RE: [Simple] Chat sessions

[Markus.Isomaki at nokia.com]

Hi all,

I think this thread has been a useful discussion on various topics related to conferencing, chat, anonymity, nicknames, display names, sidebars and private messages. Let me try to list my opinions on the different points:

1. "Nicknames" are not specific to MSRP conferences, but can be applied to any type of conferences. There should be more clarity how to convey them in conference-info and in various media transports. Initially RTP and MSRP seem to be enough.

2. There seem to be different scopes of "nicknames":
   a) A single conference instance: I believe the mechanism (or any other mechanism based on INVITE or SDP) proposed in the draft should only address this. Negotiation happens when setting up a session with the focus, and it is thus confusing if it had wider meaning.
   b) A set of conferences that are somehow federated (typically run by the same provider). In this case I believe the reservation of the nickname should be done with an out-of-band mechanism (I guess an XCAP usage similar to reserving list URIs would work), and somehow there should be a "realm" so that it would be possible to determine from a conference URI whether it belongs to the federation or not. If a user has a registered nickname within a realm, he probably still uses the mechanism in a) to announce it within a single conference in this realm. It is then upto the conference server to authorize the usage of the nickname.  
   c) Any SIP services. Again some sort of out-of-band reservation, and then sending each request through a B2BUA that translates the "real" identity to the "nickname". This could be actually used simultaneously with the conference specific systems, i.e. having a "nickname" for a "nickname". 

3. In each case there is a SIP-element that actually knows the "real" identity of the user. In cases 2a) and 2b) it is the conference focus, in 2c) it is the B2BUA. Only the nickname is shown beyond this element, as intended. 

3. As Aki explained, sidebars and private IMs within a conference are two different things. Sidebars are subconferences, that include a certain subset of the participants in the main conference. They need to be explicitly created and deleted. Private IMs within a conference are also targeted to a subset of the conference participants. But there is no need to setup a sidebar or any other additional context to send them. The recipients can simply be signaled within each message (as proposed by using CPIM To header). This seems to be a specific property of IM, as this sort of addressing would be impossible e.g. in RTP. In theory priate messaging facility could be supported by sidebars, but in this case the focus would need to have as many sidebars constantly setup, as there are different possible participant subset combinations. Way too complex and not needed.

I think the current draft needs to be split into at least two:
- Private IMs in MSRP conferences
- Nicknames in conferences (I suppose the above one would have a dependency on this one)
  This should solve the scope of 2a)

There could be further (XCAP usage?) drafts describing the solutions to 2b) and 2c).

Regards,
	Markus     

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