Corporate information system (CIS) Is a set of information systems of individual divisions of an enterprise, united by a common workflow, such that each of the systems performs part of the decision-making management tasks, and all systems together ensure the operation of the enterprise in accordance with ISO 9000 quality standards.
Historically, there have been a number of requirements for corporate information systems. These requirements are as follows:
Consistency;
Complexity;
Modularity;
Openness;
Adaptability;
Reliability;
Security;
Scalability;
Mobility;
Ease of learning;
Support for implementation and maintenance by the developer.
Let's consider these requirements in more detail.
In modern conditions, production cannot exist and develop without a highly effective management system based on the most modern information technologies. The constantly changing market requirements, huge streams of information of a scientific, technical, technological and marketing nature require the personnel of the enterprise responsible for the strategy and tactics of the development of a high-tech enterprise to make quick and accurate decisions aimed at obtaining maximum profit at minimum costs. Optimizing costs, increasing the reactivity of production in accordance with the ever-increasing requirements of consumers in the face of tough market competition cannot be based only on speculative conclusions and intuition of even the most experienced employees. We need comprehensive control over all cost centers in the enterprise, complex mathematical methods of analysis, forecasting and planning based on taking into account a huge number of parameters and criteria and a well-coordinated system for collecting, accumulating and processing information. Extensive ways of solving this problem, associated with the exorbitant growth of the administrative apparatus, even with the best organization of its work, cannot give a positive result. The transition to modern technologies, the reorganization of production cannot bypass such a key aspect as management. And there can be only one way here - the creation of a corporate information system that meets a number of stringent requirements.
CIS, first of all, must meet the requirements of complexity and consistency. It should cover all levels of management from the corporation as a whole, taking into account branches, subsidiaries, service centers and representative offices, to the workshop, site and a specific workplace and employee. The entire production process from the point of view of informatics is a continuous process of generating, processing, changing, storing and disseminating information. Each workplace - whether it is the workplace of an assembler on an assembly line, an accountant, a manager, a storekeeper, a marketing specialist or a technologist - is a node that consumes and generates certain information. All such nodes are interconnected by flows of information embodied in the form of documents, messages, orders, actions, etc. Thus, a functioning enterprise can be represented in the form of an information-logical model, consisting of nodes and links between them. Such a model should cover all aspects of the enterprise's activities, should be logically justified and aimed at identifying mechanisms for achieving the main goal in a market environment - maximum profit, which implies the requirement of consistency. A sufficiently effective solution to this problem is possible only on the basis of strict consideration of the maximum possible justified set of parameters and the possibility of multi-criteria multivariate analysis, optimization and forecasting - that is, the complexity of the system.
Information in such a model is distributed in nature and can be rather strictly structured at each node and in each flow. Nodes and flows can be conventionally grouped into subsystems, which puts forward another important requirement for the CIS - modularity of construction. This requirement is also very important from the point of view of system implementation, since it allows parallelizing, facilitating and, accordingly, speeding up the process of installation, personnel training and launching the system into industrial operation. In addition, if the system is not created for a specific production, but is purchased on the market of ready-made systems, modularity allows you to exclude from the delivery components that do not fit into the infological model of a particular enterprise or without which you can do without at the initial stage, which allows you to save money.
Since not a single real system, even if it is created by a special order, can be exhaustively complete (the immensity cannot be grasped) and in the process of operation it may be necessary for additions, and also due to the fact that at a functioning enterprise there may be already working and proven its usefulness as a component of the CIS, the next defining requirement is openness. This requirement becomes especially important if we take into account that automation is not limited to control only, but also covers such tasks as structural design and maintenance, technological processes, internal and external workflow, communication with external information systems (for example, the Internet), security systems, etc. etc.
Any enterprise does not exist in a confined space, but in a world of constantly changing supply and demand, requiring a flexible response to the market situation, which can sometimes be associated with a significant change in the structure of the enterprise and the range of products or services provided. In addition, in the conditions of a transitional economy, legislation has an unsettled, dynamically changing nature. Large corporations, in addition, may have extraterritorial divisions located in the jurisdictional zone of other countries or free economic zones. This means that the corporate information system must have the property of adaptability, that is, flexibly adjust to different legislation, have multilingual interfaces, and be able to work with different currencies at the same time. A system that does not possess the property of adaptability is doomed to a very short existence, during which it is unlikely that it will be possible to recoup the costs of its implementation. It is desirable that, in addition to customization tools, the system also possesses development tools - tools with the help of which programmers and the most qualified users of the enterprise could independently create the components they need that would organically integrate into the system.
When the CIS is operated in an industrial mode, it becomes an indispensable component of a functioning enterprise, capable of stalling the entire production process in the event of an emergency stop and causing enormous losses. Therefore, one of the most important requirements for such a system is the reliability of its functioning, which implies the continuity of the functioning of the system as a whole, even in conditions of partial failure of its individual elements due to unforeseen and insurmountable reasons.
Security is of paramount importance to any large-scale system containing a large amount of information. The security requirement includes several aspects:
Data loss protection. This requirement is implemented mainly at the organizational, hardware and system levels. An application system such as an automated control system does not necessarily have to contain data backup and recovery facilities. These issues are addressed at the operating environment level.
Maintaining the integrity and consistency of data. The application system must track changes in interdependent documents and provide versioning and generational control of datasets.
Prevention of unauthorized access to data within the system. These tasks are solved in a comprehensive manner, both by organizational measures and at the level of operating and applied systems. In particular, application components should have advanced administration tools that allow to restrict access to data and system functionality depending on the user's status, as well as monitor user actions in the system.
Prevention of unauthorized access to data from the outside. The solution to this part of the problem falls mainly on the hardware and operational environment for the functioning of the CIS and requires a number of administrative and organizational measures.
An enterprise that is successfully operating and earning sufficient profit tends to grow, the formation of subsidiaries and branches, which in the process of operating the CIS may require an increase in the number of automated workstations, an increase in the volume of stored and processed information. In addition, for companies such as holdings and large corporations, it should be possible to use the same management technology both at the level of the parent enterprise and at the level of any, even a small, member firm. This approach puts forward a scalability requirement.
At a certain stage in the development of an enterprise, the growth of requirements for performance and system resources may require a transition to a more productive software and hardware platform. In order for such a transition not to entail a radical breakdown of the management process and unjustified investment in the acquisition of more powerful application components, it is necessary to fulfill the requirement of mobility.
Ease of study is a requirement that includes not only the presence of an intuitive program interface, but also the availability of detailed and well-structured documentation, the possibility of training personnel in specialized courses and internships for responsible specialists at related enterprises where this system is already in use.
Developer support. This concept includes a number of opportunities, such as obtaining new software versions for free or with a substantial discount, obtaining additional methodological literature, hotline consultations, obtaining information about other software products of the developer, the opportunity to participate in seminars, scientific and practical conferences users and other activities by the developer or user groups, etc. Naturally, only a serious company that is stable in the market of software products and has a fairly clear perspective for the future is capable of providing such support to the user.
Escort. During the operation of complex software and hardware complexes, situations may arise that require prompt intervention by qualified personnel of the developer company or its representative on the spot. The support includes a visit of a specialist to the customer's site to eliminate the consequences of emergencies, technical training at the customer's site, methodological and practical assistance, if necessary, to make changes to the system that are not in the nature of a radical restructuring or new development. It also implies the installation of new software releases obtained from the developer free of charge by the support organization authorized by the developer or by the developer himself.
Summary: EIS must meet the requirements:
Complexity and consistency;
Modularity;
Openness;
Reliability;
Security;
Scalability;
Mobility;
Ease of learning;
Support from the developer;
Accompaniment by the developer or his representative.
In turn, the applied system, which is the ACS, puts forward a number of requirements for the environment in which it operates. The environment for the functioning of the application system is a network operating system, operating systems on workstations, a database management system and a number of auxiliary subsystems that provide security functions, archiving, etc. Typically, a list of these requirements and instructions for a specific set of system software are contained in the documentation for a specific application system.
Introduction. From the history of network technologies. 3
The concept of "Corporate networks". Their main functions. 7
Technologies used to create corporate networks. fourteen
The structure of the corporate network. Hardware. 17
Methodology for creating a corporate network. 24
Conclusion. 33
List of used literature. 34
Introduction.
From the history of network technologies.
The history and terminology of corporate networks is closely related to the history of the birth of the Internet and the World Wide Web. Therefore, it does not hurt to remember how the very first network technologies appeared, which led to the creation of modern corporate (departmental), territorial and global networks.
The Internet began in the 60s as a US Department of Defense project. The increased role of the computer has given rise to the need for both the separation of information between different buildings and local networks, and the maintenance of the overall performance of the system in the event of failure of individual components. The Internet is based on a set of protocols that allow WANs to send and transmit information to each other independently; if one node of the network is unavailable for some reason, the information reaches its final destination through other nodes that are currently operational. The protocol developed for this purpose is called the Internetworking Protocol (IP). (The acronym TCP / IP stands for the same.)
Since then, the IP protocol has become generally accepted in the military as a way to make information publicly available. Since many of these agencies' projects were carried out in various research groups at universities around the country, and the way information was exchanged between heterogeneous networks proved to be very effective, the application of this protocol quickly spread outside the military departments. It began to be used both in NATO research institutes and in European universities. Today, the IP protocol, and therefore the Internet, is the universal global standard.
In the late 1980s, the Internet faced a new challenge. At first, the information was either emails or simple data files. For their transmission, appropriate protocols were developed. Now a whole series of files of a new type have emerged, usually united under the name multimedia, containing both images and sounds, and hyperlinks that allow users to navigate both within one document and between different documents containing information related to each other.
In 1989, the Laboratory of Elementary Particle Physics of the European Center for Nuclear Research (CERN) successfully launched a new project, the purpose of which was to create a standard for the transmission of this kind of information over the Internet. The main components of this standard were the multimedia file formats, hypertext files, and the protocol for receiving such files over the network. The file format was named HyperText Markup Language (HTML). It was a simplified version of the more general Standard General Markup Language (SGML). The request service protocol is called HyperText Transfer Protocol (HTTP). In general, it looks like this: the server running the program serving the HTTP protocol (HTTP demon) sends HTML files at the request of Internet clients. These two standards formed the basis for a fundamentally new type of access to computer information. Standard multimedia files can now not only be retrieved at the user's request, but also exist and be displayed as part of another document. Since the file contains hyperlinks to other documents that may be located on other computers, the user can access this information with a light click of the mouse button. This fundamentally removes the complexity of accessing information in a distributed system. Multimedia files in this technology are traditionally called pages. A page is also called information that is sent to the client machine in response to each request. The reason for this is that a document usually consists of many separate parts linked by hyperlinks. This division allows the user to decide for himself which parts he wants to see in front of him, saves him time and reduces network traffic. A software product that is used directly by a user is usually called a browser (from the word browse - to graze) or a navigator. Most of them allow you to automatically get and display a specific page that contains links to documents that the user accesses most often. This page is called the home page and is usually accessed by a separate button. Each non-trivial document is usually provided with a special page, similar to the "Contents" section in a book. This is where the study of the document usually begins, which is why it is also often called the home page. Therefore, in general, a home page is understood as a certain index, an entry point into information of a certain kind. Usually the name itself includes a definition of this section, for example, Microsoft Home Page. On the other hand, each document can be accessed from many other documents. The entire space of referencing documents on the Internet has been called the World Wide Web (the world wide web is an acronym for WWW or W3). The document system is completely distributed, and the author does not even have the ability to trace all the links to his document that exist on the Internet. The server providing access to these pages can register all those who read such a document, but not those who link to it. The situation is the opposite of that existing in the world of printed materials. Many research areas have periodically published indexes of articles on a topic, but it is impossible to trace everyone who reads a given document. Here we know those who read (had access) to the document, but do not know who referred to it. Another interesting feature is that with this technology it becomes impossible to keep track of all the information available through the WWW. Information appears and disappears continuously, in the absence of any central control. However, this should not be intimidated, the same is happening in the world of printed materials. We do not try to accumulate old newspapers if we have fresh ones every day, and the effort is negligible.
Client software products that receive and display HTML files are called browsers. The first graphical browser was called Mosaic and was made at the University of Illinois. Many of the modern browsers are based on this product. However, due to the standardization of protocols and formats, any compatible software product can be used. Viewers exist on most major client systems capable of supporting smart windows. These include MS / Windows, Macintosh, X-Window systems, and OS / 2. There are also viewing systems for those operating systems where windows are not used - they display text fragments of documents that are being accessed on the screen.
The presence of viewers on such heterogeneous platforms is essential. The operating environments on the author's machine, server, and client are independent of each other. Any client can access and view documents created using HTML and related standards, and transmitted through an HTTP server, regardless of the operating environment in which they were created or where they came from. HTML also supports form design and feedback functions. This means that the user interface, both when querying and retrieving data, allows you to go beyond point and click.
Many stations, including Amdahl, have written interfaces for interaction between HTML forms and legacy applications, creating a universal client user interface for the latter. This makes it possible to write client-server applications without worrying about client-level coding. In fact, there are already programs in which the client is viewed as a viewer. An example is Oracle Corporation's WOW interface, which replaces Oracle Forms and Oracle Reports. Although this technology is still very young, it can already change the situation in the field of information management as much as the use of semiconductors and microprocessors in their time changed the world of computers. It allows us to turn functions into separate modules and simplify applications, taking us to a new level of integration that is more in line with the business functions of the enterprise.
Information overload is the curse of our time. The technologies that were created to alleviate this problem have only made it worse. This is not surprising: it is worth looking at the contents of the trash cans (regular or electronic) of an ordinary employee dealing with information. Even aside from the inevitable heap of advertising "junk" in the mail, most of the information is sent to such an employee just "in case" he needs it. Add to this the "out of date" information, which is likely to be needed, but later - and here's the main contents of the trash can. The employee will most likely store half of the information that "may be needed" and all the information that is likely to be needed in the future. When the need arises, he will have to deal with a cumbersome, poorly structured archive of personal information, and at this stage additional difficulties may arise due to the fact that it is stored in files of different formats on different media. The advent of the copier has made the situation of "suddenly needed" information even worse. The number of copies, instead of decreasing, only increases. Email only made the problem worse. Today the "publisher" of information can create his own, personal mailing list and with one command send an almost unlimited number of copies "in case" they may be needed. Some of these distributors of information understand that their lists are worthless, but instead of fixing them, they put a note at the beginning of the message with a note similar to the following: "If you are not interested ..., destroy this message." The letter will still clog the mailbox, and the addressee, in any case, will have to spend time getting acquainted with it and destroying it. The exact opposite of "might be useful" information is "timely" information, or information that is in demand. They expected help from computers and networks in working with this particular type of information, but so far they have not been able to cope with it. There used to be two main methods of delivering timely information.
When using the first of them, information was distributed between applications and systems. To access it, the user had to study and then constantly perform many complex access procedures. When access was obtained, each application required its own interface. When faced with such difficulties, users usually simply refused to receive timely information. They were able to master access to one or two applications, but they were not enough for the rest.
To solve this problem, some enterprises tried to accumulate all the distributed information on one main system. As a result, the user received a single access method and a single interface. However, since in this case all the requests of the enterprise were processed centrally, these systems grew and became more complex. More than ten years have passed, and many of them are still not filled with information due to the high cost of entering and maintaining it. There were other problems here as well. The complexity of such unified systems made them difficult to modify and use. To support the discrete data of transaction processes, tools have been developed to manage such systems. Over the past decade, the data we deal with has become much more complex, making it difficult to maintain information. The changing nature of information needs, and how difficult it is to change, has given rise to these large, centrally managed systems that are holding back requests at the enterprise level.
Web technology offers a new approach to delivering information on demand. Because it supports authorization, publication and management of distributed information, the new technology does not add to the complexity of the old centralized systems. Documents are written, maintained, and published directly by authors without having to ask programmers to create new data entry forms and reporting programs. With the new viewing systems, the user can access and view information from distributed sources and systems using a simple, unified interface, without having the slightest idea of the servers they are actually accessing. These simple technological changes will revolutionize information infrastructures and fundamentally change the way our organizations operate.
The main distinguishing feature of this technology is that the control of the information flow is in the hands not of its creator, but of the consumer. If the user has the ability to easily receive and view information as needed, it will no longer have to be sent to him "in case" if it is needed. The publishing process can now be independent of the automatic dissemination of information. This includes forms, reports, standards, meeting scheduling, sales support tools, training materials, schedules, and a host of other documents that tend to clog our trash cans. For the system to work, as mentioned above, you need not only a new information infrastructure, but also a new approach, a new culture. As creators of information, we must learn to publish it without distributing it, as users - to be more responsible in identifying and tracking their information requests, actively and effectively receiving information when we need it.
The concept of "Corporate networks". Their main functions.
Before talking about private (corporate) networks, you need to define what these words mean. Recently, this phrase has become so widespread and fashionable that it began to lose its meaning. In our understanding, a corporate network is a system that provides information transfer between various applications used in a corporation's system. Based on this completely abstract definition, we will consider various approaches to creating such systems and will try to fill the concept of a corporate network with concrete content. At the same time, we believe that the network should be as universal as possible, that is, allow the integration of existing and future applications with the lowest possible costs and restrictions.
A corporate network, as a rule, is geographically distributed, i.e. uniting offices, divisions and other structures located at a considerable distance from each other. Often, corporate network nodes are located in different cities and sometimes countries. The principles by which such a network is built are quite different from those used to create a local network, even covering several buildings. The main difference is that geographically distributed networks use rather slow (today - tens and hundreds of kilobits per second, sometimes up to 2 Mbit / s) leased communication lines. If, when creating a local network, the main costs are spent on the purchase of equipment and laying cables, then in wide-area networks the most significant cost element is the rent for the use of channels, which grows rapidly with an increase in the quality and speed of data transmission. This limitation is fundamental, and when designing a corporate network, all measures should be taken to minimize the amount of data transferred. For the rest, the corporate network should not impose restrictions on which applications and how they process the information carried over it.
By applications, we mean here both system software - databases, mail systems, computing resources, file service, etc. - and the means with which the end user works. The main tasks of a corporate network are the interaction of system applications located in various nodes, and access to them by remote users.
The first problem that has to be solved when creating a corporate network is the organization of communication channels. If within one city it is possible to count on leasing dedicated lines, including high-speed ones, then when moving to geographically distant nodes, the cost of leasing channels becomes simply astronomical, and their quality and reliability are often very low. The natural solution to this problem is to use existing global networks. In this case, it is sufficient to provide channels from offices to the nearest network nodes. The global network will take over the task of delivering information between nodes. Even when creating a small network within the same city, one should keep in mind the possibility of further expansion and use technologies that are compatible with existing global networks.
Often the first, if not the only, such network that comes to mind is the Internet. Using the Internet in corporate networks Depending on the tasks being solved, the Internet can be considered at different levels. For the end user, it is primarily a worldwide system for the provision of information and postal services. The combination of new technologies for access to information, united by the concept of the World Wide Web, with the cheap and generally accessible global computer communication system, the Internet, has actually spawned a new mass media, which is often referred to simply as the Net. Anyone who connects to this system perceives it simply as a mechanism that gives access to certain services. The implementation of this mechanism turns out to be absolutely insignificant.
When using the Internet as the basis for a corporate data network, a very interesting thing emerges. It turns out that the Network is not a network. This is precisely the Internet - the interconnection. If we look inside the Internet, we will see that information flows through many completely independent and mostly non-profit nodes, connected through the most diverse channels and data networks. The rapid growth of services provided on the Internet leads to overloading of nodes and communication channels, which sharply reduces the speed and reliability of information transmission. At the same time, Internet service providers do not bear any responsibility for the functioning of the network as a whole, and communication channels are developing extremely unevenly and mainly where the state considers it necessary to invest in this. Accordingly, there is no guarantee of the quality of the network, the speed of data transfer, or even the simple reachability of your computers. For tasks in which reliability and guaranteed delivery time of information are critical, the Internet is far from the best solution. In addition, the Internet binds users to a single protocol - IP. This is good when we use standard applications that work with this protocol. The use of any other systems with the Internet is not easy and expensive. If you need to provide mobile users with access to your private network, the Internet is also not the best solution.
It would seem that there should be no big problems here - Internet service providers are almost everywhere, take a laptop with a modem, call and work. However, a supplier, say, in Novosibirsk, has no obligation to you if you are connected to the Internet in Moscow. He does not receive money for services from you and, naturally, will not provide access to the network. Either you have to conclude an appropriate contract with him, which is hardly reasonable if you are on a two-day business trip, or call from Novosibirsk to Moscow.
Another Internet issue that has been widely discussed in recent years is security. If we are talking about a private network, it seems quite natural to protect the transmitted information from prying eyes. The unpredictability of information paths between many independent Internet sites not only increases the risk that some overly curious network operator could put your data on disk (technically, it is not that difficult), but also makes it impossible to determine the location of the information leak. Encryption tools only partially solve the problem, since they are mainly applicable to mail, file transfers, etc. Solutions that allow encrypting information in real time with an acceptable speed (for example, when working directly with a remote database or file server) are inaccessible and expensive. Another aspect of the security problem is again related to the decentralization of the Internet - there is no one who can restrict access to the resources of your private network. Since this is an open system where everyone can see everyone, anyone can try to get into your office network and gain access to data or programs. There are, of course, means of protection (for them, the name Firewall is adopted - in Russian, more precisely in German "firewall" means a fire wall). However, they should not be considered a panacea - think about viruses and antivirus programs. Any protection can be broken, as long as it pays for the cost of hacking. It should also be noted that you can make a system connected to the Internet inoperative without intruding on your network. There are known cases of unauthorized access to the management of network nodes, or simply using the features of the Internet architecture to disrupt access to a particular server. Thus, the Internet cannot be recommended as the basis for systems that require reliability and closedness. Connecting to the Internet within a corporate network makes sense if you need access to that vast information space, which is actually called the Network.
A corporate network is a complex system that includes thousands of various components: computers of different types, from desktop to mainframe, system and application software, network adapters, hubs, switches and routers, cabling. The main task of system integrators and administrators is to ensure that this cumbersome and very expensive system copes as best as possible with the processing of information flows circulating between the employees of the enterprise and allows them to make timely and rational decisions that ensure the survival of the enterprise in fierce competition. And since life does not stand still, the content of corporate information, the intensity of its flows and the methods of its processing are constantly changing. The latest example of a sharp change in the technology of automated processing of corporate information in plain sight - it is associated with the unprecedented growth in popularity of the Internet in the last 2-3 years. The changes brought about by the Internet are multifaceted. The WWW hypertext service has changed the way information is presented to a person, collecting all its popular types on its pages - text, graphics and sound. Internet transport - inexpensive and accessible to almost all enterprises (and through telephone networks and single users) - greatly facilitated the task of building a territorial corporate network, while simultaneously highlighting the task of protecting corporate data when it is transmitted through a highly publicly accessible public network with a multi-million population ".
Technologies used in corporate networks.
Before setting out the basics of the methodology for building corporate networks, it is necessary to give a comparative analysis of technologies that can be used in corporate networks.
Modern data transmission technologies can be classified according to data transmission methods. In general, there are three main methods of data transmission:
channel switching;
switching messages;
packet switching.
All other methods of interaction are, as it were, their evolutionary development. For example, if we represent data transmission technologies in the form of a tree, then the packet switching branch will be divided into frame switching and cell switching. Recall that packet switching technology was developed over 30 years ago to reduce overhead and improve the performance of existing data transmission systems. The first packet switching technologies, X.25 and IP, were designed with poor quality communication channels in mind. With the improvement in quality, it became possible to use a protocol such as HDLC to transfer information, which has found its place in Frame Relay networks. The desire to achieve greater performance and technical flexibility was the impetus for the development of SMDS technology, the possibilities of which were then extended by the standardization of ATM. One of the parameters by which one can compare technologies is the guarantee of information delivery. Thus, X.25 and ATM technologies guarantee reliable delivery of packets (the latter using the SSCOP protocol), while Frame Relay and SMDS operate in a mode where delivery is not guaranteed. Further, the technology can ensure that the data arrives at the recipient in the sequence it was sent. Otherwise, the order must be restored on the receiving side. Packet-switched networks can be pre-connection oriented or simply transfer data to the network. In the first case, both permanent and dial-up virtual connections can be supported. Other important parameters are the availability of data flow control mechanisms, traffic management systems, congestion detection and prevention mechanisms, etc.
Technology comparisons can also be made based on criteria such as the effectiveness of the addressing scheme or routing methods. For example, the addressing used may be geo-location (dial-up), WAN, or hardware oriented. For example, IP uses a 32-bit logical address that is assigned to networks and subnets. The E.164 addressing scheme is an example of a geographic location-based addressing scheme, and the MAC address is an example of a hardware address. X.25 technology uses a Logical Channel Number (LCN), and the virtual switched connection in this technology uses the X.121 addressing scheme. In Frame Relay technology, multiple VCs can be embedded in one channel, with a single VC identified by a Data-Link Connection Identifier (DLCI). This identifier is indicated in each transmitted frame. DLCI has local meaning only; in other words, the sender's virtual channel can be identified by one number, while the recipient's can be identified by a completely different one. Virtual dial-up connections in this technology are based on the E.164 numbering scheme. ATM cell headers contain unique VCI / VPI identifiers that change as the cells pass through intermediate switching systems. ATM switched virtual connections can use E.164 or AESA addressing schemes.
Routing of packets on a network can be done statically or dynamically, and be either a standardized mechanism for a particular technology, or act as a technical basis. Examples of standardized solutions include dynamic routing protocols OSPF or RIP for IP. In relation to ATM technology, the ATM Forum has defined the PNNI switched virtual connection request routing protocol, the distinctive feature of which is the accounting of quality of service information.
The ideal option for a private network would be to create communication channels only in those areas where it is necessary, and transfer over them any network protocols that are required by running applications. At first glance, this is a return to leased communication lines, but there are technologies for building data transmission networks that allow organizing channels inside them that arise only at the right time and in the right place. Such channels are called virtual. A system that combines remote resources using virtual channels can naturally be called a virtual network. Today, there are two main technologies for virtual networks - circuit-switched networks and packet-switched networks. The former include the conventional telephone network, ISDN and a number of other, more exotic technologies. Packet-switched networks are represented by X.25 technologies, Frame Relay and, more recently, ATM. It is too early to talk about the use of ATM in wide area networks. The rest of the types of virtual (in various combinations) networks are widely used in the construction of corporate information systems.
Circuit-switched networks provide a subscriber with several communication channels with a fixed bandwidth per connection. The well-known telephone network provides one communication channel between subscribers. If you need to increase the number of simultaneously available resources, you have to install additional phone numbers, which is very expensive. Even if we forget about the low quality of communication, the limitation on the number of channels and the long connection establishment time do not allow the use of telephone communication as the basis of a corporate network. For connecting individual remote users, this is a fairly convenient and often the only method available.
Another example of a circuit-switched virtual network is ISDN (Integrated Services Digital Network). ISDN provides digital channels (64 kbps) that can carry both voice and data. A Basic Rate Interface (ISDN) connection includes two of these channels and an additional 16 kbps control channel (this combination is referred to as 2B + D). It is possible to use a larger number of channels - up to thirty (Primary Rate Interface, 30B + D), but this leads to a corresponding increase in the cost of equipment and communication channels. In addition, the cost of renting and using the network proportionally increases. In general, the restrictions on the number of simultaneously available resources imposed by ISDN lead to the fact that this type of communication turns out to be convenient to use mainly as an alternative to telephone networks. In systems with a small number of nodes, ISDN can also be used as the main network protocol. It should only be borne in mind that access to ISDN in our country is the exception rather than the rule.
An alternative to circuit-switched networks is packet-switched networks. When using packet switching, one communication channel is used in a time-sharing mode by many users - in much the same way as in the Internet. However, unlike networks like the Internet, where each packet is routed separately, packet-switched networks require establishing a connection between end resources before transmitting information. After establishing a connection, the network "remembers" the route (virtual channel) through which information should be transmitted between subscribers and remembers it until it receives a signal that the connection is broken. For applications operating in a packet switching network, virtual circuits look like ordinary communication lines - with the only difference that their throughput and introduced delays vary depending on the network congestion.
The classic packet switching technology is the X.25 protocol. Now it is customary to wrinkle your nose at these words and say: "it is expensive, slow, outdated and not fashionable." Indeed, there are virtually no X.25 networks today that use speeds above 128 kbps. The X.25 protocol includes powerful error correction tools to ensure reliable delivery of information even on bad links and is widely used where quality communication channels are not available. In our country, they are not almost everywhere. Naturally, reliability comes at a price — in this case, the speed of the network equipment and the relatively large — but predictable — delays in the dissemination of information. At the same time, X.25 is a universal protocol that allows you to transfer almost any type of data. It is "natural" for X.25 networks to run applications that use the OSI protocol stack. These include systems using the X.400 (e-mail) and FTAM (file exchange) standards, as well as a few others. Tools are available to implement OSI-based interaction between Unix systems. Another standard X.25 networking capability is communication over common asynchronous COM ports. Figuratively speaking, an X.25 network lengthens the cable connected to a serial port, bringing its connector to remote resources. Thus, virtually any application that can be accessed through a COM port can be easily integrated into an X.25 network. As examples of such applications, we should mention not only terminal access to remote host computers, for example, Unix machines, but also the interaction of Unix computers with each other (cu, uucp), systems based on Lotus Notes, e-mail cc: Mail and MS Mail, etc. For LAN interconnection in nodes connected to the X.25 network, there are methods of packing ("encapsulating") information packets from the local network into X.25 packets. Some of the service information is not transmitted in this case, since it can be unambiguously restored on the recipient's side. The standard encapsulation mechanism is the one described in RFC 1356. It allows different LAN protocols (IP, IPX, etc.) to be transmitted simultaneously over a single virtual connection. This mechanism (or an older IP-only implementation of RFC 877) is implemented in almost all modern routers. There are also transmission methods for X.25 and other communication protocols, in particular SNA, which is used in the IBM mainframe networks, and a number of proprietary protocols from various manufacturers. Thus, X.25 networks offer a universal transport mechanism for transferring information between virtually any application. In this case, different types of traffic are transmitted over the same communication channel, "not knowing" anything about each other. With X.25 LAN bonding, you can isolate individual pieces of the corporate network from each other, even if they share the same communication lines. This facilitates the solution of security and access control problems that inevitably arise in complex information structures. In addition, in many cases there is no need to use complex routing mechanisms, leaving this task to the X.25 network. Today, there are dozens of public X.25 global networks in the world, their nodes are located in almost all major business, industrial and administrative centers. In Russia, X.25 services are offered by Sprint Network, Infotel, Rospak, Rosnet, Sovam Teleport and a number of other providers. In addition to connecting remote sites, X.25 networks always provide means of access for end users. In order to connect to any resource on the X.25 network, the user only needs to have a computer with an asynchronous serial port and a modem. At the same time, there are no problems with authorizing access to geographically remote nodes - firstly, X.25 networks are sufficiently centralized and by concluding an agreement, for example, with Sprint Network or its partner, you can use the services of any of the Sprintnet nodes - and these are thousands of cities around the world, including more than a hundred in the territory of the former USSR. Secondly, there is a protocol of interaction between different networks (X.75), which also takes into account payment issues. Thus, if your resource is connected to an X.25 network, you can access it both from your provider's nodes and through nodes on other networks - that is, from virtually anywhere in the world. From a security perspective, X.25 networks offer some very attractive capabilities. First of all, due to the very structure of the network, the cost of intercepting information in an X.25 network is high enough to already serve as a good defense. The problem of unauthorized access can also be solved quite effectively by means of the network itself. If any - however small - the risk of information leakage turns out to be unacceptable, then, of course, it is necessary to use encryption tools, including in real time. Today there are encryption tools designed specifically for X. 25 and allowing you to work at fairly high speeds - up to 64 kbps. Such equipment is manufactured by Racal, Cylink, Siemens. There are also domestic developments created under the auspices of the FAPSI. The disadvantage of X.25 technology is that it has a number of fundamental speed limits. The first of them is associated precisely with the developed capabilities of correction and recovery. These tools cause delays in the transmission of information and require a lot of processing power and performance from the X.25 equipment, as a result of which it simply "cannot keep up" with fast communication lines. Although there is equipment that has two megabit ports, the actual speed provided by it does not exceed 250 - 300 kbps per port. On the other hand, for modern high-speed communication lines, X.25 correction means are redundant and when they are used, the equipment power is often idle. The second feature that makes X.25 networks look like slow is the encapsulation of the LAN protocols (primarily IP and IPX). All other things being equal, the connection of local networks over X.25 is, depending on the parameters of the network, 15-40 percent slower than when using HDLC over a dedicated line. Moreover, the worse the communication line, the higher the loss of productivity. Again, we are dealing with an obvious redundancy: LAN protocols have their own means of correction and recovery (TCP, SPX), but when using X.25 networks, you have to do it again, losing speed.
It is on these grounds that X.25 networks are declared slow and obsolete. But before talking about the fact that any technology is outdated, it should be indicated for what applications and in what conditions. On low quality links, X.25 networks are quite efficient and offer significant cost and performance gains over leased lines. On the other hand, even if you can count on the rapid improvement in the quality of communication - a prerequisite for the obsolescence of X.25 - then the investment in X.25 equipment will not be lost, since modern equipment includes the possibility of moving to Frame Relay technology.
Frame Relay networks
Frame Relay technology emerged as a means to realize the benefits of packet switching on high-speed communication lines. The main difference between Frame Relay and X.25 networks is that they eliminate error correction between network nodes. The tasks of restoring the information flow are assigned to the terminal equipment and user software. Naturally, this requires the use of sufficiently high-quality communication channels. It is believed that for successful work with Frame Relay, the probability of an error in the channel should be no worse than 10-6 - 10-7, i.e. no more than one bad bit per several million. The quality provided by conventional analog lines is usually one to three orders of magnitude lower. The second difference between Frame Relay networks is that today almost all of them implement only the mechanism of permanent virtual connections (PVC). This means that when connecting to a Frame Relay port, you must determine in advance which remote resources you will have access to. The principle of packet switching - many independent virtual connections in one communication channel - remains here, but you cannot choose the address of any network subscriber. All resources available to you are determined when you configure the port. Thus, on the basis of Frame Relay technology, it is convenient to build closed virtual networks used to transfer other protocols by means of which routing is carried out. A "closed" virtual network means that it is completely inaccessible to other users on the same Frame Relay network. For example, in the United States, Frame Relay networks are widely used as the backbone for the Internet. However, your private network can use Frame Relay VCs on the same lines as Inernet traffic - and be completely isolated from it. Like X.25 networks, Frame Relay provides a universal transmission medium for almost any application. The main area of application for Frame Relay today is the interconnection of remote LANs. In this case, error correction and information recovery are performed at the level of LAN transport protocols - TCP, SPX, etc. Losses for encapsulation of LAN traffic in Frame Relay do not exceed two to three percent. Frame Relay LAN encapsulation is described in RFC 1294 and RFC 1490. RFC 1490 also defines Frame Relay for SNA traffic. The ANSI T1.617 Annex G specification describes the use of X.25 over Frame Relay networks. This uses all the addressing, correction and recovery functions X. 25 - but only between end nodes that implement Annex G. A persistent connection over a Frame Relay network in this case looks like a "straight wire" that carries X.25 traffic. The X.25 parameters (packet and window sizes) can be selected to achieve the lowest possible propagation delays and speed loss when encapsulating LAN protocols. The lack of error correction and complex packet switching mechanisms typical for X.25 allows information to be transmitted over Frame Relay with minimal delays. Additionally, it is possible to enable a prioritization mechanism that allows the user to have a guaranteed minimum information transfer rate for a virtual channel. This capability allows Frame Relay to be used to carry delay-critical information such as real-time voice and video. This relatively new feature is gaining in popularity and is often the primary consideration in choosing Frame Relay as the backbone of the corporate network. It should be remembered that today Frame Relay services are available in our country in no more than one and a half dozen cities, while X.25 is available in about two hundred. There is every reason to believe that as communication channels evolve, Frame Relay technology will become more widespread - primarily where X.25 networks exist today. Unfortunately, there is no single standard describing how different Frame Relay networks interact, so users are bound to a single service provider. If it is necessary to expand the geography, it is possible to connect at one point to the networks of different providers - with a corresponding increase in costs. There are also private Frame Relay networks that operate within a single city or use long-distance - usually satellite - leased lines. Building private networks based on Frame Relay allows you to reduce the number of leased lines and integrate voice and data transmission.
The structure of the corporate network. Hardware.
When building a geographically distributed network, all the technologies described above can be used. To connect remote users, the simplest and most affordable option is to use a telephone connection. ISDN networks can be used where possible. To connect the nodes of the network, in most cases, global data transmission networks are used. Even where it is possible to lay dedicated lines (for example, within the same city), the use of packet switching technologies allows you to reduce the number of required communication channels and - which is important - to ensure the compatibility of the system with existing global networks. Connecting a corporate network to the Internet is justified if you need access to the appropriate services. It is worth using the Internet as a data transmission medium only when other methods are unavailable and financial considerations outweigh the requirements of reliability and security. If you will only be using the Internet as a source of information, it is best to use dial-on-demand technology. in such a way of connection, when the connection to the Internet site is established only on your initiative and at the time you need. This dramatically reduces the risk of unauthorized access to your network from the outside. The easiest way to provide such a connection is to use dial-up to the Internet site over a telephone line or, if possible, over ISDN. Another, more reliable way to provide on-demand connectivity is to use a leased line and X.25 protocol, or - much more preferable - Frame Relay. In this case, the router on your end must be configured to disconnect the virtual connection if there is no data for a certain time and re-establish it only when data appears on your end. Widespread connection methods using PPP or HDLC do not provide this opportunity. If you want to provide your information on the Internet - for example, set up a WWW or FTP server, the connection on demand is not applicable. In this case, you should not only use access restriction using Firewall, but also isolate the Internet server from other resources as much as possible. A good solution is to use a single Internet connection point for the entire wide area network, the nodes of which are connected to each other using X.25 or Frame Relay virtual circuits. In this case, access from the Internet is possible to a single site, while users at other sites can access the Internet using a connection on demand.
To transfer data within the corporate network, it is also worth using virtual circuits of packet-switched networks. The main advantages of this approach - versatility, flexibility, security - were discussed in detail above. Both X.25 and Frame Relay can be used as a virtual network when building a corporate information system. The choice between them is determined by the quality of communication channels, the availability of services at the connection points and - not least - financial considerations. Today, the cost of using Frame Relay for long distance communications is several times higher than for X.25 networks. On the other hand, higher data rates and the ability to simultaneously transmit data and voice can be decisive arguments in favor of Frame Relay. On those parts of the corporate network where leased lines are available, Frame Relay technology is more preferable. In this case, it is possible both to interconnect local networks and connect to the Internet, as well as to use those applications that traditionally require X.25. In addition, telephone communication between the nodes is possible over the same network. For Frame Relay, it is better to use digital communication channels, however, even on physical lines or voice frequency channels, you can create a completely effective network by installing the appropriate channel equipment. Good results are obtained by using Motorola 326x SDC modems, which have unique capabilities for data correction and compression in synchronous mode. Thanks to this, it is possible - at the cost of introducing small delays - to significantly increase the quality of the communication channel and achieve an effective speed of up to 80 kbps and higher. Short-range modems can also be used on physical lines of short length, providing sufficiently high speeds. However, high quality of the line is required here, since short-range modems do not support any error correction. RAD short-range modems are widely known, as well as PairGain equipment, which allows achieving a speed of 2 Mbit / s on physical lines about 10 km long. To connect remote users to the corporate network, access nodes of X.25 networks can be used, as well as their own communication nodes. In the latter case, the allocation of the required number of telephone numbers (or ISDN channels) is required, which can be too expensive. If you need to ensure the connection of a large number of users at the same time, then using the access nodes of the X network may be a cheaper option. 25, even within the same city.
A corporate network is a rather complex structure that uses various types of communication, communication protocols and methods of connecting resources. From the point of view of the convenience of construction and manageability of the network, one should focus on the same type of equipment from one manufacturer. However, practice shows that there are no suppliers offering the most effective solutions for all emerging problems. A working network is always the result of a compromise - either it is a homogeneous system that is not optimal in terms of price and capabilities, or a combination of products from different manufacturers is more difficult to install and manage. Next, we will look at networking tools from several leading manufacturers and give some recommendations for their use.
All equipment of data transmission networks can be conditionally divided into two large classes -
1.peripheral, which is used to connect end nodes to the network, and
2. backbone or backbone, which implements the basic functions of the network (circuit switching, routing, etc.).
There is no clear boundary between these types - the same devices can be used in different capacities or combine both functions. It should be noted that high requirements are usually imposed on backbone equipment in terms of reliability, performance, number of ports, and further expandability.
Peripheral equipment is a necessary component of any corporate network. The functions of backbone nodes can be assumed by the global data transmission network, to which resources are connected. As a rule, backbone nodes as part of a corporate network appear only in those cases when leased communication channels are used or their own access nodes are created. Peripheral equipment of corporate networks in terms of their functions can also be divided into two classes.
First, these are routers that serve to connect homogeneous LANs (usually IP or IPX) over wide area data networks. In networks that use IP or IPX as the main protocol - in particular, in the same Internet - routers are also used as backbone equipment that provides docking of various communication channels and protocols. Routers can be made both as stand-alone devices and software based on computers and special communication adapters.
The second widely used type of peripheral equipment is gateways), which implement the interaction of applications running on different types of networks. Enterprise networks primarily use OSI gateways, which provide LAN interoperability with X.25 resources, and SNA gateways, which provide connectivity to IBM networks. A fully functional gateway is always a hardware and software complex, since it must provide the software interfaces necessary for applications. Routers Cisco Systems Among the routers, the most well-known products are Cisco Systems, which implement a wide range of tools and protocols used in the interaction of local area networks. Cisco equipment supports a variety of connection methods, including X.25, Frame Relay and ISDN, allowing you to create fairly complex systems. In addition, among the Cisco family of routers, there are excellent servers for remote access to local networks, and in some configurations, gateway functions are partially implemented (what in Cisco terms is called Protocol Translation).
The main area of application for Cisco routers is complex networks using IP or, less often, IPX as the main protocol. In particular, Cisco equipment is widely used in Internet backbones. If your corporate network is primarily intended for interconnecting remote LANs and requires complex IP or IPX routing over heterogeneous communication channels and data networks, then using Cisco equipment is most likely the best choice. The means of working with Frame Relay and X.25 are implemented in Cisco routers only to the extent necessary for interconnecting local networks and accessing them. If you want to build your system on the basis of packet-switched networks, then Cisco routers can work in it only as purely peripheral equipment, and many of the routing functions are redundant, and the price, accordingly, is too high. The most interesting for use in corporate networks are the access servers Cisco 2509, Cisco 2511 and the new Cisco 2520 series devices. Their main area of application is access of remote users to local networks via telephone lines or ISDN with dynamic assignment of IP addresses (DHCP). Motorola ISG Equipment Among the equipment designed to work with X.25 and Frame Relay, the most interesting products are produced by the Motorola Information Systems Group (Motorola ISG). Unlike backbone devices used in global data transmission networks (Northern Telecom, Sprint, Alcatel, etc.), Motorola equipment is capable of operating completely autonomously, without a special network control center. The range of capabilities important for use in corporate networks is much wider for Motorola equipment. Of particular note is the advanced hardware and software upgrades that make it easy to adapt the equipment to specific conditions. All Motorola ISG products can operate as X.25 / Frame Relay switches, multi-protocol access devices (PAD, FRAD, SLIP, PPP, etc.), support Annex G (X.25 over Frame Relay), provide SNA protocol conversion (SDLC / QLLC / RFC1490). Motorola ISG equipment can be divided into three groups, differing in the set of hardware and field of application.
The first group designed to work as peripheral devices is the Vanguard series. It includes the Vanguard 100 (2-3 ports) and Vanguard 200 (6 ports) serial access nodes, as well as the Vanguard 300/305 routers (1-3 serial ports and an Ethetrnet / Token Ring port) and Vanguard 310 ISDN routers. Vanguard, in addition to a set of communication capabilities, includes the transfer of IP, IPX and Appletalk protocols over X.25, Frame Relay and PPP. Naturally, at the same time, the gentleman's set necessary for any modern router is supported - RIP and OSPF protocols, means of filtering and restricting access, data compression, etc.
The next group of Motorola ISG products includes the Multimedia Peripheral Router (MPRouter) 6520 and 6560, which differ mainly in performance and expandability. In the basic configuration, the 6520 and 6560 have, respectively, five and three serial ports and an Ethernet port, and the 6560 has all the high-speed ports (up to 2 Mbps), and the 6520 has three ports up to 80 kbps. MPRouter supports all communication protocols and routing capabilities available for Motorola ISG products. The main feature of MPRouter is the ability to install a variety of additional cards, which is reflected in the word Multimedia in its name. There are serial port cards, Ethernet / Token Ring ports, ISDN cards, Ethernet hubs. The most interesting feature of MPRouter is Voice over Frame Relay. To do this, special cards are installed in it, allowing the connection of ordinary telephone or fax machines, as well as analog (E&M) and digital (E1, T1) automatic telephone exchanges. The number of simultaneously served voice channels can reach two or more dozen. Thus, MPRouter can be used simultaneously as a voice and data integration tool, a router, and an X.25 / Frame Relay node.
The third group of Motorola ISG products is the backbone equipment of global networks. The 6500plus family is expandable, fault-tolerant and redundant to create powerful switching and access nodes. They include various sets of processor modules and I / O modules, allowing for high-performance nodes with 6 to 54 ports. In corporate networks, such devices can be used to build complex systems with a large number of connected resources.
It is interesting to compare Cisco and Motorola routers. We can say that for Cisco, routing is primary, and communication protocols are only a means of communication, while Motorola focuses on communication capabilities, considering routing as another service implemented using these capabilities. In general, the routing facilities of Motorola products are poorer than those of Cisco, but sufficient for connecting end nodes to the Internet or corporate network.
Other things being equal, the performance of Motorola products is perhaps even higher, and at a lower price. So the Vanguard 300, with a comparable set of features, turns out to be about one and a half times cheaper than its closest analogue, the Cisco 2501.
Eicon Technology Solutions
In many cases, it is convenient to use the solutions of the Canadian company Eicon Technology as the peripheral equipment of corporate networks. Eicon solutions are based on the EiconCard universal communication adapter supporting a wide range of protocols - X.25, Frame Relay, SDLC, HDLC, PPP, ISDN. This adapter is installed in one of the computers on the local network, which becomes a communication server. This computer can be used for other tasks as well. This is possible due to the fact that EiconCard has a sufficiently powerful processor and its own memory and is able to implement the processing of network protocols without loading the communication server. Eicon software tools allow building both gateways and routers on the basis of EiconCard, work under control of almost all operating systems on the Intel platform. Here we will look at the most interesting ones.
The Eicon family of solutions for Unix includes an IP Connect router, X.25 Connect gateways and SNA Connect. All of these products can be installed on a computer running SCO Unix or Unixware. IP Connect allows IP traffic to be carried over X.25, Frame Relay, PPP or HDLC and is compatible with equipment from other manufacturers such as Cisco and Motorola. The package includes Firewall, data compression and SNMP management tools. The main area of application for IP Connect is connecting application servers and Unix-based Internet servers to the data network. Naturally, the same computer can be used as a router for the entire office in which it is installed. There are several advantages to using an Eicon router instead of "pure hardware" devices. First, it is easy to install and use. From the point of view of the operating system, the EiconCard with IP Connect installed looks like another network card. This makes setting up and administering IP Connect a breeze for anyone using Unix. Secondly, direct connection of the server to the data transmission network allows to reduce the load on the office LAN and to provide that very single point of connection to the Internet or to the corporate network without installing additional network cards and routers. Third, such a "server-centric" solution is more flexible and scalable than traditional routers. There are a number of other benefits that come with combining IP Connect with other Eicon products.
X.25 Connect is a gateway that allows LAN applications to communicate with X.25 resources. This product allows Unix users and DOS / Windows and OS / 2 workstations to connect to remote e-mail systems, databases and other systems. By the way, it should be noted that Eicon gateways today are perhaps the only product widespread in our market that implements the OSI stack and allows you to connect to X.400 and FTAM applications. In addition, X.25 Connect allows you to connect remote users to a Unix machine and terminal applications on stations on a local network, as well as to organize the interaction of remote Unix computers via X.25. By using standard Unix features with X.25 Connect, protocol conversion can be implemented, i.e. translate Unix access via Telnet into an X.25 call and vice versa. It is possible to connect a remote X.25 user using SLIP or PPP to the local network and, accordingly, to the Internet. In principle, similar protocol translation capabilities are available in Cisco routers running IOS Enterprise software, but this solution is more expensive than Eicon and Unix combined.
Another product mentioned above is SNA Connect. This is the gateway for connecting to IBM mainframe and AS / 400. It is typically used in conjunction with user software - 5250 and 3270 terminal emulators and APPC interfaces - also manufactured by Eicon. Analogs of the solutions discussed above exist for other operating systems - Netware, OS / 2, Windows NT, and even DOS. Of particular note is Interconnect Server for Netware, which combines all of the above capabilities with remote configuration and administration tools and a client authorization system. It includes two products - Interconnect Router, which allows for IP, IPX and Appletalk routing and is, in our opinion, the best solution for interconnecting remote Novell Netware networks, and Interconnect Gateway, which provides, in particular, powerful connectivity to SNA. Another Eicon product designed to work in the Novell Netware environment is WAN Services for Netware. It is a set of tools that enable Netware applications to be used over X.25 and ISDN networks. Using it in conjunction with Netware Connect allows remote users to connect to the local network via X.25 or ISDN, and also provide an exit from the local network in X.25. There is an option for delivering WAN Services for Netware along with Novell's Multiprotocol Router 3.0. This product is called Packet Blaster Advantage. Packet Blaster ISDN is also available, which does not work with EiconCard, but with ISDN adapters also supplied by Eicon. In this case, various connection options are possible - BRI (2B + D), 4BRI (8B + D) and PRI (30B + D). The WAN Services for NT product is designed to work with Windows NT applications. It includes an IP Router, a means of connecting NT applications to X.25 networks, support for Microsoft SNA Server, and a means of accessing remote users over X.25 to a LAN using Remote Access Server. To connect a Windows NT server to an ISDN network, the Eicon ISDN adapter can also be used in conjunction with the ISDN Services for Netware software.
Methodology for building corporate networks.
Now that we have listed and compared the main technologies that a developer can employ, let's move on to the basic questions and techniques used in designing and developing a network.
Network requirements.
Network designers and network administrators always strive to ensure that three basic network requirements are met, namely:
scalability;
performance;
controllability.
Good scalability is required so that both the number of users on the network and the application software can be changed effortlessly. High network performance is required for most modern applications to function properly. Finally, the network must be manageable enough that it can be reconfigured to meet the ever-changing needs of the organization. These requirements reflect a new stage in the development of network technologies - the stage of creating high-performance corporate networks.
The uniqueness of new software tools and technologies complicates the development of corporate networks. Centralized resources, new classes of programs, other principles of their application, changes in the quantitative and qualitative characteristics of the information flow, an increase in the number of concurrent users and an increase in the power of computing platforms - all these factors must be taken into account in their totality when developing a network. Now there are a large number of technological and architectural solutions on the market, and choosing the most suitable one is a rather difficult task.
In modern conditions, for the correct design of the network, its development and maintenance, specialists must take into account the following issues:
o Change in organizational structure.
When implementing a project, you should not "separate" software specialists and network specialists. When developing networks and the entire system as a whole, a single team of specialists of different profiles is needed;
o Use of new software tools.
It is necessary to get acquainted with the new software at an early stage of network development in order to be able to timely make the necessary adjustments to the tools planned for use;
o Researching different solutions.
It is necessary to evaluate various architectural solutions and their possible impact on the operation of the future network;
o Checking networks.
Test the entire network or parts of it early in development. To do this, you can create a prototype of the network, which will allow you to evaluate the correctness of the decisions made. In this way, you can prevent the appearance of various kinds of bottlenecks and determine the applicability and approximate performance of different architectures;
o Choice of protocols.
To choose the right network configuration, you need to evaluate the capabilities of the various protocols. It is important to determine how network operations that optimize the performance of one program or suite of programs can affect the performance of others;
o Choice of physical location.
When choosing a place to install servers, you must first of all determine the location of users. Is it possible to move them? Will their computers be connected to the same subnet? Will users have access to the global network?
o Calculation of critical time.
It is necessary to determine the acceptable response times of each application and the possible periods of maximum load. It is important to understand how abnormal situations can affect the health of the network, and determine whether a reserve is needed to organize the continuous operation of the enterprise;
o Analysis of options.
It is important to analyze the different uses of the software on the web. Centralized storage and processing of information often creates additional load at the center of the network, and distributed computing may require strengthening of local networks of workgroups.
Today there is no ready-made, debugged universal method, following which, you can automatically carry out the whole range of measures for the development and creation of a corporate network. This is primarily due to the fact that there are no two absolutely identical organizations. In particular, each organization is characterized by a unique leadership style, hierarchy, and business culture. And if we consider that the network inevitably reflects the structure of the organization, then we can safely say that no two identical networks exist.
Network architecture
Before starting to build a corporate network, you must first define its architecture, functional and logical organization and take into account the existing telecommunications infrastructure. A well-designed network architecture helps assess the feasibility of new technologies and applications, serves as a foundation for future growth, determines the choice of network technologies, helps to avoid unnecessary costs, reflects the connectivity of network components, significantly reduces the risk of incorrect implementation, etc. The network architecture forms the basis of the technical specifications for the network being created. It should be noted that a network architecture differs from a network design in that, for example, it does not define the exact schematic diagram of the network and does not regulate the placement of network components. The network architecture, for example, determines whether some parts of the network will be based on Frame Relay, ATM, ISDN, or other technologies. The network design should contain specific guidelines and estimates of parameters, for example, the required bandwidth, the actual bandwidth, the exact location of the communication channels, etc.
There are three aspects of the network architecture, three logical components:
principles of construction,
network templates
and technical positions.
Design principles are used in network planning and decision making. Principles are a set of simple instructions that describe, in sufficient detail, all aspects of building and operating a deployed network over an extended period of time. As a rule, the formation of principles is based on the corporate goals and basic methods of doing business of the organization.
The Principles provide the primary link between corporate strategy and networking. They serve to develop technical positions and network templates. When developing a technical assignment for a network, the principles of building a network architecture are set out in the section that defines the general goals of the network. The technical position can be viewed as a target description defining the choice between competing alternative network technologies. The technical position specifies the parameters of the selected technology and gives a description of a single device, method, protocol, service provided, etc. For example, when choosing a LAN technology, you need to consider speed, cost, quality of service, and other requirements. Developing technical positions requires an in-depth knowledge of networking technologies and careful consideration of the organization's requirements. The number of technical positions is determined by the given granularity, network complexity, and organization scale. The network architecture can be described by the following technical items:
Network transport protocols.
What transport protocols should be used to transfer information?
Network routing.
What routing protocol should be used between routers and ATM switches?
Quality of service.
How will the ability to choose the quality of service be achieved?
Addressing in IP networks and addressing domains.
What addressing scheme should be used for the network, including registered addresses, subnets, subnet masks, forwarding, etc.?
Switching in local networks.
What switching strategy should be used in LANs?
Combining switching and routing.
Where and how switching and routing should be used; how should they be combined?
Organization of a city network.
How should the branches of an enterprise located, say, in the same city be connected?
Organization of a global network.
How should the branches of the enterprise communicate over the global network?
Remote access service.
How do remote branch users access the enterprise network?
Network templates are a collection of network structure models that represent the relationship between the components of a network. For example, for a specific network architecture, a set of templates are created to "expose" the network topology of a large branch or WAN, or to show the layering of protocols. Network Templates illustrate a network infrastructure that is described by a complete set of technical items. Moreover, in a well-thought-out network architecture, network patterns in terms of granularity can be as close as possible in their content to technical positions. In fact, network templates are a description of the functional diagram of a network section that has specific boundaries; the following basic network templates can be distinguished: for a global network, for a city network, for a central office, for a large branch of an organization, for a branch. Other templates can be developed for network sections that have any particularities.
The described methodological approach is based on studying a specific situation, considering the principles of building a corporate network in their totality, analyzing its functional and logical structure, developing a set of network templates and technical positions. Various implementations of corporate networks can include certain components. In general, a corporate network consists of various departments connected by communication networks. They can be global (WAN) or metropolitan (MAN). Branches can be large, medium and small. A large department can be a center for processing and storing information. A central office is allocated from which the entire corporation is managed. Various service departments (warehouses, workshops, etc.) can be classified as small branches. Small offices are essentially remote. The strategic purpose of a remote branch is to locate sales and technical support services closer to the consumer. Communication with customers, which has a significant impact on corporate earnings, will be more productive if all employees can have access to corporate data at any time.
At the first step of building a corporate network, the proposed functional structure is described. The quantitative composition and status of offices and branches are determined. The necessity of deploying your own private communication network is substantiated or the choice of a service provider that is able to meet the requirements is made. The development of the functional structure is carried out taking into account the financial capabilities of the organization, long-term development plans, the number of active network users, running applications, and the required quality of service. The development is based on the functional structure of the enterprise itself.
In the second step, the logical structure of the corporate network is determined. Logical structures differ from each other only in the choice of technology (ATM, Frame Relay, Ethernet ...) for building the backbone, which is the central link of the corporation's network. Consider logical structures based on cell switching and frame switching. The choice between these two methods of information transmission is based on the need to provide a guaranteed quality of service. Other criteria can be used as well.
The data transmission backbone must satisfy two basic requirements.
o Ability to connect a large number of low-speed workstations to a small number of powerful, high-speed servers.
o Acceptable speed of response to customer requests.
An ideal backbone should have high data transmission reliability and an advanced control system. A control system means, for example, the ability to configure the backbone taking into account all local conditions and maintain reliability at such a level that, even if some parts of the network fail, the servers remain available. The listed requirements will probably determine several technologies and the final choice of one of them remains with the organization itself. What matters most is cost, speed, scalability, or quality of service.
The logical structure with cell switching is used in networks with multimedia traffic in real time (video conferencing and high-quality voice transmission). At the same time, it is important to soberly assess how necessary such an expensive network is (on the other hand, even expensive networks are sometimes unable to meet some requirements). If this is the case, then the logical structure of the frame-switched network must be taken as a basis. The logical switching hierarchy that combines the two layers of the OSI model can be represented as a three-tier diagram:
The lower layer is used to combine local Ethernet networks,
The middle layer is either an ATM local area network, a MAN network, or a WAN backbone.
The top level of this hierarchical structure is responsible for routing.
The logical structure allows you to identify all possible communication routes between individual sections of the corporate network
Cell switching backbone
When using cell switching technology to build a network backbone, high-performance ATM switches combine all Ethernet switches of the workgroup level. Operating at the second layer of the OSI reference model, these switches transmit fixed-length 53-byte cells instead of variable-length Ethernet frames. This networking concept implies that the workgroup Ethernet switch must have an ATM segmentation and assembly (SAR) output port that converts variable length Ethernet frames to fixed length ATM cells before forwarding information to the ATM backbone switch.
For wide area networks, ATM core switches are capable of providing connectivity to remote regions. Also operating in layer 2 of the OSI model, these switches on the WAN can use T1 / E1 (1.544 / 2.0Mbps), T3 (45Mbps), or SONET OC-3 (155Mbps). To provide urban connectivity, a MAN network can be deployed using ATM technology. The same ATM backbone network can be used to communicate between telephone exchanges. In the future, within the framework of the client / server telephony model, these stations can be replaced by voice servers on the local network. In this case, the ability to guarantee the quality of service in ATM networks becomes very important when organizing communication with client personal computers.
Routing
As already noted, routing is the third and highest level in the hierarchical network structure. Routing, which operates at the third layer of the OSI reference model, is used to establish communication sessions, which include:
o Communication sessions between devices located in different virtual networks (each network is usually a separate IP subnet);
o Communication sessions that go through the global / city
One strategy for building a corporate network is to install switches at the lower layers of the overall network. The local area networks are then connected using routers. Routers are required to subdivide a large organization's IP network into many distinct IP subnets. This is to prevent the "broadcast explosion" associated with the operation of protocols such as ARP. To keep unwanted traffic from spreading over the network, all workstations and servers must be split into virtual networks. In this case, routing controls communication between devices belonging to different VLANs.
Such a network consists of routers or routing servers (logical core), a network backbone based on ATM switches, and a large number of Ethernet switches located at the edge. Except in special cases, such as the use of video servers that connect directly to the ATM backbone, all workstations and servers must be connected to Ethernet switches. This network design will help localize internal traffic within workgroups and prevent such traffic from being pumped through ATM backbone switches or routers. Ethernet switch bundling is done by ATM switches, usually located in the same branch. It should be noted that multiple ATM switches may be required to provide sufficient ports to connect all Ethernet switches. Typically, in this case, a 155Mbps connection is used over multimode fiber optic cable.
The routers are located away from the ATM backbone switches because these routers need to be moved out of the primary communication paths. This design makes routing optional. It depends on the type of communication session and the type of traffic on the network. Routing should be avoided when transmitting video information in real time, as it can introduce unwanted delays. Routing is not needed for communication between devices located in the same virtual network, even if they are located in different buildings on the territory of a large enterprise.
In addition, even in a situation where routers are required for certain communication sessions, placing routers away from ATM backbone switches minimizes the number of routing hops (routing hops refers to the section of the network from the user to the first router or from one router to another). This not only reduces latency, but also reduces the load on the routers. Routing has become widespread as a local area network communication technology in the global environment. Routers provide a variety of services designed for multi-level control of the transmission channel. This includes the general addressing scheme (at the network layer), independent of how the addresses of the previous layer are formed, as well as the conversion from one frame format of the control layer to another.
Routers make decisions about where to route incoming data packets based on the information they contain about the network layer addresses. This information is retrieved, analyzed and compared with the contents of the routing tables to determine which port a packet should be sent to. Then, the link-layer address is extracted from the network-layer address if the packet is to be sent to a segment of a network such as Ethernet or Token Ring.
In addition to processing packets, routers update the routing tables in parallel, which are used to determine the destination of each packet. Routers dynamically create and maintain these tables. As a result, routers can automatically respond to changes in network conditions, such as congestion or damage to communication channels.
Determining the route is a rather difficult task. In a corporate network, ATM switches should function in much the same way as routers: the exchange of information should take place taking into account the network topology, available routes and transmission costs. The ATM switch needs this information to select the best route for a particular end-user-initiated communication session. In addition, the definition of a route is not limited to just making a decision about the path that a logical connection will take after a request for its creation is generated.
The ATM switch can choose new routes if, for some reason, the communication channels become unavailable. At the same time, ATM switches must provide network reliability at the router level. To create a scalable network with high cost efficiency, it is necessary to move routing functions to the edge of the network and provide traffic switching on its backbone. ATM is the only networking technology that can do this.
To select a technology, you must answer the following questions:
Does the technology provide an adequate quality of service?
Can she guarantee the quality of service?
How scalable will the network be?
Is there a choice of network topology?
Are the services provided by the network cost-effective?
How effective will the management system be?
The answers to these questions determine the choice. But, in principle, different technologies can be used in different parts of the network. For example, if certain sections require real-time multimedia traffic support or 45 Mbps speed, then ATM is installed in them. If a section of the network requires interactive processing of requests, which does not allow significant delays, then Frame Relay should be used if such services are available in this geographic area (otherwise, you will have to resort to the Internet).
Thus, a large enterprise can connect to the network via ATM, while branch offices connect to the same network via Frame Relay.
When setting up a corporate network and choosing a network technology with the appropriate software and hardware, the price / performance ratio should be considered. It is difficult to expect high speeds from cheap technologies. On the other hand, it makes no sense to use the most complex technologies for the simplest tasks. Different technologies must be properly combined to achieve maximum efficiency.
When choosing a technology, one should take into account the type of cable system and the required distances; compatibility with already installed equipment (significant minimization of costs can be achieved if it is possible to include already installed equipment in the new system.
Generally speaking, there are two ways to build a high-speed local area network: evolutionary and revolutionary.
The first way is based on the extension of the good old frame relay technology. It is possible to increase the performance of a local network within the framework of this approach by upgrading the network infrastructure, adding new communication channels and changing the method of packet transmission (which is what was done in switched Ethernet). A conventional Ethernet network shares bandwidth, which means that the traffic of all users on the network competes with each other, claiming the entire bandwidth of the network segment. In switched Ethernet, dedicated routes are created, so that real bandwidth of 10 Mbps is available to users.
The revolutionary path involves the transition to radically new technologies, for example, ATM for local area networks.
The rich practice of building local networks has shown that the main issue is the quality of service. This is what determines whether the network can work successfully (for example, with applications such as video conferencing, which are increasingly used in the world).
Conclusion.
To have or not to have its own communication network is a “private matter” of each organization. However, if building a corporate (departmental) network is on the agenda, it is necessary to conduct a deep, comprehensive study of the organization itself, the tasks it solves, draw up a clear document flow diagram in this organization and, on this basis, start choosing the most acceptable technology. One of the examples of building corporate networks is the currently widely known Galaktika system.
List of used literature:
1. M. Shestakov "Principles of building corporate data transmission networks" - "Computerra", No. 256, 1997
2. Kosarev, Eremin "Computer systems and networks", Finance and statistics, 1999
3. Olifer V. G., Olifer N. D. "Computer networks: principles, technologies, protocols", Peter, 1999
4. Materials of the site rusdoc.df.ru
Most companies around the world use these technologies in order to quickly outperform competitors. The area of development data allows not only to compose software for solving various problems, but also to establish communications. They allow you to store and process a significant amount of information that is necessary for the normal operation of the company. The introduction of information technology makes it possible to offer new types of services to clients.
Share your work on social media
If this work did not suit you at the bottom of the page there is a list of similar works. You can also use the search button
PAGE 3
Introduction ………………………………………………………………………… 3
1. Information communications in corporate systems. The concept of a corporate computer network ………………………………………… .5
2. Requirements for IO in corporate IS ………………… .14
3. Task ……………………………………………………………………… ..17
Conclusion ……………………………………………………………………… .27
References …………………………………………………………… 29
Introduction
The concept of "information technology" is inherently associated with computer technology and various auxiliary means. Thanks to these technologies, in all branches of production, it becomes possible to accumulate and process a wide variety of information.
The use of a number of techniques allows you to increase the efficiency of the production process and bring your business to a completely new level.
Most companies around the world use these technologies in order toquickly overtake competitors... This makes the field of information technology one of the most demanded in business.
It is worth recalling that in this area there is a special demand for qualified personnel. Information systems specialists successfully create a variety of solutions, improving their creative and technical skills.
The area of development data allows not only to compose software for solving various problems, but also to establish communications. Over time, companies have become increasingly decentralized. It becomes more and more difficult for them to save and use the information received.
The management of each enterprise is aware of the full risk of lack of control over all data. The larger the company, the higher the risk of leakage of valuable information.
Information technology is most widely used in the medical, banking, government and transport sectors. They allow you to store and process a significant amount of information that is necessary for the normal operation of the company.
The introduction of information technology makes it possible to offer new types of services to clients. Thanks to constant improvement, more and more companies are switching to automated information accounting systems.
Thanks to the introduction of information technology, companies can successfully compete in the global market. The faster information is obtained and implemented, the more success a company can achieve. Information technology can save time and reduce production costs.
1. Information communications in corporate systems. The concept of a corporate computer network.
In the economies of developed countries, small enterprises and firms occupy a significant place, the number of which has significantly increased in recent years. As world practice shows, small enterprises have a number of advantages over large ones:
Flexibility and efficiency in actions;
Easy adaptability (adaptation) to local conditions;
The possibility of faster implementation of ideas;
High capital turnover;
Integration of all business processes for sales, material and technical supply within only one enterprise;
Low management costs, which is characterized by a fairly simple organization of automated information management technology at such an enterprise.
In the conditions of modern market relations, large-scale business has been widely developed, which is characterized by forms of organization based on the combination of enterprises and firms into aggregate structures. These are collective associative forms, which include: corporations, business associations, concerns, holding companies, consortia, conglomerates, syndicates, financial and industrial groups, etc.
The size of such associations is due to the desire to improve the efficiency of activities by reducing the costs of production and sales of products, the introduction of modern technologies that require significant costs, the development of diversification processes, which are implemented by combining territorially disunited enterprises or separating branches into independent organizations with the empowerment of their management functions in a certain sphere of activity to serve the corporation as a whole (separation of production, sales and supply organizations, etc.).
Corporations and associations operate in the industries, transport, trade, utilities, etc. There are also banks, insurance companies, stock exchanges, tax system, government bodies that have a similar organizational structure. In large organizations, two forms of management have developed - centralized and decentralized.
Organizations with centralized management are characterized by the distribution of functions and powers among structural divisions with strict coordination of production and economic activities in the management apparatus.
The decentralized form is characterized by the allocation of strategic business units or profit centers within the organization, the activities of which lend themselves to independent planning and have their own budget. In this case, the department management apparatus is endowed with rather broad powers, it is responsible for the results of production and economic activities, for the competitiveness of the company's products. For senior management, real opportunities are being created to engage in long-term planning and expanding external contacts.
In the first and second cases, the corporation of the system is formed due to organizational, technological, informational and other ties that unite geographically dispersed departments, built on a variety of technological platforms, horizontally and vertically.
The main difference between the two types of management of large organizations is the organization of automated information technology.
With centralized management, the technology is focused on the concentration of information resources in the headquarters with strict restrictions on the levels of access to corporate data.
With decentralized management, along with the concentration of information, information segments are allocated in corporate data warehouses for each local area network of a branch or department.
For effective management of large organizations with a large number of branches, a corporate computer network is being built, on the basis of which information links are formed between local computer networks of individual structural divisions.
A corporate computer network is an integrated, multi-machine, distributed system of one enterprise, which has a territorial dispersion, consisting of interacting local computer networks of structural divisions and a communication subsystem for transmitting information.
Implementation of unified access of specialists from various departments of large enterprises to communication resources;
Unified centralized management, administration and maintenance of information and communication resources;
Organization of access to structured information in on-line and off-line modes;
Organization of a unified e-mail and electronic document management system;
E-mail protection based on international standards, with the implementation of the creation of secure gateways to existing data transmission networks operating under the POP3, SMTP, UUCP protocols;
Organization of a global directory service for the benefit of subscribers of a corporate computer network based on the X.500 protocol;
Implementation of a unified user interface that provides users with the means of working with the communication resources of the corporate computer network;
Interaction of the corporate network of large enterprises with the business systems of other organizations, computer networks of state institutions, financial and credit authorities participating in information exchange as subscribers of a telecommunications corporate system;
Functional scalability, ensuring the construction of a corporate computer network, as a constantly developing and improving one, open for the introduction of new hardware and software resources, allowing to develop and improve the composition and quality of information and communication services without disrupting the normal functioning of the network.
The determining factor in organizing corporate computer networks and organizing information links between divisions of large enterprises and organizations of various types, where distributed data processing in the LAN of branches and data concentration in an automated corporate information storage is carried out, is the ease of access to information resources. In this regard, the basis of the modern approach of technical solutions in the construction of information technology in corporate systems is the "client-server" architecture.
The real spread of the "client-server" architecture became possible due to the development and widespread introduction into practice of the concept of open systems. The main meaning of the open systems approach is to simplify the process of organizing the interoperability of computer networks through international and national standardization of hardware and software interfaces. The main reason for the development of the concept of open systems was the widespread transition to the organization of corporate computer networks and the problems of integrating hardware and software that arose in connection with the unification of various platforms and topologies of local computer networks of structural divisions and branches.
However, the implementation of the "client-server" architecture in corporate computer networks, which use various technical solutions when building local computer networks in branches and structural divisions that support various data transfer protocols, leads to their overload with network details to the detriment of functionality.
An even more complex aspect of this problem is associated with the possibility of using different data formats in different nodes of heterogeneous local area networks and LANs, united into a corporate system. This is especially important for high-level servers used - telecommunications, computing, databases.
The general solution to the problem of mobility of an automated information technology of a corporate system based on a client-server architecture is to rely on software packages that implement remote procedure call protocols. With these tools, a call to the server at the remote site looks like a normal procedure call.
Such organization of information links in corporate systems provides access to data of any level, providing not only all the necessary information, but also making it possible to control the work of the company's structural divisions with the required degree of detail.
A full-scale reflection of production processes makes it possible to bring automated corporate information technology closer to the company's problems, to organize the adoption of optimal decisions in the middle and upper levels of management, to put the management process on the basis of modeling and forecasting economic situations.
In large enterprises, firms, corporations, information processing processes differ depending on the requirements for solving functional problems, on the basis of which information flows are formed in corporate management systems (an enlarged diagram of information flows of a corporate system is shown in Figure 1).
Rice. 1. An enlarged scheme of information flows of the corporate system
Organization of the work of the board (central office). The main task is to prepare a strategic development plan and manage the overall activities of the company. This block of the automated corporate system is responsible for information support for the work of the board. The main form of work with information in this block is the receipt and processing of information, on the basis of which the strategic direction of the organization's development is developed. The developed strategic development plan is communicated to all structural divisions through telecommunications.
Organization of work of economic and financial services. This block ensures the functioning of the financial directorate and the accounting department of the organization. The main tasks of financial services are to form a generalized picture of the firm's work for the board, to optimize the taxation of the firm, to summarize all the financial information of the organization's activities and to bring the information to the top management of the firm.
Legal support. The main task is to strengthen the legal and property status of the company. In this module, information is processed, on the basis of which the following functions are performed:
Preparation and maintenance of a base of regulatory and reference information that regulates the external activities of the organization;
Development and legal examination of documents regulating the internal functioning of the company;
Legal expertise of concluded transactions and contracts, etc.
Legal information is communicated primarily to senior management, and is also consumed by all interested services of the organization.
The main functional tasks of the organization are the preparation of consolidated analytical reports to support the adoption of long-term decisions and the provision of an operational check of the organization's external relations based on information resources coming from various sources of information, as well as the processing of operational information for solving the functional tasks of the corporation, its structural divisions and making management decisions in real time at all corporate levels.
The organization of the solution of the main tasks for the processing of information and the management of a large company or corporation is based on a common information space, the construction of a corporate automated storage of information, which allows you to manage the current activities of the company, as well as develop strategic plans for the development of the corporation. The common information space is the organization of software, hardware, information compatibility of various hardware platforms and data exchange architectures at all levels of management and in various corporate links of the system.
A corporate computer network is a multi-machine system of one enterprise, consisting of interacting LAN units.
Corporate networks are referred to as distributed networks, or MAN (Metropoliten Area Net). In their ideology and purpose, they are close to a LAN, but individual PCs of such a network can be located at a remote distance and communicate with special communication channels. Distributed networks are used, for example, to connect central offices or banks with their branches (including in other countries), etc. A distributed network, in which a special communication system of messaging (e-mail, fax, joint work on documents) is organized, is called a corporate network in Micro Soft's terminology.
However, most often the term corporate network refers to the union of several LANs located in various structural divisions of one firm, which can be built on various technical, software and information principles.
Building a corporate computer network provides:
1. implementation of access for specialists from various departments of large enterprises to common corporate information resources;
2. unified centralized management, administration and maintenance of information and communication resources;
3.organization of a unified e-mail and electronic document management system;
4. effective protection of corporate information resources from unauthorized access;
5.interaction of the corporate network of large enterprises with the business systems of other organizations, computer networks of state institutions, financial and credit authorities, etc., participating in information exchange as subscribers of the telecommunications corporate system;
6.functional scalability, ensuring the construction of a corporate computer network, as a constantly developing and improving one, open for the introduction of new hardware and software resources, allowing to develop and improve the composition and quality of information and communication services without disrupting the normal functioning of the network.
2. Requirements for IO in corporate IS.
Requirements for information support overlap with the requirements for information that passes through this support. It is advisable to base them, first of all, on the usefulness of information for decision-making in the quality management system in particular and in the CS in general. Along with this obvious requirement and those requirements that apply to the documentation of systematic quality management, the information under consideration should be subject to such requirements as comprehensibility, relevance, one-time input and reliability.
Comprehensibility means that the quality information must be understandable to its user. This does not exclude, if necessary, the presentation of rather complex information.
The relevance of information should be understood as referring only to product quality, allowing timely decisions on quality management of a preventive-permanent nature to be taken. Relevance is determined by the content, materiality and timeliness of the information. For example, information can be considered immaterial if it does not significantly influence quality management decisions.
One-time input should be understood as the requirement for a single input of information on quality management into a data bank with subsequent reusable use, which will reduce its ambiguity by reducing the likelihood of making mistakes (with repeated input of information).
Reliability assumes that the information does not contain any serious (material) errors. At the same time, it must truthfully, fully and impartially (neutral) reflect the expected (possible) and real (actual) product quality and the state of all quality management processes.
For information support, the requirements are summarized in table 1
Table 1.
"Requirements for information support"
|
Required property |
Way of implementation |
|
|
Unambiguity |
Methods of work with information support (IO) should be strictly regulated by a regulatory document, in addition, it is desirable that the IO itself does not allow improper work with it |
|
|
Scalability |
The IO should work at different production volumes, i.e. decrease / increase in the volume or frequency (rate) of production, and, as a consequence, changes in fixed and circulating production assets should not affect the performance of the system |
|
|
Relevance |
Information entered into and generated by the IO must be time stamped by the IO |
|
|
Personification |
Manipulations with information in the IO must be identified by counterparties (personalized) |
|
|
Sharing access |
Different counterparties working with the input and output of information should have different rights to access and change information in the IO based on personification |
|
|
Flexibility |
Changes in the information flow of production should be transferred to the IO with minimal effort |
|
|
Integrability * |
IO must support import / export of data to work with other systems of the enterprise |
|
|
Adequacy |
The information entered into the IO should be checked when entering, the output - when outputting |
* the property is most relevant for automated IO systems.
Information support is a supporting subsystem of the product quality management mechanism along with such support subsystems as legal, material and technical, metrological, personnel, organizational, technological and financial.
Thus, information support is, first of all, a system.
This is justified by the presence of stable connections between its elements, and also meets the requirements:
1) is not reduced to a simple collection of elements;
2) dividing the system into separate parts, studying each of them separately, it is impossible to know all the properties of the system as a whole.
3. Task
In the Labor Code of the Russian Federation, find a list of the mandatory conditions of an employment contract. Find the relevant information in the "Consultant Plus" system.
Solution
The requirements for the content of the employment contract are established by Art. 57 of the Labor Code of the Russian Federation.
In order for an employment contract to be recognized as compliant with legislation during any inspection, it must contain:
All conditions that must be included in the contract;
Only those conditions that do not contradict the current legislation;
Only those conditions that do not contradict other documents of the company, for example, a collective agreement, internal labor regulations and other local regulations.
In Art. 57 of the Labor Code defines the composition of the mandatory information and conditions included in the text of the employment contract.
Mandatory information that should be indicated in the employment contract:
1. the surname, name, patronymic of the employee and the name of the employer (surname, name, patronymic of the employer - an individual);
2. information about the identity documents of the employee and employer - an individual;
3. taxpayer identification number (for employers, with the exception of employers who are individuals who are not individual entrepreneurs);
4. information about the representative of the employer who signed the employment contract, and the basis by virtue of which he is endowed with the appropriate powers. An employment contract on behalf of the employer-organization may be signed by its director, acting on the basis of the charter, by the head of the personnel service, acting on the basis of a power of attorney, by the director of the representative office (branch) of the organization, acting on the basis of a power of attorney and regulations;
5. place and date of the conclusion of the employment contract.
List of mandatory conditions of the employment contract.
The list of mandatory conditions of an employment contract is established by Part 2 of Art. 57 of the Labor Code.
These include:
A) Place of work. The employment contract must specify the place of work with an indication of the separate structural unit and its location. Recording a structural unit and a specific place of work in an employment contract can also play into the hands of an employer. This will deprive the employee of the grounds to justify his absence from the workplace by the fact that he was allegedly on the territory of the enterprise.
B) Labor function. In the employment contract, it is imperative to define the labor function of the employee. The labor function is work according to the position (profession, specialty) in accordance with the staffing table, specifying qualifications, the specific type of work entrusted to the employee. Job responsibilities are usually recorded in the job description, but in its absence, they can be spelled out in the employment contract.
C) Date of commencement of work. A prerequisite for an employment contract is the date of commencement of work, and for a fixed-term employment contract - the duration and circumstances (reasons) that served as the basis for its conclusion.
D) Terms of remuneration. This is a specific size of the wage rate or salary of the employee, additional payments, allowances and incentive payments. In some situations, references to the procedure for calculating earnings, given in the local regulations of the company or in the collective agreement, are permissible. But in this case, the employee must be familiarized with the content of the documents against signature.
E) Mode. The specific working hours and rest hours are indicated in the employment contract if for this employee it differs from the general rules in force for the employer.
G) Compensation. In the employment contract, it is imperative to indicate the amount of compensation for hard work and work with harmful and (or) dangerous working conditions, if the working conditions at the workplace are recognized as difficult or harmful (dangerous).
H) The nature of the work. Employees of some professions have a special nature of work: mobile, traveling, on the road, etc. The clause on the nature of the work must be included in the employment contracts of couriers, forwarders, drivers or other employees whose work is traveling in nature.
I) Condition on compulsory social insurance. This condition reflects the fact that from the moment of the conclusion of the employment contract, the employee becomes the insured person and in the event of illness, pregnancy or injury, he is entitled to receive insurance benefits.
K) Other conditions. Other obligatory conditions may be included in the employment contract. They are indicated in special cases provided for by labor legislation and other regulatory legal acts containing labor law norms.
How to take into account the interests of the employer in the employment contract?
The employer's interests can be taken into account in the employment contract in the section on additional conditions.
The Labor Code provides for the possibility of supplementing an employment contract with the following conditions:
* specify the place of work (indicating the structural unit and its location);
* establish a trial period;
* determine the responsibility for the disclosure of secrets protected by law (state, official, commercial or other);
* agree on the term of work after training at the expense of the employer;
* provide the possibility of additional insurance for the employee;
* guarantee the improvement of the social and living conditions of the employee and his family members;
* to specify in relation to the working conditions of this employee, his rights and obligations and the rights and obligations of the employer.
Additional conditions included in the employment contract should not worsen the employee's position.
Which of the permissible additional conditions is most beneficial to the employer?
Trade secret protection.
In the employment contract, you can prescribe the employee's obligations related to the protection of the employer's commercial secrets.
According to Art. 11 of the Federal Law of July 29, 2004 N 98-FZ "On Commercial Secrets", the employer's commercial secret can be protected by law and the court if the company establishes and adheres to the commercial secret regime. This regime is considered established after the owner of information constituting a trade secret has taken certain measures to protect the confidentiality of information. One of such mandatory measures is the regulation of relations on the use of information constituting a trade secret by employees on the basis of employment contracts.
Conditions of education.
Many modern companies train newly hired workers in the intricacies of the profession, and at their own expense.
A clause can be added to the employment contract, according to which the employee is obliged to work after the training for the period specified in the contract, if the training is carried out at the expense of the employer.
If you train an employee, and you do not specify the item mentioned in the employment contract, then the employer runs the risk of spending time and money on training the employee for a competitor.
The specified clause should be entered into the contract only if the accepted employee will be sent for training even before starting work. If training is planned in the future, then you can do without this condition, and then draw up an additional agreement with the employee to the employment contract.
Material liability of the employee.
Written agreements on full material liability can be concluded only with adult employees who directly serve or use monetary, commodity values or other property (part 1 of article 244 of the Labor Code of the Russian Federation). Moreover, the list of jobs and categories of workers with whom such an agreement can be concluded, its standard forms are approved in the manner established by the Government of the Russian Federation.
Currently, the List of positions and jobs replaced or performed by employees is in force, with which the employer can conclude written agreements on full individual material responsibility for the shortage of entrusted property, approved by the Resolution of the Ministry of Labor and Social Development of the Russian Federation of December 31, 2002 N 85. Before fixing the names positions in the staffing table and in the employment contract, they should be compared with the text of the List. If it is illiterate to define them, then subsequently it will become impossible to conclude an agreement on full material liability. The Labor Code stipulates that if the provision of compensations and benefits or the existence of restrictions is associated with the performance of work in certain professions, then their name and qualification requirements should be established in accordance with qualification reference books approved in the manner established by the Government of the Russian Federation.
With employees holding the positions of deputy head of the organization and chief accountant, there is no need to draw up separate agreements on full liability. According to Part 2 of Art. 243 of the Labor Code, their material liability in full amount of damage caused to the employer is established precisely by the employment contract.
Probation.
Such an additional condition of the employment contract in the interests of the employer:
* it is a good method of motivation. The employee, knowing that he is being watched, evaluated and may be fired, almost always works diligently.
* the establishment of a probationary period expands the list of grounds for dismissing a negligent employee in connection with unsatisfactory test results (Article 71 of the Labor Code of the Russian Federation).
Term of the contract.
An employment contract that is beneficial for the employer is the establishment of the term of its validity. However, not every employment contract can be time-limited.
An employment contract concluded for a certain period in the absence of sufficient grounds for that is considered concluded for an indefinite period (part 5 of article 58 of the Labor Code of the Russian Federation).
An illiterate conclusion of a fixed-term employment contract can lead to the fact that it is recognized as a contract for an indefinite period. And this is fraught not only with a fine for violation of labor laws in the event of an inspection by labor inspectors or the prosecutor's office. If an employee is dismissed due to the expiration of the term of the employment contract while the term is set incorrectly, then the dismissal may be declared illegal. The employee has the right to recover from work and collect from the employer the average earnings for forced absenteeism, compensation for moral damage, expenses for a lawyer, etc.
Article 59 of the Labor Code of the Russian Federation indicates with whom and on what grounds, it is possible to conclude a fixed-term employment contract. In other cases, there is an indefinite term. It is allowed to enter into a fixed-term employment contract with a part-time worker. He can be dismissed due to the expiration of the contract (clause 2 of article 77 of the Labor Code of the Russian Federation).
An employment contract concluded with a part-time job for an indefinite period may be terminated if an employee is hired for whom this work will be the main one (Article 288 of the Labor Code of the Russian Federation). In this case, the employer must warn the part-time worker in writing about the upcoming dismissal at least two weeks before the termination of the employment contract.
Find the relevant information in the "Consultant Plus" system.
(http://www.consultant.ru/search/base/2/)
1. "Labor Code of the Russian Federation" of 12/30/2001 N 197-FZ (as amended on 12/31/2014) (as amended and supplemented, entered into force on 03/31/2015)
The following conditions are mandatory for inclusion in an employment contract:
* place of work, and in the case when an employee is hired to work in a branch, representative office or other separate structural unit of an organization located in another locality - the place of work with an indication of the separate structural unit and its location;
* labor function (work according to the position in accordance with the staffing table, profession, specialty indicating qualifications; the specific type of work entrusted to the employee). If, in accordance with this Code, other federal laws, the provision of compensations and benefits or the existence of restrictions is associated with the performance of work in certain positions, professions, specialties, then the name of these positions, professions or specialties and qualification requirements for them must correspond to the names and requirements specified in qualification reference books approved in accordance with the procedure established by the Government of the Russian Federation, or the relevant provisions of professional standards (as amended by Federal Laws of 28.02.2008 N 13-FZ, of 03.12.2012 N 236-FZ);
* the date of commencement of work, and in the case when a fixed-term employment contract is concluded - also the period of its validity and the circumstances (reasons) that served as the basis for the conclusion of a fixed-term employment contract in accordance with this Code or other federal law;
* conditions of remuneration (including the size of the wage rate or salary (official salary) of the employee, additional payments, allowances and incentive payments);
* working hours and rest hours (if for this employee it differs from the general rules in force for this employer);
* guarantees and compensation for work with harmful and (or) dangerous working conditions, if the employee is hired in appropriate conditions, indicating the characteristics of working conditions at the workplace;
* conditions that determine, if necessary, the nature of work (mobile, traveling, on the road, other nature of work);
* working conditions at the workplace (the paragraph was introduced by the Federal Law of December 28, 2013 N 421-FZ);
* a condition on compulsory social insurance of the employee in accordance with this Code and other federal laws;
* other conditions in cases stipulated by labor legislation and other regulatory legal acts containing labor law norms.
If, when concluding an employment contract, it did not include any information and (or) conditions from among those provided for in parts one and two of this article, then this is not a basis for recognizing an employment contract as not concluded or terminating it. The employment contract must be supplemented with missing information and (or) conditions. In this case, the missing information is entered directly into the text of the employment contract, and the missing conditions are determined by the appendix to the employment contract or a separate agreement of the parties concluded in writing, which are an integral part of the employment contract.
An employment contract may provide for additional conditions that do not worsen the position of the employee in comparison with the established labor legislation and other regulatory legal acts containing labor law norms, a collective agreement, agreements, local regulations, in particular:
About specifying the place of work (indicating the structural unit and its location) and (or) about the workplace;
About the test;
On non-disclosure of secrets protected by law (state, official, commercial and other);
On the employee's obligation to work after training for at least the period established by the contract, if the training was carried out at the expense of the employer;
On the types and conditions of additional insurance for the employee;
Improvement of the social and living conditions of the employee and his family members;
On clarification, in relation to the working conditions of this employee, the rights and obligations of the employee and the employer established by labor legislation and other regulatory legal acts containing labor law norms;
On additional non-state pension provision for an employee (the paragraph was introduced by Federal Law No. 421-FZ, dated 28 December 2013).
By agreement of the parties, the labor contract may also include the rights and obligations of the employee and the employer established by labor legislation and other regulatory legal acts containing labor law norms, local regulations, as well as the rights and obligations of the employee and the employer arising from the terms of the collective agreement, agreements ... Failure to include in the employment contract any of the specified rights and (or) obligations of the employee and the employer cannot be considered as a refusal to exercise these rights or fulfill these obligations.
Conclusion
Today, there are more and more executives and private entrepreneurs, which means that they are considering the use of information technology as an opportunity to achieve efficiency in their main business.
This is considered to be a clear reflection of a specific stage in Russia's development on the path of transition to a market economy: competition is growing, companies are trying to find additional sources of increasing the profitability of their business. Information technology is tuning for the business of companies, fine tuning of a number of functions in order to achieve the greatest work effect.
To change the way businesses use information technology, service providers approach project delivery differently and offer a range of business integration services. This is what our Western colleagues do. If for ordinary system integration the main task of implementing projects was considered to be the creation of an operating IT infrastructure - the combination of all components into a single whole, now a business integrator aims at solving applied problems.
The main criterion for the work of a system integrator is the normative work of an information system with precise functions of performance, security, and for a business integrator, an effect is considered from an economic point of view, an increase in greater efficiency.
It is clear to everyone that good performance of the IT infrastructure is essential. Companies pay great attention to how the tool increases business efficiency. The engineering aspects of the IT infrastructure criticism are replaced by the economic aspects. And the leading players in the system integration market have now restructured their work with clients and can offer a new approach to solving the problem - through information technology.
But despite such positive notes in understanding the real possibilities of information technology for business, it cannot be said that the situation has changed dramatically now: the maximum demand of companies for information services is not observed. For some reason, top management is wary of information technology. So the specifics of the current level of development of Russia and its mentality are being clarified. Information technology for business does not provide any opportunity to improve its efficiency. There is no magic, and if a company has poorly done business processes, it is poorly managed, then nothing, not even information technology, will save it from bankruptcy. Maybe in the distant future they will control the business process without human intervention, but now this does not work yet if you have a poor company that is barely making ends meet.
But information technology in project activities helps teachers who have just decided to engage in this activity. Even if they do not have some kind of strategic plan and they do not know where to start, then information technology can help them and achieve high results.
European information technologies bring much more benefit to steadily developing organizations that need this tool, right up to supporting the development of the company.
But the maximum effect of information technology will be achieved only with an integrated approach to the use of technology.
Bibliography
- Bondarenko A.S., Grinberg A.S., Gobachev N.N. Information technology management. - M .: Alpina Business Books, 2011.
- Grinberg A.S., Gorbachev N.N., Bondarenko A.S.Information technology management: Textbook. manual for universities. - M .: UNITI-DANA, 2012- 479 p.
- Zayats A., Khalikov M. Internet and the World Wide Web: Textbook. allowance. - SPb .: GLTA, 2011.
- Computer modeling of management: Textbook / A.F. Gorshkov, B.V. Evteev, V.A. Korshunov et al. // Under total. ed. N.P. Tikhomirov. - M .: Publishing house "Exam", 2012-528 p.
- Labotsky, V.V. Knowledge management (technologies, methods and means of representation, extraction and measurement of knowledge) / V.V. Labotsky. - Minsk: Sovrem, school, 2011- 392 p.
- Pikuza V., Garashchenko A. Economic and financial calculations in Excel ... Training course. - SPb: Peter, 2011 .-- 396 p.
- Seletkov S., Khoroshilov A. World information resources. - SPB: Peter, 2011.
- Utkin V.B., Baldin K.V.Information systems and technologies in economics: Textbook. for universities. - M: UNITY-DANA, 2012- 335 p.
- Khoroshilov A. Management of information resources. - M .: Finance and statistics, 2012
- Stepanova E.E., Khmelevskaya N.V. Information support of management activities: Textbook. allowance. - M .: FORUM: INFRA-M, 2011 .-- 154 p.
Other similar works that may interest you. Wshm> |
|||
| 8033. | INFORMATION RESOURCES OF CORPORATE INFORMATION SYSTEMS | 111.06 KB | |
| Sources of information in the information system. The entire production process from the point of view of computer science is a continuous process of generating, processing, changing, storing and distributing information. A modern enterprise can be viewed as an effective information center, the sources of information of which are the external and internal business environment. | |||
| 10714. | CHANNELS OF CONNECTION. COMMUNICATION CHANNEL NETWORKS | 67.79 KB | |
| A communication line is an indispensable part of each communication channel, through which electromagnetic waves travel from a transmitting point to a receiving one (in the general case, a channel can contain several lines, but more often the same line is part of several channels). | |||
| 14233. | Design of a local area network for FE "BelovTransAuto" | 466.49 KB | |
| LAN is a network intended for processing storage and transmission of data and is a cable system of a building object or a group of building objects. LANs are used to solve problems such as: Data distribution. In this regard, it is not necessary at every workplace to have drives for storing the same information; Resource allocation. Peripherals can be accessed by all users on the LAN. | |||
| 15842. | Design of a local area network for OJSC OSV Steklovolokno | 1.5 MB | |
| The result of this work is an approximate list and cost of the necessary network equipment for creating a modern local area network of an organization: in total, network equipment and connecting cables will need ... | |||
| 7398. | DEVELOPMENT OF THE CLOSED CORPORATE NETWORK ARCHITECTURE USING THE DJANGO FRAME | 1.39 MB | |
| Using the free Django framework for web applications, in Python, develop a web application for the KKMOO "Youth League for the Development of National Cultures of the Kuban", which implements the fourth and fifth sections of the technical assignment; implement the user's home page, the ability to upload documents to your page | |||
| 11055. | Project of a local area network of the second floor of school No. 19 | 29.79 KB | |
| An effective solution that ensures an increase in the level of educational services provided and supports modern models of lifelong education is the creation and development of an information environment that integrates educational content, user services and the infrastructure of teacher-student networking. | |||
| 1426. | Organization of a workable local area network for automating the workflow of a small enterprise | 805.67 KB | |
| Network topologies Connect the printer to a local network. Computer networks are essentially distributed systems. Computer networks, also called computer networks or data transmission networks, are the logical result of the evolution of two most important scientific and technical branches of modern civilization - computer and telecommunication technologies. | |||
| 13129. | Organization and description of the local area network (LAN) of the service center with Internet access | 2.1 MB | |
| Computer network communication equipment. Calculating the cost of building a network Conclusion List of sources used Introduction Not so long ago, teleworking was a challenge for an employer. | |||
| 9997. | Development and design of a local area network for an organization with two offices and a warehouse | 3.39 MB | |
| The purpose of the analytical part is to consider the existing state of the subject area, the characteristics of the object, the telecommunications system and substantiate proposals for eliminating the identified shortcomings and new technologies. | |||
| 11751. | Banking IS module for finding errors in connecting an operator to a corporate network based on client-server technology | 5.96 MB | |
| The purpose of the final qualification work is to reduce the cost of maintaining the banking information system ClientSberbank; increasing the efficiency of the system by reducing the number of calls to the administrator by making phone calls based on the clientserver technology. Automation of this process allows you to more quickly correct errors in connecting to the server without visiting client workplaces and reduce the number of calls to the operator's point of the ClientSberbank banking information system by sending ... | |||
Introduction
1. The structure of modern corporate networks
1.1 The role of the Internet in corporate networks
1.2 Local networks and client-server systems
2. Application of Intranet technology in corporate data transmission networks
2.1 Fundamental Intranet Principles
2.2 Intranet architecture
3. Principles of building corporate data transmission networks
3.1 Features of the TCP / IP stack
3.2 Virtual networks
3.3 X.25 based networks
3.4 FrameRelay networks
4.1 ATM technology
4.2 Fast Ethernet and Gigabit Ethernet Standards
4.3 100VG-AnyLAN Technology
Conclusion
Bibliography
Introduction
corporate network data ethernet standard
With some delay, in comparison with the West, Russia is slowly but surely beginning to understand the importance of an integrated approach to the automation of enterprises and organizations. From their own experience and thanks to the many publications in the computer press, many have realized that the effectiveness of automation primarily depends on how widely it covers all areas of a legal entity's activity. This is partly why the idea of building corporate information systems (CIS) has recently become so popular.
A corporate information system is a system that uses modern information and computer technologies, directly carrying out organizational, managerial and production activities of an enterprise or organization and is not an auxiliary or service one.
The existence of any corporate information system is unthinkable without network communication channels, the flesh and blood of which is the corporate network. A corporate network is a complex system that includes thousands of various components: computers of various types, from desktop to mainframe, system and application software, network adapters, hubs, switches and routers, cabling. And since life does not stand still, the content of corporate information, the intensity of its flows and the methods of its processing are constantly changing. The latest example of a sharp change in the technology of automated processing of corporate information in plain sight - it is associated with the unprecedented growth in popularity of the Internet in the last 5-7 years.
The changes brought about by the Internet are multifaceted. The WWW hypertext service (WorldWideWeb) has changed the way information is presented to a person, collecting on its pages all of its popular types - text, graphics and sound. Internet transport - inexpensive and accessible to almost all enterprises (and through telephone networks and single users) - greatly facilitated the task of building a territorial corporate network, while at the same time highlighting the task of protecting corporate data when transferring it through a public network with a multimillion population. The TCP / IP stack immediately came out on top, displacing the former leaders of IPX and NetBIOS LANs, and X.25 in WANs.
Thus, this course work reveals issues related to the principles of construction and operation of data transmission networks in distributed corporate networks.
1. The structure of modern corporate networks
Before talking about corporate networks, you need to define what these words mean. Recently, this phrase has become so common that it began to lose its meaning. In this case, the concept of a corporate network means a system that provides information transfer between various applications used in the corporation's system.
The corporate network is considered as a complex system consisting of several interacting layers. At the base of the pyramid, representing the corporate network, lies a layer of computers - information storage and processing centers, and a transport subsystem (Fig. 1), which ensures reliable transmission of information packets between computers.
Rice. 1. Hierarchy of corporate network layers.
Above the transport system, there is a layer of network operating systems that organizes the operation of applications in computers and provides the resources of its computer for general use through the transport system.
Various applications work on the operating system, but due to the special role of database management systems, which store basic corporate information in an orderly way and perform basic search operations on it, this class of system applications is usually separated into a separate layer of the corporate network.
At the next level, system services operate, which, using the DBMS as a tool for finding the necessary information among the millions and billions of bytes stored on disks, provide end users with this information in a form convenient for making a decision, and also perform some common procedures for enterprises of all types. information processing. These services include the WWW service, e-mail system, collaboration systems, and many others.
And, finally, the upper level of the corporate network is represented by special software systems that perform tasks specific to a given enterprise or enterprises of a given type. Examples of such systems are bank automation systems, accounting organization, computer-aided design, process control, etc.
The ultimate goal of the corporate network is embodied in high-level applications, but for them to work successfully, it is absolutely essential that the subsystems of the other layers are clearly performing their functions.
A corporate network, as a rule, is geographically distributed, i.e. uniting offices, divisions and other structures located at a considerable distance from each other. Often, corporate network nodes are located in different cities and sometimes countries. The principles by which such a network is built are quite different from those used to create a local network, even covering several buildings. The main difference is that geographically distributed networks use rather slow (today tens and hundreds of kilobits per second, sometimes up to 2 Mbit / s.) Leased communication lines. If, when creating a local network, the main costs are spent on the purchase of equipment and laying cables, then in wide-area networks the most significant cost element is the rent for the use of channels, which grows rapidly with an increase in the quality and speed of data transmission. This limitation is fundamental, and when designing a corporate network, all measures should be taken to minimize the amount of data transferred. For the rest, the corporate network should not impose restrictions on which applications and how they process the information carried over it.
Applications are understood as the system software - databases, mail systems, computing resources, file service, etc. - and the means with which the end user works. The main tasks of a corporate network are the interaction of system applications located in various nodes, and access to them by remote users.
The first problem that has to be solved when creating a corporate network is the organization of communication channels. If within the same city you can count on leasing dedicated lines, including high-speed ones, then when moving to geographically distant nodes, the cost of leasing channels becomes simply astronomical, and their quality and reliability often turn out to be very low. In fig. 2 shows a corporate network as an example, which includes local and regional networks, public access networks and the Internet.
The natural solution to this problem is to use existing global networks. In this case, it is sufficient to provide channels from offices to the nearest network nodes. The global network will take over the task of delivering information between nodes. Even when creating a small network within the same city, one should keep in mind the possibility of further expansion and use technologies that are compatible with existing global networks. Often the first, if not the only, such network that comes to mind is the Internet.
Rice. 2. Combining various network communication channels into a corporate network.
1.1 RoleInternetin corporate networks
If we look inside the Internet, we will see that information flows through many completely independent and mostly non-profit nodes, connected through the most diverse channels and data networks. The rapid growth of services provided on the Internet leads to overloading of nodes and communication channels, which sharply reduces the speed and reliability of information transmission. At the same time, Internet service providers do not bear any responsibility for the functioning of the network as a whole, and communication channels are developing extremely unevenly and mainly where the state considers it necessary to invest in this. In addition, the Internet binds users to a single protocol — IP (Internet Protocol). This is good when we use standard applications that work with this protocol. The use of any other systems with the Internet is not easy and expensive. If you need to provide mobile users with access to your private network, the Internet is also not the best solution. It would seem that there should be no big problems here - Internet service providers are almost everywhere, take a laptop with a modem, call and work. However, a supplier, say, in Vladivostok, has no obligation to you if you are connected to the Internet in Moscow. He does not receive money for services from you and, naturally, will not provide access to the network. Another Internet issue that has been widely discussed in recent years is security. If we are talking about a private network, it seems quite natural to protect the transmitted information from prying eyes. The unpredictability of information paths between many independent Internet sites not only increases the risk that some overly curious network operator could put your data on disk (technically, it is not that difficult), but also makes it impossible to determine the location of the information leak. Another aspect of the security problem is again related to the decentralization of the Internet - there is no one who can restrict access to the resources of your private network. Since this is an open system where everyone can see everyone, anyone can try to get into your office network and gain access to data or programs.
1.2 Local networks and client-server systems
So, the Internet is a perfectly accessible worldwide global network. Before the Internet appeared, there were many local computer networks installed inside large enterprises, organizations and firms. This is not about a single information space, but about the information field within the organization.
It is clear that the success of the commercial and entrepreneurial activities of the company depends on the correct construction of a system for the exchange of internal information, which includes:
· Automated workplaces for managers, accountants, planners, administrators, engineers and other categories of workers;
· Databases and knowledge bases;
· Centers of reference, analytical information;
· Email, electronic data interchange, etc.
The structure of any in-house computer network is based on
on the structure of the company itself, therefore inherits the principles of distribution of information resources, the horizontal division of labor based on the creation of divisions, as well as the vertical division of labor.
The main function of any local network is the distribution of information between specific employees, so that two conditions are met:
Any information must be protected from unauthorized use. That is, each employee should work only with the information to which he has the rights, regardless of the computer on which he entered the network.
Working in the same network and using the same technical means of data transmission, network clients should not interfere with each other. There is such a thing as network load. The network should be built in such a way that it does not fail and work fast enough for any number of clients and calls.
Any, even the smallest, network must have an administrator (Supervisor). This is the person (or group of people) who customize it and ensure it runs smoothly. The tasks of administrators include:
· Distribution of information on working groups and between specific clients;
· Creation and support of a common data bank;
· Protection of the network from unauthorized entry, and information - from damage, etc.
If we touch on the technical aspect of building a local computer network, then we can distinguish the following elements:
Interface board in users' computers. This is a device for connecting a computer to a shared LAN cable.
Cabling. With the help of special cables, physical connection is organized between devices on a local network.
Local network protocols. In general, protocols are programs that transport data between devices connected to a network.
In fig. 3 schematically shows the principle of operation of any protocol, local area network or Internet network:
Rice. 3. The principle of data transmission over the network.
Network operating system. It is a program that is installed on a file server and serves to provide an interface between users and data on the server.
File server. It serves to store and place programs and data files that are used for shared user access.
Network printing. It allows many users on a local network to share one or more printing devices.
Local network protection. Network protection is a set of methods used to protect data from damage from unauthorized access or some kind of accident.
Bridges, gateways and routers. They allow networks to be interconnected.
In fig. 4 shows several topologies of local networks.
Rice. 4. Methods for connecting computers to a network.
In the organization of modern local computer networks, the "client-server" technology is widely used. Its essence is shown in Fig. 5.
Rice. 5. Client-server architecture.
The principle of operation of the "client-server" technology:
* the client forms and sends a request to the server database, or rather to the program that processes requests.
* this program manipulates the database stored on the server, in accordance with the request, generates the result and transfers it to the client.
* The client receives the result, displays it on the display and waits for further user actions. The cycle repeats until the user finishes working with the server.
Local networks and the "client-server" systems built on their basis allow organizing group work on information and distributing it among employees. The introduction of these systems in the organization allowed the latter to significantly improve labor productivity, reduce labor costs and communicate with clients, partners, customers, as well as within the company at a qualitatively new level.
However, there are at least three main disadvantages of such systems:
Implementing these systems is costly and complex. But this is inevitable. The problem is different. Programs that process information within an organization are constantly improving: new versions are released, this is due to the growing needs of a developing organization. Replacing old versions with new ones is not a free service. The programmers working in the firm will not even help here.
Different automated systems use different information, process it in different ways and produce different output data: the process of "connecting" information, reports of all divisions of the corporation, is associated with endless format transformations, correctness checks, etc. In short, extra universal software is required, extra highly qualified, and therefore highly paid specialists.
If an organization is a transnational corporation, divisions, branches and representative offices of which are scattered all over the world, then the exchange of vital information between them is a real problem. Here there can be no question of any local network.
In connection with these, as well as many other problems, it became necessary to introduce new systems that would perform the functions of both a global and a local network of an organization. Moreover, it is desirable that the cost of such systems be minimal.
A solution was found: if almost every organization is already connected to the Internet, if it already has its own local network, then why not combine these two things together? The only problem is to ensure the secrecy of internal information, since the Internet is a system open to everyone. The new system was named Intranet.
2.Application of technologyIntranetin corporate data transmission networks
Until a few years ago, the names "Intranet" or "Intranet" were not known in the computer world. However, today these words are encountered, perhaps more often than others. This term denotes a new direction in the development of networks. The importance of this direction is evidenced by the fact that all the leading manufacturers of network software pay increased attention to it. If the management of the enterprise wants their local or corporate network in the present and future tense to meet the modern requirements for networking, then the transition to the Intranet is inevitable. So what does this popular term mean? Novell defines this direction as follows: “Today's corporate networks integrate services originally designed for the global Internet environment, and as a result of their evolution, they can today provide users with flexible new ways to access computing resources and information anytime, anywhere. These corporate networks are called intranets. " Internet and Intranet are not only similar sounding names for networks, but they also have the same construction method, they can use the same software to access information and manage the network, etc.
A fully functional intranet is defined by eight key services, including file handling, printing, directory services, effective security, messaging, the ability to post and view WEB publications, and the organization and management of global networks.
Thanks to the possibilities of operational communication, Internet and Intranet technologies are rapidly penetrating all spheres of human activity, becoming the de facto standard for business interaction. Enterprises that have not yet implemented these technologies are lagging behind the development of a civilized society and, therefore, risk being on the road to bankruptcy.
This chapter discusses the need for and the first steps in intranet technology adoption in an enterprise. The advantages of this technology, first of all, in the enterprise management system are considered. Some variants of organizational and technical solutions in the field of Intranet are given.
2.1 Fundamental principlesIntranet
First, Intranet is an internal information system based on Internet technology, Web services, TCP / IP and HTTP communication protocols, and HTML pages. Intranet is a technology that allows an organization to define itself as a whole as an object, group, family, where everyone knows their role, and everyone's work is aimed at improving and health of the organization. How is this achieved? All tasks, goals, processes, connections, interactions, infrastructure, projects, schedules, budgets and culture, in a word, everything that the organization lives with is interactively, in a single interface, linked together. Moreover, each employee can use the necessary information, and, according to his competence, replenish it. In other words, the Intranet represents the "intelligence" of the organization. The ultimate goal of this intelligence is to organize the desktop of each employee (and the concept of "desktop" has long meant a personal computer) with the minimum cost, time and effort, so as to enable work to be more productive, and products - more timely and competitive.
Second, the Internet is about bringing hardware, technology, and software together. Intranet is something else. If the organization has the Internet, then everything that is needed to build an Intranet already exists. In fact, building an Intranet is like building an individual intelligence. This requires approaches to the study of practical decision-making, operating in the entire information space with clear, clear tasks, the study of information to improve work in the future. All this requires the timely transmission of information to everyone who needs it.
Thirdly, the Intranet is both a local network, a client-server system, and a personal computer - in a word, everything that was previously used in various organizations to work with information. But before, all machines, software, and communication systems were directly in their ownership. It was impossible to have an internal connection of all data without a group of programmers and new software for each new kind of information. With the Intranet, access to all information, applications, data, knowledge, processes, etc. possible in the same browser for the Internet. There is no more huge number of conversions to different formats, which means wasted time, version incompatibilities, etc. Instead, the Intranet connects people together with the Internet, Web servers, databases in the only way, allowing them to easily learn even with old software. ...
Fourthly, Intranet is an opportunity to build an organization on an informational level and provide this information to everyone who needs it. If an employee knows what the company is doing, what is the strategic system of the company's technical vision, what are the principles of leadership, who the clientele and partners are, then he can more clearly focus on his own contribution to the common cause. A single web page that everyone understands that represents the essence of the company is equivalent to success. All branches and representative offices can constantly access the central messages and follow the instructions. Thus, the global network is used not only as a method of cheap transmission of information over long distances, but also as a tool for guiding the process in the organization.
2.2 ArchitectureIntranet
The simplest Intranet diagram is shown in Fig. 6.
Fig. 6. Intranet architecture.
As seen from Fig. 6, the organization retains both a local network and Internet access. All that appears is a new node called the firewall or firewall. Firewall is a computer with special software installed on it, which allows:
· Identify any user entering from outside in order to deny or allow him access;
· Distribute access rights between users;
· Use cryptography, that is, encryption of secret information.
3. Principles of building corporate data transmission networks
The structure of organizations, regardless of the type of activity, includes numerous divisions directly carrying out one or another type of company activity, as well as management, accounting, office, etc. The divisions of the company are permeated with vertical and horizontal ties, they exchange information with each other, as well as perform separate parts of one "big job". At the same time, some of the divisions, for example, the management, financial and supply services, interact with external partners (bank, tax office, suppliers, etc.), as well as with the branches of the company itself.
Thus, any organization is a set of interacting elements (departments), each of which can have its own structure. The elements are interconnected functionally, i.e. they perform certain types of work within the framework of a single business process, as well as informational, exchanging documents, faxes, written and oral orders, etc. In addition, these elements interact with external systems, and their interaction can also be both informational and functional. Moreover, the interaction between all elements of the organization is carried out through the corporate network. And this situation is true for almost all organizations, no matter what type of activity they are engaged in - for a government institution, a bank, an industrial enterprise, a commercial firm, etc.
This general view of the organization allows us to formulate some general principles of building corporate information networks, i.e. information networks throughout the organization. This chapter will consider the approaches and ideas about what should be a corporate information network of a large organization. Particular attention will be paid to the transport layer of the network and the protocols that provide data transfer.
3.1 Features of the stackTCP/ IP
/ IP is an abbreviation for "TransmissionControlProtocol / Internet Protocol". In computer networking terminology, a protocol is a pre-agreed standard that allows two computers to exchange
data. In fact, TCP / IP is not one protocol, but several. That is why it is often called a set, or a suite of protocols, among which TCP and IP are the two main ones (Fig. 7).
Fig. 7. TCP / IP stack.
The TCP / IP software on a computer is a platform-specific implementation of TCP, IP, and other members of the TCP / IP family. It also typically contains high-level applications such as FTP (File Transfer Protocol), which provide command line control over the transfer of files over the Web.
The TCP / IP stack originated from research funded by the Advanced Research Project Agency (ARPA) of the US government in the 1970s. This protocol was developed so that the computing networks of research centers around the world can be interconnected in the form of a virtual "network of networks" (Internetwork). The original Internet was created by converting an existing conglomerate of computer networks called ARPAnet with TCP / IP.
The reason TCP / IP is so important today is because it allows self-contained networks to connect to the Internet or join together to create private intranets. The computing networks that make up an intranet are physically connected through devices called routers or IP routers. A router is a computer that transfers data packets from one network to another. On a TCP / IP-based intranet, information is transmitted in discrete chunks called IP packets or IP datagrams. Thanks to TCP / IP software, all computers connected to the computer network become "close relatives". It essentially hides the routers and underlying network architecture and makes it appear like one big network. Just as Ethernet connections are identified by 48-bit Ethernet IDs, intranet connections are identified by 32-bit IP addresses, which we express in dotted decimal notation (for example, 128.10.2.3). By taking the IP address of a remote computer, a computer on the intranet or on the Internet can send data to it as if it were part of the same physical network. / IP gives a solution to the problem of data between two computers connected to the same intranet, but belonging to different physical networks. There are several parts to the solution, with each member of the TCP / IP family of protocols contributing to the cause. IP, the most fundamental protocol in the TCP / IP suite, transmits IP datagrams over the intranet and performs an important function called routing, essentially choosing the route the datagram will take from point A to point B and using routers to "hop" "between networks." is a higher layer protocol that allows applications running on various host computers on a network to exchange data streams. TCP divides streams of data into chains called TCP segments and transmits them using IP. In most cases, each TCP segment is sent in a single IP datagram. However, if necessary, TCP will split the segments into multiple IP datagrams that fit into physical data frames that are used to transfer information between computers on the network. Because IP does not guarantee that datagrams will be received in the same order in which they were sent, TCP reassembles TCP segments at the other end of the route to form a continuous stream of data. FTP and Telnet are two examples of popular TCP / IP applications that rely on TCP.
Another important member of the TCP / IP stack is UDP (UserDatagram Protocol), which is similar to TCP but more primitive. TCP is a "reliable" protocol because it provides error checking and acknowledgment messages to ensure that data reaches its destination without corruption. UDP is an "unreliable" protocol because it does not guarantee that datagrams will arrive in the order in which they were sent, or even that they will arrive at all. If reliability is a desirable condition, software will be required to implement it. But UDP still has its place in the TCP / IP world, and is used in many programs. The SimpleNetwork Management Protocol (SNMP) application, which is implemented in many TCP / IP implementations, is one example of UDP programs.
Other TCP / IP protocols play less visible but equally important roles in the operation of TCP / IP networks. For example, Address Resolution Protocol (ARP) translates IP addresses into physical network addresses, such as Ethernet identifiers. A related protocol, the ReverseAddressResolution Protocol (RARP), does and does the opposite by converting physical network addresses to IP addresses. Internet Control Message Protocol (ICMP) is an escort protocol that uses IP to exchange control information and control errors related to the transmission of IP packets. For example, if a router cannot transmit an IP datagram, it uses ICMP to inform the sender that there is a problem.
The TCP / IP stack is one of the most widely used transport protocol stacks for computer networks today. The explosive growth in popularity of the Internet has led to changes in the balance of power in the world of communication protocols - the TCP / IP protocols, on which the Internet is built, quickly began to crowd out the undisputed leader of the past - the IPX / SPX stack from Novell. Today, the total number of computers on which the TCP / IP stack is installed is much larger than the total number of computers on which the IPX / SPX stack is installed, and this indicates a sharp change in the attitude of LAN administrators to the protocols used on desktops, since they make up the overwhelming majority of the world's computer park, and it was on them that the Novell protocols required to access NetWare file servers used to work almost everywhere. The process of becoming the TCP / IP stack the number one stack in all types of networks continues, and now any industrial operating system necessarily includes a software implementation of this stack in its delivery set.
Although the TCP / IP protocols are inextricably linked with the Internet, and each of the millions of Internet computers operates on the basis of this stack, however, there are a large number of local, corporate and territorial networks that are not directly part of the Internet, which also use the TCP / IP protocols. To distinguish them from the Internet, these networks are referred to as TCP / IP networks, or simply IP networks.
Local and corporate networks are increasingly using TCP / IP protocols to carry their internal traffic. Until recently, these were mostly networks based on the Unix operating system. The reason was the historical relationship between Unix and TCP / IP — the first TCP / IP stack protocols were implemented in a UnixBSD environment at the University of Berkeley. However, now that TCP / IP protocols are available in every network operating system, there are local TCP / IP networks based on other operating systems.
Of course, one of the obvious reasons for using the TCP / IP stack on local and corporate networks is the ease with which such networks can be connected to the Internet when needed. However, the flexibility and openness of the stack are good enough reasons in themselves to use TCP / IP protocols in stand-alone local and corporate networks.
In parallel with the Internet, there are other public wide area networks operating on the basis of the TCP / IP protocols. Public IP networks provide the customer with a higher level of service compared to the Internet - lower packet delays, protection against unauthorized access, and high availability. Using public IP network services, an enterprise can build the backbone of its corporate network without exposing itself to the risk of attacks from numerous hackers on the Internet.
3.2 Virtual networks
The ideal option for a corporate network would be to create communication channels only in those areas where it is necessary, and transfer over them any network protocols that are required by running applications. At first glance, this is a return to leased communication lines, however, there are technologies for building data transmission networks that allow organizing channels within them that arise only at the right time and in the right place. Such channels are called virtual. A system that combines remote resources using virtual channels can naturally be called a virtual network. Today, there are two main technologies for virtual networks - circuit-switched networks and packet-switched networks. The former include the conventional telephone network, ISDN and a number of other, more exotic technologies. Packet-switched networks are represented by X.25 technologies, Frame Relay and, more recently, ATM. It is too early to talk about the use of ATM in wide area networks. The rest of the types of virtual (in various combinations) networks are widely used in the construction of corporate information systems.
Circuit-switched networks provide a subscriber with several communication channels with a fixed bandwidth per connection. The well-known telephone network provides one communication channel between subscribers. If you need to increase the number of simultaneously available resources, you have to install additional phone numbers, which is very expensive. Even if we forget about the low quality of communication, the limitation on the number of channels and the long connection establishment time do not allow the use of telephone communication as the basis of a corporate network. For connecting individual remote users, this is a fairly convenient and often the only method available. It should only be borne in mind that access to ISDN in our country is the exception rather than the rule.
An alternative to circuit-switched networks is packet-switched networks. When using packet switching, one communication channel is used in a time-sharing mode by many users - in much the same way as in the Internet. However, unlike networks like the Internet, where each packet is routed separately, packet-switched networks require establishing a connection between end resources before transmitting information. After establishing a connection, the network "remembers" the route (virtual channel) through which information should be transmitted between subscribers and remembers it until it receives a signal that the connection is broken. For applications operating in a packet switching network, virtual circuits look like ordinary communication lines - with the only difference that their throughput and introduced delays vary depending on the network congestion.
3.3 Protocol-based networksX.25
The classic packet switching technology is the X.25 protocol. Now it is customary to wrinkle your nose at these words and say: "it is expensive, slow, outdated and not fashionable."
Indeed, today there are practically no X.25 networks operating at speeds higher than 128 Kbps. The X.25 protocol includes powerful error correction tools to ensure reliable delivery of information even on bad links and is widely used where quality communication channels are not available. In our country, they are not almost everywhere.
Naturally, reliability comes at a price — in this case, the speed of the network equipment and the relatively large — but predictable — delays in the dissemination of information. At the same time, X.25 is a universal protocol that allows you to transfer almost any type of data.
Another standard X.25 networking capability is communication over common asynchronous COM ports. Figuratively speaking, an X.25 network lengthens the cable connected to a serial port, bringing its connector to remote resources.
Thus, virtually any application that can be accessed through a COM port can be easily integrated into an X.25 network. Examples of such applications include not only terminal access to remote host computers, but email as well.
Today, there are dozens of public X.25 global networks in the world, their nodes are located in almost all major business, industrial and administrative centers. In Russia, X.25 services are offered by Sprint Network, Infotel, Rospak, Rosnet, SovamTeleport and a number of other providers.
In addition to connecting remote sites, X.25 networks always provide means of access for end users. In order to connect to any resource on the X.25 network, the user only needs to have a computer with an asynchronous serial port and a modem. At the same time, there are no problems with access authorization in geographically remote sites.
Thus, if your resource is connected to an X.25 network, you can access it both from your provider's nodes and through nodes on other networks - that is, from virtually anywhere in the world.
From a security perspective, X.25 networks offer some very attractive capabilities. First of all, due to the very structure of the network, the cost of intercepting information in an X.25 network is high enough to already serve as a good defense. The problem of unauthorized access can also be solved quite effectively by means of the network itself.
The disadvantage of X.25 technology is that it has a number of fundamental speed limits. The first of them is associated precisely with the developed capabilities of correction and recovery. These tools cause delays in the transmission of information and require a lot of processing power and performance from the X.25 equipment, as a result of which it simply "cannot keep up" with fast communication lines. Although there is equipment that has two megabit ports, the actual speed provided by it does not exceed 250 - 300 Kbps per port.
On the other hand, for modern high-speed communication lines, X.25 correction means are redundant and when they are used, the equipment power is often idle.
The second feature that makes X.25 networks look like slow is the encapsulation of the LAN protocols (primarily IP and IPX). All other things being equal, the connection of local networks over X.25 is, depending on the parameters of the network, 15-40 percent slower than when using HDLC over a dedicated line.
Moreover, the worse the communication line, the higher the loss of productivity. Again, we are dealing with an obvious redundancy: LAN protocols have their own means of correction and recovery (TCP, SPX), but when using X.25 networks, you have to do it again, losing speed. It is on these grounds that X.25 networks are declared slow and obsolete.
But before talking about the fact that any technology is outdated, it should be indicated for what applications and in what conditions. On low quality links, X.25 networks are quite efficient and offer significant cost and performance gains over leased lines.
On the other hand, even if you count on a rapid improvement in the quality of communication - a prerequisite for the obsolescence of X.25 - then the investment in X.25 equipment will not be lost, since modern equipment includes the possibility of transition to FrameRelay technology.
3.4 NetworksFrameRelay
Frame Relay technology emerged as a means to realize the benefits of packet switching on high-speed communication lines. The main difference between Frame Relay and X.25 networks is that they eliminate error correction between network nodes. The tasks of restoring the information flow are assigned to the terminal equipment and user software. Naturally, this requires the use of sufficiently high-quality communication channels.
The lack of error correction and complex packet switching mechanisms typical for X.25 allows information to be transmitted over Frame Relay with minimal delays. Additionally, it is possible to enable a prioritization mechanism that allows the user to have a guaranteed minimum information transfer rate for a virtual channel. This capability allows Frame Relay to be used to carry delay-critical information such as real-time voice and video. This relatively new feature is gaining in popularity and is often the primary consideration in choosing Frame Relay as the backbone of the corporate network.
There are also private Frame Relay networks that operate within the same city or use long-distance - usually satellite - leased lines. Building private networks based on Frame Relay allows you to reduce the number of leased lines and integrate voice and data transmission.
4. Main trends in the development of SPD
Although the transition to new high-speed technologies such as Fast Ethernet and 100VG-AnyLAN has begun recently, two new projects are already in development - Gigabit Ethernet and Gigabit VG, proposed by the Gigabit Ethernet Alliance and the IEEE 802.12 committee, respectively.
Interest in technologies for local networks with gigabit speeds has increased due to two circumstances - firstly, the success of relatively inexpensive (compared to FDDI) Fast Ethernet and 100VG-AnyLAN technologies, and secondly, with too great difficulties experienced by ATM technology on paths to the end user.
All work on the creation of technologies that meet modern requirements can be divided into three large groups:
Creation of speed-scalable technology based on Ethernet technology: Ethernet -FastEthernet -GigabitEthernet line. QoS is not supported by any of the technologies in the triad, so additional mechanisms must be implemented in switches and routers to support QoS.
Creation of scalable speed technology, partially compatible with Ethernet, and having built-in capabilities to provide an entry-level quality of service for real-time traffic: 100VG-AnyLAN - 1000VG line.
The use of ATM technology in local area networks, originally designed to support fine grading of quality of service for application-to-application connections and to provide a hierarchy of rates within the same technology. Since ATM technology is significantly different from other technologies of local networks and does not have a cheap option for working on a shared environment, the main efforts of developers are focused on implementing mechanisms for the least painful implementation of this technology in existing local networks and reducing the cost of ATM equipment.
It should be emphasized that the emergence in the early 90s of high-speed multiport bridges, which, in essence, are modern LAN switches, dramatically expanded the functionality of LAN protocols. The use of micro-segmentation, when the network does not have a shared environment between end nodes and switch ports, removes many of the limitations inherent in a particular protocol. An extreme form of departure from the classic use of a time-shared environment is full-duplex versions of LAN protocols that operate exclusively in micro-segments.
Due to the great popularity of switches and, accordingly, full-duplex modes of operation of protocols in local networks, when comparing protocols and choosing the most promising for your network, you must always take into account the existence of two modes of operation of each protocol - half-duplex (in a network with repeater hubs) and full-duplex (in a network on based on switches). Comparing the capabilities and costs of only half-duplex versions will not give a correct picture, as these figures can vary significantly. For example, the maximum diameter of a FastEthernet segment even when using fiber is less than 400 meters in half-duplex mode, and when using full-duplex mode it increases up to 2 kilometers, like other technologies such as FDDI, ATM and 100VG-AnyLAN.
4.1 TechnologyATM
ATM technology (Asynchronous Transfer Mode) is characterized by a wide range of properties that meet the requirements of modern corporate networks. These are high bandwidth, the ability to organize high-speed connections, the provision of guaranteed bandwidth, universal compatibility. Following the path of simplification and standardization of some switching procedures, the developers of ATM made this technology capable of providing high performance and efficiently combining various types of traffic. Characteristic Gigabit Ethernet OC-48c (2.5Gbps ATM) Bandwidth 2.488 Gbps Media Access Control Carrier sense multiple access with collision detection Connection-based access Is there an optimization for real-time applications? Is the physical layer standardized? Work in progress Is the media access level standardized? Work in progress Absent Where is it used? For connecting servers and communication between local networks For dial-up connection of local networks (backbones), for connecting servers, in global and metropolitan networks Distance restrictions < 2 км для многомодового оптоволокна, < 50 м для
неэкранированной витой пары < 2 км для многомодового оптоволокна, < 40 км для
одномодового оптоволокна Package size Variable, no more than 1500 bytes Fixed, cells of 53 bytes Is the quality of service guaranteed? Trunk protocol Bridge connection (spanning tree) Routing (OSPF-based PNNI) Supported by existing devices? Tab. 1. Comparative characteristics of Gigabit Ethernet and 2.5 Gbps (OC-48c) ATM. 4.2 StandardsFastEthernetandGigabitEthernet In 1995, the IEEE committee adopted the FastEthernet specification as a standard, and the networked world received a technology that, on the one hand, solves the most painful problem - the lack of bandwidth at the lower level of the network, and on the other hand, it is very easy to integrate into existing Ethernet networks, which today give the world about 80% of all network connections. The ease of implementation of FastEthernet is due to the following factors: · The general method of access allows using up to 80% of Ethernet adapters microcircuits in network adapters and FastEthernet ports; · Drivers also contain most of the code for Ethernet adapters, and the differences are caused by the new coding method (4B / 5B or 8B / 6T) and the presence of a full-duplex version of the protocol; · The frame format remains the same, which allows protocol analyzers to apply the same analysis methods to FastEthernet segments as for Ethernet segments, only mechanically increasing the speed of operation. The differences between FastEthernet and Ethernet are mainly focused on the physical layer. The developers of the FastEthernet standard have taken into account the trends in the development of structured cabling systems and implemented the physical layer for all popular cable types included in structured cabling standards (such as EIA / TIA 568A) and commercial cabling systems. There are three options for the FastEthernet physical layer: 100Base-TX for two-pair UTP Category 5 unshielded twisted pair cable (or STPType 1 shielded twisted pair cable); 100Base-T4 for 4-pair UTP Category 3,4 or 5 unshielded twisted pair cable; 100Base-FX for multimode fiber optic cable. FastEthernet technology has several key properties that determine the areas and situations of its effective application. These properties include: · A large degree of continuity in relation to the classic 10 megabit Ethernet; · High speed of data transfer - 100 Mb / s; · The ability to work on all major types of modern cabling - UTPCategory 5, UTPCategory 3, STPType 1, multimode fiber. In the summer of 1996, an 802.3z group was announced to develop a protocol similar to Ethernet as much as possible, but with a bit rate of 1000 Mb / s. As with FastEthernet, the message was received with great enthusiasm by Ethernet proponents. As an alternative to FastEthernet technology, AT&T and HP have come up with a new low-cost 100Mbps technology called 100Base-VG (VoiceGrade is a technology capable of operating on Category 3 cable originally intended for voice transmission). In this project, it was proposed to improve the access method taking into account the needs of multimedia applications, and for the packet format to maintain compatibility with the packet format of 802.3 networks. In September 1993, at the initiative of IBM and HP, the IEEE 802.12 committee was formed to standardize the new technology. The project was expanded by supporting in one network frames not only the Ethernet format, but also the TokenRing format. As a result, the new technology was named 100VG-AnyLAN (Fig. 8), that is, a technology for any networks, where any networks are understood as Ethernet and TokenRing networks. In the summer of 1995, 100VG-AnyLAN technology received the status of the IEEE 802.12 standard. Rice. 8. 100VG-AnyLAN technology. 100VG-AnyLAN technology is less popular with communications equipment manufacturers than competing FastEthernet technology. Companies that do not support 100VG-AnyLAN technology attribute this to the fact that for most of today's applications and networks, the capabilities of FastEthernet technology are sufficient, which is not so noticeably different from the Ethernet technology familiar to most users. In the longer term, these manufacturers suggest using ATM technology, or GigabitEthernet, rather than 100VG-AnyLAN for multimedia applications. Finally, consider a table that compares this technology to Fast Ethernet and GigabitEthernet. Characteristic Topology Maximum net diameter Hub cascading Yes; 3 levels Yes; 5 levels Two hubs maximum Cable system Optical fiber Performance With a network length of 100 m 80% (theoretical) 95% (demonstrated) 80% (theoretical) With a network length of 2500 m 80% (theoretical) 80% (demonstrated) Not supported Technology IEEE 802.3 frames 802.5 frames Access method CSMA / CD + Reconciliationsublayer Tab. 2. Comparative characteristics of Fast Ethernet, GigabitEthernet and 100VG-AnyLAN. Conclusion
So, the relevance of this work is directly related to the ever-increasing role played by corporate computer networks to ensure the effectiveness of management and the successful functioning of a variety of organizations. At the same time, in almost every such network, there is a general tendency to an increase in the number of users, the volume of circulating information, traffic intensity and the associated deterioration in the quality of network services. All this requires experimental studies of network properties, and not only in the online monitoring mode, but also for a deeper study - in particular, in order to predict their behavior. The task of improving the corresponding scientific, methodological and software for analysis and modeling is also connected with this. In the first chapter of the course work, the features of the structure of corporate networks were considered. The structure of corporate networks, as a rule, is geographically distributed, i.e. uniting offices, divisions and other structures located at a considerable distance from each other. Often, corporate network nodes are located in different cities and sometimes countries. The principles by which such a network is built are quite different from those used to create a local network, even covering several buildings. The main difference is that geographically distributed networks use rather slow (today tens and hundreds of kilobits per second, sometimes up to 2 Mbit / s.) Leased communication lines. If, when creating a local network, the main costs are spent on the purchase of equipment and laying cables, then in wide-area networks the most significant cost element is the rent for the use of channels, which grows rapidly with an increase in the quality and speed of data transmission. This limitation is fundamental, and when designing a corporate network, all measures should be taken to minimize the amount of data transferred. The second chapter discusses the need for and the first steps to introduce Intranet technology in corporate enterprise networks. The advantages of this technology, first of all, in the enterprise management system are considered. Some variants of organizational and technical solutions in the field of Intranet are given. At the end of the course work, an overview of the main trends in the development of SPT is carried out and a comparative characteristic of the main technical parameters of promising SPT technologies is carried out. Bibliography 1. Olifer V.G., Olifer N.A. New technologies and equipment for IP networks // SPb .: BHV-Saint Petersburg. 2000 year Samardak A.S. Corporate information systems // Vladivostok. 2003 r. Rassokhin D.N., Lebedev A.I. WorldWideWeb - World Wide Web of the Internet. // Moscow: Faculty of Chemistry, Moscow State University. 1997 year Prosis, D. A TCP / IP Beginner's Guide // PCMagazine. 2000 Semenov Yu.A. Internet protocols and resources // Moscow: Radio and communication. 2002 year Http: //www.lankey.ru Integrated solutions for building enterprise infrastructure. Kutyrkin S.B., Volchkov S.A., Balakhonov I.V. Improving the quality of the enterprise using information systems of the ERP class // Methods of quality management, No. 4, 2000 Krol E. Everything about the Internet: Per. from English // Kiev: Trade and Publishing Bureau BHV, 1998. The concept of a corporate information system. Integrated information technology- unification of various types of information technologies. Currently, there is a tendency to combine various types of information technologies into a single computer-technological complex, which is called integrated .
A special place in it belongs to the means of communication, which provide not only extremely wide technological capabilities for automating various types of activities, but also being the basis for creating various network options for automated information technologies (local, multi-level distributed, global computer networks, e-mail, digital integrated service networks). All of them are focused on the technological interaction of a set of objects formed by devices for transmitting, processing, accumulating, storing and protecting data, and are integrated computer systems for processing data of great complexity with practically unlimited operational capabilities for the implementation of management processes in the economy. Integrated computer technology data processing are designed as a complex information technology and software complex. It supports a unified way of presenting data and user interaction with system components, provides information and computing needs of specialists that arise in the course of their professional work. Integrated computer technologies provided the basis for the implementation of corporate information systems (CIS). The corporate information system or abbreviated KIS is the now generally accepted name and abbreviation of the name of the integrated information management systems. Abroad, such systems are almost called the Management Information System (MIS), the only thing is that there is no adjective “integrated”, which is important here. These systems are the heirs of the integrated automated control systems. Corporate networks are an integral part of corporate information systems. Corporate computer networks. Corporate networks- networks of the scale of an enterprise, corporation. Since these networks typically use the communication capabilities of the Internet, geographic location is irrelevant to them. Corporate networks are classified as a special type of local area networks that have a significant coverage area. Nowadays corporate networks are developing very actively and they are often called Intranets ( Intranet). Intranet (Intranet) - it is a private intra-company or inter-company computer network that has enhanced capabilities due to the use of Internet technologies in it, which has access to the Internet, but is protected from access to its resources by external users. Intranet system can also be defined as a system for storing, transferring, processing and accessing interfirm and intrafirm information using the means of local networks and the Internet. The Intranet is a technology for managing corporate communications, in contrast to the Internet, which is a technology for global communications. Fully functional network Internet should provide, at a minimum, the implementation of such basic network technologies as: ■ network management; ■ a network directory that reflects all other services and resources; ■ network file system; ■ integrated messaging (email, fax, teleconferencing, etc.); ■ work on the World Wide Web; ■ network printing; ■ protection of information from unauthorized access. Intranet network can be isolated from external Internet users using firewalls. Firewall software, usually located on web servers or proxy servers, at least verifies the external subscriber's credentials and knowledge of the password, thereby protecting against unauthorized access to the network and the receipt of confidential information from it. Information on the Internet and all its services are available to all users of the corporate network. In today's highly competitive market, gaining access to the latest information is becoming a critical component of business success. Therefore, the Intranet can now be regarded as the most promising environment for the implementation of corporate applications. The process of developing corporate systems is greatly simplified, since there is no need to develop an integration project. So, individual departments can create their own subsystems using their own LAN, servers, without connecting them with other departments. If necessary, they can be connected to a single enterprise system. The client computer must have a program browser that accesses WWW objects and translates HTML files into a visible image. These files must be available regardless of the user's operating environment. Thus, server applications should be created invariant from clients and their development should be fully focused on implementation. functional tasks corporations and availability one-stop client. Modern management systems for large enterprises have gone from strictly centralized to distributed systems. Information technology providing support for distributed control was built on the basis of systems with a "client-server" architecture. Distributed management was combined with distributed communications, although serious problems arose in the management of distributed databases (ensuring data integrity and consistency, synchronization of updating, protection from unauthorized access), administration of information and computing resources of the network, etc. Building control systems on the principles of Intranet allows you to combine the best qualities of centralized storage systems with distributed communications. The architecture of the Intranet was a natural development of information systems: from systems with a centralized architecture, through client-server systems to the Intranet. The entire information system is located on a central computer. At the workplaces are the simplest access devices (navigators), which provide the ability to control processes in the information system. All processes are carried out on a central computer, with which the access device communicates by means of a simple protocol, by transmitting screens and codes of pressed keys on the remote control. The main advantages of Intranet systems: ■ the server generates information (not data) in a form that is convenient for presentation to the user; ■ an open protocol is used to exchange information between the client and the server; ■ the application system is concentrated on the server; only the navigator is placed on the clients; ■ facilitated centralized management of the server part and workstations; ■ a unified interface that does not depend on the software used by the user (operating system, DBMS, etc.). An important advantage of the Intranet is the openness of the technology. Existing software based on proprietary technologies, when solutions are developed by one company for one application, may seem more functional and convenient, but sharply limit the development of information systems. Currently, the Intranet system widely uses open standards in the following areas: ■ management of network resources (SMTP, IMAP, MIME); ■ teleconferencing (NNTP); ■ information service (НТРР, HTML); ■ reference service (LDAP); ■ programming (Java). Trends for further development of the Intranet: ■ intelligent network search; ■ high interactivity of navigators due to the use of Java technology; ■ network computers; ■ transformation of the navigator interface into a universal interface with a computer. An intranet gives a tangible economic effect in the activities of an organization, which is primarily associated with a sharp improvement in the quality of information consumption and its direct impact on the production process. For the information system of the organization, the key concepts are "information publication", "information consumers", "information presentation". Conclusions: 1. Distributed data processing means that the user and his application programs (applications) are able to work with tools located in dispersed nodes of the network system. 2. Implementation of "client-server" technologies may differ in the efficiency and cost of information and computing processes, as well as in the levels of software and hardware, in the mechanism of component connections, in the efficiency of access to information, its diversity, etc. 3. There is a tendency of further globalization of the worldwide process of informatization of society. The technological basis is the global information superhighway and national information infrastructures of advanced countries, united on the basis of international standards and protocols of information interaction into a qualitatively new information education - the Global Information Infrastructure (GIL). 4. Electronic document flow is a system for manipulating official electronic documents in a standardized form and based on the regulations adopted in the system. 5. The main procedures for managing electronic documents are combined into a group of procedures for creating documents, storing and manipulating documents. 6. Currently, there is a tendency to combine various types of information technologies into a single computer-technological complex, called integrated. 7. Corporate information system or abbreviated KIS is the now generally accepted name and abbreviation of the name of integrated information management systems. 8. The Intranet system (Intranet) is a private intra-company or inter-company computer network that has enhanced capabilities due to the use of Internet technologies in it, which has access to the Internet, but is protected from access to its resources by external users. 9. The Intranet system gives a tangible economic effect in the activities of the organization, which is primarily associated with a sharp improvement in the quality of information consumption and its direct impact on the production process. For the information system of the organization, the key concepts are "information publication", "information consumers", "information presentation".
4.3 100VG-AnyLAN Technology
