while I like to take credit for the good things in RFC 2119 (and disclaim the
bad things) - the
term RECOMMENDED (good or bad) comes from RFC 1122
basically I copied the definition section from RFC 1122 for the 1st version of
what became RFC 2119.
(see http://www.sobco.com/ids/draft-bradner-key-words-00.txt)
based on mailing list discussion I produced two revisions of the ID (mostly to
add guidance on usage)
http://www.sobco.com/ids/draft-bradner-key-words-01.txt
and
http://www.sobco.com/ids/draft-bradner-key-words-02.txt
the 02 version is what was approved by the IESG as RFC 2119
all of the above is to say that I can not help in this discussion about the
difference between SHOULD &
RECOMMENDED other than the fact they represent different parts of speech
maybe Bob Braden has an idea since I do find not a usage of RECOMMENDED in the
RFC series before RFC 1122
Scott
On Jun 24, 2013, at 4:38 PM, John C Klensin <john-ietf(_at_)jck(_dot_)com>
wrote:
--On Monday, June 24, 2013 16:28 -0400 Alia Atlas
<akatlas(_at_)gmail(_dot_)com> wrote:
I read SHOULD and RECOMMENDED as different.
SHOULD is how a implementation ought to behave unless there
are special circumstances (deployment, additional
functionality, better idea). MUST says that there are no
circumstances special enough to change the behavior.
RECOMMENDED is closer to a Best Current Practice (BCP); so I
might write "It is RECOMMENDED that the network-converged
timer have a minimum value of 2 seconds." but in 10 years,
maybe it'll only take 2 microseconds - so that'll become a bad
recommendation!
And that, again, is close to the distinction that a reasonable
person might read into 2026. But not into 2119 which appears
(at least to me) to make them fully-substitutable alternatives.
The distinction doesn't make the comments made by Peter, Dave,
or others any less valid. If we told ourselves that readers
should (lower case) infer conformance statements from SHOULD and
applicability ones from RECOMMENDED... well, we would be pretty
delusional.
john