Equilibrium and Dynamics of TCP/AQM

Tuesday, August 7, 2001 - 1:30pm - 2:30pm
Keller 3-180
Steven Low (California Institute of Technology)
Congestion control of the Internet is performed by TCP protocol at traffic sources in concert with active queue management (AQM) algorithms at network links. We interprete TCP/AQM as carrying out a distributed primal-dual algorithm over the Interenet to maximize aggregate source utility. Different protocols correspond to different optimization algorithms to solve the same prototype problem with different utility functions, and we derive these utility functions explicitly. We describe a linear model to study the dynamics of the system around equilibrium. It suggests that the current protocol will become unstable (oscillatory) as delay or capacity increases. We propose a scalable protocol that maintains stability for arbitrary delay, capacity and routing.

(Joint work with John Doyle (Caltech) and Fernando Paganini UCLA)).