Re: [storm] iSCSI feature removal: SLP ?

"David Harrington" <ietfdbh@comcast.net> Tue, 06 July 2010 19:06 UTC

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From: "David Harrington" <ietfdbh@comcast.net>
To: "'Mallikarjun Chadalapaka'" <cbm@chadalapaka.com>, "'Mark S. Edwards'" <marke@muttsnuts.com>, <storm@ietf.org>
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Date: Tue, 6 Jul 2010 15:06:07 -0400
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Subject: Re: [storm] iSCSI feature removal: SLP ?
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Hi,

I made a suggested change as a contributor because I didn't want to
come down with the force of an AD Evaluation. That will come later.
But there are some things I know will not make it through IESG
Evaluation, and the IESG is actually working to document some of the
things for which we commonly reject a document. The use of non-RFC2119
language to specify compliance is a common cause for DISCUSSes. 

The storm WG is something of a cross-SDO effort, and that might lead
to some lack of understanding of IETF process, and IESG common
complaints. Let me be sure you understand my objection.

The IETF does not support "not almost must" compliance language.
We want our standards to be clear and unambiguous.
Therefore, we have RFC2119 compliance keywords, such as SHOULD NOT and
NOT RECOMMENDED.
What you are proposing sounds to me like a SHOULD NOT, or a NOT
RECOMMENDED:

4. SHOULD NOT   This phrase, or the phrase "NOT RECOMMENDED" mean that
   there may exist valid reasons in particular circumstances when the
   particular behavior is acceptable or even useful, but the full
   implications should be understood and the case carefully weighed
   before implementing any behavior described with this label. 

The full implications appear to be that nobody seems to implement SLP,
and therefore the SLP part of your implementation will not
interoperate with many other existing implementations. Therefore,
implementing SLP appears to be NOT RECOMMENDED. I am not telling you
that you must say it is NOT RECOMMENDED; I am telling you that you
should clarify the compliance requirement that represents WG consensus
using RFC2119 language, so the requirement is clear and unambiguous.

As Responsible AD for the storm WG, I need to champion your documents
during IESG Evaluation. If you submit a document to me that says, "for
compliance, SLP is no longer almost must", then I will almost
certainly tell you to revise it before I will champion the document
for you. The WG advice SHOULD be written using RFC2119 language,
because if you don't and I send the document for IESG Evaluation, we
will all waste lots of time debating with the other IESG members when
they raise DISCUSSes questioning why we are not using RFC2119 keywords
to describe the compliance rules.

Does that explain my objection to non-RFC2119 language better?
This will also apply to other WG documents, especially those on the
standards track.

dbh


> -----Original Message-----
> From: Mallikarjun Chadalapaka [mailto:cbm@chadalapaka.com] 
> Sent: Tuesday, July 06, 2010 12:27 PM
> To: 'David Harrington'; 'Mark S. Edwards'; storm@ietf.org
> Subject: RE: [storm] iSCSI feature removal: SLP ?
> 
> Hi David and all,
> 
> With deployment experience, we now know that the original 
> "almost must"
> recommendation is not valid (ignoring the fact that it was 
> contained in an Informational RFC).  
> 
> But OTOH, we do not have to say "SHOULD NOT" implement SLP 
> either, which IMHO is overly constraining and thus unwarranted.
> 
> At this point, I plan to make it clear in the consolidated 
> draft that SLP is not an "almost must" requirement, along the 
> lines of what DavidB/Mark had proposed.
> 
> Please let me know if that is not agreeable to anyone.
> 
> Thanks.
> 
> Mallikarjun
> 
> 
> 
> > -----Original Message-----
> > From: storm-bounces@ietf.org 
> [mailto:storm-bounces@ietf.org] On Behalf 
> > Of David Harrington
> > Sent: Monday, July 05, 2010 11:03 AM
> > To: 'Mark S. Edwards'; storm@ietf.org
> > Subject: Re: [storm] iSCSI feature removal: SLP ?
> > 
> > Hi,
> > 
> > I think "recommendation is no longer valid" is equivalent to "NOT 
> > RECOMMENDED" which is equivalent to "SHOULD NOT".
> > 
> > So I recommend "SHOULD NOT" (or if you prefer, rewording to "NOT 
> > RECOMMENDED").
> > 
> > dbh (as contributor)
> > 
> > > -----Original Message-----
> > > From: storm-bounces@ietf.org [mailto:storm-bounces@ietf.org] On 
> > > Behalf Of Mark S. Edwards
> > > Sent: Wednesday, June 23, 2010 6:23 PM
> > > To: storm@ietf.org
> > > Subject: Re: [storm] iSCSI feature removal: SLP ?
> > >
> > > Looks ok to me.  I was trying to be diplomatic in case there
were 
> > > any SLP diehards out there waiting to be offended.
> > >
> > > But since none have appeared over the parapet the hammer
approach 
> > > that effectively deprecates SLP as an interoperability mechanism

> > > suits me.
> > >
> > > I agree that we should not specifically prohibit it's 
> use, after all 
> > > people are free to create and use any discovery mechanism 
> they wish 
> > > for their own purposes.  Could be SLP, could be LDAP or "Fred's 
> > > Bird-Brained Resource Locator", none should be explicitly
barred.
> > >
> > > Mark.
> > >
> > >
> > > At 21:25 23/06/2010, david.black@emc.com wrote:
> > > >Mark,
> > > >
> > > > > So if pushed I'd write something like:
> > > > >
> > > > > "iSCSI equipment that need discovery functions beyond
> > SendTargets
> > > > > should implement iSNS for extended discovery management
> > > capabilities
> > > > > and maximum interoperability."
> > > > >
> > > > > Since any unit that implements SLP or even LDAP as a 
> discovery 
> > > > > mechanism is not going to interoperate with the majority
> > > of systems,
> > > > > I'd hesitate to even mention them.  However, if anyone feels

> > > > > strongly that SLP deserves some mention, then by all means
do
> > so,
> > > > > just please don't assert it too strongly.
> > > > >
> > > > > One final point.  Given that iSNS has won the consensus
> > > argument, is
> > > > > there a case for turning the "should' in the above sentence
to
> > > >"SHOULD" ?
> > > >
> > > >Yes, I would use "SHOULD" plus I would add text to say:
> > > >
> > > >         SLP has not been widely implemented or deployed for
use
> > with
> > > >         iSCSI, therefore RFC 3121's recommendation that SLP be
> > > >         implemented is no longer valid.
> > > >
> > > >This is one of those situations in which subtlety does not win
> > style
> > > >points (IMHO) but I don't think we need a recommendation 
> that SLP 
> > > >"SHOULD NOT" be implemented.  In addition (as noted below), RFC
> > 3721
> > > >would need to be added to the list of RFCs that are 
> updated by the 
> > > >combined iSCSI Internet-Draft.
> > > >
> > > >Any objections?
> > > >
> > > >Thanks,
> > > >--David
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: storm-bounces@ietf.org 
> [mailto:storm-bounces@ietf.org] On 
> > > > > Behalf
> > > >Of Mark S. Edwards
> > > > > Sent: Monday, June 07, 2010 7:00 AM
> > > > > To: storm@ietf.org
> > > > > Subject: Re: [storm] iSCSI feature removal: SLP ?
> > > > >
> > > > > Sorry for the delay.
> > > > >
> > > > > As you say, RFC3721 was more about guidance and was
> > > written before
> > > > > there was any deployment experience.  At least the text
> > > says 'should'
> > > > > rather than 'SHOULD'.  It might be nicer to all round if it
> > could
> > > > > just be removed and no extended discovery mechanism be
> > mentioned,
> > > > > but we have realities to consider such as an iSCSI array
> > > won't get
> > > > > Microsoft certification unless it supports at least 
> basic iSNS -
> > 
> > > > > running code and consensus.
> > > > >
> > > > > The one good thing we have now is that iSNS is indeed now an
> > IETF
> > > > > protocol (RFC 4171) and the original argument for SLP was
that
> > it
> > > > > was an existing RFC.  So the argument for using SLP ahead
> > > of iSNS is
> > > > > no longer relevant.
> > > > >
> > > > > So if pushed I'd write something like:
> > > > >
> > > > > "iSCSI equipment that need discovery functions beyond
> > SendTargets
> > > > > should implement iSNS for extended discovery management
> > > capabilities
> > > > > and maximum interoperability."
> > > > >
> > > > > Since any unit that implements SLP or even LDAP as a 
> discovery 
> > > > > mechanism is not going to interoperate with the majority
> > > of systems,
> > > > > I'd hesitate to even mention them.  However, if anyone feels

> > > > > strongly that SLP deserves some mention, then by all means
do
> > so,
> > > > > just please don't assert it too strongly.
> > > > >
> > > > > One final point.  Given that iSNS has won the consensus
> > > argument, is
> > > > > there a case for turning the "should' in the above sentence
to
> > > >"SHOULD" ?
> > > > >
> > > > > Mark.
> > > > >
> > > > >
> > > > > At 23:54 21/05/2010, Black_David@emc.com wrote:
> > > > > > > Regarding the feature removal discussion, can I add SLP
to
> > the
> > > >list ?
> > > > > > >
> > > > > > > The RFC 3721 states
> > > > > > >
> > > > > > > "iSCSI equipment that
> > > > > > >        need discovery functions beyond SendTargets
> > > should at least
> > > > > > >        implement SLP, and then consider iSNS when
extended
> > > >discovery
> > > > > > >        management capabilities are required such as in
> > larger
> > > >storage
> > > > > > >        networks.  It should be noted that since iSNS
will 
> > > > > > > support
> > > >SLP,
> > > > > > >        iSNS can be used to help manage the discovery
> > > information
> > > >returned
> > > > > > >        by SLP."
> > > > > > >
> > > > > > > The implication is that targets and initiators should
> > > expect to
> > > >find
> > > > > > > support for SLP before considering iSNS.
> > > > > > >
> > > > > > > I remember our first iSCSI appliance and we spent
> > > ages trying to
> > > >get
> > > > > > > SLP working because it the above wording 
> effectively made it
> > 
> > > > > > > mandatory.  SLP turned out to be a complete bust and was
> > > >effectively
> > > > > > > killed off when Microsoft refused to support it in their

> > > > > > > initiator and in their target logo tests.
> > > > > > >
> > > > > > > The result is that today I doubt you could find a 
> target or
> > > >initiator
> > > > > > > out there supporting SLP.
> > > > > > >
> > > > > > > For anybody that does still implement SLP we could
change
> > the
> > > >wording
> > > > > > > for SLP a little to remove the implied hierarchy, or
> > > just admit
> > > >that
> > > > > > > running code has created IETF consensus.
> > > > > >
> > > > > >This is interesting.  RFC 3720 (main iSCSI spec) 
> never mentions
> > 
> > > > > >SLP.  RFC 3721 is not a Standards Track RFC, but 
> that's not a 
> > > > > >reason not to update it (if people will excuse the
> > > double negative).
> > > > > >
> > > > > >So, Mark, could you send an email to the list with
> > > proposed text on
> > > > > >SLP that you'd like to see in the new consolidated iSCSI
> > > draft (no
> > > > > >more than a few sentences, please)?  If that text (as
> > > revised) is
> > > > > >acceptable to the WG, the result would go into the new
> > > consolidated
> > > > > >iSCSI draft, and RFC 3721 would be added to the list of
> > > RFCs that
> > > > > >are being updated by that draft.
> > > > > >
> > > > > >Thanks,
> > > > > >--David
> > > > > >----------------------------------------------------
> > > > > >David L. Black, Distinguished Engineer EMC Corporation,
> > > 176 South
> > > > > >St., Hopkinton, MA  01748
> > > > > >+1 (508) 293-7953             FAX: +1 (508) 293-7786
> > > > > >black_david@emc.com        Mobile: +1 (978) 394-7754
> > > > > >----------------------------------------------------
> > > > >
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