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

From: "Fairlie-Cuninghame, Robert" <[email-masked]>
Date: Fri, 7 Jul 2000 07:38:14 -0700

Gethin,
 
> I do see problems with the new method you suggested.  For example, the
> suggested characters & and $ are valid in their own right in the tel
> url (unless i've read it wrong again :) ) so we would need to 
> translate
> or do something with all occurances of them.  The same problem occurs
> with `/' being used in the longer escaped string.

The & and $ are reserved characters (RFC2396) in the tel: private prefix and
future extension paramter names and values (therefore must be quoted if they
appear in these fields) _and_ they are not used in the tel: syntax as
meta-characters (as far as I can see). Therefore, these two characters
should never appear in a tel:. The two characters are also unreserved in the
sip: user part(ie don't have to be escaped). [Forget about the '/' character
- I was looking at the wrong unreserved list for that one.]

John Rosenburg says this merely cascades the problem - I disagree.
There is a difference between escaping the tel: URL and merely escaping the
whole sip: URL. In the former case the user part is an actually an
interpreted/embedded field, not just an opaque string (as would be the case
if someone was to escape the URL). 
For instance, if someone else was to escape the whole sip URL [per RFC2396]
_without_ recursively escaping the URL how would you tell whether

sip:host%3bparameter=value%3bhidden

referred to a parameter with value "value;hiddden" or is "hidden" a separate
parameter?

So my point is: if you don't do recursive escaping of the SIP URL then the
telephone-suscriber part is the least of your worries (and if you do
recursive escaping then this doesn't cause a problem). So I don't see how
this cascades the problem.

Cheers,

Robert.

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---

From: Henning Schulzrinne <[email-masked]>
Date: Fri, 07 Jul 2000 10:44:14 -0400

Frankly, I thought we solved this problem already several days ago? Why
invent a kludge that no other URL scheme is using to solve a non-issue?
-- 
Henning Schulzrinne   http://www.cs.columbia.edu/~hgs