The Mobile Ad hoc Network (MANET) is a collection of connected mobile nodes without any centralized administration. Proactive routing approach is one of those categories of proposed routing protocol which is not suitable for larger network due to their high overhead to maintain routing table for each and every node. The novelty of this approach is to form a binary tree structure of several independent sub-networks by decomposing a large network to sub-networks. Each sub-network is monitored by an agent node which is selected by several broadcasted regulations. Agent node maintains two routing information; one for local routing within the sub-network and another for routing through all other agent node. In routing mechanism first source node checks for destination within sub-network then source sends destination address to respective parent agent node if destination is not available in local routing, this process follows up to the destination node using agent mode. This approach allowed any proactive routing protocol with scalability for every routing mechanism. The proposed approach is thoroughly analyzed and its justification for the connectivity through sub-networks, routing between each source to destination pair, scalability, etc., are given, which show expected performance.
TopIntroduction
Mobile ad hoc networks (MANETs) (Spojmenovic, 2002) are autonomous system, multi-hop wireless network without requiring any existing infrastructure. This type of networks is designed by number of mobile nodes connected through wireless links. In MANETs, two nodes can directly communicate with each other when they are within radio range. Otherwise, intermediate nodes are required to relay messages to neighboring nodes along the path from source to destination. Ad hoc networks (Spojmenovic, 2002) are characterized by frequent changes and mobile nodes may join the network, disconnect or move at any time. These problems make the routing problem in ad hoc networks more difficult than traditional wired networks.
This kind of network is most usable for environments where nodes are frequently changing and low bandwidth available, such as moving vehicles in battlefield. Many restrictions should be well considered, such as limited power and bandwidth. Mobile ad hoc networks are suitable for proper communication in military and also used to play an important role in many fields without the use of a fixed infrastructure such as disaster search-and-rescue operations, data acquisition in remote areas, conference and convention centers etc.
One of the major issues related to MANET implementation is the routing. The major routing approaches are obtained into this area are the well-known DSDV (Perkins, 1994) in proactive and the AODV (Chiang & Gerla, 1997) in reactive routing protocols. In MANET, every node operated as a router as well as node also, maintaining individually routes to other nodes. If the number of nodes increases, the routing overhead will increase rapidly. In order to support multi-hop routing (Chiang & Gerla, 1997), there are several different protocols have been proposed. There are different standards to divide these routing protocols in different category: proactive routing versus reactive routing or flat routing versus cluster based routing and so on.
In proactive protocols (Spojmenovic, 2002; Royer & Toh, 1999) routes between every pair of nodes are established in advance even if no data transmission is required. Routes to all destinations are updated periodically. These routing protocols maintain consistent, up-to-date routing information for every pair of source and destination in the network. These protocols require to maintaining one or more tables for routing information, and they respond to frequently changes in network topology by propagating updates throughout the network to maintaining a consistent updates of network. In contrast, on demand (reactive) protocols (Spojmenovic, 2002; Royer & Toh, 1999) establish the route to a destination only when data transmission is required. Thus, a node broadcast route request packet to the network and waits for the route reply message to form a route to the destination node. This routing protocol reduces the routing load as compared to the proactive protocols.
In flat routing protocol, each pair of source and destination communicate through peer-to-peer relationship and participating in routing equally. Routing algorithm is easily implemented. However, it is having poor performance in terms of scalability (Iwata, Chiang, Pei, Gerla, & Chen, 1999) in a certain extent. For example, DSDV (Perkins, 1994; Rahman & Zukarnain, 2004), DSR (Broch & Malts, 1998) and AODV (Rahman & Zukarnain, 2004) are typical flat routing protocols. The hierarchical (Spojmenovic, 2002; Pei, Gerla, & Hong, 1999) routing protocol communicates through so many sub-networks forming by dividing the whole network into many logical areas. There are different routing strategies are used inside and outside the logical area. Compared with flat routing protocol, the hierarchical routing protocol possesses better performance and is propitious to support scalable networks. At present, the growing interest in wireless ad hoc network techniques has resulted in many hierarchical routing protocols such as ZRP (Haas & Peariman, 2001), each routing protocol having its own advantages and drawbacks. Research is continued on commendably satisfying the demands of multi-hop wireless ad hoc networks on the aspects of scalability, less routing overhead, and complexity.