Chapter 24

Conferencing in the IMS

In Chapter 23, we introduced the basic technologies and architectures developed by the IETF in the conferencing area. In this chapter, we discuss how those technologies are used in the IMS to provide a conferencing service. This chapter is fairly brief because applying the technologies described in Chapter 23 to the IMS architecture is relatively straight-forward.

24.1 The IMS Conferencing Service

The IMS conferencing service (specified in 3GPP TS 24.147 [32]) is based on the SIPPING conferencing framework (specified in RFC 4353 [272]). Of the specifications produced within the XCON working group, the IMS conferencing service only uses BFCP (specified in RFC 4582 [106]). In the future, as the work in the XCON working group progresses, the IMS conferencing service may use the XCON framework and the conference control protocol developed by the XCON working group. However, at present, they are not yet used in the context of this IMS service.

The IMS conferencing services is based on the tightly-coupled conference model described in Figure 23.3. In the IMS, the conference server is distributed into two logical entities: one handling signaling and the other handling media, as shown in Figure 24.1. The former corresponds to a combination of an AS and an MRFC; the latter corresponds to an MRFP.

PSTN interworking is also part of the IMS conferencing service. Users on the PSTN can participate in IMS conferences through an MGCF, which acts as a conference ...

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