To prevent unnecessary network-wide dissemination of RREQs, the
originating node SHOULD use an expanding ring search technique. In
an expanding ring search, the originating node initially uses a TTL =
TTL_START in the RREQ packet IP header and sets the timeout for
receiving a RREP to RING_TRAVERSAL_TIME milliseconds.
RING_TRAVERSAL_TIME is calculated as described in section 10. The
TTL_VALUE used in calculating RING_TRAVERSAL_TIME is set equal to the
value of the TTL field in the IP header. If the RREQ times out
without a corresponding RREP, the originator broadcasts the RREQ
again with the TTL incremented by TTL_INCREMENT. This continues
until the TTL set in the RREQ reaches TTL_THRESHOLD, beyond which a
TTL = NET_DIAMETER is used for each attempt. Each time, the timeout
for receiving a RREP is RING_TRAVERSAL_TIME. When it is desired to
have all retries traverse the entire ad hoc network, this can be
achieved by configuring TTL_START and TTL_INCREMENT both to be the
same value as NET_DIAMETER.