Dipanjan Chakraborty Anupam Joshi CSEE University of Maryland Baltimore County

1. Dipanjan ChakrabortyAnupam JoshiCSEEUniversity of Maryland Baltimore County Anamika: Distributed Service Discovery and Composition Architecture for Pervasive Environments

7. Service I am Wireless LAN enabled!! Blender!! I have GPS service!!

8. Service Discovery Are you a Toaster ?? I am looking for a printer!! Do you have MP3 songs?

9. Definitions • “Service” • Hardware or software entity residing on any device or platform • Has distinct functional description • Can be utilized by other services/clients • “Service Discovery” • Process of discovering the availability of a service in the neighborhood • “Service Composition” • Integration and execution of multiple services in the planned order to satisfy a request

10. Ad hoc Environment • Network formed by multiple heterogeneous nodes in the reachable vicinity of one another • Some nodes are mobile, some are not • Environment around a device changes dynamically • Services exist on those devices

11. Issues of Service Discovery in an Ad hoc Environment • Discovery Architecture • Registry-based/centralized/semi-centralized • In Ad hoc Environment • Global request broadcasting • Global Advertisement and caching • Discovery method • Unique identifier/Interfaces/attributes • Language/network independence • Scalability

12. Issues of Service Composition in Ad hoc Environments • Services are distributed in the Environment • Efficient Service Discovery • Composition needs to be done in a de-centralized manner • Fault tolerance and graceful recovery • Solution should efficiently utilize node/service topology

13. Application Layer Service Integration Layer Service Execution Layer Broker Arbitration and Delegation Fault Recovery Module Network Layer (DSDV/AODV/CSGR etc) General Architecture Planner Service Discovery Layer (Bluetooth SDP, Salutation-lite etc)

14. Anamika: System Components

15. Anamika: Network Manager • Communication between Bluetooth peers done over RFCOMM • Connect-transmit-disconnect mode of operation • Segmentation and reassembly of Anamika messages • Implementation done on IBM’s Bluedrekar transport driver

16. Anamika: Service Discovery • Peer-to-peer service discovery (Group-based Service Discovery) • Dynamic caching of discovered services in peers • Semantic description based service matching (using DAML-S and DReggie Ontology) • Service Discovery also provides invocation information

17. GSD Protocol Summary • GSD= Group-based Service Discovery • Peer-to-peer caching of service advertisements • No global advertisements • No global request broadcast • Describe services semantically in DARPA Agent Markup Language (DAML) • Enhance service matching mechanism based on semantic description

18. GSD Protocol Summary • Class/subClass hierarchy of DAML used to classify services to different groups based on functionality • Intelligently forward requests to appropriate nodes • Prevent request flooding • Efficient in terms of bandwidth usage and discovering a service in a MANET

19. Group-based Request Routing

20. Service Composition Techniques • “Request Processor” uses DAML-S to model Composition Knowledge • Dynamic Broker Selection Technique • No assumption about the platform of the broker/central entity • Broker Arbitration and Delegation • Source of the request starts a process which decides the broker platform • Parameters based on current processor usage, memory capability, longevity, services available in its vicinity etc

21. Dynamic Broker Selection Technique (contd) • Broker discovers *all* the required services • Fault tolerance • Source-monitored fault-tolerance • Assumption: Source remains ‘alive’ all the time • Periodic ‘checkpoints’ being sent to the source • Source issues a new composition request in case of failure

22. Service Composition Techniques • Distributed Brokering Technique • Broker Arbitration and Delegation • Requester is responsible to determine the ‘first’ broker • Parameters to select a broker are similar to the ‘dynamic Broker selection’ mechanism • More emphasis on services that are needed ‘immediately’ • ‘first’ broker not responsible for the whole composition • Composes only ‘as much’ as it can • ‘radius’ of composition is small • ‘first’ broker selects another broker when it has completed the ‘partial’ composition

23. Distributed Brokering Technique (contd.) • Fault Recovery • Similar to the one used in ‘dynamic entity selection’ mechanism • Each broker keeps the client informed about the partial state of composition and execution • Client issues a new composition request with the subset that is remaining

24. Results • Simulation carried in Glomosim simulator • 25 to 100 nodes • Movement pattern=random way-point • Radio Range of each node=31 meters

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30. Future Work • Simulation of the whole composition architecture • Implementation of a pro-active service discovery and composition architecture • Mathematical modeling of the discovery and composition process