[OpenSIPS-Users] Troubleshooting unabsorbed 200 OK retransmissions

[Bogdan-Andrei Iancu]

Hi Michael,

On 01/31/2013 09:30 PM, Michael Schloh von Bennewitz wrote:
> Hello Bogdan,
>
> On Tues., Jan. 30, 2013, Bogdan-Andrei Iancu wrote:
>> On 01/27/2013 06:28 PM, Michael Schloh wrote:
>>> An upstream PSTN gateway is retransmitting 200 OK just some hundreds
>>> milliseconds after the first 200 OK (following my outgoing INVITE.)
>>> My OpenSIPS 1.7.2 on Solaris 11 AMD64 is sending both 200 OK
>>> messages to the UAC which initiates the INVITE. The retransmitted
>>> 200 OK messages are identical.
>>>
>>> [...]
>>>
>>> How can I force OpenSIPS to absorb the 200 OK retransmissions?
>>>
>> The retransmissions for 200 OK are end-2-end, which means their are
>> transparent for the proxies - that's what the RFC says. The 200 OK  +
>> ACK exchange is end-2-end confirmation and proxies are not absorbing
>> any retransmissions here.
>>
> Okay that makes sense, so not only is OpenSIPS doing its job
> correctly but that I shouldn't try to adjust this behaviour in
> respect of RFC3261.
>
> What doesn't make sense is that the upstream gateway is waiting
> sometimes just 300 milliseconds to retransmit, when they know
> there will be SQL lookups, DNS lookups, and so on.
>
> The operator told me that the timer value 500 ms is standard
> practice for 200 OK, not sure if he's right about that or if
> there's any good reason for it.
Indeed 500ms is the first timer for retransmissions - but as you 
mentioned the retransmission for the 200 OK, why does it take so look to 
get the ACK back - is someone doing some heavy processing for the 200 OK 
or for ACK ?

Regards,
Bogdan