8 Jan
2018
8 Jan
'18
6:49 p.m.
Many, many thanks !
I've posted the full dialog unredacted here: https://pastebin.com/EE9iwgZf
The OK from Kamailio back to VOIP provider has
Record-Route: <sip:KAMAILIOIP;lr=on;ftag=SD2rbta01-8dd0e72b-0016-0379-
0000-0000;did=e0c.e0a1>
Contact: <sip:NUMBER@ASTERISKIP:5060>
So my understanding is that the ACK should be
ACK sip:NUMBER@ASTERISKIP:5060 SIP/2.0
....
and not
ACK sip:NUMBER@KAMAILIOIP:5060 SIP/2.0
Am I understanding correctly ?
Rgds
J
On Mon, Jan 8, 2018 at 11:28 AM, Sebastian Damm <damm(a)sipgate.de> wrote:
Hi,
On Mon, Jan 8, 2018 at 2:39 PM, Jean Cérien <cerien.jean(a)gmail.com> wrote:
Thanks for this answer. The voip provider is not really eager to alter
its SBC as it considers that the contact field is not mandatory in the ACK.
The RFC states (section 8.1.1.8)
The problem is not that the ACK doesn't carry a Contact header. The
problem is that the ACK is constructed incorrectly. This is what the RfC
says to UAC behavior (section 12.1.2):
The route set MUST be set to the list of URIs in the Record-Route header
field from the response, taken in reverse order and preserving all URI
parameters. If no Record-Route header field is present in the response, the
route set MUST be set to the empty set. This route set, even if empty,
overrides any pre-existing route set for future requests in this dialog. *The
remote target MUST be set to the URI from the Contact header field of the
response.*
This is what the carrier's SBC gets wrong. It doesn't address your
Asterisk but instead addresses your Kamailio, although the Contact of your
200 OK (hopefully) contains the Asterisk IP.
Please verify that your 200 OK going to the carrier actually does carry a
Contact header with the Asterisk IP, but if it does, section 12.1.2 of the
SIP RfC could help when arguing with the carrier.
Regards
Sebastian
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