Experimental evaluation of TCP performance and fairness in an 802.11e test-bed

ABSTRACT

In this paper we present measurements made using an 802.11e wireless testbed. We demonstrate experimentally how the new 802.11e [1] QoS parameters behave in our testbed. We describe the testing methodology used to validate the operation of the 802.11e TXOP, AIFS and CWmin parameters and compare the experimental results to existing analytical models. We also discuss a number of practical issues encountered during our measurements. We then use the testbed to demonstrate some known problems with TCP's performance caused by cross-layer interaction between the TCP congestion control algorithm and the MAC layer CSMA/CA contention mechanism. Finally, we study how these problems can be mitigated using the flexibility provided by the 802.11e parameters via the scheme suggested in [2].

REFERENCES

• 1: IEEE P802.11E/D9.0 Draft Standard, August 2004.
• 2: D. J. Leith , P. Clifford, Using the 802.11e EDCF to Achieve TCP Upload Fairness over WLAN Links, Proceedings of the Third International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, p.109-118, April 04-06, 2005 [doi>10.1109/WIOPT.2005.54]
• 3: Q. Ni, "ns-802.11e EDCF for IEEE 802.11e Wireless LAN", http://www-sop.inria.fr/planete/qni/, November 2002.
• 4: S. Wiethölter and C. Hoene, "Design and verification of an IEEE 802.11e EDCF simulation model in ns-2.26," Technische Universität Berlin, Tech. Rep. TKN-03-019, November 2003.
• 5: G. Bianchi, "Performance analysis of IEEE 802.11 distributed coordination function," IEEE Journal on Selected Areas in Communications, vol. 18, no. 3, pp. 535--547, March 2000.
• 6: R. Battiti, B. Li, "Supporting service differentiation with enhancements of the IEEE 802.11 MAC protocol: models and analysis", Technical Report DIT-03-024, University of Trento, May 2003.
• 7: Enrico Pelletta , Hector Velayos, Performance Measurements of the Saturation Throughput in IEEE 802.11 Access Points, Proceedings of the Third International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, p.129-138, April 04-06, 2005 [doi>10.1109/WIOPT.2005.39]
• 8: M. Franceschinis, M. Mellia, M. Meo, M. Munafo, "Measuring TCP over WiFi: A Real Case", WiNMee 2005, April 2005.
• 9: Soekris Engineering, http://www.soekris.com/.
• 10: Multiband Atheros Driver for WiFi(MADWiFi), http://sourceforge.net/projects/madwifi/, October 2004 version.
• 11: MGEN, The Multi-Generator Toolset, http://mgen.pf.itd.nrl.navy.mil/.
• 12: Iperf --- The TCP/UDP Bandwidth Measurement Tool, http://dast.nlanr.net/Projects/Iperf/.
• 13: tcpdump, http://www.tcpdump.org/.
• 14: H. Balakrishnan, V. Padmanabhan, "How Network Asymmetry Affects TCP", IEEE Communications Magazine, April 2001, pp60--67.
• 15: A. Detti, E. Graziosi, V. Minichiello, S. Salsano and V. Sangregorio, "TCP fairness issues in IEEE 802.11 based access networks", submitted paper.
• 16: S. Pilosof, R. Ramjee, Y. Shavitt, P. Sinha, "Understanding TCP fairness over Wireless LAN", INFOCOM 2003, 1--3 April 2003.
• 17: H. Wu, Y. Peng, K. Long, S. Cheng, J. Ma, "Performance of Reliable Transport Protocol over IEEE 802.11 Wireless LAN: Analysis and Enhancement", INFOCOM 2002, 23--27 June 2002.

INDEX TERMS

Primary Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.2 Network Protocols
          Subjects: Protocol verification

Additional Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.5 Local and Wide-Area Networks

General Terms:
Experimentation, Measurement, Performance

Keywords:
802.11, 802.11e, TCP, fairness, test-bed