Characterizing and conserving energy consumption in mobile p2p systems
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Characterizing and Conserving Energy Consumption in Mobile P2P Systems. Selim Gürün Priya Nagpurkar Ben Zhao Department of Computer Science U.C. Santa Barbara. 1 st International Workshop on Decentralized Resource Sharing in Mobile Computing and Networking ACM MOBISHARE, Los Angeles, CA

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Characterizing and Conserving Energy Consumption in Mobile P2P Systems

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Characterizing and conserving energy consumption in mobile p2p systems

Characterizing and Conserving Energy Consumption in Mobile P2P Systems

Selim Gürün

Priya Nagpurkar

Ben Zhao

Department of Computer Science

U.C. Santa Barbara

1st International Workshop on Decentralized Resource Sharing in Mobile Computing and Networking

ACM MOBISHARE, Los Angeles, CA

September 25, 2006


Breaking news

Breaking News…

....

The U.S. software maker also boasted that Zune has what iPod doesn’t have, music-sharing capability. Using its Wi-Fi wireless function, Zune users will be able to detect one another and then share songs, recordings and pictures wirelessly.

…..

  • How to implement P2P applications/routing stacks on resource-constrained mobile devices?

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Underlying research questions

Underlying Research Questions

  • What are the resource constraints of mobile devices and what makes P2P more challenging on such devices?

  • How do current P2P protocols utilize mobile device resources, especially the limited energy supply?

  • Can we implement a mobile-friendly, energy-efficient P2P application on such devices? How?

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Decentralization induced challenges on mobile devices

Decentralization-Induced Challenges on Mobile Devices

  • Mobile devices: Very diverse

    • Linux wristwatches, multi-core laptops and anything in between

    • Our platform: smart-phone and PDA like devices

  • Energy constraints on mobile devices introduce unique challenges to distributed applications

    • In Client-Server architecture clients offload tasks to wall-powered, resource-rich servers

    • Easier to implement disconnected operation for client

  • P2P nodes provide services to fellow nodes –no servers

    • Nodes have to be awake for providing services

    • Always-on, always connected assumption hurts mobile P2P

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Underlying research questions1

Underlying Research Questions

  • What are the constraints of mobile devices and what makes P2P more challenging on such devices?

    • Energy is limited

    • Always-on nature of servers restricts sleep options

  • How do current P2P protocols utilize mobile device resources, especially the limited energy supply?

  • Can we implement a mobile-friendly, energy-efficient P2P application on such devices? How?

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P2p on resource restricted devices

P2P On Resource Restricted Devices

  • Initial idea was:

    • To evaluate the performance of a proof-of-concept P2P application on a mobile device

  • Not as trivial as it seems!

    • Many P2P protocols are implemented with no embedded platforms in mind

  • Simmud

    • Peer-to-peer multiplayer game from UPenn.

    • Back-ported to JRE 1.3 (inetsocketaddress, etc.)

    • Not stable in our run-time environment

  • FreePastry, Tapestry

    • Extensive use of non-blocking IO

    • Back-porting not feasible at all

  • Simpastry: C#

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Chimera a light weight p2p protocol

Chimera: A Light-Weight P2P Protocol

  • Light-weight, structured P2P protocol based on Tapestry

    • Developed in UCSB-CURRENT lab

    • Implemented in C as an application library

    • Easy to port: Requires (only) OpenSSL, arm-gcc is fine!

  • Chimera-CHAT

    • A generic, command-line based chat application

    • Forwards messages based on destination host’s node identifier

  • Chimera Internals

    • Borrows many concepts from Tapestry, e.g. circular address space

    • Prefix based routing: O(log(n)) hops in average

    • Nodes keep links to nodes that are in close proximity for stability

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Chimera routing

Source Node

Leafset Neighbor

Routing Neighbor

Leafset Links

Routing Table Links

Chimera Routing

3223

0230

3123

3011

3003

3001

2333

2331

1023

2011

Each node keeps a leafset of neighbors and a set of routing nodes.

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Stargate and our evaluation bench

Powermon

PerfMon

High-precision

Data Acquisition Device

SCL

Programmable

Power Supply

Stargate and Our Evaluation Bench

PowerTool

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Cpu load across scenarios

CPU Load Across Scenarios

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Wireless energy use across experiments

Wireless Energy Use Across Experiments

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Chimera energy consumption results

Chimera –Energy Consumption Results

  • CPU utilization is low

    • We do not observe any significant increase in CPU load when we increase network size from 25 nodes to 200

    • Techniques like voltage/clock scaling can reduce CPU energy consumption significantly

    • Analyzes with much larger networks pending!

  • Wireless utilization is also low

    • Idle 70% of the time, in average

    • Better utilization of wireless interface needed

  • Compared results to TMSNC

    • A command line based MSN client

    • Not a substantial difference

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Underlying research questions2

Underlying Research Questions

  • What are the constraints of mobile devices and what makes P2P more challenging on such devices?

    • Energy

    • Always-on assumption (for server functionality)

  • How do current P2P protocols utilize mobile device resources, especially the limited energy supply?

    • Most energy wasted in idle state

    • No large CPU demand difference between client-server and P2P applications

  • Can we implement a mobile-friendly, energy-efficient P2P application on such devices? How?

    • Should we depend on physical layer for energy savings? Or should we use application layer to manage it?

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Reclaiming idle power in 802 11 ad hoc mode

Beacon Interval

ATIM

ATIM

ATIM

B

Node A

B

B

Node B

Node C

A

ATIM

R

ATIM ACK

D

Data

P

Data ACK

B

Beacon

Reclaiming Idle Power in 802.11 Ad-Hoc Mode

A

A

D

A

R

P

A

L

A

L

A

L

A: Active

L: Low Power

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Physical layer power saving caveats

Physical Layer Power Saving Caveats

  • Approximate energy savings rate (when idle):

    1 – (ATIM window/Beacon window)

    • Real energy savings is lower: sleep mode uses energy

  • (Not good) Each data message requires one ATIM message + an ACK

  • ATIM window: too small-> not enough time for ATIM broadcast, too large -> not enough time for data frames

  • Cisco Aironet parameters:

    • Beacon period: 20 to 1000 milliseconds, default 100

    • ATIM window: 5 to 60 milliseconds, default 5

  • The best beacon and ATIM parameters are application specific!

    • Can we do better than this, if we let P2P routing protocols adaptively choose best parameters?

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Wireless card sleep policy

Wireless Card Sleep Policy

Can we use Chimera network manager for better energy savings?

Wi > 1 seconds

Active

Low

Power

Wt > 3 seconds

Wi: Wireless Idle time

Wt: Wake up timeouts for checking network state

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Energy savings impact of various w i

Energy Savings Impact of Various Wi

42% savings

26% savings

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Average delay of various w i

Average Delay of Various Wi

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Related work

Related Work

  • Numerous energy saving protocols exist for ad-hoc networks

    • IEEE 802.11 ad-hoc power savings protocol

    • SPAN

    • Jung et al. (Texas A&M)

  • Power profiling setups used in prior studies to characterize mobile power consumption

    • Powerscope

  • Other P2P Systems for mobile networks

    • JXTA

    • Jabber

    • RockyRoad

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Summary future directions

Summary & Future Directions

  • Our Goal: A resource-aware, energy efficient P2P protocol

    • Tapestry like Java based implementations not suitable for mobile platforms

    • Chimera: Surprisingly efficient!

  • Physical layer power saving protocols are useful but not enough!

    • More savings possible by providing more feedback from P2P protocol later to physical layer.

  • A lot of work is ongoing

    • Compare power saving methods

    • Evaluate in much larger mobile communities

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Backup slides

Backup Slides

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P2p on mobile systems

P2P on Mobile Systems

  • Peer-to-peer paradigm:

    Decentralized, highly-scalable,

    fault-tolerant networks

P2P

  • P2P nodes are both clients and servers depending on context of operation.

  • Mobile Systems:

    • More widespread than ever

    • Wireless networks everywhere

  • How to implement P2P applications/routing stacks on mobile devices when there are so many resource constraints?

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Wireless card power consumption

Wireless Card Power Consumption

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Most expensive functions

Most Expensive Functions

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Jabber

Jabber

In jabber, the peers communicate to each other using servers. Not exactly a P2P architecture

Jabber Server

Jabber Server

Mobile Jabber Client

Mobile Jabber Client

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Characterizing and conserving energy consumption in mobile p2p systems

JXTA

In JXTA, the peers has to ask rendezvous servers who provides the service.

Rendezvous Server

Rendezvous Server

Service advertisement

Service Discovery

Mobile JXTA Peer

Mobile JXTA Peer

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Rockyroad

RockyRoad

In RockyRoad, routing and service discovery protocols are designed by the developer. RockyRoad is an API.

Rendezvous Server

Rendezvous Server

Developer Specific

Service Discovery

Service advertisement

Default Protocols

Routing: Forwarding

Searching: Broadcasting

Mobile RockyRoad Peer

Mobile RockyRoad Peer

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Support for J2ME and J2SE exist!.


Characterizing and conserving energy consumption in mobile p2p systems

SPAN

SPAN sits on top of physical layer. It tries to minimize the number of nodes that have their wireless NIC turned on, while still maintaining a connected network

Localized decisions: battery and # of pairs that it can connect

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