network hardware - devices necessary for the operation of a computer network, for example: router, switch, hub, patch panels, etc. Active and passive network equipment can be distinguished.

Active network equipment – hardware followed by some "smart" feature. That is, a router, switch (switch ) etc. are active network equipment.

Passive network equipment – equipment that is not endowed with “intelligent” features. For example - cable system: cable (coaxial and twisted pair (UTP/STP)), plug/socket (RG58, RJ45, RJ11, GG45), repeater (repeater), patch panel, concentrator (hub), balun (balun) for coaxial cables (RG-58), etc. Also, passive equipment includes installation cabinets and racks, telecommunication cabinets.

The main components of the network are workstations, servers, transmission media(cables) and network equipment.

Workstations – network computers on which network users implement applied tasks.

Network servers– hardware and software systems that perform the functions of managing the distribution of network resources public access. A server can be any computer connected to the network that contains resources used by other devices on the local network. Quite powerful computers are used as server hardware.

Networks can be created with any type of cable.

1. Twisted pair (TP- Twisted Pair) is a cable made in the form of a twisted pair of wires. It can be shielded or unshielded. Shielded cable is more resistant to electromagnetic interference. Twisted pair cable is best suited for small institutions. Disadvantages of this cable is a high signal attenuation coefficient and high sensitivity to electromagnetic interference, therefore the maximum distance between active devices on a LAN when using twisted pair cables should be no more than 100 meters.

2. Coaxial cable consists of one solid or twisted central conductor, which is surrounded by a layer of dielectric. A conductive layer of aluminum foil, metal braid, or a combination thereof surrounds the dielectric and simultaneously serves as a shield against interference. The overall insulating layer forms the outer sheath of the cable.

Coaxial cable can be used in two different data transmission systems: without signal modulation and with modulation. In the first case digital signal used as it comes from the PC and is immediately transmitted via cable to the receiving station. It has one transmission channel with a speed of up to 10 Mbit/s and a maximum range of 4000 m. In the second case, the digital signal is converted into analog and sent to the receiving station, where it is again converted into digital. The signal conversion operation is performed by the modem; Each station must have its own modem. This transmission method is multi-channel (provides transmission over dozens of channels using just one cable). In this way, sounds, video signals and other data can be transmitted. The cable length can reach up to 50 km.

3. Fiber optic cable is a newer technology used in networks. The information carrier is a light beam that is modulated by the network and takes the form of a signal. Such a system is resistant to external electrical interference and thus very fast, secure and error-free data transmission is possible at speeds of up to 2 Gbit/s. The number of channels in such cables is huge. Data transfer is carried out only in simplex mode, therefore, to organize data exchange, devices must be connected by two optical fibers (in practice, a fiber optic cable always has an even, paired number of fibers). The disadvantages of fiber optic cable include high cost and complexity of connection.

4. Radio waves in the microwave range are used as a transmission medium in wireless local area networks, or between bridges or gateways for communication between local area networks. In the first case, the maximum distance between stations is 200 - 300 m, in the second - this is the line-of-sight distance. Data transfer speed - up to 2 Mbit/s.

Wireless local networks are considered a promising direction for the development of LANs. Their advantage is simplicity and mobility. Problems associated with laying and installing cable connections also disappear - just install interface cards on workstations, and the network is ready to work.

Kinds network equipment.

1. Network cards are controllers that are plugged into the expansion slots of the computer motherboard, designed to transmit signals to the network and receive signals from the network.

2. Terminators are 50 Ohm resistors that attenuate the signal at the ends of the network segment.

3. Hubs are the central devices of a cable system or a star physical topology network, which, when receiving a packet on one of its ports, forwards it to all the others. The result is a network with a logical common bus structure. There are active and passive concentrators. Active concentrators amplify received signals and transmit them. Passive hubs pass the signal through themselves without amplifying or restoring it.

4. Repeaters are network devices that amplifies and re-forms the shape of the incoming analog network signal over a distance of another segment. A repeater operates at an electrical level to connect two segments. Repeaters do not recognize network addresses and therefore cannot be used to reduce traffic.

5. Switches are software-controlled central devices of the cable system that reduce network traffic due to the fact that the incoming packet is analyzed to determine the address of its recipient and, accordingly, is transmitted only to him.

Using switches is a more expensive but also more productive solution. A switch is usually a much more complex device and can serve multiple requests simultaneously. If for some reason the required port is busy at a given time, the packet is placed in the buffer memory of the switch, where it waits for its turn. Networks built using switches can cover several hundred machines and have a length of several kilometers.

6. Routers - standard network devices that operate at the network level and allow you to forward and route packets from one network to another, as well as filter broadcast messages.

7. Bridges are network devices that connect two separate segments, limited by their physical length, and transmit traffic between them. Bridges also amplify and convert signals for other types of cable. This allows you to expand the maximum network size while still maintaining restrictions on the maximum cable length, number of connected devices, or number of repeaters per network segment.

8. Gateways are software and hardware systems that connect heterogeneous networks or network devices. Gateways allow you to solve problems of differences in protocols or addressing systems. They operate at the session, presentation and application layers of the OSI model.

9. Multiplexers are central office devices that support several hundred digital subscriber lines. Multiplexers send and receive subscriber data via telephone lines, concentrating all traffic in one high-speed channel for transmission to the Internet or to the company’s network.

10. Firewalls (firewalls)– network devices that implement control over information entering and leaving the local network and providing protection to the local network by filtering information. Most firewalls are built on classical access control models, according to which a subject (user, program, process or network packet) is allowed or denied access to any object (file or network node) upon presentation of some unique element inherent only to this subject. In most cases, this element is a password. In other cases, such a unique element is microprocessor cards, biometric characteristics of the user, etc. For a network packet, such an element is addresses or flags located in the packet header, as well as some other parameters.

Introduction

Chapter I Theoretical foundations for building networks

Computer network topology

A ring is a topology in which each computer is connected by communication lines to only two others: from one it only receives information, and to the other it only transmits. The ring topology is shown in Figure 1.

Figure 1 - Ring topology

On each communication line, as in the case of a star, there is only one transmitter and one receiver. This allows you to avoid using external terminators. Work in a ring network is that each computer relays (renews) the signal, that is, acts as a repeater, therefore the attenuation of the signal throughout the ring does not matter, only the attenuation between neighboring computers of the ring is important. In this case, there is no clearly defined center; all computers can be the same. However, quite often a special subscriber is allocated in the ring who manages the exchange or controls the exchange. It is clear that the presence of such a control subscriber reduces the reliability of the network, because its failure will immediately paralyze the entire exchange.

Star - basic topology computer network (Figure 2), in which all computers on the network are connected to a central node (usually a switch), forming a physical segment of the network.

Figure 2 - Star topology

Such a network segment can function either separately or as part of a complex network topology (usually a “tree”). All information exchange takes place exclusively through the central computer, which is subject to a very large load in this way, so it cannot do anything else except the network. As a rule, it is the central computer that is the most powerful, and it is on it that all functions for managing the exchange are assigned. In principle, no conflicts are possible in a network with a star topology, because management is completely centralized.

Bus - is a common cable (called a bus or backbone) to which all workstations are connected. There are terminators at the ends of the cable to prevent signal reflection. The bus topology is shown in Figure 3.

Figure 3 - Bus topology

Network equipment

Network equipment - devices necessary for the operation of a computer network, for example: router, switch, hub, patch panel, etc. Active and passive network equipment can be distinguished.

Active network equipment

This name refers to hardware followed by some “intelligent” feature. That is, a router, switch (switch), flexible multiplexer, etc. are active network equipment. On the contrary, a repeater (repeater)] and a concentrator (hub) are not ASO, since they simply repeat the electrical signal to increase the connection distance or topological branching and do not represent anything “intelligent”. But managed hubs belong to active network equipment, since they can be endowed with some kind of “intelligent feature”

Passive network equipment

Passive equipment differs from active equipment primarily in that it is not powered directly from the mains and transmits the signal without amplification. Passive network equipment means equipment that is not endowed with “intelligent” features. For example, cabling system: cable (coaxial and twisted pair), plug/socket (RG58, RJ45, RJ11, GG45), repeater, patch panel, hub, coaxial cable balun (RG-58), etc. Also, Passive equipment includes mounting cabinets and racks, telecommunication cabinets. Installation cabinets are divided into standard, specialized and vandal-proof. By type of installation: wall, floor and others.

Basic network equipment

Basic network equipment includes:

Server is a dedicated computer. A server is a computer selected from a group of personal computers (or workstations) to perform some service task without direct human intervention. The server and workstation may have the same hardware configuration, since they differ only in the participation of the person at the console in their work.

Some service tasks can be performed on workstation parallel to the user's work. Such a workstation is conventionally called a non-dedicated server.

A console (usually a monitor/keyboard/mouse) and human participation are required for servers only at the initial setup stage, during hardware maintenance and management in emergency situations (normally, most servers are managed remotely). For emergency situations, servers are usually provided with one console kit per group of servers (with or without a switch, such as a KVM switch).

As a result of specialization (see below), the server solution may receive a console in a simplified form (for example, a communication port), or lose it altogether (in this case, initial configuration and non-standard management can only be performed via the network, and network settings can be reset to default state). The server is shown in Figure 4.

Figure 4 - Server

Modem (an acronym made up of the words modulator and demodulator) is a device used in communication systems to physically interface an information signal with its propagation medium, where it cannot exist without adaptation.

The modulator in the modem modulates the carrier signal when transmitting data, that is, changes its characteristics in accordance with changes in the input information signal, the demodulator carries out the reverse process when receiving data from the communication channel. The modem serves as the terminal equipment of the communication line. The very formation of data for transmission and processing of received data is carried out by the so-called. terminal equipment (a personal computer can also play this role).

Modems are widely used to connect computers through a telephone network (telephone modem), cable network (cable modem), radio waves (en:Packet_radio, radio relay communication). Previously, modems were also used in cell phones(have not yet been supplanted by digital methods of data transmission). The modem is shown in Figure 5.

Figure 5 - Modem

Twisted pair is a type of communication cable that consists of one or more pairs of insulated conductors, twisted together (with a small number of turns per unit length), covered with a plastic sheath.

Twisting of conductors is carried out in order to increase the degree of connection between the conductors of one pair (electromagnetic interference equally affects both wires of the pair) and subsequent reduction of electromagnetic interference from external sources, as well as mutual interference during the transmission of differential signals. To reduce the coupling of individual cable pairs (periodic bringing together of conductors of different pairs) in UTP cables of category 5 and higher, the wires of the pairs are twisted with different pitches. Twisted pair is one of the components of modern structured cabling systems. Used in telecommunications and computer networks as a physical signal transmission medium in many technologies such as Ethernet, Arcnet and Token ring. Currently, due to its low cost and ease of installation, it is the most common solution for building wired (cable) local networks.

The cable connects to network devices using an 8P8C connector (mistakenly called RJ45). The twisted pair is shown in Figure 6.

Figure 6 – Twisted pair

A coaxial cable (from the Latin co - together and axis - axis, that is, “coaxial”), also known as coaxial (from the English coaxial), is an electrical cable consisting of a coaxially located central conductor and screen. Typically used to transmit high frequency signals. Invented and patented in 1880 by British physicist Oliver Heaviside. The coaxial cable is shown in Figure 7.

Figure 7 – Coaxial cable

Optical fiber is a thread made of an optically transparent material (glass, plastic) used to transfer light within itself through total internal reflection.

Fiber optics is a branch of applied science and mechanical engineering that describes such fibers. Optical fiber cables are used in fiber optic communications, which allow information to be transmitted over longer distances at higher data rates than electronic communications. In some cases, they are also used to create sensors. The optical fiber is shown in Figure 8.

Currently, this is the most common network conductor, consisting of 8 copper conductors intertwined with each other to reduce electromagnetic interference. The length of a segment of such wire is up to 100 meters (Fig. 1.1).

Rice. 1.1.

The average speed of information in twisted pair is 100 megabits/sec, characteristic impedance- 100 ohm. At higher speeds, information transfer increases sharply signal attenuation(the higher the speed, the greater the attenuation). Thus, at a speed of 100 Mbit/sec (100 MHz), the amplitude drops by a factor of 1000, which is equivalent to a signal attenuation of 67 dB. The signal delay per meter of cable is usually 4-5 nanoseconds. Comparing twisted pair with other cables, it can be noted that it is easy to install, but is susceptible to interference. The cable is relatively cheap, but with low information privacy. It transmits using the point-to-point method (one receiver and one transmitter); star topology is usually used for installing twisted pair cables. Available in several categories. Category 1 – telephone cable (noodles). Used for speech transmission. Category 2 has a speed of up to 1 MHz (1 megabit sec). Category 3 cable has 9 turns per meter, attenuation up to 40 dB and information speed up to 10 megabits sec. Category 4 cable transmits signals up to 20 MHz. Category 5 is the most popular. It has an information speed of up to 100 Mgb sec and uses a twist of 27 turns per meter. Category

6 can transmit a signal with a frequency of up to 500 MHz. Category 7 cable is very expensive - it uses a shield for both individual conductors and a common one. As for cable insulation, gray PVC (non-plenum) insulation is most often used. It is cheap, but burns with the release of poisonous gas. The cable is connected to the network card using an 8P8C connector (Fig. 1.2).

Rice. 1.2.

The wire contains a central conductor made of copper, an insulator layer in copper or aluminum braiding (this is a shield against electromagnetic interference) and external PVC insulation. Maximum transmission speed data - 10 Mbit/sec. The length of a thin coaxial segment is up to 185 meters (Fig. 1.3). This wire has a diameter of about 5 mm.

Rice. 1.3.

The cable is connected to the network card via a BNC (BIEN SI) bayonet-type connector with rotation (Fig. 1.4).

Rice. 1.4.

Compared to twisted pair, coaxial is more expensive, its repair is more difficult, and its flexibility is worse (especially for thick cables). But it has an advantage - the cable braid (copper or aluminum foil) eliminates interference that distorts the signal. Coaxial cable is used, usually in a bus topology, and multipoint signal transmission is used (many receivers and many transmitters).

Fiber optic cable

The cable contains several glass light guides protected by insulation. It has a data transfer rate of several Gbits per second and is not subject to electrical interference. Signal transmission without attenuation goes over a distance measured in kilometers - Fig. 1.5. In a multimode cable, the segment has a length of up to 2 km, and in a single-mode cable – up to 40 km.

Rice. 1.5.

Bits of information are encoded by entities such as strong light, weak light, no light. The signal sources in the cable are an infrared LED or a laser. Optical wire is the most inflexible of all cable signal transmission media, but it is the most noise-resistant, with high information confidentiality. Installation of such a cable is complex and expensive, usually by welding using special equipment. The cable is sometimes armored, i.e. protected with a metal shell (for strength). Optical cable can be single-mode or multimode. In a single-mode cable, the signal is transmitted by an infrared laser with a single wavelength of 1.3 microns, which is suitable for very long-distance signal transmission. In addition to being expensive, high-power lasers are also short-lived. Multimode optical cable is more often used in practice. It uses many 0.85 µm wavelengths and an infrared diode. Since each wave has its own attenuation and refraction, partial distortion of the signal shape occurs and such a cable is used over shorter distances than a single-mode cable. Among other features of an optical cable, it can be noted that the glass can crack from mechanical stress and becomes cloudy from radiation, which, in turn, leads to an increase in signal attenuation in the cable. Teflon (plenum) is usually used to insulate optical fibers. This is expensive (compared to PVC) orange insulation, but it practically does not burn in a fire. The cable connector is usually of the bayonet type (Fig. 1.6). The figure shows an ST type optical connector, which is connected to the cable using the adhesive method, that is, by gluing the optical fiber into the tip, followed by drying and grinding. Connectors for mounting and connecting cords differ in the diameter of the shank (0.9 and 3.0 mm, respectively) and the absence of cable fastening elements in the first ones. Single-mode and multimode connectors differ in the tolerance requirements for the ceramic tip capillary parameters.

LAN equipment can be active or passive. Passive elements include cable, box, switching devices such as cabinets, patch-panel, sockets, patch cords.

Active LAN equipment includes network adapters that perform the function of connecting the user to the LAN, supporting data exchange between the PC and the LAN data transmission medium. In addition, the network adapter acts as a temporary data storage and buffering.

Network cards can be divided into two types: adapters for client computers and adapters for servers. Depending on the Ethernet, Fast Ethernet or Gigabit Ethernet technology used, network cards provide data transfer rates of 10, 100 or 1000 Mbit/s.

Repeater(REPITER) is a repeater device designed to increase the length of a network segment.

Hub(ACTIVE HUBE) is a multiple access device with 4 to 32 ports, used to connect users to a network.

Bridge(BRIDGE) is a device (for example, a computer), with 2 ports, usually used to connect several LAN workgroups, allows you to filter network traffic by parsing network (MAC) addresses.

Switch(SWITCH) - a device with 4-32 ports that divides the overall data transmission medium into logical segments. Each logical segment is connected to a separate switch port to combine multiple LAN workgroups.

Router(ROUTER) - provides a choice of route (for example, a computer) for transferring data between several networks, as well as for combining several LAN workgroups, allows you to filter network traffic by parsing network (IP) addresses.

Media converter- a device, usually with two ports, usually used to convert data transmission media (coaxial-twisted pair, twisted pair-fiber)

Transceiver- signal amplifier, used for bidirectional transmission between the adapter and a network cable or two cable segments. Transceivers are also used as converters for converting electrical signals into other types of signals (optical or radio signals) in order to use other information transmission media.

Gateways- this is communication equipment (for example, a computer) that serves to combine heterogeneous networks with various protocols exchange. Gateways completely transform the entire data flow, including codes, formats, control methods, etc.

Active equipment - bridges, routers and gateways in a local area network use specialized software.

Who installs active equipment?

Installation of active equipment and its configuration are actually different from each other and must be carried out by highly specialized professionals according to a pre-developed project. Only in this case will you be able to do without wasted equipment that is not working correctly. For example, by contacting Russian Engineering Society You will always receive qualified advice, assistance in installing and configuring active equipment and will not be left alone with non-working equipment.

How not to get confused in the growing web of wires?

In the process of development of any enterprise, there is a constant process of changing the number of employees, increasing or reducing divisions, developing branches and remote departments. An enterprise, like a living organism, requires a “circulatory system” free of toxins; as it develops and expands, it involves an increasing number of employees, and the number of various active and executive equipment is growing. There comes a time when the company’s management decides to make further investments in the field of IT infrastructure and should get an excellent predictable result in building a modern network.

Implementation of the "new LAN" project

One of the areas of our activity is carrying out a full range of works on design, modernization, as well as supply and installation of active and passive equipment for creating IT infrastructure in small and medium-sized enterprises, building Data Processing Centers (DPC), creating data storage systems, “ server rooms” equipped with low-current cable systems, uninterruptible power supply systems, monitoring systems and maintaining specified climatic conditions. We also equip these and any other premises with reliable security systems, such as video surveillance, fire alarms, access control and management.

We use ready-made, inexpensive solutions for integration with IT systems. All this allows you to optimize costs and expand the capabilities of existing equipment.

We use proven technologies, equipment and materials from certified manufacturers. We keep construction work on LAN installation to a minimum, focused on the end result, letters of gratitude and recommendations from Customers are the main indicator of our qualifications.

Advantages for the Customer when working with us

	Project department . Our GUI department is the core of all creative endeavors necessary to create a modern, high-quality product. Designers are the first to take an individual approach to each developed object, perform quick and high-quality calculations, detailed elaboration of technical documentation, carry out “designer supervision” and support the adopted engineering solutions.
	Freedom of choice . We are not associated with the supply of any specific equipment; we have our own warehouse and many different suppliers. We install equipment at sites only from those manufacturers whose equipment meets all client requirements for reliability, efficiency, safety and price. The engineering systems we install allow you to reduce your costs at the construction stage, during operation and when expanding the system in the future.
	Full-time specialists. Our engineers and installers working on site work on a permanent basis; we carry out all work from installation to commissioning ourselves, without the help of random installation teams. Our engineers are not sellers of related services and additional work, but trained professionals focused on results.
	Legality. Our activities are legally established; we are always ready to provide you with the necessary permits, approvals, licenses and certificates. The absence of intermediaries allows us to reduce acceptance times technical solutions and ultimately - save your money.
	Service center . Since 2009, we have been providing you with maintenance and repair services for complex modern engineering systems; we have diagnostic equipment, a stationary workshop, and our own warehouse for spare parts and replacement stock. The qualifications of our employees allow us to repair and put into operation almost any security system in the shortest possible time, and the mobility of our teams and the presence of several strongholds allow us to arrive at the site of an urgent repair within 2 hours in Moscow.
	Individual approach for us it is sensitivity to the customer’s expectations, complete mutual understanding, reliability of cooperation, efficiency and achievement of a common goal. We strive for long-term and mutually beneficial cooperation.

Introduction

Assessing the processes of functioning of modern enterprises, it should be noted the trend of increasing use of computer technologies in production, as well as for enterprise management and technological processes. Depending on the nature of production, management can involve from one to hundreds, or even hundreds of thousands, of computers located in space and connected by means of communication into a network.

A local area network (LAN) is a system for information exchange and distributed data processing, covering a small area within enterprises and organizations, focused on the collective use of network resources - hardware (network equipment), software and information.

Basic LAN network equipment: cables with terminal receiving and transmitting equipment; workstations - computers; servers - more powerful computers; network adapters - network cards; modems; concentrators; switches; routers and bridges.

In today's market computer equipment and technology, LAN network equipment, including personal computers, is represented by a great variety of different types, modifications, and developments from competing manufacturers. Equipment of this class is updated continuously, becoming obsolete on average in 5-7 years, which creates an objective need for computer technology specialists and specialists related to computer technology, constantly monitor market fluctuations and conduct an analysis of the composition and characteristics of LAN network equipment at any current moment. The topic is relevant. The above and my personal interest, as the author of the final qualifying work, in fulfilling the technical specifications for the modernization of the existing LAN at the service trade enterprise Torg-Service LLC, where I did my practical training, determined the choice of topic.

The subject of the final qualifying work is local computer network (LAN) equipment.

The object of the study is the composition and characteristics of LAN network equipment.

The purpose of the final qualifying work is to analyze the composition and characteristics of LAN network equipment.

The objectives of the study stem from the stated goal:

Study the scientific literature on the problem under consideration.

Define the structure and functions of the local area network (LAN) model, abstract network model, development of network protocols.

Conduct a review and analysis of the composition and characteristics of network equipment of a local computer network.

Inspect the LAN of Torg-Service LLC and conduct an analysis of network equipment in order to modernize the operation of the network operating at the enterprise within the framework of the technical specifications.

Develop and implement network modernization elements into production.

A local area network is nothing without hardware, network equipment, which is the “support” of the network, without means of communication between the equipment and with the network server. Structured cabling systems, universal data transmission medium in a LAN; server cabinets, connectors, crossover panels are protocol-independent equipment. All other equipment in its design and functions significantly depends on what specific protocol is implemented in them. The main ones are network adapters (NA), concentrators or hubs, bridges and switches as a means of logical structuring of the network, computers.

Research methods in the final qualifying work are analysis of scientific literature, systematization and integration of theoretical knowledge and practical skills.

The work consists of an introduction, three chapters, a conclusion, a list of sources used, the graphic part of the work is presented in the appendices.

1. Analysis of the composition and characteristics of LAN network equipment

.1 Characteristics of the subject area

A local area network (LAN) is a system for information exchange and distributed data processing, covering a small area within enterprises and organizations, focused on the collective use of public resources - hardware, software and information.

The main task solved when creating local computer networks is to ensure compatibility of equipment in terms of electrical and mechanical characteristics and ensure compatibility of information support (programs and data) in terms of coding system and data format. The solution to this problem belongs to the field of standardization and is based on the so-called OSI model (Model of Open System Interconnections). The OSI model was created based on technical proposals from the International Standards Organization (ISO).

The OSI Network Model (OSI), the Open Systems Interconnection Basic Reference Model (1978), is an abstract network model for communications and network protocol development. Offers a measurement perspective on computer networking. Each dimension serves its part of the equipment interaction process. Thanks to this structure, the joint operation of network equipment and software it becomes much simpler and more transparent.

According to the OSI model, the architecture of computer networks should be considered at different levels (the total number of levels is up to seven). The topmost level is applied. At this level the user interacts with the computing system. The lower level is physical. It ensures the exchange of signals between devices. Data exchange in communication systems occurs by moving it from the upper level to the lower one, then transporting it and, finally, playing it back on the client's computer as a result of moving from the lower level to the upper one.

To ensure the necessary compatibility, special standards called protocols operate at each of the seven possible levels of computer network architecture. They determine the nature of the hardware interaction of network components (hardware protocols) and the nature of the interaction of programs and data (software protocols). Physically, protocol support functions are performed by hardware devices (interfaces) and software (protocol support programs). Programs that support protocols are also called protocols.

Each level of the architecture is divided into two parts:

service specification;

protocol specification.

A service specification defines what a layer does, and a protocol specification defines how it does it, and any given layer may have more than one protocol.

Let's look at the functions performed by each layer of software:

The physical layer makes connections to the physical channel, disconnects from the channel, and manages the channel. The data transfer rate and network topology are determined.

The lowest level of the model is intended to directly transmit the data stream. Transmits electrical or optical signals into a cable or radio broadcast and, accordingly, receives them and converts them into data bits in accordance with digital signal encoding methods. In other words, it provides an interface between the network media and the network device.

Parameters defined at this level: type of transmission medium, type of signal modulation, logical levels “0” and “1”, etc.

At this level, signal concentrators (hubs), signal repeaters (repeaters) and media converters operate.

Physical layer functions are implemented on all devices connected to the network. On the computer side, the physical layer functions are performed by the network adapter or serial port. The physical layer refers to the physical, electrical, and mechanical interfaces between two systems. The physical layer defines such types of data transmission media as optical fiber, twisted pair, coaxial cable, satellite channel data transfers, etc. Standard types of network interfaces related to the physical layer are: V.35, RS-232C, RS-485, RJ-11, RJ-45, AUI and BNC connectors.

The data link layer adds auxiliary symbols to the transmitted information arrays and monitors the correctness of the transmitted data. Here the transmitted information is divided into several packets or frames. Each packet contains source and destination addresses, as well as error detection.

The th layer is designed to ensure the interaction of networks at the physical layer and control errors that may occur. It packs the data received from the physical layer into frames, checks for integrity, if necessary, corrects errors (forms a repeated request for a damaged frame) and sends it to the network layer. The data link layer can communicate with one or more physical layers, monitoring and managing this interaction.

The IEEE 802 specification divides this layer into two sublayers - MAC (Media Access Control) regulates access to the shared physical medium, LLC (Logical Link Control) provides network layer service. Switches and bridges operate at this level.

The network layer determines the route for transmitting information between networks, provides error handling, and also manages data flows. The main task of the network layer is data routing (data transfer between networks).

The third layer of the OSI network model is designed to determine the data transmission path. Responsible for translating logical addresses and names into physical ones, determining the shortest routes, switching and routing, monitoring problems and congestion in the network.

Network layer protocols route data from source to destination. The router (router) operates at this level.

The transport layer connects lower layers (physical, data link, network) with upper layers, which are implemented in software. This level separates the means of generating data on the network from the means of transmitting it. Here the information is divided according to a certain length and the destination address is specified.

The th level of the model is designed to ensure reliable data transfer from sender to recipient. However, the level of reliability can vary widely. There are many classes of transport layer protocols, ranging from protocols that provide only basic transport functions (for example, data transfer functions without acknowledgment), to protocols that ensure that multiple data packets are delivered to the destination in the proper sequence, multiplex multiple data streams, provide data flow control mechanism and guarantee the reliability of the received data.

The session layer manages communication sessions between two interacting users, determines the beginning and end of a communication session, the time, duration and mode of a communication session, synchronization points for intermediate control and recovery during data transfer; Restores the connection after errors during a communication session without losing data.

Examples: UDP is limited to monitoring the integrity of data within one datagram, and does not exclude the possibility of losing an entire packet, or duplicating packets, or disrupting the order in which data packets are received. TCP provides reliable continuous data transmission, eliminating data loss or disruption of the order of its arrival or duplication; it can redistribute data, breaking large portions of data into fragments and, conversely, merging fragments into one packet.

Representative level - controls the presentation of data in the form required by the user program, performs data compression and decompression. The task of this level is to convert data when transmitting information into a format that is used in the information system. When receiving data, this data representation layer performs the inverse transformation.

This layer is responsible for protocol conversion and data encoding/decoding. It converts application requests received from the application layer into a format for transmission over the network, and converts data received from the network into a format understandable to applications. This layer can perform compression/decompression or encoding/decoding of data, as well as redirecting requests to another network resource if they cannot be processed locally.

Layer 6 (presentations) of the OSI reference model is typically an intermediate protocol for converting information from neighboring layers. This allows communication between applications on disparate computer systems in a manner transparent to the applications. The presentation layer provides code formatting and transformation. Code formatting is used to ensure that the application receives information to process that makes sense to it. If necessary, this layer can perform translation from one data format to another.

The presentation layer not only deals with the formats and presentation of data, it also deals with the data structures that are used by programs. Thus, layer 6 provides organization of data as it is sent.

The application layer interacts with application network programs that serve files, and also performs computational, information retrieval work, logical transformations of information, transmission of mail messages, etc. The main task of this level is to provide a convenient interface for the user.

The top level of the model ensures the interaction of user applications with the network. This layer allows applications to use network services such as:

remote access to files and databases

forwarding email.

From the above we can conclude:

At different levels, different units of information are exchanged: bits, frames, packets, session messages, user messages.

1.2 Composition and purpose of network equipment as an object of study

The main LAN equipment is cables with terminal receiving and transmitting equipment, network adapters, modems, hubs, switches, routers, bridges, workstations (PC), servers. The simplest example of network equipment is a modem, or modulator-demodulator. The modem is designed to receive an analog signal from the telephone line, which is processed (by the modem itself) and transmitted to the computer in the form of information that the computer understands. The computer processes the received information and, as necessary, displays the result on the monitor screen. Usually there are active and passive network equipment.

Active hardware means hardware followed by some "intelligent" feature. That is, a router, switch (switch), etc. are active network equipment (ANE). On the contrary, a repeater (repeater) and a concentrator (hub) are not ASO, since they simply repeat the electrical signal to increase the connection distance or topological branching and do not represent anything “intelligent”. But managed switches belong to active network equipment, since they can be endowed with some kind of “intelligent feature”.

Passive network equipment means equipment that is not endowed with “intelligent” features. For example - cable system: cable (coaxial and twisted pair (UTP/STP)), plug/socket (RG58, RJ45, RJ11, GG45), repeater (repeater), patch panel, hub (hub), balun (balun) for coaxial cables (RG-58), etc. Also, passive equipment includes mounting cabinets and racks, telecommunication cabinets. Installation cabinets are divided into: standard, specialized and vandal-proof. By type of installation: wall and floor and others.

The most important network equipment that allows you to transfer data over a transmission medium is network adapters, or network cards (network cards). There are different network adapters for different types of networks. That's why they are adapters, that is, data transmission equipment adapted to a particular transmission medium.

Network card, also known as network card, network adapter, Ethernet adapter, NIC (network interface controller) - peripheral device, allowing the computer to communicate with other devices on the network. Currently, network cards are integrated into motherboards for convenience and to reduce the cost of the entire computer as a whole.

Based on their design, network cards are divided into:

internal - separate cards inserted into a PCI, ISA or PCI-E slot;

external, connected via USB or PCMCIA interface, mainly used in laptops;

built in motherboard.

On 10-megabit network cards, 3 types of connectors are used to connect to the local network:

8P8C for twisted pair;

BNC - connector for thin coaxial cable;

15-pin transceiver connector for thick coaxial cable.

These connectors can be present in different combinations, sometimes even all three at once, but only one of them is working at any given time.

One or more information LEDs are installed next to the twisted pair connector, indicating the presence of a connection and the transfer of information.

One of the first mass-produced network cards was the NE1000/NE2000 series from Novell, and in the late 1980s there were many Soviet clones of network cards with a BNC connector, which were produced with various Soviet computers and separately.

The network adapter (Network Interface Card (or Controller), NIC) together with its driver implements the second, channel level of the open systems model in the final node of the network - the computer. More precisely, in a network operating system, the adapter and driver pair performs only the functions of the physical and MAC layers, while the LLC layer is usually implemented by an operating system module that is common to all drivers and network adapters. Actually, this is how it should be in accordance with the IEEE 802 protocol stack model. For example, in Windows NT, the LLC level is implemented in the NDIS module, common to all network adapter drivers, regardless of what technology the driver supports.

The network adapter together with the driver performs two operations: frame transmission and reception. Transmitting a frame from a computer to a cable consists of the following steps (some may be missing, depending on the encoding methods adopted):

Receiving an LLC data frame through the cross-layer interface along with MAC layer address information. Typically, communication between protocols within a computer occurs through buffers located in RAM. Data to be transmitted to the network is placed in these buffers by upper-layer protocols, which retrieve it from disk memory or from the file cache memory using the I/O subsystem of the operating system.

Formatting the MAC data frame - the layer into which the LLC frame is encapsulated (with the 01111110 flags discarded), filling in the destination and source addresses, calculating the checksum.

Formation of code symbols when using redundant codes of type 4B/5B. Scrambling codes to obtain a more uniform spectrum of signals. This stage is not used in all protocols - for example, 10 Mbit/s Ethernet technology does without it.

Output of signals into the cable in accordance with the accepted linear code - Manchester, NRZ1. MLT-3, etc.

Receiving a frame from a cable to a computer involves the following steps:

Receiving signals from the cable that encode the bit stream.

Isolating signals from noise. This operation can be performed by various specialized chips or DSP signal processors. As a result, a certain bit sequence is formed in the adapter receiver, which with a high degree of probability coincides with the one sent by the transmitter.

If the data was scrambled before being sent to the cable, it is passed through a descrambler, after which the code symbols sent by the transmitter are restored in the adapter.

Checking the frame checksum. If it is incorrect, the frame is discarded, and the corresponding error code is sent to the LLC protocol through the inter-layer interface to the top. If the checksum is correct, then an LLC frame is extracted from the MAC frame and transmitted through the interlayer interface upward to the LLC protocol. The LLC frame is placed in a RAM buffer.

As an example of adapter classification, we use the 3Com approach. 3Com believes that Ethernet network adapters have gone through three generations of development.

First-generation network adapters use a multi-frame buffering method. In this case, the next frame is loaded from the computer memory into the adapter buffer simultaneously with the transfer of the previous frame to the network. In receive mode, after the adapter has fully received one frame, it can begin transmitting this frame from the buffer to the computer memory simultaneously with receiving another frame from the network.

Second-generation network adapters widely use highly integrated circuits, which increases the reliability of the adapters. Additionally, the drivers for these adapters are based on standard specifications. Second-generation adapters typically come with drivers that run on both the NDIS (Network Driver Interface Specification) standard developed by 3Com and Microsoft and approved by IBM, and the ODI (Open Driver Interface) standard developed by Novell.

In third-generation network adapters (3Com includes its adapters of the EtherLink III family), a pipeline frame processing scheme is implemented. It lies in the fact that the processes of receiving a frame from the computer’s RAM and transmitting it to the network are combined in time. Thus, after receiving the first few bytes of the frame, their transmission begins. This significantly (by 25-55%) increases the performance of the “RAM - adapter - physical channel - adapter - RAM” chain. This scheme is very sensitive to the transmission start threshold, that is, to the number of frame bytes that are loaded into the adapter buffer before transmission to the network begins. The third generation network adapter performs self-tuning of this parameter by analyzing the operating environment, as well as by calculation, without the participation of the network administrator. Bootstrapping provides the best possible performance for a particular combination of the performance of the computer's internal bus, its interrupt system, and its DMA system.

Third-generation adapters are based on application-specific integrated circuits (ASICs), which improves adapter performance and reliability while reducing its cost. 3Com called its frame pipeline technology Parallel Tasking, and other companies have also implemented similar schemes in their adapters. Increasing the performance of the adapter-memory channel is very important for improving the performance of the network as a whole, since the performance of a complex frame processing route, including, for example, hubs, switches, routers, global communication links, etc., is always determined by the performance of the slowest element this route. Therefore, if the network adapter of the server or client computer is slow, no fast switches will be able to improve the network speed.

Network adapters produced today can be classified as fourth generation. Modern adapters necessarily include an ASIC that performs the functions of the MAC level (MAC-PHY), the speed is up to 1 Gbit/s, and there are also a large number of high-level functions. Such features may include support for the RMON remote monitoring agent, a frame priority scheme, remote computer control functions, etc. In server versions of adapters, it is almost necessary to have a powerful processor that offloads the central processor. An example of a fourth generation network adapter is the 3Com Fast EtherLink XL 10/100 adapter.

A cable is an element for transmitting an electronic signal through wires. Any cable consists of metal cores (wires) that conduct electric current. A wire is a kind of transmission medium for an electronic signal. When installing the cable, proper cable routing techniques must be followed. The cable should not be bent at an acute angle (it would be better to have a rounded angle) to reduce the likelihood of microdamage. Network equipment is very sensitive to such damage. Do not bend or unbend the cable repeatedly. This also leads to disruption of its microstructure and, as a result, the data transfer speed will be lower than usual, and the network will fail more often.

In computer stores you can find cables that are initially designed for short distances.

When installing wireless networks, only the presence on the computer of a PCI or PCMCIA slot on laptops, or a USB connector, where the network adapter itself is connected, is taken into account. The fact is that the data transmission medium for wireless networks is radio communication. There is no need to run wires anymore.

Connectors, or as they are often called ports, used in creating fixed cable computer networks today come in three types: RJ-11 connector, RJ-45 connector and BNC connector.

The RJ-11 connector is better known as a telephone connector. A cable for this standard consists of four wires. Such connectors are used on telephone analog or digital ADSL modems. In the standard version, the RJ-11 connector uses only two wires: those in the middle.

The RJ-45 connector is a standard, widely used network connector used in modern network adapters and similar equipment, and has eight pins. Its presence on the motherboard indicates that a network card is integrated into the motherboard. A user who has the ability to connect to a computer local network will not have much difficulty connecting to it through this port.

And finally, the BNC connector is practically not used at present. Appeared in the 70s, when computer networks were just being created. It can be found on TVs, as this connector is used to connect the antenna cable to the TV. It was on such cables that computer networks were previously built. Nowadays there are practically no such networks. However, cable is widely used in everyday life when connecting an antenna to a TV and in broadcasting equipment, as well as when creating wireless computer networks (also for connecting an antenna).

Such equipment includes such elements of network equipment as routers, satellite dish decoders and modems.

Router or router - network device, based on information about the network topology and certain rules, making decisions about forwarding network layer packets (layer 3 of the OSI model) between different network segments.

Typically, a router uses the destination address specified in the data packets and determines from the routing table the path along which the data should be sent. If there is no described route in the routing table for an address, the packet is discarded.

There are other ways to determine the forwarding route of packets, such as using the source address, the upper-layer protocols used, and other information contained in the network layer packet headers. Often, routers can translate the addresses of the sender and recipient, filter the transit data stream based on certain rules to limit access, encrypt/decrypt the transmitted data, etc.

Routers help reduce network congestion by dividing the network into collision domains or broadcast domains, and by filtering packets. They are mainly used to connect networks different types, often incompatible in architecture and protocols, for example, to combine Ethernet local networks and WAN connections using xDSL, PPP, ATM, Frame relay, etc. protocols. A router is often used to provide access from a local network to a global network. The Internet performs the functions of address translation and firewall.

A router can be either a specialized (hardware) device or a regular computer that performs the functions of a router. There are several software packages (mostly based on the Linux kernel) that can turn your PC into a high-performance, feature-rich router, such as Quagga.

To connect cables, connectors, plugs and network equipment together, the tools that are essential for any system administrator. Naturally, there may be more tools, but in our case we will consider only the most basic ones, without which it is impossible for any system administrator to work.

When creating large computer networks for any institution, it is necessary that the system administrator be aware of the latest prices for network equipment; this is important in the event that it will be necessary to provide preliminary calculations for the equipment purchased for the network. The administrator should not worry about prices for equipment and other goods; he takes on the role of a person who will be exclusively involved in creating the computer network itself.

So, the system administrator's toolkit includes: RJ-45 pliers, a utility knife, a set of RJ-45 jacks, a dialer (digital device), a patch cord 1.0 - 1.5 meters long, a set of bolts for installing equipment in system case, universal screwdriver, calculator. And now, in order, about each element separately.

RJ-45 clamps: used for crimping twisted pair cables; their presence is required if you are going to install a network.

To build a simple local network, it is enough to have network adapters and a cable of the appropriate type. But even in this case, additional devices are needed, for example, signal repeaters, to overcome the restrictions on the maximum length of the cable segment.

The main function of a repeater is to repeat signals received on one of its ports on all other ports (Ethernet) or on the next port in a logical ring (Token Ring, FDDI) synchronously with the original signals. The repeater improves the electrical characteristics of the signals and their synchronization, and as a result, it becomes possible to increase the distance between the most remote stations in the network.

A multiport repeater is often called a hub (hub, concentrator) because this device implements not only the signal repetition function, but also concentrates the functions of connecting computers into a network in one device. In almost all modern network standards, a hub is a mandatory network element that connects individual nodes into a network.

The sections of cable that connect two computers or any two other network devices are called physical segments. Consequently, hubs and repeaters are a means of physically structuring the network.

A network hub or hub (jarg from the English hub - activity center) is a network device designed to combine several Ethernet devices into a common network segment. Devices are connected using twisted pair, coaxial cable or optical fiber. The term hub (hub) is also applicable to other data transfer technologies: USB, FireWire, etc.

The hub operates at the physical layer of the OSI network model and repeats the signal arriving at one port to all active ports. If a signal arrives on two or more ports at the same time, a collision occurs and the transmitted data frames are lost. Thus, all devices connected to the hub are in the same collision domain. Hubs always operate in half-duplex mode, where all connected Ethernet devices share the available access bandwidth.

Many hub models have simple protection against excessive collisions that occur due to one of the connected devices. In this case, they can isolate the port from the general transmission medium. Network segments based on twisted pair are much more stable than segments on a coaxial cable, since in the first case each device can be isolated from the general environment by a hub, and in the second case, several devices are connected using one cable segment, and, in the case of a large number collisions, the hub can isolate only the entire segment.

Recently, hubs have been used quite rarely; instead, switches have become widespread - devices that operate at the link level of the OSI model and increase network performance by logically separating each connected device into a separate segment, a collision domain.

Let us denote the following characteristics of network hubs:

The number of ports - connectors for connecting network lines; hubs with 4, 5, 6, 8, 16, 24 and 48 ports are usually produced (the most popular are those with 4, 8 and 16). Hubs with more ports are significantly more expensive. However, hubs can be connected in cascade to each other, increasing the number of ports on a network segment. Some have special ports for this.

Data transfer speed - measured in Mbit/s, hubs are available with speeds of 10, 100 and 1000. In addition, hubs with the ability to change speed are mostly common, designated as 10/100/1000 Mbit/s. The speed can be switched either automatically or using jumpers or switches. Typically, if at least one device is connected to the hub at a low-band speed, it will transmit data to all ports at that speed.

The type of network media is usually twisted pair or optical fiber, but there are hubs for other media, as well as mixed ones, for example, for twisted pair and coaxial cable.

Workstations (PCs) are formed on a LAN based on personal computers (PCs) and are used to solve applied problems, issue requests to the network for services, receive the results of satisfying requests, and exchange information with other workstations. The core of the PC is the PC, on which the configuration of the workstation depends.

Network servers are hardware and software systems that perform the functions of managing the distribution of public network resources, but can also work like ordinary computers.

The server is created on the basis of a powerful computer, much more powerful than workstation computers.

A LCS may have several different servers for managing network resources, but there is always one (or several) file server (server without data) for managing external storage devices (SSDs) for general access and organization distributed databases data. In conclusion, it should be noted that in a LAN, an important role in organizing the interaction of the network equipment described above belongs to the link layer protocol, which is focused on a very specific network topology.

1.3 Technologies and protocols for interaction of LAN hardware

When organizing the interaction of LAN network equipment, an important role is played by the link layer protocol.

However, in order for the link layer to cope with this task, the structure of the LAN must be quite specific, for example, the most popular link layer protocol - Ethernet - is designed for parallel connection of all network nodes to a common bus for them - a piece of coaxial cable. . The Token Ring protocol is also designed for a very specific configuration of connections between computers - a connection in a ring. Ring and IEEE 802.5 are prime examples of token-passing networks. Token passing networks move a small block of data called a token along the network. Possession of this token guarantees the right to transfer. If the node receiving the token does not have information to send, it simply forwards the token to the next endpoint. Each station can hold a marker for a certain maximum time (default is 10ms).

The technology was originally developed by IBM in 1984. In 1985, the IEEE 802 committee adopted the IEEE 802.5 standard based on this technology. Recently, even IBM products have been dominated by the Ethernet family of technologies, despite the fact that previously for a long time the company used Token Ring as the main technology for building local networks.

Basically, the technologies are similar, but there are minor differences. IBM's Token Ring describes a "star" topology, where all computers are connected to one central device (multistation access unit (MSAU)), while IEEE 802.5 does not focus on topology. Appendix B shows the differences between the technologies. ring - Token ring local area network (LAN) technology - a local area network protocol that resides at the Data Link Layer (DLL) of the OSI model. . It uses a special three-byte frame called a token that moves around the ring. Possession of a token gives the owner the right to transmit information on the medium. Token ring frames travel in a loop.

Stations on a local area network (LAN) Token ring are logically organized in a ring topology with data transferred sequentially from one ring station to another with a control token circulating around the control access ring. This token passing mechanism is shared by ARCNET, the token bus, and FDDI, and has theoretical advantages over stochastic CSMA/CD Ethernet.

This technology offers a solution to the problem of collisions that arise when operating a local network. In Ethernet technology, such collisions occur when information is simultaneously transmitted by several workstations located within the same segment, that is, using a common physical data channel.

If the station that owns the token has information to transmit, it grabs the token, changes one bit of it (resulting in the token becoming a "beginning of data block" sequence), completes it with the information it wants to transmit, and sends that information to the next one. ring network stations. When a block of information circulates around the ring, there is no token on the network (unless the ring provides early token release), so other stations wishing to transmit information are forced to wait. Therefore, there can be no collisions in Token Ring networks. If early token release is ensured, then a new token can be released after the data block transmission is completed.

The information block circulates around the ring until it reaches the intended destination station, which copies the information for further processing. The information block continues to circulate around the ring; it is permanently deleted after reaching the station that sent the block. The sending station can check the returned block to ensure that it was viewed and then copied by the destination station.

Unlike CSMA/CD networks (such as Ethernet), token-passing networks are deterministic networks. This means that we can calculate maximum time which will pass before any end station can transmit. This characteristic, as well as some reliability characteristics, make the Token Ring network ideal for applications where latency must be predictable and network stability is important. Examples of such applications are the environment of automated stations in factories. It is used as a cheaper technology and has become widespread wherever there are critical applications for which it is not so much speed that is important as reliable delivery of information. Currently, Ethernet is not inferior to Token Ring in reliability and is significantly higher in performance.

In the last few years, there has been a movement towards abandoning the use of shared data transmission media in local networks and a transition to the mandatory use of active switches between stations, to which end nodes are connected by individual communication lines. In its pure form, this approach is offered in ATM (Asynchronous Transfer Mode) technology, and a mixed approach, combining shared and individual data transmission media, is used in technologies bearing traditional names with the switching prefix (switching): switching Ethernet, switching Token Ring, switching FDDI .

But, despite the emergence of new technologies, the classic protocols of local Ethernet networks and Token Ring, according to experts, will be widely used for at least another 5 - 10 years, and therefore, knowledge of their details is necessary for the successful use of modern communication equipment. (Fiber Distributed Data Interface) - Fiber-optic interface for distributed data - a standard for data transmission in a local network stretched over a distance of up to 200 kilometers. The standard is based on the Token Ring protocol. In addition to its large area, the FDDI network is capable of supporting several thousand users.

It is recommended to use fiber optic cable as the data transmission medium for FDDI, but copper cable can also be used, in which case the abbreviation CDDI (Copper Distributed Data Interface) is used. The topology is a double ring scheme, with data circulating in the rings in different directions. One ring is considered the main one; information is transmitted through it in the normal state; the second is auxiliary; data is transmitted through it in the event of a break on the first ring. To control the state of the ring, a network token is used, as in Token Ring technology.

Since such duplication increases the reliability of the system, this standard is successfully used in trunk communication channels.

The standard was developed in the mid-80s by the National American Standards Institute (ANSI) and received the number ANSI X3T9.5.Ethernet (IEEE802.3u, 100BASE-X) - a set of standards for data transmission in computer networks, with speeds up to 100 Mbit/s , unlike regular Ethernet (10 Mbit/s).

Fast Ethernet technology is an evolutionary development of classic Ethernet technology.

The main advantages of Fast Ethernet technology are:

increasing the capacity of network segments up to 100 Mb/s;

maintaining a star-shaped network topology and supporting traditional data transmission media - twisted pair and fiber optic cable.

Options for implementing Ethernet technology are as follows (Appendix B):

BASE-T - any of the 100 Mbit Fast Ethernet standards for twisted pair:

BASE-TX - using two pairs of category 5 cable conductors or shielded twisted pair STP Type 1;

BASE-T4 - over a four-pair Cat3 cable (and higher) in half-duplex mode; no longer in use;

BASE-T2 - over two pairs of Cat3 cable; no longer used.

100BASE-T cable segment length is limited to 100 meters (328 feet). In a typical configuration, 100BASE-TX uses one pair of stranded wires in each direction to transmit data, providing up to 100 Mbps of throughput in each direction (duplex).

BASE-FX is a variant of Fast Ethernet using fiber optic cable. This standard uses the long-wave part of the spectrum (1300 nm) transmitted over two wires, one for reception (RX) and one for transmission (TX). Network segment lengths can be up to 400 meters (1,310 feet) in half-duplex mode (with collision detection guaranteed) and two kilometers (6,600 feet) in full-duplex mode using multimode fiber. Long distance operation is possible using single-mode fiber. 100BASE-FX is not compatible with the 10BASE-FL, 10 Mbps fiber option.

BASE-SX is a low-cost alternative to 100BASE-FX using multimode fiber, as it uses cheaper shortwave optics. 100BASE-SX can operate over distances up to 300 meters (980 feet). 100BASE-SX uses the same wavelength as 10BASE-FL. Unlike 100BASE-FX, this allows 100BASE-SX to be backwards compatible with 10BASE-FL. Thanks to its use of shorter wavelengths (850 nm) and the short range over which it can operate, 100BASE-SX uses less expensive optical components (light emitting diodes (LEDs) instead of lasers). All this makes this standard attractive for those who are upgrading a 10BASE-FL network and those who do not need to work over long distances.

BASE-BX is a variant of Fast Ethernet over single-core fiber, using single-mode fiber, along with a special multiplexer that splits the signal into transmitting and receiving waves.

BASE-LX - 100 Mbps Ethernet option using optical cable. Maximum length segment 15 kilometers in full duplex mode over a pair of single-mode optical fibers.

BASE-LX WDM - 100 Mbps Ethernet option using fiber optic cable. The maximum segment length is 15 kilometers in full duplex mode over one single-mode optical fiber at a wavelength of 1310 nm and 1550 nm. Interfaces come in two types, differ in the wavelength of the transmitter and are marked either with numbers (wavelength) or with one Latin letter A (1310) or B (1550). Only paired interfaces can operate in pairs: on one side there is a transmitter at 1310 nm, and on the other at 1550 nm.

ATM technology has many attractive properties - scalable data transfer speeds up to 10 Gb/s; excellent support for multimedia traffic and the ability to work in both local and global networks. .(Asynchronous Transfer Mode) - an asynchronous method of data transfer - a high-performance network switching and multiplexing technology based on data transfer in the form of cells of a fixed size (53 bytes), of which 5 bytes are used for the header. Unlike the synchronous data transfer method (STM - Synchronous Transfer Mode), ATM is better suited to provide data transfer services with widely varying or varying bitrates.

The network is built on the basis of an ATM switch and an ATM router. The technology is implemented both in local and global networks. The joint transmission of various types of information, including video and voice, is allowed.

The data cells used in ATM are smaller compared to the data cells used in other technologies. The small, constant cell size used in ATM allows:

transmit data over the same physical channels, both at low and high speeds;

work with constant and variable data streams;

integrate any types of information: texts, speech, images, videos;

support point-to-point, point-to-many, and many-to-many connections.

ATM technology involves internetworking at three levels.

To transfer data from the sender to the recipient in the ATM network, virtual channels VC (Virtual Circuit) are created, which come in two types:

a permanent virtual channel, PVC (Permanent Virtual Circuit), which is created between two points and exists for a long time, even in the absence of data to transmit;

switched virtual channel, SVC (Switched Virtual Circuit), which is created between two points immediately before data transmission and is broken after the end of the communication session.

For routing in packets, so-called packet identifiers are used. They come in two types:

VPI (virtual path identificator) - virtual path identifier (channel number)

VCI (virtual connect identificator) - virtual connection identifier (connection number).

The results of comparison of FDDI technology with Fast Ethernet and Token Ring technologies are presented in Appendix B.

All stations in the FDDI network are divided into several types according to the following criteria: end stations or hubs; according to the option of connecting to the primary and secondary rings; by the number of MAC nodes and, accordingly, MAC addresses per station.

If the station is connected only to the primary ring, then this option is called a single attachment - Single Attachment, SA. If the station is connected to both the primary and secondary rings, then this option is called Dual Attachment, DA.

Obviously, a station can only take advantage of the fault tolerance properties provided by having two FDDI rings when it is connected twice. As can be seen from Figure 1, the reaction of stations to a cable break is to change the internal paths of information transmission between the individual components of the station. A virtual network is a group of network nodes whose traffic, including broadcast traffic, is completely isolated at the data link level from other network nodes. This means that frames cannot be transmitted between different virtual segments based on a link-layer address, regardless of the type of address - unique, multicast, or broadcast. At the same time, within a virtual network, frames are transmitted using switching technology, that is, only to the port that is associated with the frame's destination address.

Figure 1 - Reconfiguration of dual-connection stations in the event of a cable break

When using virtual network technology in switches, two tasks are simultaneously solved:

increased performance in each of the virtual networks, since the switch transmits frames in such a network only to the destination node;

Isolating networks from each other to manage user access rights and create protective barriers against broadcast storms.

Connecting virtual networks to the Internet requires the involvement of the network layer. It can be implemented in a separate router, or it can also work as part of the switch software.

There are several ways to build virtual networks:

Grouping of ports;

Grouping of MAC addresses;

Use of tags in the additional field of the frame - proprietary protocols and specifications IEEE 802.1 Q/p;

LANE specification for ATM switches;

Using the network layer;

VLAN based on port grouping.

The study and analysis of scientific and technical literature in the subject area of ​​the final qualifying work showed that: the need to meet the growing requirements of production workers for local computer networks contributes to dynamic change purpose, composition, structure, methods of network organization. This, in turn, requires the development and implementation of new and increasingly advanced types of network hardware, as well as the dynamic development of technology and protocols for the interaction of equipment used in the creation of computer networks.

I, as the author of the final qualifying work, completed an internship at the service trade enterprise Torg-Service LLC. Working as an engineer on duty for servicing technical equipment of the local network, which has been operating at the enterprise since 2006, he studied the advantages and disadvantages of the existing equipment, and had the opportunity to implement his knowledge in the development and implementation of the “Terms of Reference” received from the enterprise for the implementation of the technical part of the modernization project of the local computer operating at the enterprise. networks" (Appendix I).

2. Inspection and analysis of the LAN of Torg-Service LLC in order to modernize the network

Torg-Service LLC is a private enterprise, which includes 4 production departments and an administrative and economic department with accounting.

The company, in order to make a profit, is engaged in the production and adaptation of media materials, advertising audio clips; develops software products for broadcasting companies, advertising performances, concerts, etc., based on user requests; sale of mortgages and components for computers, as well as consumables; PC sales and service.

A distributed local area network was developed and implemented by such a multifunctional enterprise in 2006.

Over the past 5 years, the current LAN has become outdated, and does not suit the performers and management of the organization for the following reasons: poor performance of the network server and workstations; rigid structure and functions of the equipment included in the LAN; outdated network protocols.

For this objective reason, there was a need to modernize the local computer network (LAN) operating at the enterprise.

The modernization project for the existing LAN at the enterprise is carried out with the aim of:

inclusion, in addition to the existing one, of new technological equipment for diagnostics and testing of embedded and computer components, testing of PC performance;

replacing the system and basic software of the server with a modern, more powerful one;

connecting three mobile workstations to the central LAN server.

At the same time, provide employees of the enterprise, according to their qualifications and positions, with prompt and high-quality access to LAN resources and to the resources of the global INTERNET network. It is necessary that individual time for using LAN and INTERNET resources is automatically taken into account.

Types and volumes of work to be performed.

Conduct a survey of the enterprise's existing LAN in order to audit network equipment, protocol operation, organization and maintenance of databases, as well as server operation.

Draw up a diagram of the equipment proposed for implementation of the modernized network, include three mobile workstations in the diagram.

Ensure the selection and installation of a modern operating system, administration programs and modern communication protocols for network equipment on the central LAN server.

Conduct trial operation of the enterprise's modernized LAN.

2.1 Structure of the enterprise and the existing LAN

An examination of the LAN of the service trading enterprise Torg-Service LLC was carried out within the framework of the “Terms of reference for the implementation of the technical part of the project for modernizing the local computer network operating at the enterprise” (Appendix I), which allowed us to draw the following conclusions:

The company currently consists of 4 production departments and an administrative department, which includes accounting and a garage. The company is located in one building and on one floor.

The functions and tasks of the departments are as follows:

production department (production) - is engaged in the production and adaptation of media materials, the sale of advertising audio clips;

commercial department - deals with sales and purchases of components, PCs, customer service, accounting, statistics;

technical department - ensures the operation of the LAN, maintains all hardware and software;

service center - works with the public, accepts PCs for repair, checks components and PCs for the commercial department;

Management is currently planning to expand its activities

enterprises, namely a list of services provided to the population, in order to ensure self-sufficiency of the service center. The department purchased modern Antec P183 equipment for testing and diagnosing computer components and embedded parts, diagnosing the operation of personal computers purchased for commercial purposes by the enterprise and accepted from the public for repair or sale.

The block diagram of the LAN operating at the enterprise is presented in Figure D.1. (Appendix D).

The structure of the network, running the Windows Server 2003 network operating system, uniting 20 computers, corresponds to the structure of information flows. Depending on the network traffic, computers on the network are divided into groups (network segments). In this case, computers are combined into a group according to the principle: if most of the messages generated by them are addressed to computers in this group.

Various link layer protocols for the formation of a unified transport system belong to the 2nd generation, i.e. ensure the transfer of information between end nodes.

Packets are routed in the network according to the star topology.

Access rights to information are determined individually for employees of each department. Some of the information is publicly available, while some should only be available to users in a specific department.

All network users have access to both the internal information resources of the organization and the resources of the global Internet. Moreover, in this case, access rights are also assigned individually to employees of each department, depending on the functions assigned to them in the course of the company’s business activities. For example, some employees should have access to all services and resources on the Internet, and some should have access only to e-mail, for example, using only a certain set of available protocols for these purposes.

Recording the work time of a specific performer and a specific department on the network and with the INTERNET is difficult, because all the time goes to the enterprise and is not automatically taken into account to whom exactly and when the information is provided. And this is a violation of the confidentiality of information and the waste of time on work on the INTERNET that is not justified by production needs.

There is no need to divide the network into virtual segments; the network is built without using VLAN technology. The traffic movement is transparent for all departments; the differentiation of access rights to information resources is ensured by software at the level Active Directory(Windows 2003 Server Directory Services)

Based on an examination of the existing LAN at the enterprise and in pursuance of the technical specifications, I, as the author of the final qualifying work, determined the range of tasks that must be further solved in the final qualifying work:

Include into the existing LAN structure the equipment newly received by the service center and a second dedicated server to manage the work of the service center. Organization of network services (services): DNS, Active Directory, DHCP, DNS, File Server, Terminal Server;

Organize uninterrupted power supply to active network equipment,

servers, using a distributed system uninterruptible power supply. The battery life must be at least 7 minutes.

In addition to the standard configuration, the main communications center's uninterruptible power supplies must support the following additional features:

Provide UPS management via the network via SNMP/Telnet/HTTP (using any Web browser); regular shutdown of each server connected to the UPS in the event of a complete battery discharge.

The upgraded network must still support the interaction of 20 personal computers. The cable infrastructure is built on the basis of one main communication center.

The network must provide: file storage and management, network printing; email, optimal teamwork with information (databases); server file backup; backup of network application files (email storage, databases).

The entire network requires one main communication center.

Use 3Com products as active network equipment, and the bandwidth of the communication channel with workstations must be at least 100 Mbit/s; this bandwidth must be allocated for each workstation (switched network).

The backbone must provide a throughput of at least 33% of the maximum traffic of the communication center.

It is necessary to ensure management, monitoring, and collection of statistics from active network equipment. The equipment must be controlled only in the main communications center.

Means for effectively managing internal network traffic are not required; to manage external Internet traffic, it is necessary to implement a system on the Traffic Inspector software platform.

To increase the level of network fault tolerance, it is necessary to provide redundant power supplies for active network equipment devices of the main communication center.

Provide a structured cabling system; for communication with servers it is necessary to use an unshielded twisted pair cable; for communication with workstations it is necessary to use an unshielded twisted pair cable.

At each workplace of enterprise specialists, it is necessary to install cable system ports in a quantity equal to 2. Moreover, the excess of the number of workplaces over the number of personal computers must be at least 30%, the average distance from the communication center to the workplace is 45 m.

The number of central servers should be 1.

Table 1 shows the distribution of applications and users across servers.

Table 1 - Services and clients

local area network modernization

6. Required configuration of the main server:

Processor type: Server (Intel Xeon 5140)

Number of processors in the server: 4

Amount of random access memory (RAM) of the server (MB): 4096

Required disk space (TB): 2

Desired chassis type: Intel Server Chassis SC5299-E

Data backup device required: Spire Spectrum II (1 TB)

The number of server communication lines must be 1

The transmission line speed must be 100 Mbit/s

Uninterruptible power supplies.

Based on the above tasks of modernizing the existing LAN at the enterprise, let’s move on to justifying the choice of equipment and equipment communications.

2.2 Trends in the future development of network equipment

Over time, the standards that made it possible to connect computers into local networks were gradually optimized, the throughput of communication channels increased, the software evolved, and the speed of data transfer increased. Soon, local networks began to be used not only for sending text and various documents between multiple computers, but also for transmitting multimedia information such as sound and images. This opened up the possibility of organizing video conferencing systems within a local network, allowing users of such a system to communicate in real time “directly”, physically being in different rooms, perform joint editing of texts and tables, and arrange “virtual presentations”. Already now, computer video communication systems are widely used by large commercial enterprises, where they serve to organize communications between various departments, in military complexes for the rapid transfer of information between several subscribers and entire units, and more recently - in home “desktop” systems, as a means organization of leisure. Among the advantages of KBC we can mention the relatively low cost of operation compared to other communication systems existing today, their versatility, and comparative ease of use. During the work process, video conference subscribers generally see images of the interlocutor and their own on their monitor screens, which is necessary for visual control of the established connection.

Emerging in last years the steady trend of convergence of local networks with corporate and global networks leads to significant interpenetration of their technologies (for example, Internet into local). This requires almost complete replacement of hardware and software LAN. Appendix B lists the main differences between network devices.

Along with rapidly developing network technologies that are in demand in all spheres of human activity, the development and production of hardware and software for networks does not stand still.

The promising development of hardware, cables, adapters, routers, switches, hubs and other network equipment is moving towards increasing the speed of information transmission and processing, providing protection against unauthorized interference in the operation of the network and equipment.

It should be noted that at present, many manufacturers of network equipment, at the design and production stage, include in their equipment the possibility of further improvement by updating the built-in software (firmware).

By using the latest Windows server 2008 operating system in local networks, improved operation of management utilities, connection stability, “burial” management, advanced filtering and data search, multiple selection, record checking, export functions, and good client fault tolerance are achieved. Windows server 2008 provides the ability to protect files and folders on NTFS volumes using the EFS encrypted file system.

2.3 Justification for choosing equipment for network modernization

Now that the main tasks have been defined, let us once again briefly recall the characteristics of the most common network equipment and the differences between them (Appendix B).

Ethernet repeaters, often called hubs or hubs, simply forward received packets to all of their ports regardless of destination.

The bridges operate in accordance with the IEEE 802.1d standard. Like Ethernet switches, bridges are protocol independent and forward packets to the port to which the destination is connected. However, unlike most Ethernet switches, bridges do not transmit packet fragments when collisions occur and packets with errors because all packets are buffered before being forwarded to the destination port. Packet buffering (store-and-forward) introduces latency compared to on-the-fly switching. Bridges can provide performance equal to the throughput of the media, but internal blocking reduces their performance somewhat.

The operation of routers depends on network protocols and is determined by the protocol-related information carried in the packet. Like bridges, routers do not forward packet fragments to the destination when collisions occur. Routers store the entire packet in their memory before transmitting it to the destination, hence, when using routers, packets are transmitted with a delay. Routers can provide bandwidth equal to the channel capacity, but they are characterized by internal blocking. Unlike repeaters, bridges, and switches, routers modify all transmitted packets.

The end network equipment is the source and recipient of information transmitted over the network.

Some network equipment uses the term loopback in the virtual interface used for management. Unlike a loopback interface, a loopback device does not communicate with itself.

A print server is a device that allows a group of wired and wireless network users to share a printer in their home or office. Has a high-speed USB 2.0, LPT or COM ports for connecting a printer. Typically equipped with a 10/100BASE Ethernet interface and often with a high-speed 802.11g wireless network interface. Supporting a variety of network operating systems, it brings a high level of flexibility and productivity to the printing process. When choosing equipment for a computer network, I, as the author, decided to choose 3Com as the manufacturer.

I chose 3Com due to good reviews about the equipment of this manufacturer, and also due to the fact that when producing their equipment they provide it with additional functions, technologies and protocols of their own design. The peculiarity is that if you build a network exclusively on active network equipment from 3Com, the reliability and efficiency of such a network increases significantly. This happens due to the fact that the equipment tests itself, as well as neighboring active nodes, while constantly maintaining up-to-date connections with each other. On a network with 3Com equipment, speed increases thanks to traffic compression technology. Switch type hubs were chosen as switching devices, since they not only transmit the packet to the destination port, unlike hubs, which just copy the received packet to all ports, but also amplify the signal. This avoids the effect of signal attenuation in remote areas of the network. In addition, Switch type devices can significantly relieve the network of unnecessary traffic, since, unlike hubs, the received signal is transmitted strictly to the destination port, and is not duplicated to all ports.

In the case of complex turnkey network construction, it is better to purchase equipment from one supplier, since:

Firstly, equipment supplies will most likely be one-time;

Secondly, you can count on significant discounts when purchasing equipment, which will make it possible to reduce the cost of the construction project of a new network as much as possible;

Thirdly, you can count on prompt round-the-clock technical support of this equipment and extended warranty service periods, which will significantly reduce the total cost of operating the equipment.

Based on the terms of the technical specifications and having discussed all the details with the supplier’s representative, who is also the official distributor of 3Com in Russia, I came to the choice of equipment.

Thus, a complete set of active and passive network equipment, with the exception of printers, was purchased for 65,048.68 rubles. Despite the fact that the selection used equipment of an above-average class, quite functional and of high quality, and with a margin of + 30% to existing workplaces, the project turned out to be relatively inexpensive even by today’s standards. All that remains is to configure the workstations after installing the network and connecting the final network equipment. Table 2 below shows how to configure the network parameters of user computers.

Table 2 - Network parameters of computer network users

The main gateway is the address of a computer that is intended to organize access for users of a computer network to the Internet. The main server is the Central server with the Microsoft Windows 2008 Server Enterprise Edition operating system installed on it (Appendix D), the network services Active Directory, DNS Server installed on it , File Server, etc. In this case, it is specified as a network parameter, since when logging on to the client computer, it is necessary to have a running DNS server on the network that can resolve host names by their network addresses, which also acts as a domain controller. The primary DNS server, unless it is also an Internet gateway, can only resolve a range of internal names. It is not able to serve client requests outside the internal network. The server is additional - in this case it is both an Internet gateway and a proxy server for the organization. It is registered as a network parameter of the user’s computer, since it is capable of resolving its requests for name resolution to external resources, to the Internet.

After setting up the central server, Internet gateway and client computers, the network is ready for use.

2.4 Prospects for the development of LAN of Torg-Service LLC

Currently, LAN hardware of various sizes is subject to requirements for increased reliability, fault tolerance, fault recovery, high throughput and load capacity, scalability, and improvement of other qualitative and quantitative characteristics that affect the performance of both an individual node and the entire network as a whole. . With each subsequent generation, these requirements are met by hardware manufacturers. However, development does not end there, but is just beginning.

Manufacturers, in addition to supporting open common protocols in their equipment, also include technologies, algorithms and protocols of their own invention that increase the functionality of devices, their performance and open up additional opportunities for fine-tuning and managing such equipment.

Development implies not only the improvement of what already exists, but also the production of what was not widely used before. Such a breakthrough in our century has been the use of broadband wireless access technologies for civilian purposes. These technologies include: SDH networks, RRL, WiMax, BWA, Wi-Fi.

Despite the fact that currently more widespread established and proven technologies X.25, Frame Relay, FDDI, ATM, Ethernet, wireless access technologies undoubtedly find application in certain niches. Moreover, in some cases, only wireless technologies will be able to provide access where there are no technical conditions for wired ones or there is simply no physical opportunity, due to their limitations, to lay a cable.

A Wi-Fi network is a radio network that allows you to transfer information between objects via radio waves (without wires). The Wi-Fi Alliance is developing standards in this area. The main advantage of Wi-Fi is the provision of “mobility” to clients, which is extremely convenient. The main disadvantage is vulnerability to attackers.

Currently, there are three standards available on the Russian market: 802.11a, 802.11b and 802.11g.

11b - equipment of this standard Supports transfer speeds up to 11 Mbps. Frequency - 2.4 GHz. Encryption - WEP. This standard has a continuation, the so-called 802.11b+. The main difference between 802.11b+ and 802.11b is speed. 802.11b+ allows you to exchange data at speeds of up to 22 Mbit/s.

11g is a more advanced standard that has increased the degree of protection and data transfer speed to 54 Mbit. Frequency - 2.4 GHz. Encryption - WEP, WPA, WPA2. The main feature of the equipment of this standard is its backward compatibility with the 802.11b standard. That is, if you previously purchased an 802.11g network adapter, you can be absolutely sure that you can work with it on an 802.11b network.

Both of the above standards are currently approved for use in the Russian Federation, which cannot be said about 802.11a.

11a is a standard similar to 802.11g, but created to allow multiple clients to connect simultaneously. Those. this standard allows for increased density compared to 802.11g. The second most significant difference is the frequency of the radio wave - 5 GHz. It is precisely because of the frequency that this standard cannot be used on the territory of the Russian Federation without special permission. (English: Worldwide Interoperability for Microwave Access) is a telecommunications technology developed to provide universal wireless communication over long distances for a wide range of devices (from workstations and laptops to mobile phones). The technology is based on the IEEE 802.16 standard, which is also called Wireless MAN. The name "WiMAX" was created by the WiMAX Forum, an organization that was founded in June 2001 with the goal of promoting and developing WiMAX technology. The forum describes WiMAX as “a standard-based technology that provides high-speed wireless network access as an alternative to leased lines and DSL.” It is suitable for the following applications:

Connecting Wi-Fi access points to each other and to other segments of the Internet.

Providing wireless broadband access as an alternative to leased lines and DSL.

Providing high-speed data transmission and telecommunications services.

Creating access points that are not tied to geographic location. Allows you to access the Internet at high speeds, with much greater coverage than Wi-Fi networks. This allows the technology to be used as “trunk channels”, a continuation of which are traditional DSL and leased lines, as well as local networks. As a result, this approach makes it possible to create scalable high-speed networks within entire cities.

The last mile problem has always been a pressing issue for telecom operators. By now, many last-mile technologies have appeared, and any telecom operator is faced with the task of choosing a technology that optimally solves the problem of delivering any type of traffic to its subscribers. There is no universal solution to this problem; each technology has its own area of ​​application, its own advantages and disadvantages. The choice of a particular technological solution is influenced by a number of factors, including:

operator strategy, target audience, currently offered and planned services,

the amount of investment in network development and their payback period,

existing network infrastructure, resources to maintain it in working order,

the time required to launch the network and begin providing services.

Each of these factors has its own weight, and the choice of a particular technology is made taking into account all of them together. A simple and effective model that allows you to quickly assess the economic parameters of using WiMAX technology

Many telecommunications companies are betting big on using WiMAX to provide high-speed communications services. And there are several reasons for this.

Firstly, the 802.16 family of technologies will make it possible to cost-effectively (compared to wired technologies) not only to provide network access to new clients, but also to expand the range of services and cover new hard-to-reach territories.

Secondly, wireless technologies are much easier to use than traditional wired channels. WiMAX and Wi-Fi networks are easy to deploy and easily scalable as needed. This factor turns out to be very useful when it is necessary to deploy a large network in the shortest possible time. For example, WiMAX was used to provide Internet access to survivors of the December 2004 tsunami in Indonesia (Aceh). The entire communication infrastructure of the region was disabled and prompt restoration of communication services for the entire region was required.

In total, all these advantages will reduce prices for the provision of high-speed Internet access services for both business structures and individuals.

2.5 Development and implementation of elements for modernizing LAN network equipment of Torg-Service LLC

The newly received equipment, the Antec P183 test bench, is proposed to be connected via a server, which is selected from the existing computers in service center. It must ensure operation within the service center and communication with the main LAN server. The choice was made on a standard PC configuration running Windows XP, 2 GB RAM, 400 GB hard drive memory.

Research has shown that in order to solve the problems set in the technical specifications (Appendix A) and meet the requirements for the operating system (Appendix D), it is necessary to install the Windows Server 2008 operating system on the central LAN server.

The case for the new server is equipped with powerful power supplies, additional fans, removable covers and a protective front panel. A Tower (Rack) (5U) case has been selected, certified by the motherboard manufacturer.

A high-speed DVD-ROM drive will not only save time when installing the OS and application software (software), but will also be extremely useful when working with a centralized help system.

Since all workstations connected to the network will constantly access the server, one of its most important components is a powerful 64-bit network card. It effectively manages information exchange, that is, it has a coprocessor that takes over the main functions of the central processor for processing data received by the server.

To provide additional reliability, two network cards simultaneously. Windows server 2008 comes with improved management utilities. Provides the ability to create stable connections and manage “burial”, advanced filtering and data search, multiple selection, record checking, and export function. server 2008 provides reliable protection for files and folders on volumes and provides network scalability.

Appendix E presents an option for upgrading the network at the customer’s request: including three mobile locations in the LAN (Appendix A). The organization of such a network model assumes the presence of a VPN server in the central office, to which remote clients connect. Remote clients can work from home, or, using a laptop computer, from anywhere on the planet where there is access to world wide web. This method It is advisable to use the organization of a virtual network in cases of geographically independent employee access to the organization’s local network via Internet access. Often, providers create VPN connections for their clients to organize access to Internet resources.

The so-called Extranet VPN, which provides access to an organization's clients through secure access channels, is gaining widespread use due to the popularity of e-commerce. In this case, remote clients will have very limited opportunities to use the local network; in fact, they will be limited to access to those company resources that are necessary when working with their clients, for example, a site with commercial offers, and VPN is used in this case for the secure transfer of confidential data. Information security tools - encryption protocols - are built into the remote access client computer.

Data encapsulation using the PPTP protocol occurs by adding the GRE (Generic Routing Encapsulation) header and the IP header.

This network is a domain network running Windows Server 2008. The server has two network interfaces with IP addresses, internal for the local network 11.7.3.1 and external 191.168.0.2 for connecting to the Internet. It should be noted that when designing networks, the VPN server is placed last.

In Windows Server 2008, installing the VPN server role is quite simple.

In our case, we have an already formed network, with the addresses described above. Next, you need to configure the VPN server and allow certain users to access the external network. There is an internal site on the local network, which we will try to access by including virtual elements in it.

Following the wizard's prompts in Figure 2, install:

in the first step the necessary parameters;

in the second step, select remote access (VPN or modem);

in the third step we establish remote access via the Internet;

in the fourth step we indicate the server interface connected to the Internet, in our case 191.168.0.2;

in the fifth step we determine the method of assigning addresses remote clients, in our case these will be automatically assigned addresses.

So, the VPN server has been created, after the installations have been completed, we move on to managing the users of our domain. For employees who need remote access to the organization’s internal network, we allow this same access by setting the appropriate switch on the “Incoming Calls” tab (see Figure 3).

It should be remembered that for correct operation it is necessary that the installed firewall allows the protocols used by the VPN.

Figure 2 - Screenshot of the Server Configuration Wizard dialog box

We are done with the server part, let's move on to creating the client part of the network on remote computer.

To create the client part of the LKS network (Figure 4) on a remote computer, you must:

in the first step, launch the Network Connection Wizard;

in the second step, following the prompts, select “Connect to the network at your workplace”;

in the third step “Connect to a local network”;

in the fourth step, enter the name of the connection;

in the fifth step, we select whether to pre-connect to the Internet (if you are connecting from a place with constant access, select “no”; if, for example, you use a mobile phone as a modem, then you should select pre-dialing a number to connect to the Internet).

in the sixth step, enter the IP address of the server being accessed (see Figure 4);

in the last (seventh) step, the properties are adjusted, and some points regarding security and the type of connection created are configured.

Figure 3 - Screenshot of the window for connecting addresses of mobile LAN users

In conclusion, I would like to say that in fact there are a lot of ways to use VPN. The method described in this final qualifying work is good because it ensures the security of not only the information that is transmitted, but also the connection itself.

Figure 4 - Screenshot of the “New Connection Wizard” window

The remote access configuration is complete, it's time to check its functionality. Let’s start traditionally, with everyone’s favorite “ping” command, let’s just try to “ping” some workstation from our modernized local network (Figure 5).

Everything works fine, all that remains is to measure the performance of the created network. To do this, copy the file through the VPN connection, and also, without using it, to the VPN server. The physical medium for transmitting information will be a 100 Mbit network; in this case, network throughput is not a limiting factor. So, copying a file of 342,921,216 bytes in size took 121 seconds. With a VPN connection - 153 seconds. In general, the loss in copying time was 26%, which is natural, since when transmitting information through a VPN, additional overhead costs arise in the form of data encryption/decryption.

Figure 5 - Connection test results window

In our case, the PPTP protocol was used; when using other types of protocols, the time loss will also vary. Microsoft currently recommends using L2TP IPSec with smart cards to provide maximum security for authentication and information transfer.

It is proposed to provide accounting of access time to the external environment (INTERNET) and internal LAN reserves using specialized software “Traffic Inspector”. The program is installed on the central LAN server and allows you to manage traffic, statistics, and accounting for the access provided, and access to the external network (INTERNET) is provided using the NAT protocol.

Below (Figure 6) is a screenshot of calling the Traffic Inspector program. It should be concluded that an inspection of the operation of the LAN equipment operating at Torg-Service LLC was carried out and the tasks were solved: developing a scheme for a modernized network, including three mobile workstations in the scheme, justification was carried out for the selection and installation of a modern operating system Windows server 2008 on the central LAN server , VPN server for the implementation of the modernized LAN network scheme, trial operation of the modernized LAN network was carried out.

Figure 6 - Screenshot of calling the Traffic Inspector program

Conclusion

In the final qualifying work, when studying and analyzing the composition and characteristics of network equipment by systematizing and integrating theoretical knowledge and conclusions from a practical examination of the local computer network operating at the service trade enterprise Torg-Service LLC, the following was carried out:

It is shown that an important task in the design, operation and modernization of a LAN is played by the structure (architecture) of the network model, technologies and protocols for the interaction of network elements.

The role, composition and characteristics of network equipment as an object of research are shown and studied.

It has been established that Torg-Service LLC, like any other enterprise, is extremely interested in maintaining “its” LAN at a modern level in order to conduct an effective business.

Trends in the future development of the composition and functions of network equipment, prospects for technologies and protocols for equipment interaction are analyzed.

Proposed practical scheme modernization of the existing LAN, with justification for the choice of network equipment and operating system in accordance with the technical specifications of the network user, Torg-Service LLC.

The first chapter of the work shows that the network equipment of a local computer network, being the most important component of the network architecture, cannot be considered without means of communication between the equipment and with the network server.

Structured cabling systems, universal data transmission medium in a LAN; server cabinets, connectors, crossover panels are protocol-independent equipment.

All other equipment in its design and functions significantly depends on what specific protocol is implemented in them. The main ones are network adapters (NA), concentrators or hubs, bridges and switches as a means of logical structuring of the network, computers.

Chapter 2 noted that many of today's networking devices combine a range of functions. For example, a modern ADSL modem, in addition to the function of connecting to the ISP provider’s network, is capable of performing the functions of a firewall (firewall), router and simple surge protector. Moreover, the cost of such a modem does not go beyond the cost of a middle-class modem.

If previously network administration was solved by specially developed complex software that was installed on computers, now this has become possible through the use of modern compact desktop devices or in rack-mount format, which perfectly cope with the solution certain tasks, be it VLAN switches, firewalls, comprehensive network protection equipment, carrier-grade equipment (multiplexers, interface converters, modular switches, etc.).

In many cases, manufacturers already at the production stage include in their equipment the possibility of improvement by updating the built-in software (firmware). This allows you to significantly reduce the total cost of equipment ownership, since with the release of next-generation equipment there is no need to throw away the old device and buy a new one. Simply download and install the update, and the device acquires additional functionality, support for new protocols and improved operating algorithms.

Access technologies are constantly evolving; there are already a huge number of solutions on the market for providing access using various technologies: wired and wireless. Moreover, it is absolutely not necessary for wired and wireless access technologies to compete with each other. Each of them has its own niche, its own area of ​​application. On the contrary, in the case of building complex and extensive systems, these technologies can be used in combination, and often one of the technologies creates a backup access channel that will work in the event of a failure of the main channel.

Completing this chapter of my final qualifying work allowed me to better understand the situation on the equipment market, with technologies that in the future will be used to build local computer networks. The main directions of development of network equipment are as follows:

increasing the capacity of communication channels;

increasing the speed of data transfer between ports in network devices;

expansion of the total bandwidth;

reducing delays when packets pass through active equipment ports;

improvement of existing technologies and protocols for access to the data network;

development of new promising access technologies;

development of more convenient and modern tools and methods for managing network equipment.

The practical part of the WRC, Chapter 3, presents the development and implementation of modernization of network equipment of the existing LAN at the service trade enterprise Torg-Service LLC within the framework of the “Terms of reference for the implementation of the technical part of the project for modernization of the local computer network operating at the enterprise”:

new equipment for testing embedded parts and components and PCs was connected;

mounted operating system Windows server 2008, replacing Windows server 2003;

Three mobile workstations were introduced into the LAN functioning scheme, for which a VPN server was installed and tested on the main north and on the computers of the mobile workstations.

Glossary

		the latest technology for building frame switching networks, providing high speed transmission data by sending data cells (fixed size frames) over broadband local and wide area networks.
		several buildings within one organizational structure located in a limited area.
		network topology, the operation of which is based on the transmission in a circle of a marker that determines the direction of data transfer.
		telecommunications technology designed to provide universal, long-range wireless connectivity to a wide range of devices
	Subscriber cable	a connecting cable used to connect equipment in a work area.
		a connecting element with different types of connectors allowing: - to connect asymmetrical cable connectors; - change the sequence (cross adapter) or the number of involved conductors in the connectors; - change the wave impedance (wave adapter).	specialist responsible for the normal functioning and use of resources automated system and/or computer network
	Wireless network	a network that does not use cables to connect components. Wireless network channels are laid over the air. Wireless network divided into radio networks and infrared networks.
	Wide Area Network	a computer network connecting computers that are geographically distant from each other. Global network connects local networks.
		element for transmitting an electronic signal through wires. Any cable consists of metal cores - wires - that conduct electric current. A wire is a kind of transmission medium for an electronic signal.
		signal transmission medium between two active equipment devices, including line, subscriber and network cables.
	The local network	unification of subscriber, network and peripheral equipment of a building or complex of buildings using physical (cable system) and radio channels for the purpose of sharing hardware and network resources and peripheral devices.
	Highway	a set of physical telecommunication channels between distribution points(telecommunication terminals - American standard) inside the building and between buildings.
	Router	a network device that, based on information about the network topology and certain rules, makes decisions about forwarding network layer packets (layer 3 of the OSI model) between different network segments.
	Main gate	the address of a computer that is intended to organize access for computer network users to the Internet.
		computer or software system that provide remote access to their services or resources for the purpose of exchanging information. Typically, communication between a client and server is maintained through message passing, and a specific protocol is used to encode client requests and server responses.
	Network card, also Ethernet adapter	a peripheral device that allows a computer to communicate with other devices on a network.
	Network hardware	devices necessary for the operation of a computer network, for example: router, switch, hub. Usually there are active and passive network equipment.
	Network hub	a network device designed to connect several Ethernet devices into a common network segment.
	Telecommunications	transmission and reception of electromagnetic signals or any information via wires, radio and other channels

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