Re: [Simple] RE: [xmppwg] Action Item: character mappings for interoperability

Is the context of this thread IM only, or do we also care about 
presence? I am not sure the issues are always exactly the same, since IM 
addresses may be delivered as part of presence.

I wonder (vaguely) if draft-daigle-napstr-03.txt is applicable here. 
Also, if I recall we _do_ have guidance on how to map an im: url to a 
concrete service using SRV, don't we? It seems to me that if I am a SIP 
user, the only real hope I have of cross-protocol interoperability is to 
advertise a PRES or IM URI. Other systems may be able to reach SIP URIs 
on an ad-hoc basis, but the abstract schema provide a more general 
approach.

More inline:

Adam Roach wrote:

> I'm cross posting this to SIMPLE to help cross-pollinate some
> ideas here.
> 
> Joe Hildebrand [mailto:JHildebrand@jabber.com] wrote:
> 
> [huge snip]
> 
> 
>>Example: josé#26;bób@jabber.com becomes 
>>im:jos%c3%a9&b%c3%b3b@jabber.com
>>(note for the MIME-impaired: that's jose' and bo'b)
>>
>>Actually, it's not clear to me from RFC 3428 whether I should 
>>map into sip:, sips: or im:; I could use some guidance here
>>from the SIMPLE folk.
> 
> 
> Well, they're all (potentially) different namespaces. In particular,
> there's nothing (other than a possible site-local policy) that would
> ensure that "im:adam@dynamicsoft.com" would map to the same user as
> "sip:adam@dynamicsoft.com" -- so, you need to have some mechanism
> by which a distinction is performed. I'll get to that in a second.
> 
> By contrast, "sip:adam@dynamicsoft.com" and
> "sips:adam@dynamicsoft.com" *will* always refer to the same
> user:
> 
>    Any resource described by a SIP URI can be
>    "upgraded" to a SIPS URI by just changing the scheme, if it is
>    desired to communicate with that resource securely.
> 
> So, when you get to a gateway that is going from XMPP to SIP,
> I would posit that selection of "sip:" would be appropriate
> when SASL isn't being used on the XMPP side, and that "sips:"
> would be appropriate when it is.
> 
> Now, for the issue I deferred: when a message arrives for a
> jid, how do you know what to do with it? Let's imagine that I
> send an IM (from an XMPP client) to the jid
> "JHildebrand@jabber.com". If my understanding is correct,
> this *must* end up being routed to the server indicated by
> the xmpp-server SRV record for "jabber.com." So... does that
> server attempt to deliver it to an XMPP account called
> "JHildebrand@jabber.com"? Does it gateway it to
> "im:JHildebrand@jabber.com"? Does it gateway it to
> "sip:JHildebrand@jabber.com"?
> 
> One answer would be "selection amongst those destinations
> is going to be based on local configuration at the jabber.com
> XMPP server, since it 'owns' the jabber.com namespace." And
> that would work, sort of, and be consistent and simple.
> 
> But it's a very incomplete solution.
> 
> On a grander scale, we need to ask: if you are sitting at an
> XMPP client as "JHildebrand@jabber.com", and want to send an IM
> to "sip:adam@dynamicsoft.com", how do you do that? Can we assume
> that "dynamicsoft.com" is running an XMPP to SIMPLE gateway? Can
> we assume that jabber.com is? Should this be able to work if
> the XMPP to SIMPLE gateway is owned by yet a third domain?
> 
> I think all three solutions need to be possible.
> 
> We've already discussed how the first would work; that's easy.
> The scheme to use in translation is a matter of the destination
> server configuration, potentially selected on a user-by-user
> basis.

I'm not sure I agree on this. As you mention above, even if 
dynamicsoft.com maintains an xmpp to simple gateway, there is no reason 
to expect that you can infer an identifier that makes sense to the xmpp 
side of the gateway from a SIP URI. If dynamicsoft maintains such a 
gateway, then it would make more sense to advertise an xmpp identity in 
addition to the SIP identity, or perhaps an im: URI for both.

It seems to me that an xmpp device, presented with a SIP URI, can do 
nothing intelligent with it beyond submitting it to some xmpp-sip 
gateway that it _already_ knows about, and it cannot use the SIP URI to 
discover that gateway.
> 
> The second would require some indication from your client to your
> server (the host indicated by the xmpp-client SRV record for
> jabber.com) that you want to break out to a SIP network.
> I don't know enough about the formatting of jids to propose something
> ideal, but I would think that using some sort of locally-configured
> prefix would provide that sort of indication (e.g. sending
> an IM to "sip#x3A;adam@dynamicsoft.com" would indicate to your
> server, by the presence of "sip#x3A;", that it should gateway
> to "sip:adam@dynamicsoft.com" using its SIMPLE gateway
> functionality instead of finding the XMPP server for
> dynamicsoft.com). In this case, the proper scheme to use is
> explicitly indicated by the user.
> 
> The third case will require using a jid that explicitly routes
> to the third-party gateway; for example,
> "adam#40;dynamicsoft.com@simple.im-gateway.org". (Ideally, this
> ugliness would be hidden behind some sort of user interface
> construct that allows users to configure their default SIMPLE
> gateway). For this case, the scheme is decided by the gateway
> itself, and will typically be specific to the protocol
> mapping provided by that gateway (i.e. a gateway that 
> translates to SIMPLE will always use sip: or sips:, as
> appropriate).
> 
> At least, that's my two cents on the topic.
> 
> /a
> 
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