Network switchAvayaERS 2550T-PWR50-port network switchAnetwork switch(sometimes known as aswitching hub) is acomputer networking devicethat is used to connect devices together on acomputer network, by using a form ofpacket switchingto forward data to the destination device. A network switch is considered more advanced than ahubbecause a switch will only forward a message to one or multiple devices that need to receive it, rather than broadcasting the same message outof each of its ports.[1]A network switch is a multi-portnetwork bridgethat processes and forwards data at thedata link layer(layer 2) of theOSI model. Switchescan also incorporateroutingin addition to bridging; these switches are commonly known aslayer-3ormultilayer switches.[2]Switches exist for various types of networks includingFibre Channel,Asynchronous Transfer Mode,InfiniBand,Ethernetand others. The first Ethernet switch was introduced byKalpanain 1990.[3]OverviewCisco small businessSG300-28 28-port Gigabit Ethernet rackmountswitch and its internalsA switch is a device used on acomputer networkto physically connect devices together. Multiple cables can be connected to a switch to enable networked devices to communicate with each other. Switches manage the flow of data across a network by only transmitting a received message to the device for which the message was intended. Each networked device connected to a switch can beidentified using aMAC address, allowing the switch to regulate the flow of traffic. This maximises security and efficiency of the network.Because of these features, a switch is often considered moreintelligent than anetwork hub. Hubs neither provide security, or identification of connected devices. This means that messages have to be transmitted out of every port of the hub, greatly degrading the efficiency of the network.Network designAn Ethernet switch operates at the data link layer of theOSI modelto create a separatecollision domainfor each switch port. Each computerconnected to a switch port can transfer data to any of the other ones at a time, and the transmissions will not interfere with the limitation that, inhalf duplexmode, each line can onlyeitherreceive fromortransmit to its connected computer at a certain time. Infull duplexmode, each linecan simultaneously transmitandreceive, regardless of the partner.In the case of using arepeater hub, only a single transmission could take place at a time for all ports combined, so they would all share the bandwidth and run inhalf duplex. Necessary arbitration would also result in collisions requiring retransmissions.ApplicationsThe network switch plays an integral part in most modernEthernetlocal area networks(LANs).Mid-to-large sized LANs contain a number of linkedmanagedswitches.Small office/home office(SOHO) applications typically use a single switch, or an all-purposeconverged devicesuch as aresidential gatewayto access small office/homebroadbandservices such asDSLorcable Internet. In most of these cases, the end-user device contains arouterand components that interface to the particular physical broadband technology. User devices may also include a telephone interface forVoice over IP(VoIP) protocol.MicrosegmentationSegmentation is the use of a bridgeor a switch (or a router) to split a larger collision domain into smallerones in order to reduce collision probability and improve overall throughput. In the extreme, i. e. microsegmentation, each device is located on a dedicated switch port. In contrast to an Ethernet hub, there is a separate collision domainon each of the switch ports. This allows computers to have dedicatedbandwidth on point-to-point connections to the network and alsoto run in full-duplex without collisions. Full-duplex mode has only one transmitter and one receiver per collision domain, making collisions impossible.Role of switches in a networkSwitches may operate at one or more layers of theOSI model, including the data link and network layers. A device that operates simultaneously at more than one ofthese layers is known as amultilayer switch.In switches intended for commercial use, built-in or modular interfaces make it possibleto connect different types of networks, includingEthernet,Fibre Channel,ATM,ITU-TG.hnand802.11. This connectivity can be at any of the layers mentioned. While layer-2 functionality is adequate forbandwidth-shifting within one technology, interconnecting technologies such asEthernetandtoken ringis easier at layer 3.Devices that interconnect at layer 3are traditionally calledrouters, so layer-3 switches can also be regarded as (relatively primitive) routers.Where there is a need for a great deal of analysis of network performance and security, switches may be connected between WAN routers as places for analytic modules. Some vendors providefirewall,[4][5]networkintrusion detection,[6]and performance analysis modules that can plug into switch ports. Some of these functions may be on combined modules.[7]In other cases, the switch is used tocreate a mirror image of data that can go to an external device. Since most switch port mirroring provides only one mirrored stream,network hubscan be useful for fanning out data to several read-only analyzers, such asintrusion detection systemsandpacket sniffers.
Posted on: Thu, 11 Sep 2014 16:03:03 +0000
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