[Olsr-dev] local broadcast/custom message types

Lotte Steenbrink (spam-protected)
Fri Feb 22 10:52:52 CET 2013

Hi Henning and Bastian,

Am 21.02.2013 um 08:53 schrieb Henning Rogge:

> On 02/21/2013 08:49 AM, Lotte Steenbrink wrote:
>> As far as I/we understood it, the TTL that olsr routers (so in our
>> case the nexus 7s) will decrement is the one in the olsr-header. If
>> they get a packet that does not have this header, they will forward
>> it to whatever hop they consider appropriate, flooding the subnet
>> that forms our MANET with these broadcasts (and only the gateway node
>> would actually decrement the IP TTL). So based on this assumption we
>> figured it would be a better idea to make use of the already
>> implemented header creation rather than build these packets from
>> scratch... Is this assumption correct?
> Similar, but not completely correct.
> Have a look at the OLSR RFC:
> http://tools.ietf.org/html/rfc3626#section-3.3
> As you can see, every OLSR message (within the packet container) has a number of mandatory fields. You cannot have OLSR messages without them.
> One of the fields is the TTL, the other one is the hopcount.
> If you set the TTL of an OLSR message to 1 and the hopcount to 0, it will not be forwarded by the receivers (the same is done to the HELLO message).

You were completely right from the beginning, I was suffering from a severe case of “it can't possibly be _that_ easy”. Thanks for your patience and the explanations, I'm sorry for causing a fuss!


> Henning Rogge
> -- 
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