Subject: MMUSIC+PINT joint WG Last Call

From: [email-masked] (Igor Faynberg)
Date: Tue, 24 Aug 1999 12:05:54 -0400

MMUSIC and PINT participants:

Following the advice of Transport Area Directors, this is to announce a 

WG last call on 'draft-antti-telephony-url-09.txt'. The document is
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to be reviewed by both groups on a subject of becoming PROPOSED

STANDARD by September 7,1999.
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Please remember to cross-post the comments to [email-masked]' and
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[email-masked]'. 
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MMUSIC and PINT chairs

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This message came from the IETF PINT Working Group Mailing List.

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From: Dean Willis <[email-masked]>
Date: Mon, 30 Aug 1999 13:18:31 -0500

Lawrence made a key point for me in his discussion of
draft-antti-telephony-url-09.txt.

The draft, as it exists, has no clearly delineated mechanism for supporting
private context. Some of the folks in the office believe this to be a "show
stopper" on acceptance of the current draft. Private context seems to me to
be a key enabler for virtual private dial neworks (VPDNS), or private
numbering plans, and that's a very important application.

In fact, I see two different sorts of private context.

For routing functions in GSTN, we use the dialed-digit string and Nature of
Address (NOA) and Numbering Plan Indicator (NPI) values from ISUP. NOA
includes scopes like "global", "local", and "private", and NPI provides a
code point for differentiating between numbering plans at the same scope
level. To represent this in a URL, we need to have some equivalent function.

At the raw switch level there is no understanding of numbering plans, etc.
All the switches can do is outpulse a dialed digit string onto a trunk which
is part of a trunk group (TG). That is, dialed 8227891 on trunk group 1
might go someplace very different than dialed 8227891 on trunk group 2 of a
given switch. To terminate a call from IP into a switch (without making
another IN call), we need to be able to specify the correct trunk group to
use. It would be nice to be able to represent this in the URL as well.

I had initially considered proposing to use the future-extension syntax of
draft-antti-telephony-url-09.txt to provide for NOA, NPI, and TG. It would
be easy enough to add ";NOA=1;NPI=2345" or ";TG=23456" to a TEL URL this
way.

Perhaps the PINT "private context" notation would be equally useful.

Of course, it would nice if the representation of private context for NOA,
NPI, and TG were standardized, as this would make buying gateways much
easier . . .

Thoughts?

--
Dean Willis

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From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 30 Aug 1999 21:21:33 -0400

> WG last call on 'draft-antti-telephony-url-09.txt'. The document is

Two comments:

1. The draft has a very particular usage for these URL's in mind. The
basic idea is that a user "receiving" this URL would directly dial the
number indicated. In fact, from the document itself:

> These URL schemes are used to direct the user agent to place a call
>    using the telephone network. The network in question may be a

It is for this reason that post dial sequences, for example, make
perfect sense. However, in the usage envisioned in SIP (perhaps others
see it used differently), the tel URL would identify a GSTN subscriber,
be included in the request URI and To field of the INVITE, and sent to
some local proxy. THe proxy, using enum and/or GLP, translates this to a
full SIP URL, so it can route the request. This SIP URL is then placed
in the request URI. In this case, the URI is used to identify the
resource, rather than indicate the means to dial a number to contact it.
In this usage, including things like post dial sequences just doesn't
make sense, since the original user of the tel URL is never actually
going to dial the number. Thus, perhaps some kind of rewording softening
this usage would be nice.

2. One of the things that came up at the last meeting from the DCS
documents was a proposal to add some values to the user parameter in the
SIP URL. Right now, SIP allows user=ip and user=phone. The suggestion
was to add user=lnp-phone and user=private. It seems that two of these
make a lot of sense for the tel URL. In particular, it seems highly
desirable to know whether a tel URL represents a number that has already
been translated, as is the purpose of the user=lnp-phone parameter. This
makes sense when one considers that tel URL's might be used in places
like megaco (?) as well. Its not useful when the application of the tel
URL is restricted to indicating a number a user should dial, but makes
more sense in broader applications like SIP/megaco integration with SS7
(see my point above).

Thanks,
Jonathan R.
-- 
Jonathan D. Rosenberg                       Lucent Technologies
Member of Technical Staff                   101 Crawfords Corner Rd.
High Speed Networks Research                Holmdel, NJ 07733
FAX: (732) 834-5379                         Rm. 4C-526
EMAIL: [email-masked]
URL: http://www.cs.columbia.edu/~jdrosen

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