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TCP New RenoWhen multiple packets drops, Reno can not handlewellPartial ACK:

happens if multiple packets are lost

A partial ACK does not acknowledge all packets that areoutstanding at the beginning of a fast recovery (this takessender out of fast recovery)Sender must wait until timeout occurs

New Reno:Partial ACK does not take sender out of fast recoveryNew Reno can handle multiple lost segments withoutentering slow start

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Point-to-Point Client Serverconnection (PPP)

ApplicationFTPconstant file sizeConstant inter-requesttime

ProfileClientServer: FTP serverPacket discarder

drop packets

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CWND in PPP Server-Client: onedrop

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Sent Segment Sequence NumberPPP Server-Client: one drop

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CWND in PPP Server-Client: twodrops

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Sent Segment Sequence NumberPPP Server-Client: two drops

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WAN Topology

West SubnetEast Subnet

WAN Topology

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CWND in WAN: packet drop(0.05%) packet latency (0.001)

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SSSN in WAN, packet drop(0.05%)-packet latency (0.001)

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CWND in Wireless Topology

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ConclusionReno performs well only if no loss or one packet dropwithin a windowNewReno can deal with multiple lost segmentswithout entering slow start

SACK (selective acknowledgement and selectiveretransmit)TCP congestion control algorithms do not perform

satisfactory in wireless network due to signalattenuation in wireless environment.

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References

K. Fall and S. Floyd, Simulation based comparisons of Tahoe, Renoand SACK TCP, Computer Communications Review , vol. 26, no. 3, July1996, pp. 5-21.M. N. Akhtar, M. A. O. Barry and H. S. Al-Raweshidy Modified TahoeTCP for wireless networks using OPNET simulator, Proc of the London

Communications Symposium (LCS2003), London, Sept 2003.W. Stevens, TCP slow start, congestion avoidance, fast retransmit andfast recovery algorithms,. Network Working Group, RFC2001, Jan1997.M. Omueti and Lj. Trajkovic, M-TCP+: using disconnection feedback to

improve performance of TCP in wired/wireless networks, Proc. SPECTS 2007, San Diego , CA, USA, July 2007, pp. 443-450. A. S. Tanenbaum, Computer Networks, The Transport Layer, 4rdEdition.