Enterprise network equipment. What equipment is needed to create a local network

This article is about LAN basics, the following topics will be covered:

• The concept of a local network;
• Local network device;
• Equipment for local network;
• Network topology;
• TCP/IP protocols;
• IP addressing.

The concept of a local network

Net - a group of computers connected to each other with the help of special equipment that ensures the exchange of information between them. The connection between two computers can be direct ( point-to-point connection) or using additional communication nodes.

There are several types of networks, and the local area network is just one of them. A local area network is, in fact, a network used in one building or a separate room, such as an apartment, to allow the computers and programs used in them to communicate. Local networks located in different buildings can be interconnected using satellite communication channels or fiber optic networks, which allows you to create a global network, i.e. a network that includes several local networks.

The Internet is another example of a network that has long since become worldwide and all-encompassing, comprising hundreds of thousands of different networks and hundreds of millions of computers. Whether you access the Internet via a modem, a local connection, or a global connection, every Internet user is effectively a network user. A wide variety of programs are used to surf the Internet, such as Internet browsers, FTP clients, e-mail programs, and many others.

A computer that is connected to a network is called a workstation ( workstation). As a rule, a person works with this computer. There are also computers on the network on which no one works. They are used as control centers in the network and as information stores. These computers are called servers.
If computers are located relatively close to each other and connected using high-speed network adapters, then such networks are called local networks. When using a local area network, computers are usually located within the same room, building, or in several closely spaced houses.
To combine computers or entire local networks that are located at a considerable distance from each other, modems are used, as well as dedicated or satellite communication channels. Such networks are called global networks. Typically, the data transfer rate in such networks is much lower than in local ones.

LAN device

There are two types of network architecture: peer-to-peer ( Peer-to-peer) and client/server ( Client/Server), On the this moment the client/server architecture has practically supplanted the peer-to-peer one.

If a peer-to-peer network is used, then all computers included in it have the same rights. Accordingly, any computer can act as a server that provides access to its resources, or a client that uses the resources of other servers.

In a network built on a client / server architecture, there are several main computers - servers. The rest of the computers that are part of the network are called clients, or workstations.

Server - is a computer that services other computers on the network. There are various types of servers, differing from each other in the services they provide; database servers, file servers, print servers, mail servers, web servers, etc.

Peer-to-peer architecture has become popular in small offices or home LANs. In most cases, to create such a network, you will need a couple of computers that are equipped with network cards, and a cable. The cable used is a twisted pair cable of the fourth or fifth category. Twisted pair is so named because the pairs of wires inside the cable are twisted ( this avoids interference and external influences). You can still find quite old networks that use coaxial cable. Such networks are morally obsolete, and the information transfer rate in them does not exceed 10 Mbps.

After the network is created and the computers are connected to each other, you need to configure all the necessary parameters programmatically. First of all, make sure that operating systems with network support have been installed on the computers to be connected ( Linux, FreeBSD, Windows)

All computers in a peer-to-peer network are combined into workgroups that have their own names ( identifiers).
In the case of a client/server network architecture, access control is performed at the user level. The administrator has the opportunity to allow access to the resource only to certain users. Let's say you make your printer available to network users. If you do not want anyone to print on your printer, then you should set a password to work with this resource. With a peer-to-peer network, anyone who knows your password can access your printer. On a client/server network, you can restrict the use of the printer for some users, whether they know the password or not.

To access a resource in a local network built on a client / server architecture, the user must enter a username (Login - login) and password (Password). Note that the username is open information, and the password is confidential.

The process of verifying a username is called identification. The process of verifying that the entered password matches the username by authentication. Together, identification and authentication constitute the authorization process. Often the term authentication' - used in a broad sense: to indicate authentication.

From all of the above, we can conclude that the only advantage of a peer-to-peer architecture is its simplicity and low cost. Client/server networks provide a higher level of performance and security.
Quite often, the same server can perform the functions of several servers, such as a file server and a web server. Naturally, the total number of functions that the server will perform depends on the load and its capabilities. The higher the power of the server, the more clients it can serve and the more services it can provide. Therefore, a powerful computer with a large amount of memory and a fast processor is almost always assigned as a server ( as a rule, multiprocessor systems are used to solve serious problems)

LAN equipment

In the simplest case, network cards and a cable are enough for the network to work. If you need to create a fairly complex network, then you will need special network equipment.

Cable

Computers within a local network are connected using cables that transmit signals. A cable that connects two network components ( e.g. two computers) is called a segment. Cables are classified depending on the possible values ​​​​of the information transfer rate and the frequency of failures and errors. There are three main categories of cables most commonly used:

• twisted pair;
• Coaxial cable;
• Fiber optic cable,

To build local networks is now the most widely used twisted pair . Inside, such a cable consists of two or four pairs of copper wire twisted together. Twisted pair also has its own varieties: UTP ( Unshielded Twisted Pair - unshielded twisted pair) and STP ( Shielded Twisted Pair - shielded twisted pair). These types of cable are capable of transmitting signals over a distance of about 100 m. As a rule, UTP is used in local networks. STP has a braided copper filament sheath that has a higher level of protection and quality than the UTP cable sheath.

In the STP cable, each pair of wires is additionally shielded ( it is wrapped in foil), which protects the data that is being transmitted from external interference. This solution allows you to maintain high transmission speeds over longer distances than in the case of using a UTP cable. The twisted pair is connected to the computer using an RJ-45 connector ( Registered Jack 45), which closely resembles an RJ-11 phone jack ( regi-steredjack). Twisted pair is capable of providing network operation at speeds of 10.100 and 1000 Mbps.

Coaxial cable consists of a copper wire covered with insulation, a shielding metal braid and an outer sheath. The central wire of the cable transmits signals into which the data has been previously converted. Such a wire can be either solid or stranded. Two types of coaxial cable are used to organize a local network: ThinNet ( thin, 10Base2) and ThickNet ( thick, 10Base5). At the moment, local area networks based on coaxial cable are practically not found.

At the core fiber optic cable there are optical fibers (light guides) through which data is transmitted in the form of pulses of light. Electrical signals are not transmitted over fiber optic cable, so the signal cannot be intercepted, which virtually eliminates unauthorized access to data. Fiber optic cable is used to transport large amounts of information at the highest available speeds.

The main disadvantage of such a cable is its fragility: it is easy to damage it, and it can be mounted and connected only with the help of special equipment.

network cards

Network cards make it possible to connect a computer and a network cable. The network card converts the information that is intended to be sent into special packets. Packet - a logical collection of data, which includes a header with address information and information itself. The header contains address fields that contain information about the place of origin and destination of the data, the NIC analyzes the destination address of the received packet and determines whether the packet was actually sent this computer. If the output is positive, the board will send the packet to the operating system. V otherwise the packet will not be processed. Special software allows you to process all packets that pass within the network. This opportunity is used by system administrators when they analyze the operation of the network, and attackers to steal data passing through it.

Any network card has an individual address built into its chips. This address is called the physical or MAC address ( Media Access Control - access control to the transmission medium).

The order of actions performed by the network card is as follows.

1. Receiving information from the operating system and converting it into electrical signals for further sending over the cable;
2. Receiving electrical signals over a cable and converting them back into data that it can work with operating system;
3. Determining whether the received data packet is intended specifically for this computer;
4. Controlling the flow of information that passes between a computer and a network.

Hubs

concentrator (hub) is a device capable of connecting computers in a physical star topology. The hub has several ports that allow you to connect network components. A hub with only two ports is called a bridge. A bridge is needed to connect two network elements.

The network, together with the hub, is common bus". Data packets when transmitted through the hub will be delivered to all computers connected to the local network.

There are two types of concentrators.

passive concentrators. Such devices send the received signal without pre-processing it.
Active hubs ( multi-site repeaters). They receive incoming signals, process them and transmit them to connected computers.

Switches

Switches are needed to organize a closer network connection between the sending computer and the destination computer. In the process of data transfer through the switch, information about the MAC addresses of computers is recorded in its memory. Using this information, the switch compiles a routing table, in which for each of the computers it is indicated that it belongs to a certain network segment.

When the switch receives data packets, it creates a special internal connection ( segment) between its two Ports using the routing table. It then sends a data packet to the appropriate port on the destination computer based on the information described in the packet header.

Thus, this connection is isolated from other ports, which allows computers to exchange information at the maximum speed that is available for this network. If a switch has only two ports, it is called a bridge.

The switch provides the following features:

• Send a data packet from one computer to the destination computer;
• Increase data transfer rate.

Routers

The router is similar in principle to a switch, but has a larger set of functionality. It learns not only the MAC, but also the IP addresses of both computers involved in data transfer. When transporting information between different network segments, routers analyze the packet header and try to figure out the best path for the packet to travel. The router is able to determine the path to an arbitrary network segment using information from the routing table, which allows you to create a general connection to the Internet or a wide area network.
Routers allow packets to be delivered in the fastest way, which can increase the throughput of large networks. If some segment of the network is overloaded, the data flow will take a different path,

Network topology

The arrangement and connection of computers and other elements on a network is called a network topology. A topology can be compared to a network map showing workstations, servers, and other network equipment. The chosen topology affects the overall network capabilities, the protocols and network equipment that will be used, as well as the ability to further expand the network.

Physical topology - is a description of how they will be connected physical elements networks. The logical topology defines the routes of data packets within the network.

There are five types of network topology:

• Common bus;
• Star;
• Ring;

Common bus

In this case, all computers are connected to the same cable, which is called the data bus. In this case, the packet will be received by all computers that are connected to this network segment.

Network performance is largely determined by the number of computers connected to the common bus. The more such computers, the slower the network. In addition, such a topology can cause various collisions that occur when several computers simultaneously try to transmit information to the network. The likelihood of a collision increases as the number of computers connected to the bus increases.

Benefits of using networks with topology " common bus» the following:

• Significant cable savings;
• Ease of creation and management.

Main disadvantages:

• the probability of collisions with an increase in the number of computers in the network;
• a broken cable will shut down many computers;
• low level of protection of transmitted information. Any computer can receive data that is transmitted over the network.

Star

When using a star topology, each cable segment coming from any computer on the network will connect to a central switch or hub. All packets will be transported from one computer to another through this device. It is allowed to use both active and passive hubs. If the connection between the computer and the hub is broken, the rest of the network continues to work. If the hub fails, the network will stop working. With the help of a star structure, even local networks can be connected to each other.

Using this topology is convenient when searching for damaged items: cables, network adapters or connectors, " Star" more comfortable " common bus” and in case of adding new devices. It should also be taken into account that networks with a transmission rate of 100 and 1000 Mbps are built according to the topology " star».

If in the very center stars» position a hub, the logical topology will change to "common bus".
Advantages " stars»:

• ease of creation and management;
• high level of network reliability;
• high security of information that is transmitted within the network ( if a switch is located in the center of the star).

The main disadvantage is that the failure of the hub leads to the cessation of the entire network.

Ring topology

In the case of using a ring topology, all computers on the network are connected to a single ring cable. Packets loop in one direction through all the network cards of computers connected to the network. Each computer will amplify the signal and send it further along the ring.

In the presented topology, the transmission of packets around the ring is organized by the marker method. The marker is a specific sequence of binary bits containing control data. If a network device has a token, then it has the right to send information to the network. Only one token can be passed inside the ring.

The computer that is going to transport the data takes the token from the network and sends the requested information around the ring. Each subsequent computer will transmit data further until this packet reaches the destination. Upon receipt, the recipient will return an acknowledgment of receipt to the sending computer, and the latter will create a new token and return it to the network.

The advantages of this topology are as follows:

• more efficiently than in the case of a common bus, large amounts of data are served;
• each computer is a repeater: it amplifies the signal before sending it to the next machine, which allows you to significantly increase the size of the network;
• the ability to set different network access priorities; however, the computer with the higher priority will be able to hold the token longer and transmit more information.

Flaws:

• a break in the network cable leads to the inoperability of the entire network;
• an arbitrary computer can receive data that is transmitted over the network.

TCP/IP protocols

TCP/IP protocols ( Transmission Control Protocol/Internet Protocol - Transmission Control Protocol/Internet Protocol) are the main internetworking protocols and manage the transfer of data between networks of different configurations and technologies. It is this family of protocols that is used to transmit information on the Internet, as well as in some local networks. The TPC/IP protocol family includes all intermediate protocols between the application layer and the physical layer. Their total number is several dozen.

The main ones among them are:

• Transport protocols: TCP - Transmission Control Protocol ( communication control protocol) and others - manage the transfer of data between computers;
• Routing protocols: IP - Internet Protocol ( Internet Protocol) and others - provide the actual data transfer, process data addressing, determine the best path to the addressee;
• Network address support protocols: DNS - Domain Name System ( domain system names) and others - provides the determination of the unique address of the computer;
• Application service protocols: FTP - File Transfer Protocol ( file transfer protocol), HTTP - HyperText Transfer Protocol (Hypertext Transfer Protocol), TELNET and others - are used to gain access to various services: file transfer between computers, WWW access, remote terminal access to the system, etc.;
• Gateway protocols: EGP - Exterior Gateway Protocol ( external gateway protocol) and others - help transmit routing messages and network status information over the network, as well as process data for local networks;
• Mail protocols: POP - Post Office Protocol ( mail receiving protocol) - used to receive email messages, SMPT Simple Mail Transfer Protocol ( mail transfer protocol) is used to send mail messages.

All major network protocols ( NetBEUI, IPX/SPX and TCPIP) are routable protocols. But manually you have to configure only the TCPIP routing. Other protocols are routed by the operating system automatically.

IP addressing

When building a local network based on the TCP / IP protocol, each computer receives a unique IP address, which can be assigned either by a DHCP server - a special program installed on one of the network computers, or by Windows tools, or manually.

The DHCP server allows you to flexibly distribute IP addresses to computers and assign permanent, static IP addresses to some computers. The built-in Windows tool does not have this capability. Therefore, if there is a DHCP server on the network, then it is better not to use Windows tools by setting the operating system network settings to automatic ( dynamic) IP address assignment. Installing and configuring a DHCP server is beyond the scope of this book.

It should be noted, however, that when using a DHCP server or Windows tools to assign an IP address, it takes a long time for computers on the network to boot up and the operation for assigning IP addresses, the longer the larger the network. Also, the computer with the DHCP server must be turned on first.
If you manually assign static ( permanent, not changing) IP addresses, then computers will boot faster and immediately appear in a networked environment. For small networks, this option is the most preferred, and it is this that we will consider in this chapter.

For the TCP / IP protocol bundle, the base protocol is IP, since it is he who is responsible for moving data packets between computers through networks using various network technologies. It is thanks to the universal characteristics of the IP protocol that the very existence of the Internet, consisting of a huge number of heterogeneous networks, became possible.

IP protocol data packets

The IP protocol is the delivery service for the entire TCP-iP family of protocols. Information coming from other protocols is packaged into IP protocol data packets, an appropriate header is added to them, and the packets begin their journey through the network.

IP addressing system

One of the most important fields in the IP data packet header are the sender and destination addresses of the packet. Each IP address must be unique on the internetwork where it is used in order for the packet to reach its destination. Even in the entire global Internet network, it is impossible to meet two identical addresses.

An IP address, unlike a regular postal address, consists entirely of numbers. It occupies four standard computer memory cells - 4 bytes. Since one byte (Byte) is equal to 8 bits (Bit), the length of the IP address is 4 x 8 = 32 bits.

A bit is the smallest possible unit of information storage. It can only contain 0 ( bit cleared) or 1 ( bit set).

Although an IP address is always the same length, it can be written in different ways. The format for writing an IP address depends on the number system used. In this case, the same address can look completely different:

The binary number 10000110 is converted to decimal as follows: 128 + 0 + 0 + 0 + 0 + 4 + 2 + 0 =134.
The most preferred option, in terms of human readability, is to write the IP address in dotted decimal notation. This format consists of four decimal numbers separated by dots. Each number, called an Octet, is the decimal value of the corresponding byte in the IP address. An octet is called so because one byte in binary form consists of eight bits.

When using dotted decimal notation to write octets in an IP address, keep in mind the following rules:

• Only integers are allowed;
• Numbers must be between 0 and 255.

The most significant bits in the IP address, located on the left, determine the class and network number. Their combination is called the subnet identifier or network prefix. When assigning addresses within the same network, the prefix always remains the same. It identifies the ownership of the IP address of the given network.

For example, if the IP addresses of computers on the subnet 192.168.0.1 - 192.168.0.30, then the first two octets define the subnet ID - 192.168.0.0, and the next two - host IDs.

How many bits are used for one purpose or another depends on the class of the network. If the host number is zero, then the address does not point to any one particular computer, but to the entire network as a whole.

Network classification

There are three main classes of networks: A, B, C. They differ from each other in the maximum possible number of hosts that can be connected to a network of this class.

The generally accepted classification of networks is shown in the following table, where it is indicated the largest number network interfaces available for connection, which octets of the IP address are used for network interfaces (*), and which remain unchanged (N).

For example, in the networks of the most common class C, there cannot be more than 254 computers, so only one, the lowest byte of the IP address, is used to number network interfaces. This byte corresponds to the rightmost octet in dotted decimal notation.

A legitimate question arises: why can only 254 computers be connected to a class C network, and not 256? The fact is that some intranet IP addresses are intended for special use, namely:

O - identifies the network itself;
255 - broadcast.

Network segmentation

The address space within each network allows splitting into smaller subnets by the number of hosts ( Subnets). The process of subnetting is also called sharding.

For example, if the class C network 192.168.1.0 is divided into four subnets, then their address ranges will be as follows:

• 192.168.1.0-192.168.1.63;
• 192.168.1.64-192.168.1.127;
• 192.168.1.128-192.168.1.191;
• 192.168.1.192-192.168.1.255.

In this case, not the entire right octet of eight bits is used for host numbering, but only the 6 least significant of them. And the two remaining high bits determine the subnet number, which can take values ​​from zero to three.

Both regular and extended network prefixes can be identified using a subnet mask ( subnet mask), which also allows you to separate the subnet ID from the host ID in an IP address by masking the subnet portion of the IP address with a number.

The mask is a combination of numbers appearance resembling an IP address. The binary representation of the subnet mask contains zeros in bits that are interpreted as a host number. The remaining bits set to one indicate that this part of the address is a prefix. The subnet mask is always used in conjunction with the IP address.

In the absence of additional subnetting, the masks of the standard network classes have the following meanings:

When the subnetting mechanism is used, the mask changes accordingly. Let's explain this using the already mentioned example with the division of a class C network into four subnets.

In this case, the two most significant bits in the fourth octet of the IP address are used to number the subnets. Then the mask in binary form will look like this: 11111111.11111111.11111111.11000000, and in dotted decimal form -255.255.255.192.

Private network address ranges

Each computer connected to the network has its own unique IP address. For some machines, such as servers, this address does not change. Such a permanent address is called a static address. For others, such as clients, the IP address can be fixed (static) or dynamically assigned each time you connect to the network.

To get a unique static, that is, a permanent IP address on the Internet, you need to contact a special InterNIC organization - Internet Network Information Center ( network information Center Internet). InterNIC assigns only the network number, and the network administrator must deal with further work on creating subnets and numbering hosts on his own.

But formal registration with InterNIC in order to obtain a static IP address is usually required for networks that have a permanent connection to the Internet. For private networks that are not part of the Internet, several blocks of address space are specially reserved, which can be freely used to assign IP addresses without registering with InterNIC:

However, these addresses are used only for internal network addressing and are not intended for hosts that directly connect to the Internet.

The LINKLOCAL address range is not a network class in the usual sense. It is used by Windows when automatically assigning private IP addresses to computers on a local network.

I hope you now have an idea about the local network!

A local network within a company or apartment allows you to combine several devices into single system. With the help of such a network it is convenient to exchange files and documents. A local area network (LAN) also saves a lot of time by connecting printers, fax machines, and other shared devices.

Features of network equipment of local area networks

Network equipment refers to all devices that make up a local area network.

Network equipment can be conditionally divided into two types:

1. Active network equipment. It transforms, processes received and transmitted information. This includes print servers, network cards, and routers.


2. Passive network equipment. Cables, connectors, power sockets, signal amplifiers do nothing with the information, they only contribute to the physical transmission of the signal.

Depending on the structure of the LAN, the hardware configuration required to create it will vary.

Wireless LAN equipment

Wireless LAN is the network of the future. It is now becoming an increasingly popular option for equipping offices and especially apartments. Its big advantage is that there is no need to run wires from device to device. The downside until recently was the speed of data transfer. But now this is no longer a problem.

On the local network with wireless connection there must be at least one computer or server that broadcasts a signal to other devices. It can itself be connected to the network via a network card and cable, or via a 3G / 4G-type modem. Further signal transmission from the main access point can be carried out using a number of devices.

Wi-Fi routers allow you to connect to the network using cables and transmit information to other devices using a radio signal. Usually they have several outputs for distributing a cable signal, in some situations this allows you to increase the number of connected devices. Or solve issues with those in which there is no sensor for processing the wireless signal.

UCB adapters. This type of device is connected to computers or laptops, printers that do not have a built-in sensor for processing a Wi-Fi signal. It can serve as a cable replacement and allows even legacy devices to be used inside the WLAN.

Wi-Fi access point antennas are needed in a large office or room if the signal from the main router or switch is not enough for the entire area.

From overall structure network depends on the list of other equipment. But if a wireless LAN is made on the basis of new equipment, then, as a rule, you can save a lot on various adapters and adapters. Indeed, recently every printer, fax machine or camera has sensors for transmitting information via Bluetooth or using a Wi-Fi connection.

Equipment for creating a local network

Most users still prefer wired LANs. This has its own rationale. Most often, this solution allows you to win in speed and performance. It is easy to imagine a high-speed wireless network in an apartment where five people live and where several devices are used simultaneously. In an enterprise or office, hundreds or thousands of computers need to be brought together. And here it is difficult to do without professional telecommunication equipment.

V general view creating a LAN requires the use of several types of equipment:

1. Servers. This is the most expensive part. For a small network, you can make a regular computer a server computer. A large network will require the use of professional server hardware, which can be bought or rented.


2. Cables and wires for connecting individual computers into a single system.


3. Switches, distributors, gateways. These are passive and active network equipment that distributes or converts the signal.


4. End devices (computers, laptops, tablets, printers).

Some companies make their own server rooms and serve the local network at their own facilities. Such a solution is expensive, but it allows you to be sure that the network security system and its performance are in your own hands.

Service providers for creating a LAN in corporate systems offer other solutions:

• rent of servers or their parts (co-location);


• a cloud service that allows you to store data on a distributed system of servers, it costs less than renting servers.

LAN Equipment Manufacturers

Among manufacturers network equipment there are several big names. These include companies:

• D-Link Systems;
• 3Com Corporation;
• Cisco;
• Sagem.

Cable products are produced by many telecommunications and computer companies.

There are manufacturers who create a wide range of solutions, for example, Cisco. There are those who specialize in certain areas. An example is the French company Nexans, which produces cables, including network cables, which are especially resistant to temperature changes.

Wholesale suppliers of LAN equipment

Vendors involved in the supply of telecommunications equipment are divided into three types.

• suppliers integrated solutions Full construction. These include Cisco and HP;


• companies specializing in a particular direction, on wired or wireless types of LAN. This type of enterprise includes Avaya, Dell, and Extreme Networks;


• suppliers of a narrow group of equipment, individual components for networks. Here experts include the brands Allied Telesis, D-Link, Brocade, Juniper Network.

Previously, corporate customers preferred to equip offices with turnkey networks, they turned to the first group of vendors to solve their problems. This saved a lot of time, but it didn't always give them the best value for their money.

The second group of vendors has occupied its niche due to proposals for optimizing and reducing the costs of creating and maintaining networks. For example, Avaya is working on increasing the throughput of wireless networks, and Dell is trying to develop universal switches that are compatible with various brands of network equipment.

The search for the optimal solution to a specific problem can lead the customer to any of the three types of company. All of them have a place in a growing market.

Examples of modern network equipment for local area networks are demonstrated at the annual Sviaz exhibition.

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

Rice. 1.1.

The average speed of information in a twisted pair is 100 megabits / sec, wave resistance- 100 ohm. At higher data rates, there is a sharp increase in signal attenuation(the higher the speed, the greater the attenuation). So, at a speed of 100 Mbps (100 MHz), the amplitude drops by a factor of 1000, which is equivalent to a signal attenuation of 67 dB. Signal delay per meter of cable is typically 4-5 nanoseconds. Comparing twisted pair with other cables, it can be noted that it is easy to install, but is prone to interference. The cable is relatively cheap, but with low information security. Transmission in it according to the point-to-point method (one receiver and one transmitter), for the installation of a twisted pair, star topology is usually used. 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). In a category 3 cable - 9 turns per meter, attenuation up to 40 dB and information speed up to 10 megabits sec. The cable of the 4th category transmits a signal up to 20 MHz. Category 5 is the most popular. It has an information rate 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 screen for both individual conductors and a common one. With regard to cable insulation, PVC (non-plenum) insulation is most often used. gray color. It is cheap, but burns with the release of poisonous gas. The cable is connected to the network card by the 8P8C connector (Fig. 1.2).

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

The cable connects to the network card via a BNC (BI EN SI) bayonet-type connector with a turn (Fig. 1.4).

Compared to twisted pair, coaxial is more expensive, its repair is more difficult, and flexibility is worse (especially for a thick cable). 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 Gbps, is not subject to electrical interference. Signal transmission without attenuation goes to a distance measured in kilometers - fig. 1.5. In a multimode cable, a segment has a length of up to 2 km, and in a single-mode cable, up to 40 km.

Bits of information are encoded by entities such as strong light, weak light, no light. 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 secrecy. The installation of such a cable is complex and expensive, usually by welding on special equipment. The cable is sometimes armored, i.e. protected by a metal sheath (for strength). Optical cable can be single-mode or multi-mode. 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 signal transmission. In addition to being expensive, a powerful laser is also short-lived. Multimode optical cable is more commonly used in practice. It uses many 0.85 µm wavelengths and an infrared diode. Since each wave has its own attenuation and refraction, a partial distortion of the signal shape occurs and such a cable is used at shorter distances than single-mode. Among other features of an optical cable, it can be noted that glass can crack from mechanical stress and become cloudy from radiation, which, in turn, leads to an increase in signal attenuation in the cable. Teflon (plenum) is usually used for fiber insulation. This is an expensive (compared to PVC) orange insulation, but it practically does not burn in a fire. The cable connector is usually bayonet type (Fig. 1.6). The figure shows an ST type optical connector, which is glued to the cable, i.e. by gluing the optical fiber into the ferrule, followed by drying and grinding. Connectors for mounting and connecting cords differ in the diameter of the shank (respectively 0.9 and 3.0 mm) and the absence of the first cable attachment elements. Singlemode and multimode connectors differ in their capillary tolerance requirements for the ceramic tip.

Introduction

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

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

The main network equipment of the LAN: cables with terminal transceiver equipment; workstations - computers; servers - more powerful computers; network adapters - network boards; modems; concentrators; switches; routers and bridges.

On the modern market computer equipment and technology LAN network equipment, including personal computers, is represented by a great variety of different types, modifications, and developments of competing manufacturers. This class of equipment is updated continuously, on average it becomes obsolete in 5-7 years, which creates an objective need for computer technology specialists and specialists associated with computer technology, constantly monitor market fluctuations and conduct an analysis of the composition and characteristics of LAN network equipment at any necessary current moment. The topic is relevant. The above and my personal interest, as the author of the final qualifying work in the implementation terms of reference for the modernization of the existing LAN at the service trade enterprise Torg-Service LLC, where I passed industrial practice and determined the choice of topic.

The subject of research of the final qualifying work is the equipment of a local area network (LAN).

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

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

The objectives of the study follow from the goal:

To study the scientific literature on the problem under consideration.

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

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

Examine the LAN of Torg-Service LLC and analyze network equipment in order to modernize the operation of the network operating at the enterprise within the framework of the terms of reference.

Develop and introduce into production the elements of network modernization.

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

Graduation Research Methods qualifying work are the 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 Characterization of the subject area

A local area network (LAN) is a system of 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 to be solved when creating local computer networks is to ensure the compatibility of equipment in terms of electrical and mechanical characteristics and ensure compatibility information support(programs and data) by 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 the technical proposals of the International Standards Institute ISO (International Standards Organization).

The OSI Network Model (EMBOS), the Open Systems Interconnection Basic Reference Model (1978), is an abstract network model for communications and network protocol development. Offers a dimensional view of a computer network. Each dimension serves its part of the equipment interaction process. Thanks to this structure, the joint operation of network equipment and software becomes much easier 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 top level is applied. At this level, the user interacts with the computer system. The lower level is physical. It provides signal exchange between devices. Data exchange in communication systems occurs by moving them from the upper layer to the lower one, then transporting them, and finally playing them back on the client computer as a result of moving from the lower layer 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 between programs and data (software protocols). Physically, protocol support functions are performed by hardware devices (interfaces) and software tools (protocol support programs). Programs that support protocols are also called protocols.

Each level of architecture is divided into two parts:

service specification;

protocol specification.

The service specification defines what a layer does, and the protocol specification defines how it does it, and each layer can have more than one protocol.

Consider the functions performed by each level of software:

The physical layer performs connections with the physical channel, so, disconnections from the channel, channel management. The data transfer rate and network topology are determined.

The lowest level of the model is intended directly for the transfer of data flow. Carries out the transmission of electrical or optical signals to a cable or radio broadcast and, accordingly, their reception and conversion into data bits in accordance with the methods of encoding digital signals. In other words, it provides an interface between a network carrier and a network device.

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

At this level, concentrators (hubs), repeaters (repeaters) of the signal and media converters work.

Physical layer functions are implemented on all devices connected to the network. On the computer side, physical layer functions are performed by a network adapter or a 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 medium as fiber optic, 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 link layer adds auxiliary symbols to the transmitted information arrays and controls 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 tools.

The oop 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 link layer can interact with one or more physical layers, controlling and managing this interaction.

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

The network layer determines the route of information transfer between networks, provides error handling, as well as data flow control. The main task of the network layer is data routing (transfer of data between networks).

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

Network layer protocols route data from a source to a destination. At this level, a router (router) operates.

The transport layer connects the lower layers (physical, data link, network) with the upper layers, which are implemented by software. This layer separates the means of generating data in the network from the means of their transmission. Here, 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 transmission from the sender to the recipient. At the same time, the level of reliability can vary over a wide range. 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 correct sequence, multiplex multiple data streams, provide data flow control mechanism and guarantee the validity 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 transmission; restores the connection after errors during the communication session without data loss.

Examples: UDP is limited to data integrity control within a single datagram, and does not exclude the possibility of losing the entire packet, or duplicating packets, violating the order of receiving data packets. TCP provides reliable continuous data transmission, excluding data loss or violation of the order of their arrival or duplication, it can redistribute data by breaking large portions of data into fragments and vice versa gluing fragments into one packet.

Presentation level - manages the presentation of data in the form required for 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 data is received, this presentation 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 by applications. At this level, compression/decompression or encoding/decoding of data can be performed, as well as redirecting requests to another network resource if they cannot be processed locally.

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

The presentation layer deals not only with the formats and presentation of data, it also deals with the data structures that are used by programs. Thus, layer 6 provides for the organization of data during its transfer.

The application layer interacts with network application 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 layer is to provide a user-friendly interface.

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

remote access to files and databases

email forwarding.

From the above, we can conclude:

At different levels, the exchange occurs with different units of information: 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 transceiver 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 is understandable to the computer. The computer processes the received information and, as necessary, displays the result on the monitor screen. Usually distinguish between active and passive network equipment.

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

Passive network equipment refers to 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. Mounting cabinets are divided into: typical, specialized and anti-vandal. 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 a network card, network adapter, Ethernet adapter, NIC (English network interface controller) - peripheral device, which allows the computer to communicate with other devices on the network. Currently, network cards are integrated into motherboards for the convenience and cost reduction of the entire computer as a whole.

According to the constructive implementation, network cards are divided into:

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

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

embedded in motherboard.

On 10-Mbit NICs, 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 at any given moment only one of them works.

Next to the twisted pair connector, one or more information LEDs are installed to indicate the presence of a connection and the transfer of information.

One of the first mass network cards was Novell's NE1000/NE2000 series, and there were quite a few Soviet clones of network cards with a BNC connector in the late 1980s, 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 end node of the network - a computer. More precisely, in a network operating system, the adapter/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, which is common to all network adapter drivers, regardless of which technology the driver supports.

The network adapter, together with the driver, perform two operations: transmitting and receiving a frame. Transferring a frame from a computer to a cable consists of the following steps (some may be missing, depending on the encoding methods used):

Reception of an LLC data frame through an inter-layer interface along with MAC-layer address information. Usually, interaction between protocols inside a computer occurs through buffers located in RAM. Data for transfer to the network is placed in these buffers by upper-level protocols, which retrieve them from disk memory or from file cache using the I / O subsystem of the operating system.

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

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

Issuance of signals to the cable in accordance with the accepted line code - Manchester, NRZ1. MLT-3 etc.

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

Receiving from the cable signals that encode the bit stream.

Isolation of signals against the background of 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's receiver, with a high degree of probability coinciding with the one that was sent by the transmitter.

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

Frame checksum check. If it is incorrect, then the frame is discarded, and the corresponding error code is transmitted to the LLC protocol through the interlayer interface upwards. If the checksum is correct, then the LLC frame is extracted from the MAC frame and transmitted through the inter-layer interface upstream, to the LLC protocol. The LLC frame is buffered in RAM.

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

First generation network adapters use a multi-frame buffering technique. In this case, the next frame is loaded from the computer's memory into the adapter's 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 to transfer this frame from the buffer to the computer's memory at the same time as receiving another frame from the network.

Second-generation network adapters make extensive use of highly integrated chips, which improves the reliability of the adapters. In addition, the drivers for these adapters are based on standard specifications. Second-generation adapters typically come with drivers that work in both the NDIS (Network Driver Interface Specification) standard developed by 3Com and Microsoft and approved by IBM, and the ODI (Open Driver Interface Specification) standard developed by Novell.

Third-generation network adapters (3Com includes its adapters of the EtherLink III family among them) implement a pipelined frame processing scheme. 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 chain " RAM- adapter - physical channel - adapter - RAM". Such a scheme is very sensitive to the transmission start threshold, that is, to the number of frame bytes that are loaded into the adapter's buffer before transmission to the network begins. The third generation network adapter self-tunes this parameter by analyzing the operating environment, as well as by calculating, without the participation of a network administrator. Self-tuning provides the best possible performance for a particular combination of the performance of the computer's internal bus, its interrupt system, and its direct memory access system.

Third-generation adapters are based on application-specific integrated circuits (ASICs), which increase the performance and reliability of the adapter while reducing its cost. 3Com called its frame-pipelining technology Parallel Tasking, and other companies have implemented similar schemes in their adapters. Improving the performance of the "adapter-memory" link 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 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 speed up the network.

Network adapters produced today can be attributed to the fourth generation. Modern adapters necessarily include an ASIC that performs MAC-level functions (MAC-PHY), the speed is developed up to 1 Gb / s, and there are also a large number of high-level functions. The set of such functions may include support for the RMON remote monitoring agent, frame priority scheme, computer remote 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 of electronic signal transmission over wires. Any cable consists of metal cores (wires) that conduct electricity. Wire is a kind of electronic signal transmission medium. When installing the cable, it is necessary to adhere to the methods of correct cable laying. The cable should not be bent at an acute angle (it is better to have a rounded corner) to reduce the likelihood of microdamage. Network equipment is very sensitive to such damage. Do not repeatedly bend and unbend the cable. This also leads to a violation of its microstructure and, as a result, the data transfer rate will be lower than usual, and the network will fail more often.

In computer stores, you can find cables that are already originally 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.

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

The RJ-11 jack is more commonly known as a telephone jack. The cable under 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: the ones 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. It will not be difficult for a user who has the ability to connect to a computer local network to connect 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 used to be built. Now such networks are almost non-existent. However, the 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, decoders for satellite dishes and modems.

A router or router is 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.

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

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

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

The 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) with which you can turn your PC into a high-performance and feature-rich router, such as the Quagga.

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

When creating large computer networks for any institutions, 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 deal exclusively with the creation of the computer network itself.

So, the system administrator's tools include: RJ-45 pliers, a clerical 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 mounting equipment in system case, universal screwdriver, calculator. And now in order about each element separately.

RJ-45 pliers: used for crimping twisted pair, their presence is mandatory if you are going to install a network.

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

The main function of the repeater (repeater) is the repetition of signals received on one of its ports, on all other ports (Ethernet) or on the next port in the logical ring (Token Ring, FDDI) synchronously with the original signals. The repeater improves the electrical characteristics of the signals and their synchronism, 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 not only implements the signal repetition function, but also concentrates the functions of connecting computers to a network in one device. In almost all modern networking standards, a hub is a mandatory element of a network that connects individual nodes into a network.

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

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

The hub works at the physical layer of the OSI network model, repeats the signal coming to one port to all active ports. If a signal arrives at two or more ports, a collision occurs at the same time, 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 provided access bandwidth.

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

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

Let's denote the following characteristics of network hubs:

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

Data transfer rate - measured in Mbps, hubs are available with speeds of 10, 100 and 1000. In addition, hubs with the ability to change the speed are mainly common, referred to as 10/100/1000 Mbps. The speed can be switched both automatically and using jumpers or switches. Typically, if at least one device is attached to a hub at a low range speed, it will send data to all ports at that speed.

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

Workstations (RS) are formed in a LAN based on personal computers (PCs) and are used to solve applied problems, issue requests to the network for service, 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 network resources for general access, but can also work like ordinary computers.

The server is based on a powerful computer, much more powerful than workstation computers.

There may be several different servers in the LAN for managing network resources, but there is always one (or several) file server (server without data) for managing external storage devices (storage) public access and organizations distributed bases 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 well-defined network topology.

1.3 Technologies and protocols for the interaction of LAN hardware

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

However, in order for the link layer to cope with this task, the structure of the LAN must be well defined, for example, the most popular protocol channel level - 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 well-defined configuration of communications between computers - a ring connection. 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. Ownership of this token guarantees the right to transfer. If the host receiving the token has no information to send, it simply forwards the token to the next end station. Each station can hold the token 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 technologies from the Ethernet family, despite the fact that the company used Token Ring for a long time as the main technology for building local area 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(English multistation access unit (MSAU)), while IEEE 802.5 does not focus on topology. Appendix B shows the differences between the technologies. ring - Local area network (LAN) technology rings with "token access" - 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 marker that moves around the ring. Ownership of a token grants the right to the holder to transmit information on the medium. Ring frames with token access move in a loop.

Stations on a local area network (LAN) Token ring are logically organized in a ring topology with data being transmitted 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 occurs during the operation of a local network. In Ethernet technology, such collisions occur during the simultaneous transmission of information 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 send, it grabs the token, changes one bit of it (resulting in the token becoming the "beginning of data block" sequence), adds the information it wants to transmit, and sends this information to the next ring network stations. When an information block circulates around the ring, there is no token on the network (unless the ring provides an "early token release"), so other stations wishing to transmit information must wait. Therefore, collisions cannot occur in Token Ring networks. If early release of the token is provided, then a new token can be issued after the transmission of the data block 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 finally removed after reaching the station that sent the block. The sending station can check the returned block to ensure that it has been viewed and then copied by the destination station.

Unlike CSMA/CD networks (such as Ethernet), token passing networks are deterministic networks. This means that it is possible to calculate the maximum time that will pass before any end station can transmit. This characteristic, along with some reliability characteristics, makes 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 important not so much speed as reliable information delivery. Currently, Ethernet is not inferior to Token Ring in terms of reliability and is significantly higher in performance.

In the past few years, there has been a movement towards the rejection of the use of shared data transmission media in local networks and the 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 that combines shared and individual data transmission media is used in technologies that have traditional names with the prefix switching (switching): switching Ethernet, switching Token Ring, switching FDDI .

But, despite the emergence of new technologies, the classic Ethernet and Token Ring local area networks, 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) - A fiber-optic interface for distributed data - a standard for data transmission in a local area network stretched over a distance of up to 200 kilometers. The standard is based on the Token Ring protocol. In addition to a large area, the FDDI network is capable of supporting several thousand users.

FDDI recommends using fiber optic cable as the data transmission medium, 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 backbone communication channels.

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

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

The main advantages of Fast Ethernet technology are:

increase in the bandwidth of network segments up to 100 Mb/s;

preservation of star network topology and support for traditional data transmission media - twisted pair and fiber optic cable.

Implementation options for 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 cable conductors of category 5 or shielded twisted pair STP Type 1;

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

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

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

BASE-FX - Fast Ethernet variant using fiber optic cable. This standard uses the long-wavelength part of the spectrum (1300 nm) transmitted over two strands, one for reception (RX) and one for transmission (TX). The length of a network segment can be up to 400 meters (1310 feet) in half duplex mode (with guaranteed collision detection) and two kilometers (6600 feet) in full duplex mode using multimode fiber. Long distance operation is possible with single-mode fiber. 100BASE-FX is not compatible with 10BASE-FL, 10 Mbps over fiber.

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 backward compatible with 10BASE-FL. Due to the use of shorter wavelengths (850nm) and the short distance 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 the 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 that uses single-mode fiber along with a special multiplexer that splits the signal into transmit and receive waves.

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

BASE-LX WDM - 100Mbps Ethernet option via fiber optic cable. Maximum segment length 15 kilometers in full duplex mode over one single mode optical fiber at a wavelength of 1310 nm and 1550 nm. There are two types of interfaces, they differ in the transmitter wavelength and are marked either with numbers (wavelength) or with one Latin letter A (1310) or B (1550). Only paired interfaces can work in a pair: on the one hand, a transmitter at 1310 nm, and on the other, at 1550 nm.

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

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. Joint transmission of various types of information is allowed, including video, voice.

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

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

work with constant and variable data streams;

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

support point-to-point, point-to-set, set-to-set connections.

ATM technology involves interconnection at three levels.

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

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

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

The results of comparing 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 features: end stations or hubs; according to the option of accession to the primary and secondary rings; by the number of MAC nodes and, accordingly, MAC addresses per station.

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

Obviously, a station can only use the fail-safe features provided by having two FDDI rings if it is dual-connected. As can be seen from Figure 1, the reaction of stations to a cable break is to change the internal ways of transmitting information between the individual components of the station. A virtual network is a group of network nodes, whose traffic, including broadcast traffic, is completely isolated from other network nodes at the data link level. This means that it is not possible to send frames between different virtual segments based on the link layer address, regardless of whether the address is unique, multicast, or broadcast. At the same time, within the 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 connected stations in the event of a cable break

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

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

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

Linking virtual networks to the internet requires network layer involvement. 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 MAC - addresses;

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

LANE specification for ATM switches;

Using the network layer;

VLAN based on port grouping.

The study and analysis of the scientific and technical literature of the subject area of ​​the final qualification work showed that: the need to meet the growing requirements of production workers for local area networks contributes to a dynamic change in the purpose, composition, structure, and methods of network organization. This, in turn, requires the development and implementation of new and more advanced types of network hardware, as well as the development in dynamics 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, had an internship at the service trade enterprise Torg-Service LLC. Working as a duty engineer for maintenance of technical means of a local network operating at the enterprise since 2006, he studied the advantages and disadvantages of existing equipment, got the opportunity to implement his knowledge in the development and implementation of the “Terms of Reference” received from the enterprise for the technical part of the project for upgrading the local computer operating at the enterprise networks” (Appendix I).

2. Inspection and analysis of the LAN LLC "Torg-Service" 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 enterprise, for the purpose of making a profit, is engaged in the production and adaptation of media materials, advertising audio clips; develops, at the request of users, software products for broadcasting companies, advertising performances, concerts, etc.; 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, it became necessary to modernize the local area network (LAN) operating at the enterprise.

The project of modernization of 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 component parts of computers, testing of PC performance;

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

connection of three mobile workstations to the central LAN server.

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

Types and volumes of work to be performed.

Conduct a survey of the LAN operating at the enterprise in order to revise the network equipment, the operation of protocols, the organization and maintenance of databases, as well as the operation of the server.

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

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

Carry out trial operation of the modernized LAN of the enterprise.

2.1 Structure of the enterprise and operating LAN

The survey of the LAN of the service trade enterprise LLC "Torg-Service" was carried out as part of the "Terms of Reference for the implementation of the technical part of the project for the modernization of the local area network operating at the enterprise" (Appendix I), led to the following conclusions:

The company currently consists of 4 production departments and an administrative and economic department, which includes accounting and a garage. The company is located in the same building and on the same 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 purchase of components, PCs, work with clients, 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

enterprises, namely the list of services provided to the population, in order to ensure the 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 population for repair or sale.

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

The structure of a network running a network OS Windows Server 2003, which unites 20 computers, corresponds to the structure of information flows. Depending on the network traffic, the 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 the computers of this group.

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

Packet routing in the network follows the star topology.

Access rights to information are determined individually for the employees of each department. Some of the information is public, and some should be available only to users of a certain department.

All network users have access, both to internal information resources organizations, and to the resources of the global Internet. Moreover, in this case, access rights are also assigned individually to the 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 only have access to e-mail, for example, using only a certain set of available protocols for these purposes.

Accounting for the time of work of a particular contractor and a particular department in the network and with 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 for work in the INTERNET that is unreasonable for production needs.

There is no need to divide the network into virtual segments, the network is built without using VLAN technology. Traffic flow for all departments is transparent, differentiation of access rights to information resources is provided by software at the Active Directory level (Windows 2003 Server directory services)

Based on a survey of the existing LAN at the enterprise and in pursuance of the terms of reference, I, as the author of the final qualifying work, have defined a range of tasks that need to be further solved in the final qualifying work:

Include in the existing LAN structure the newly received equipment in 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 uninterruptible power supply of active network equipment,

servers, while using a distributed uninterruptible power supply system. Battery life should be at least 7 minutes.

In addition to the standard configuration, the Master Communications Center UPS is required to support the following additional features:

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

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

The network should provide: file storage and management, network printing; e-mail, optimal collective work with information (databases); backing up server files; backing up network application files (electronic message storage, databases).

There must be one main communication center for the entire network.

Use 3Com products as active network equipment, moreover, the bandwidth of the communication channel with workstations must be at least 100 Mbps, it is necessary to allocate this bandwidth for each workstation (switched network).

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

It is necessary to provide management, monitoring, collection of statistics from active network equipment. The equipment should only be managed in the main communications center.

Tools for effective management of internal network traffic are not required; to manage external Internet traffic, it is necessary to implement a system based 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, use UTP cable to communicate with servers, use UTP cable to communicate with workstations.

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

The number of central servers must be 1.

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

Table 1 - Services and Clients

local area network upgrade

6. Required configuration of the main server:

Processor Type: Server ( Intel Xeon 5140)

Number of processors in the server: 4

The amount of RAM (RAM) server (MB): 4096

Required disk space (TB): 2

Preferred Chassis Type: Intel Server Chassis SC5299-E

Backup Device Required: Spire Spectrum II (1TB)

The number of server communication lines must be equal to 1

The transmission line speed must be 100 Mbps

Uninterruptible power supplies.

Based on the above tasks of upgrading the existing LAN at the enterprise, let's move on to justifying the choice of equipment and equipment communication facilities.

2.2 Trends in the future development of network equipment

Over time, the standards that allowed connecting computers to local networks were gradually optimized, the bandwidth of communication channels increased, the software evolved, and the speed of data transfer grew. Soon, local area networks were used not only to send text and various documents between multiple computers, but also to transfer multimedia information such as sound and images. This opened up the possibility of organizing video conferencing systems within the local network, which allowed users of such a system to communicate in real time “directly”, being physically located in different rooms, perform joint editing of texts and tables, and arrange “virtual presentations”. Already, computer video communication systems are widely used by large commercial enterprises, where they serve to organize communication between various departments, in military complexes for the rapid transfer of information between several subscribers and entire divisions, and more recently in home "desktop" systems, as a means of leisure organization. Among the advantages of KBS, one can mention the relatively low cost of operation compared to other communication systems existing today, their versatility, and relative ease of use. In the course of work, videoconference subscribers generally see the images of the interlocutor and their own on the screens of their monitors, which is necessary for visual control of the established connection.

The steady trend of convergence of local networks with corporate and global networks, which has been outlined in recent years, leads to a significant interpenetration of their technologies (for example, the Internet into a local one). This requires an almost complete replacement of LAN hardware and software. Appendix B lists the main differences between network devices.

Together with the 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.

Prospective development of hardware, cables, adapters, routers, switches, hubs and other network equipment is in the direction of increasing the speed of transmission and processing of information, ensuring 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 stage of design and production include in their equipment the possibility of further improvement by updating the firmware (firmware).

Due to the use of the latest Windows server 2008 operating system in local networks, improved management utilities, connection stability, management of "burial", advanced filtering and data search, multiple selection, record checking, export functions, good fault tolerance of clients are achieved. Windows Server 2008 provides the ability to protect files and folders on NTFS volumes with the encrypted EFS file system.

2.3 Rationale for the choice of equipment for network modernization

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

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

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 forward packet fragments on collisions or error packets 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 medium, but internal blocking slows them down 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 fragments of packets to the destination when collisions occur. Routers store the entire packet in their memory before forwarding it to the destination, therefore, when using routers, packets are transmitted with a delay. Routers can provide bandwidth equal to the bandwidth of the link, but they are characterized by the presence of 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 the loopback interface, the loopback device does not talk to itself.

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

I chose 3Com due to the good reviews about the equipment of this manufacturer, and also due to the fact that during the production of their equipment they supply 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, then 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 communications with each other. In a network with 3Com equipment, speed is increased thanks to traffic compression technology. Hubs of the Switch type were chosen as switching devices, since they not only transmit the packet to the destination port, unlike hubs that only 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, devices such as Switch can significantly offload the network from unnecessary traffic, since, unlike hubs, the received signal is transmitted strictly to the destination port, and is not duplicated to all ports.

Equipment in the case of complex construction of a turnkey network is better to purchase from one supplier, since:

First, the supply of equipment 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 a new network construction project as much as possible;

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

Based on the terms of reference and having discussed all the details with a representative of the supplier, 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 when choosing, equipment of an above-average class was used, which was quite functional and of high quality, moreover, with a margin of + 30% to existing jobs, the project turned out to be relatively inexpensive even by today's standards. It remains only to configure the workstations after installing the network and connecting the final network equipment. Table 2 below shows the configuration of network settings for user computers.

Table 2 - Network parameters of computer network users

Main gateway - the address of a computer that is designed to organize access for computer network users to the Internet. Main server - Central server with the Microsoft Windows 2008 Server Enterprise Edition operating system (Appendix D) installed on it network services Active Directory, DNS Server, File Server, etc. In this case, it is specified as a network parameter, because when the client computer logs on, it needs to have a DNS server running on the network that can resolve hostnames to their network addresses, which also acts as a domain controller. The primary DNS server, unless it is also an Internet gateway, is capable of resolving only 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 of the organization. It is registered as a network parameter of the user's computer, as it is able to resolve its requests for name resolution to external resources, to the Internet.

Once the central server, Internet gateway, and client computers have been configured, the network is ready to go.

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

Currently, LAN hardware of various sizes is subject to requirements for increased reliability, fault tolerance, recoverability after failures, high throughput and load capacities, 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 next generation, these requirements are met by manufacturers hardware. However, development does not end there, but only begins.

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 is already there, 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 the established and proven technologies X.25, Frame Relay, FDDI, ATM, Ethernet are now more widespread, undoubtedly, they find application in certain niches and wireless access technologies. Moreover, in some cases, only wireless technologies will be able to provide access where there are no technical conditions for wired ones or simply there will be 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 to provide customers with "mobility", which is extremely convenient. The main disadvantage is the vulnerability to intruders.

At the moment, three standards 802.11a, 802.11b and 802.11g are presented on the Russian market.

11b - equipment this standard Supports transfer rates 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 up to 22 Mbps.

11g is a more advanced standard that has increased the degree of protection and data transfer rate up to 54 Mbps. 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 a network adapter of the 802.11g standard was previously purchased, then you can be absolutely sure that you can work with it in the 802.11b standard network.

Both of the standards listed above 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 be able to simultaneous connection many clients. Those. this standard allows you to expand the density in relation to 802.11g. The second most significant difference is the frequency of the radio wave - 5GHz. It is precisely because of the frequency that this standard cannot be used on the territory of the Russian Federation without special permission. (Eng. Worldwide Interoperability for Microwave Access) is a telecommunications technology designed to provide a 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, also called Wireless MAN. The name "WiMAX" was created by the WiMAX Forum, an organization that was founded in June 2001 to promote and develop 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." Suitable for:

Point connections WiFi access with each other and other segments of the Internet.

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

Provision of high-speed data transmission and telecommunication services.

Creation of 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 “backbone channels”, which are continued by traditional DSL and leased lines, as well as local networks. As a result, this approach allows you to create scalable high-speed networks within entire cities.

Problem last mile has always been an urgent task for communication operators. To date, many last mile technologies have appeared, and any telecom operator faces 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 scope, 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 investments in network development and their payback period,

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

the time required to launch the network and start 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 evaluate the economic parameters of using WiMAX technology

Many telecommunications companies are betting heavily on the use of WiMAX to provide high-speed communications services. And there are several reasons for this.

Firstly, 802.16 family technologies will make it possible to cost-effectively (compared to wired technologies) not only provide access to the network to new customers, but also 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 is very useful when you need 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 Aceh, Indonesia. The entire communication infrastructure of the region was put out of action and the prompt restoration of communication services for the entire region was required.

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

2.5 Development and implementation of elements of modernization of LAN network equipment LLC "Torg-Service"

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

Studies have shown that in order to solve the tasks set in the terms of reference (Appendix A) and fulfill 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 blanks and a protective front panel. Selected Tower (Rack) (5U) chassis certified by the motherboard manufacturer.

A high-speed DVD-ROM drive will not only save time when installing the OS and application software (SW), 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 arriving at the server.

To provide additional reliability, two network cards were used 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, export function. server 2008 provides reliable protection of files and folders on volumes, provides network scalability.

Appendix E presents an option for upgrading the network at the request of the customer: including three mobile places 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 use laptop computer, from anywhere in the world where you have access to world wide web. This method It is advisable to use a virtual network organization in cases of geographically unattached access of employees to the organization's local network through Internet access. Often, providers create VPN connections for their customers to provide access to Internet resources.

The so-called Extranet VPN, when access is provided to the organization's clients through secure access channels, is gaining wide acceptance due to the popularity of e-commerce. In this case, remote clients will be very limited in their ability to use the local network, in fact, they will be limited to accessing those company resources that are necessary when working with their clients, for example, a website with commercial offers, and the VPN is used in this case to securely forward confidential data. Information security tools - encryption protocols built into the computer of the remote access client.

Encapsulation of data 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 Internet connection. It should be noted that when designing networks, the VPN server is placed last.

In Windows Server 2008, installing the VPN Server role is fairly straightforward.

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

Following the prompts of the wizard in Figure 2, install:

at 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;

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

at 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 settings have been made, we proceed to manage the users of our domain. For employees who need remote access to the organization's internal network, we allow this very 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 dialog box of the server setup wizard

WITH server part finished, let's move on to creating the client part of the network on a remote computer.

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

at the first step, start the network connection wizard;

at the second step, following the prompts, select the item "Connect to the network at the workplace";

in the third step "Connecting to a local network";

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

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

at the sixth step, enter the IP address of the server to be accessed (see Figure 4);

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

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 a VPN. The method described in this final qualification work is good in that 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 performance. Let's start traditionally, with everyone's favorite "ping" command, just try to "ping" some workstation from our upgraded local network (Figure 5).

Everything works fine, it remains to measure the performance of the created network. To do this, we will copy the file through the VPN connection, and also, without using it, to the VPN server. A 100 Mbit network will act as a physical transmission medium, in this case the network bandwidth 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 transferring information through a VPN, additional overhead costs appear 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 loss in time will also vary. At present Microsoft time recommends using the L2TP IPSec protocol with smart cards for maximum authentication and communication security.

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

Below (in Figure 6) is a screenshot of the call to the "Traffic Inspector" program. It should be concluded that a survey of the operation of the equipment of the LAN operating at Torg-Service LLC was carried out and the tasks were solved: developing a scheme for an upgraded network, including three mobile workstations in the scheme, justifying the choice and installation of a modern Windows server 2008 operating system on the central LAN server , VPN server to implement the upgraded scheme LAN networks, pilot operation of the upgraded 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 the conclusions of a practical survey of the local area network operating at the service trade enterprise Torg-Service LLC, the following was carried out:

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

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

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

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

A practical scheme for the modernization of an existing LAN is proposed, with a justification for the choice of network equipment and an operating system in pursuance of the terms of reference of the network user, Torg-Service LLC.

The first chapter of the work shows that the network equipment of the local area 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, universal LAN data transmission medium; server cabinets, connectors, cross panels are protocol-independent equipment.

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

Chapter 2 noted that many of today's networking devices combine a whole set of functions. For example, a modern ADSL modem, in addition to the function of communicating with the ISP provider's network, is capable of performing the functions of a firewall (firewall), router and a simple network filter. At the same time, the cost of such a modem does not go beyond the cost of a middle-class modem.

If earlier network administration was solved by specially developed complex software that was installed on computers, now it has become possible through the use of modern compact desktop devices or in rack-mount format, which are excellent at solving certain tasks, be it VLAN - switches, firewalls, complex network protection equipment, carrier-class equipment (multiplexers, interface converters, modular switches, etc.).

In many cases, manufacturers already at the production stage put into their equipment the possibility of improvement by updating the firmware (firmware). This can significantly reduce the total cost of ownership of equipment, as there is no need to throw out the old device and buy a new one with the release of next-generation equipment. It is enough just to download and install the update, and the device acquires additional functionality, support for new protocols and improved operation algorithms.

Access technologies are constantly developing, already now there is a huge number of solutions on the market for providing access using various technologies: wired and wireless. Moreover, it is not necessary that wired and wireless access technologies compete with each other. Each of them has its own niche, its own scope. On the contrary, in the case of building complex and extended 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.

Completion of this chapter of the 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 area networks. The main directions of development of network equipment are as follows:

increase in the throughput of communication channels;

increase in data transfer speed between ports in network devices;

expansion of the total bandwidth;

reduction of delays when packets pass through the ports of active equipment;

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

development of new promising access technologies;

development of more convenient and modern means and management methods for network equipment.

In the practical part of the WRC, Chapter 3, the development and implementation of the modernization of the network equipment of the existing LAN at the service trade enterprise Torg-Service LLC is presented as part of the "Terms of Reference for the implementation of the technical part of the project for the modernization of the local area network operating at the enterprise":

new equipment for testing mortgages and components and PCs was connected;

operating room installed Windows system server 2008, instead of Windows server 2003;

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

Glossary

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home

Network equipment for local network

the site offers services for installing and configuring network equipment for a local network of various scales and various topologies

01

Components of a network

LAN network equipment includes network switches, access points, network cards, print servers, repeaters, splitters, cable systems and trays, as well as many other devices on the basis of which communication can be organized via data network channels.

the site offers its services for the selection of this type of equipment, as well as further technical support and warranty service.

• > minimum possible deadlines
• > network stability
• > possibility of further modernization
• > economic profitability
• > maximum disclosure of the capabilities of network equipment
• > easy maintenance

02

Help website specialists

Our team brings together highly qualified professionals, thanks to many years of experience which, in a short time, many different projects of local networks based on the equipment offered on the site were implemented. We not only have our own vision for each of the particular cases of network infrastructure, but also carefully listen to the individual wishes of our customers. As a result, this quintessence of professional knowledge and techniques, as well as a highly individualized approach, help us create LAN projects that meet all six main quality criteria:

03

Our services

Site specialists offer whole line services related to network equipment for a local area network, the list of which can be found below:

• > determination and preparation of the site for the installation of network equipment (planning cold and hot aisles, laying raised floors, ensuring a reliable ventilation system and power supply systems)
• > planning a local network (in particular, its scale, choice of topology)
• > selection of passive network equipment (cables, connectors, cable trays and cabinets, sockets, etc.)
• > further technical support of the local network

• > selection of active network equipment (the required number of switches with the required number of ports, access points and a set of antennas (if necessary, organizing WIFI), as well as auxiliary devices, such as print servers, repeaters, etc.
• > direct connection of network equipment for local network
• > setting up network equipment and combining it into a local network
• > repair and replacement of network components due to a malfunction
• > modernization of the local network and its expansion

04

Principles for choosing network equipment for a local network

Let's decide what should be guided by when choosing network equipment for a local network. First of all, it's a manufacturer. The following manufacturers of network equipment for the local area network are represented on the site.

"You can purchase the necessary network equipment for the local network in the store at . Our experts will help you make the most correct choice and suggest the main features of each of the models under consideration.

If the considered model of network equipment for a local area network is not currently available on the site, we suggest contacting the manager to clarify the possibility of purchasing it on order. "

05

Allied Telesis is a manufacturer of networking equipment for small and medium businesses offering the widest range of network switches (managed, smart and unmanaged), media converters (LC, ST, SC standards and Fast Ethernet or Gigabit Ethernet ports) and PCI network cards. From Allied Telesis, you can find options that are powerful enough for high-performance environments with increased load levels, as well as energy-efficient options that are characterized by reduced power consumption.

06

Linksys offers network switches and access points, the functionality of which is almost identical to the capabilities of much more expensive analogs from Cisco. The key difference is the focus on small and medium businesses, and, consequently, the lower price of these devices. Devices from Linksys are highly reliable, and also more versatile than their “brothers” from Cisco.

07

TRENDnet - the products of this manufacturer are notable for their low cost and high quality of service. On the site you can find network switches, access points and WIFI antennas from TRENDnet. Note that almost all products of this brand are energy efficient and cause minimal harm to the environment.

08

Ubiquiti is a well-known and very popular manufacturer of network equipment for organizing local networks in the Russian Federation. The vast majority of Ubiquiti hotspots are capable of multi-mode operation (eg point-to-point/point-to-multipoint) and transmit data hundreds of kilometers thanks to polling support (as a decent and more efficient alternative to WIFI).

09

Zyxel - developments of this manufacturer are distinguished by high reliability and versatility. Although this is not the cheapest product, but with the correct configuration, a local network based on devices from Zyxel will work without repeated interventions in the configuration for many years.

10

Mikrotik - Latvian manufacturer of network equipment Mikrotik produces high-quality devices for building local networks, the configuration of which is accessible even for non-professionals. Note that devices with basic functionality can be easily upgraded by purchasing additional licenses. This approach significantly reduces the cost of upgrading the network.

13

Maximum compliance with network parameters from the site

However, it is the website specialists who will help you make the right choice. In view of a detailed acquaintance with the technical description of each of the products posted on the site, as well as with the basic principles for selecting network equipment, the site professionals will offer you a choice of several models that are most suitable for your requirements. It is likely that a complete set of network equipment for organizing a local area network will contain devices from different manufacturers - since this approach will ensure maximum compliance with network parameters and client requests. Such solutions are absolutely suitable for further modernization and scaling, as well as supplementing with equipment from third-party manufacturers that are not presented on the site.