Information Technology Reference
In-Depth Information
6
CHAPTER
Troubleshooting Token Ring
The Token Ring network was originally developed by IBM in the 1970s. It is still IBM's primary
local-area network (LAN) technology, and is second only to Ethernet/IEEE 802.3 in general LAN
popularity. The IEEE 802.5 specification is almost identical to, and completely compatible with, IBM's
Token Ring network. In fact, the IEEE 802.5 specification was modeled after IBM Token Ring, and
continues to shadow IBM's Token Ring development. The term
Token Ring
is generally used to refer to
both IBM's Token Ring network and IEEE 802.5 networks.
Token Ring/IEEE 802.5 Comparison
Token Ring and IEEE 802.5 networks are basically quite compatible, but the specifications differ in
relatively minor ways. IBM's Token Ring network specifies a star, with all end stations attached to a
device called a
multistation access unit
(MAU), whereas IEEE 802.5 does not specify a topology
(although virtually all IEEE 802.5 implementations also are based on a star). Other differences exist,
including media type (IEEE 802.5 does not specify a media type, whereas IBM Token Ring networks
use twisted-pair wire) and routing information field size. Figure 6-1 summarizes IBM Token Ring
network and IEEE 802.5 specifications.
