1. 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

2. 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

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

4. Figure 4a-2: Early Ethernet Bus Topology

5. 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 Token-Ring networks
As Ethernet grew to 100 Mbps and faster, FDDI became obsolete and was discarded

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