Subject: Re: [Sipping] draft-ietf-sipping-e164-00.txt

From: [email-masked]
Date: Mon, 3 Dec 2001 19:55:18 EST

My comments on draft-ietf-sipping-e164-00:

Nits: There are a number of places in this draft where there is a paragraph 
with extra indentation, some of which appear at first as if they intend to 
indicate that the indented paragraph is quoted from some other place such as 
RFC  2916. Unless there is a specific reason for this indentation, which 
needs to be made clear, this extra indentation needs to be removed.

Confusion is caused in Section 4 by describing sip URLs as containing e.164 
numbers and the example:

    sip:[email-masked];user=phone

In E.123 (referenced in E.164), + indicates (in written phone numbers) that 
an international prefix is required. It therefore indicates that what follows 
is a standard international phone number, i.e., begins with the country code 
and is globally unique (or "globally-scoped").

After saying that "both examples describe a globally-scoped telephone 
number", the draft goes on, correctly, to say that this representation of the 
phone number for SIP is "locally-scoped", since it contains a host name, and 
that a UAC "should not use a DNS query to resolve a number". It is true that 
the number can only have a meaning within the confines defined by that host. 
(It may very well be the same string as a globally-scoped phone number or a 
portion of it without the country code, but as far as we are concerned, that 
is coincidental. Only the designated host knows how to interpret the number. 
It could be a private number that just happens to look like a global e.164 
number.)

It would seem that the example of a telephone number for sip:... in 
draft-ieft-sipping-e164 should not include the "+" before the number. In 
fact, the part before the @ symbol could consist of any legitimate string of 
characters known to the host, certainly including letters.

The statement that "both examples describe a globally-scoped telephone number 
(i.e. E.164 number)" should be worded to say:

    The first example describes a globally-scoped telephone number (i.e., 
E.164 number). The second example describes a telephone number which is 
locally-scoped within the domain of the designated host. It may be a private 
number or a portion of the E.164 number or it may be equivalent to the E.164 
number.

Further, the statement in Section 6 "If the e.164 number was received [by a 
proxy] as part of a sip URL..." causes confusion, since, by definition, the 
sip URL does not contain an "e.164" number, or at least, it is not known that 
it does. If anything, the statement should be something like the following to 
remove the reference to e.164:

    If the Proxy receives a sip URL and the domain portion does not refer to 
a domain owned ... 

In Section 7, it is unknown what the references to "DID call" and "post-dial 
digit strings" mean. For "DID", the gateway (and everything else) just sees a 
normal e.164 number. (The term "DID" should disappear from the descriptions. 
It really only refers to the signaling arrangement between central offices 
and PBXs.) For "post-dial" cases, the post-dial digits are never part of the 
e.164 number.

Mike Pierce
Artel

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---

From: Ben Campbell <[email-masked]>
Date: 06 Dec 2001 16:43:34 -0600

Hi,

Just to make sure people realize, since there was quite a bit of
feedback over this draft submission, that this was not a new draft.
Rather, it is a minor update incorporating feedback from a working group
last call. It became a 00 draft again because was renamed to reflect its
status as a SIPPING wg item. Since most of the new feedback seems not to
concern changes since the last called version, I am not quite sure how
to proceed. Perhaps the chairs would like to comment? (This is not to
pick on Mike; there were several people who responsed. More in fact than
did in the actual last call.)

In any case, my responses to your actual comments are inline:

> needs to be made clear, this extra indentation needs to be removed.

Usually that is intended to reflect additional descriptive, explanatory
text, or otherwise non-normative text. It is a common practice in I-Ds.
Of course, it is always possible that there is a formatting problem that
does not render on my computer, so if you see a specific location that
does not reflect this usage, please let me know.

> It could be a private number that just happens to look like a global e.164 

It seems to me you are confusing the idea of phone number scope with
domain name scope--they are not the same thing. For example,
"sip:[email-masked];user=phone" would be interpreted
differently depending on whether the element doing said interpretation
was "example.com" or something else. An element that is not responsible
for the "example.com" domain should not attempt to interpret the user
part of the URL. It doesn't matter whether the user part is
"+1234567890" or "dontreadme". Only an element responsible for
"example.com" has any business making that interpretation.

Now, if the element is indeed responsible for example.com, it gets to
interpret the user part. In this example, we have hinted to example.com
that we intended the user part to be a phone number, and by using the
"+" prefix, we have told example.com that the number is globally
routable.
> characters known to the host, certainly including letters.
See above.

>     If the Proxy receives a sip URL and the domain portion does not refer to 

The second version may be simpler, but it seems to make normative
statements about SIP behavior that is beyond the scope of this draft.

> and PBXs.) For "post-dial" cases, the post-dial digits are never part of the 

The terms were used as examples only in an explanatory (indented)
paragraph, and were not intended to be normative text. Would it make
things clearer to add a "For example,..." phrase to the offending
sentence?

Thanks!

Ben.