Zone Routing Protocol (ZRP)

Routing protocols for mobile ad-hoc networks have to face the challenge of frequently changing topology, low transmission power and asymmetric links. Both proactive and reactive routing protocols prove to be inefficient under these circumstances. The Zone Routing Protocol (ZRP) combines the advantages of the proactive and reactive approaches by maintaining an up-to-date topological map of a zone centered on each node. Within the zone, routes are immediately available. For destinations outside the zone, ZRP employs a route discovery procedure, which can benefit from the local routing information of the zones. This paper presents the Zone Routing Protocol. First, we discuss the problem of routing in ad-hoc networks and the motivation of ZRP. We describe the architecture of ZRP, which consists of three sub-protocols. We describe the routing process and illustrate it with an example. Further, we describe the query control mechanisms, which are used to reduce the traffic amount in the route discovery procedure. ZRP does not define the actual implementation of the protocol components. Therefore, we present the guidelines for implementation, and example implementations provided in the draft specifications. We discuss the problem of routing in networks with unidirectional links, and the proposal for a solution to it. The overhead of the routing protocol is important in the power and bandwidth limited ad-hoc networks. We discuss the factors influencing on the traffic amount based on measurements performed in a number of papers. We describe the significant issue of choosing an optimal zone radius, and two algorithms for automatic selection of the radius. Finally, we draw some conclusions about the performance of the protocol. The paper is based on literature research.