Re: EPP Poll 'msgid' attribute

Andrew Sullivan <[email protected]>
Newsgroups gmane.ietf.provreg
Message-ID <[email protected]>
On Mon, Oct 31, 2011 at 11:33:19AM +0200, Mike O'Connell wrote:
> 
> We're looking at implementing a selectable poll message process where the op='req' can specify the clTRID as the 'msgid' attribute to retrieve any unacked responses associated with that client identifier.
> 
> Has anyone implemented anything like this? What are the thoughts regarding this?

I argued for altering the way poll worked to do something quite like
this, about the time that EPP went through one of the standards levels
(I think from proposed to draft).  I outlined the suggestion in a
long-expired I-D that is still available:
http://tools.ietf.org/id/draft-sullivan-epp-experience-00.txt.  See
sections 3.4 and 4.2.

I strongly recommend you not try to shoehorn this functionality into
the existing poll queue mechanism.  The existing mechanism is quite
clearly FIFO, and if you try to manage it differently while using the
same syntax, you not only produce quite different behaviour with the
same protocol; you'll also find that you don't have enough primitives
to manage the queue correctly, and messages will get lost.  Anyway,
you'll be in flagrant violation of section 2.9.2.3 of RFC 5730: "a
successful response to a <poll> command MUST return the first message
from the message queue."  If conformance is important to you for
contractual reasons, then you just can't do this.

When I argued in favour of the approach to the poll queue I outlined
in that I-D, Scott Hollenbeck pointed out (correctly) that you could
do it with an extension anyway.  That's what I'd recommend.  Afilias
never did undertake that work, however, because a colleague of mine in
the development department decided instead that the passage, "Service
messages SHOULD be created for passive clients affected by an action
on an object," used the ordinary English meaning of SHOULD and not the
RFC 2119 one.  (Note that in RFC 3730, that SHOULD was a MUST, but I
still don't see how the SHOULD gets one off the hook in case it's
merely convenient.)

Best,

A

-- 
Andrew Sullivan
[email protected]

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