EWSN 2012TCP Performance Optimizations forWireless Sensor NetworksPhilipp Hurni, Ulrich Bürgi, Markus Anwander,Torsten Bra...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Overview       >     Motivation and Related...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Reasons for Poor TCP Performance in       W...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Optimization of TCP in WSNs       >     Dis...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Caching and Congestion Control (cctrl)     ...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       cctrl Functions       >     Caching of     ...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Channel Activity Monitoring       >     MAC...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       MAC Proxy       Trento, February 15, 2012  ...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Channel Activity Levels with X-MAC       Tr...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Long Idle Periods       Trento, February 15...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Spatial Reuse by Multiple TCP Connections  ...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Testbed Experiments       >     7 TelosB no...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Throughput       Trento, February 15, 2012 ...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Radio On-Time as Energy Consumption       M...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Throughput with Multiple Connections       ...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Overall Comparison of Throughput       Tren...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Overall Comparison of Energy Consumption   ...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Cross-Traffic Measurements       Trento, Fe...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Cross-Traffic Throughput       Trento, Febr...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Cross-Traffic Comparison       Trento, Febr...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Conclusions       >     Implementation of c...
Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks       Thanks for your attention !       >     bra...
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TCP Performance Optimizations for Wireless Sensor Networks

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EWSN 2012, Trento

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TCP Performance Optimizations for Wireless Sensor Networks

  1. 1. EWSN 2012TCP Performance Optimizations forWireless Sensor NetworksPhilipp Hurni, Ulrich Bürgi, Markus Anwander,Torsten BraunResearch Group ―Communication and Distributed Systems‖Institute of Computer Science and Applied MathematicsUniversity of Bern, Switzerlandbraun@iam.unibe.ch, cds.unibe.ch
  2. 2. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Overview > Motivation and Related Work — Reasons for Poor TCP Performance in Wireless Multi-Hop Networks — Optimization of TCP in WSNs > Proposed Optimization Concepts — Caching and Congestion Control (cctrl) Module including Channel Activity Monitoring — Spatial Reuse by Multiple TCP Connections > Results by Testbed Experiments — Throughput — Radio On-Time as Energy Consumption Measure > Conclusions Trento, February 15, 2012 2
  3. 3. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Reasons for Poor TCP Performance in Wireless Multi-Hop Networks > Higher bit error rates and packet loss > Underlying MAC protocols (exponential back-off, hidden / exposed nodes) > TCP end-to-end error and congestion control mechanisms TCP data segment loss TCP acknowledgement loss Trento, February 15, 2012 3
  4. 4. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Optimization of TCP in WSNs > Distributed TCP Caching (Dunkels et al., 2004) > TCP Support for Sensor Networks (Braun et al., 2007) Trento, February 15, 2012 4
  5. 5. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Caching and Congestion Control (cctrl) Module > is aware of all TCP packets forwarded by a node by interception of outbound packets. > allocates buffer for 2 packets per TCP connection (1 for each direction, µIP has max. 1 unacknowledged TCP data segment per connection) Trento, February 15, 2012 5
  6. 6. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks cctrl Functions > Caching of — complete TCP data segments and scheduling of retransmission timer (RTO = 3 ∙ RTTestimated, RTTestimated = estimated RTT between intermediate node and destination) — TCP/IP header for TCP acknowledgements > Local retransmission of TCP data segment (max. 3 attempts), when RTO expires prior to TCP acknowledgement reception (a) > Removal of TCP data segments, if acknowledgement number of TCP acknowledgement > sequence number of cached TCP data segment > For retransmitted TCP data segments, for which a TCP acknowledgement has been received: discard TCP data segment; regenerate TCP acknowledgement (b) Trento, February 15, 2012 6
  7. 7. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Channel Activity Monitoring > MAC proxy notifies cctrl upon reception of any packet and stores a timestamp in activity history. > cctrl continuously calculates channel activity level (= # overheard packets by MAC proxy during the last time period RTTestimated) > Observation: — Channel activity level of most nodes = 0 during long idle periods — Long idle periods by – TCP data segment loss at one of the first hops – TCP acknowledgement loss close to its destination (i.e. TCP data segment’s source). > Approach: — Split RTO into: – RTO1 = 3 ∙ RTTestimated ∙ 2/3 – RTO2 = 3 ∙ RTTestimated ∙ 1/3 — When RTO1 expires: early retransmission, if channel activity level = 0; otherwise: retransmission when RTO2 expires. — Triggers early local retransmissions close to destination Trento, February 15, 2012 7
  8. 8. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks MAC Proxy Trento, February 15, 2012 8
  9. 9. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Channel Activity Levels with X-MAC Trento, February 15, 2012 9
  10. 10. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Long Idle Periods Trento, February 15, 2012 10
  11. 11. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Spatial Reuse by Multiple TCP Connections Trento, February 15, 2012 11
  12. 12. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Testbed Experiments > 7 TelosB nodes in different rooms of a 3 floor building using U Bern’s Wisebed testbed > Receiver node 1 > Sender nodes 2-7 > Experiments with different MAC protocols for 10 minutes, 15 repetitions > 16 bytes payload > 79 bytes per TCP data segment > 63 bytes per TCP acknowledgement > Total: approx. 2500 experiments during > 400 hours Trento, February 15, 2012 12
  13. 13. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Throughput Trento, February 15, 2012 13
  14. 14. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Radio On-Time as Energy Consumption Measure Trento, February 15, 2012 14
  15. 15. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Throughput with Multiple Connections Trento, February 15, 2012 15
  16. 16. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Overall Comparison of Throughput Trento, February 15, 2012 16
  17. 17. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Overall Comparison of Energy Consumption Trento, February 15, 2012 17
  18. 18. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Cross-Traffic Measurements Trento, February 15, 2012 18
  19. 19. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Cross-Traffic Throughput Trento, February 15, 2012 19
  20. 20. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Cross-Traffic Comparison Trento, February 15, 2012 20
  21. 21. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Conclusions > Implementation of caching, local TCP data segment retransmission, and TCP acknowledgement regeneration in intermediate nodes on top of several WSN MAC protocols > NullMAC and LPP provide good response to local retransmission. Results with ContikiMAC are worse. > cctrl can improve performance and energy efficiency. > Spatial reuse by multiple TCP connections can further improve performance. > Best performance and energy efficiency with cctrl and NullMAC ! → adaptive MAC protocols (Hurni et al., 2010) Trento, February 15, 2012 21
  22. 22. Torsten Braun:TCP Performance Optimizations for Wireless Sensor Networks Thanks for your attention ! > braun@iam.unibe.ch > http://cds.unibe.ch Trento, February 15, 2012 22
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