RFC 3261 made the @ and after it optional in ABNF.  So a strict parser to 3261 
must allow it.  In fact we've seen plenty of Call-ID's without it, from some 
very common equipment.
We just can't change the BNF because a strict parser parsing to this new draft 
would not accept 3261 call-id's.
-hadriel


________________________________
From: [email protected] [mailto:[email protected]] On Behalf Of Venkatesh
Sent: Wednesday, March 25, 2009 5:35 PM
To: Jonathan Rosenberg
Cc: IETF SIP List
Subject: Re: [Sip] The problem with draft-kaplan-sip-secure-call-id-00

Hello:

I am not sure that this alone will fix the problem in totality. If I were to 
use the reverse analogy i.e. what if a UA that conforms to this specification 
offers the request to a "aggressive parsing" UA that is only compliant with RFC 
3261?

If we are not planning on changing the BNF, I am wondering if this draft should 
simply say that the string after the "@" sign MUST NOT include a domain name, 
host address, MAC....? Or if this is ambiguous, simply say that the UA MUST 
generate *another* cryptographic identifier to be placed after the @ sign?

Thanks,
Venkatesh
On Wed, Mar 25, 2009 at 1:51 PM, Jonathan Rosenberg 
<[email protected]<mailto:[email protected]>> wrote:
I didnt get a chance to say this at the mike.

You *cannot* change the BNF for the call-id. If you did, you might end up with 
the following problem:

A new UA gets built, compliant to this update. It is one of these 'aggressive 
parsing' UAs. It rejects any message which is not compliant to the BNF. An 
older, normal RFC-3261 compliant UA sends a call-id which includes the @-sign.

According to the BNF of this updated 3261, and based on the strictness of this 
aggressive-parsing UAs, it rejects that request as non-compliant.

As such, you need to keep the BNF, but change the normative language such that 
an endpoint MUST NOT include the [@ host] but MUST be prepared to receive it.

-Jonathan R.

--
Jonathan D. Rosenberg, Ph.D.                   111 Wood Avenue South
Cisco Fellow                                   Iselin, NJ 08830
Cisco, Voice Technology Group
[email protected]<mailto:[email protected]>
http://www.jdrosen.net                         PHONE: (408) 902-3084
http://www.cisco.com
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