Proxy Supported Power Optimization for Heterogeneous Wireless Clients

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Proxy Supported Power Optimization for
Heterogeneous Wireless Clients

• Annie L. Luo
• IBM T.J. Watson Research Center
• Mentor Marcel Rosu
• Manager Chandra Narayanaswami

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Power Optimization for Wireless NIC

• Active power consumption in WLAN interface
• 5-10 in notebooks, 50-90 in PDAs
• Existing power-reduction approaches for WLAN
  clients
• 802.11 Power Saving Mode limited power saving
  during active transmissions
• MAC level extending sleep time
• Transport level energy efficient protocols
• The unpredictability of incoming traffic causes
  waste of power
• Our approach Power Aware Web Proxy (PAWP),
  using
• A web proxy to shape HTTP traffic going into
  clients WNIC
• Based on
• Application domain knowledge
• MAC level configuration
• Network conditions

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Analysis of Incoming WLAN Traffic
Data transfer
Timeout
Sources of wasted energy in WLAN interfaces
Proposing Power Aware Web Proxy that modulates
WLAN data transmission into intervals of high and
no traffic
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Comparison on Power Consumption
ACPIspec.pdf
eBay.com
www.eBay.com
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Architecture of PAWP (summer 2003)
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Limitations in PAWP-2003 Implementation

• Simplistic Blackboard
• Static data structure
• Inefficient, linear searching method and data
  access
• No memory management mechanism
• The resulting proxy
• Handles only one client at a time
• Has to be restarted after downloading each page

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A More Realistic WLAN Scenario

• Multiple, heterogeneous wireless clients, varying
  in
• Power characteristics
• Connectivity and configuration
• Processing capability
• Display size, etc.
• Clients have different requirements in power
  management
• The proxy needs to treat clients differently

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PAWP-2004 Implementation

• Improvements since summer 2003
• Handling cookies
• Pipelining requests and responses
• Enriched decision rules set for efficient traffic
  shaping
• Improvements in summer 2004
• Re-implemented Blackboard to maintain information
  using dynamic data structures enables handling
  multiple clients
• Used hash table for efficient searching and
  management of web objs increasing proxy speed
• Added memory management more realistic proxy
  behaviors
• Amount of work 3K lines of code

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Experimental Testbed
Power measurement environment for wireless client
network interface card
HTTP protocol trace collection using IBM
PageDetailer - Downloading time distribution -
Information of web objects - HTTP headers
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Improving the Experimental Testbed

• Limitations in the prior-summer04 experimental
  testbed
• Manual operations needed for everything
• Start PageDetailer start proxy start
  oscilloscope data collection start browser
  clean browser cache download web page close
  browser stop oscilloscope data collection
  stop proxy record PageDetailer information
  Start next round
• Tedious, time-consuming, error-prone
• More importantly long intervals between
  experiments make measurements inaccurate due to
  real-time network dynamics

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Improving the Experimental Testbed

• Limitations in the prior-summer04 experimental
  testbed
• Manual operations needed for everything
• Start PageDetailer start proxy start
  oscilloscope data collection start browser
  clean browser cache download web page close
  browser stop oscilloscope data collection
  stop proxy record PageDetailer information
  Start next round
• Tedious, time-consuming, error-prone
• More importantly long intervals between
  experiments make measurements inaccurate due to
  real-time network dynamics
• Summer 2004 improvements
• Automation of entire experiment process
• Coordination between the client, proxy, and data
  collection PC
• Implemented using Perl scripts (approx. 1K lines
  of code)
• Experiment monitoring made easy, measurement
  results more accurate

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Complete, Across-The-Board Experiments

• Based on the new experimental testbed
• Experiments on each proxy configuration can be
  done in lt 30 sec
• Quick, automatic switching between configurations
• Measurements in each set are close in time
  avoided deviation

1st set
2nd set
Direct
Proxy1
Proxy2
Proxy3
Proxy4
Direct
Proxy1

(sec)
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Experimental Results (1)
Website Size kB / Num of Objects Website Size kB / Num of Objects Connection Type Download Energy J Download Time s ThroughputkB/s
Internet Explorer cnn 285kB/80 Direct Proxy 4.78 1.93 (-60) 10.4 6.65 (-36) 27.4
Internet Explorer nytimes 270kB/80 Direct Proxy 4.91 2.17 (-56) 11.6 7.57 (-35) 23.3
Internet Explorer washingtonpost 535kB/73 Direct Proxy 6.50 2.98 (-54) 12.6 11.0 (-13) 42.5
Internet Explorer msn 180kB/85 Direct Proxy 6.49 2.86 (-56) 15.6 12.2 (-22) 11.5
Mozilla cnn 298kB/82 DirectProxy 4.881.52 (-69) 6.374.72 (-26) 46.8
Mozilla nytimes183kB/62 DirectProxy 4.931.23 (-75) 10.823.71 (-66) 16.9
Mozilla washingtonpost504kB/67 DirectProxy 6.722.56 (-62) 9.748.15 (-16) 51.7
Mozilla msn172kB/40 DirectProxy 3.341.30 (-61) 4.324.11 (-5) 39.8
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Experimental Results (2)
Relative energy consumption with Proxy vs. Direct
case throughput
Cost and Benefits of Proxy Features
www.nytimes.com Tload s DownloadEnergy J
no prefetching 5.73 1.82
no response pipelining 6.69 1.92
no request pipelining 5.73 1.71
all features on 5.47 1.63
Results from WMCSA04 paper
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Contributions

• Proposed and implemented a Power Aware Web Proxy
• Uses application level traffic information to
  schedule network traffic
• Enables efficient, client-specific WNIC power
  management
• No change required on client side
• Explored benefits of improved system
  predictability
• Identified possible areas for improvement in
  browser and web page design
• Publications
• MobiSys 2004 poster
• WMCSA 2004 paper
• BroadWiM 2004 paper
• Planning to submit more papers based on work of
  summer04

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Future Work and Discussions

• Future work
• Optimize proxy traffic shaping based on various
  client configuration
• Proxies for media streaming, VOIP, IM, etc.
• Proxies for ultrawide band networks
• Other research directions utilizing PAWP
  architecture
• Web page rendering
• Usability analysis and optimization
• Suggestions on HTTP extensions

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Web Page Rendering