2 June 2004MJ Blange, IP Karkowski, BCB Vermeulen 1

TNO Physics and Electronics Laboratory

Service Discovery inHeterogeneous Wireless Networks

International Workshop on Wireless Ad-hoc Networks

IWWAN, 2 June 2004IP Karkowski 2

Overview• Possible approaches to handling vertical handovers.• SPEARS architecture.• Service discovery concepts in SPEARS.• Implementation details.• Experimental results.• Conclusions and future work.

IWWAN, 2 June 2004IP Karkowski 3

Vertical handovers• Lower levels of the OSI protocol stack.• IP layer.• Middleware layer between networking protocols and

application.

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LAN

The SPEARS architectureCurrent implementation based on:• Within IMT: Bluetooth (PAN)• Between IMT’s: WiFi ad-hoc network (LAN)• Public network: GPRS (WAN)

GPRS basisstation

WAN

PAN

PAN

PAN

PAN

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Motivation• Robustness• No central server• Flexibility of the network configuration.

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Service discovery middleware• Services• Lookup servers

• Global lookup server (WAN)• Local lookup servers (LAN)

• Registration of services• Usage of services

SERVICEPROVIDER

SERVICEREQUESTER

FIND

SERVICEREGISTRY

SERVICEREGISTRY

SERVICEDESCRIPTION

INTERACT

PUBLISH

SERVICEPROVIDER

REQUESTER

SERVICEPROVIDER

REQUESTER

FIND

PUBL

ISH

SERVICEDESCRIPTION

SERVICE

CLIENT

FIND

PUBLISH

SERVICEDESCRIPTION

SERVICE

CLIENT

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Service / Network Outage (Case 1)

LAN

WAN

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Service / Network Outage (Case 2)

WAN

LAN

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Service / Network Outage (Case 3)

WAN

LAN

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SPEARS Implementation of ServiceDiscoveryEssential 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.

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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 ableto see which service version (LAN or WAN) they areabout to use.• Services annotated with an attribute indicating service type.

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Experimental results

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Conclusions• Vertical handovers at middleware layer.• Practical implementation in Jini.