3 Definitions and abbreviations

24.2373GPPIP Multimedia (IM) Core Network (CN) subsystem IP Multimedia Subsystem (IMS) service continuityRelease 17Stage 3TS

3.1 Definitions

For the purposes of the present document, the terms and definitions given in 3GPP TR 21.905 [1] and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in 3GPP TR 21.905 [1].

Alerting phase: Refers to a SIP session for which all possibly existing dialogs created by the SIP INVITE request initiating the session are early dialogs, for which no final SIP response has been received yet and for which SIP 180 (Ringing) response has already been received in an existing early dialogs.

Pre-alerting phase: Refers to a SIP session for which all possibly existing dialogs created by the SIP INVITE request initiating the session are early dialogs, for which no final SIP response has been received yet and for which SIP 180 (Ringing) response has not been received or sent yet in any existing early dialogs.

Dual radio access transfer for calls in alerting phase: feature enabling dual radio access transfer of a session with speech media component where the session is in an alerting phase.

Dual radio access transfer for originating calls in pre-alerting phase: feature enabling dual radio access transfer of a session with speech media component where the session was originated by the SC UE and the session is in a pre-alerting phase.

Dynamic STI: An STI dynamically assigned by the SCC AS, representing the SIP dialog identifier (Call-ID header field and the values of tags in To and From header fields) and used for session transfer request when Gm service control is available.

Dynamic STN: An STN encoded as an E.164 number in tel URI format dynamically assigned by the SCC AS replacing the static STN during PS to CS dual radio access transfer.

Static STN: An STN configured in the SC UE as an E.164 number. The static STN is used for PS to CS transfer when dynamic STN cannot be used.

Additional transferred session SCC AS URI: A SIP URI which is a public service identity hosted by SCC AS and which is used during PS-CS access transfer with the MSC Server assisted mid-call feature.

Static STI: An STI configured in the SC UE either as a SIP URI or as an E.164 number in tel URI format or SIP URI representation of tel URI. The static STI is used for CS-PS transfer when dynamic STI is unavailable.

PS to PS STI: An STI configured in SC UE either as a SIP URI or as an E.164 number in tel URI format or SIP URI representation of tel URI. The PS to PS STI is used for PS to PS access transfer.

PS to CS STN: An STN that is encoded as an E.164 number. The PS to CS STN is used for PS to CS access transfer.

Speech media component: SDP media component of audio media type with codec suitable for conversational speech. Connection (c=) and attribute (a=) informations at the SDP session level not overridden by information at the SDP media level in the speech media component are considered to be part of the speech media component.

Active speech media component: speech media component which has "recvonly" or "sendrecv" directionality at the SC UE or at the MSC server serving the SC UE.

Inactive speech media component: speech media component which has "sendonly" or "inactive" directionality at the SC UE or at the MSC server serving the SC UE.

Active video media component: video media component which has "recvonly" or "sendrecv" directionality at the SC UE or at the MSC server serving the SC UE.

Inactive video media component: video media component which has "sendonly" or "inactive" directionality at the SC UE or at the MSC server serving the SC UE.

ATCF URI for originating requests: A URI of the ATCF where the ATCF receives requests sent by the served UEs.

ATCF URI for terminating requests: A URI of the ATCF where the ATCF receives requests targeted to the served UEs.

ATCF management URI: A URI hosted by the ATCF where the ATCF performing the role of a UAS receives SIP requests for ATCF management (e.g. SIP MESSAGE requests containing the PS to CS SRVCC related information). The ATCF management URI is routable via the I-CSCF in the network where the ATCF is located using the same routing mechanism as used for Public Service Identities hosted by an AS.

Registration Path: The set of Path header field values and the set of Service-Route header field values created by successful completion of the SIP REGISTER transaction.

SRVCC-related information: Information required by the ATCF to perform PS to CS SRVCC transfer or CS to PS SRVCC transfer or both. It is provided in the MIME body as defined in clause D.3.

UE information for CS to PS SRVCC: Session description containing speech media component that will be used by the ATGW to send media to the SC UE during the CS to PS SRVCC access transfer.

ATGW information for CS to PS SRVCC: Session description containing speech media component that will be used by the SC UE to send media to the ATGW during the CS to PS SRVCC access transfer.

PS to CS SRVCC for calls in alerting phase: feature enabling PS to CS SRVCC of a session with speech media component where the session is in alerting phase.

CS to PS SRVCC for calls in alerting phase: feature enabling CS to PS SRVCC of a session with speech media component where the session is in alerting phase.

PS to CS SRVCC for originating calls in pre-alerting phase: feature enabling PS to CS SRVCC of a session with speech media component where the session was originated by the SC UE and the session is in pre-alerting phase.

PS to CS SRVCC for terminating calls in pre-alerting phase: feature enabling PS to CS SRVCC of a session with speech media component where the session was terminated by the SC UE and the session is in pre-alerting phase.

CS session in an early phase: A CS call for which the CS call setup procedure is not complete, i.e. the CC CONNECT message is not sent or received as described in 3GPP TS 24.008 [8] yet but where either a CC CALL PROCEEDING message as described in 3GPP TS 24.008 [8] has been received or a CC ALERTING message as described in 3GPP TS 24.008 [8] has been sent or received.

Precondition enabled dialog: a dialog (either a confirmed dialog or an early dialog) created by a SIP response containing a Require header field with the precondition option tag.

Precondition enabled initial INVITE request: an initial INVITE request containing a Require header field with the precondition option tag or a Supported header field with the precondition option tag.

RTP payload format: the <encoding name> portion of an "a=rtpmap" attribute according to IETF RFC 4566 [93] for the dynamically assigned RTP payload type numbers or the name of encoding reserved in IETF RFC 3551 [91] table 1 for statically assigned RTP payload type numbers.

RTP payload type number: a number identifying an RTP payload type of a media stream using the RTP based transport protocol. In SDP, the RTP payload type number can be found in a sub-field of an <fmt> portion of an "m=" line, in a <payload type> portion of the "a=rtpmap" attribute and in a <format> portion of an "a=fmtp" attribute, according to IETF RFC 4566 [93]. In RTP, the RTP payload type number is found in the PT field of the RTP header according to IETF RFC 3550 [92].

RTP payload type: an RTP payload type number indicated in a sub-field of an <fmt> portion of an "m=" line and, if included, an "a=rtpmap" attribute and an "a=fmtp" attribute for the RTP payload type number, included in an SDP body, according to IETF RFC 4566 [93].

For the purposes of the present document, the following terms and definitions given in 3GPP TS 23.237 [9] apply:

Access Leg

Access Transfer Control Function (ATCF)

Access Transfer Gateway (ATGW)

Access Transfer Update – Session Transfer Identifier (ATU-STI)

Dual radio

Emergency Session Transfer Number for SR VCC (E-STN-SR)

Home Leg

Local Operating Environment

Remote Leg

Serving Leg Session Transfer Identifier for reverse SRVCC (STI-rSR)

Source Access Leg

Target Access Leg

Emergency Session Transfer Number for DRVCC (E-STN-DRVCC)

For the purposes of the present document, the following terms and definitions given in 3GPP TS 24.292 [4] apply:

CS call

CS media

For the purposes of the present document, the following terms and definitions given in 3GPP TS 23.218 [67] apply:

Initial filter criteria

For the purposes of the present document, the following terms and definitions given in 3GPP TS 23.228 [15] apply:

Policy and Charging Rule Function (PCRF)

For the purposes of the present document, the following terms and definitions given in 3GPP TS 23.003 [12] apply:

Correlation MSISDN

IP Multimedia Routeing Number (IMRN)

Session Transfer Identifier (STI)

Session Transfer Number (STN)

Session Transfer Number for SR-VCC (STN-SR)

For the purposes of the present document, the following terms and definitions given in IETF RFC 5012 [16] apply:

Emergency service URN

For the purposes of the present document, the following terms and definitions given in IETF RFC 4353 [55] apply:

Conference

Conference URI

Focus

Participant

For the purposes of the present document, the following terms and definitions given in IETF RFC 3264 [58] apply:

Directionality

For the purposes of the present document, the following terms and definitions given in 3GPP TS 23.292 [63] apply:

ICS user

For the purposes of the present document, the following terms and definitions given 3GPP TS 24.229 [2] apply:

Authorised Resource-Priority header field

Temporarily Authorised Resource-Priority header field

NOTE: Within the present specification, a Temporarily Authorised Resource-Priority header field can be applied to handling of originating requests in the ATCF.

For the purposes of the present document, the following terms and definitions given in 3GPP TS 24.301 [52] apply:

Evolved Packet System (EPS)

Persistent EPS bearer context

For the purposes of the present document, the following terms and definitions given in 3GPP TS 23.501 [96] apply:

5G System (5GS)

NG-RAN

Non-3GPP InterWorking Function (N3IWF)

Protocol Data Unit (PDU) session

For the purposes of the present document, the following terms and definitions given in 3GPP TS 24.501 [98] apply:

Persistent PDU session context

For the purposes of the present document, the following terms and definitions given 3GPP TS 29.274 [70] apply:

Allocation/Retention Priority (ARP)

For the purposes of the present document, the following terms and definitions given 3GPP TS 23.216 [49] apply:

5G SRVCC

3.2 Abbreviations

For the purposes of the present document, the abbreviations given in 3GPP TR 21.905 [1] and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in 3GPP TR 21.905 [1].

1xx A SIP status-code in the range 101 through 199

18x A SIP status-code in the range 180 through 189

2xx A SIP status-code in the range 200 through 299

EATF Emergency Access Transfer Function

E-STN-SR Emergency Call Session Transfer Number – Single Radio

E-SR-VCC Emergency Single Radio Voice Call Continuity

C-MSISDN Correlation MSISDN

IMRN IP Multimedia Routing Number

SC Service Continuity

SCC Service Centralization and Continuity

SM Session Management

SRVCC Single Radio Voice Call Continuity

STI Session Transfer Identifier

STI-rSR Session Transfer Identifier for reverse SRVCC

STN Session Transfer Number

STN-SR Session Transfer Number – Single Radio

vSRVCC Single Radio Video Call Continuity