Subject: (IPng 7356) W.G. Last Call on "A Method for flexible IPv6 Address Assignments"

From: Bob Hinden <[email-masked]>
Date: Wed, 24 Mar 1999 17:50:04 -0800

This is a IPng working group last call for comments on advancing the
following document as a Informational RFC:

	Title         : A Method for flexible IPv6 Address Assignments
	Author(s)	: M. Blanchet
	Filename	: draft-ietf-ipngwg-ipaddressassign-00.txt
	Pages		: 5
	Date		: 17-October-1009

Please send substantive comments to the ipng mailing list, and minor
editorial comments to the author.  This last call period will end two
week from today on April 7, 1999.

Bob Hinden / Steve Deering

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From: Shane Kerr <[email-masked]>
Date: Thu, 25 Mar 1999 11:58:49 -0500 (EST)

> 	Filename	: draft-ietf-ipngwg-ipaddressassign-00.txt

The first Y2K bug I've experienced.  ^^^^  Unless this draft is MUCH
older than 6 months.  (Okay, maybe it's just a typo.)

> week from today on April 7, 1999.

Is it just me, or does IPv6 seem very classful?  With all of this TLA,
sub-TLA, NLA, SLA, and now sub-NLA stuff, that is.  I much prefer to think
in terms of /13, /29, /35, /48, or /40, especially since the definitions
of the aggregation levels are subject to change.  "I can't route from my
SLA."  "Is that a new-style SLA or an old-style SLA?"  Yuck.

Anyway, to address this draft, I do indeed like the suggestion of using
the RFC1219 style of numbering from the leftmost bits on allocation, but
am concerned with how general the applicability is, especially when the
centermost numbering is added.

RFC1219 deals with the problem of allowing a network operator to grow (and
shrink, I suppose) network sizes gracefully.  However it assumes that the
administrator decides what number are going to be assigned on both the
leftmost and rightmost ends of the bit-field.  While this is possibly true
in an organization, I suspect that there aren't nearly so many
organizations that control network assignments at THREE levels.

This draft has little or no applicability to registries, since we can't
really make any kinds of assumptions about how address space will be used
- maybe the context should be refocused towards bodies that have some 
control over multiple levels of the address hierarchy (large ISP's,
multi-building corporations, or universities perhaps).

Personally, I'm operating under the assumption that an initial /35
allocation will be enough space for any one organization for the
forseeable future (after all, this is a number of networks 1/8 the size of
the existing IPv4 address space).

--
Shane Kerr <[email-masked]>
Software Engineer
American Registry for Internet Numbers

---

From: Bob Fink <[email-masked]>
Date: Thu, 25 Mar 1999 09:37:17 -0800

Shane,

At 11:58 AM 3/25/99 -0500, Shane Kerr wrote:
...
>the existing IPv4 address space).

I disagree that a /35 is reasonable as it removes the possibility for a
larger provider to allocate space from the NLA below them (which would only
be 13 bits in the case of the /35 Sub-TLA) in a hierarchical manner to
downstream transits/networks and leave those networks any space to work with.

For example, if you imagined a Sprint or UUNET or MCI as the Sub-TLA, they
could easily have hundreds of downstream local ISPs. If you used a 6-8 bit
NLA1 space for these downstream ISPs, then each would only have 7-5 bits
for their customers NLA2 space below them... hardly enough in any real
world situation for them to number many customers. And saying that the ISP
could just come back for more of their /29 Sub-TLA space doesn't make it
work as you are already committed to staying to the right of the /35 unless
serious and continuous renumbering takes place.

Return to a /29 Sub-TLA initial assignment and let the ISPs get about their
business, IMO.

Bob

---

From: Shane Kerr <[email-masked]>
Date: Thu, 25 Mar 1999 13:36:33 -0500 (EST)

On Thu, 25 Mar 1999, Bob Fink wrote:

> larger provider to allocate space from the NLA below them (which would
> only be 13 bits in the case of the /35 Sub-TLA) in a hierarchical manner
> to downstream transits/networks and leave those networks any space to
> work with. 

See, this is exactly the kind of classful thinking that I was talking
about in my e-mail!  By restricting ourselves to these TLA/NLA/SLA notions
we've sucessfully turned a 128-bit address into a 13-bit address, even
though there are 29 bits available.  Forcing arbritrary bit boundaries
causes artificial shortages, as we observe here.

> For example, if you imagined a Sprint or UUNET or MCI as the Sub-TLA,
> they could easily have hundreds of downstream local ISPs. If you used a
> 6-8 bit NLA1 space for these downstream ISPs, then each would only have
> 7-5 bits for their customers NLA2 space below them... hardly enough in
> any real world situation for them to number many customers. And saying
> that the ISP could just come back for more of their /29 Sub-TLA space
> doesn't make it work as you are already committed to staying to the
> right of the /35 unless serious and continuous renumbering takes place.
>
> Return to a /29 Sub-TLA initial assignment and let the ISPs get about
> their business, IMO. 

I'm just a humble engineer, without any say in these earth-shaking
political policy decisions.  Nevertheless, we intend to reserve a /29 for
all comers initially, even though we only assign them a /35.  For those
organizations that actually need a /29, there will be no trouble in
getting the additional space, without any renumbering.  I'm not really
sure what your comment about us being "committed to staying to the right
of the /35" means.

I would also like to raise a point that I mentioned briefly to Bob Hinden
at the IETF, which is the inability to renumber easily is going to create
another source of artificial shortage of numbers.  Given that renumbering
is hard, organizations are going to try to get larger space than they need
in order to avoid renumbering.  As an employee of a registry, I'd like to
do everything in my power to reduce the tug-of-war that's going to occur
between the registries and organizations, as we try to limit the number of
TLA's (for routing - really!) and they try to avoid increased operational
costs of renumbering.  I guess I'd just like to raise awareness that this
is an actual issue, and not just something to dismiss as being "hard".
BTW, Matt Crawford's work on router renumber is an excellent start,
although as he indicated in his "Steal this Slide" presentation he will
probably not be able to do further work on this (as in cascading
renumbering protocols and so on).

Personally, I just want a /63 from my ISP.  Is that even possible as
things are planned today?  "I'm sorry, SLA or single-IP only."

---

From: Craig Metz <[email-masked]>
Date: Thu, 25 Mar 1999 14:13:33 -0500

In message <Pine.GSO.3.96.990325125809.15788A-100000@sunshine>, you write:
>getting the additional space, without any renumbering.

  Aside: Given that both human-printable addresses and current-generation IPv6
DNS use hexadecimal digits, splitting the assignment prefix on something not a
hexadecimal digits encourages configuration errors. It may be way too late now,
but IMO the registries should seriously reconsider any boundary choice that is
not a multiple of four bits.

  On /29 vs /35, if my understanding is correct, even when registrants are only
"allowed" to use the first /35 slice, they have the /29 reserved for them and
are supposed to use a /29 top-level route. If the /29 is reserved for them and
they have a route for /29, then what motivation is there for a site to go
through the headache of getting approval from the registries to use the rest of
their /29 instead of just doing it? That, in turn, appears to defeat the entire
purpose of the /35's existence.

									-Craig

---

From: Craig Metz <[email-masked]>
Date: Thu, 25 Mar 1999 14:22:57 -0500

>things are planned today?  "I'm sorry, SLA or single-IP only."

  On the 6Bone, many providers do what's right, not what the specs says you're
necessarily supposed to do. For example, point-to-point links are generally
set up as /126 subnets, even though there's a decent argument based on the
addressing specs that you shouldn't do that (they'd be /127 if we didn't burn
the zero-host address for anycast).

  I expect that operational practice will match this. If, understanding the
consequences of your actions (e.g., possible future renumbering), you ask your
provider for an allocation that conserves address space, most will probably be
happy to give it to you. In the IPv4 world, if you ask your ISP to give you
less address space, most ISPs won't argue with you ;)

									-Craig

---

From: "Matt Crawford" <[email-masked]>
Date: Thu, 25 Mar 1999 14:27:00 -0600

> Is it just me, or does IPv6 seem very classful?

Yes and no.  From the site's point of view there's only one class.

> I much prefer to think in terms of /13, /29, /35, /48, or /40, ...

I'm with you on that, but I can't agree with the following.

> forseeable future (after all, this is a number of networks 1/8 the
> size of the existing IPv4 address space).

This is a distortion.  Leaving aside the home dialup customers for
the moment, all "Sites" get a /48.  No more, no less.  That is a
choice which has been made and has some technical reasons behind it.
It's not, begging your pardon, for registries or ISPs to haggle
about.  It's changeable only by IETF action, if at all.

That means that a /35 allows numbering of up to 2^13 sites.  The
registries and ISPs know better than I do what efficiency there may
be if there are one, two or three intermediate levels of delegation.

We may assume that IPv6 renumbering will become much less painful
than IPv4 renumbering is today but even so, it is very well that room
is being reserved for growth of the initial /35's without renumbering.

I'm hoping that someone else will write about the other goal of
aggressive aggregation -- limiting the size and volatility of the
default-free routing tables.
______________________________________________________________________________
Matt Crawford                    [email-masked]                     Fermilab
"A5.1.5.2.7.1. Remove all classified and CCI boards from the COMSEC equipment,
thoroughly smash them with a hammer or an ax, and scatter the pieces."
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From: Marc Blanchet <[email-masked]>
Date: Thu, 25 Mar 1999 16:55:23 -0600

>older than 6 months.  (Okay, maybe it's just a typo.)

The draft is ok.

>SLA."  "Is that a new-style SLA or an old-style SLA?"  Yuck.

The use of *LA in the draft was just to identify each party.  This draft
does not define a new assignment scheme.

>the RFC1219 style of numbering from the leftmost bits on allocation,
> but am concerned with how general the applicability is, especially when the

You use it if you need it. The registries may not want to use it. But I
know already major networks that are using the draft for making the
assignments.  

You can also think about the large organisations that have been assigned a
prefix and want to delegate the task of assignments to divisions and the
divisions delegate to departements and furthermore. Then using this scheme
enables you to have more flexibility if the network changes, or 10 new
divisions of a company that has been bought, like it seems to happen often!.

>shrink, I suppose) network sizes gracefully.  

Assignment is not only done by "network operators". 

>However it assumes that the

See the comment before.

>really make any kinds of assumptions about how address space will be used

as said, you choose if you want to use it. 

>multi-building corporations, or universities perhaps).

that was the intent.

Maybe, I can change the wording to be more precise on this.  

>the existing IPv4 address space).

Thanks for your comments.

Marc.

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From: Brian E Carpenter <[email-masked]>
Date: Fri, 26 Mar 1999 09:31:16 +0000

Shane,

Let's not confuse the discussion of the TLA address format and
structure, which is a done deal already decided by the IETF,
and TLA/subTLA allocation policy, which is a non-IETF matter
currently being debated among the registries. 

You are correct that getting renumbering to work (more) easily
is key, and that is what the IETF should be worrying about now.

  Brian

---

From: Brian E Carpenter <[email-masked]>
Date: Fri, 26 Mar 1999 11:37:40 +0000

I can see no argument against publishing this as informational,
though whether the registries implement it is another matter.

> 5. Implementation
> 
> While describing this method is easier displaying bits, it is not useful 
> to do the assignment using bits.  Programs implementing this method will 
> be useful.

This is very unclear to me; there seem to be many logic steps compressed
into this, and the last sentence is not useful without considerable
explanation.

> 7. Security Considerations
> 
> Address assignment doesn't seem to have any specific security consideration.
> 
I'm sure that "doesn't seem to have any" won't get past the IESG.
"has no known" would be better.

   Brian