Subject: RE: [SIP] SIP URL telephone-subscriber syntax.

From: [email-masked]
Date: Wed, 5 Jul 2000 09:24:01 +0300

Hello,

Problems seem to crop up in <quoted-string> which was included as to be
"compatible" with the RFC 2543. I agree that it should be removed in future
versions of RFC 2806. 

As <"> and "%" are not allowed characters in itself, the issue was mentioned
in RFC 2806 section 1.2, meaning that all those special characters must be
escaped with the %hex notation before putting them in the URL, resulting in
the double escaping you discussed. This is hairy and IMHO it is a very good
idea to get rid of the <quoted-string> altogether. Sadly, your email about
your plans to dump <quoted-string> from SIP URLs came a bit too late to be
taken into account when writing the first version of RFC 2806.

So, my recommendation for tel: URLs is the same: do not use it, it will
become deprecated.

> Modified spec roughly accordingly. Note that RFC 2806 has a mistake in
> that % can never appear as itself. Same for %22 (") and %23 
> (#), %3c (<)
> and %3e (>), according to RFC 2396.

Are you referring to <private-prefix> here?

Yes, this is mentioned in RFC 2806 section 1.2. All of those chars must be
escaped before using them in a tel: URL. This is also said in the BNF
comments. The original reason why I listed the characters exclipitly in
<private-prefix> was that there were some characters that should not be
present as the first character of the prefix, to make it distinguishable
from <global-network-prefix> and <local-network-prefix> after unescaping. 

(I do not subscribe to SIP mailing list at the moment, so please Cc: me on
replies - thanks.)

Antti

--
Antti Vähä-Sipilä / Nokia Mobile Phones
My views and opinions are not necessarily those of my employer.
Send personal email to [email-masked] only. http://www.iki.fi/avs/

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---

From: Henning Schulzrinne <[email-masked]>
Date: Wed, 05 Jul 2000 15:33:52 -0400

> from <global-network-prefix> and <local-network-prefix> after unescaping.

However, this notation is very confusing and at variance with RFC 2396.
Characters that can't appear by themselves (without escaping) should
just be listed as "escaped", not be listed as octets. If there are
certain characters that somehow designate number ranges, this is not
really a BNF issue. (Whether this is a good idea is a separate topic; in
my view, relying on naming rules that omit characters, but otherwise
look identical, to determine semantics is likely to be confusing. I
think it would be much cleaner to designate some special character as a
private prefix, e.g., *)

-- 
Henning Schulzrinne   http://www.cs.columbia.edu/~hgs