Subject: clarification: parameters and brackets

From: Jonathan Rosenberg <[email-masked]>
Date: Sat, 11 Dec 1999 03:12:24 -0500

Folks,

An issue that keeps arising (and came up during the bakeoff), is whether
parameters in the From, To, and Contact header are URI parameters or
header parameters. To clarify, the rule is simple:

1. If there are angle brackets, the parameters inside the angle brackets
are URI parameters. Parameters outside the angle brackets are header
parameters.

2. If there are no angle brackets, all the parameters are HEADER
parameters.

For example:

From: J. Rosenberg <sip:[email-masked];foo=yes>;bar=no

  foo=yes is a URI parameter
  bar=no  is a From parameter

Contact: sip:[email-masked];param=value

  param=value is a Contact parameter.

So, the rules for generating these things are also simple:

1. If the URI has parameters, you must put the URI, and its parameters,
inside angle brackets. Header parameters go outside the angle brackets.

2. If there are no URI parameters, and there is no display name, you
don't need the angle brackets. Any parameters are header parameters.

-Jonathan R.
-- 
Jonathan D. Rosenberg                       200 Executive Drive
Chief Scientist                             Suite 120 
dynamicsoft                                 West Orange, NJ 07052
[email-masked]                     FAX:   (732) 741-4778
http://www.cs.columbia.edu/~jdrosen         PHONE: (732) 741-7244
http://www.dynamicsoft.com

---

From: Henning Schulzrinne <[email-masked]>
Date: Sat, 11 Dec 1999 10:57:32 -0500

Added in Section 6.6:

\begin{changebar}
The \header{Contact}, \header{From} and \header{To} header fields
contains a URL.  If the URL contains a comma, question mark or
semicolon,
the URL {\MUST} be enclosed in angle brackets ($<$ and $>$).  Any URL
parameters are contained within these brackets.  If the URL is not
enclosed in angle brackets, any semicolon-delimited parameters are
header-parameters, not URL parameters.
\end{changebar}

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

---

From: Bobby Sardana <[email-masked]>
Date: Sat, 11 Dec 1999 18:31:34 -0600

Greetings:

Recently, there has been much debate over the SIP grammar and its
variance with what people are implementing. With respect to the SIP
grammar I would like to find out the following:

a. If the SIP protocol (viz., the grammar) can be converted to an
XML DTD then it would become "trivial" for it to parse and without any
variance (fixed DTD).
b. The "map" for headers to "tags" should be straight forward.
c. I am not sure about the "size" of the SIP XML message, but I am
guessing that its impact would be minimal, as to what is being acheived.

It seems that every "new" protocol being developed comes with its own
grammar and its variance. This leads to "proprietary" implementations
because "variance" with grammar is mostly an
implementation/interpretation issue rather than a "concrete" definition.
However, this can be eliminated by picking up a "standard" way of
"defining" essentially (key/value) pairs.

So what I am proposing is that SIP grammar and its implementors would
benefit if the SIP messages can be defined in an XML format since
parsing becomes easy and without any variance. It is understandable that
the SIP designers went with RFC based "text messaging format" but I was
wondering if they considered the XML option. If they did, I would like
to know their findings.

Thanks.

Bobby Sardana.
[email-masked]

---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 13 Dec 1999 00:07:02 -0500

Well, its just plain waaaaaaaaaay to late for something like this. A
complete BNF (which SIP has), has no variance. We've found that peoples
implementations have variance, but thats what bakeoffs are for.

-Jonathan R.