Service Discovery in Heterogeneous Wireless Networks TNO Physics - PowerPoint PPT Presentation

International Workshop on Wireless Ad-hoc Networks Service Discovery in Heterogeneous Wireless Networks TNO Physics and Electronics Laboratory MJ Blange, IP Karkowski, BCB Vermeulen 2 June 2004 1

Overview • Possible approaches to handling vertical handovers. • SPEARS architecture. • Service discovery concepts in SPEARS. • Implementation details. • Experimental results. • Conclusions and future work. IP Karkowski IWWAN, 2 June 2004 2

Vertical handovers • Lower levels of the OSI protocol stack. • IP layer. • Middleware layer between networking protocols and application. IP Karkowski IWWAN, 2 June 2004 3

The SPEARS architecture WAN Current implementation based on: GPRS basisstation • Within IMT: Bluetooth (PAN) • Between IMT’s: WiFi ad-hoc network (LAN) • Public network: GPRS (WAN) PAN PAN PAN LAN PAN IP Karkowski IWWAN, 2 June 2004 4

Motivation • Robustness • No central server • Flexibility of the network configuration. IP Karkowski IWWAN, 2 June 2004 5

Service discovery middleware • Services • Lookup servers • Global lookup server (WAN) • Local lookup servers (LAN) SERVICE DESCRIPTION • Registration of services SERVICE SERVICE REGISTRY REGISTRY • Usage of services SERVICE PUBLISH PUBLISH PUBLISH FIND FIND FIND CLIENT SERVICE SERVICE DESCRIPTION SERVICE SERVICE SERVICE SERVICE PROVIDER PROVIDER CLIENT INTERACT REQUESTER PROVIDER REQUESTER REQUESTER SERVICE DESCRIPTION IP Karkowski IWWAN, 2 June 2004 6

7 IWWAN, 2 June 2004 Service / Network Outage (Case 1) WAN LAN IP Karkowski

8 IWWAN, 2 June 2004 Service / Network Outage (Case 2) LAN WAN IP Karkowski

9 IWWAN, 2 June 2004 Service / Network Outage (Case 3) LAN WAN IP Karkowski

SPEARS Implementation of Service Discovery Essential requirements: • Multicasting support. • Restricting multicast to LAN. • Routing of IP packages between mobile nodes through WAN. Highlights: • Combination of AODV & Mobile IP. • Based on Jini™ from Sun Microsystems. • SPEARS specific extensions. IP Karkowski IWWAN, 2 June 2004 10

Implementation aspects • ‘Codebase’ problem - must be different in WAN and LAN registrations. • SpearsClassLoader • setCodebase() member function. • First register at WAN, then LAN. • Service type identification - applications must be able to see which service version (LAN or WAN) they are about to use. • Services annotated with an attribute indicating service type. IP Karkowski IWWAN, 2 June 2004 11

Experimental results IP Karkowski IWWAN, 2 June 2004 12

Conclusions • Vertical handovers at middleware layer. • Practical implementation in Jini. IP Karkowski IWWAN, 2 June 2004 13