A Scalable, Commodity Data Center Network Architecture

1. What is the problem? Is the problem real?
The common tree-based architecture of switches/routers in datacenters is inefficient and result in oversubscription and relatively low effective bandwidths. This is definitely a real problem, but it would have been nice if the paper had shown some numbers to back it as opposed to just listing some examples.

2. What is the solution's main idea (nugget)?
The paper proposes constructing a fat-tree out of inexpensive, commodity switches that can achieve full bisection bandwidth.

3. Why is solution different from previous work?
The smart thing about this paper is to use the fat-tree topology in the datacenter. Such topologies have been used in the past in super-computers and even telephone networks. Identification of its relevance to datacenters enable them to achieve high bandwidths using cheap commodity switches. Also, unlike most other solutions that increase performance, this thing actually seems to result in reduced power consumption which is a big plus in its favour.

4. Does the paper (or do you) identify any fundamental/hard trade-offs?
This topology makes load balancing harder than before, which have well-known consequences at the transport layer. The paper does talk about a centralized scheduler, but I think in practice, it might be more complicated than what the paper paints. The actual effects with out-of-order delivery etc. need to be checked with realistic workloads.

5. Do you think the work will be influential in 10 years? Why or why not?
Definitely. I think the solution is definitely attractive, has no major complicated requirements and anything that constructs a high performance system out of commodity hardware is bound to be influential. At the very least, the ideas of fat-trees and using commodity hardware for datacenter architectures are here to stay.

6. Others:
As mentioned earlier, I really want to know the bandwidth requirements of the current datacenter applications and whether they are hitting the limit w.r.t. what can be provided. While it does seem like we can always do with more bandwidth, we should ensure we are not solving the wrong problem in datacenters.