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Comparison of TCP SACK and TCP Peach

Comparison of TCP SACK and TCP Peach. Sriram Rajan Vijaykumar Rajaram. Outline. Purpose of project Working mechanism of TCP SACK Working mechanism of TCP Peach Implementation issues of the protocols using ML Designer simulation tool Comparison of the protocols Conclusion References.

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Comparison of TCP SACK and TCP Peach

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  1. Comparison of TCP SACK and TCP Peach Sriram Rajan Vijaykumar Rajaram

  2. Outline • Purpose of project • Working mechanism of TCP SACK • Working mechanism of TCP Peach • Implementation issues of the protocols using ML Designer simulation tool • Comparison of the protocols • Conclusion • References

  3. Purpose of project • TCP SACK has better performance in long delay links [9] • TCP Peach was introduced especially for satellite links that contains long delay links [5] • The performance comparison of these protocols were not evaluated • Hence there is need for performance evaluation of these protocols

  4. Working of TCP SACK • Introduction of SACK option in the TCP header • Receiver receives a SACK-Permitted option on the SYN of the TCP header • Receiver generates and sends the SACK option • SACK option conveys extended acknowledgement information to sender

  5. 16 bit SRC Port 16 bit DST Port 32 bit sequence number 32 bit ACK number HL flags 16 bit window size resvd 16 bit TCP checksum 16 bit urgent pointer Options (40 bytes) Data Working of TCP SACK • SACK option in TCP header

  6. Working of TCP SACK • Each block definition is 8 bytes • Length is 1 byte • Kind (TCP option type identifier) is 1 byte • n blocks will have a length of 8*n+2 bytes • With a 40 byte Options header, only 4 blocks can really be defined

  7. Working of TCP Peach • Introduces sudden start and rapid recovery algorithms • With sudden start algorithm, the congestion window reaches the maximum window size rapidly • Rapid recovery algorithm identifies the cause for loss of packets and works accordingly • Adapts itself to TCP Reno receivers

  8. Working of TCP Peach

  9. Implementation issues of TCP SACK • Used ML Designer (MLD) • Modified existing TCP Reno module • Included variables “kind” and “length” in the TCPPacket data structure • The left and right vectors were included in the packet information • Separate modules for sender and receiver were developed

  10. Implementation issues of TCP SACK • A scoreboard was created at the sender end, in order to keep track of the information from the receiver • At receiver’s end, buffers were created in order to update the SACK block information based on the received segments

  11. Implementation issues of TCP Peach • The TCP Reno module was modified in the MLD • A dummy flag was added to the TCPPacket data structure • For a dummy segment, the dummy flag was set to 1 • The sudden start and rapid recovery algorithms were added

  12. Implementation issues of TCP Peach • Separate modules for sender and receiver were created • At receiver end, the flag for dummy was set in the ACK, when a dummy segment arrived • The working of the TCP Peach congestion control algorithm was implemented

  13. Network Scenario • Three TCP senders • Three TCP receivers • Variable delays as high as 1 sec • Used the random early drop (RED) scheme • The senders were connected to server through a FIFO queue • The server transmits the packets to the corresponding receivers through a TCP router

  14. Comparison Throughput of TCP SACK

  15. Comparison Throughput of TCP Peach

  16. Conclusion • TCP SACK and TCP Peach were implemented using ML Designer • Various implementation issues were observed • The performance was analyzed by comparing the throughput • TCP SACK performed better than TCP Peach

  17. Future Work • Implement FACK/ SACK option in TCP Peach • Use the same network scenario to compare with TCP SACK

  18. References • Gevros, P.; Crowcroft, J.; Kirstein, P.; Bhatti, S.; “Congestion control mechanisms and the best effort service model”, Network, IEEE , Volume: 15 , Issue: 3 , May-June 2001, Pages:16 – 26 • V. Jacobson, “Congestion Avoidance and Control,” ACM Comp. Commun.Rev., vol. 18, no. 4, Aug. 1988, pp. 314–29. • R. T. Braden, “Requirements for Internet Hosts — Communication Layers,”, RFC 1122, IETF, Oct. 1989. • A Tanenbaum; “Computer Networks”, (4th ed), 2003, pp. 532-540. • I.F.Akyildiz, G. Morabito and S. Palazzo; “TCP-Peach: a new congestion control scheme for satellite IP networks”, IEEE/ACM Transactions on Networking, vol. 9 , June 2001, pp. 307 - 321 • K. Kevin and S. Floyd; “Simulation-based comparisons of Tahoe, Reno and SACK TCP”, ACM SIGCOMM Computer Communication Review, vol. 26, pp. 5-21. • G. Schorcht, I. Troxel, K. Farhangian, P. Unger, D. Zinn , C.K. Mick, A. George, and H. Salzwedel; “System-level simulation modeling with MLDesigner”, 11th IEEE/ACM International Symposium on Modeling, Analysis and Simulation of Computer Telecommunications Systems, 2003. MASCOTS, October 2003, pp.207-212 • M. Mathis, J. Mahdavi, S. Floyd, and A. Romanow. Tcp selective acknowledgement options.Technical Report RFC 2018, IETF, 1996. • R. Bruyeron, B. Hemon, L.Zhang; “Experimentations with TCP selective acknowledgement”, ACM SIGCOMM Computer Communication reveiewm Vol. 3, Issue 2, April 1998, pp. 54 – 77.

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