[Olsr-users] Received message to big to be forwarded

Ferry Huberts (spam-protected)
Fri Apr 17 14:34:54 CEST 2015


We should be able to split packets with multiple messages into multiple 
packets as long as the messages themselves aren't to big.
And also the reverse: merge packets for larger MTUs.

IMHO olsrd should/can adapt to different MTU sizes.

This most probably not go into v1 unless someone has a nice patch set 
(well tested!). But I think it's a good idea for v2.

On 17/04/15 14:30, Henning Rogge wrote:
> The only other option I see is to set the MTU size for olsrd messages
> to 1280-40-8=1232 bytes... which should be guaranteed for all IPv6
> capable networks.
> Henning
> On Fri, Apr 17, 2015 at 2:25 PM, Ferry Huberts <(spam-protected)> wrote:
>> On 17/04/15 14:22, Henning Rogge wrote:
>>> On Fri, Apr 17, 2015 at 2:07 PM, Jernej Kos <(spam-protected)> wrote:
>>>> Hello!
>>>> We are seeing a lot of the following messages in our logs:
>>>> Received message to big to be forwarded on digger1226(1296 bytes)!
>>>> Received message to big to be forwarded on digger1346(1328 bytes)!
>>>> The message sizes indicate that the OLSR messages that are to be
>>>> forwarded are probably larger than the MTU (the OLSR daemon has multiple
>>>> interfaces with different MTU sizes). Does this warning indicate some
>>>> problems with propagating routing information as messages are dropped
>>>> instead of being forwarded?
>>> The problem is that olsrd cannot fragment messages (which are flooded
>>> through the whole mesh) hop-by-hop... which means a network with
>>> different MTU-sizes AND large neighborhoods (which produce huge
>>> messages) is a problem.
>> Yes, you should really setup a lower MTU on all your nodes
>>> Henning Rogge
>> --
>> Ferry Huberts

Ferry Huberts

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