A Policy-aware Switching Layer for Data Centers; Joseph, Tavakoli, & Stoica

This paper describes PLayer, a policy-aware switching layer for data centers. PLayer is meant to help combat the problems posed by middleboxes (e.g. firewalls) and having equivalent logical and physical network topologies. With middleboxes that are hard-wired into the physical network, any rerouting of traffic due to server failures could bypass the middlebox, meaning that behavior is not reliable.

PLayer separates the notions of policy from reachability, meaning that traffic goes through middleboxes as expected by data center policy, not just as network mechanisms allow. Additionally, middleboxes are taken off the physical network data path, with traffic forwarded to them via a policy-aware pswitch. Pswitches contain switch and policy cores; as the authors point out, minimal hardware change is required for PLayer to actually be adopted in data centers.

However, it's not clear from the paper how these switches would be acquired, if DC owners would have to hack their own together. The authors themselves developed a software implementation of the pswitches using Click. They simulated use of the pswitches on a small collection of topologies and found through the use of simple micro-benchmarks that their software prototype incurred an increase in latency and decrease in throughput. Despite this degrading performance, use of pswitches offers guarantees that middleboxes will be traversed as desired even in the presence of network churn.