Title: A Spectrum of TCP-friendly Window-based Congestion Control Algorithms

Author: Shudong Jin, Liang Guo, Ibrahim Matta, and Azer Bestavros
        {jins, guol, matta, best}@cs.bu.edu

        Computer Science Department
        Boston University

Date: February 2, 2001
      Revised on April 27, 2001
      Posted on July 12, 2001


Abstract:

 This technical report revises BUCS-TR-2001-015 and is a longer version
 of a paper to appear in IEEE/ACM Transactions on Networking.

 The  increased  diversity of  Internet  application requirements  has
 spurred  recent  interests   in  transport  protocols  with  flexible
 transmission  controls. In  window-based congestion  control schemes,
 increase rules  determine how  to probe available  bandwidth, whereas
 decrease  rules  determine  how  to  back  off  when  losses  due  to
 congestion are detected.  The parameterization of these control rules
 is done so  as to ensure that the  resulting protocol is TCP-friendly
 in terms of the relationship between throughput and loss rate.

 In this  paper, we define  a new spectrum of  window-based congestion
 control algorithms  that are  TCP-friendly as well  as TCP-compatible
 under RED.  Contrary to previous memory-less controls, our algorithms
 utilize  history information  in  their control  rules. Our  proposed
 algorithms have two salient features:  (1) They enable a wider region
 of TCP-friendliness,  and thus more flexibility in  trading off among
 smoothness, aggressiveness, and responsiveness; and (2) they ensure a
 faster  convergence  to  fairness   under  a  wide  range  of  system
 conditions.  SIMD is one instance  of this spectrum of algorithms, in
 which  the congestion  window is  increased super-linearly  with time
 since the detection  of the last loss. Compared  to recently proposed
 TCP-friendly  AIMD  and   binomial  algorithms,  we  demonstrate  the
 superiority of SIMD in: (1) adapting to sudden increases in available
 bandwidth,    while    maintaining    competitive   smoothness    and
 responsiveness;   and  (2)   rapidly  converging   to   fairness  and
 efficiency.

Keywords:
 Congestion Control, TCP-friendly, Fairness, Convergence.