Re: [AVT] draft-ietf-avt-rtp-vorbis: configuration-uri

[Peter Saint-Andre <stpeter at jabber.org>]

On Wed, Jun 13, 2007 at 02:42:38AM +0200, Luca Barbato wrote:
> Peter Saint-Andre wrote:
> > In draft-ietf-avt-rtp-vorbis-05 we find:
> > 
> >       configuration-uri:  the URI of the configuration headers in case
> >          of out of band transmission.  In the form of
> >          "protocol://path/to/resource/".
> > 
> > This assumes that URIs have a certain structure and that there is a
> > resource with a certain media type available at the URI. While that is
> > true of many URI schemes (e.g., http: and rtsp:), it is not true of
> > other URI schemes (e.g., mailto: and xmpp:). Unless you have a good
> > reason for thinking that a configuration-uri must be of the form you
> > specify, I think it would be best to generalize the format so that any
> > URI that conforms to RFC 3986 can be used.
> 
> The rationale for picking this restricted form is just simplicity, I can
> relax the spec so it is RECOMMENDED to structure the configuration-uri
> this way.

That's fine with me.

> > As an example, we might define a way to retrieve configuration headers
> > via XMPP, for which the URI might be something like this:
> > 
> > xmpp:user at example.com?config;header=resource
> 
> I see a problem
> 
> > 
> > Do you mean that if the URI ends with a trailing slash, then the method
> > in use is "simple configuration packet" but if the URI does not end in a
> > trailing slash then the method in use is "multiple packets aggregated in
> > a single stream"?
> 
> Yes.
> 
> > Again, this seems limited to a specific URI structure,
> > since in the XMPP example above we might do something like the following
> > for multiple aggregated packets:
> > 
> > xmpp:user at example.com?config;header=resource;aggregate=aggregated.bz2;hash=sha1hash
> 
> ";" has a particular use in sdp, this string cannot be delivered in sdp.
> 
> What about mapping the former to
> 
> xmpp://user at example.com/aggregated.bz2!sha1hash

xmpp://user at example.com means "authenticate as user at example.com". Also
XMP URIs are not "hierarchical" in the way that HTTP URIs are. So
xmpp:user at example.com/aggregated.bz2!sha1hash doesn't mean what you
think it means -- i.e., it doesn't mean "obtain the resource (file)
'aggregated.bz2' with SHA1 hash 'sha1hash' from the XMPP entity 
identified by user at example.com". XMPP URIs are structured differently
(though they still conform to RFC 3986).

> and let the application convert it to the format xmpp expect?

That's what XMPP URIs do -- we don't use them natively. But IMHO the
original URI should conform to RFC 4622.

> Probably xmpp configuration uri would be used just in conjunction with
> Jingle and never with sdp so the issue won't happen.

Right.

As long as the text is changed to say that the format you describe is
recommmended, I'm fine (because we would specify the XMPP URI format in
a different spec anyway).

Peter

-- 
Peter Saint-Andre
XMPP Standards Foundation
http://www.xmpp.org/xsf/people/stpeter.shtml


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