> Of late, I have been referring to the syntax in RFC 2068 which is
> essentially RFC 822 with a few improvments.
>> Which should we use?
I recommend using draft-ietf-drums-abnf-*.txt.
The DRUMS ABNF document is being separated from the RFC 822bis
specification precisely so that the ABNF specification can be
referenced by other specifications that want to use it. If it's not
adequate for IPP, I'm sure the ABNF authors would want to know why.
(But wait until version -03. The DRUMS WG meeting last Friday agreed
on some important changes which make things a lot cleaner.)