E.2 Fixed broadband aspects when connected to the IM CN subsystem

24.2293GPPIP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP)Release 18Stage 3TS

E.2.1 Introduction

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

Requirements for the IP Edge node, defined in ETSI ES 282 001 [138]in support of this communication are outside the scope of this document and specified elsewhere.

From the UEs perspective, it is assumed that one or more IP-CAN bearer(s) are provided, in the form of connection(s) managed by the layer 2 (e.g. DSL modem supporting the UE).

In the first instance, it is assumed that the IP-CAN bearer(s) is (are) statically provisioned between the UE and the IP Edge node, defined in ETSI ES 282 001 [138], according to the user’s subscription.

It is out of the scope of the current Release to specify whether a single IP-CAN bearer is used to convey both signalling and media flows, or whether several PVC connections are used to isolate various types of IP flows (signalling flows, conversational media, non conversational media…).

The end-to-end characteristics of the fixed-broadband IP-CAN bearer depend on the type of access network, and on network configuration. The description of the network PVC termination (e.g., located in the DSLAM, in the BRAS…) is out of the scope of this annex.

E.2.2 Procedures at the UE

E.2.2.1 Activation and P-CSCF discovery

Fixed-broadband bearer(s) is (are) statically provisioned in the current Release.

Unless a static IP address is allocated to the UE, prior to communication with the IM CN subsystem, the UE shall perform a Network Attachment procedure depending on the used fixed-broadband access type. When using a fixed-broadband access, both IPv4 and IPv6 UEs may access the IM CN subsystem. The UE may request a DNS Server IPv4 address(es) via RFC 2132 [20F] or a DNS Server IPv6 address(es) via RFC 3315 [40].

The methods for P-CSCF discovery are:

I. When using IPv4, employ the Dynamic Host Configuration Protocol (DHCP) RFC 2132 [20F], the DHCPv4 options for SIP servers RFC 3361 [35A], and RFC 3263 [27A] as described in subclause 9.2.1. When using IPv6, employ Dynamic Host Configuration Protocol for IPv6 (DHCPv6) RFC 3315 [40], the DHCPv6 options for SIP servers RFC 3319 [41] and DHCPv6 options for Domain Name Servers (DNS) RFC 3646 [56C] as described in subclause 9.2.1. In case the DHCP server provides several P-CSCF addresses or FQDNs to the UE, the UE shall select the P-CSCF address or FQDN as indicated in RFC 3319 [41]. If sufficient information for P-CSCF address selection is not available, selection of the P-CSCF address by the UE is implementation specific.

II. The UE selects a P-CSCF from the list in the IMS management object as specified in 3GPP TS 24.167 [8G].

The UE shall use method II to select a P-CSCF if the IMS management object contains the P-CSCF list. Otherwise, the UE shall use method I to select a P-CSCF.

E.2.2.1A Modification of a fixed-broadband connection used for SIP signalling

Not applicable.

E.2.2.1B Re-establishment of a fixed-broadband connection used for SIP signalling

Not applicable.

E.2.2.1C P-CSCF restoration procedure

A UE supporting the P-CSCF restoration procedure uses the keep-alive procedures described in RFC 6223 [143].

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

E.2.2.2 Void

E.2.2.3 Void

E.2.2.4 Void

E.2.2.5 Fixed-broadband bearer(s) for media

E.2.2.5.1 General requirements

The UE can establish media streams that belong to different SIP sessions on the same fixed-broadband bearer.

E.2.2.5.1A Activation or modification of fixed-broadband bearers for media by the UE

If the UE receives indication within the SDP according to RFC 3524 [54] that media stream(s) belong to group(s), and if several fixed-broadband bearers are available to the UE for the session, the media stream(s) may be sent on separate fixed-broadband bearers according to the indication of grouping. The UE may freely group media streams to fixed-broadband bearers in case no indication of grouping is received from the P-CSCF.

If the UE receives media grouping attributes in accordance with RFC 3524 [54] that it cannot provide within the available fixed-broadband bearer(s), then the UE shall handle such SDP offers in accordance with RFC 3388 [53].

The UE can receive a media authorization token in the P-Media-Authorization header field from the P-CSCF according to RFC 3313 [31]. If a media authorization token is received in the P-Media-Authorization header field when a SIP session is initiated, the UE shall reuse the existing fixed-broadband bearer(s) and ignore the media authorization token.

E.2.2.5.1B Activation or modification of fixed-broadband bearers for media by the network

Not applicable.

E.2.2.5.1C Deactivation of fixed-broadband bearers for media

Not applicable.

E.2.2.5.2 Special requirements applying to forked responses

Since the UE is unable to perform bearer modification, forked responses place no special requirements on the UE.

E.2.2.5.3 Unsuccessful situations

Not applicable.

E.2.2.6 Emergency service

E.2.2.6.1 General

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

NOTE: In fixed-broadband the UE is unable to receive any indication from the network, that would allow the UE to determine, whether it is currently attached to its home operator’s network or to a different network, so the UE assumes itself always attached to the home operator’s network when connected via fixed-broadband access technology.

E.2.2.6.1A Type of emergency service derived from emergency service category value

Not applicable.

E.2.2.6.1B Type of emergency service derived from extended local emergency number list

Not applicable.

E.2.2.6.2 eCall type of emergency service

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

E.2.2.6.3 Current location discovery during an emergency call

Void.