[OpenSIPS-Users] SIP message relay order

[Bogdan-Andrei Iancu]

Hi Stas,

Such races may happen at application level or even at network level 
(when using UDP) - so if you have 2 packets very close as time, they may 
swap. That is SIP :)

The full guilt is in the UAC device, IMHO - it should let some time gap 
between the ACK and re-INVITE, to eliminate any possible races.

Now, what you can do is to use the dialog module and to check the dialog 
state when receiving the re-invite. If $DLG_status is /3/ (Confirmed by 
a final reply but no ACK received yet), drop with no reply the 
re-INVITEs (to force a later retransmission) :
http://www.opensips.org/html/docs/modules/2.2.x/dialog.html#id297400

Regards,

Bogdan-Andrei Iancu
OpenSIPS Founder and Developer
http://www.opensips-solutions.com

On 02/02/2017 10:31 PM, Stas Kobzar wrote:
> Hello List,
>
> My call flow has initial INVITE and re-INVITE to update RTP IP/port.
> Usually everything works well, but sometimes OpenSIPS come up with 
> following example:
>
> UA OpenSIPS          PSTN GW
> -------------------------------------------
> INV(CSeq: 100) -----> | ---> INV(CSeq: 100)
> <---- 200 OK  | <--- 200 OK
>
> (UA sends ACK then new INVITE)
>
> ACK(CSeq: 100) -----> |
> reINV(Cseq: 101) ---> |
>
> (OpenSIPS relays first INVITE then ACK)
>                       | ---> reINV(CSeq: 101)
>                       | --->   ACK(CSeq: 100)
>
> When PSTN gateway receives re-INVITE before ACK for previous INVITE
> it responds 500 with Retry-After header.
> This is correct behaviour which conforms to the RFC 3261 section 14.2
>
> My question is:
> Is it possible to assure order of received and relayed messages within 
> the same SIP session? Is there any configuration parameter?
>
> Thank you,
> -- 
>
> Stas Kobzar
>
> Developeur VoIP / VoIP Developer
>
>
> Modulis­.ca Inc.
>
> # Bureau / Office: 514-284-2020 x 246
>
> Email: s <http://firstname.lastname>tas.kobzar at modulis.ca
>
> https://www.modulis.com <https://www.modulis.com/>
>
>
>
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