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.
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 network 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.
In the modern market of computer equipment and technology, LAN network equipment, including personal computers, is represented by a great variety of different types, modifications, 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 related to computer technology to constantly monitor market fluctuations and analyze 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 fulfilling the terms of reference for the modernization of the existing LAN at the service trade enterprise Torg-Service LLC, where I had an internship, 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.
Define the structure and functions of a local area network (LAN) model, an abstract network model, development 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.
Research methods in the final qualification work are the analysis of scientific literature, the 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 to ensure the compatibility of information support (programs and data) in terms of the 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 collaboration 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.
Level 6 (submissions) reference model OSI is usually an intermediate protocol for translating information from adjacent 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 the application network programs serving 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.
NIC, also known as network card, network adapter, Ethernet adapter, NIC (network interface controller) - a peripheral device that allows a computer to interact with other network devices. 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 a 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 in any this 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 the NE1000/NE2000 series Novell, and also quite a few in the late 1980s there were Soviet clones of network cards with a BNC connector, which were produced with various Soviet computers and separately.
The network adapter (Network Interface Card (or Controller), NIC), together with its driver, implements the second, channel level of the open systems model in the 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 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, functions remote control computer, 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 connect networks. 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 a local network to a 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 Linux kernels) with which you can turn your PC into a high-performance and multifunctional router, such as 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 some 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 into a common 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 the general transmission medium. 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 from the general environment by a hub, and in the second case several devices are connected using one cable segment, and, in the case of a large number collisions, the hub can 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(PC) 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) for general access and organizing distributed databases. 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 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 LAN structure must be quite specific, for example, the most popular link layer protocol - Ethernet - is designed for parallel connection of all network nodes to a common bus for them - a piece of coaxial cable. . The Token Ring protocol is also designed for a 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. Token ring from IBM describes the star topology, when all computers are connected to one central device (English multistation access unit (MSAU)), while IEEE 802.5 does not focus on the 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.
Main advantages Fast technology Ethernet 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- cheap alternative 100BASE-FX using multimode fiber because 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 a 10BASE-FL network and those who do not need to work over long distances.
BASE-BX is a variant of Fast Ethernet over single-core fiber 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. The maximum segment length is 15 kilometers in full duplex mode over one single-mode optical fiber at a wavelength of 1310 nm and 1550 nm. 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 pairs: on the one hand, the transmitter is 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 FDDI networks are divided into several types according to the following features: end stations or concentrators; 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 technology virtual networks Switches perform two tasks at the same time:
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 to 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 the maintenance of technical means of a local network operating since 2006 at the enterprise, 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 implementation of 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 according to user requests software products for broadcasters, promotional 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, provide employees of the enterprise, according to their qualifications and position, with prompt and high-quality access to LAN resources, as well as to global resources. INTERNET networks. 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, uniting 20 computers, corresponds to the structure 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. And 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. The movement of traffic for all departments is transparent, the differentiation of access rights to information resources is provided by software at the level Active Directory(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 shutdown 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); backup 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 volume 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 different 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 hardware and software tools LAN. Appendix B lists the main differences between network devices.
Together with rapidly developing and in demand in all spheres of human activity network technologies the development and production of hardware and software 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 service periods, 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 the equipment used in the selection was above average, sufficiently 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 of computer network users to the Internet. Main server - Central server with the Microsoft Windows 2008 Server Enterprise Edition (Appendix D) operating system installed on it, Active Directory network services, DNS Server installed on it , File Server, etc. In this case, it is specified as a network parameter, because when a client computer logs on, it needs to have a running DNS server 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. Serve customer requests outside internal network it is not able to. The server is optional - in this case, it is both the Internet gateway and the organization's proxy server. 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 a single node and the entire network as a whole. . With each subsequent generation, these requirements are met by hardware manufacturers. However, development does not end there, but 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 for wired there will be no technical conditions 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 Russian Federation, which cannot be said about 802.11a.
11a is a standard similar to 802.11g, but designed to allow multiple clients to connect at the same time. 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:
Connections of Wi-Fi access points 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 WiFi 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.
The problem of the last mile has always been an urgent task for signalmen. 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.
First, the 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, using a portable computer, from anywhere in the world where there is access to the World Wide Web. It is advisable to use this method of organizing a virtual network 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, the possibilities for using the local network will be greatly reduced for remote clients, in fact, they will be limited to access to those company resources that are necessary when working with their clients, for example, a site with commercial offers, and VPN is used in this case 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 domain network, running Windows Server 2008. The server has two network interfaces with IP addresses, internal for the local network 11.7.3.1 and external 191.168.0.2 for connecting to the Internet. It should be noted that when designing networks, the VPN server is placed last.
In Windows Server 2008, installing the VPN Server role is 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 choose 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 to 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 the 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 the ways VPN applications so many. 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 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. Microsoft currently recommends the use of L2TP IPSec 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 scheme of the upgraded LAN network, trial 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), a 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 designed complex software that was installed on computers, now it has become possible through the use of modern compact desktop devices or in rackmount 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 tools and methods for managing 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;
mounted operating system Windows 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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the latest frame-switched networking technology that provides high-speed data transmission by sending data cells (fixed-size frames) over broadband local and wide area networks. |
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several buildings within the same organizational structure, located in a limited area. |
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network topology, which is based on the transfer around the circle of the marker that determines the direction of data transfer. |
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telecommunications technology designed to provide universal long-range wireless communications for a wide range of devices |
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Subscriber cable |
connection cable used to connect equipment in the work area. |
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connecting element with different types of connectors allowing: - to connect unbalanced cable connectors; - change the sequence (cross adapter) or the number of involved conductors in the connectors; - change the wave impedance (wave adapter). |
specialist responsible for the normal functioning and use of resources automated system and/or computer network |
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Wireless network |
a network that does not use a cable to communicate components. Wireless network channels are laid over the air. Wireless networks are divided into radio networks and infrared networks. |
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global computer network |
a computer network that connects computers that are geographically distant over long distances from each other. The global network unites local networks. |
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element for transmitting an electronic signal through wires. Any cable consists of metal cores - wires - that conduct electricity. Wire is a kind of electronic signal transmission medium. |
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signal transmission medium between two devices of active equipment, including a line, subscriber and network cables. |
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The local network |
combining subscriber, network and peripheral equipment of a building or a complex of buildings using physical (cable system) and radio channels in order to share hardware and network resources and peripheral devices. |
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Highway |
a set of physical telecommunication channels between distribution points (telecommunication terminals - am. standard) inside the building and between buildings. |
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router |
a network device that, based on information about the network topology and certain rules, makes decisions about forwarding network layer packets (layer 3 of the OSI model) between different network segments. |
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Main gate |
the address of a computer that is designed to organize access for users of a computer network to the Internet. |
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computer or software system that provide remote access to their services or resources for the purpose of exchanging information. Typically, communication between a client and a server is maintained through message passing, using a specific protocol to encode client requests and server responses. |
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Network card, also, Ethernet adapter |
A peripheral device that allows a computer to communicate with other devices on a network. |
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Network hardware |
devices necessary for the operation of a computer network, for example: router, switch, hub. Usually distinguish between active and passive network equipment. |
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network hub |
a network device designed to combine multiple Ethernet devices into a common network segment. |
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Telecommunications |
transmission and reception of electromagnetic signals or any information via wires, radio and other channels |
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LAN equipment is a solid list of various interrelated elements and devices necessary for the operation and. First of all, these are network servers, workstations, routers, communicators, cables, bridges. All this and much more in general ensures a highly productive and uninterrupted functioning of the network, so it cannot be said that one or another equipment for a local network is more important than another.
IN professional environment It is customary to single out several of the most important key nodes of a local computer network:
Flylink specialists will develop and
Introduction
Chapter I Theoretical basis network building
Topology of computer networks
A ring is a topology in which each computer is connected by communication lines to only two others: it only receives information from one, and only transmits information to the other. The ring topology is shown in Figure 1.
Figure 1 - Ring topology
On each communication line, as in the case of a star, only one transmitter and one receiver operate. This eliminates the need for external terminators. The work in the ring network is that each computer retransmits (resumes) the signal, that is, acts as a repeater, therefore the signal attenuation in the entire ring does not matter, only the attenuation between neighboring computers of the ring is important. In this case, there is no clearly defined center, all computers can be the same. However, quite often a special subscriber is allocated in the ring, which controls the exchange or controls the exchange. It is clear that the presence of such a control subscriber reduces the reliability of the network, because its failure immediately paralyzes the entire exchange.
Star - the basic topology of a computer network (Figure 2), in which all computers in the network are connected to a central node (usually a switch), forming a physical network segment.
Figure 2 - Star Topology
Such a network segment can function both separately and as part of a complex network topology (usually a "tree"). The entire exchange of information goes exclusively through the central computer, which in this way has a very large load, so it cannot do anything other than the network. As a rule, it is the central computer that is the most powerful, and it is on it that all the functions of managing the exchange are assigned. No conflicts in a network with a star topology are in principle impossible, because management is completely centralized.
A bus is a common cable (called a bus or backbone) to which all workstations are connected. There are terminators at the ends of the cable to prevent signal reflection. The bus topology is shown in Figure 3.
Figure 3 - Bus topology
Network equipment
Network equipment - devices necessary for the operation of a computer network, for example: a router, switch, hub, patch panel, etc. Active and passive network equipment can be distinguished.
Active network equipment
This name refers to hardware followed by some "intelligent" feature. That is, a router, a switch (switch), a flexible multiplexer, etc. are active network equipment. On the contrary, a repeater (repeater)] and a concentrator (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 hubs are active network equipment, as they can be endowed with some kind of “intellectual feature”
Passive network equipment
Passive equipment differs from active equipment primarily in that it is not powered directly from the mains and transmits a signal without amplification. Passive network equipment refers to equipment that is not endowed with "intelligent" features. For example, cable system: cable (coaxial and twisted pair), plug/socket (RG58, RJ45, RJ11, GG45), repeater, patch panel, hub, coaxial cable balun (RG-58), etc. Also, passive equipment includes mounting cabinets and racks, telecommunication cabinets. Mounting cabinets are divided into standard, specialized and anti-vandal. By type of installation: wall, floor and others.
Basic network equipment
The main network equipment includes:
The server is a dedicated computer. A server is a computer allocated from a group of personal computers (or workstations) to perform some service task without the direct participation of a person. The server and the workstation may have the same hardware configuration, as they differ only in the participation of the person behind the console in their work.
Some service tasks can run on the workstation in parallel with the user's work. Such workstation conventionally called a non-dedicated server.
Servers need a console (usually a monitor/keyboard/mouse) and human participation only at the initial setup stage, during hardware maintenance and emergency management (normally, most servers are controlled remotely). For emergency situations, servers are typically provided with one console kit per group of servers (with or without a switch, such as a KVM switch).
As a result of specialization (see below), a server solution may receive a simplified console (for example, a communication port), or lose it altogether (in this case, initial configuration and emergency management can only be performed via the network, and network settings can be reset to default state). The server is shown in Figure 4.
Figure 4 - Server
Modem (an acronym made up of the words modulator and demodulator) is a device used in communication systems to physically interface an information signal with its propagation medium, where it cannot exist without adaptation.
The modulator in the modem modulates the carrier signal during data transmission, that is, changes its characteristics in accordance with changes in the input information signal, the demodulator performs the reverse process when receiving data from the communication channel. The modem performs the function of the terminal equipment of the communication line. The very formation of data for the transmission and processing of received data is carried out by the so-called. terminal equipment (a personal computer can also act as its role).
Modems are widely used to connect computers through the telephone network (telephone modem), cable network (cable modem), radio waves (en: Packet_radio, radio relay). Previously, modems were also used in cell phones (until they were supplanted by digital data transmission methods). The modem is shown in Figure 5.
Figure 5 - Modem
Twisted pair (eng. twisted pair) - a type of communication cable, is one or more pairs of insulated conductors twisted together (with a small number of turns per unit length), covered with a plastic sheath.
The twisting of conductors is carried out in order to increase the degree of connection between the conductors of one pair (electromagnetic interference equally affects both wires of the pair) and the subsequent reduction of electromagnetic interference from external sources, as well as mutual interference during the transmission of differential signals. To reduce the coupling of individual cable pairs (periodic convergence of conductors of different pairs), in UTP cables of category 5 and above, the wires of the pair are twisted with different pitches. Twisted pair is one of the components of modern structured cabling systems. It is used in telecommunications and computer networks as a physical signal transmission medium in many technologies such as Ethernet, Arcnet and Token ring. Currently, due to its low cost and ease of installation, it is the most common solution for building wired (cable) local networks.
The cable is connected to network devices using the 8P8C connector (which is mistakenly called RJ45). The twisted pair is shown in Figure 6.
Figure 6 - Twisted pair
Coaxial cable (from Latin co - jointly and axis - axis, that is, "coaxial"), also known as coaxial (from English coaxial), is an electrical cable consisting of a central conductor and a screen located coaxially. Usually used to transmit high-frequency signals. Invented and patented in 1880 by British physicist Oliver Heaviside. The coaxial cable is shown in Figure 7.
Figure 7 - Coaxial cable
Optical fiber - a thread of optically transparent material (glass, plastic) used to transfer light inside itself through total internal reflection.
Fiber optics is a branch of applied science and engineering that describes such fibers. Optical fiber cables are used in fiber optic communications, which allow information to be transmitted over longer distances at a higher data rate than in electronic communications. In some cases, they are also used to create sensors. The optical fiber is shown in Figure 8.
A local network within a company or apartment allows you to combine several devices into a 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.
Network equipment refers to all devices that make up a local area network.
Network equipment can be conditionally divided into two types:
Depending on the structure of the LAN, the hardware configuration required to create it will vary.
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.
The list of other equipment depends on the general structure of the network. 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.
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.
In general, creating a LAN requires the use of several types of equipment:
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 to create a LAN in corporate systems offer other solutions:
There are several big names among network equipment manufacturers. These include companies:
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.
Vendors involved in the supply of telecommunications equipment are divided into three types.
Previously, corporate customers preferred to equip offices with turnkey networks, they turned to the first group of vendors to solve their problems. This significantly saved time, but did not always give them best solutions 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.
Read our other articles:Definition 1
network hardware- devices necessary for the functioning of a computer network.
Network equipment is divided into active And passive equipment.
Active equipment It does not contain electronic circuits that are powered by an electrical network or other sources and perform the functions of amplification, signal conversion, etc. Active equipment processes the signal according to special algorithms. Data transmission in networks occurs in data packets, each of which also contains an additional technical information(information about its source, purpose, integrity of information, etc.), which allows you to deliver the package to its destination. The tasks of active network equipment include not only capturing and transmitting a signal, but also processing this technical information, as a result of which it redirects and distributes incoming streams in accordance with the algorithms built into the device’s memory. It is this feature and mains power that is a sign of active equipment.
Remark 1
Active equipment includes the following types of devices:
Network card, network card, network adapter, Ethernet adapter - an additional device that is installed in a PC and ensures its interaction with other network devices.
In modern PCs and laptops, the controller and components that perform the functions of a network card are mostly already integrated into motherboards. Also exist:
Figure 1 Internal NIC
Figure 2. External network card
Definition 2
concentrator(active hub, multiport repeater) - a network device with $4-48$ ports, which is used to connect a PC to a network using a twisted pair cable.
Hubs also have connectors for connecting to networks based on coaxial cable. Currently supplanted by network switches.
Figure 3
Definition 3
Repeater, repeater– network equipment designed to increase the length network connection by repeating the signal at the physical layer.
There are single port And multiport repeaters.
It differs from the hub in that the repeater has much less delay time, because. it usually has two cable connectors. He does not need to concentrate the signal somewhere and distribute it to other outputs. Multiport repeaters for twisted pair are called network hubs (hubs), and coaxial - repeaters (repeaters).
Figure 4
Definition 4
Bridge– a network device with $2$ ports, which is designed to combine several segments of a computer network into a single network, filters network traffic by parsing network (MAC) addresses.
Figure 5
Definition 5
Switch (switch)- a network device that is designed to combine several nodes of a computer network.
Switches are designed using bridge technology, which is why they are often referred to as multiport bridges. It differs from a hub, which distributes traffic from one connected device to all others, in that it only transmits data directly to the recipient. Thus, network segments that were not intended for data get rid of the need to process them, which, of course, leads to an increase in network performance and security. An exception may be broadcast traffic for all network nodes and traffic for devices whose outgoing switch port is unknown.
Figure 6
Definition 6
Router (router)– specialized network computer, which has $2$ or more network interfaces and forwards data packets between different network segments.
The router allows you to filter network traffic by parsing network ($IP$) addresses. It is mainly used to combine networks of different types, which are often incompatible in architecture and protocols. For example, to combine Ethernet LANs and WAN connections. Often a router is used to provide access from a local network to the Internet. Routers for home use are usually low-port and provide a connection from the PC's home network to the Internet provider's communication channel.
Figure 7
Definition 7
Media converter (media converter)– a network device that converts a signal propagation medium from one type to another. Typically, the signal propagation medium is copper wires and optical cables.
Typically, a media converter has $2$ ports.
Figure 8
Definition 8
network transceiver– a device that is designed to convert the data transfer interface $(RS232-V35$, $AUI-UTP)$. Usually has $2$ ports.
Figure 9
According to some experts, the repeater (repeater) and concentrator (hub) do not belong to active network equipment, because they simply repeat the signal, and do not process it according to certain algorithms. But managed hubs are still active network equipment even with this approach.
Definition 9
Passive network equipment- network equipment that is not powered by the mains or other sources, and is intended to perform the functions of distribution or signal level reduction.
Passive network equipment is:
A structured cabling system (SCS) consists of a set of cables and switching equipment, includes a method of their sharing, which allows you to create regular expandable communication structures in local networks for various purposes. SCS is physical basis building infrastructure, which allows you to bring together a lot of network information services for various purposes into a single system: local computer networks and telephone networks, security systems, video surveillance, etc.
Figure 10.
Patch panel(cross-panel, patch-panel) - a component of the SCS, made in the form of a panel with many connectors, which are located on the front side of the panel. On its back side there are contacts that are designed for a fixed connection with cables and are electrically connected to the connectors.
Figure 11.
Plug/socket ($RG58$, $RJ45$, $RJ11$, $GG45$) Balun for coaxial cables ($RG-58$), etc.
