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Description of network topology of the office building
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| Description of network topology of the office building
Network topology (from the Greek. τππος, - place) is a way of describing the network configuration, the layout and connection of network devices. Topology is a scheme for connecting communication channels of computers or network nodes to each other. Network topology can be physical - describes the actual location and connections between network nodes. logical - describes the movement of the signal within the physical topology. informational - describes the direction of information flows transmitted over the network. exchange management is the principle of transferring the right to use the network. There are many ways to connect network devices. The following topologies are distinguished: fully connected cellular common bus star ring snowflake 1) Fully connected topology is the topology of a computer network in which each workstation is connected to all the others. This option is cumbersome and inefficient, despite its logical simplicity. An independent line should be allocated for each pair, each computer should have as many communication ports as there are computers in the network. For these reasons, the network can only have relatively small final dimensions. Most often, this topology is used in multi-machine complexes or global networks with a small number of workstations. The access technology in the networks of this topology is implemented by the token transfer method. A token is a packet equipped with a special sequence of bits (it can be compared to a letter envelope). It is successively transmitted in a ring from computer to computer in one direction. Each node retransmits the transmitted token. The computer can transfer its data if it has received an empty token. The token with the packet is transmitted until the computer to which the packet is intended is found. In this computer, data is received, but the token moves on and returns to the sender. After the computer that sent the packet makes sure that the packet has been delivered to the addressee, the token is released. Disadvantage: cumbersome and inefficient option, because each computer must have a large number of communication ports. 2) Mesh topology is a basic fully connected topology of a computer network in which each workstation of the network connects to several other workstations of the same network. It is characterized by high fault tolerance, complexity of configuration and excessive cable consumption. Each computer has many possible ways to connect to other computers. A cable break will not cause the connection between the two computers to be lost. It is obtained from a fully connected one by removing some possible connections. This topology allows the connection of a large number of computers and is typical, as a rule, for large networks. 3) A common bus is a common cable (called a bus or trunk) to which all workstations are connected. There are terminators at the ends of the cable to prevent signal reflection. Dignities: Short network installation time; Cheapness (requires less cable and network devices); Easy to set up; The failure of the workstation does not affect the operation of the network. Disadvantages: Network problems, such as cable breakage and terminator failure, completely block the operation of the entire network; Complex fault localization; With the addition of new workstations, network performance decreases. Bus topology is a topology in which all LAN devices are connected to a linear network data transmission environment. Such a linear medium is often referred to as a channel, bus, or track. Each device, for example, a workstation or a server, is independently connected to a common bus cable using a special connector. The bus cable must have a matching resistor or terminator at the end, which absorbs the electrical signal, preventing it from being reflected and moving in the opposite direction along the bus. 4) Star is the basic topology of a computer network in which all computers of the network are connected to a central node (usually a switch), forming a physical segment of the network. Such a network segment can function both separately and as part of a complex network topology (as a rule, a "tree"). The entire exchange of information goes exclusively through the central computer, which is assigned a very heavy load in this way, so it cannot do anything else except the network. As a rule, it is the central computer that is the most powerful, and it is on it that all the exchange management functions are assigned. No conflicts in the network with the star topology are in principle impossible, because management is completely centralized. The access method is implemented using Arcnet technology. This access method also uses a token to transmit data. The token is passed from computer to computer in ascending order of the address. As in the ring topology, each computer regenerates a marker. Advantages: the failure of one workstation does not affect the operation of the entire network as a whole; good network scalability; easy troubleshooting and interruptions in the network; high network performance (subject to proper design); flexible administration options. Disadvantages: failure of the central hub will result in the network (or network segment) inoperable as a whole; laying a network often requires more cable than most other topologies; the finite number of workstations in a network (or network segment) is limited by the number of ports in the central hub. 5) A ring is a topology in which each computer is connected by communication lines with only two others: it only receives information from one, and only transmits it to the other. On each communication line, as in the case of a star, only one transmitter and one receiver work. This allows you to abandon the use of external terminators. The work in the ring network consists in the fact that each computer retransmits (resumes) the signal, that is, acts as a repeater, because the attenuation of the signal in the entire ring does not matter, only the attenuation between neighboring ring computers is important. There is no clearly defined center in this case, all computers can be the same. However, quite often a special subscriber is allocated in the ring, which manages the exchange or controls the exchange. It is clear that the presence of such a managing subscriber reduces the reliability of the network, because its failure immediately paralyzes the entire exchange. Computers in the ring are not completely equal (unlike, for example, bus topology). Some of them necessarily receive information from the computer that is transmitting at this moment, earlier, and others - later. It is on this feature of the topology that the methods of managing exchange over the network, specially designed for the "ring", are built. In these methods, the right to the next transfer (or, as they say, to capture the network) passes sequentially to the next computer in a circle. Connecting new subscribers to the "ring" is usually completely painless, although it requires a mandatory shutdown of the entire network for the duration of the connection. As in the case of the "bus" topology, the maximum number of subscribers in the ring can be quite large (1000 or more). The ring topology is usually the most resistant to overloads, it ensures reliable operation with the largest flows of information transmitted over the network, because there are usually no conflicts in it (unlike the bus), and there is also no central subscriber (unlike the star). In the ring, unlike other topologies (star, bus), a competitive method of sending data is not used, a computer on the network receives data from the previous one in the list of recipients and redirects them further if they are not addressed to him. The list of recipients is generated by a computer that is a token generator. The network module generates a token signal (usually of the order of 2-10 bytes to avoid attenuation) and transmits it to the next system (sometimes in ascending order of the MAC address). The next system, having received the signal, does not analyze it, but simply passes it on. This is the so-called zero cycle. The subsequent algorithm of operation is as follows — the GRE data packet transmitted by the sender to the addressee begins to follow the path laid out by the marker. The packet is transmitted until it reaches the recipient. Dignities: Easy to install; Almost complete absence of additional equipment; The possibility of stable operation without a significant drop in data transfer speed during heavy network load, since the use of a token eliminates the possibility of collisions. Disadvantages: The failure of one workstation, and other problems (cable breakage), affect the performance of the entire network; Complexity of configuration and configuration; The complexity of troubleshooting. The need to have two network cards on each workstation. 6) Snowflake (Hierarchical Star or tree topology) is a star-type topology, but several concentrates are used, hierarchically interconnected by star-type connections. The "snowflake" topology requires a shorter cable length than the "star", but more elements. жүктеу/скачать 91,22 Kb. Достарыңызбен бөлісу:
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