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MULTIMEDIA TRAFFIC MANAGEMENT ON TCP/IP OVER ATM-UBR

MULTIMEDIA TRAFFIC MANAGEMENT ON TCP/IP OVER ATM-UBR. By Dr. ISHTIAQ AHMED CH. OVERVIEW. Introduction Problem Definition. Previous related work. Unique experimental design.

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MULTIMEDIA TRAFFIC MANAGEMENT ON TCP/IP OVER ATM-UBR

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  1. MULTIMEDIA TRAFFIC MANAGEMENT ON TCP/IP OVER ATM-UBR By Dr. ISHTIAQ AHMED CH.

  2. OVERVIEW • Introduction • Problem Definition. • Previous related work. • Unique experimental design. • Analysis of different TCP implementations that proves that these implementations do not utilize the available bandwidth efficiently. • Based on our analysis we proposed Dynamic Granularity Control algorithm for TCP. • Conclusions.

  3. INTRODUCTION Management of Multimedia communications requires • Efficient resource management. • Maximum utilization of bandwidth allocated. • Providing QoS parameters.

  4. Tools subjected to Multimedia Communications Among the tools for Multimedia Communications, the ATM Networks and TCP/IP protocol were selected.

  5. ATM (Asynchronous Transfer Mode) High-Speed Network Technology Features • Multi-Service Traffic Categories • - CBR (Constant Bit Rate) • - UBR (Unspecified Bit Rate) • - Promising Traffic with Quality of Service (QoS) • Academic Network & Easy to Use

  6. TCP/IP • Most Widely Used Protocol in the Internet. • It has lot of research potential to meet the network communication requirements. • Source code and helping material are easily available.

  7. PROBLEM DEFINITION ATM switchwith buffer size 3K or 4K cells ATM switch with buffer size 1K cells or 2K cells

  8. PROBLEM DEFINITION Multimedia Communications suffers from three major problems ATM switch buffer overflow. Loss of Protocol Data Units by the Protocol being used. Fairness among multiple TCP connections.

  9. My Research Problem Research is Dealing with the two above mentioned problems such that: • Avoiding Congestion in the ATM network. • Efficient utilization of bandwidth allocated. • Fairness among multiple TCP connections.

  10. Transmission Control Protocol • Different Implementations of TCP - TCP Tahoe - TCP Reno - TCP NewReno - TCP SACK • Congestion Control algorithms of TCP - Slow-Start - Congestion Avoidance - Fast Retransmit - Fast Recovery

  11. Previous Related Work TCP/IP over ATM • Jacobson (1988) • TCP Tahoe is added with Slow-Start, Congestion Avoidance and Fast Retransmit algorithms to avoid loss of data. • Jacobson (1990) • TCP Reno modified the Fast Retransmit algorithm of TCP Tahoe and added Fast Recovery algorithm. • Gunningberg (1994) • The large MTU size of ATM causes throughput Deadlock.

  12. Previous Related Work TCP/IP over ATM • Romanow (1995) • Cells of Large packet when lost at ATM level heavily effects TCP throughput. • This gives rise to cell discard strategies like PPD (Partial Packet Discard) and EPD (Early Packet Discard). • Larger the MTU size smaller will be the TCP Throughput • Hoe (1996) • The slow-start algorithm ends up pumping too much data. • Fast Retransmit algorithm may recover only one of the packet losses.

  13. Previous Related Work TCP/IP over ATM • Floyd (1996) • TCP Reno implementation is modified to recover multiple segment losses. The implementation is named as TCP NewReno. • Mathis (1996) • The Fast Retransmit and Fast Recovery algorithms are modified using Selective Acknowledgment Options. The new TCP version is known as TCP SACK.

  14. Problems of TCP/IP over ATM • SUMMARY of Related Research Work • Segment losses badly effect the throughput of TCP over congested ATM networks. • Fast Retransmit and Fast Recovery algorithms of Reno TCP are unable to recover multiple segment losses in the same window of data. • NewReno TCP and Linux TCP algorithms are supposed to recover these segment losses but……..

  15. Previous Research on TCP/IP over ATM is related to: • Multiple UBR streams from different sources are contending at the same output port of the ATM switch. • Major part of the related research is based on simulated studies.

  16. Unique Experimental Design The ATM Network being Congested due to: • CBR flow, which has absolute precedence, and the TCP flow on UBR sharing the same output port in the ATM switch. • The cell buffer size in the ATM switch for UBR meets the minimum requirement.

  17. Traffic Generator Cell Loss Unique Experimental Design Fujitsu EA1550 CBR Streams CBR B A FreeBSD 3.2-R Switch Buffer MTU Size TCP Traffic over UBR TCP ThroughputAnalysis depending on 4 parameters C FreeBSD 3.2-R Netperf Tcpdump Socket Buffer Size

  18. My Research Contribution • Throughput measurement and analysis of TCP over congested ATM under variety of network parameters. • Throughput evaluation and analysis of several TCP implementations. • Proposed a new congestion control scheme for TCP to avoid congestion in the ATM network and to improve the throughput of TCP.

  19. Performance Analysis of Linux TCP

  20. Congestion Control Algorithms of Linux TCP • Slow-Start algorithm • Congestion Avoidance • Fast Retransmit algorithm. • Fast Recovery algorithm.

  21. Slow-Start Algorithm Sender Receiver ATM switch 1St segment 2nd segment Acknowledgment (ACK)

  22. Congestion Avoidance Algorithm Sender Receiver ATM switch one segment per RTT 2nd segment after RTT Acknowledgment (ACK)

  23. Fast Retransmit and Fast Recovery Algorithms Sender Receiver ATM switch one segment per RTT 2nd segment after RTT Acknowledgment (ACK) Duplicate ACK

  24. Throughput Results CBR Stream = 100[Mbps] Socket Buffer Size=64Kbytes 100 RENO TCP MTU=9180bytes Linux TCP MTU=9180bytes 80 Linux TCP MTU=1500bytes Linux TCP MTU=512bytes 60 Effective Throughput[Mbps] 40 20 0 0 50 100 150 200 UBR Switch Buffer Size[Kbytes]

  25. Throughput Results Switch Buffer Size = 53[Kbytes] Socket Buffer = 64[Kbytes] MTU=9180bytes CBR Stream PressureTCP Throughput over UBR 140 Reno TCP 120 Linux TCP 100 80 Throughput[Mbps] 60 40 20 0 0 20 40 60 80 100 120 140 CBR Pressure[Mbps]

  26. Segments Acknowledged ( No. of bytes) CBR=100Mbps MTU=9180bytes Buffer Size=53Kbytes 10000 Linux TCP E.TP=7.06 Mbps 8000 6000 Packets Acknowledged[Kbytes] 4000 2000 0 0 2 4 6 8 10 Time[sec]

  27. Analysis of Linux TCP • TCP throughput is less than 20% of the available bandwidth and varies 14 to 16%. • Retransmission time outs are less than Reno TCP. • Linux TCP will be bad in connection sensitive applications due to expiry of its retransmission timer. • Retransmission timer expires due to the making a decision what to send. • Retransmission timeouts and FRR processes consumed almost more than 50% of the total time. • If MTU size is large then congestion occurs soon.

  28. Proposed Dynamic Granularity Control (DGC) algorithm for TCP A more conservative Jacobson’s congestion avoidance scheme is applied by reducing the MSS size. Step 1: Congestion Avoidance • Decrease MSS to 1460 bytes if MSS >1460 bytes. • If MSS =1460 bytes, decrease MSS to 512 bytes.

  29. Proposed DGC Algorithm for TCP Fast retransmit machine (FRM) consist of following stages. • Fast retransmission. • Fast recovery. • TCP re-ordering. • Segment loss. Step 2:FRM. • Reducing MSS to 512 bytes under FRM events.

  30. Implementation of DGC algorithm • DGC is implemented on Linux kernel 2.4.0-test10 with ATM-0.78 distribution. • Sender side implementation.

  31. Results and Discussions CBR Stream = 100[Mbps] Window Size=64Kbytes 120 DGC TCP MTU=9180 bytes Linux TCP MTU=9180 bytes 100 Linux TCP MTU=512 bytes 80 Available bandwidth 60 Effective Throughput[Mbps] 40 20 0 0 50 100 150 200 Switch Buffer Size[Kb]

  32. Results and Discussions Switch buffer size = 53[Kbytes] Window size=64Kbytes 160 DGC TCP MTU=9180 bytes 140 Linux TCP MTU=9180 bytes Linux TCP MTU=512 bytes 120 Available bandwidth 100 80 Throughput[Mbps] 60 40 20 0 0 20 40 60 80 100 120 140 160 CBR Pressure[Mbps]

  33. Segments Acked (No. of Bytes) Switch buffer size = 53[Kbytes] MTU=9180bytes 60000 DGC TCP E.TP=41.71 Mbps Linux TCP E.TP=7.06 Mbps 50000 40000 30000 Number of Segments Acked [Kbytes] 20000 10000 0 0 2 4 6 8 10 Time[sec]

  34. TWO UBR STREAMS without any External CBR Pressure 100 UBR Stream1 CBR=100[Mbps] UBR Stream2 CBR=100[Mbps] 80 Single UBR Stream [Mbps] 60 Effective Throughput[Mbps] 40 20 0 0 50 100 150 200 Switch Buffer Size[K bytes]

  35. Multiple Streams of Linux TCP under CBR pressure 100 Maximum Available Bandwidth [Mbps] Linux TCP UBR1 CBR=100[Mbps] 80 Linux TCP UBR2 CBR=100[Mbps] 60 Effective Throughput[Mbps] 40 20 0 0 50 100 150 200 Switch Buffer Size[K bytes]

  36. Linux TCP and DGC TCP Streams 100 DGC TCP UBR Flow1 CBR=[100Mbps] Linux TCP UBR Flow2 CBR=100[Mbps] 80 Maximum Available Bandwidth [Mbps] 60 Effective Throughput[Mbps] 40 20 0 0 50 100 150 200 Switch Buffer Size[K bytes]

  37. DGC and Linux TCP under CBR Pressure 140 DGC TCP UBR Flow1 120 Linux TCP UBR Flow2 Total Additive Throughput [Mbps] 100 80 Throughput[Mbps] 60 40 20 0 0 20 40 60 80 100 120 140 CBR Pressure[Mbps]

  38. CONCLUSIONS • Proposed TCP DGC algorithm used more than 98% of the available bandwidth. • No Retransmission timeout occurs and hence synchronization effect is minimized. • Fairness is thoroughly better than the other available flavors of TCP.

  39. Final Concluding Remarks • Analysis of TCP Reno • Slow-start algorithm pumps too much in the network. • If MTU size is large then throughput will be better. • Throughput of TCP is less than 2% of the available bandwidth during heavy congestion in the network. • The retransmission timeout occurs too frequently producing TCP throughput deadlock. • Fast Retransmit and Fast Recovery algorithms are unable to recover multiple segment losses.

  40. Final Concluding Remarks • Analysis of Linux TCP • Throughput of Linux TCP is improved as compared to TCP Reno but still less than 20% of the available bandwidth. • If MTU size is large then congestion state in the network is achieved soon. • More than 50% of the total is consumed to recover a segment loss. • Retransmission timeout still occurs, therefore Linux TCP will be bad in connection sensitive applications.

  41. Final Concluding Remarks • Analysis of proposed TCP DGC algorithm • Almost all the available bandwidth is utilized. • The idea is equally applicable to other communication protocols facing congestion problem in the network. • DGC TCP may not be useful over the Internet in certain cases.

  42. Future Directions • High-Speed TCP • http://www.icir.org/floyd/hstcp.html • Fast TCP • http://netlab.caltech.edu/FAST/ • TCP Performance Tuning Page • http://www.psc.edu/networking/projects/

  43. Future Directions • Performance analysis of multiple TCP connections, fairness, and buffer requirements over Gigabit Networks. • Multi-homing • Multi-streaming • SCTP (Stream Control Transmission Protocol) • Performance analysis of TCP flavours over Wireless Ad-hoc networks

  44. Thank you very much.

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