iSCSI Naming: WWUIs, URNs, and namespaces

[Black_David@emc.com]

<RANT> I don't like naming issues. </RANT> :-) :-)

After suitable consulting with some members of
the IESG and IAB, I have some news to convey about
the current approach to iSCSI naming.

The IESG will not approve another global namespace
for iSCSI's use - this means that WWUIs as currently
designed will need to be revised out of the
naming and discovery draft, and that it will not be
possible to proceed with the WWUI URN draft
as an official IPS WG work item.  The best course of
action would probably be to allow the WWUI URN draft
to expire without further revision.

To a first approximation, WWUIs are/were a "grand
unified theory" of naming, in that any namespace could
be glued into the WWUI world (as several were).
The WG is being directed to instead focus on the
individual namespaces and make sure that the ones that
are used are in fact necessary.  iSCSI can use text
keys to identify which sort of name is being used
(one key for each sort of format, for each instance
in which a name is used), and it may be possible
to encode the name format in the parse rules for the
values of iSCSI keys to avoid proliferation of keys.

Taking a look at the namespaces in the current iSCSI
naming and discovery draft, here's some initial
guidance from this WG co-chair:
  iscsi - canonical target -- This should be fine.
  eui - WWNs -- The use of these for storage makes eminent
	sense.  I don't see a problem here.
  dns - hostnames -- Use of these should be abandoned as
	not only are they not really URNs (as indicated
	in the draft), but their intended usage is straying
	into the tarpit known as "URN resolution".  Faster
	progress will made by staying out.  A DNS hostname
	can be put into an Alias or something new can be
	invented to carry it as a Location Hint, BUT the
	relevant URN WG RFCs and drafts on URN resolution
	should be reviewed before proceeding too far in this
	direction.
  iscsi - Reverse DNS and oui - Org. Unique Identifier --
	The rationale for these is not clear to me.
	Assuming that WWNs are going to be available for
	use in naming iSCSI Initiators and Targets, what
	are the problems that these sorts of names solve
	that WWNs don't?  It appears that one of the problems
	may be who can get/create them.  Discussion of this
	on the list would be appropriate.
In any case, the fewer name formats we have to deal with,
the better.

I want to try to anticipate an objection to this, which
would note that from a functional viewpoint the basic
impact of this is to move some characters from one text 
string to another (e.g., from a WWUI type designator
to part of an iSCSI text key), and wonder if this is
a distinction without a difference.  One of the reasons
for the <RANT> that started this post is that a functional
view is not sufficient for naming - how things are named,
the intended usage of names and their scope matter a lot.
This is particularly true when considering the structure
of a namespace and how that structure may be extended.
The upshot is that avoiding introduction of something
claiming to be yet another global namespace is important
(i.e., use existing namespaces with global scope in preference
to inventing new ones).  The resulting need to define
the name spaces/formats in the main iSCSI spec. is
probably a "feature" as it forces us to pay more
attention to the sorts of names we use and raises the
bar for adding additional sorts of names in the future.

I will be working with
the naming and discovery team in my "copious spare time"
to make sure that we don't lose the valuable work and
progress they've made to date as a consequence of this
change.  Discussion on the list about what sort
of names are important (e.g., the Reverse DNS and OUI
namespaces) and why would be useful. 

Thanks,
--David


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David L. Black, Senior Technologist
EMC Corporation, 42 South St., Hopkinton, MA  01748
+1 (508) 435-1000 x75140     FAX: +1 (508) 497-8500
black_david@emc.com       Mobile: +1 (978) 394-7754
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