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

6.3. Source Routing Concepts

We know it's difficult, but try to temporarily put aside everything you learned in the previous chapters. None of the concepts of transparent bridges apply to a source-routed environment. Table 6-1 provides a summary of the differences between transparent and source routing bridges.

Table 6.1. Summary of Differences between Transparent and Source Route Bridging

CHARACTERISTIC	TRANSPARENT BRIDGING	SOURCE ROUTE BRIDGING
Transparency	Bridges and multiple LANs are transparent to end stations. All end stations appear to each other to be on the same LAN. No end station difference between bridged and non-bridged traffic.	Bridges and multiple rings are exposed to end stations. End stations know which other stations on the same versus different rings. End stations send frames differently to versus bridged stations.
Topology knowledge	Address table and port mappings are learned and maintained by bridges.	Routes are learned and maintained by end stations.
Frame format	Unchanged by bridging.	Route information is inserted in frames.
Frame forwarding	Bridges make all forwarding decisions. No end station involvement.	End stations make all forwarding decisions. Bridges follow end station instructions.
Bridge mode	Promiscuous; bridges intercept all traffic on all ports.	Bridges only intercept frames carrying source routing information.
Data Link operation	Connectionless or connection-oriented.	Connection-oriented.
Link utilization	All traffic follows the single spanning tree. Links not in ...