Content for TR 23.820 Word version: 9.0.0
5 Service Interruption scenarios
6 Alternative solutions
7 Conclusions and recommendations
$ Change history
5 Service Interruption scenarios p. 8
5.1 Introduction p. 8
5.2 S-CSCF Service Interruption p. 8
5.2.1 Introduction p. 8
5.2.2 Unregistered User p. 9
5.2.3 Originating Traffic from Registered User p. 10
5.2.4 Terminating Traffic for Registered User p. 11
5.3 P-CSCF Service Interruption p. 12
5.3.1 Introduction p. 12
5.3.2 Originating Traffic p. 12
5.3.3 Terminating Traffic p. 13
5.3.4 Subsequent requests towards P-CSCF without traversing the S-CSCF p. 13
5.4 IMS-UE Service Interruption p. 13
5.5 SIP-AS Service Interruption p. 14
5.5.1 Introduction p. 14
5.5.2 Third Party Registration Request p. 14
5.5.3 Originating Service Request p. 14
5.5.4 Terminating Service Request p. 14
5.6 IP-CAN Service Interruption p. 15
5.7 HSS Service Interruption p. 15
6 Alternative solutions p. 17
6.1 Backup of S-CSCF Information in the HSS p. 17
6.1.1 Introduction p. 17
6.1.2 Normal Registration p. 17
6.1.3 Retrieval of S-CSCF Information p. 18
6.1.4 Removal of S-CSCF Information p. 21
6.1.5 Handling of Originating SIP Request for an Unknown User in the S-CSCF p. 22
6.1.6 Restoration During Re-registration Procedure p. 23
6.1.7 Backup of S-CSCF information after UE's subscription p. 24
6.2 Triggering of initial registration from the S-CSCF or P-CSCF p. 25
6.2A Precautionary de-registration of un-registered users p. 28
6.2B S-CSCF re-assignment for unregistered user p. 28
6.3 Second P-CSCF and deregistration from S-CSCF p. 28
6.4 Monitoring P-CSCF Health p. 31
6.4.1 Introduction p. 31
6.4.2 Monitoring P-CSCF health from the UE p. 31
6.4.3 Monitoring P-CSCF health from the IP GW p. 31
6.5 Possible Solution for SIP-AS Service Restoration p. 34
6.6 Update of S-CSCF Name in the HSS after Loss of Data p. 35
6.6.1 Introduction p. 35
6.6.2 Restart Indication p. 35
6.6.3 S-CSCF Name Check Required Flag p. 36
6.6.4 S-CSCF Name Check by the HSS p. 36
6.7 Forking Service Restoration p. 37
6.8 Possible Solutions for SIP-AS Service Restoration p. 38
6.9 AS Behaviour After HSS Recovery p. 39
6.10 HSS Failover with no loss of service p. 40
6.10.1 Introduction p. 40
6.10.2 Diameter FAILOVER p. 40
6.10.2.1 SLF p. 40
6.10.2.2 I-CSCF, S-CSCF and AS p. 41
7 Conclusions and recommendations p. 41
7.1 S-CSCF Service Interruption p. 41
7.2 S-CSCF Re-Selection during Re-Registration p. 41
7.3 SIP-AS Service Interruption p. 41
7.4 HSS Service Interruption p. 41
7.5 P-CSCF Service Interruption p. 41
$ Change history p. 13
