Improving the performance of interactive TCP applications using service differentiation

  • Authors:

  • Waél Noureddine;Fouad Tobagi

  • Affiliations:

  • Department of Electrical Engineering, Stanford University, Stanford, CA;Department of Electrical Engineering, Stanford University, Stanford, CA

  • Venue:
  • Computer Networks: The International Journal of Computer and Telecommunications Networking - Special issue: Towards a new internet architecture
  • Year:
  • 2002

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Abstract

Interactive TCP applications, such as Telnet and the Web, are particularly sensitive to network congestion. Indeed, congestion-induced queueing and packet loss can be a significant cause of large delays and variability, thereby decreasing user-perceived quality. We consider addressing these effects using service differentiation, by giving priority to interactive applications' traffic in the network. We study different packet marking schemes and handling mechanisms (packet dropping and scheduling) in the network. For marking packets, two approaches are considered. First, we look into application-based marking, and show how the protection of Telnet traffic against loss can eliminate large echo delays caused by retransmit timeouts, and how, by limiting packet loss for Web page downloads, their delays can be significantly reduced, resulting in enhanced interactivity. Second, we consider differentiation based on TCP state, where we present a marking algorithm that prioritizes packets at the source, based on each connection's window size. In addition, we describe the shaping mechanisms required for conformance to agreements with the network. We show how this marking results in good response times for short transfers, which are characteristic of interactive applications, without significantly affecting longer ones.