Normalized queueing delay: Congestion control jointly utilizing delay and marking

Mingyu Chen, Xingzhe Fan, Manohar N. Murthi, T. Dilusha Wickramarathna, Kamal Premaratne

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Depending upon the type of feedback that is primarily used as a congestion measure, congestion control methods can be generally classified into two categories: marking/loss-based or delay-based. While both marking and queueing delay provide information about the congestion state of a network, they have been largely treated with separate control strategies. In this paper, we propose the notion of the normalized queueing delay, which serves as a congestion measure by combining both delay and marking information. Utilizing normalized queueing delay (NQD), we propose an approach to congestion control that allows a source to scale its rate dynamically to prevailing network conditions through the use of a time-variant set-point. In ns-2 simulation studies, an NQD-enabled FAST TCP demonstrates a significant link utilization improvement over FAST TCP under certain conditions. In addition, we propose another NQD-based controller D + M TCP (Delay+Marking TCP) that achieves quick convergence to fair and stable rates with nearly full link utilization. Therefore, NQD is a suitable candidate as a congestion measure for practical congestion control.

Original languageEnglish (US)
Pages (from-to)618-631
Number of pages14
JournalIEEE/ACM Transactions on Networking
Issue number2
StatePublished - 2009


  • Congestion control
  • Explicit Congestion Notification (ECN)
  • High-speed networks
  • TCP
  • Transport protocols
  • Window flow control

ASJC Scopus subject areas

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


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