Re: [Stox] I-D Action: draft-ietf-stox-groupchat-05.txt

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On 19 Jun 2014, at 18:49, Ben Campbell <[e-mail]> wrote:

> Hi Peter,
> 
> [Disclaimer: this was a higher level review than for the previous version--I mainly looked to see how the previous discussions about the architecture rendered into the draft. ]
> 
> This version is much improved. I think you've gotten the "FAIL" off of it. But of course, cleaning up the architecture reveals a few things :-)
> 
> Section 4:
> 
> I think the addition of section 4 helps a lot in general.
> 
> The architecture treats the MSRP Conference server to be a monolithic thing. The result of this is, in the examples, all the SIP and MSRP traffic go to the sample place. That doesn't match the architecture from RFC 4975 and simple-chat, where the signaling (SIP) is separate from media (MSRP).  simple-chat talks in terms of a conference focus that handles the signaling side, and an MSRP switch that handles the media (MSRP) side.

For all practical reasons, they do end up in the same place. Otherwise, how would the MSRP switch communicate with the SIP server in order to share the information it knows about the participants or add/remove the media plane slots? Do we need another protocol or mechanism between the two? Even speculating about this possibility would introduce some unnecessary uncertainty for those contemplating implementing this specification.

> Now, it's perfectly okay to collocate those services into an MSRP Conference Server in real deployments, and okay to show it that way in this draft for the sake of simplicity.
> But it would be worth mentioning that in section 4, and maybe also mentioning that any interaction between the conference focus and MSRP switch are out of scope (and irrelevant) for this draft.

I would skip mentioning this this, based on the argument I made above. It sounds as scary as "there is something we don’t know how it has to be done but is not our problem”. 

> Along the same line, I assume the public "SIP side" interface of the X2M gateway looks like a conference focus plus an MSRP switch to the outside world. Again, these could be logically separate, but co-located.
> Section 5 (and subsections)
> 
> The diagram does not show the transport (e.g. TCP) connection establishment for MSRP. I think it would be useful to do so. Also, the active endpoint (the one opening the transport connection) has to send an immediate MSRP SEND request once the connection is established. (I don't _think_ simple-chat extended that to allow an initial NICKNAME to replace that--but I may have missed it.)
> 
> Section 6 (and subsections)
> 
> The diagram in section 6 still has a "SIP Server". It's still not clear to me what that represents. It _could_ be a SIP Proxy, in which the MSRP session would skip it. I guess it could be an MSRP aware b2bua, in which case the MSRP session might also traverse it. It could be a combo of a SIP proxy and an RFC 4976 MSRP relay, but that would require additional MSRP signaling.
> 
> I would suggest promoting it to some sort of SIP "service" or "service provider", which is more of a cloud than a box, and having the MSRP traffic skip it entirely. Or removing it entirely--there's no _protocol_ reason that a SIP user needs an outbound service provider (even though there might be perfectly good _deployment_ reasons.)
> 
> I also think section 6 needs to show the same sort of MSRP connection establishment and initial SEND request as mentioned for 5.
> 
> Thanks!
> 
> Ben.
> 
> 
> On Jun 10, 2014, at 10:46 PM, Peter Saint-Andre <[e-mail]> wrote:
> 
>> An attempt to address feedback received recently, as well as the "FAIL" issue...
>> 
>> On 6/10/14, 9:44 PM, [e-mail] wrote:
>>> 
>>> A New Internet-Draft is available from the on-line Internet-Drafts directories.
>>> This draft is a work item of the SIP-TO-XMPP Working Group of the IETF.
>>> 
>>>        Title           : Interworking between the Session Initiation Protocol (SIP) and the Extensible Messaging and Presence Protocol (XMPP): Groupchat
>>>        Authors         : Peter Saint-Andre
>>>                          Saul Ibarra
>>>                          Salvatore Loreto
>>> 	Filename        : draft-ietf-stox-groupchat-05.txt
>>> 	Pages           : 40
>>> 	Date            : 2014-06-10
>>> 
>>> Abstract:
>>>   This document defines a bidirectional protocol mapping for the
>>>   exchange of instant messages in the context of a multiparty chat
>>>   session among users of the Session Initiation Protocol (SIP) and
>>>   users of the Extensible Messaging and Presence Protocol (XMPP).
>>>   Specifically, this document defines a mapping between the SIP-based
>>>   Message Session Relay Protocol (MSRP) and the XMPP Multi-User Chat
>>>   (MUC) extension.
>>> 
>>> 
>>> The IETF datatracker status page for this draft is:
>>> https://datatracker.ietf.org/doc/draft-ietf-stox-groupchat/
>>> 
>>> There's also a htmlized version available at:
>>> http://tools.ietf.org/html/draft-ietf-stox-groupchat-05
>>> 
>>> A diff from the previous version is available at:
>>> http://www.ietf.org/rfcdiff?url2=draft-ietf-stox-groupchat-05
>>> 
>>> 
>>> Please note that it may take a couple of minutes from the time of submission
>>> until the htmlized version and diff are available at tools.ietf.org.
>>> 
>>> Internet-Drafts are also available by anonymous FTP at:
>>> ftp://ftp.ietf.org/internet-drafts/
>>> 
>>> _______________________________________________
>>> stox mailing list
>>> [e-mail]
>>> https://www.ietf.org/mailman/listinfo/stox
>>> 
>> 
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