Subject: [Sipping] RE: [Sip] New I-D on usage of phone numbers in SIP [DO NOT REPLY! ]

From: "Elwell, John" <[email-masked]>
Date: Thu, 02 Nov 2006 13:49:31 +0000

Jonathan,

Some good stuff in here.
 
> The document proposes a framework and architecture for the usage of 
> phone numbers with SIP. It tries to answer questions like the 
> difference 
> between a tel URI and SIP URI with user=phone, when to use each, what 
> the meaning of concepts like LNP and freephone are in a 
> pure-SIP world, 
> the architectural role of ENUM, and impacts on PSTN interoperability, 
> and so on.

I am not sure about classing a SIP URI as an address. As you say later, the
more important meaning of the domain part is as an identifier of the owner
of the namespace to which the user part belongs. It says nothing about where
this can be found (unless it is in the form of an IP address). It requires a
DNS look-up to obtain an address (IP address). Likewise, at least when used
as an AoR, the entire SIP URI (including the user part) identifies a
resource (a user) and does not say where that resource is to be found. It
requires a location server look-up to determine this. So in many respects I
think a SIP URI is much more like a name. I could put it on my business
card, in the same way I would put a phone number on my business card.

However, I do realise that the rest of the document is predicated on this
distinction between name and address, so this discrimination is useful even
if the terms aren't quite right. Unfortunately I don't have a proposal.

John

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From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 06 Nov 2006 17:46:53 -0500

> Some good stuff in here.

Thanks!

> DNS look-up to obtain an address (IP address).

Its an address in that it is bound to a specific domain and requests to 
it will get routed to proxies with particular IP addresses, learned 
through the DNS.

  Likewise, at least when used
> resource (a user) and does not say where that resource is to be found.

Sure it does; it says it is found in the domain indicated in the RHS of 
the URI. I like drawing analogies to the postal service; this would be 
equivalent to saying something like "Joe Smith of London, England". It 
absolutely an address, in that it points to something through its 
location (London). Its just not very specific, in that you need to do 
some further work once you get to London.

> It

Sure; both are valuable on business cards. That doesn't make them both 
names.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 06 Nov 2006 17:46:53 -0500

Thanks!

-Jonathan R.