Service*: Distributed Service Advertisement for Multi-Service, Multi-Hop MANET Environments

We consider the problem of service advertisement when multiple services are available in a MANET. We present Service*, a novel distributed service advertisement protocol that uses a push-based mechanism to optimally place services in a dynamically selected subset of available nodes, called brokers. Such a dynamic arrangement of broker nodes is shown to have good scalability characteristics as the number of services and nodes increase and enables discovery queries to be satisfied with high probability using only single-hop broadcasts. The approach reduces message overhead by eliminating network-wide packet dissemination while maintaining a high service discovery ratio. The protocol is distributed in that it does not require the use of any centralised infrastructure. Instead, nodes initiating an advertising session use local rules to select a minimal subset of their 1-hop neighbours and delegate to them the task of acting as service brokers. We describe the protocol and present simulation results that exhibit a high discovery ratio with only a fractional overhead as compared to two other advertising protocols that utilise a pure and an optimised flooding approach.