Performance Comparison of Ad Hoc Routing Protocols: An ...

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knows the whole path from the source to the destination node (called Source-Routing) and includes the addresses of the intermediate nodes of the route in the packets. DSR does not use hello-messages between the nodes to notify their neighbors of their presence. DSR basically is based on the Link-State-Algorithms [11], in which each node is capable of saving the best route to a destination. Also if a change appears in the network topology, then the whole network will get this information by flooding. 2. Ad hoc On demand Distance Vector (AODV): The Ad hoc On demand Distance Vector (AODV) routing algorithm is also designed for MANETs. It is an on demand algorithm, meaning that it maintains routes as long as they are needed by the sources. AODV uses sequence numbers to ensure the freshness of routes [3]. These routes are loop-free, self-starting, and scale to large numbers of mobile nodes. 3. Temporally-Ordered Routing Algorithm (TORA): The Temporally-Ordered Routing Algorithm (TORA) is an algorithm for routing data across MANETs. TORA does not use a shortest path to the greatest extent possible for message propagation. TORA generates and maintains a Directed Acyclic Graph rooted at a destination. No three nodes can have the same height. Data can flow from nodes with higher heights to nodes with lower heights, meaning that data can only flow downhill and can not flow back to the source [6, 13]. By maintaining a set of totally-ordered heights at all times, TORA achieves loop-free routing. t time of a link failure oid originator id r reflection bit indicates 0=original level 1=reflected level d integer to order nodes relative to reference level i the nodes id The triplet (t, oid, r) is called the reference level. And the tuple (d, i) is an offset within that reference level. Each node maintains a neighbor table containing the height of the neighbor nodes. Initially the height of all the nodes is NULL and their quintuple is (-,-,-,-,i). The height of a destination neighbor is (0, 0, 0, 0, dest). EVALUATION We used simulation to evaluate the three routing algorithms. The algorithms were implemented using ten mobile nodes in a predefined network. In this network the source node is 0, and the destination node or sink is 1. In all three algorithms, the initial route for data transmission is 0-3- 4-7-1 as shown in figures 1 and 2. But as the transmission progresses the nodes move, resulting in the new and different route shown in figure 3. The random movement model is used for nodes movement. The performance metrics addressed are the throughput of sending/receiving bits, throughput of dropping bits, throughput of sending bits versus average simulation end to end delays, and throughput of sending bits versus average simulation jitter. SIMULATION ENVIRONMENT The ns-2 simulator [1, 12] was used for the study. The hosts are placed on a square field of 600m x 600m. The protocol used for data transmission is TCP/UDP. Acknowledgment Packets are also TCP/UDP. Any source-destination (S-D) pair could be chosen for data transmission. The packet size is 24 bytes. Each connection starts at a time from 1 simulated second and the simulation runs for 150 simulated seconds.
PERFORMANCE ANALYSIS Figure 1 Initial state of nodes The performance of the algorithms was evaluated using the ns-2 simulator. The following key issues are addressed: 1. Throughput of sending bits/receiving bits. 2. Throughput of dropping bits. 3. Throughput of sending bits versus average simulation end to end delays. 4. Throughput of sending bits versus average simulation jitter. Figure 2 Initial route when data transmission starts from source 0 to destination 1
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