Floodless in SEATTLE: A Scalable Ethernet Architecture for Large Enterprises

Summary

This paper describes a network architecture that combines the scalability of IP networks with the plug-and-play functionality of ethernet networks. The key idea is to extend ethernet routing to prevent broadcasts and optimize routing. Specifically, the paper proposes a DHT based lookup mechanism. When a node first joins the network it is discovered by the switch to which it is connected. This switch is responsible to adding the node's MAC to the directory. It does this by applying a consistent hash function to the MAC address and determining which switch is responsible for that hash value. The (MAC, location) pair is then stored by the designated switch. When a different host sends a packet, a lookup is preformed in the same manner and the packet is subsequently routed along the shortest path to the destination.

The key aspect of this algorithm is that the directory service eliminates the need for broadcasts, thus making the solution scalable. The network architecture also separates naming from locations, unlike TCP where nodes in a subnet must have a common prefix. This feature allows plug-and-play functionality where nodes do not have to be configured.

Thoughts

Overall, I like the idea; it would certainly be nice to have a large network with no configuration.

Part of the design requires caching directory entries, however, it is not clear how these caches would be invalidated when nodes disconnect from the system of failures occur. Also, I am concerned about the security of the system, it seems that nothing prevents nodes from spoofing MAC addresses or pretending to be switches.