14. VL2: A Scalable and Flexible Data Center Network

Today's data centers prevent high utilization, according to the authors, by several ways:

• Not providing enough capacity between the servers.
• Congestion and high resource utilization occurs in some of the servers while others are rather lightly-loaded.
• When one service has a traffic load, all other hosts in the same tree/branch suffer collateral damage.
• Lack of easy migration of VLANs.

By measuring network traffic, flow distribution, analyzing traffic matrix and failure characteristics, Virtual Layer 2 (VL2) is introduced to address the above issues. Design:

• Valiant Load Balancing to do random traffic spreading over multiple paths
• Based on IP
• Ability to host any service on any server, separating server names from locators.
• Replaces ARP queries to VL2 directory

Comments:

1. The last 2 papers are both IP-based to achieve backward compatibility, and replaces ARP broadcasts with queries to a specific server. Seems very promising in today's economy: optimal utilization with existing hardware.
2. It's good to see a paper addressing the 144-ports switches and 24-ports from the cost-effective perspective. It's very practical and yet hardly mentioned in "research", which kind of reminds me when I had my master thesis proposal, my advisors laughed at the idea of my mentioning how much can be saved if the technique could be implemented. I guess after working for Microsoft Research, the authors live in a more practical world than most of us bookworms, haha.