The All-New Switch Book: The Complete Guide to LAN Switching Technology, Second Edition

6.7. IEEE Standards and Source Routing

There is no IEEE standard for a pure source routing bridge. Considerable work was done in this area within the IEEE 802.5 (Token Ring) Working Group, but the project was never completed, and no draft was ever approved or officially published.

The only mention of source route bridging within the IEEE LAN standards is in the form of the SRT bridge discussed in section 6.6.3. SRT bridging was incorporated into the IEEE 802.1D bridge standard in 1993, as the result of a joint IEEE 802.1/802.5 Task Force effort.^[] Thus, all standards-compliant bridges must include transparent bridge capability, along with the Spanning Free Protocol. This is the "T" part of the SRT bridge. In a standards context, source routing is an optional enhancement to a transparent bridge.

^[] Rich was a member of that joint Task Force.

Of course, pure source routing bridges are available from many suppliers, and have been widely deployed in Token Ring LANs. They are much more common than their officially approved SRT counterparts. Source routing in its pure form is specified by IBM, an organization that, at least in the Token Ring world, is more important than the IEEE.