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

[Jernej Kos]

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

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