Re: [storm] iSCSI version descriptors

Paul Koning <paul_koning@dell.com> Fri, 22 October 2010 15:15 UTC

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From: Paul Koning <paul_koning@dell.com>
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Date: Fri, 22 Oct 2010 11:14:17 -0400
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Subject: Re: [storm] iSCSI version descriptors
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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