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1、100 Mbps Fast Ethernet,Section Objectives,Upon completion of this section, you will be able to: Summarize the features of Fast Ethernet Summarize 100BASE-T4, 100BASE-TX, and 100BASE-FX implementations Recognize back pressure frames in a trace Attach Sniffer Pro to your Fast Ethernet networks Use the
2、 Sniffer Pro statistics and decodes to locate areas of concern,Overview of Fast Ethernet,100Mbps version of the Ethernet standard Uses the same timing criteria as 10 Mbps Ethernet 100BASE-Tx supports Category 3,4 and 5 twisted-pair wiring and fiber cabling Standard defined by IEEE 802.3u Many switch
3、es and hubs combine 10 Mbps and 100 Mbps ports to link legacy networks into high speed backbones,Remote Router,Workgroup LANs,Workgroup,Hubs/Switches,Router,Campus,10/100 Mbps Hubs,and Switches,Network Center,10/100 Mbps Switches,Firewall,Router,Router,Hub,Remote LAN,Faster Server Links,Token Ring,W
4、here to Deploy Fast Ethernet,WAN,Fractional T1,T1, X.25,Frame Relay,Similarities between 10BASE-T and 100BASE-T,Both use CSMA/CD Frame formats and frame lengths are the same Both can run on Category 3, 4 and 5 UTP It must be four-pairs for 100BASE-T to run on 3 and 4 Interconnections are made with h
5、ubs, repeaters, switches, etc.,100BASE-T Features,100BASE-T transmits ten times as much data in the same amount of time It has new PHY standards The network design is more compact The interframe gap is .96 microseconds instead of 9.6 microseconds It is still 96 bit times for 10/100/100, the times ju
6、st get shorter as the speed increases Coding schemes 4B5B and 8B6T replace Manchester encoding,Physical Layer Specifications,100BASE-TX: Fast Ethernet for Category 5 UTP Most widely used physical layer specification for 100BASE-T today 100BASE-T4: Fast Ethernet for CAT3 UTP Use when you have a large
7、 installed base of voice grade wiring Requires four wires of the cable Not implemented very often, so there is very little vendor support for it 100BASE-FX: Fast Ethernet for Fiber Optic Cabling Used in sites that are considering fiber cabling or have it installed Usually used between floors of a bu
8、ilding,100BASE-TX for Category 5 UTP,Transmission over two pairs of Category 5 UTP or IBM Type 1 STP wire RJ-45 connector is exactly the same as that used by 10-BASE-T where the RJ-45 links two pairs of wires The punchdown blocks in the wiring closet must be Category 5 certified Traditional DB-9 con
9、nector used for STP wiring 4B5B coding,Operates over four pairs of Category 3, 4, or 5 UTP wiring Three pairs are used for transmission and the fourth wire is used for collision detection Since it can run on Category 3, provides for easier migration to 100BASE-T without rewiring Three of the four pa
10、irs are used to transmit or receive, so full-duplex operation is not possible 8B6T coding,100BASE-T4 for Category 3 UTP,100 Base T Ethernet Pinouts,Pin Signal Wire Color,1 2 3 4 5 6 7 8,Transmit 3 Receive 3 Transmit 2 Receive 1 Transmit 1 Receive 2 Transmit 4 Receive 4,EIA/TIA-T568A,white/green gree
11、n/white white/orange blue/white white/blue orange/white white/brown brown/white,1 2 3 4 5 6 7 8,Transmit 2 Receive 2 Transmit 3 Receive 1 Transmit 1 Receive 3 Transmit 4 Receive 4,white/orange orange/white white/green blue/white white/blue green/white white/brown brown/white,Pin Signal Wire Color,AT
12、&T 258A and EIA/TIA-568B,RJ45,100BASE-FX for Fiber Optic Cabling,Operates over two strands of multimode or singlemode fiber cabling (just like FDDI) Fiber optic media transmits over greater distances than UTP; useful for connections between interconnect devices on a Fast Ethernet backbone Uses the M
13、IC, ST or SC fiber connectors defined for FDDI and 10BASE-FX networks 4B5B coding,4B5B Encoding Technique (100BASE-FX and 100BASE-TX ),Upper layer protocols send data in 8 bit bytes The MAC driver splits the bytes into 4 bit nibbles A look-up table is used to convert the 4-bit nibble to a 5-bit symb
14、ol or symbol code Clocking information is carried within the data stream 100BASE-FX uses a two-state NRZI signal A change in signal level represents a binary code-one; no signal level change represents a binary code-zero,ULP MAC PHY,8 bit bytes,4 bit nibbles,5 bit symbols,100BASE-TX uses MLT-3 terna
15、ry signaling Any signal change in TX is represented by circulating among three progressive levels: (+1, 0,-1, 0, +1, 0,-1, 0 .) Hex 1F to 4B5B: 1 maps to 01001, F maps to 11101 A transition = binary 1; No transition = binary 0 Transition order: +1 0 -1 0 +1 0 -1 0 endlessly,+1 0 -1,0,1,0,0,0,1,1,1,1
16、,1,No transition present, so this is a binary 0,Transition present, so this is a binary 1,1,F,4B5B Ternary Example,8B6T Encoding Technique (100BASE-T4),Based on a ternary symbol - meaning it may take on one of three values: 1,0 or -1 also represented as +, 0 or - Each byte is mapped to a 6 bit-time ternary code symbol, called a 6T symbol (i.e., to represent 1F, the 6T code group is 0 - + 0 + -) A lookup table is
