A.5.4 Signalling flows for termination to an ICS UE with CS media using Gm reference point when using an MSC Server not enhanced for ICS
24.2923GPPIP Multimedia (IM) Core Network (CN) subsystem Centralized Services (ICS)Release 17Stage 3TS
Figure A.5.4-1 shows the termination of a call to an ICS UE using CS bearers controlled through the IM CN subsystem. In this example the MSC Server is not enhanced for ICS thus translation at the MGCF of ISUP message to SIP messages is required.
Figure A.5.4-1: ICS UE termination with CS media using Gm reference point when using an MSC Server not enhanced for ICS
The details of the signalling flows are as follows:
1-12. These steps are identical to steps 1-12 described in subclause A.5.3 (Signalling flows for termination to an ICS UE with CS media using Gm reference point when using an MSC Server enhanced for ICS)
13. ISUP IAM message (MSC Server not enhanced for ICS to MGCF)
The MSC Server not enhanced for ICS maps the received SETUP message to an ISUP IAM message that is routed towards the MGCF.
Specifically for this signalling flow, the IAM includes:
– Called Party Number parameter = [Numbering plan identifier = ISDN/telephony numbering plan], (type of number = international number), (Number digits = 12125556666)]. The Called Party Number is set to the SCC AS PSI DN, as received in the SETUP message.
– Calling Party Number parameter = [(Numbering plan identifier = ISDN/telephony numbering plan), (type of number = international number), (Number digits = 12125552222)]
14. SIP INVITE request (MGCF to intermediate IM CN subsystem entities) – see example in Table A.5.4-14.
The MGCF maps the received ISUP IAM message to a SIP INVITE request which is routed towards the intermediate IM CN subsystem entities. The INVITE request is addressed to the SCC AS PSI DN in the Request-URI.
Table A.5.4-14: SIP INVITE request (MGCF to intermediate IM CN subsystem entities)
INVITE tel:+1-212-555-6666 SIP/2.0
Via: SIP/2.0/UDP mgcf1.home1.net;branch=z9hG4bKnashds7
Max-Forwards: 70
Route: <sip:icscf1.home1.net;lr>
P-Asserted-Identity: <tel: +1-212-555-2222>
P-Charging-Vector: icid-value="AyretyU0dm+6O2IrT5tAFrbHLso=023551024"; orig-ioi=home2.net
Privacy: none
From: <tel: +1-212-555-2222>;tag=171828
To: <tel:+1-212-555-6666>
Call-ID: f81d4fae-7dec-11d0-a765-00a0c91e6bf6
Accept-Contact: *;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel"
Cseq: 127 INVITE
Supported: 100rel, precondition
Contact:<sip:mgcf1.home1.net>;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel"
Allow: INVITE, ACK, CANCEL, BYE, PRACK, UPDATE, REFER
Content-Type: application/sdp
Content-Length: (…)
v=0
o=- 2987933615 2987933615 IN IP6 5555::aaa:bbb:ccc:eee
s=
c=IN IP6 5555::aaa:bbb:ccc:eee
t=0 0
m=audio 3456 RTP/AVP 97 96
b=AS:25.4
a=curr:qos local sendrecv
a=curr:qos remote none
a=des:qos mandatory local sendrecv
a=des:qos none remote sendrecv
a=rtpmap:97 AMR
a=fmtp:97 mode-set=0,2,5,7; mode-change-period=2
a=rtpmap:96 telephone-event
a=maxptime:20
Request-URI: SCC AS PSI DN as received in the SETUP message.
P-Asserted-Identity: The MGCF inserts the tel-URI containing the subscriber number, as received from the ICS UE B.
SDP: The SDP contains preconfigured set of codecs supported by the MGW.
15. SIP 100 (Trying) response (intermediate IM CN subsystem entities to MSC Server not enhanced for ICS)
The intermediate IM CN subsystem entities respond to the MSC Server not enhanced for ICS with a SIP 100 (Trying) response. There is no ICS specific content in this response.
16. SIP INVITE request (intermediate IM CN subsystem entities to SCC AS) – see example in Table A.5.4-16
The SIP INVITE request is sent to the SCC AS.
Table A.5.4-16: SIP INVITE request (intermediate IM CN subsystem entities to SCC AS)
INVITE tel:+1-212-555-6666 SIP/2.0
Via: SIP/2.0/UDP scscf2.home2.net;branch=z9hG4bK332b33.1,SIP/2.0/UDP icscf1.home1.net;branch=z9hG4bK871y12.1, SIP/2.0/UDP mgcf1.home1.net;branch=z9hG4bKnashds7
Max-Forwards: 68
Route: <sip:sccas.home1.net;lr>, <sip:scscf1.home1.net;lr>;orig-dialog-id="yuflsae80r3rb3fh31ondyr829cnyr381cn932YDWref0w0-wwtg374"
Record-Route: <sip:scscf1.home1.net;lr>
P-Asserted-Identity:
P-Charging-Vector:
Privacy:
From:
To:
Accept-Contact:
Call-ID:
Cseq:
Supported:
Contact:
Allow:
Content-Type:
Content-Length: (…)
v=
o=-
s=
c=
t=
m=
b=
a=
a=
a=
a=
a=
a=
a=
a=
17. SIP 100 (Trying) response (SCC AS to intermediate IM CN subsystem entities)
The SCC AS responds to the intermediate IM CN subsystem entities with a SIP 100 (Trying) response. There is no ICS specific content in this response.
18. SIP 200 (OK) response (SCC AS to intermediate IM CN subsystem entities) – see example in Table A.5.4-18
The SCC AS responds to the SIP INVITE request with a SIP 200 (OK) response that includes an SDP answer.
Table A.5.4-18: SIP 200 (OK) response (SCC AS to intermediate IM CN subsystem entities)
SIP/2.0 200 OK
Via: SIP/2.0/UDP scscf2.home2.net;branch=z9hG4bK332b33.1,SIP/2.0/UDP icscf2.home2.net;branch=z9hG4bK871y12.1, SIP/2.0/UDP mgcf2.home2.net;branch=z9hG4bKnashds7
Record-Route: <sip:sccas.home1.net;lr>,<sip:scscf2.home2.net;lr>
P-Access-Network-Info:
Privacy: none
From: <tel: +1-212-555-2222>;tag=171828
To: <tel:+1-212-555-6666>;tag=1667452
Call-ID: f81d4fae-7dec-11d0-a765-00a0c91e6bf6
CSeq:
Require: 100rel, precondition
Contact: <sip:user1_public1@home2.net;gr=urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6>;+g.3gpp.icsi-ref="urn%3Aurn-7%3gpp-service.ims.icsi.mmtel">
Allow: INVITE, ACK, CANCEL, BYE, PRACK, UPDATE, REFER, MESSAGE
Content-Type: application/sdp
Content-Length: (…)
v=0
o=- 2987933623 2987933623 IN IP6 5555::ggg:fff:aaa:bbb
s=-
c=IN IP6 5555::ggg:fff:aaa:bbb
t=0 0
m=audio 3456 RTP/AVP 97 96
b=AS:25.4
a=curr:qos local sendrcv
a=curr:qos remote sendrcv
a=des:qos mandatory local sendrecv
a=des:qos mandatory remote sendrecv
a=rtpmap:97 AMR
a=fmtp:97 mode-set=0,2,5,7; mode-change-period=2
a=maxptime:20
19. SIP 200 (OK) response (intermediate IM CN subsystem to MGCF)
The intermediate IM CN subsystem entities route the SIP 200 (OK) response to the MSC Server not enhanced for ICS.
20. ISUP ANM message (MGCF to MSC Server not enhanced for ICS)
On receipt of the SIP 200 (OK) response, the MGCF generates an ISUP ANM message and sends this to the MSC Server not enhanced for ICS.
There is no ICS specific content in this message.
21-22. These steps are identical to steps 19-20 described in subclause A.5.3.
23-24. SIP ACK request (MGCF to SCC AS via intermediate IM CN subsystem entities)
On receipt of the SIP 200 (OK) response, the MGCF sends a SIP ACK request which is routed to the SCC AS via the intermediate IM CN subsystem entities. There is no ICS specific content in this response.
25-36. These steps are identical to steps 23-34 described in subclause A.5.3.