Subject: RE: [Sipping] I-D ACTION:draft-ietf-sipping-e164-00.txt

From: "Christian Huitema" <[email-masked]>
Date: Mon, 3 Dec 2001 11:07:51 -0800

> 	Title		: Resolution of e.164 numbers in SIP
Applications
> 	Author(s)	: B. Campbell
> 	Filename	: draft-ietf-sipping-e164-00.txt
> 	Pages		: 8
> 	Date		: 30-Nov-01
> 
> This document describes how SIP may use the DNS to resolve services
> associated with E.164 numbers
> 
> A URL for this Internet-Draft is:
> http://www.ietf.org/internet-drafts/draft-ietf-sipping-e164-00.txt

The essence of the draft is that if a SIP entity has to forward an
INVITE to a "tel:+12345678901" URL, it should first try to map the
telephone number to an URL using the DNS mapping specified in ENUM.

Well, I think this is a thoroughly bad idea.

Right now, my UA gives me two choice: invite a contact using a sip URL,
or call a phone number. If I want to call a partner, I can look at the
partner business card, and make a conscious decision to either call the
url "[email-masked]" or call the phone number "+1 234 567 8901".
Presumably, I choose the phone number for a reason. Why should a network
element override that choice and redirect the call to the URL instead?

-- Christian Huitema

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---

From: "Dean Willis" <[email-masked]>
Date: Mon, 3 Dec 2001 14:24:11 -0600

Well, maybe there's something not clear here. Or maybe two points -- I
should check the draft and verify that it brings this out.

1) Local policy, such as SIP routing tables or outbound proxy rules, MAY
override the "look it up in DNS" approach normally used for resolving a SIP
URL. This means if you really want to send a call to the PSTN via your own
choice of routes, you can.

2) Ok, you've got this SIP phone in your hand, and you want to call a phone
number off of somebody's business card. You don't actually know whether that
phone number will be routed to a SIP phone or a PSTN phone before it's all
over with. You have two choices: 1: force the call through a gateway to
PSTN, which might send it through the called party's gateway and back onto
the Internet, or 2: Treat the number as a URI and see if DNS knows how to
find a URL for a node willing to claim responsibility for handling the
next-hop routing.

Most phones (or local outbound proxies) configured with gateway routes will
actually default to sending "phone numbers" to a default gateway to PSTN.
Only in the presence of additional information, such as phone-routes, TRIP
info, or DNS, will they do something different. So basically it boils down
as to how your phone and the various network elements are configured, what
least-cost routing policies are being applied, and what dynamic information
about the network is available to the decision-making nodes.

Does this begin to address your concern? How can we make this more clear in
the draft?

--
Dean Willis