A Policy-aware Switching Layer for Data Centers

1. What is the problem? Is the problem real?
Datacenter management is hard and the scale makes errors in configurations inevitable. In addition, there are no explicit protocols or mechanisms to deploy middle-boxes in them resulting in operators overloading existing mechanisms and coming up with ad hoc and error-prone techniques. Unlike in the Internet where people have proposed similar techniques for doing things in a “clean” way when the “clumsy” techniques had sort of become familiar and operational, this paper hits the problem at the right time. Datacenters management is still evolving and admins do make errors. The problem is very real.

2. What is the solution's main idea (nugget)?
The physical network path not the way through which the actual traversal of middle-boxes happen. They introduce a new kind of programmable switch, pswitch, that can take in policies and ensure correct middle-box traversals.

3. Why is solution different from previous work?
Previous papers have not looked at the mess in configuring datacenters, and this paper proposes a neat solution based on the principles of policy and indirection from some well known previous papers (i3, middle-boxes are not harmful) in the context of datacenters. I haven’t read the Ethane paper, so I am not sure what is the exact difference between PLayer and Ethane.

4. Does the paper (or do you) identify any fundamental/hard trade-offs?
There is an increased latency in the network as the pswitch has to look-up the policy for every frame. This is probably fine in largely over-provisioned datacenters that anyway have very small latencies and a small increase is insignificant. With the trend moving towards extracting every cent of investment in the datacenter, dealing with this increased latency might be important.

5. Do you think the work will be influential in 10 years? Why or why not?
As I said earlier, this paper addresses the architectural clumsiness problem of datacenters at the right time, not after people have mastered a clumsy but effective way. Principles in this paper are sure to influence datacenter management.

6. Others:
I have discussed this with Dilip earlier – a user-study with network admins will help in evolving the right language for specifying policies.