[Kamailio-Users] switch to TCP when UDP message is bigger than MTU
Daniel-Constantin Mierla
miconda at gmail.com
Tue Apr 21 14:05:43 CEST 2009
Hello,
On 04/20/2009 08:34 PM, Klaus Darilion wrote:
> Hi Sandro!
>
> If you just need it for testing then you could use the approaches
> mentioned in the other emails.
>
> But for a production system you usually do not want this feature.
> Practically this paragraph from RFC 3261 is non-sense as it brakes
> communication with SIP clients.
>
> Residential customers SIP clients are mostly behind NAT and often do not
> even support TCP. Thus, automatic switching to TCP will cause problems
> as you can not reach the clients anymore.
>
> Usually administrators look how to turn this feature off instead of
> turning it on.
>
is it supposed to happen even if UA binds location with UDP contact? I
thought is used manly for inter-proxy/scb communication.
Cheers,
Daniel
> regards
> Klaus
>
> Sandro Bordacchini schrieb:
>
>> Hi all.
>>
>> I am doing some test about tcp/udp transport protocols in SIP and IP
>> fragmentation.
>>
>> I would like to test this behaviour, as stated in par. 18.1.1 of rfc3261:
>>
>> If a request is within 200 bytes of the path MTU, or if it is larger
>> than 1300 bytes and the path MTU is unknown, the request MUST be sent
>> using an RFC 2914 [43] congestion controlled transport protocol, such
>> as TCP. If this causes a change in the transport protocol from the
>> one indicated in the top Via, the value in the top Via MUST be
>> changed. This prevents fragmentation of messages over UDP and
>> provides congestion control for larger messages. However,
>> implementations MUST be able to handle messages up to the maximum
>> datagram packet size.
>>
>> To do this, I am running a OpenSer 1.3.2 with a "default" configuration
>> (and very simple: no accounting, no auth, no DB) and I have two SIP
>> phones registered on that server (for example, ext. 100 and ext. 101).
>>
>> When 100 calls 101, the INVITE reaches the OpenSer that appends some
>> "dummy" headers (I have added some append_hf in the route), just to let
>> the message be bigger than the MTU.
>> The INVITE is routed towards 101 with UDP protocol and I have IP
>> fragmentation.
>>
>> Do you have some hint to get the OpenSer work as described in the RFC
>> (i.e. switch automatically to TCP)?
>> Or is this only possible with UACs and not with proxies?
>>
>> TIA
>>
>>
>
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--
Daniel-Constantin Mierla
http://www.asipto.com/
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