User Manual

NovaRoam EH900 User Manual
V. 1.1
Page 66
RREP back to the source node. Otherwise, it rebroadcasts the RREQ. Nodes
keep track of the RREQ's source IP address and broadcast ID. If they receive a
RREQ that has already been processed, they discard the RREQ and do not
forward the packet.
As the RREP propagates back to the source, nodes create forward pointers to
the destination. Upon receiving the RREP, the source node will begin forwarding
data to the destination. If the source node later receives a RREP containing a
greater sequence number or the same sequence number with a smaller hop
count, it may update its routing information for that destination to use the better
route.
Routes are maintained as long as they remain active. A route is considered active
when data periodically travels from the source to the destination using the route.
When the source stops sending data packets, the route will time out and
eventually be deleted from the destination and intermediate node routing tables. If
a link breakage occurs while the route is active, the node upstream of the break
propagates a route error (RERR) message to the source node to inform it of the
now unreachable destination(s). After receiving the RERR, the source node can
reinitiate route discovery if the route is still required.
Figure 39 depicts an example of a simple network using AODV Routing. Subnets
1 and 2 are mobile subnets, while Subnet 3 is a fixed subnet on a wired network.
With AODV Routing enabled, all subnets are able to communicate with each
other. If Subnet 1 leaves the communications range of the Subnet 3, Subnet 1
automatically attempts to reach the fixed Subnet by routing packets through the
Subnet 2.