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

[Henning Rogge]

Yes,

they can and will be distributed over multiple messages... if they
don't fit into the local MTU.

Henning

On Fri, Apr 17, 2015 at 2:39 PM, Jernej Kos <(spam-protected)> wrote:
> Hello!
>
> So the reason for these big messages is probably the fact that there are
> nodes that have a lot of neighbours? Can these be split over multiple
> messages or not?
>
>
> Jernej
>
> On 17. 04. 2015 14:37, Henning Rogge wrote:
>> Hi,
>>
>> I think olsrd (1) already can split packets along the messages... the
>> problem happens when a message is too large even for a UDP packet of
>> its own.
>>
>> Henning
>>
>> On Fri, Apr 17, 2015 at 2:34 PM, Ferry Huberts <(spam-protected)> wrote:
>>> OTOH
>>>
>>> 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
>