Technology Basics
3-12
Token Ring
This new frame passes through the network to reach the station which originally
formulated the request, and it builds its own routing database by reversing the
order of the bridge identifications in the Routing Information Field of the frame.
From this point on, the two stations can transmit frames which tell the bridges in
the network what route they need to take.
Because this routing information takes up space in a frame and in the routing
database of each end station, there is a finite number of bridges whose
identifications can be included in the Routing Information Field of a Token Ring
frame. This translates directly into a limitation on the number of bridges that may
be designed into a Token Ring network. An IEEE 802.5 compliant Token Ring
network may contain no more than 14 rings, connected by no more than 13
bridges.
Routers
A Token Ring router performs the same function as an Ethernet router. It provides
for the interconnection of two or more Token Rings, and transmits frames
between them based on more detailed information than is required by bridges.
This more in-depth information allows routers to be more discerning and precise
with regard to the exchange of frames, but forces them to operate slightly slower
due to the time involved in the examination.
The use of a router or series of routers is the only way to “reset” the 13 bridge rule
described in the Bridges section of this chapter (above).
NOTE
In order for a network to be IBM Token Ring compatible, it must
contain no more than eight rings and no more than seven bridges
in its longest path.
Summary of Contents for MMAC-5FNB
Page 1: ...Cabletron Systems Networking Guide MMAC FNB Solutions ...
Page 2: ......
Page 4: ...ii ...
Page 10: ...viii ...
Page 188: ...Expansion Ethernet 8 12 Port Assignment and Virtual LANs ...
Page 194: ...Expansion Token Ring 9 6 Port Assignment ...