Motivation Agilla: Mobile Agent Middleware � Existing sensor network software lacks flexibility Entire network runs just one application � for Wireless Sensor Networks Cannot adapt to changes in � • the environment • the network • user requirements Chenyang Lu Department of Computer Science and Engineering 2 Agilla: A Flexible Middleware for Example: Forrest Sensor Networks � Three applications: 1) Environmental Monitoring, � Sensor network as a shared computing resource 2) Fire Detection, 3) Fire Tracking � Flexible application deployment Env. monitoring agent Fire detection agent Fire tracking agent 3 4 Example: Cargo Tracking Agilla’s System Architecture � Thousands of containers leave/join network per day Node @ (2,1) � Software need to be changed on the fly due to Node @ (1,1) Agents Agents � Departure and arrival of containers m igrate Container’s country and company � Change in security levels � Change in security policies � rem ote Neighbor Neighbor � Change in tracking technologies access Tuplespace Tuplespace List List � Agilla : support rapid and flexible deployment of Middleware Services Middleware Services software in wireless sensor networks Agilla Middleware Agilla Middleware TinyOS TinyOS 5 6 1
Agilla’s Computational Model Tuple Space-Based Coordination � Content-addressable shared memory � Tuple – A set of data fields � Template – A pattern that matches particular tuples PC Clone � Provides spatiotemporal decoupling in unreliable networks or Stack Migrate Code “rout” Condition Codes “in” “in” “out” Heap Tuplespace Two variants of each: Tuplespace 1) Strong (code + state) 2) Weak (code only) 7 8 Agilla Tuple Space API Location-Base Addressing � Remotely accessible localized tuple spaces � Nodes are addressed by location � Stores context information out in � Facilitates inter-agent communication Tuplespace (3,3) (3,1) (3,2) Local Remote out : insert (2,2) rout : insert in : remove clone to (3,3) rinp : probing remove clone to (3,1) rd : read rrdp : probing read inp : probing remove rrdpg : probing group read (1-hop) Fire Detection rdp : probing read (1,3) (1,1) Agent regrxn : register reaction deregrxn : deregister reaction 9 10 Implementation on TinyOS 1.1.13 Our Test Bed � Agilla is available for Mica2 and MicaZ motes � 6x9 Mica2 Mote 4 agents/node Test Bed � � Agent Injector � Multi-hop Grid Written in Java � � One base station Remote Injection via RMI � � Key Challenges � Network bandwidth • Compact instructions Memory � • ROM: 54.7KB of 128KB • RAM: 3.5KB of 4KB Message loss � • Agent-level ARQ 11 12 2
Performance Evaluation: Agilla Instruction Execution Times migration vs. remote tuple space access Local Operations Migration instructions are more reliable because of hop-by-hop acknowledgements… Remote … but remote tuplespace operations Operations have less overhead 13 14 Initial Experiences Fire Tracking Video � Fire Detection & Tracking � Presented at IPSN 2005 � Intruder Detection and Tracking Agents guard network perimeter and follow intruders � � Periodically report intruder location to base station � Cargo & Inventory Management � In collaboration with Boeing Mobile agents load manifests from RFID, find items, detect � security breaches, and send alert to Internet gateways. � Demo at SenSys 2005 (coming) 15 Video available at: http:/ / m obilab.w ustl.edu/ projects/ agilla 16 Related Work Agilla Summary � Distributing inanimate code modules � Mobile agent middleware simplifies application deployment & increases network flexibility � XNP [xbow’03], Deluge [sensys’04], MNP [icdcs’05], SOS [mobisys’05] � Agilla middleware services Maté/Bombilla [asplos’02] � Agent mobility � � Mobile Agent-Like Middleware Tuple space-based coordination � � Sensorware [mobisys’03] Location-centric addressing � • Weak migration only � Context discovery � Smart Messages [Kang‘04] � Empirical results: deploying sensor network • No remote interactions applications on Agilla is reliable and efficient • Single thread per node 17 18 3
References Agimone: Middleware Support for Seamless Integration of Sensor and C.-L. Fok, G.-C. Roman, and C. Lu, Rapid Development and IP Networks Flexible Deployment of Adaptive Wireless Sensor Network Applications, International Conference on Distributed Computing Systems (ICDCS'05), June 2005. Agilla: http://mobilab.wustl.edu/projects/agilla • Source Code • Documentation Chenyang Lu • Tutorials • Experience Reports Department of Computer Science and Engineering 19 Motivating Application: Cargo Tracking Problem Statement � Weak radio => low radio range => isolated networks => reduced utility Ship Train � Communication restrictions can be eased by connecting WSNs using a common IP network � Custom application-specific software is written to connect sensor and IP networks Sensor and IP networks have vastly different characteristics � and capabilities � Not reusable, error prone, inflexible Truck Shipping Yard Customer, Shipper, DHS, CBP 21 22 Background: Two Distinct Middlewares Mobile Agent Model � Mobile agent : unit of execution that can relocated Node (1,1) Node (2,1) across hosts Agents Agents migrate � Multiple mobile agents can run on each host AQL AQL AQL AQL AQL AQL AQL AQL remote � High degree of spatio-temporal decoupling => need access Neighbors Neighbors Tuple Space Tuple Space Neighbors Neighbors Agilla Middleware Agilla Middleware shared data space with uniform interfaces. TinyOS TinyOS MICA2 Mote MICA2 Mote Agilla : Sensor Network Middleware Lim one : I P Network Middleware • Mobile Agents • Mobile Agents • Host-level tuple spaces • Agent-level tuple spaces • Host-level neighbor list • Agent-level neighbor list Severe resource lim itations Resource rich 23 24 4
Agilla and Limone Programming Tuple Space Model Models � Tuple : collection of data � <15, “str”, false> Agilla Lim one � Tuple space : shared data space containing tuples � Template : patterns which match tuples � Simple bytecode � Java programming <15, *, false> matches <15, “str”, false> � language language � Hosted on custom VM � Hosted on Java VM � Common tuple space operations: � Handful of well-known � Rich data types � out(t) : add tuple t to tuple space data types � rd(T) : copy tuple matching template T from tuple space � in(T) : remove tuple matching template T from tuple space � react(T, c): execute code segment C when tuple matching template T is placed in tuple space 25 26 Agimone Agimone Services � Shared data space � AgimoneAgent has own Agilla TS � Agilla agents access TS directly � AgimoneAgent wraps Agilla TS in Limone TS API � Sensor network discovery � AgimoneAgent advertises self with Limone Registry � Limone Registry distributes ad to other AgimoneAgents � Ads stored in AgimoneAgent’s Agilla tuple space Network Architecture System Components 27 28 Agimone Services (Continued) Cargo Tracking Revisited � � Inter-Network Migration Watchdog Agents � Monitors sensors � Multi-step process � Sends alert tuple to base station � Though internally � Port authority’s Limone agent complex, appears simple reacts to it to Agilla agent developer � 17 lines of Agilla code, 11 lines of Java code � Intrusion Search Agent � Searches multiple WSNs for alert tuples • Autonomously crosses WSN boundaries � 23 lines of Agilla code, no additional Java code 29 30 5
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