International Journal of Computer Applications (0975 – 8887) Volume 99 – No.14, August 2014 42 A Survey on Various Enhancements Made on ZRP Kanishka Raheja Mtech Scholar Department of CSE, BRCM-CET (Bahal), India Sunil Kr Maakar Assistant professor Department of CSE, BRCM-CET (Bahal), India ABSTRACT MANET is a self organizing and self configurable infrastructure less network of mobile nodes connected by wireless where the nodes move arbitrarily. Routing is a critical issue in Mobile Ad Hoc Networks. One of well- known protocol for Ad hoc networks is Zone Routing Protocol. However, many useless control packets are used resulting in the increase of network load and decrease of network performance. This paper studies various enhancements that have been made on ZRP to improve its performance. Keywords MANET, ZRP, cache, IARP, IERP 1. INTRODUCTION A Mobile Ad hoc Network (MANET) is a formation of the network instantaneously and dynamically with the collection of wireless mobile nodes that operates without the support of any fixed network infrastructure [3]. Much work has been done on routing in MANETs .Many protocols and algorithms such as Destination- Sequenced Distance-Vector (DSDV) protocol, Cluster-based routing algorithms, Dynamic Source Routing (DSR) protocol, Ad hoc On-demand Distance-Vector (AODV) protocol, Zone Routing Protocol (ZRP), Temporally Ordered Routing Algorithm (TORA), and Associative Bit Routing (ABR) have been proposed. Among these protocols, the ZRP has a wide application [4]. However, when the protocol searches for a new route, it sends many useless control packets, which increase the network load and decrease the network performance. In this paper we propose various enhancements that are made on ZRP. Existing Ad-hoc routing protocols can be classified into two groups: proactive and reactive routing protocols. Proactive routing protocols attempt to continuously evaluate the routes within the network, so that when a packet needs to be forwarded, the route is already known and can be immediately used. Reactive protocols invoke a route determination procedure on an on-demand basis. 1.1 ZRP The comparison of proactive and reactive scheme shows that there is needed a protocol that combines the advantages of proactive and reactive protocol. The ZRP [1] is a hybrid reactive/proactive scheme. In ZRP, a node proactively maintains routes destinations within a local neighborhood, which is considered as a routing zone. A node routing zone is defined as a collection of nodes whose minimum distance hop from the node is no greater than a parameter referred to as the zone radius. Each node maintains its own routing zone, but the routing zones of neighborhood nodes overlap. If a node want to communicate with in its zone it can communicate proactively and the IntrAzone Routing Protocol (IARP) is used and IntErzone Routing Protocol (IERP) for routing beyond the routing zone.ZRP uses the concept of border casting a node such as if a node cannot find its destination with in a zone it sends the packets to its peripheral nodes of the routing zone and then that node is responsible for searching the destination to its own zone proactively. This process continues until the source finds its destination. The reactive routing process is divided into two phases: the route request phase and the route reply phase. ZRP performs better than any single proactive or reactive protocol [4].But its performance can be further improved by enhancing this protocol. This paper presents various enhancements which have been made in ZRP. 1.1.2 Analysis ZRP is better suitable for the large networks. The performance of protocol has been adjusted accordingly. However, many useless control packets are used resulting in the increase of network load and decrease of network performance. In the reactive protocol, the IERP request packets are sent to all border nodes. The IERP packets are necessary for searching a route. However, these packets may cause a network congestion resulting in the decrease of network performance. In the real communication situations, the data transmission may happen many times to the same DN. But in such situation, in ZRP the border-cast route searching is carried out to all destinations. 2. A CACHING SCHEME FOR ROUTING IN MOBILE AD HOC NETWORKS AND ITS APPLICATION TO ZRP ZRP is based on the notion of a zone. Each node n is the center of a zone with radius k hops, denoted Z k (n). Nodes at a distance lesser than or equal to k from n belong to Z k (n). A proactive protocol is used among the nodes of Z k (n). A reactive protocol is used by n to reach a node outside its zone. Practically, k is set to a value much smaller than the network diameter to get a fast convergence of the proactive component of ZRP and a low routing protocol overhead. Therefore, the probability that a sender selects a destination out of its zone is high, thus, again, caching is useful to reduce path discoveries of the reactive part of ZRP. Whenever a route to a destination out of the zone is to be discovered then that route is to be cached for further usage [5]. The simplest form of caching is based on timeouts associated with cache entries. When an entry is cached, a timer starts. When the timeout elapses, the entry is removed from the cache. Each time the entry is used, the timer restarts. Therefore, the effectiveness of such a scheme depends on the timeout value associated with a cached route. If the timeout is well-tuned, the protocol performance increases; otherwise, a severe degradation arises as entries are removed either prematurely or too late from the cache. This cache scheme can not only be applied for ZRP but it can be applied for other reactive protocols like AODV.