Review for "VL2: A Scalable and Flexible Data Center Network"

Agility is an important character for the data center networks. However, the structure of today's data center networks prevent agility. More precisely, there are 3 main issues. First, conventional data center networks are hierarchal, which do not provide enough capacity between servers. Second, when hosting multiple services, the data center network is fragile with traffic flood. Once a service has traffic flood, it will have collateral effects on other services.

The VL2 is trying to deal with the limitations of existing data center networks and also provide agility. There are three main goals of VL2: uniform high capacity, performance isolation, layer-2 semantics.

Basically, VL2 is trying to build up a layer 2.5 for the servers’ network. VL2 incorporates with Clos topology and valiant load balancing, which provide extensive path among the servers. By implementing Equal Cost Multipath and OSPF, VL2 can also achieve high scalability.

Previous works like fat-tree and Monsoon, they cannot provide the communication-intensive operations such as data shuffle, whereas VL2 can support these communication spikes. Dcell and BCube cannot be scaled well, whereas VL2 can achieve good scalability.

I think VL2 can be influential in 10 years. It is because VL2 actually solves some vital problem that existing data center networks cannot deal with.