Subject: [IPTEL] URL Generalization for Portability (was TRIP)

From: S_S_Dinesh/India/[email-masked]
Date: Mon, 8 May 2000 14:10:12 +0530

Jonathan Rosenburg wrote:
> I wonder if we can't think about this problem in more general terms.

yes, please!

> In the SIP model, each proxy owns some piece of the namespace
> (engineering.dynamicsoft.com, for example), and is therefore responsible
> for the definition of the user space (jdrosen@) within that domain.
> Thats why each proxy can, an usually will, perform some kind of URI
> translation independent from other proxies. Our underlying assumption
> was that usernames only have meaning within their domain. For example,
> with sip:[email-masked], only a dynamicsoft.com proxy knows how
> to handle jdrosen. There might be jdrosen's in other domains that aren't
> me. However, in the case of telephone numbers, the proxy that owns the
> domain does not necessarily own the user space. sip:[email-masked],
> for example, uses a user name that is not "owned" by gateway.com, in the
> sense that this name has valid semantics outside of gateway.com. Other
> domains, like wcom.com, would know how to handle this number as well.
> Its possible that we might even see things besides phone numbers as user
> names that are valid across multiple domains. An example is (heaven
> forbid), social security numbers (in the US, at least):

The underlying problem here is differentiating between a phone-number and a
service-name-which-looks-like-a-number. Yes, the user=phone gives a hint on
nature od address, the "+" encodding gives a hint on the scope of address,
but it is still muddy.

There was some discussion of this problem wrt DCS during the November
interim meeting. It was suggested that a cross-domain destination which is
a
phone number could be better represented by a tel: URL than by confusing
the
scope of the user part of a sip: URL. This simplilifies life greatly.

Something like

     INVITE [email-masked]
     To: tel:5551212;trans=lnp?gdbs

could be used to indicate to gateway.carrier.com that premium gateway
service is requested towards the PSTN location identified by telephone
number 5551212, that LNP and GDBS translation have been applied, and that
the phone number is of local scope for the gateway. Incidentally, I think I
just noticed a minor anomaly in the tel-url grammar -- don't see how to
encode more than one future-extension field . . .

--
Dean

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From: S_S_Dinesh/India/[email-masked]
Date: Mon, 8 May 2000 14:10:14 +0530

a
the
>the phone number is of local scope for the gateway.

Since the To: field isn't allowed to change during the transaction,
aren't you going to run into problems if some service along the way
determines that the called number needs to change (as the result of
LNP, 800/900 lookup, etc)?

For example; let's say that one of the services that I have out in the
network is a "reachable from anywhere" speed dialing list. It maps,
for example, "4" as a telephone number to "2145551212". So I launch
an invite to my local proxy:

  INVITE sip:[email-masked] SIP/2.0
  To: tel:4

It goes through my service node:

  INVITE sip:[email-masked] SIP/2.0
  To: tel:4

And he wants to send it on to your gateway for premium service, after
translating the 4 into "2145551212."

It's my interpretation that, under the model you're proposing,
I'd need to send along

  INVITE sip:[email-masked] SIP/2.0
  To: tel:2145551212

But that would break the transaction, since the To: field has changed.

I understand the distinction between destination and service
activation that you're trying to make, but your example seems
unworkable. What am I missing?

--
Adam Roach, Ericsson Inc. |  Ph: +1 972 583 7594 | 1010 E. Arapaho, MS L-04
[email-masked]   | Fax: +1 972 669 0154 | Richardson, TX 75081 USA

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From: S_S_Dinesh/India/[email-masked]
Date: Mon, 8 May 2000 14:10:21 +0530

Adam wrote:
> Dean blurted

Right you are. That should teach me not to come up with examples while
squatting on one of those interminable telco conference calls.

But I still think using a tel: url gives a cleaner semantic than
sip:number@gateway;user=phone.

I was talking with some guys today about scope and context, and I'm
inclined
to think we need the nature of address and numbering plan indicator fields
out of some ISUP variants. Scope appears to be global, local, or private,
with some need to represent local and private within some context like area
code or private numbering plan.

So, for example

tel:+19727294162 is a global number with unspecified context,
tel:9727294162 is a local number
tel:7724162;phone-context=mcivnet34 is a private number with context in the
MCI private numbering plan #34
tel:4512345687724162;phone-context=mciswtrunk is a private number, in
numbering plan 45, relative to switch 123 and trunk group 45678
. . . and whatever other sick private variants one might come up with

--
Dean

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