Re: [SR-Users] ACK Relay Issue Transaction Not Found

Alex Balashov Tue, 24 Nov 2020 09:31:19 -0800

Hiddenly? :-)

-- Alex


On 11/24/20 12:22 PM, [email protected] wrote:

Thanks for your reply.
I can't see the ACK being relayed to MSTeams in network capture throughin Relay Route
if(is_method("ACK|BYE")) {
sip_trace();
setflag(22);
}
but call has been established successfully. is ACK is being relayedhiddenly by Kamailio ?
On Tuesday, November 24, 2020, 09:35:32 PM GMT+5, Alex Balashov<[email protected]> wrote:
Hi,

If you take a look at the documentation for t_check_trans(), you'll see
that it behaves in very different ways depending on the type of message
it is handling, and is supposed to return a negative/false value in some
scenarios or abort script execution -- context is very important:
https://kamailio.org/docs/modules/stable/modules/tm.html#tm.f.t_check_trans<https://kamailio.org/docs/modules/stable/modules/tm.html#tm.f.t_check_trans>
There are two types of ACKs - hop-by-hop ACKs, which acknowledge
negative final replies, and end-to-end ACKs, which are for successful
final 2xx replies and meant to be relayed by Kamailio end-to-end, in the
manner of a normal in-dialog request.

An ACK of this nature is a separate request and a separate transaction,
though its CSeq is identical to that of the INVITE transaction it is
meant to acknowledge. However, a 2xx final reply will close an INVITE
transaction, subject to `max_inv_lifetime` and `wt_timer`[1] and all
that stuff:

The documentation speaks to this point:

     "For end-to-end ACKs (ACKs to 2xx responses for forwarded
     INVITE transactions) it will return true if the corresponding
     INVITE transaction is found and still active and false if not.

     Note that the e2e ACK matching is more of a hint then a
     certainty. A delayed e2e ACK might arrive after the
     transaction wait time elapses, when the INVITE transaction
     no longer exists and thus would not match anything. There
     are also cases when tm would not keep all the information
     needed for e2e ACK matching (since this is not needed for
     a stateful proxy and it requires additional memory,
     tm will not keep this information unless needed by
     some other module or callbacks)."

So, in other words, you should not expect t_check_trans() to return true
for an end-to-end ACK. It is reasonable to expect that in the vast
majority of cases, it will return false. The ACK should be relayed in
the same manner as any other loose-routed in-dialog request, e.g. a
reinvite or a BYE. If you follow the logic of the stock configuration
that Kamailio ships with, this will happen correctly by default.

-- Alex
[1]https://kamailio.org/docs/modules/stable/modules/tm.html#tm.p.wt_timer<https://kamailio.org/docs/modules/stable/modules/tm.html#tm.p.wt_timer>
On 11/24/20 3:24 AM, [email protected]<mailto:[email protected]> wrote:
 > Hi When ACK is received on Kamailio from PBX t_check_trans() fails.
 > 200 OK sent PBX from Teams and ACK from PBX is provided here.
 >
 > What could be the issue.
 >
 > SIP/2.0 200 OK
> FROM: "Ext1"<sip:1102@PBX_IP<mailto:1102@PBX_IP>>;tag=e08f0a03-1120-4e13-b0e2-90d1a027c05f> TO: <sip:1101@KAM_IP<mailto:1101@KAM_IP>>;tag=e667397cb47c457a860222931e320b41
 > CSEQ: 25772 INVITE
 > CALL-ID: a6685754-b402-4a15-82b2-5fb2551e5b58
 > VIA: SIP/2.0/UDP
>PBX_IP:7790;received=PBX_IP;branch=z9hG4bKPj170912fc-0908-40bb-8248-9f6cb560332d;rport=7790
 >
 > RECORD-ROUTE:
><sip:sip-du-a-us.pstnhub.microsoft.com:5061;transport=tls;lr>,<sip:sbc.callsprout.com;transport=tls;ftag=e08f0a03-1120-4e13-b0e2-90d1a027c05f;lr>,<sip:KAM_IP:7790;transport=udp;ftag=e08f0a03-1120-4e13-b0e2-90d1a027c05f;lr>
 >
 > CONTACT:
><sip:api-du-b-usea.pstnhub.microsoft.com:443;x-i=c825abba-7203-442c-8461-994522d14365;x-c=25f3c2ce3a635971b809dc3be872e51b/s/1/63c9eea743284db99366cabf5f7dcbf5;ias=52.114.132.46~5061~3>
 >
 > CONTENT-LENGTH: 353
 > SUPPORTED: timer
 > CONTENT-TYPE: application/sdp
 > ALLOW: INVITE,ACK,OPTIONS,CANCEL,BYE,NOTIFY
 > REQUIRE: timer
 > SESSION-EXPIRES: 1800;refresher=uac
 > SERVER: Microsoft.PSTNHub.SIPProxy v.2020.11.16.5 i.USEA.5
 > X-Siptrace-Fromip: tls:KAM_IP:7790
 > X-Siptrace-Toip: udp:PBX_IP:7790
 > X-Siptrace-Time: 1606205334 607029
 > X-Siptrace-Method: INVITE
 > X-Siptrace-Dir: out
 >
 > ACK
>sip:api-du-b-usea.pstnhub.microsoft.com:443;x-i=c825abba-7203-442c-8461-994522d14365;x-c=25f3c2ce3a635971b809dc3be872e51b/s/1/63c9eea743284db99366cabf5f7dcbf5;alias=.114.132.46~5061~3
 > SIP/2.0
 > Via: SIP/2.0/UDP
 > PBX_IP:7790;rport;branch=z9hG4bKPjaa30c14c-c965-473d-bc49-9f223f9f634c
> From: "Ext1" <sip:1102@PBX_IP<mailto:1102@PBX_IP>>;tag=e08f0a03-1120-4e13-b0e2-90d1a027c05f> To: <sip:1101@KAM_IP<mailto:1101@KAM_IP>>;tag=e667397cb47c457a860222931e320b41
 > Call-ID: a6685754-b402-4a15-82b2-5fb2551e5b58
 > CSeq: 25772 ACK
 > Route: <sip:KAM_IP:7790;lr;ftag=e08f0a03-1120-4e13-b0e2-90d1a027c05f>
 > Route:
><sip:sbc.callsprout.com;transport=tls;lr;ftag=e08f0a03-1120-4e13-b0e2-90d1a027c05f>
 >
 > Route: <sip:sip-du-a-us.pstnhub.microsoft.com:5061;transport=tls;lr>
 > Max-Forwards: 70
 > User-Agent: Asterisk
 > Content-Length:  0
 > X-Siptrace-Fromip: udp:PBX_IP:7790
 > X-Siptrace-Toip: udp:KAM_IP:7790
 > X-Siptrace-Time: 1606205334 615495
 > X-Siptrace-Method: ACK
 > X-Siptrace-Dir: in

 >
 > _______________________________________________
 > Kamailio (SER) - Users Mailing List
 > [email protected] <mailto:[email protected]>
> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users<https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users>
 >

--
Alex Balashov | Principal | Evariste Systems LLC

Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, <http://www.evaristesys.com/,>http://www.csrpswitch.com/ <http://www.csrpswitch.com/>
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--
Alex Balashov | Principal | Evariste Systems LLC

Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/

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Re: [SR-Users] ACK Relay Issue Transaction Not Found

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