Ankur Vyavaharkar Gagandeep Gill

 TCP overview  TCP fundamentals  Wireless Network  Simulation using Opnet  Mobility and TCP  Improvements

 Connection oriented end-to-end data transfer protocol.  reliable end-to end transmission of data achieved by error and retransmission.  Congestion control over the internet.  Much better suited for wired networks than wireless networks.  End-to-end semantics  Acknowledgements sent to TCP sender confirm delivery of data received by TCP receiver  Ack for data sent only after data has reached receiver

 Efficient use of higher bandwidth networks.  Avoiding Dead Lock situation.  Transmits certain segments with sequence numbers.  Effective flow control

 Communication over wireless links is often characterized by sporadic high bit-error rates, and intermittent connectivity due to handoffs.  When packets are lost in networks for reasons other than congestion, these measures result in an unnecessary reduction in end –to-end throughput and sub- Optimal performance.  TCP performance in wireless networks suffers from significant throughput degradation and very high interactive delays.

 Low quality wireless links  Mobility  High probability of transmission errors  Low data rates  Long delays  Lower bandwidth  Handovers

SCENARIOS

Mobility and TCP

 Link Layer protocols  Indirect-TCP protocol  The snoop Protocol  Selective Acknowledgments

 Window limitation.  Selective acknowledgement (SACK).  TCP byte counting.  Split connection.  Last hop solutions.

 A comparison of different TCP flavors are made.  Reno performs well when congestion is less ( i.e. one drop)  It can be seen from the graph that Modified TCP Tahoe perform best in a wireless scenario when congestion is more.  Slow Start and congestion avoidance is very important algorithm for improvement in TCP performance.

 Some mechanisms to improve TCP/IP performance over Wireless and mobile computing environment, Wen- Tsuen Chen; Jyh-Shin Lee; Parallel and Distributed Systems 2000 proceedings Seventh International Conference 4-7 July 2000 pp  Performance enhancement techniques for TCP over wireless links Yanmaz, E.; Wei, S.-C.; Tonguz, O.K.; Vehicular Technology Conference, VTC Spring IEEE 61 st Volume 4, 30 May-1 June 2005 Page(s):2245 – 2249.

 A reconfigurable protocol setting to improve TCP over wireless Chiasserini, C.-F.; Meo, M.; Vehicular Technology, IEEE Transactions on Volume 51, Issue 6, Nov Page(s):1608 –  The effect of reordering and dropping packets on TCP over a slow wireless link, Nehme, A.; Phillips, W.; Robertson, W.; Electrical and Computer Engineering, IEEE CCECE Canadian Conference on Volume 3, 4-7 May 2003 Page(s): vol.3

 M. Meyer, J. Sachs, Performance Evaluation of a TCP Proxy in Wireless Networks, IEEE Wireless Communications, October 2003, pp  Xylomenos, G.; Polyzos, G.C.; Mahonen, P.; Saaranen, M.; Communications Magazine, IEEE Volume 39, Issue 4, April 2001 Page(s):  S. Floyd, “A report on recent developments in TCP congestion control,” IEEE Communications Magazine, vol. 39, no. 4, pp. 84–90, April 2001.

 JTCP: jitter-based TCP for heterogeneous wireless networks Wu, E.H.-K.; Mei-Zhen Chen; Selected Areas in Communications, IEEE Journal on Volume 22, Issue 4, May 2004 Page(s):