01-09-2012, 01:00 PM
Ad hoc On-demand Distance Vector (AODV) Routing Protocol
AODV.ppt (Size: 964.5 KB / Downloads: 209)
AODV Overview
AODV is a packet routing protocol designed for use in mobile ad hoc networks (MANET)
Intended for networks that may contain thousands of nodes
One of a class of demand-driven protocols
The route discovery mechanism is invoked only if a route to a destination is not known
UDP is the transport layer protocol
Source, destination and next hop are addressed using IP addressing
Each node maintains a routing table that contains information about reaching destination nodes.
Each entry is keyed to a destination node.
Routing Table Fields
Destination IP address
Destination Sequence Number
Valid Destination Sequence Number Flag
Other state and routing flags
Network Interface
Hop Count (needed to reach destination)
Next Hop
Precursor List
Lifetime (route expiration or deletion time)
AODV Operation – Message Types
RREQ Messages
While communication routes between nodes are valid, AODV does not play any role.
A RREQ message is broadcasted when a node needs to discover a route to a destination.
As a RREQ propagates through the network, intermediate nodes use it to update their routing tables (in the direction of the source node).
The RREQ also contains the most recent sequence number for the destination.
A valid destination route must have a sequence number at least as great as that contained in the RREQ.
Congestion Handling
Other possible methods to improve AODV congestion handling:
A route may predict when congestion is about to occur and try to avoid it by reduce the transmission rate.
Schedule the requests so that it will not overload the network.
Information “Freshness” Assured
AODV depends on each node in the network to own and maintain its destination sequence number.
A destination node increments its own sequence number immediately before it originates a route discovery
A destination node increments its own sequence number immediately before it originates a RREP in response to a RREQ
The node treats its sequence number as an unsigned number when incrementing accomplishing sequence number rollover.
Destination information is assured by comparing the sequence number of the incoming AODV message with its sequence number for that destination.
AODV.ppt (Size: 964.5 KB / Downloads: 209)
AODV Overview
AODV is a packet routing protocol designed for use in mobile ad hoc networks (MANET)
Intended for networks that may contain thousands of nodes
One of a class of demand-driven protocols
The route discovery mechanism is invoked only if a route to a destination is not known
UDP is the transport layer protocol
Source, destination and next hop are addressed using IP addressing
Each node maintains a routing table that contains information about reaching destination nodes.
Each entry is keyed to a destination node.
Routing Table Fields
Destination IP address
Destination Sequence Number
Valid Destination Sequence Number Flag
Other state and routing flags
Network Interface
Hop Count (needed to reach destination)
Next Hop
Precursor List
Lifetime (route expiration or deletion time)
AODV Operation – Message Types
RREQ Messages
While communication routes between nodes are valid, AODV does not play any role.
A RREQ message is broadcasted when a node needs to discover a route to a destination.
As a RREQ propagates through the network, intermediate nodes use it to update their routing tables (in the direction of the source node).
The RREQ also contains the most recent sequence number for the destination.
A valid destination route must have a sequence number at least as great as that contained in the RREQ.
Congestion Handling
Other possible methods to improve AODV congestion handling:
A route may predict when congestion is about to occur and try to avoid it by reduce the transmission rate.
Schedule the requests so that it will not overload the network.
Information “Freshness” Assured
AODV depends on each node in the network to own and maintain its destination sequence number.
A destination node increments its own sequence number immediately before it originates a route discovery
A destination node increments its own sequence number immediately before it originates a RREP in response to a RREQ
The node treats its sequence number as an unsigned number when incrementing accomplishing sequence number rollover.
Destination information is assured by comparing the sequence number of the incoming AODV message with its sequence number for that destination.