CCNA1_M8_Ethernet_Switching (1130704)

Просмтор этого файла доступен только зарегистрированным пользователям. Но у нас супер быстрая регистрация: достаточно только электронной почты!

Текст из файла

CCNA – Semester1Module 8Ethernet SwitchingObjectives••••Define bridging and switching.Explain Spanning-Tree Protocol (STP).Collision domains and broadcast domainsData flow and network segmentationEthernet SwitchingSegmentationLayer 2 Bridging• When a frame comes, bridge check the source addresswith the MAC table– If there was a mapping between the source address and thereceiving port, then ignores– Else, update MAC table with the source address and thereceiving port• Bridge check the destination address with the MACtable– If the destination address is in the MAC table, then forward theframe to the associated port– If the destination address is unknown, multicast or broadcast,then forward the frame to all other ports except the receivingport.Layer 2 Switching• Rather than creating two collision domains,each port creates its own collision domain(micro-segmentation).• A switch dynamically builds and maintains aContent-Addressable Memory (CAM) table,holding all of the necessary MAC information foreach port.Switch CAM Table• Operations that might have been done in software as inbridge can now be done in hardware using an applicationspecific integrated circuit (ASIC).Switch benefits• Provide micro-segmentation• Double bandwidth betweennodes• Collision-free transmission• Two 10- or 100- Mbps datapath• Allow multiple circuitssimultanouslyLatency• Latency is the delay between the time a frame firststarts to leave the source device and the time thefirst part of the frame reaches its destination.Factors that cause delay are:– Media delays.– Circuit delays.– Software delays.– Delays caused by the content of the frame and wherein the frame switching decisions can be made.Switching methods• Store-and-forward:–––The entire frame is received before forward.Increases latency with larger frames.Error detection is high.• Cut-through:–––Immediately forward a packet after checking the destinationaddress.No error checkingOffers the lowest level of latency• Fragment-free switching:––Forwards a packet after receiving the first 64 bytes.Filters out collision packets (size < 64 bytes)Forwarding DecisionSwitch Mode• With cut-through methods of switching, both the sourceport and destination port must be operating at the samebit rate in order to keep the frame intact.

This is calledsynchronous switching.• If the bit rates are not the same, the frame must bestored at one bit rate before it is sent out at the other bitrate. This is known as asynchronous switching. Storeand-forward mode must be used for asynchronousswitching.Switching modesSwitching LoopadBro!tormStc as• When multiple switches are designed with redundantpaths to provide for reliability and fault tolerance in asimple hierarchical tree, switching loops are unlikely tooccur.Spanning-Tree Protocoleramst FacadBroStandby Link• Main function of the Spanning Tree Protocol(STP) is to allow redundantswitched/bridged paths without sufferingthe effects of loops in the networkSpanning Tree Protocol••A switch sends special messages called bridge protocol data units(BPDUs) out all its ports to let other switches know of its existence.The switches use a spanning-tree algorithm (STA) to resolve and shutdown the redundant pathsCollision Domains andBroadcast DomainsShared Media Environments••It is important to be able to identify a shared media environment,because collisions only occur in a shared environment.Some networks are directly connected and all hosts share Layer 1Collisions in collision domainCollision Domain Segmentation• The types of devices that interconnect the media segmentsdefine collision domains.Round-Trip Delay• The 5-4-3-2-1 rule also provides guidelines to keep roundtrip delay time in a shared network within acceptable limits.Segmenting a collision domain with bridge• Segmentationincreases theopportunity for eachhost in the network togain access to themedia.• This effectivelyreduces the chance ofcollisions andincreases availablebandwidth for everyhost.Broadcasts in Bridged Environment••Layer 2 devices forward broadcast and if excessive, canreduce the efficiency of the entire LAN.Broadcasts must be controlled at Layer 3, as Layer 2 andLayer 1 devices cannot.Router• Routers actually work at Layers 1, 2, and 3.• A router (layer 3 device) solves the problem of too muchbroadcast traffic.• It is Layer 3 that allows the router to segment broadcastdomains or “network”.Broadcast Domain SegmentationData FlowsSummary•••••Layer 2 bridging and switchingContent-addressable memory (CAM)Switching methodsSpanning-Tree Protocol (STP)Collisions, broadcasts, collision domains, andbroadcast domains• Layer 1, 2, and 3 devices with collision domainsand broadcast domains• Data flow.

Характеристики

Тип файла PDF

PDF-формат наиболее широко используется для просмотра любого типа файлов на любом устройстве. В него можно сохранить документ, таблицы, презентацию, текст, чертежи, вычисления, графики и всё остальное, что можно показать на экране любого устройства. Именно его лучше всего использовать для печати.

Например, если Вам нужно распечатать чертёж из автокада, Вы сохраните чертёж на флешку, но будет ли автокад в пункте печати? А если будет, то нужная версия с нужными библиотеками? Именно для этого и нужен формат PDF - в нём точно будет показано верно вне зависимости от того, в какой программе создали PDF-файл и есть ли нужная программа для его просмотра.

Список файлов учебной работы