Improving TCP Performance over Wireless Links with Periodic Disconnection CMPT 885-3: SPECIAL TOPICS: HIGH-PERFORMANCE NETWORKS

Transcription

1 M-TCP:Improving TCP Performance with Periodic Discnt over Wireless M-TCP Links Improving TCP Performance over Wireless Links with Periodic Disconnection CMPT 885-3: SPECIAL TOPICS: HIGH-PERFORMANCE NETWORKS Click to CMPT FINAL 885-3: PROJECT SPECIAL PRESENTATIONS TOPICS: Spring 2002 HIGH-PERFORMANCE CMPT 885-3: SPECIAL TOPICS: NETWORKS HIGH-PERFORMANCE NETWORKS April 4, 2002 Spring Wangang Zeng, Meihua Judy Zhan, Zhiwen Lin Wan Gang Zeng, Judy Zhan, Zhiwen Lin M-TCP 1

2 Motivation TCP In Wireless Network Problem Inproperly trigger congestion control Solution Avoid congestion control M-TCP 2

3 Road Map Introduction Characteristics of wireless network Problem with TCP in wireless network Approach to improve TCP performance M-TCP Implementation and simulation M-TCP in OPNET ( C language) References M-TCP 3

4 Introduction: Characteristics of Wireless Network High-Speed Network SH SH Divided into cells, and users share cell bandwidth Smaller cells are preferred to provide higher bandwidth to users Smaller cells result in smaller cell latencies, that, in turn, cause frequent handoffs Handoff: the action that mobile host changes wireless cell M-TCP 4

5 Introduction: TCP Congestion Control Window size Slope: 1/round-trip time W W/2 Time On detecting packet loss, TCP sender assumes that network congestion has occurred On determining congestion, TCP sender drastically reduces the congestion window Reducing congestion window reduces amount of data that can be sent per RTT M-TCP 5

6 Introduction: Problem with TCP over Wireless Links Congestion control may be inappropriate in wireless environment On a wireless channel, packet loss occurs due to the following reasons: Congestion. It is appropriate to reduce congestion window Transmission error. It is not appropriate to reduce congestion window Handoff. It is not appropriate to reduce congestion window M-TCP 6

7 Approach to improve TCP Performance M-TCP Kevin Brown & Suiresh Singh RFC 3135, 2757 Three-level hierarchy of architecture High-Speed Network SH SH Supervisor Host Cell Mobile Support Station(MSS) Mobile Host(MH) M-TCP 7

8 Comparison: TCP and M-TCP TCP SH TCP Fixed Host (Sender) Mobile Host (Receiver) M-TCP 8

9 Comparison: TCP and M-TCP (cont d) Cwnd Reduced TCP SH Fixed Host (Sender) Mobile Host (Receiver) If the MH disconnects to the network and RTO times out, congestion control is invoked at the sender. If the disconnection time is long, the connection may be lost. M-TCP 9

10 Comparison: TCP and M-TCP(cont d) TCP SH M-TCP Fixed Host (Sender) SH-TCP M-TCP Mobile Host (Receiver) ACK(n) ACK(n-1) At SH, TCP connection is split into SH-TCP and M-TCP M-TCP 10

11 Comparison: TCP and M-TCP(cont d) Cwnd unchanged TCP SH Fixed Host (Sender) SH-TCP M-TCP Mobile Host (Receiver) ACK(n, 0) 0) If the wireless link is broken, SH-TCP will send an ACK packet to acknowledge the nth byte with a receiver window 0. This forces the Sender into Persist Mode. M-TCP 11

12 M-TCP 12

13 M-TCP 13

14 M-TCP Characteristics Transport protocol in mobile computing Maintain end-to-end TCP semantics Be able to deal with the problems caused by lengthy disconnection or by frequent disconnection Ensure that handoffs are efficient M-TCP 14

15 Implementation Details 10BaseT M-TCP 15

16 Node Model of Supervisor Host(SH) M-TCP 16

17 M-TCP State Diagram at SH M-TCP 17

18 Node model of Mobile Host(MH) M-TCP 18

19 Modification of IP_enca M-TCP 19

20 Simulation Results --- FTP Congestion Window Size Size (byte) normal normal-discnt MTCP-discnt Time ( sec ) M-TCP 20

21 Simulation Results - DB Access Congestion Window Size Size (byte) normal discnt MTCP-discnt Time (sec) M-TCP 21

22 Simulation Result: data transfer time FTP Window Size (Byte) Time (sec) Normal Normal M-TCP Disconnect MTCP disconnect 22

23 Simulation Result: data transmission time FTP Seq. Number (byte) Time (sec) Normal Normal Disconnect MTCP Disconnect M-TCP 23

24 References 1. J. Border, M. Kojo, J. Griner, G. Montenegro, Z. Shelby, "Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations", RFC 3135, June 2001, 2. G. Montenegro, S. Dawkins, M. Kojo, V. Magret, N. Vaidya, "Long Thin Networks", RFC 2725, January 2000, 3. Kevin Brown, Suresh Singh, "M-TCP: TCP for Mobile Cellular Networks", ACM, July 1997, brown.pdf. 4. Kevin Brown, Suresh Singh, "A Network Architecture for Mobile Computing", Proc. IEEE INFOCOMM'96, S.F. CA, March 1996, 5. S. Singh, "Quality of Service Guarantees in Mobile Computing", J. Computer Communications, Vol. 19, pp , *6. K. Seal and S. Singh, "Loss profiles: A Quality of Service Measure in Mobile Computing," Journal of Wireless Networks, vol. 2, no. 1, pp , Ajay Bakre and B.R. Badrinath, "I-TCP: Indirect TCP for Mobile Hosts", In Proc. of 15th Int'l Conf. on Distributed Computing Systems (ICDCS), May Last visit Feb. 24th, M-TCP 24

25 The End M-TCP 25