Ankur VyavaharkarGagandeep 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 . 437-444.

Performance enhancement techniques for TCP over wireless links Yanmaz, E.; Wei, S.-C.; Tonguz, O.K.;Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st 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 onVolume 51,  Issue 6,  Nov. 2002 Page(s):1608 – 1620.

The effect of reordering and dropping packets on TCP over a slow wireless link , Nehme, A.; Phillips, W.; Robertson, W.; Electrical and Computer Engineering, 2003. IEEE CCECE 2003. Canadian Conference on Volume 3, 4-7 May 2003 Page(s):1555 - 1558 vol.3

M. Meyer, J. Sachs, Performance Evaluation of a TCP Proxy in Wireless Networks, IEEE Wireless Communications, October 2003, pp. 70-79.

Xylomenos, G.; Polyzos, G.C.; Mahonen, P.; Saaranen, M.; Communications Magazine, IEEE Volume 39,  Issue 4,  April 2001 Page(s):52 - 58 .

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 networksWu, E.H.-K.; Mei-Zhen Chen;Selected Areas in Communications, IEEE Journal onVolume 22,  Issue 4,  May 2004 Page(s):757 - 766