Proxy Supported Power Optimization for Heterogeneous Wireless Clients

1. Proxy Supported Power Optimization for Heterogeneous Wireless Clients Annie L. Luo IBM T.J. Watson Research Center Mentor: Marcel Rosu Manager: Chandra Narayanaswami Annie L. Luo, Carnegie Mellon University

2. 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 client’s WNIC Based on: • Application domain knowledge • MAC level configuration • Network conditions Annie L. Luo luluo@cs.cmu.edu

3. 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 Annie L. Luo luluo@cs.cmu.edu

4. DIRECT PROXY Comparison on Power Consumption ACPIspec.pdf eBay.com www.eBay.com Annie L. Luo luluo@cs.cmu.edu

5. Oracle Rules Client SideThreads Fetching Threads Blackboard WLAN Clients Web Servers Information perRequest Information perClient Architecture of PAWP (summer 2003) Annie L. Luo luluo@cs.cmu.edu

6. 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 Annie L. Luo luluo@cs.cmu.edu

7. 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 Annie L. Luo luluo@cs.cmu.edu

8. 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 Annie L. Luo luluo@cs.cmu.edu

9. Oscilloscope(VellemanPC S64i) Vdd=3.3V - VR + Digital Multimeter(HP3458A) Wireless Client(IBM ThinkPad) Intersil PRISM3 PC Cardwith Extender Data collection PC R=0.53 W 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 Annie L. Luo luluo@cs.cmu.edu

10. Improving the Experimental Testbed • Limitations in the prior-summer’04 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 Annie L. Luo luluo@cs.cmu.edu

11. Improving the Experimental Testbed • Limitations in the prior-summer’04 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 Annie L. Luo luluo@cs.cmu.edu

12. 0 210 120 150 180 30 60 90 Complete, Across-The-Board Experiments • Based on the new experimental testbed • Experiments on each proxy configuration can be done in < 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) Annie L. Luo luluo@cs.cmu.edu

13. Experimental Results (1) Annie L. Luo luluo@cs.cmu.edu

14. Experimental Results (2) Relative energy consumption with Proxy vs. Direct case throughput Cost and Benefits of Proxy Features Results from WMCSA’04 paper Annie L. Luo luluo@cs.cmu.edu

15. 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 summer’04 Annie L. Luo luluo@cs.cmu.edu

16. 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 Annie L. Luo luluo@cs.cmu.edu

17. Web Page Rendering Annie L. Luo luluo@cs.cmu.edu