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Content for TR 23.850 Word version: 11.0.0

1… 4A…

4A Reference Architecture p. 9

5 Solutions Alternatives for Originating Sessions p. 9

5.1 CS Copy Cat model based on V-CSCF p. 9

5.1.1 Reference Architecture p. 9

5.1.2 Functional Entities p. 10

5.1.2.1 V-CSCF p. 10

5.1.2.2 IBCF p. 10

5.1.3 Procedures and Flows p. 10

5.1.3.1 Registration procedures p. 10

5.1.3.2 Session origination procedures with VPLMN routing p. 10

5.1.3.3 VPLMN originating call routing with CS breakout in VPLMN p. 12

5.1.3.4 VPLMN originating call routing with CS breakout in Destination PLMN p. 13

5.1.3.5 Home routing procedures p. 14

5.1.3.5.1 CS copy cat model for home routing p. 14

5.1.3.5.2 Home routing without involving V-CSCF p. 15

5.1.3.5.3 CS copy cat model for home routing using Home Routing AS p. 16

5.2 Transit routing via VPLMN p. 18

5.2.1 General p. 18

5.2.2 Architecture impacts p. 18

5.2.3 Example use cases p. 18

5.2.3.1 Transit routing via VPLMN after successful ENUM/DNS resolution p. 18

5.2.3.2 Transit routing via VPLMN for CS breakout p. 19

5.2.4 Session origination procedures p. 20

5.2.4.1 Session origination procedure for transit routing via VPLMN p. 20

5.2.4.2 Session origination procedure for home routing p. 21

5.3 Transit function in the visited network p. 22

5.3.1 General p. 22

5.3.2 Alternative A - configuration based route-back p. 22

5.3.2.1 Description p. 22

5.3.2.2 Routing back to visited network p. 24

5.3.2.3 Evaluation p. 24

5.3.3 Alternative B - Route-back triggered by the visited network p. 24

5.3.3.1 Description p. 24

5.3.3.2 Routing back by using SIP Trunk Group Parameters p. 26

5.3.3.2.1 Session origination procedure for routing via VPLMN p. 26

5.3.3.2.2 Session origination procedure for home routing p. 28

5.3.3.3 Evaluation p. 28

5.4 IMS home routing p. 28

5.4.1 General p. 28

5.4.2 Architecture impacts p. 29

5.4.3 Example home routing use cases p. 29

5.4.3.1 Forced routing to HPLMN p. 29

5.4.3.2 Routing to another HPLMN subscriber p. 29

5A Solutions Alternatives for Terminating Sessions p. 30

5A.1 Use of IBCF and removal of OMR attributes p. 30

6 Alternatives Assessment and Conclusions p. 30

6.1 Assessment p. 30

6.1.1 General p. 30

6.1.2 Specific Criteria p. 31

6.1.3 Home Routing p. 31

6.2 Conclusions p. 32

A CS voice Charging and interconnection principle - high level description p. 33

A.1 General Business Logic p. 33

A.2 Payment flows p. 34

A.2.1 Deterministic charging p. 35

A.2.2 IPX Voice Hubbing p. 35

A.3 Accounting principles p. 35

A.3.1 GSMA roaming business model p. 35

A.3.2 Application of GSMA roaming business model to IMS: no home routing p. 36

A.3.3 Application of GSMA roaming business model to IMS: home routing p. 38

B Recommendations for the Convergent Interconnection p. 39

B.1 Convergent Interconnection p. 39

$ Change history p. 40