Video of the Day

Ø  LA Express Park Explained!

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Proposal

Ø  One proposal/team, 1 page!q  Team members!q  Concise description of project !q  Responsibilities of each member!q  Specific equipment needed!

Ø  Written proposal due: 9/20th, 11:59pm!q  Email to Mo!

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Proposal Presentation

Ø  8 min per group!q  Including 3 min for questions!

Ø  Your elevator pitch!!

Ø  Email Mo your slides by 11am on 9/20th !q  All use Mo’s laptop à reduce context switches!

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Agilla: Mobile Agent Middleware for Wireless Sensor Networks

Chenyang Lu!Computer Science and Engineering!

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Motivation

Ø  Adaptive applications in wireless sensor networks!Ø  Adapt to changes in!

q  the environment!q  the network!q  user requirements!

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Example: Forrest

Ø  Three applications: 1) Environmental Monitoring, 2) Fire Detection, 3) Fire Tracking!

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Example: Forrest with Agilla

Env. monitoring agent Fire detection agent Fire tracking agent

Ø  Sensor network as a shared computing resource!q  Flexible application deployment!

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Example: Cargo Tracking Ø  Thousands of containers leave/join network per day!Ø  Software need to be changed on the fly due to!

q  Departure and arrival of containers!q  Container’s country and company!q  Change in security levels and policies!q  Change in tracking technologies!

Ø  Agilla: support adaptive applications in wireless sensor networks!

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Agilla’s System Architecture

TinyOS

Node @ (1,1)

Tuplespace

Agilla Middleware

Agents

TinyOS

Node @ (2,1)

Tuplespace

Agilla Middleware

Agents migrate

remote access Neighbor

List Neighbor

List

Middleware Services Middleware Services

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Agilla’s Computational Model

Clone or

Migrate Code

Stack

Heap

Condition Codes

PC

Two variants of each: 1) Strong (code + state) 2) Weak (code only)

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Mobile Agent Model

Ø  Mobile agent: unit of execution that can move across hosts!

Ø  Multiple mobile agents may share a host!Ø  Spatiotemporal decoupling => need shared data

space with uniform interfaces!

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Tuple Space-Based Coordination Ø  Content-addressable shared memory!

q  Tuple – A set of data fields!q  Template – A pattern that matches particular tuples!

Ø  Provides spatiotemporal decoupling in unreliable networks!

“out”

“rout”

“in”

Tuplespace Tuplespace

“in”

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Tuple Space Model Ø  Tuple: collection of data!

q  <15, “str”, false>!Ø  Tuple space: shared data space containing tuples!Ø  Template: patterns which match tuples!

q  <15, *, false> matches <15, “str”, false>!

Ø  Common tuple space operations:!q  out(t): add tuple t to tuple space!q  rd(T): copy tuple matching template T from tuple space!q  in(T): remove tuple matching template T from tuple space!q  regrxn(T, c): execute code segment C when tuple matching

template T is placed in tuple space!

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Agilla Tuple Space API Ø  Remotely accessible localized tuple spaces!Ø  Stores context information!Ø  Facilitates inter-agent communication!

out: ! !insert!in: ! ! !remove!rd: ! ! !read!inp: ! !probing remove!rdp: ! !probing read!regrxn: ! !register reaction!deregrxn: !deregister reaction!

rout: !insert!rinp: !probing remove!rrdp: !probing read!rrdpg: !probing group read (1-hop)!

Local Remote

Tuplespace

in out

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Location-Base Addressing

Ø  Nodes are addressed by location!

(3,1) (3,2) (3,3)

(2,2)

(1,1) (1,3)

clone to (3,3) clone to (3,1)

Fire Detection Agent

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Implementation on TinyOS 1.1.13 Ø  Agilla is available for Mica2 and MicaZ motes!

q  4 agents/node!Ø  Agent Injector!

q  Written in Java !q  Remote Injection via RMI!

Ø  Key Challenges!q  Network bandwidth!

•  Compact instructions!q  Memory!

•  ROM: 54.7KB of 128KB !•  RAM: 3.5KB of 4KB!

q  Message loss!•  Agent-level ARQ!

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Experimental Set-up Ø  6x9 Mica2 Mote

Testbed!Ø  Multi-hop Grid!Ø  One base station!

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Performance Evaluation: migration vs. remote tuple space access

Migration instructions are more reliable because of hop-by-hop acknowledgements…

…but remote tuplespace operations have less overhead

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Agilla Instruction Execution Times

Local Operations

Remote Operations

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Experiences

Ø  Fire Detection & Tracking!q  Presented at IPSN 2005!

Ø  Intruder Detection and Tracking!q  Agents guard network perimeter and follow intruders!q  Periodically report intruder location to base station!

Ø  Cargo & Inventory Management !q  In collaboration with Boeing!q  Mobile agents load manifests from RFID, find items,

detect security breaches, and send alert to Internet gateways.!

q  Demo at SenSys 2005!

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Fire Tracking Video

Video available at: http://mobilab.wustl.edu/projects/agilla

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Related Work

Ø  Distributing inanimate code modules!q  XNP [xbow’03], Deluge [sensys’04], MNP [icdcs’05],

SOS [mobisys’05]!q  Maté/Bombilla [asplos’02]!

Ø  Mobile Agent-Like Middleware!q  Sensorware [mobisys’03]!

•  Weak migration only!q  Smart Messages [Kang‘04] !

•  No remote interactions!•  Single thread per node!

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Agilla Summary

Ø  Mobile agent middleware simplifies application deployment & increases network flexibility!

Ø  Agilla middleware services!q  Agent mobility!q  Tuple space-based coordination !q  Location-centric addressing!q  Context discovery!

Ø  Empirical results demonstrate Agilla is reliable and efficient!

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C.-L. Fok, G.-C. Roman and C. Lu, Agilla: A Mobile Agent Middleware for Self-Adaptive Wireless Sensor Networks, ACM Transactions on Autonomous and Adaptive Systems, Special Issue on Self-Adaptive and Self-Organising Wireless Networking Systems, 4(3), Article 16, July 2009. Agilla: http://mobilab.wustl.edu/projects/agilla

•  Source Code •  Documentation •  Tutorials •  Experience Reports

References

Agimone: Middleware Integration of Sensor and IP Networks

!!!Chenyang Lu!Computer Science and Engineering!

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Motivating Application: Cargo Tracking

Shipping Yard

Ship Train

Truck Customer, Shipper, DHS, CBP

SensorNetwork

SensorNetwork

SensorNetwork

SensorNetwork

IP Network

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Problem Statement Ø  Weak radio => low radio range => isolated

networks => reduced utility!

Ø  Communication restrictions can be eased by connecting WSNs using a common IP network!

Ø  Custom application-specific software is written to connect sensor and IP networks!q  Sensor and IP networks have vastly different

characteristics and capabilities!q  Not reusable, error prone, inflexible!

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Background: Two Distinct Middlewares

TinyOS

Node (1,1)

Tuple SpaceNeighborsNeighbors

Agilla Middleware

MICA2 Mote

Agents

TinyOS

Node (2,1)

NeighborsNeighbors

MICA2 Mote

Agentsmigrate

remote access

Agilla Middleware

Tuple Space

Java VM

Mobile Host 1

Limone Server

Agents

Java VM

Mobile Host 2

Agentsmigrateremote access

TS

AQ

L

TS

AQ

L

TS

AQ

L

TS

AQ

L

TS

AQ

L

TS

AQ

L

TS

AQ

L

TS

AQ

L

Limone Server

Agilla: Sensor Network Middleware Limone: IP Network Middleware

•  Mobile Agents •  Host-level tuple spaces •  Host-level neighbor list

•  Mobile Agents •  Agent-level tuple spaces •  Agent-level neighbor list

Severe resource limitations Resource rich

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Programming Models

Ø  Agilla byte code!Ø  Hosted on custom VM!Ø  Handful of well-known

data types!

Ø  Java !Ø  Hosted on Java VM!Ø  Rich data types!

Agilla Limone

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Agimone

Network Architecture System Components

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Agimone Services Ø  Shared data space!

q  AgimoneAgent has own Agilla TS!q  Agilla agents access TS directly!q  AgimoneAgent wraps Agilla TS in

Limone TS API!

Ø  Sensor network discovery!q  AgimoneAgent advertises self with

Limone Registry!q  Limone Registry distributes ad to

other AgimoneAgents!q  Ads stored in AgimoneAgent’s

Agilla tuple space!

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Agimone Services Inter-network Migration

Ø  Multi-step process!Ø  Though internally

complex, appears simple to Agilla agent developer!

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Cargo Tracking Revisited Ø  Watchdog Agents!

q  Monitors sensors!q  Sends alert to base station!q  Port authority’s Limone agent

reacts to it!q  17 lines of Agilla code, 11

lines of Java code!Ø  Intrusion Search Agent!

q  Searches multiple WSNs for alert tuples!•  Autonomously crosses WSN

boundaries!q  23 lines of Agilla code, no

additional Java code!

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Experimental Setup

100Mbps Ethernet IBM R40 Laptop •  1.5GHz Pentium M •  512MB RAM •  Windows XP

Mica2 Mote on Gateway •  7.4MHz Atmel 128L •  4KB RAM •  TinyOS

115kbps serial

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Performance: Agimone Services

Ø  TS operations between mote and PC take 10-11 ms, regardless of type or direction!

Ø  Cross-WSN migration takes ~85 ms!Ø  As size of agent increases, serial link becomes

bottleneck!

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Performance: Middleware Overhead

Ø  Native implementation done using simple message passing!q  27.39ms faster to move in and out of one WSN!q  78.39ms faster round-trip across two WSNs!

In-and-Out latency End-to-End Migration Latency

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Other Integration Frameworks Ø  Hourglass [J. Shneidman, et al. 04] and Stream-Based

Overlay Networks [P. Pietzuch, et al. 06]!q  Routes data from WSN to Internet, but does not support

applications!Ø  Tenet [R. Govindan, et al. 05]!

q  PCs directly control sensors; no support for autonomous task migration!

Ø  SERUN [J. Liu, et al. 05]!q  Embedded microservers control sensors; tasks cannot migrate

across microservers!Ø  IrisNet [P. Gibbons, et al. 03]!

q  Applies database abstraction to desktop PCs with sensing peripherals (e.g., webcams)!

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Conclusions

Ø  Agimone middleware enables integration of sensor and IP networks.!

Ø  Cargo tracking application demonstrates that Agimone simplifies development.!

Ø  Enhance productivity at the cost of moderate performance overhead.!

!

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G. Hackmann, C.-L. Fok, G.-C. Roman and C. Lu, Agimone: Middleware Support for Seamless Integration of Sensor and IP Networks, International Conference on Distributed Computing in Sensor Systems (DCOSS'06), June 2006. http://www.cs.wustl.edu/mobilab/projects/agimone/

•  Source Code •  Documentation •  Tutorials •  Experience Reports

References