Source routing bridges

• CSMA/CD community preferred to use transparent bridges due to their simplicity.
• The Token Ring community, however, preferred source routing bridges.
• In source routing, the sending station knows whether the destination is on the same network. If it is not, the sender sets the higher destination address bit to 1 and includes the exact path to the frame header.
• The path is a sequence of alternating bridge and LAN addresses (4bits/12bits).
• This requires that each machine know the topology and can construct a path to any receiver.
• Instead, the sender first broadcasts a discovery frame asking the receiver to signal himself. In the return trip bridges record their addresses in the frame header and the path is formed.

• Problem: Too many frame loose in the network.