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Analysis of Energy Consumption of TCP Reno, Newreno, and SACK in Multi-Hop Wireless Network

Analysis of Energy Consumption of TCP Reno, Newreno, and SACK in Multi-Hop Wireless Network. Thesis Defense of Harkirat Singh. Outline. Motivation TCP Mechanism Energy Model Experiment Methodology Experiment Results Conclusion. Motivation. Wireless devices need to be Reliable

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Analysis of Energy Consumption of TCP Reno, Newreno, and SACK in Multi-Hop Wireless Network

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  1. Analysis of Energy Consumption of TCP Reno, Newreno, and SACK in Multi-Hop Wireless Network Thesis Defense of Harkirat Singh

  2. Outline • Motivation • TCP Mechanism • Energy Model • Experiment Methodology • Experiment Results • Conclusion

  3. Motivation • Wireless devices need to be • Reliable • Light Weight • Wireless links are error prone, low bandwidth etc. • TCP connection suffers long idle time hence low throughput • How is Power consumed in a wireless node?

  4. Lucent 802.11 Silver (11 Mbps) WaveLAN DSSS PC Card Characteristics [INFOCOM’01] • Radio States : Transmit, receive, idle, sleep Power (Sleep) = 50mW Power (Idle) = 780mW Idle / Sleep Ack Data Recv Xmt Power (Xmt) = 1478mW Power (Recv) = 900mW

  5. TCP Mechanism • TCP is a sliding window protocol with built in self-clocking and congestion control algorithm • Slow start • Congestion avoidance • Fast retransmit • Fast recovery • TCP Tahoe implements first three • TCP Reno, Newreno and SACK have all four

  6. Slow start • Slow start is used during initial phase of a connection or after retransmission timeout (Probing the network) • It is also known as additive increase and multiplicative decrease cwnd:1 cwnd:2 cwnd:4 cwnd:8 Sender Receiver

  7. Fast retransmit and recovery • TCP receiver generates ack for next expected packet • In the event of packet loss or reordering, receiver Acks last in-sequence pkt received • TCP sender retransmits first unacknowledged packet after 3 dup_acks without waiting for retransmit timer to go off • ssthresh = min (cwnd, rcv advertised window) / 2 • Send missing pkt and set cwnd += 3 • Inflate cwnd till retransmitted pkt is acked • Deflate the window, enter Congestion Avoidance

  8. Congestion Avoidance • When cwnd > ssthresh TCP invokes Congestion Avoidance • cwnd += 1/cwnd (for each ack) • In other words cwnd is incremented (cwnd++) by one per round trip time • It is conservative approach to increase cwnd as name suggests • When congestion is detected (by timeout), TCP slows down and invokes slow start

  9. Evolution of TCP window Fast retransmit and recovery Slow start Congestion avoidance Congestion Window Time

  10. Evolution of cwnd Outstanding Data Time

  11. TCP Newreno • TCP Reno is optimized for single packet loss in a window, multiple pkt loss degrades the performance • TCP Newreno enhances the performance in the event of multiple pkt drop without having SACK • Introduces new variable Partial ACK • When fast retransmit is invoked record the highest sequence number transmitted as Recover • When all of the data up to and including Recover is acknowledged TCP exits fast recovery • Avoids invocation of Fast retransmit in quick succession

  12. SenderReceiver 0 .. 61 7 .. 14 14 7 .. 13 cwnd : 8 New round 14 dup Acks 0 .. 131 14 15 .. 28 15 .. 28 cwnd : 15 New round 14, 29 .. 34 14 29 .. 34 cwnd : 10 cwnd : 21 Receiver generates Ack 29, sender exits Fast recovery and adjust “inflated” cwnd and enters Congestion avoidance 0 .. 281 cwnd : 7

  13. TCP SACK • SACK Data structure • Recoverand Partial ack as Newreno • Receiver informs non-contiguous data • Receiver can reflects max of three SACK blocks • Sender maintains a queue of segments that have been transmitted but not yet acknowledged, Scoreboard • SACK is invoked in the event of three dup_acks • Sender can judiciously send new packet or retransmit packet to fill hole at receiver

  14. next next next tcp_seq start tcp_seq start tcp_seq start tcp_seq end tcp_seq end tcp_seq end dups dups dups rxmit rxmit rxmit TCP SACK Data Structures struct tcpcb { … struct sackhole *snd_holes; … …

  15. SACK Example Sender’s queue Receiver’s queue 1 2 3 4 5 6 1 2 ACK 1 SACK [2] 1 3 4 5 6 2 3 4 ACK 1 SACK [3,2] 1 4 5 6 6 2 3 5 ACK 1 SACK [5,3,2] 1 4 6 HOLES AT RCVR

  16. Evolution of ACK received by TCP-SAC Sender 3 dup_ack Sequence Number Time

  17. TCP Protocols Summary

  18. Outline • Motivation • TCP Mechanism • Energy Model • Experiment Methodology • Experiment Results • Conclusion

  19. Energy consumption of a node Packet Reception + ProcessingPacket Processing + Transmission Idle Period Current PTX PRX Idle Current Consumption Pidle Time

  20. Energy Model • Total energy (E) can be represented as • PTX is energy spent for transmission • tTX is time spent in transmission • tRX is negligible so can be eliminated • Assume average connection throughput is bytes/sec and the transmission speed is r bytes/sec we can write

  21. Goals • Awake node during ideal time consume unnecessary power • Power off nodes during idle period this gives lower bound of Total Energy consumption though not realistic call it Idealized Energy • Alternatively during idle period node is asleep and in the event of a pkt node is awoken up by radio

  22. Goals contd.’ • Investigate the Energy consumption of TCP variants (Total Energy vis-à-vis Idealized Energy) • TCP connection characteristic in wireless revisited • Low bandwidth connection • Higher BER • Mobility • These leads to longer Idle time • Hence TCP sender can sleep!!

  23. Evolution of TCP Sequence Idle connection Sequence Number Time

  24. Outline • Motivation • TCP Mechanism • Energy Model • Experiment Methodology • Experiment Results • Conclusion

  25. Test Bed • Three hop wireless ad hoc network • Each laptop equipped with Lucent 11 Mbps WaveLAN card Running FreeBSD 4.3 • SACK is implemented based on RFC 2018 • Dummynet used for packet loss and delay • Energy measurement at sender using HP 34401A multimeter and VeePro software

  26. Energy Measurement • Two multimeters simultaneously used for measuring Radio and Total Node Power • Multimeter takes current measurement with a granularity of 1 millisecond • Multimeter dumps data to different laptop • Integration of current * voltage over connection time gives total Energy

  27. Workload, Factors, and Metrics • TTCP used as a constant workload generator - 5 MB • Error : 1%, 5% and 10% • RTT : 15, 40, 70, 100 and 130 msec • Reordering : 1% and 5% • Burst Error : 85% for 1 sec every 12 sec • MTU 512 and 1500

  28. A typical run .. Pkt Router generates Loss and Delay (DUMMYNET) Pkt Start TTCP Start Loss+Delay script Pkt Start TTCP server Start multimeter Stop

  29. Total Energy Energy Consumed by Node Current (mA) Idealized Energy Simultaneous measurement of Energy consumed by the radio Time (msec)

  30. Metrics • Total Energy/bit ( E ) measured in Joules/bit. This includes the energy consumed while the sender is idle • Idealized Energy/bit( EI )measured in Joules/bit.This measure excludes the idle time energy and thus more closely approximates the cost of the various protocols • Goodputin kbps

  31. Outline • Motivation • TCP Mechanism • Energy Model • Experiment Methodology • Experiment Results • Conclusion

  32. Parameters Values Average RTT Burst Packet Loss MTU Size RTS/CTS Protocols • 15, 40, 70, 100, 130 msec • 85% loss rate for 1 second every 12 seconds • 1500 bytes • OFF • Reno, Newreno, and SACK Experiment Results – Burst Loss

  33. Burst loss Energy Goodput NEWRENO-Total Sack-Total SACK Goodput (kbps) Energy (Joules * e-6/Bit) Reno SACK-Ideal NEWRENO-Ideal Average RTT (msec) Average RTT (msec)

  34. Parameters Values Average RTT Packet Loss MTU Size RTS/CTS Protocols • 15, 40, 70, 100, 130 msec • 1%, 5%, and 10% • 512 and 1500 bytes • ON, OFF • Reno, Newreno, and SACK Random uniform Loss

  35. 1% Packet Loss Total Energy Idealized Energy RENO512 SACK512 SACK512 Total Energy (Joules * e-6/Bit) Idealized Energy (Joules * e-6/Bit) SACK1500 RENO512 SACK1500 NEWRENO1500 Average RTT(msec) Average RTT(msec)

  36. 5% Packet Loss Total Energy Goodput RENO1500 NEWRENO1500 SACK512 SACK1500 RENO512 & NEWRENO512 Total Energy (Joules * e-6/Bit) Goodput (Kbps) SACK1500 SACK512 RENO512 & NEWRENO512 RENO1500 Average RTT(msec) Average RTT(msec)

  37. TCP Reno, Newreno and SACK (Thruput) Average Thruput: 5% Packet Loss, MTU 1500 SACK Newreno Thruput (bps) Reno Time

  38. 10% Packet Loss Total Energy Idealized Energy SACK1500 SACK1500 Idealized Energy (Joules * e-6/Bit) Total Energy (Joules * e-6/Bit) NEWRENO1500 SACK512 NEWRENO512 Average RTT(msec) Average RTT(msec)

  39. Loss Experiment Summary - (mtu 512)

  40. Parameters Values Average RTT Packet Loss Reorder Packet MTU Size RTS/CTS Protocols • 15, 40, 70, 100, 130 msec • None • 1% and 5% packets reordered • 512 and 1500 bytes • ON, OFF • Reno, Newreno, and SACK Packet Reordering

  41. Goodput : Packet Reordering 1% Packet reorder 5% Packet reorder SACK SACK512 & 1500 512 1500 NEWRENO NEWRENO 1500 Goodput (Kbps) Goodput (Kbps) 512 1500 512 Average RTT(msec) Average RTT(msec)

  42. 1% Packet Reordering Total Energy Idealized Energy RENO512 NEWRENO512 NEWRENO512 RENO512 Idealized Energy (Joules * e-6/Bit) Total Energy (Joules * e-6/Bit) SACK512 SACK512 Average RTT(msec) Average RTT(msec)

  43. 5% Packet Reordering Total Energy Idealized Energy RENO 512 1500 NEWRENO NEWRENO512 1500 512 Total Energy (Joules * e-6/Bit) Idealized Energy (Joules * e-6/Bit) NEWRENO1500 SACK512 & 1500 SACK512 & 1500 Average RTT(msec) Average RTT(msec)

  44. Discussion • SACK outperforms in most of the cases (Burst Loss, Random uniform Loss and Packet Reordering) • Does SACK help YES/NO • Higher Goodput at the cost of extra processing • SACK has higher Idealized Energy

  45. Discussion contd.’ Total Energy vs Goodput • Energy α 1 / Goodput • Idealized Energy is a • factor of Protocol E α 1/ζ Energy (Joules * e-6/Bit) Goodput (Kbps)

  46. Discussion contd.’ Timeouts (Loss case) • At higher loss all protocols perform • alike • SACK512 leads to lesser timeouts • SACK - No timeout in reordering • case, Reno > Newreno SACK1500 Average Number of Timeouts RENO512 NEWRENO512 SACK512 % Loss

  47. Related Work • TCP Energy based on simulation • We measured energy using a wireless test-bed and a real TCP/IP stack (FreeBSD) • Metrics considered were Total Energy, ratio of successful transmission to total number of transmission • Total as well as Idealized energy (Processing energy)

  48. Conclusion • Awake Energy α 1 / Goodput • Idealized Energy is a factor of Complexity of the Protocol • Channel conditions are important in selection of particular Protocol • SACK is not suitable for nodes with low Idle Energy • SACK has lower Total Energy and Idealized Energy under Packet reordering

  49. Questions?? Thank You

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