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

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.