RE: [Sip] SIPit21: BNF future-proofing problem?

This would mean a large change to existing parsers and formatters. And
also, the "escaping" and "unescaping" overheads.

Changing the header-value BNF may be more acceptable?

Regards
Satya T

-----Original Message-----
From: Christer Holmberg [mailto:christer.holmberg@ericsson.com] 
Sent: Wednesday, November 21, 2007 11:13 PM
To: Christer Holmberg; Robert Sparks
Cc: sip List
Subject: RE: [Sip] SIPit21: BNF future-proofing problem?

Hi,

Another alternative would be to define an escaping mechanism for
quoted-strings in SIP messages, and require all characters not allowed
by the header-value ABNF to be escaped.

Regards,

Christer 

________________________________

From: Christer Holmberg [mailto:christer.holmberg@ericsson.com]
Sent: Wed 21/11/2007 15:33
To: Robert Sparks
Cc: sip List
Subject: RE: [Sip] SIPit21: BNF future-proofing problem?

Hi,

>So to restate the problem that was reported:
>
>Right now, extension-header does not allow a new header that contains a

>quoted-string.
>
>We have defined extensions (and are likely to define new
>ones) that use quoted-string (anything that uses name-addr for 
>instance).
>
>This inconsistency has caused interoperability problems in real 
>implementations.
>
>My original note was to suggest that we change extension-header to 
>actually allow the headers we're going to define.
>
>Christer's response could be read as a proposal to change
>quoted- string to achieve the same goal.

Yes.

Unless someone can show a use-case where the x00-x20 characters would be
needed, for backward compability reasons I think it's better to restrict
quoted-string than to extend extension-header.

Regards,

Christer

> > Hi,
> >
> > I am still a little unclear what Robert is proposing, but is there 
> > really a need to be able to use characters between x00 and
> x20 in SIP
> > messages? Characters between x21 and x7F, and between x80
> and xBF, are
> > ok since they are covered by TEXT-UTF8char and UTF8-CONT.
> >
> > Regards,
> >
> > Christer
> >
> >
> > ________________________________
> >
> >     From: Hisham Khartabil [mailto:hisham.khartabil@gmail.com]
> >     Sent: 21. marraskuuta 2007 7:30
> >     To: Robert Sparks
> >     Cc: sip List
> >     Subject: Re: [Sip] SIPit21: BNF future-proofing problem?
> >    
> >    
> >     I think I did misread Robert's original email. I thought header 
> > values having quoted strings are currently not allowed and Robert 
> > wanted to change RFC2822. Now I realise that you can have
> header field
> > values with quoted string. Therefore I support the correction that 
> > Robert is proposing.
> >    
> >     Hisham
> >    
> >    
> >     On 21/11/2007, Hisham Khartabil <hisham.khartabil@gmail.com>
> > wrote:
> >
> >             This is a big change if we do adopt it. It will
> cause a lot of
> > problem to parsers that handle extenion headers today and is not 
> > backwards compatible. Why isn't the extension header as is defined 
> > today not sufficient?
> >                            
> >             Hisham
> >            
> >            
> >                                             On 20/11/2007, Robert 
> > Sparks <rjsparks@nostrum.com > wrote:
> >
> >                     The BNF in 3261 says the following:
> >                    
> >                     extension-header  =  header-name HCOLON
> header-value
> >                     header-value      =  *(TEXT-UTF8char / UTF8-CONT
> > / LWS)
> >                    
> >                     This is intended to be the catch-all
> field for all future
> > extensions
> >                     - older parsers working against this
> BNF shouldn't barf
> >                     when we introduce a new header field.
> >                    
> >                     Now, we may have new fields in the
> future that look like:
> >                    
> >                     NewHeader = new-header-name HCOLON quoted-string
> >                    
> >                     And down inside quoted-string, we get:
> >                    
> >                           quoted-string  =  SWS DQUOTE
> *(qdtext / quoted-pair ) DQUOTE
> >                           qdtext         =  LWS / %x21 / %x23-5B /
> > %x5D-7E
> >                                             / UTF8-NONASCII
> >                           quoted-pair  =  "\" (%x00-09 / %x0B-0C
> >                                            / %x0E-7F)
> >                    
> >                     So, for instance, we could have inside
> a quoted string the 2 byte
> >                     sequence \ NULL
> >                    
> >                     This does not parse against
> header-value above...
> >                    
> >                     Is this a problem? Some of the SIPit21
> participants argued that it
> > is.
> >                    
> >                     The projects I've been involved in
> don't parse unknown headers and
> >                     the stacks will just hand up an
> unparsed bucket of bits (the only
> > rules
> >                     used are those necessary to identify
> the next header-field
> > starting).
> >                    
> >                     Would it be worth the effort to make
> the BNF reflect that rather
> > than
> >                     continuing with the incongruity that we
> currently specify?
> >                    
> >                     RjS
> >                    
> >                    
> >                     _______________________________________________
> >                     Sip mailing list 
> > https://www1.ietf.org/mailman/listinfo/sip
> > <https://www1.ietf.org/mailman/listinfo/sip>
> >                     This list is for NEW development of the
> core SIP Protocol
> >                     Use sip-implementors@cs.columbia.edu
> for questions on current sip
> >                     Use sipping@ietf.org for new
> developments on the application of sip
> >                    
> >
> >
> >            
>
>

_______________________________________________
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This list is for NEW development of the core SIP Protocol Use
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_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol Use
sip-implementors@cs.columbia.edu for questions on current sip Use
sipping@ietf.org for new developments on the application of sip

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use sip-implementors@cs.columbia.edu for questions on current sip
Use sipping@ietf.org for new developments on the application of sip