17-09-2012, 05:13 PM
Exploration and Comparison of Several AODV Implementations: A Survey
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ABSTRACT
An ad-hoc network consists of mobile nodes constructing a network that the topology changes dynamically. The Ad-hoc On Demand Distance Vector Routing (AODV) protocol is an algorithm used for the implementation of such networks. The connection between nodes is established for the duration of one session, so no need to have a base station in order to establish such a connection between nodes. Nodes discover other target nodes that are out of range by broadcasting the network with Rout Requests (RREQ) that are forwarded by each node. If the destination node get the RREQ, then it sends back Route Reply (RREP) to the source node. After the route has been discovered between source node and destination node, then it’s the time to start sending data thru that route. This paper is an exploration and comparison of several AODV implementations including: Mad-hoc, AODV-UCSB, AODV-UU, Kernel-AODV and AODV-UIUC.
INTRODUCTION
The Ad hoc On-Demand Distance Vector (AODV) routing protocol is designed for mobile ad hoc networks (MANETs) and other wireless ad-hoc networks with large numbers of mobile nodes. The protocol's algorithm creates routes between nodes only when the routes are requested by the source nodes, giving the network the flexibility to allow nodes to enter and leave the network as will. Routes remain active only as long as data packets are traveling along the paths from the source to the destination. If the source stops sending packets, the path will time out and close. AODV was developed at the Nokia Research Center of University of California, Santa Barbara and University of Cincinnati by C. Perkins and S. Das [1].
HOW AODV WORKS
AODV utilizes routing tables to store routing information; one routing table for uncast routes as well as one for multicast routes. These tables hold information like: destination address, next-hop address, hop count, destination sequence number, and life time.
AODV discovers routes as needed and when it is necessary, which means no need to maintain routes from every node to all other nodes. And routes should be maintained as long as it’s necessary. AODV nodes have four types of messages to communicate between each other:
• Route Request (RREQ)
• Route Reply (RREP).
• Route Error (RERR)
• HELLO messages.
ADVANTAGES AND DISADVANTAGES OF EACH IMPLEMENTATION
There are a lot of advantages and disadvantages of AODV protocols. One advantage of AODV is that it doesn’t create extra traffic for communication among existing links, that’s because routes are established on demand and destination sequence numbers are used to find the latest route to the destination. Also connection setup delay is less. In addition, distance vector routing is simple, and it doesn't require much memory or calculation. However AODV requires more time to establish a connection, and the initial communication to establish a route is heavier than some other approaches. In contrast of DSR, the source node and the intermediate nodes of AODV store the next-hop information corresponding to each flow for data packet transmission.
CONCLUSION
AODV is currently one of the most popular ad-hoc routing protocols. These indicate that AODV performs very well both during high mobility and high network traffic load, making it one of the most interesting candidates among today’s ad-hoc routing protocols.
Several independent AODV implementations exist, such as AODV-UU, Kernel-AODV, AODV-UCSB, AODV-UIUC, and Mad-hoc AODV. This paper discussed advantages and disadvantages of each implementation. Finally, the AODV-UU installation/configuration on NS-2 has been explained in details.