In this paper, we evaluate the performance of both real and virtual queue-based marking schemes designed for use at routers in the Internet. Using fluid flow models, we show via analysis and simulations that Virtual Queue (VQ)-based marking schemes outperform Real Queue (RQ)-based marking schemes in terms of robustness to disturbances and the ability to maintain low queueing delays. In fact, we prove that a linearized model of RQ-based marking schemes exhibit a lack of robustness to constant but otherwise unknown levels of disturbances. The analytical results we present are applicable to combinations of proportionally fair and TCP-type congestion controllers at the source, and Random Exponential Marking (REM) and Proportional Control (PC) schemes at the router. The behavior of Random Early Discard (RED) and Proportional-Integral (PI) control schemes at the router are also studied via simulations.

Original languageEnglish (US)
Pages (from-to)81-93
Number of pages13
JournalIEEE/ACM Transactions on Networking
Issue number1
StatePublished - Feb 2005


  • Active Queue Management
  • Congestion control
  • Fluid-flow analysis

ASJC Scopus subject areas

  • Software
  • Computer Science Applications
  • Computer Networks and Communications
  • Electrical and Electronic Engineering


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