M.C. Weigle, D. Vembar, and Z. Du, Assessing the Impact of Multiple Active Queue Management Routers, Proceedings of Globecom, accepted June 2006, to appear.

Abstract

Recent studies have shown that a non-negligible number of packets face multiple congested links on Internet paths. We investigate the impact of using multiple Active Queue Management (AQM) routers on paths that consist of multiple congested links. We present the results of an ns-2 evaluation study of various AQM techniques that, in contrast to previous studies of AQM, uses a complex network topology including up to 3 congested links, reverse path traffic, and realistic round-trip times. We consider the effects of multiple AQM routers on the throughput of long-lived FTP flows and HTTP response times of web traffic. We find that, especially for web traffic, performance is improved as the number of AQM routers is increased, but that significant improvements occur with even a single AQM router.

ns-2 Modifications

• PackMime - HTTP traffic generator
• DelayBox - Per-flow delay, loss, and bottleneck bandwidth
• Full-TCP bug fixes - these fixes have now been incorporated into ns-2.29
• trace.cc - modified ns/trace/trace.cc for cleaner output of Full-TCP trace-queue data files

• 8q-exp - main script
• parking-lot.tcl - TCL file
• format-time-mem.pl - used by parking-lot.tcl

• process - main processing script
• The following 4 scripts are used by process to determine frequency of ECN marking and congestion notification:
  • grab-marks
  • find-earliest-mark.pl
  • process-ECN-marks
  • process-congnotif