Subject: iSCSI Naming: WWUIs, URNs, and namespaces

From: [email-masked]
Date: Fri, 23 Mar 2001 00:47:37 -0500

<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

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

---

From: Mark Bakke <[email-masked]>
Date: Fri, 23 Mar 2001 08:36:09 -0600

David-

This is starting to seem like work.  In case they help,
please see my comments below.  We can take this up in
more detail in the N&D team.

--
Mark

> for iSCSI's use - this means that WWUIs as currently

So I take it that WWUIs are fine, as long as they use
existing global name spaces.

> be glued into the WWUI world (as several were).

The reason we glued these in was to avoid creating a new
global name space.  We allowed the use of a few currently
available global name spaces.  How can this be a problem?

>         sense.  I don't see a problem here.

So far, so good.  Does that mean that we can keep the above
two, in the current WWUI, as we have it formatted?

EUI, although it's not that flexible (see later), is required
for interoperating with and adding iSCSI to existing devices.

>         should be reviewed before proceeding too far in this

I don't like this one that much, either, for the same reasons.

>         on the list would be appropriate.

These two formats use existing global name spaces, and allow
the implementor or end user to take a more flexible approach
to naming than is offered by the EUI-64.  When dealing with
a large number of logical targets, burning WWNs (essentially,
MAC addresses), and attempting to keep them tied to a logical
entity without tying them to hardware is not practical.

Both of these formats accomplish the same thing, and we could
make do with just one of them.  The only real differences are:

- OUI is a fixed length naming authority; reverse DNS is variable
  and could result in longer names.

- A human looking at a reverse DNS-based name can easily determine
  who the naming authority is; a human looking at an OUI-based
  name will usually have to go look it up at IEEE.

- Only a hardware manufacturer (and a few software manufacters)
  will already have an OUI.  Others, such as storage service
  providers, large end customers, or software driver providers,
  would either be out-of-luck for naming their devices, or would
  have to register for an OUI, which would otherwise be a waste
  of IEEE resources.  OTOH, a storage service provider could
  provide its own names by using the reverse-DNS authority.
  Everyone has a DNS name.  This would enable the SSP to provide
  its customers with a WWUI that would not change if the back-end
  storage device was replaced.  After all, it's not the device
  that's important to this customer, it's the DATA.

- If we had to pick one or the other, I would pick the reverse
  DNS, since it offers the ability to generate unique names to
  a wider variety of users.

> In any case, the fewer name formats we have to deal with,

Although I probably should have discussed this with the rest
of the NDT first, I would personally be happy with:

- iscsi - The canonical name.
- eui - For compatibility with existing device naming schemes.
- reverse-dns - For better naming flexibility moving forward.

Perhaps the IESG would accept the WWUI with just these three.
Or perhaps we could just make the WWUI into a URN?  I don't
know if that would help, but perhaps...

The main point is that we are NOT creating any new name
spaces; we really are just using what's already there.  Maybe
by specifying fewer of the options that are already there, we
would be in better shape.

> the intended usage of names and their scope matter a lot.

So that leads to the question: Has any other WG come up with
a world-wide-unique-identifier for something else that the
IESG folks deems acceptable?  If we can see a few examples,
we would be better able to anticipate what they want.

> namespaces) and why would be useful.

From a requirements point of view, please respond if any
of the types of names are important to you (plural).

Hopefully, we can get this out of the way quickly.

-- 
Mark A. Bakke
Cisco Systems
[email-masked]
763.398.1054

---

From: "Renato E. Maranon" <[email-masked]>
Date: Fri, 23 Mar 2001 09:36:17 -0800

I'm with Mark Bakke on the minimum:

Renato Maranon
Maranti Networks, Inc
920 Hillview Court
Milpitas, Ca 95035
Phone:  408-719-9600 x309
Fax:    408-719-9631
email:  [email-masked]
home:   www.marantinetworks.com

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
Mark Bakke
Sent: Friday, March 23, 2001 6:36 AM
To: [email-masked]
Cc: [email-masked]
Subject: Re: iSCSI Naming: WWUIs, URNs, and namespaces

David-

--
Mark

 

-- 
Mark A. Bakke
Cisco Systems
[email-masked]
763.398.1054