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1、網(wǎng)絡(luò)教程——局域網(wǎng)和局域網(wǎng)交換大連理工大學(xué)網(wǎng)絡(luò)中心局域網(wǎng)和局域網(wǎng)交換局域網(wǎng)概述以太網(wǎng)分段局域網(wǎng)交換和虛網(wǎng)生成樹協(xié)議局域網(wǎng)和局域網(wǎng)交換——局域網(wǎng)概述MAC地址以太網(wǎng)標(biāo)準(zhǔn)快速以太網(wǎng)局域網(wǎng)概述目前三種主要類型的局域網(wǎng)是以太網(wǎng),令牌環(huán)和FDDI。IEEE定義了這三種局域網(wǎng)的大部分標(biāo)準(zhǔn)。局域網(wǎng)標(biāo)準(zhǔn)NameMACSublayerSpecLLCSublayerSpecOtherCommentsEthernetversion2(DIXEthernet)EthernetNotapplicableThisspeci
2、sownedbyDigital,Intel,andXerox.IEEEEthernetIEEE802.3IEEE802.2Alsopopularlycalled802.3Ethernet.TokenRingIEEE802.5IEEE802.2IBMhelpeddevelopmentbeforetheIEEEtookover.FDDIANSIX3T9.5IEEE802.2ANSIliked802.2,sotheyjustrefertotheIEEEspec.局域網(wǎng)頭格式PreambleDest.A
3、ddressSourceAddressTypeDataFCSEthernet(DIX)PreambleDest.AddressSourceAddressLengthDataFCSIEEEEthernetSDDSAPSSAPControlACDest.AddressSourceAddressEDDataFCSIEEETokenRingFDDSAPSSAPControlSDFSSDDest.AddressSourceAddressEDDataFCSANSIFDDIFCDSAPSSAPControlP
4、reambleFS86variable2471662111-2variable4802.311166111-2variable411802.2802.3802.5802.2802.541166111-2variable4.51.5FDDIMAC802.2FDDI最大幀大小,除前導(dǎo)碼以外:以太網(wǎng):1518bytes令牌環(huán):4472bytes(4MB)17,800bytes(16MB)FDDI:4472bytes(4MB)MAC地址MAC地址的一個主要的功能就是區(qū)分或標(biāo)識以太網(wǎng),令牌環(huán),和FDDI局
5、域網(wǎng)上的接口卡。VendorCode(24bits)MACAddressMostSignificantByteLeastSignificantByteEthernet——MostSignificantBitislastTokenRing——MostSignificantBitisfirstMAC地址廣播地址——0xFFFF.FFFF.FFFF。廣播地址可以讓局域網(wǎng)上的所有設(shè)備接收到同一個幀。組播地址——在以太網(wǎng)和FDDI中使用??梢宰尵钟蚓W(wǎng)上的部分是設(shè)備接收到同一個幀。在IP組播中也使用組播地址
6、。功能地址——只在令牌環(huán)上使用。功能地址區(qū)分一個或多個接口提供的特定功能。以太網(wǎng)標(biāo)準(zhǔn)StandardMaximumCableLengthTypeofCableMACSublayerSpecificationDeviceconnectstoaHuborDirectlytoaBus10B5500m50Ohmthickcoaxialcable802.3Bus10B2185m50Ohmthincoaxialcable802.3Bus10BT100mUTP802.3Hub10BTL2000mFiber80
7、2.3Hub100BTx100mUTP/STP802.3Hub100BT4100mUTP,4pair802.3Hub100BFx400mFiber802.3Hub半雙工和全雙工以太網(wǎng)操作HubNICNICNICNIC2-PairCableReceivePairTransmitPairTransmitReceiveCollision?Loopback12234455510BTHalf-DuplexOperation網(wǎng)卡發(fā)送一個幀。網(wǎng)卡將幀回送到自己的接收對。Hub接收到幀。Hub在內(nèi)部總線上傳遞幀
8、。Hub將信號從每個設(shè)備的接收對送出。半雙工和全雙工以太網(wǎng)操作Full-DuplexNICFull-DuplexNICReceiveTransmitReceiveTransmit10BTFull-DuplexOperation不會發(fā)生碰撞;所以,時間不會浪費在重傳幀上。不必等其他機器發(fā)送。每個方向都有10M帶寬,增加了可用的帶寬??焖僖蕴W(wǎng)StandardWhatItDefinesTypeofCableMaximumLengthtoHubMaximumDistancebetweenDevices