H (Normative)  IP-Connectivity Access Network specific concepts when using DOCSIS to access IM CN subsystem |R7|  Word‑p. 827

H.1  Scope

The present annex defines IP-CAN specific requirements for a call control protocol for use in the IP Multimedia (IM) Core Network (CN) subsystem based on the Session Initiation Protocol (SIP), and the associated Session Description Protocol (SDP), where the IP-CAN is a DOCSIS cable access network.

DOCSIS (Data Over Cable Service Interface Specification) is a term referring to the ITU-T Recommendation J112 [87] Annex B standard for cable modem systems.

H.2  DOCSIS aspects when connected to the IM CN subsystem

H.2.1  Introduction

A UE accessing the IM CN subsystem, and the IM CN subsystem itself, utilise the services provided by the DOCSIS cable access network to provide packet-mode communication between the UE and the IM CN subsystem.

From the perspective of the UE, the necessary IP-CAN bearer for signalling is transparently available to the UE.

The UE is not directly involved in requests for IP-CAN bearer(s) for media flow(s). The IM CN interacts with the PCRF in the DOCSIS IP-CAN to establish IP-CAN bearer(s) for media flow(s), on behalf of the UE.

H.2.2  Procedures at the UE

H.2.2.1  Activation and P-CSCF discovery

Prior to communication with the IM CN subsystem, the UE shall perform a Network Attachment procedure as defined in the CableLabs PacketCable specifications PKT-TR-ARCH-FRM [88]. When using DOCSIS, both IPv4 and IPv6 UEs may access the IM CN subsystem. The procedures for P-CSCF discovery defined in subclause 9.2.1 of this document apply.

H.2.2.1A  Modification of IP-CAN used for SIP signalling

Not applicable.

H.2.2.1B  Re-establishment of the IP-CAN used for SIP signalling

Not applicable.

H.2.2.1C  P-CSCF restoration procedure |R9|

A UE supporting the P-CSCF restoration procedure uses the keep-alive procedures described in RFC 6223.

If the P-CSCF fails to respond to the keep-alive request the UE shall acquire a different P-CSCF address using any of the methods described in the subclause H.2.2.1 and perform an initial registration as specified in subclause 5.1.

H.2.2.2  Void

H.2.2.3  Void

H.2.2.4  Void

H.2.2.5  Handling of the IP-CAN for media  Word‑p. 828

H.2.2.5.1  General requirements

The UE does not directly request resources for media flow(s).

H.2.2.5.1A  Activation or modification of IP-CAN for media by the UE

Not applicable.

H.2.2.5.1B  Activation or modification of IP-CAN for media by the network

Not applicable.

H.2.2.5.1C  Deactivation of IP-CAN for media |R11|

Not applicable.

H.2.2.5.2  Special requirements applying to forked responses

The UE does not directly request resources for media flow(s). As a result there are no special UE requirements applying to forked responses.

H.2.2.5.3  Unsuccessful situations

Not applicable.

H.2.2.6  Emergency service

H.2.2.6.1  General |R14|

If attached to network via DOCSIS access technology, the UE shall always consider being attached to its home operator's network for the purpose of emergency calls.

H.2.2.6.1A  Type of emergency service derived from emergency service category value |R15|

Not applicable.

H.2.2.6.1B  Type of emergency service derived from extended local emergency number list |R15|

Not applicable.

H.2.2.6.2  eCall type of emergency service |R14|  Word‑p. 829

The UE shall not send an INVITE request with Request-URI set to "urn:service:sos.ecall.manual" or "urn:service:sos.ecall.automatic".

H.2.2.6.3  Current location discovery during an emergency call |R14|

Void.

H.2A  Usage of SDP |R8|

H.2A.0  General |R9|

Not applicable.

H.2A.1  Impact on SDP offer / answer of activation or modification of IP-CAN for media by the network

Not applicable.

H.2A.2  Handling of SDP at the terminating UE when originating UE has resources available and IP-CAN performs network-initiated resource reservation for terminating UE

Not applicable.

H.2A.3  Emergency service |R11|

No additional procedures defined.

H.3  Application usage of SIP

H.3.1  Procedures at the UE

H.3.1.0  Void

H.3.1.0a  IMS_Registration_handling policy |R15|

Not applicable.

H.3.1.1  P-Access-Network-Info header field

If the UE is aware of the access technology, the UE shall include the P-Access-Network-Info header field where indicated in subclause 5.1.

H.3.1.1A  Cellular-Network-Info header field |R13|

Not applicable.

H.3.1.2  Availability for calls |R8|  Word‑p. 830

Not applicable.

H.3.1.2A  Availability for SMS |R11|

Void.

H.3.1.3  Authorization header field |R10|

When using SIP digest or SIP digest without TLS, the UE need not include an Authorization header field on sending a REGISTER request, as defined in subclause 5.1.1.2.1.

H.3.1.4  SIP handling at the terminating UE when precondition is not supported in the received INVITE request, the terminating UE does not have resources available and IP-CAN performs network-initiated resource reservation for the terminating UE |R13|

Not applicable.

H.3.1.5  3GPP PS data off |R14|

Not applicable.

H.3.1.6  Transport mechanisms |R15|

No additional requirements are defined.

H.3.1.7  RLOS |R16|

Not applicable.

H.3.2  Procedures at the P-CSCF

H.3.2.0  Registration and authentication |R12|

Void.

H.3.2.1  Determining network to which the originating user is attached

If the access-type field in the P-Access-Network-Info header field indicated DOCSIS access the P-CSCF shall assume that the initial request for a dialog or standalone transaction or an unknown method destined for a PSAP is initiated in the same country.

H.3.2.2  Location information handling  Word‑p. 831

Upon receipt of an initial request for a dialog or standalone transaction or an unknown method, the P-CSCF based on local policy may include a P-Access-Network-Info header field.

H.3.2.3  Void

H.3.2.4  Void

H.3.2.5  Void

H.3.2.6  Resource sharing |R13|

Not applicable.

H.3.2.7  RLOS |R16|

Not applicable.

H.3.3  Procedures at the S-CSCF |R8|

H.3.3.1  Notification of AS about registration status

Not applicable.

H.3.3.2  RLOS |R16|

Not applicable.

H.4  3GPP specific encoding for SIP header field extensions

H.4.1  Void

H.5  Use of circuit-switched domain |R8|

There is no CS domain in this access technology.

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