Table of Contents for TS 23.380 Word version: 19.0.0

Introduction p. 7

Scope p. 8

References p. 8

Definitions, symbols and abbreviations p. 9

3.1	Definitions p. 9
3.2	Abbreviations p. 9

Restoration of Data in the S-CSCF p. 10

4.1

General p. 10

4.2

Registration Procedure p. 10

4.2.1	Introduction p. 10
4.2.2	S-CSCF Restoration after Failure p. 10
4.2.2A	SBI Support for S-CSCF Restoration after Failure \|R16\| p. 10
4.2.3	S-CSCF Restoration during Registration Process p. 11

4.3

UE Terminating Procedure p. 12

4.3.1	Introduction p. 12
4.3.2	S-CSCF Restoration after Restart p. 12
4.3.3	S-CSCF Restoration after Failure p. 12
4.3.4	SBI Support for S-CSCF Restoration after Failure \|R16\| p. 12

4.4

UE Originating Procedure p. 13

4.4.1	Introduction p. 13
4.4.2	S-CSCF Restoration after Restart p. 13
4.4.3	S-CSCF Restoration after Failure p. 13

4.5

SIP-AS Originating Procedure p. 14

4.5.1	Introduction p. 14
4.5.2	S-CSCF Restoration after Restart p. 14
4.5.3	S-CSCF Restoration after Failure p. 14

4.6

S-CSCF Data Restoration Information Backup and Update Procedures p. 14

4.6.1	Introduction p. 14
4.6.2	Backup and Update of S-CSCF Restoration Information during Registration Process p. 14
4.6.3	Backup and Update of S-CSCF Restoration Information after UE's Subscription p. 15
4.6.4	Backup and Update of S-CSCF Restoration Information after P-CSCF's Subscription \|R16\| p. 15

Recovery after P-CSCF failure |R9| p. 16

5.0

General p. 16

5.1

Update PDP context/Bearer at P-CSCF failure p. 16

5.1.1	General requirements p. 16
5.1.2	Network recovery information flow - Update PDP context / Bearer p. 16
5.1.3	Network recovery information flow with S5 PMIP \|R11\| p. 18

5.2

Inform UE about P-CSCF failure p. 19

5.2.1	General requirements p. 19
5.2.2	Network recovery information flow - Inform UE at P-CSCF failure p. 19
5.2.3	Network recovery information flow - Inform UE at P-CSCF failure with S5 PMIP \|R11\| p. 21

5.3

Network recovery information flow - UE uses keep alive mechanism p. 22

5.4

HSS-based P-CSCF restoration for 3GPP access |R12| p. 23

Introduction p. 23

Description p. 23

General p. 23

P-CSCF restart/failure detection by S-CSCF p. 25

5.4.2.2.1	General p. 25
5.4.2.2.2	Direct connection from S-CSCF to P-CSCF p. 25
5.4.2.2.3	S-CSCF connection to P-CSCF via IBCF/ATCF p. 25

5.4.2.3

MME/SGSN mechanism support p. 26

5.4.3

PCO-based optional extension p. 26

5.4.3.1	Introduction p. 26
5.4.3.2	Description p. 26

5.4.4

UE indication of support for "Update PDP context/bearer at P-CSCF failure" Restoration |R16| p. 29

5.4.5

Coexistence with "Update PDP context/bearer at P-CSCF failure" mechanism p. 29

5.4.6

HSS based P-CSCF restoration in roaming scenarios p. 29

5.5

PCRF-based P-CSCF restoration |R12| p. 30

5.5.1

Introduction p. 30

5.5.2

PCRF-based P-CSCF restoration information flow - deactivate PDN connection/PDP context p. 30

5.5.3

PCO-based optional extension p. 33

5.5.3.1	Introduction p. 33
5.5.3.2	Description p. 33
5.5.3.3	UE indication of support for "Update PDP context/bearer at P-CSCF failure" Restoration p. 33

5.5.4

Coexistence with "Update PDP context/bearer at P-CSCF failure" mechanism p. 33

5.5.5

P-CSCF restoration in roaming scenarios for PCRF based solution p. 33

5.6

P-CSCF restoration for WLAN |R13| p. 34

5.6.1

Introduction p. 34

5.6.2

Basic mechanism for the HSS-based solution p. 34

5.6.2.1	Overview and principles p. 34
5.6.2.2	Description p. 34

5.6.3

Basic mechanism for the PCRF-based solution p. 36

5.6.4

Optional extension for the HSS and PCRF-based solutions for the TWAN access p. 36

5.6.4.1	Overview and principles p. 36
5.6.4.2	Description p. 37
5.6.4.3	Indication of UE support of the P-CSCF restoration extension for the TWAN access p. 38

5.6.5

Optional extension for the HSS and PCRF-based solutions for the untrusted WLAN access p. 38

5.6.5.1	Overview and principles p. 38
5.6.5.2	Description p. 38
5.6.5.3	Indication of UE support of the P-CSCF restoration extension for the untrusted WLAN access p. 40

5.6.6

Supported features and capabilities p. 40

5.6.6.1	Introduction p. 40
5.6.6.2	Feature support in the HSS and S-CSCF p. 40
5.6.6.3	Feature support in the 3GPP AAA Server p. 40
5.6.6.4	Feature support in the PGW p. 41
5.6.6.5	Feature support in the TWAN p. 41
5.6.6.6	Feature support in the ePDG p. 41
5.6.6.7	Capability support in the UE p. 41

5.7

Interaction between P-CSCF restoration and NBIFOM |R13| p. 42

5.7.1	Introduction p. 42
5.7.2	HSS-based solution p. 42
5.7.3	PCRF-based solution p. 43

5.8

P-CSCF Restoration for 5GC |R15| p. 43

5.8.1

Introduction p. 43

5.8.2

Common Procedures for P-CSCF Restoration in 5GC p. 43

5.8.2.1	General p. 43
5.8.2.2	P-CSCF Address List Update Procedure p. 44
5.8.2.3	DHCP based P-CSCF Selection Triggering Procedure p. 44
5.8.2.4	PDU Session Release with Reactivation Procedure p. 45

5.8.3

P-CSCF Failure Detection at SMF/UPF p. 46

5.8.3.1	Overview and Principles p. 46
5.8.3.2	P-CSCF Monitoring and Failure Detection Procedure p. 46

5.8.4

UDM/HSS Based P-CSCF Restoration p. 48

5.8.4.1	Overview and principles p. 48
5.8.4.2	Trigger P-CSCF Restoration Procedure via SMF p. 48
5.8.4.3	Trigger P-CSCF Restoration Procedure via AMF p. 50

5.8.5

PCF Based P-CSCF Restoration p. 51

5.8.5.1	Introduction p. 51
5.8.5.2	Trigger P-CSCF Restoration Procedure via PCF p. 51

5.9

P-CSCF Restoration in EPC with 5GC interworking |R15| p. 52

5.10

P-CSCF Restoration in EPC for untrusted WLAN when N10 is used instead of S6b |R16| p. 53

Recovery after SCC AS failure |R13| p. 53

6.1

General p. 53

6.2

General Procedure p. 53

6.2.1

Enhanced Third Party Registration Procedure p. 53

6.2.1.1	Introduction p. 53
6.2.1.2	Description p. 53

6.2.2

Enhanced Service Request Procedure p. 54

6.2.2.1	Introduction p. 54
6.2.2.2	Description p. 55

Detection of EPC/5GC NF Failures and IMS Restoration Procedures |R19| p. 55

7.1

General p. 55

7.2

UE Terminating Procedure p. 56

7.2.1

Introduction p. 56

7.2.2

P-CSCF triggering SMF/PGW-C failure checking p. 56

7.2.3

P-CSCF receiving EPC/5GC NF failure notification from PCRF/PCF p. 58

7.2.3.1	Introduction p. 58
7.2.3.2	Description p. 58

Recovery after PCRF/PCF failure |R19| p. 59

8.1

General p. 59

8.2

PCRF/PCF bypass procedures p. 59

8.2.1	General Requirement p. 59
8.2.2	Establishment of EPS bearer/QoS flow used for IMS signalling with PCRF/PCF bypassing p. 60
8.2.3	IMS MO procedure of PCRF/PCF bypass p. 60
8.2.4	IMS MT procedure of PCRF/PCF bypass p. 61
8.2.5	Dedicated IMS bearer termination procedure of PCRF/PCF bypass p. 62

Change history p. 62