INTERNET AND ADHOC SERVICE DISCOVERY BY: NEHA CHAUDHARY

Mobile ad hoc networks are characterized by their highly dynamic, multi-hop, and infrastructure-less nature. In this dynamic environment, different nodes offering different services may enter and leave the network at any time. Efficient and timely service discovery is a prerequisite for good utilization of shared resources on the network.

Service discovery allows devices to automatically locate network services with their attributes and to advertise their own capabilities to the rest of the network.

Challenges in service discovery in MANET The first challenge is enabling resource- constrained, wireless devices to discover services dynamically. The second one is enabling service discovery in large mobile ad hoc networks.

SERVICE DISCOVERY ARCHITECTURE CENTRALIZED DIRECTORY ARCHITECTURE DIRECTORY-LESS ARCHITECTURE DIRECTORY-BASED ARCHITECTURE. DISTRIBUTED DIRECTORY ARCHITECTURE. INFRASTRUCTURE-LESSINFRASTRUCTURE-BASED

CENTRALIZED DIRECTORY ARCHITECTURE 1.SLP 2.Jini 3.Salutation

SERVICE LOCATION PROTOCOL(SLP) The Service Location Protocol (SLP) is a service discovery Protocol that allows computers and other devices to find services in a local area network without prior configuration. Each service must have a URL that is used to locate the service. Additionally it may have an unlimited number of name/value pairs, called attributes.

SLP has two different modes of operation: ( 1) when a DA is present, it collects all service information advertised by SAs, and UAs unicast their requests to the DA. (2) when there is not a DA, UAs repeatedly multicast the request. SAs listen for these multicast requests and unicast responses to the UA.

SLP provides a flexible and scalable framework for providing hosts with access to information about the existence, location, and configuration of networked services by scope mechanism. SLP uses service scope, which is a collection of services within certain domain, to achieve scalability.

SLP ROLES SLP has three different roles for devices. User Agents (UA) are devices that search for services. Service Agents (SA) are devices that announce one or more services. Directory Agents (DA) are devices that cache services.

Client UA Service SA DA Service Request(multicast) Service Reply Service register Service ACK Service reply Service REQ

VerTypeLenFlags ExtOffsetXID LangLenLang SLP Data The SLPv2 packet structure

Jini It provides a platform for clients to locate services. The purpose of a Jini system is to federate users, devices and services into a distributed system. The notion of a service is the central concept of Jini. A service (represented as Java object) is a software entity providing any kind of computation or controlling a hardware device.

Each Jini subsystem contains a set of lookup services that maintains the dynamic information about services in network. Clients can use Jini lookup services or download java code to access the services.

SALUTATION Salutation is the major cooperation architecture to solve the problems of service discovery and utilization among the appliances/equipment in an environment of widespread connectivity and mobility. The Salutation architecture defines an entity called the Salutation Manager (SLM).

Functions of SLM Service registry Service discovery Service availability Service session management

Service location architecture Service co-ordinator based architecture Distributed query based architecture Hybrid service location architecture

SERVICE CO-ORDINATOR BASED ARCHITECTURE In this architecture the node which is better equipped acts as Service co-ordinator. It acts as service collection point SCs broadcast their presence in the n/w so that servers in the neighborhood are aware of the SCs. Server register their services and access information with the SCs

If advertisement scope is too narrow this will result in less service registered.(less burden on SC) If scope of advertisement is too wide it results in more control traffic because more servers replying to SCs. Validity of the SCs over time and space is reflected by frequency of advertisement send by SCs. Updation of the list of the services is reflected by frequency of the registration by server

DISTRIBUTED QUERY BASED ARCHITECTURE No service coordinator Client broadcast the service query to the neighbours. Server that receive the query will send the directed reply The success of service search depend on the scope of the broadcast and also the percentage and location distribution of server in the network

Hybrid service location architecture It improves the service availability by using distributed approach And improves the scalability by using SC based scheme. Service availability defines how many service query request made by client can be fulfilled by SCs or server in the network.