Subject: Line Folding + Grammar strictiness {RESEND}

From: [email-masked]
Date: Tue, 23 Nov 1999 16:09:30 +0530

Hi,
According to the specification of line folding, a header may be broken into
multiple lines by inseting a LWS in the next line.
so
<hdr>:<token1> <token2>
     <token3>

is allowed.

However, the spec says that Headers itself should not have leading white
spaces.

However, Ive seen certain examples where many headers beging with an LWS.
Is this something that is allowed ? If this is so, it makes differentiating
between a Header continuation and a new Header more difficult.

Please refer to definition of a tag-param

tag-param= "tag=" UUID
UUID = 1*(hex|'-')

However, in one of the test messages of 2nd bakeoff (test1.txt) , there was
a
test which had a

tag=12231423424n
and
tag=98ashd<something>

None of the above confirm to the grammar specified, so why should a parser
allow it ?

Just wondering how strictly the tests are following the grammar - if not,
why define a fixed rule set in the first place ?

Regds
Arjun

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From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 24 Nov 1999 15:46:25 -0500

> between a Header continuation and a new Header more difficult.

Its not allowed. You can't have leading white space in front of the
header. I thought the spec said this.

> None of the above confirm to the grammar specified, so why should a parser

There is a general guideline about being forgiving on reception, but you
are correct. Really, tag should just be a token, same with Call-ID. The
semantics should say that they must be unique, and that a suggestion is
to use a UUID or something of the form id@host, but we should not impose
that at a syntactic level. 

-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: Wed, 24 Nov 1999 18:06:15 -0500

Jonathan Rosenberg wrote:

> that at a syntactic level.

For the call-id, I disagree. This should be specified, since any other
form is invalid. We want to specify a user@host form to decrease the
likelihood of collisions. (One reason we might want to reconsider the
Call-ID form is to avoid revealing host information, but then we better
come up with a reasonable alternative.)

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

---

From: Henning Schulzrinne <[email-masked]>
Date: Thu, 25 Nov 1999 08:33:19 -0500

Lars Berggren wrote:

> 
> There are also cases when the host part of the user@host form causes
> problems when creating a globally unique id, e.g. for hosts on LANs without
> globally unique hostnames or ip-addresses.
> 
> However if such hosts is to be reached globally I believe they must have
> some globally reachable sip-url (where the host part indicates some kind
> of nat-sip-proxy).
> Thus, I think it might be a good idea that clients without globally unique
> ip-addresses constructs its Call-ID from their globally reachable sip-url
> or some other unique token (given by the sysadmin) that can be configured
> into the client.
> 
> For example:
> Call-ID: [email-masked];tag=12921838
> or
> Call-ID:[email-masked]
> (the latter following the current rfc stated syntax of Call-ID)
> 
> What about this? Is it something to add to the firewall-friendly
> implementation requirements in appendix A of the rfc?
> 

I'm not sure that making the Call-ID more complicated is all that
helpful, since it is after all (mostly) an opaque identifier. The local
part is supposed to be globally unique all by itself, with the host part
adding a layer of "insurance" that makes it safe to use mainly
time-based identifiers as the local part.

For those with non-globally-unique addresses, there is a potential
problem only if they use a 10.x.x.x address. (Even in that case, the
likelihood of bad consequences is probably small.) Otherwise, if they
use a host name, that host is not likely to be pingable or resolvable
via DNS, but probably unique.

Thus, I would suggest leaving things as is. It doesn't seem to be broken
and I'm reluctant to add complexity if I can help it.

Henning

---

From: Lars Berggren <[email-masked]>
Date: Thu, 25 Nov 1999 09:48:55 +0100 (CET)

For example:

/Lars

Lars Berggren       <[email-masked]>
Intertex Data AB    tel: +46-8-6282828
Sundbyberg, Sweden  fax: +46-8-6286414