network protocols handbook.pdf

199Protocols GuideLAN - Ethernet ProtocolsProtocol NameGigabit (1000 Mbps) Ethernet:IEEE 802.3z (1000Base-X) and 802.3ab (1000Base-T)and GBICProtocol DescriptionEthernet protocols refer to the family of local-area network (LAN)covered by the IEEE 802.3 standard. The Gigabit Ethernet protocolis based on the Ethernet protocol but has tenfold speedincrease over Fast Ethernet, using shorter frames with carrierExtension. It is published as the IEEE 802.3z and 802.3ab supplementsto the IEEE 802.3 base standards.Carrier Extension is a simple solution, but it wastes bandwidth.Packet Bursting is “Carrier Extension plus a burst of packets”.Burst mode is a feature that allows a MAC to send a short sequence(a burst) of frames equal to approximately 5.4 maximum-lengthframes without having to relinquish control of themedium.The Gigabit Ethernet standards are fully compatible with Ethernetand Fast Ethernet installations. They retain Carrier SenseMultiple Access/ Collision Detection (CSMA/CD) as the accessmethod. Full-duplex as well as half duplex modes of operationare supported, as are single-mode and multi mode fiber andshort-haul coaxial cable, and twisted pair cables. The GigabitEthernet architecture is displayed in the following figure:802.3z1000 BaseLXFiber OpticSingle-Modeor MultimodeFiberMAC full Duplex and/or Half duplexGigabit Media Independent Interface (GMII) (Optionsl)1000 BASEX PCS8B/108 Auto-Megotiation1000 BaseSXFiberMultimodeFiber1000 BaseCXCopperShieldedCopperCableFigure 2-11: Gigabit Ethernet Protocol Stack1000 BaseTPCS1000 BsaeIPMAUnshieldedTwisted PairIEEE 802.3z defines the Gigabit Ethernet over fiber and cable,and has the physical media standard 1000Base-X (1000BaseSX– short wave covering up to 500m, and 1000BaseLX – longwave covers up to 5km). The IEEE 802.3ab defines the GigabitEthernet over the unshielded twisted pair wire (1000Base-Tcovers up to 75m).The Gigabit interface converter (GBIC) allows network managersto configure each gigabit port on a port-by-port basis forshort-wave (SX), long-wave (LX), long-haul (LH), and copperphysical interfaces (CX). LH GBICs extend the single-mode fiberdistance from the standard 5 km to 10 km.Protocol Structure1000Base-X has a minimum frame size of 416bytes, and1000Base-T has a minimum frame size of 520bytes. An extensionfield is used to fill the frames that are shorter than the minimumlength.7 1 6 6 2Pre SFD DA SALengthType46=< n=