Ad-hoc On-demand Distance Vector
From Wikipedia, the free encyclopedia
The Ad-hoc On-demand Distance Vector (AODV) routing algorithm is an algorithm for routing data across Wireless Mesh Networks. It is capable of both unicast and multicast routing. It is a reactive routing protocol, meaning that it establishes a route to a destination only on demand. In contrast, the most common routing protocols of the Internet are proactive, meaning they find routing paths independently of the usage of the paths. AODV is, as the name indicates, a distance-vector routing protocol.
In AODV, the network is silent until a connection is needed. At that point the network node that needs a connection broadcasts a request for connection. Other AODV nodes forward this message, and record the node that they heard it from, creating an explosion of temporary routes back to the needy node. When a node receives such a message and already has a route to the desired node, it sends a message backwards through a temporary route to the requesting node. The needy node then begins using the route that has the least number of hops through other nodes. Unused entries in the routing tables are recycled after a time.
When a link fails, a routing error is passed back to a transmitting node, and the process repeats.
Much of the complexity of the protocol is to lower the number of messages to conserve the capacity of the network. For example, each request for a route has a sequence number. Nodes use this sequence number so that they do not repeat route requests that they have already passed on. Another such feature is that the route requests have a "time to live" number that limits how many times they can be retransmitted. Another such feature is that if a route request fails, another route request may not be sent until twice as much time has passed as the timeout of the previous route request.
The advantage of AODV is that it creates no extra traffic for communication along existing links. Also, distance vector routing is simple, and 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.
For other alternatives see the Ad hoc routing protocol list.
[edit] See also
[edit] External links
- AirMatrix Manufacturer of High Quality, Commercial Grade Mesh Nodes based on LocustWorld Pro Firmware.
- LocustWorld An open source meshap offering for community networks as well as commercial offerings.
- RFC 3561 AODV - the specification
- http://moment.cs.ucsb.edu/AODV/aodv.html
- Cambridge Matrix recommends AODV mesh routing
- Solar Mesh AP Don Moskaluk experiment with Solar and Ad-hoc On-demand Distance Vector using Locustworld's AODV
