Re: [secdir] secdir review of draft-ietf-httpbis-p4-conditional-19

Mark Nottingham <> Mon, 09 July 2012 00:52 UTC

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From: Mark Nottingham <>
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Date: Mon, 9 Jul 2012 10:52:37 +1000
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To: Klaas Wierenga <>
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Subject: Re: [secdir] secdir review of draft-ietf-httpbis-p4-conditional-19
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On 06/07/2012, at 7:11 PM, Klaas Wierenga wrote:
>>> "ought to" is not very normative. Why not make it MUST or SHOULD?
>> We've used that terminology when we want to give implementation advice, but cannot impose a new RFC2119-level requirement, because it would make existing implementations non-conformant (as per our charter).
> So would that not be a good case for SHOULD with perhaps some explanation along the above lines why it isn't a MUST?

No, because that still affects conformance (saying "you SHOULD do this unless you're an old implementation is awkward and hard to enforce; it also encourages implementations not to update themselves).

>>> 4.1 p17, Not modified, second paragraph
>>> A 304 response..... isn't this a fine case of a SHOULD rather than a
>>> MUST? Or perhaps "A 304 response MUST include a Date header field,
>>> unless the origin server.... , in that case a Date header field MUST
>>> NOT be provided", and what actually does "reasonable approximation" mean?
>> I'm not sure what you're concerned about here; it's a MUST requirement because it's important for interop.
> it is really just for clarity, I had a bit of trouble parsing, rereading I think my remark about SHOULD probably doesn't make sense. Still, I read it like "you MUST do A unless condition B applies in which you MUST NOT do A", I just suggested rephrasing, perhaps to:
> "If condition B applies you MUST do A, if condition B does NOT apply you MUST NOT do A" 

OK, I'll pass that on to the editors.

Thanks again,

Mark Nottingham