ECE 8990 Advanced Computer Network SystemsMississippi State University Comparison of TCP SACK and TCP Peach Sriram Rajan Vijaykumar Rajaram

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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 ConclusionReferences

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach Working of TCP SACK SACK option in TCP header HL 16 bit SRC Port16 bit DST Port 32 bit sequence number 32 bit ACK number 16 bit window size resvd flags 16 bit urgent pointer 16 bit TCP checksum Options (40 bytes) Data

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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 Kind=5 Length (n) Left edge of 1 st block (32 bits) Right edge of 1 st block (32 bits) … Left edge of nth block (32 bits) Right edge of nth block (32 bits)

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach Working of TCP Peach

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach Comparison Throughput of TCP SACK

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach Comparison Throughput of TCP Peach

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach 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

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach Future Work Implement FACK/ SACK option in TCP Peach Use the same network scenario to compare with TCP SACK

ECE 8990 Advanced Computer Network SystemsComparison of TCP SACK & TCP Peach References 1.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 2.V. Jacobson, “Congestion Avoidance and Control,” ACM Comp. Commun.Rev., vol. 18, no. 4, Aug. 1988, pp. 314–29. 3.R. T. Braden, “Requirements for Internet Hosts — Communication Layers,”, RFC 1122, IETF, Oct A Tanenbaum; “Computer Networks”, (4th ed), 2003, pp 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 K. Kevin and S. Floyd; “Simulation-based comparisons of Tahoe, Reno and SACK TCP”, ACM SIGCOMM Computer Communication Review, vol. 26, pp 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, MASCOTS, October 2003, pp M. Mathis, J. Mahdavi, S. Floyd, and A. Romanow. Tcp selective acknowledgement options.Technical Report RFC 2018, IETF, 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.