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

From: Peter Saint-Andre - &yet <[email-masked]>
Date: Wed, 08 Oct 2014 20:18:12 -0600

On 8/20/14, 7:14 AM, Peter Saint-Andre wrote:
> On 6/20/14, 2:31 PM, Ben Campbell wrote:
>>
>> On Jun 19, 2014, at 10:52 PM, Peter Saint-Andre <[email-masked]>
>> wrote:
>>
>>> On 6/19/14, 3:49 PM, Ben Campbell 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.
>>>
>>> As you pointed out later in this thread, this is a simplifying
>>> assumption to make the diagrams and explanations easier to follow.
>>
>> Do you concur that that assumption should be pointed out? (Or did I
>> miss some place where it is already?)
>
> Hi Ben, I've continued to think about this. I now conclude it would be
> better to show the proper architecture: i.e., signalling traffic from
> the XMPP side is sent to the conference focus, and groupchat media
> traffic is sent to the MSRP switch. This is especially important because
> in the XMPP world we don't consider groupchat messages to be "media".
> Making this clear in the text, diagrams, and protocol flows will help
> developers understand the differences.
>
> I'll work these concepts into the next version of the I-D, which I hope
> to work on in the next week or two.

Sorry about being so slow.

When I look at draft-ietf-simple-chat, I see that the conference focus 
and the MSRP switch both have the same address, although the URIs differ 
because the focus has a SIP URI and the switch has an MSRP URI. The 
focus seems to inform the participant about the MSRP URI to contact 
using an SDP a= line specifying a "path" attribute, such as:

a=path:msrp://chat.example.com:7654/jshA7weztas;tcp

Is it allowable for the focus to have an address different from the 
switch? For example, could we have an architecture like this?

    ####################################################################
    #                                                                  #
    #                +------------------+                              #
    #                | msrp.example.org |%%%%%%%%%%%%                  #
    #            &&&&| (MSRP switch) +-----+        %                  #
    #            &   +---------------| M2X |        %                  #
    #            &           %       | GW  |...     %                  #
    #            &           %       +-----+  .  +-----+               #
    #            &           %                .  | X2M |               #
    #            &           %           +-------| GW  |--+            #
    #            &           %           |       +-----+  |            #
    #  +------------------+  %       +-----+    +-------------------+  #
    #  | chat.example.org |**********| X2S |    | muc.example.com   |  #
    #  | (conference      |  %       | GW  |    | (MUC service)     |  #
    #  | focus)     +-----+  %       +-----+    +-------------------+  #
    #  +------------| S2X |  %           | example.com    |            #
    #        *      | GW  |..............| (XMPP server)  |            #
    #        *      +-----+  %           +----------------+            #
    #        *               %                 .                       #
    #        *               %                 .                       #
    #        [email-masked]           [email-masked]            #
    #                                                                  #
    ####################################################################

Where:

    . = XMPP
    % = MSRP
    * = SIP
    & = app-specific

I ask because having a separate address for the switch (effectively 
redirecting from the focus to the switch) might introduce challenges 
with authorization of entities on the XMPP side (e.g., a client or 
server might whitelist the focus address but that authorization decision 
wouldn't apply to the switch address).

For now, while editing draft-ietf-stox-groupchat I will keep the focus 
and switch addresses the same.

Peter

--
Peter Saint-andre
https://andyet.com/

-- 
Peter Saint-Andre
https://andyet.com/