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Re: Use of LWSP in ABNF -- consensus call

2007-05-16 05:32:43
On Mon, 14 May 2007, Lisa Dusseault wrote:
The IESG reviewed <http://www.ietf.org/internet-drafts/draft-crocker-rfc4234bis-00.txt> for publication as Internet Standard and would like to know if there is consensus to recommend against the use of LWSP in future specifications, as it has caused problems recently in DKIM and could cause problems in other places.

LWSP was one of the factors in the SASL WG's abandoning of the DIGEST-MD5 revision. To be precise, the complexity inherent in the 822-style n#rule syntax (the emulation of which in modern ABNF uses LWSP) was found to be a source of implementation errors and interoperability issues. Part of the discussion can be seen at:
   http://www.imc.org/ietf-sasl/mail-archive/msg02752.html

While I don't think removing LWSP from the ABNF RFC is good idea, adding a comment to its definition in section B.1 that warns protocol designers to consider carefully whether they really need or want "LWSP" instead of "*WSP" does seem appropriate. Calling out that LWSP permits lines containing just whitespace may help drive home the issue.


Philip Guenther
Sendmail, Inc

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