ETSI TS 124 237 V15.6.0 (2019-10)

TECHNICAL SPECIFICATION
Universal Mobile Telecommunications System (UMTS);
LTE;
IP Multimedia (IM) Core Network (CN)
subsystem IP Multimedia Subsystem (IMS) service continuity;
Stage 3
(3GPP TS 24.237 version 15.6.0 Release 15)


3GPP TS 24.237 version 15.6.0 Release 15 1 ETSI TS 124 237 V15.6.0 (2019-10)

Reference
RTS/TSGC-0124237vf60
Keywords
LTE,UMTS
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ETSI
3GPP TS 24.237 version 15.6.0 Release 15 2 ETSI TS 124 237 V15.6.0 (2019-10)
Intellectual Property Rights
Essential patents
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pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
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Legal Notice
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities. These shall be
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The cross reference between 3GPP and ETSI identities can be found under http://webapp.etsi.org/key/queryform.asp.
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
3GPP TS 24.237 version 15.6.0 Release 15 3 ETSI TS 124 237 V15.6.0 (2019-10)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 15
1 Scope . 16
2 References . 16
3 Definitions and abbreviations . 20
3.1 Definitions . 20
3.2 Abbreviations . 23
4 Overview of IP Multimedia (IM) Core Network (CN) subsystem Service Continuity . 24
4.1 General . 24
4.2 Underlying network capabilities . 25
4.2.1 General . 25
4.2.2 PS-CS session continuity, Single Radio . 25
4.2.3 PS to CS and CS to PS session continuity, dual radio access transfer . 26
4.3 URI and address assignments . 26
4.4 Support of session continuity in enterprise scenarios . 27
4.5 Guidelines for use of media feature tags or feature capability indicators . 27
5 Functional entities . 27
5.1 Introduction . 27
5.2 User Equipment (UE) . 27
5.3 Application Server (AS) . 28
5.4 MSC server . 28
5.5 EATF . 29
5.6 Access Transfer Control Function (ATCF) . 30
5.7 Access Transfer Gateway (ATGW) . 30
6 Roles for registration in the IM CN subsystem for service continuity . 31
6.1 Introduction . 31
6.2 SC UE . 31
6.2.1 Distinction of requests . 31
6.2.2 General . 31
6.2.3 SC UE receiving the ATGW information for CS to PS SRVCC . 31
6.3 SCC AS . 32
6.3.1 General . 32
6.3.2 Triggers for the SCC AS providing information to ATCF . 32
6.3.3 SCC AS providing the PS to CS SRVCC related information to the ATCF . 33
6.3.4 Triggers for the SCC AS providing information to MSC server . 34
6.3.5 SCC AS providing the CS to PS SRVCC information to the MSC server . 35
6.4 MSC server . 35
6.4.1 Distinction of requests . 35
6.4.2 General . 35
6.4.3 MSC server receiving the MSC information for CS to PS SRVCC . 35
6.5 Access Transfer Control Function (ATCF) . 36
6.5.1 Distinction of requests . 36
6.5.2 Registration related procedures in the ATCF . 36
6.5.3 ATCF receiving the SRVCC-related information . 38
6.5.4 ATCF sending the ATGW information for CS to PS SRVCC . 39
6.5.5 ATCF receiving the UE information for CS to PS SRVCC . 39
6A Roles for General Capabilities . 39
6A.1 Introduction . 39
6A.2 UE roles . 40
6A.2.1 Operator policy enforcement . 40
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6A.2.2 Signalling elements . 40
6A.2.2.1 Common SIP message set up procedures . 40
6A.2.2.2 SIP INVITE request . 40
6A.3 ATCF . 41
6A.3.1 SRVCC information bound to the registration path . 41
6A.4 SCC AS . 42
6A.4.1 Common SIP message set up procedures . 42
6A.4.2 SIP INVITE request . 42
6A.4.3 SIP INVITE responses towards the SC UE . 42
6A.4.3A SIP INVITE responses towards the MSC server . 44
6A.4.4 Handling of OMR specific attributes . 45
6A.4.5 Target refresh request for a dialog and associated responses . 45
6A.4.6 Rejecting malicious SIP REFER requests from remote UE . 46
6A.4.7 Protecting from malicious SIP INFO requests with remote leg information from remote UE . 46
6A.4.8 Precondition and access transfer . 46
6A.5 SDP media description conflict between target and remote access leg . 47
6A.6 Indicating traffic leg . 47
6A.6.1 The SCC AS server procedure for indicating traffic leg . 47
6A.6.2 The MSC server procedure for indicating traffic leg . 47
6A.6.3 The ATCF server procedure for indicating traffic leg . 47
6A.7 MSC server . 48
6A.7.1 Precondition and access transfer . 48
7 Roles for call origination for service continuity . 48
7.1 Introduction . 48
7.2 SC UE . 48
7.2.1 General . 48
7.2.2 Additional procedures with MSC server assisted mid-call feature . 49
7.3 SCC AS . 49
7.3.1 Distinction of requests sent to the SCC AS . 49
7.3.2 Call origination procedures at the SCC AS . 49
7.3.3 Subscription related procedures in the SCC AS . 50
7.4 EATF . 50
7.4.1 Distinction of requests sent to the EATF . 50
7.4.2 Call origination procedures at the EATF . 51
7.5 Access Transfer Control Function (ATCF) . 52
7.5.1 Distinction of requests . 52
7.5.2 Call origination procedures in the ATCF . 52
7.5.2.1 General . 52
7.5.2.2 Sessions originated in PS domain . 52
7.5.2.3 Sessions originated in CS domain . 53
7.5.3 Procedures in the ATCF for originating requests not related to a call . 55
7.6 MSC server . 55
7.6.1 Call origination procedures . 55
8 Roles for call termination for service continuity . 56
8.1 Introduction . 56
8.2 SC UE . 56
8.3 SCC AS . 57
8.3.1 Distinction of requests sent to the SCC AS . 57
8.3.2 Call termination procedures in the SCC AS . 57
8.4 Access Transfer Control Function (ATCF) . 59
8.4.1 Distinction of requests . 59
8.4.2 Call termination procedures in the ATCF . 59
8.4.2.1 General . 59
8.4.2.2 Sessions terminated in PS domain . 59
8.4.2.3 Sessions terminated in CS domain . 60
8.5 MSC server . 62
8.5.1 Distinction of requests . 62
8.5.2 Call termination procedures . 62
8.5.2.1 SIP INVITE request from home network . 62
8.5.2.2 SIP INVITE request from ATCF . 62
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9 Roles for PS-CS access transfer . 63
9.1 Introduction . 63
9.1A Additional procedures with MSC Server assisted mid-call feature . 63
9.2 SC UE . 64
9.2.0 General . 64
9.2.1 SC UE not using ICS procedures for PS to CS access transfer . 64
9.2.1AAA SC UE not using ICS procedures for PS to CS access transfer of emergency session . 66
9.2.1AA SC UE using ICS procedures for PS to CS access transfer . 66
9.2.1A SC UE procedures for PS to CS access transfer with MSC server assisted mid-call feature . 67
9.2.1B SC UE procedures for PS to CS access transfer with MSC server assisted mid-call feature for speech
and video session . 70
9.2.2 SC UE procedures for CS to PS access transfer . 71
9.2.2.1 Distinction of request . 71
9.2.2.2 SC UE procedure for transferring the first CS call . 71
9.2.3 SC UE procedures for CS to PS access transfer with MSC server assisted mid-call feature . 72
9.2.4 SC UE procedures for selecting a session in an early dialog phase to be transferred using PS to CS
dual radio access transfer procedure . 73
9.2.5 SC UE procedures for CS to PS dual radio access transfer of calls in an early phase . 74
9.2.5.1 Conditions for CS to PS dual radio access transfer of calls in originating pre-alerting or in the
alerting phase . 74
9.2.5.2 SC UE procedure for CS to PS dual radio access transfer of calls in originating pre-alerting or in
the alerting phase . 75
9.2.5.3 SC UE procedures for transferring an additional CS session in an early phase . 76
9.3 SCC AS . 77
9.3.0 General . 77
9.3.1 Distinction of requests sent to the SCC AS . 77
9.3.2 SCC AS procedures for PS to CS access transfer . 77
9.3.2A SCC AS procedures for PS to CS access transfer with MSC server assisted mid-call feature . 81
9.3.3 SCC AS procedures for CS to PS access transfer . 85
9.3.4 SCC AS procedures for CS to PS access transfer with MSC server assisted mid-call feature . 86
9.3.5 SCC AS procedures for PS to CS dual radio access transfer of calls in an early dialog phase . 88
9.3.5.1 Conditions for selecting a sessions in an early dialog phase . 88
9.3.5.2 SCC AS procedures for PS to CS dual radio access transfer of a originating session in the
alerting phase . 89
9.3.5.3 SCC AS procedures for PS to CS dual radio, access transfer of a originating session in the pre-
alerting phase . 91
9.3.5.4 SCC AS procedures for PS to CS dual radio access transfer of an additional session in an early
dialog phase. 93
9.3.5.5 SCC AS procedures for PS to CS dual radio access transfer of a terminating session in the
alerting phase . 94
9.3.6 Removal of non-transferred audio media components and release of source access legs. 95
9.3.7 SCC AS procedures for CS to PS dual radio access transfer for calls in an early phase . 96
9.3.7.1 Conditions for transferring dialog(s) in the originating pre-alerting or the alerting dialog phase . 96
9.3.7.2 SCC AS procedures for CS to PS dual radio access transfer for originating calls in pre-alerting
phase or in alerting phase on the originating side . 96
9.3.7.3 SCC AS procedures for CS to PS dual radio access transfer for a call in the alerting phase on the
terminating side . 98
9.3.7.4 SCC AS procedures for PS to CS dual radio access transfer of an additional session in an early
dialog phase. 99
9.4 MSC server enhanced for ICS . 102
9.4.1 Void . 102
9.4.1A Void . 102
9.5 PS to CS session continuity with MSC server assisted mid-call feature . 102
9.6 PS to CS session continuity with MSC server assisted mid-call feature for speech and video session . 105
9.7 MSC procedures for PS to CS dual radio access transfer of calls in an early phase . 105
9.8 MSC server enhanced for dual radio access transfer using a SIP interface . 107
9.8.1 General . 107
9.9 EATF . 108
9.9.1 EATF procedures for PS to CS session continuity, dual radio session transfer of emergency session . 108
10 Roles for PS-PS access transfer . 108
10.1 Introduction . 108
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10.2 SC UE . 108
10.2.0 General . 108
10.2.1 Full session transfer . 109
10.2.1A Void . 113
10.2.2 Partial session transfer . 113
10.2.3 Void . 114
10.3 SCC AS . 114
10.3.1 Distinction of requests sent to the SCC AS . 114
10.3.2 PS to PS access transfer procedures at the SCC AS . 114
10.3.3 Void . 119
10.3.4 S-CSCF releasing the source access leg during PS to PS access transfer . 119
10.3.5 P-CSCF releasing the source access leg during PS to PS access transfer . 119
10.3.6 P-CSCF releasing early dialog during PS to PS access transfer . 119
11 Roles for PS-PS access transfer in conjunction with PS-CS access transfer . 120
11.1 Introduction . 120
11.2 SC UE . 120
11.2.1 SC UE procedures for PS to PS+CS access transfer . 120
11.2.1.1 General . 120
11.2.1.2 SC UE procedures for PS to PS+CS access transfer using ICS . 120
11.2.1.3 SC UE procedures for PS to PS+CS access transfer not using ICS . 121
11.2.1.4 SC UE procedures for PS to PS+CS access transfer not using ICS with MSC server assisted mid-
call feature . 121
11.2.2 SC UE procedures for PS+CS to PS access transfer . 122
11.2.2.1 General . 122
11.2.2.2 SC UE procedures for PS+CS to PS access transfer using ICS . 122
11.2.2.3 SC UE procedures for PS+CS to PS access transfer not using ICS . 122
11.3 SCC AS . 123
11.3.1 Distinction of requests sent to the SCC AS . 123
11.3.2 SCC AS procedures for PS to PS+CS access transfer . 123
11.3.3 SCC AS procedures for PS+CS to PS access transfer . 123
12 Roles for PS-CS access transfer, Single Radio . 124
12.1 Introduction . 124
12.2 SC UE procedures for PS to CS access transfer, PS to CS SRVCC . 125
12.2.1 General . 125
12.2.2 ICS-based . 125
12.2.3 Not based on ICS . 126
12.2.3A Not based on ICS with MSC Server assisted mid-call feature . 126
12.2.3B Call in alerting phase . 128
12.2.3B.1 General . 128
12.2.3B.1A Considerations for MSC server assisted mid-call feature . 131
12.2.3B.2 Assignment of Transaction Identifiers to the transferred sessions . 132
12.2.3B.3 Single call in alerting phase or pre-alerting phase . 132
12.2.3B.3.1 Terminating call in alerting phase . 132
12.2.3B.3.2 Originating call in alerting phase . 133
12.2.3B.3.3 PS to CS SRVCC for originating calls in pre-alerting phase . 133
12.2.3B.3.4 PS to CS SRVCC for terminating calls in pre-alerting phase . 133
12.2.3B.4 Established call with a session in alerting phase or in pre-alerting phase . 133
12.2.3B.4.1 Active session with incoming call in alerting phase . 133
12.2.3B.4.2 Held session with new outgoing call in alerting phase or in pre-alerting phase . 134
12.2.4 Abnormal cases . 134
12.2.4.1 Confirmed dialog . 134
12.2.4.2 Early dialog . 134
12.2.4.3 Moving from a 3GPP access to non-3GPP access colliding with SRVCC access transfer . 135
12.2A SC UE procedures for PS to CS access transfer, vSRVCC . 135
12.2A.1 General . 135
12.2A.2 ICS-based . 135
12.2A.3 Not based on ICS . 136
12.2A.4 Void . 136
12.2A.5 Call in alerting phase . 136
12.2A.5A Call in pre-alerting phase . 137
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12.2A.6 Abnormal cases . 137
12.2B SC UE procedures for CS to PS SRVCC . 137
12.2B.1 Distinction of requests . 137
12.2B.2 First call transfer . 138
12.2B.2.1 General . 138
12.2B.2.2 Transfer of call with active speech media component . 139
12.2B.2.3 Transfer of call with inactive speech media component . 139
12.2B.2.4 Transfer of originating call in alerting phase . 139
12.2B.2.5 Transfer of terminating call in alerting phase. 139
12.2B.3 Additional call transfer . 140
12.2B.3.1 General . 140
12.2B.3.2 Transfer of call with active speech media component . 141
12.2B.3.3 Transfer of call with inactive speech media component . 141
12.2B.3.4 Transfer of originating call in alerting phase . 141
12.2B.3.5 Transfer of terminating call in alerting phase. 141
12.2B.4 Procedures after calls are transferred . 141
12.3 SCC AS . 142
12.3.0 General . 142
12.3.0A Distinction of requests sent to the SCC AS . 142
12.3.0B Determine the transferable session set . 143
12.3.1 SCC AS procedures for PS to CS access transfer, PS to CS SRVCC . 143
12.3.2 SCC AS procedures for PS to CS access transfer with MSC server assisted mid-call feature, PS to
CS SRVCC . 144
12.3.2.1 General . 144
12.3.2.2 Transfer of the first session . 145
12.3.2.3 Transfer of an additional session . 146
12.3.3 SCC AS procedures for PS to CS SRVCC, abnormal case . 149
12.3.3.1 PS to CS SRVCC cancelled by MME/SGSN or failure by UE to transition to CS domain for
ongoing session . 149
12.3.3.1A PS to CS SRVCC cancelled by MME/SGSN or failure by UE to transition to CS domain for
session in early
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