A hybrid active queue management for stability and fast adaptation

Changhee Joo, Saewoong Bahk, Steven S. Lumetta

Research output: Contribution to journalArticlepeer-review


The domination of the Internet by TCP-based services has spawned many efforts to provide high network utilization with low loss and delay in a simple and scalable manner. Active queue management (AQM) algorithms attempt to achieve these goals by regulating queues at bottleneck links to provide useful feedback to TCP sources. While many AQM algorithms have been proposed, most suffer from instability, require careful configuration of non-intuitive control parameters, or are not practical because of slow response to dynamic traffic changes. In this paper, we propose a new AQM algorithm, hybrid random early detection (HRED), that combines the more effective elements of recent algorithms with a random early detection (RED) core. HRED maps instantaneous queue length to a drop probability, automatically adjusting the slope and intercept of the mapping function to account for changes in traffic load and to keep queue length within the desired operating range. We demonstrate that straightforward selection of HRED parameters results in stable operation under steady load and rapid adaptation to changes in load. Simulation and implementation tests confirm this stability, and indicate that overall performances of HRED are substantially better than those of earlier AQM algorithms. Finally, HRED control parameters provide several intuitive approaches to trading between required memory, queue stability, and response time.

Original languageEnglish (US)
Pages (from-to)93-104
Number of pages12
JournalJournal of Communications and Networks
Issue number1
StatePublished - Mar 2006


  • Active queue management (AQM)
  • Random early detection (RED)
  • Response time
  • Stability

ASJC Scopus subject areas

  • Information Systems
  • Computer Networks and Communications


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