A.6 CCNL call
24.6423GPPCompletion of Communications to Busy Subscriber (CCBS) and Completion of Communications by No Reply (CCNR) using IP Multimedia (IM) Core Network (CN) subsystemProtocol specificationRelease 18TS
Figure A.6.1: CCNL call
Figure A.6.1 shows a basic signalling flow for a CCNL call.
Call flows
1 to 4: The terminating AS sends a NOTIFY request to the originating AS, according to the procedures described in RFC 6910 [5]. The body contains a parameter informing of the caller’s call-completion state ‘ready’ (for recall). The originating AS confirms the notification.
Table A.6-1: NOTIFY request (Terminating AS to S-CSCF)
NOTIFY sip:oas.home1.net SIP/2.0
Via: SIP/2.0/UDP tas.home2.net;branch=z9hG4bK348923.1
Max-Forwards: 70
Route: <sip:scscf2.home2.net>
P-Asserted-Identity: <sip:tas.home2.net>
From: <sip:user2_public2@home2.net>;tag=151170
To: <sip:user1_public1@home1.net>;tag=31415
Call-ID: b89rjhnedlrfjflslj40a222
CSeq: 47 NOTIFY
Subscription-State: active ;expires=4630
Event: call-completion
Contact: <sip:tas.home2.net>
Content-Type: application/call-completion
Content-Length: (…)
cc-state: ready
cc-service retention
5 to 8: The originating AS initiates the CCNL recall to UE A by sending a REFER request, the "m" SIP URI parameter set to "NL" will be included in the Request-URI of the REFER request. UE-A confirms the REFER request.
Table A.6-2: REFER request (Originating AS to S-CSCF)
REFER sip:user1_public1@home1.net;m=NL SIP/2.0;
Via: SIP/2.0/UDP oas.home1.net;branch=z9hG4bK23273846
Max-Forwards: 70
Route: <sip:scscf1.home1.net;lr>
P-Asserted-Identity: <sip:oas.home1.net>
From: <sip:oas.home1.net>; tag=161828
To: <sip:user1_public1@home1.net>
Call-ID: cb03a0s09a2sdfglkj490333
Cseq: 127 REFER
Refer-To: <sip:user2_public2@home2.net;method=INVITE>
Referred-By: <sip:oas.home1.net>
Contact: <sip:oas.home1.net>
Content-Length: 0
9 to 10: UE-A starts the CCNL call by sending an INVITE request to UE-B.
11 to 13: In order to mark the INVITE request as a prioritized request for call-completion, the originating AS adds the "m" SIP URI parameter with the value "NL" to the Request-URI, and forwards the INVITE request to UE-B. The originating AS also adds a Call-Info header field with the URI of UE-A from the P-Asserted-Identity from the original communication, a "purpose" header field parameter set to "call-completion", and a m-parameter set to "NL".
Table A.4-3: SIP INVITE request (Originating AS to S-CSCF)
INVITE sip:user2_public2@home2.net;m=NL SIP/2.0;
Via: SIP/2.0/UDP [5555::aaa:bbb:ccc:ddd]:1357;comp=sigcomp;branch=z9hG4bKnashds7
Max-Forwards: 70
Route: sip:pcscf1.home1.net:7531;lr;comp=sigcomp>, <sip:orig@scscf1.home1.net;lr>
Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel"
Privacy: none
From: <sip:user1_public1@home1.net>; tag=171829
To: <sip:user2_public2@home2.net>
Call-ID: cb03a0s09a2sdfglkj490444
Cseq: 154 INVITE
Supported: 100rel; precondition, gruu, 199
Require: sec-agree
Contact: <sip:user1_public1@home1.net;gr=urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bg6>;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel"
Allow: INVITE, ACK, CANCEL, BYE, PRACK, UPDATE
Accept: application/sdp,application/3gpp-ims+xml
Content-Type: application/sdp
Content-Length: (…)
Annex B (informative):
Example of filter criteria