B O S T O N   U N I V E R S I T Y
                                       
                      Computer Science Department
                                       
                         C O L L O Q U I U M

          Duality Model of TCP and Queue Management Algorithms

                            Steven Low

                  California Institute of Technology

                           Wednesday, June 20
			        1:00 pm
                       (Coffee served at 12:45 am)
                         Seminar Room / MCS 135


 We describe a duality model of TCP congestion controls.
 Congestion control is the interaction of source rates
 with certain congestion measures in the network. 
 The basic idea is to regard source rates as primal
 variables and congestion measures as dual variables,
 and congestion control a Lagrangian method that iterates 
 on source rates and congestion measures to maximize 
 aggregate source utility subject to a capacity constraint.
 In TCP, the primal iteration is carried out by source
 algorithms such as Reno or Vegas, and the dual iteration
 is carried out by queue management such as DropTail, RED
 or REM. We present these algorithms and derive their 
 utility functions.  Finally, we linearize the duality
 model and use that to illustrate the (in)stability of 
 TCP as network scale up in delay and capacity.

Host: John Byers
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