Congestion Control for System Area Networks

Congestion is an important issue in the design of SANs (e.g., Infiniband), as in any computer network. Typical SAN switches use link-level flow control to avoid dropping packets. While this eliminates the well-known congestion collapse phenomenon, it can cause congestion spreading or tree saturation, where one bottleneck link causes traffic to block throughout the network. Congestion control has been widely studied in the literature. However, this problem needs to be reevaluated in the context of SAN environments due to their unique characteristics (e.g., small bandwidth-delay product, input port buffering, small switch buffers).

We have developed and evaluated a new congestion control scheme for SANs. Our approach couples a simple switch-based ECN packet marking mechanism appropriate for typical SAN switches with small input buffers, together with hybrid window and rate control at end-devices. Our approach and many of our ideas are being adopted in the congestion management protocol being developed for InfiniBand.

Papers and Reports

• Jose Renato Santos, Yoshio Turner, G. (John) Janakiraman, "End-to-End Congestion Control for InfiniBand," Infocom 2003, April 2003, San Francisco, CA.
• Jose Renato Santos, Yoshio Turner, G. (John) Janakiraman, "Evaluation of Congestion Detection Mechanisms for InfiniBand Switches," IEEE Globecom 2002 High-speed Networking Symposium, November 2002, Taiwan (also Tech. Rep. HPL-2002-224, HP Laboratories, August 2002).
• Jose Renato Santos, Yoshio Turner, G. (John) Janakiraman, "End-to-end Congestion Control for System Area Networks," Tech. Rep. HPL-2002-4 (R.1), HP Laboratories, May 2002.
• Yoshio Turner, Jose Renato Santos and G. (John) Janakiraman, "An Approach for Congestion Control in InfiniBand," Tech. Rep. HPL-2001-277 (R.1) , HP Laboratories, May 2002.

Presentations

• "End-to-End Congestion Control for System Area Networks," presentation at HPL Computer Sciences Colloquium series, June 2003, Palo Alto, CA.
• "End-to-End Congestion Control for InfiniBand," presentation at Infocom 2003, April 2003, San Francisco, CA.
• "Evaluation of Congestion Detection Mechanisms for InfiniBand Switches," presentation at IEEE Globecom 2002 High-speed Networking Symposium, November 2002, Taiwan.
• "InfiniBand Congestion Control - HP Proposal," presentation of our approach to the Link Working Group of the InfiniBand Trade Association, August 2001.