TCP Performance Optimizations forWireless Sensor Networks

EWSN 2012

Philipp Hurni, Ulrich Bürgi, Markus Anwander, Torsten Braun

Research Group ―Communication and Distributed Systems‖

Institute of Computer Science and Applied Mathematics

University of Bern, Switzerland

braun@iam.unibe.ch, cds.unibe.ch

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

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

Optimization of TCP in WSNs

> Distributed TCP Caching (Dunkels et al., 2004)

> TCP Support for Sensor Networks (Braun et al., 2007)

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)

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)

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

MAC Proxy

Channel Activity Levels with X-MAC

Long Idle Periods

Spatial Reuse by Multiple TCP Connections

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

Throughput

Radio On-Time as Energy Consumption Measure

Throughput with Multiple Connections

Overall Comparison of Throughput

Overall Comparison of Energy Consumption

Cross-Traffic Measurements

Cross-Traffic Throughput

Cross-Traffic Comparison

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)

Thanks for your attention !

> braun@iam.unibe.ch

> http://cds.unibe.ch

TCP Performance Optimizations forWireless Sensor Networks

Technology

TCP/IP Optimizations for High Performance WANs · 2020-01-24 · TCP/IP provides the underlying transport for most of the bulk data transfers across wide area networks (WANs) including

Presemtation Tier Optimizations

Frontend Optimizations (Greek)

Introduction to Optimizations

Linear Optimizations

Optimizing CUDA. 2 © NVIDIA Corporation 2008 Outline Overview Hardware Memory Optimizations Execution Configuration Optimizations Instruction Optimizations

Intraprocedural Optimizations

Optimizations and Tradeoffs

Ethernet and TCP optimizations

Turbo Decoding and Detection forWireless Applications

A Survey of Energy Efficient Network Protocols ForWireless Networks

Bytecode Optimizations

Presentation Tier optimizations

Embedded Linux Optimizations

Improving compiler optimizations using Machine Learningudspace.udel.edu/bitstream/handle/19716/13442/2014_Kulkarni_Sameer_PhD.pdf · Some compiler optimizations are binary optimizations,

TCP Performance Optimizations for Wireless Sensor …home.inf.unibe.ch/~rvs/research/pub_files/HBAB12.pdf · TCP Performance Optimizations for Wireless Sensor Networks ... Contiki

Global optimizations

Optimizations - Advanced

Spark optimizations & deployment

De-optimizations ATTACK!!!