A linear system analysis of RED

James Aweya, Michel Ouellette, Delfin Y. Montuno

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


The random early detection (RED) algorithm proposed by Floyd and Jacobson [IEEE/ACM Trans. Networking 1 (4) (1993) 397] is a simple and quite effective mechanism for active queue management and as a result has been widely implemented in Internet routers. While RED certainly performs better than drop-tail, its parameters are difficult to tune to give good performance under different congestion scenarios. Also, studies have shown that RED does not stabilize the queue lengths in routers, because its equilibrium queue length strongly depends on the number of active TCP connections. As a result numerous variants of RED have been proposed to work around the performance problems of RED. In this paper, using inferences drawn from a linear systems analysis, we provide an insight into why RED is difficult to tune. The same linear systems analysis is used to show that the DRED algorithm proposed in [Computer 36 (2-3) (2001) 203; Comput. Commun. 24 (12) 2001 1170] overcomes the performance limitations of RED [IEEE/ACM Trans. Network. 1 (4) (1993) 397].

Original languageBritish English
Pages (from-to)1736-1750
Number of pages15
JournalComputer Communications
Issue number18
StatePublished - 1 Dec 2002


  • Active queue management
  • Congestion control
  • Control theory
  • Random early detection
  • TCP


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