Rbridges: transparent routing

Abstract

This work describes a method of interconnecting links that combines the advantages of bridging and routing. The basic design is a replacement for a transparent bridge and makes no assumption about higher layer protocols. It involves creating an infrastructure of switches (which we call Rbridges, for "routing bridges") in which packets are routed, although, as with bridges, layer 2 end code location is learned through receipt of data packets. It avoids the disadvantages of bridges, since packets within the infrastructure need not be confined to a spanning tree, and packets are protected with a hop count and not proliferated while in transit, so there is no need for any artificial startup delay on ports to avoid temporary loops. This allows IP nodes to travel within a multi-link campus without changing IP addresses. The paper introduces further optimizations for IP, such as avoiding hooding ARP messages through the infrastructure, and (for IP nodes), allowing Rbridges to avoid learning on data packets.