Paul & Dale:
While section 5.2 of RFC 3261 says that the To URI must contain a SIP or
SIPS URI, RFC 3261 was published before the newer tel URI RFC 3966
(which obsoletes RFC 2806 which is referred to by RFC 3261).
In section 9 of the newer RFC 3966 (titled "Use ot 'tel' URIs with SIP
(Informative)") it says that:
"SIP can use the 'tel' URI anywhere a URI is allowed, for example as
a Request-URI, along with 'sip' and 'sips' URIs."
While this section of RFC 3966 is only informative it does bring into
doubt whether the Request-URI and To URI in a REGISTER request can only
contain sip or sips URI as Paul stated below.
Personally, I think that this informative remark is not meant to apply
to REGISTER requests but this section certainly does not make this
clear.
Whether the To and Request URIs in a REGISTER request can contain a tel
URI brings into question the purpose of the tel URI. A colleague of mine
would like that a single tel URI:
1. is an AOR URI to which locations can be registered using
REGISTER request. The domain of the location service for the
Request URI presumably comes from the tel URI's domain
phone-context, which must be present, and hence the tel URI must
be a local number.
2. is an AOR URI to which other SIP UAs can send INVITE's. This
assumes that the tel URI has a domain phone-context as well so
that the UA can route the tel URI to the AOR's location service.
3. contains a telephone number (the telephone-subscriber in RFC
3966) so that a PSTN caller can also call the AOR. This assumes
that the PSTN number is routed to a PSTN to SIP gateway which is
configured with the domain of the location service associated
with the tel URI. However, because the tel URI is a local and
not a global number, the number does not contain a leading "+".
This may present a problem for the PSTN caller. However, since
PSTN callers don't use the tel directly, they could be given the
same number but with a leading "+".
The objective is that a subscriber can have a single identity: a tel URI
for the SIP domain which contains the same telephone number which is
their identity in the PSTN telephone network.
I'm not sure that this is the intent of the tel URI especially given
that the telephone number must be a local number and not a global one.
My understanding is it is just a way of representing a telephone number
so that e.g. a SIP UA can call the number by using an appropriate
gateway: a SIP to PSTN gateway if the number is global or an
proxy/gateway identified by the tel URI's phone-context if the number is
local.
Comments on this which include references to relevant RFCs would be
appreciated.
Jolan
On Mon Nov 28 19:51:19 EST 2005 Paul Kyzivat wrote:
> I pretty much agree with Dale.
>
> It would be good if people would RTFM before posting questions like this
> one. Section 5.2 of 3261 says:
>
> Request-URI: The Request-URI names the domain of the location
> service for which the registration is meant (for example,
> "sip:chicago.com"). The "userinfo" and "@" components of the
> SIP URI MUST NOT be present.
>
> To: The To header field contains the address of record whose
> registration is to be created, queried, or modified. The To
> header field and the Request-URI field typically differ, as
> the former contains a user name. This address-of-record MUST
> be a SIP URI or SIPS URI.
>
> This makes it pretty clear that the R-URI and To-URI of register MUST be
> sip or sips.
>
> I do have some sympathy though. I think it *ought* to be ok to use a tel
> uri in the To: header. Of course that won't by itself be enough to get
> the domain to assume responsibility for the phone number - that would
> have to already have been established somehow. But it would provide a
> way for a UA to say it wants to accept calls to that number that happen
> to reach the domain.
>
> Paul
>
> Dale R. Worley wrote:
> > On Mon, 2005-11-28 at 02:54 -0800, Litty Preeth wrote:
> >
> >>Suppose there is a sip soft-phone with a tel URI say "tel:
> >>+358-555-1234567". If i want to register that phone to a SIP
> >>registrar handling the domain say "xyz.com" then what would be the
> >>sheme of the request uri of that REGISTER request - sip or tel ? I
> >>mean would it be tel:xyz.com or sip:xyz.com
> >
> >
> > Maybe I'm not seeing how you want to use SIP, but I think such a request
> > would be meaningless. A REGISTER is for informing the proxy that
> > handles a SIP domain, e.g., "sip:... at example.com" that requests for
> > <sip:foo at example.com>" should be routed to <sip:foo at 10.1.2.3>. A
> > REGISTER can never provide information about how to handle requests for
> > a tel: URI.
> >
> > Perhaps people have started building registrars/proxies that route tel:
> > URIs and use REGISTER messages, but that is an extension of RFC 3261
> > that I've never heard of.
> >
> > Dale
> >
> >
> > _______________________________________________
> > Sip-implementors mailing list
> > Sip-implementors at cs.columbia.edu
> > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
> >
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