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Aodv guide 1 A Quick Guide to AODV Routing Node Node Node Node Luke Klein-Berndt Wireless Communications Technologies Group National Institute of Standards and Technology CAODV is a method of routing messages between mobile computers It allows these mobil

A Quick Guide to AODV Routing Node Node Node Node Luke Klein-Berndt Wireless Communications Technologies Group National Institute of Standards and Technology CAODV is a method of routing messages between mobile computers It allows these mobile computers or nodes to pass messages through their neighbors to nodes with which they cannot directly communicate AODV does this by discovering the routes along which messages can be passed AODV makes sure these routes do not contain loops and tries to ?nd the shortest route possible AODV is also able to handle changes in routes and can create new routes if there is an error The diagram to the left shows a set up of four nodes on a wireless network The circles illustrate the range of communication for each node Because of the limited range each node can only communicate with the nodes next to it A Quick Guide to AODV Routing Node Node Message Node Node Node Node wants to send a message to Node Unfortunately it is unsure of the route to get there CNodes you can communicate with directly are considered to be Neighbors A node keeps track of its Neighbors by listening for a HELLO message that each node broadcast at set intervals When one node needs to send a message to another node that is not its Neighbor it broadcasts a Route Request RREQ message The RREQ message contains several key bits of information the source the destination the lifespan of the message and a Sequence Number which serves as a unique ID In the example Node wishes to send a message to Node Node ? s Neighbors are Nodes Since Node can not directly communicate with Node Node sends out a RREQ The RREQ is heard by Node and Node A Quick Guide to AODV Routing Since Node is not a Neighboring node Node has to discover a route It does this by generating a Route Request and broadcasting it Dest Node A packet of data Neighbors Node Node Node Route Request Packet Dest Node Src Node Lifespane ID Node RREQ Node RREQ Node CWhen Node ? s Neighbors receive the RREQ message they have two choices if they know a route to the destination or if they are the destination they can send a Route Reply RREP message back to Node otherwise they will rebroadcast the RREQ to their set of Neighbors The message keeps getting rebroadcast until its lifespan is up If Node does not receive a reply in a set amount of time it will rebroadcast the request except this time the RREQ message will have a longer lifespan and a new ID number All of the Nodes use the Sequence Number in the RREQ to insure that they do not rebroadcast a RREQ In the example Node has a route to Node and replies to the RREQ by sending out a RREP Node on the other hand does not have a route to Node so it rebroadcasts the RREQ A Quick Guide