A.4 CCNR 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 16TS

Figure A.4.1: CCNR call

Figure A.4.1 shows a basic signalling flow for a CCNR operation and a CCNR 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.4-1: 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=1800

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 CCNR recall to UE A by sending a REFER request, the "m" SIP URI parameter set to "NR" will be included in the Request-URI of the REFER request. UE-A confirms the REFER request.

Table A.4-2: REFER request (Originating AS to S-CSCF)

REFER sip:user1_public1@home1.net;m=NR 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 CCNR 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 "NR" to the Request-URI, and forwards the INVITE request to UE-B.

Table A.4-3: SIP INVITE request (Originating AS to S-CSCF)

INVITE sip:user2_public2@home2.net;m=NR 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

Call-Info:<sip:user1_public1@home1.net>;purpose=call-completion;m=BS

Content-Type: application/sdp

Content-Length: (…)