A.2 Introduction

24.2923GPPIP Multimedia (IM) Core Network (CN) subsystem Centralized Services (ICS)Release 17Stage 3TS

A.2.1 General

The signalling flows provided in this annex follow the methodology developed in 3GPP TS 24.228 [10]. The following additional considerations apply:

a) 3GPP TS 24.228 [10] shows separate signalling flows with no configuration hiding between networks, and with configuration hiding between networks. There is no ICS specific functionality associated with hiding, and therefore such separate signalling flows are not show in the present document;

b) 3GPP TS 24.228 [10] does not show the functionality between the S-CSCF and the AS. As ICS can depend on the functionality provided by SCC AS, the signalling flows between S-CSCF and SCC AS are shown in the present document;

c) 3GPP TS 24.228 [10] breaks down the functionality of the various CSCFs. In the present document this is only shown for registration. For all other flows the CSCFs are collapsed into a single entity labelled "Intermediate IM CN subsystem entities";

NOTE: 3GPP TS 24.228 [10] is an informative specification that is no longer maintained and cannot be used for specifying ICS requirements. It is not intended that the reader refer to 3GPP TS 24.228 [10] beyond the subclause on methodology.

d) where entities are combined as in c) above, and the signalling flow is directed to such a combined entity, the contents of the signalling flow represent the contents of the sending entity;

e) where entities are combined as in c) above and the signalling flow originates at such a combined entity, the contents of the signalling flow represent the contents of the receiving entity; and

f) ordering of headers within a table does not follow the conventions of 3GPP TS 24.228 [10].

A.2.2 Key required to interpret signalling flows

The key to interpret signalling flows specified in 3GPP TS 24.228 [10] subclauses 4.1 and 4.2 applies with the additions specified below:

– sip:234150999999999@ics.mnc015.mcc234.3gppnetwork.org represents the temporary public user ID used for registration.

– sip:sccas.home1.net represents the address of the SCC AS on the originating side.

– sip:sccas2.home2.net represents the address of the SCC AS on the terminating side.

Each signalling flow table contains descriptions for headers where the content of the header is new to that signalling flow, as is already performed in 3GPP TS 24.228 [10].

However, 3GPP TS 24.228 [10] includes extensive descriptions for the contents of various headers following each of the tables representing the contents of the signalling flows. Where the operation of the header is identical to that shown in 3GPP TS 24.228 [10], then such text is not reproduced in the present document.

Additional text can also be found on the contents of headers within 3GPP TS 24.228 [10] in addition to the material shown in the present document.

In order to differentiate between messages for SIP and media, the notation in figure A.2-1 is used.

Figure A.2-1: Signalling flow notation