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 <[EMAIL PROTECTED]> 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
>
>
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