Re: [storm] iSCSI version descriptors

"David Harrington" <ietfdbh@comcast.net> Wed, 08 December 2010 15:00 UTC

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From: "David Harrington" <ietfdbh@comcast.net>
To: <david.black@emc.com>, <paul_koning@Dell.com>
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Date: Wed, 8 Dec 2010 10:00:49 -0500
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Subject: Re: [storm] iSCSI version descriptors
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Hi,

Jumping in late ...

I think compliance requirements are key here.
If you can be "compliant to version 1" if you implement mandatory
feature X AND if you do NOT implement mandatory feature X, then you
don't have a very good compliance requirement.
The purpose of a version # is to help identify the set of features
that can be expected to be supported by OTHER implementations, to
ensure interoperability.
(obviously, if the feature was originally, and continues to be,
protocol-negotiable that's not a problem within a version#)

I think it could be a poor engineering choice to have version 1 refer
to multiple different possible sets of features. I disagree that "Yes,
using the same version should be a goal", if the set of features one
implementation can expect of another implementation changes;
interoperability should be the goal. You can ignore my engineering
advice (I assume the WG knows the technology better than me). But I
would appreciate being educated why this is OK.

Interoperability is considered during IESG Evaluation
http://www.ietf.org/iesg/statement/discuss-criteria.html. If I
question the interoperability of using the same version #, others in
the IESG also might question this. So you should ***document in each
draft*** why using the same version # to identify the changes proposed
in that draft is OK technically from an interoperability standpoint. 

(p.s. "we've already implemented it that way from the draft" is NOT an
argument that holds much weight with the IESG).

David Harrington
Director, IETF Transport Area
ietfdbh@comcast.net (preferred for ietf)
dbharrington@huaweisymantec.com
+1 603 828 1401 (cell)

> -----Original Message-----
> From: storm-bounces@ietf.org [mailto:storm-bounces@ietf.org] 
> On Behalf Of david.black@emc.com
> Sent: Monday, October 25, 2010 9:56 AM
> To: paul_koning@Dell.com
> Cc: storm@ietf.org
> Subject: Re: [storm] iSCSI version descriptors
> 
> > For now, I believe we should say 3270/5048 and not mention 
> "new consolidated draft".  It doesn't
> > seem appropriate to reference a draft.  If we end up being 
> able to reuse the code for the
> > consolidated spec, as intended, then at the time that spec 
> comes out, the description of the code
> > points would be updated to say that it applies to that RFC as
well.
> 
> Yes, the specifications of the version code values need to be 
> in terms of RFC numbers, not references to Internet-Drafts.
> 
> Thanks,
> --David
> 
> 
> > -----Original Message-----
> > From: Paul Koning [mailto:paul_koning@Dell.com]
> > Sent: Friday, October 22, 2010 11:14 AM
> > To: Black, David
> > Cc: storm@ietf.org
> > Subject: Re: [storm] iSCSI version descriptors
> > 
> > 
> > On Oct 22, 2010, at 1:14 AM, <david.black@emc.com> 
> <david.black@emc.com> wrote:
> > 
> > > One more time on this issue.  This is for discussion - 
> it's not an announcement of a decision.
> > This is the only real issue that needs to be resolved to 
> complete the new (SAM) features draft for
> > iSCSI.
> > >
> > > Reminder: we need to define a set of small positive 
> integer values to describe the iSCSI version
> > starting with 0 = "no version claimed".  After some private 
> discussions, it appears that we need two
> > additional version values beyond 0.
> > >
> > > The first observation is that the baseline should be at 
> least RFC 3720 (original iSCSI) + RFC 5048
> > (Corrections and Clarifications).  That would be version value 1.
> > >
> > > The next observation is that taking features out of the 
> consolidated iSCSI draft may allow a
> > visible behavior change.  RFC 3720 has this to say about 
> text keys for negotiation:
> > >
> > >   All keys in this document, except for the X extension 
> formats, MUST
> > >   be supported by iSCSI initiators and targets when used 
> as specified
> > >   here.  If used as specified, these keys MUST NOT be 
> answered with
> > >   NotUnderstood.
> > >
> > > When we take out a feature in the new iSCSI consolidated 
> draft, the easiest thing to do is allow a
> > NotUnderstood response to the keys that negotiate that 
> feature.  This should not pose a problem for
> > unimplemented features, but it would be a behavior change.  
> The completely backwards-compatible
> > alternative is have the consolidated iSCSI draft list the 
> keys used for removed features and
> > prohibit  a NotUnderstood response to those keys (Reject 
> would be an acceptable alternative
> > response).
> > 
> > That sounds right.  Does it cause problems for that to be 
> the answer?
> > 
> > > If we're careful about this, the same version value can 
> apply to 3720/5048 and the consolidated
> > iSCSI draft.  I'd suggest that we be careful, and the 
> details of how can be worked out as we
> > finalize the consolidated draft - I think we should have at 
> least one more round of looking at
> > features to remove.
> > 
> > Yes, using the same version should be a goal.
> > 
> > > After that, we'll need a version value for the new (SAM) 
> features draft additions.  The result
> > would be 3 version values:
> > > 	0 = no version claimed
> > > 	1 = 3720/5048 or new consolidated draft
> > > 	2 = (3720/5048 or new consolidated draft) + SAM 4/5 
> features from the SAM draft.
> > 
> > I assume these numbers will be handled by IANA, so they'll 
> need an IANA Considerations section
> > spelling out how.
> > 
> > For now, I believe we should say 3270/5048 and not mention 
> "new consolidated draft".  It doesn't
> > seem appropriate to reference a draft.  If we end up being 
> able to reuse the code for the
> > consolidated spec, as intended, then at the time that spec 
> comes out, the description of the code
> > points would be updated to say that it applies to that RFC as
well.
> > 
> > For the SAM draft, can we reference a specific draft?  I 
> think it's quite absurd that drafts even
> > have standard status in the first place, but given that 
> they do, we need to be precise about which
> > document we're talking about.  If we say "draft 2010/10/34" 
> now, and then a followup draft comes out
> > for which the same code point is appropriate, we'd update 
> the description of the code point to list
> > that one as well.  But we can't leave it unstated.
> > 
> > 	paul
> > 
> 
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