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 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 releases the token Token Passing is Complex and Expensive 802.5 quickly lost out to Ethernet

Figure 4a-2: Early Ethernet Bus Topology

Figure 4a-3: FDDI Backbone Network 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

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