[OLSR-users] Regular data broadcasting in ad hoc networks

[Andreas Tønnesen]

Hi lolo,

You subject is an interesting one.
A regular broadcast will not be routed in a ac-hoc network routed by
any of the MANET protocols. In such a network a broadcast will only
travel to the immediate neighbors(1-hop). But the issue of
broadcasting(and multicatsing) in theese kind of networks has been
discussed a lot, and a check with the MANET mailinglist could probably
be usefull as I can only speak for OLSR.
OLSR uses the MPR optimization for net-wide flooding and inheriting this
mechanism for normal IP broadcasts is probably a good idea. To do this
the best approach, IMO, is to have a local service intercepting IP
broadcast and encapsulate them in a OLSR message. All OLSR clients in
the network will have to understand theese encapsulated broadcast
packages for this to work 100%, but due to the default forwarding
algorithm in OLSR, such broadcast would be flooded even in a
non-hetreogenous environment.
Upon receiving a encapsualted broadcast, the OLSR client would have
to de-capsulate it message and pass it on to the IP layer in a
transparent manner(to avoid having to change kernel functionallity),
making sure that this traffic is not routed out from this node.
In addition to this, the message will be forwarded by the client
according to the default forwarding algorithm.

This is just stuff from the top of my head - but I've had discussions
on this with other people, and people seem to agree that this would
be a interesting approach.

I hope you found this helpful :)

- Andreas

lolo wrote:
> Hi all
> 
> This maybe has been answered many times and everywhere but i can't find 
> a short and final answer to that basic question :
> In an ad hoc network, with a routing protocol installed on every node, 
> all the nodes having a valid address in the same common subnetwork, 
> 192.168.1.0/24 for example, would a basic broadcast message will be 
> (re)transmitted to every member of the subnet as in a wired network 
> segment ? a crude command sample could be ping -b 192.168.1.0 or more 
> useful ones like iperf or netperf
> 
> I would accept long answers too... ;-)
> 
> Regards
> 
> Laurent
> 
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-- 
Andreas Tønnesen
http://www.olsr.org