复旦大学：《计算机网络 Computer Networking》课程教学资源（PPT课件讲稿）Token-Ring Networks

Token-Ring Networks Chapter 4a Panos Boodo Business Data Networks and telecommunications 6th edition Copyright 2007 Prentice-Hall May only be used by adopters of the book

Token-Ring Networks Chapter 4a Panko’s Business Data Networks and Telecommunications, 6th edition Copyright 2007 Prentice-Hall May only be used by adopters of the book

Figure 4a-1: Ring Network Wrapped Ring Access Unit Main ring Backup Ring Token Break=n了 StP or UTP 1. Frames travel around the ring The ring is a dual ring 2. If a trunk line between Normally, the backup ring is not used access units breaks The ring is wrapped Computer Computer A Computer C so the loop is restored 2

2 Figure 4a-1: Ring Network STP STP or UTP Main Ring Backup Ring Break Wrapped Ring Access Unit Token Computer A Computer B Computer C Computer E Computer D 1. Frames travel around the ring. The ring is a dual ring. Normally, the backup ring is not used. 2. If a trunk line between access units breaks, The ring is wrapped, so the loop is restored

)802.5 Token-Ring Network Created about the same Time as ethernet Standardized as 802.5 16 Mbps maximum speed Token Passing Media Access Control Special token frame circulates around the ring when no station is transmitting When a station gets the token, it may transmit a frame When a station finishes sending the frame it releas es the token oken Passing is Complex and Expensive 802.5 quickly lost out to Ethernet

3 802.5 Token-Ring Network • Created about the Same Time as Ethernet – Standardized as 802.5 – 16 Mbps maximum speed • Token Passing Media Access Control – Special token frame circulates around the ring when no station is transmitting – When a station gets the token, it may transmit a frame – When a station finishes sending the frame, it releases the token • Token Passing is Complex and Expensive – 802.5 quickly lost out to Ethernet

Figure 4a-2: Early Ethernet Bus Topology N (1)Transmitted Signal (3)Received Signa Trunk cable (2)Trans ceiver Broadcasts Signal in Both Directions(Bus Transmission)

4 Figure 4a-2: Early Ethernet Bus Topology NIC NIC (1) Transmitted Signal (3) Received Signal (2) Transceiver Broadcasts Signal in Both Directions (Bus Transmission) Trunk Cable

Figure 4a-3: FDDI Backbone Network 16 Mbps 10 Mbps 802.5 Netw ork 802. 3 Netw ork 100 Mbps FDDI Backbone netw ork 16 Mbps 802.5 Netw ork tOMb 802.3 Netw ork Fiber Distributed Data Interface(FDDI) was a 100 Mbps token ring network technology that could spans tens of kilometers This made it an ideal backbone network to connect 10 Mbps ethernet networks and 16 mbps 802.5 Token - Ring networks As Ethernet grew to 100 Mbps and faster fddi became obsolete and was discarded

5 Figure 4a-3: FDDI Backbone Network 10 Mbps 802.3 Netw ork 10Mbps 802.3 Netw ork 16 Mbps 802.5 Netw ork 100 Mbps FDDI Backbone Netw ork 16 Mbps 802.5 Netw ork Fiber Distributed Data Interface (FDDI) was a 100 Mbps token ring network technology that could spans tens of kilometers This made it an ideal backbone network to connect 10 Mbps Ethernet networks and 16 Mbps 802.5 Token-Ring networks As Ethernet grew to 100 Mbps and faster, FDDI became obsolete and was discarded

I Perspective Ring Topologies are Desirable The ability to be wrapped is vital where high reliability is important The SoNET/SDH carrier technology discussed in Chapter 7 and Module C uses a ring topology However, Token Passing is not necessary with Switched Networks Just as CSMa/Cd is not necessary in switched Ethernet networks

6 Perspective • Ring Topologies are Desirable – The ability to be wrapped is vital where high reliability is important – The SONET/SDH carrier technology discussed in Chapter 7 and Module C uses a ring topology • However, Token Passing is Not Necessary with Switched Networks – Just as CSMA/CD is not necessary in switched Ethernet networks