A.2 CCBS suspend and resume procedures

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.2.1: CCBS suspend and resume procedures

Figure A.2.1 shows a basic signalling flow for CCBS suspend and resume procedures.

Call flows

1 to 4: UE-A is busy and the CCBS recall fails. The originating AS initiates the suspension procedure. It generates a PUBLISH request according to the procedures described in RFC 6910 [5]. The Request-URI of the PUBLISH request includes the URI of the terminating AS. The From header field includes the URI of UE-Aand the To header field includes the URI of UE-B. The body of the PUBLISH request indicates the PIDF state ‘closed’.

Table A.2-1: PUBLISH request (Originating AS to S-CSCF)

PUBLISH sip:tas.home2.net;m=BS SIP/2.0

Via: SIP/2.0/UDP oas.home1.net;branch=z9hG4bKnashds7

Max-Forwards: 70

Route: <sip:scscf1.home1.net>

P-Asserted-Identity: <sip:user1_public1@home1.net>

From: <sip:user1_public1@home1.net>;tag=31415

To: <sip:user2_public2@home2.net>; tag=151170

Call-ID: b89rjhnedlrfjflslj40a222

CSeq: 71 PUBLISH

Event: presence

Expires: 1800

Content-Type: application/pidf+xml

Content-Length: (…)

<?xml version="1.0" encoding="UTF-8"?>

<presence xmlns="urn:ietf:params:xml:ns:pidf"

xmlns:rpid="urn:ietf:params:xml:ns:pidf:rpid"

xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"

xmlns:pcp="urn:ietf:params:xml:ns:pidf:caps"

xmlns:c="urn:ietf:params:xml:ns:pidf:cipid"

entity="pres:user2_public1@home2.net">

<tuple id="a8098a.672364762364">

<status>

<basic>closed</basic>

</status>

</tuple>

</presence>

5 to 8: The terminating AS suspends the queue entry and 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 ‘queued’. The originating AS starts busy state supervision procedures on UE-A.

Table A.2-2: 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: 72 NOTIFY

Subscription-State: active ;expires=1795

Event: call-completion

Contact: <sip:tas.home2.net>

Content-Type: application/call-completion

Content-Length: (…)

cc-state: queued

cc-service retention

9 to 12: UE-A becomes not busy. The originating AS initiates the resumption procedure. It generates a PUBLISH request according to the procedures described in RFC 6910 [5]. The Request-URI of the PUBLISH request includes the URI of the terminating AS. The From header field includes the URI of UE-A and the To header field includes the URI of UE-B. The body of the PUBLISH request indicates the PIDF state ‘open’.

Table A.2-3: PUBLISH request (Originating AS to S-CSCF)

PUBLISH sip:tas.home2.net;m=BS SIP/2.0

Via: SIP/2.0/UDP oas.home1.net;branch=z9hG4bKnashds7

Max-Forwards: 70

Route: <sip:scscf1.home1.net>

P-Asserted-Identity: <sip: user1_public1@home1.net>

From: <sip:user1_public1@home1.net>;tag=31416

To: <sip:user2_public2@home2.net>; tag=151170

Call-ID: b89rjhnedlrfjflslj40a222

CSeq: 85 PUBLISH

Event: presence

Expires: 1100

Content-Type: application/pidf+xml

Content-Length: (…)

<?xml version="1.0" encoding="UTF-8"?>

<presence xmlns="urn:ietf:params:xml:ns:pidf"

xmlns:rpid="urn:ietf:params:xml:ns:pidf:rpid"

xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"

xmlns:pcp="urn:ietf:params:xml:ns:pidf:caps"

xmlns:c="urn:ietf:params:xml:ns:pidf:cipid"

entity="pres:user2_public1@home2.net">

<tuple id="a8098a.672364762364">

<status>

<basic>open</basic>

</status>

</tuple>

</presence>

13 to 16: The terminating AS resumes the queue entry and 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 ‘queued’.

Table A.2-4: 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: 86 NOTIFY

Subscription-State: active ;expires=1095

Event: call-completion

Contact: <sip:tas.home2.net>

Content-Type: application/call-completion

Content-Length: (…)

cc-state: queued

cc-service retention