Liaison statement
CLUE WG response to LS to IETF CLUE WG on media handling aspects related to CLUE protocol

1. Overall
3GPP SA4 asked IETF CLUE to inform SA4 on the progress of CLUE work group on
any media handling aspects related to CLUE protocol.

2. CLUE status:
It was brought to our attention that many CLUE documents are already endorsed
by 3GPP in 3GPP TS 24.103 (http://www.3gpp.org/DynaReport/24103.htm ).

From the attached document (SP-140483_S4-140989 Rel-13_WID IMS_TELEP) we
conclude that 3GPP SA4 has an interest in the following aspects and we will
try to respond what is the CLUE status for each item

• Media codecs (speech, video, real-time text) for IMS-based telepresence –
CLUE does not recommend any specific codecs. The topic is out of scope for
CLUE WG.

•Media configuration including session setup and control procedures for
IMS-based telepresence, and media provisioning aspects of capability
negotiation based on SDP and CLUE protocols, etc. – This is the major focus of
the CLUE WG as specified in the WG charter (clue/charter/). The following
documents defines these topic:

- Framework for Telepresence Multi-Streams in draft-ietf-clue-framework-21
defines a framework for a protocol to enable devices in a telepresence
conference to interoperate. This document is now going to publication which
means that the CLUE WG agrees that it is ready
- CLUE signaling in draft-ietf-clue-signaling-05 defines how to use SIP and
SDP to establish a Telepresence call. The document is still a work in
progress.
- The CLUE protocol is specified in draft-ietf-clue-protocol-03 specifies the
negotiation of a CLUE telepresence session. It is using the XML schema for the
CLUE data model specified in draft-ietf-clue-data-model-schema-07 . These
documents are work in progress but they are quiet mature.

• Set-up and control of the individual media streams between clients including
interactivity, such as adding and dropping of media components, as well as
end-to-end QoS handling, etc. for IMS-based telepresence. – This is not in the
scope of the CLUE WG, the support for set-up and control of individual streams
is based on existing tools that were specified by other WGs like AVTcore,
AVText, Payload and MMUSIC.
• Data transport including usage of RTP / RTCP protocols, RTP profiles, RTP
payload formats, RTP mapping, media synchronization, etc. for IMS-based
telepresence, e.g., in relation to negotiation and establishment of the CLUE
data channel, and exchange of CLUE ADVERTISEMENT and CONFIGURE messages – This
topic is discussed in the CLUE signaling document and some aspects of mapping
RTP streams to CLUE Media Captures are discussed in
draft-ietf-clue-rtp-mapping-04
• Requirements and guidelines for media adaptation in IMS-based telepresence,
for example in response to changes of network bandwidth – this is not in the
scope of CLUE work. A general solution for congestion control is discussed in
the IETF RMCAT WG.