Subject: RE: IPv6 Addr/Prefix clarification

From: "Michel Py" <[email-masked]>
Date: Thu, 31 Jan 2002 16:29:27 -0800

>>> Keith Moore wrote:
>>> By allowing sites to subnet /64s we aren't forcing them to give up
>>> autoconfig, private addresses, etc...

>> Michel Py wrote: 
>> Would you educate me on how you do autoconfig, let's say, on a /85 ?

> Keith Moore wrote:
> you don't.  a site that chooses to subnet below /64 is inherently
> choosing not to use stateless autoconfig.  but this is a choice for
> that site to make, not for us to make on that site's behalf.  

This is direct contradiction with what you wrote before.

> you still haven't given a single argument in favor of not allowing
> sites to subnet below /64.

Yes, I have. And you haven't yet given a single good reason why a site
should subnet below /64, when a site should, indeed, use the SLA bits
(means SITE LEVEL AGGREGATOR) which have been designed for that very
purpose.

Michel.

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From: Keith Moore <[email-masked]>
Date: Thu, 31 Jan 2002 19:57:09 -0500

> This is direct contradiction with what you wrote before.

no it's not. 

> (means SITE LEVEL AGGREGATOR) which have been designed for that very

A site should subnet below /64 if - for any reason - it doesn't have 
enough subnet bits above /64 and - for whatever reason - it can't
get more address space by other means.  

Perhaps this will only happen if we fail to allocate prefixes efficiently, 
and/or if ISPs don't follow our recommendations.  But if either of those 
does occur, it will make perfect sense to subnet below /64 - and it's
certainly a lot saner than NAT.

On the other hand, expecting that everything will go exactly as we've
anticipated - when we don't even agree about how things will go - 
is utterly insane.

Keith

---

From: "Tony Hain" <[email-masked]>
Date: Thu, 31 Jan 2002 17:06:25 -0800

You are both right and wrong... ;)

We can never prevent a site from internally subnetting on any boundary
it chooses, but we should be very clear about the consequences. At the
same time we have to be consistent in our discussions with the rir's and
providers about making sure sites have at least the options of /48 &
/64, and that attempts to allocate less will result in ugly hacks that
will be hard for them to maintain.

The strongest reason to make this a hard architectural boundary is to
simplify the dev/test/interoperability of the code for the platform
vendors. Sites that accept a /64 are stuck with a single subnet, unless
they have sufficient technical knowledge to break the architecture; and
have the appropriate support from their platform vendors. We are not in
a position to prevent architectural abuse (even in our documentation;
see RFC3022), but we can set expectations and interoperability
requirements.

If a site receives a /64 from their provider, the simplest approach
would be to bridge the environment. For those that want a more complex
topology, they will be better-off to lobby their provider for more
space. Given track records, this is likely to be possible for a simple
matter of more money. For those who don't want to pay for address space,
but do want to pay for the cost of local implementations which subnet
longer than /64, they are free to do so. One might point out this is a
false economy, but people don't always listen.

Tony

> -----Original Message-----
> From: [email-masked]
> [mailto:[email-masked]]On Behalf Of Michel Py
> Sent: Thursday, January 31, 2002 4:29 PM
> To: Keith Moore
> Cc: [email-masked]
> Subject: RE: IPv6 Addr/Prefix clarification
>
>
> >>> Keith Moore wrote:

---

From: Keith Moore <[email-masked]>
Date: Thu, 31 Jan 2002 21:00:02 -0500

> will be hard for them to maintain.

agree entirely.

> vendors. 

I guess I'm arguing that we should make it clear to vendors that
it's *not* reasonable to assume that nobody will ever need to subnet
beyond /64.  

> Sites that accept a /64 are stuck with a single subnet, unless
> they have sufficient technical knowledge to break the architecture

and I'm arguing that the 64 bit boundary should not be a wired-in
part of the architecture (just as in hindsight it turned out to be
a bad idea to make class a/b/c boundaries a part of the v4 architecture)
it's not just for sites -  someday we may be forced to rethink 
allocation strategies in a way that gives sites less than /64.

> matter of more money. 

'more money' is not always a simple matter - sometimes the difference
is between being able to operate at all or not. 

> For those who don't want to pay for address space,

and it's not always a false economy.  it depends on the other factors.

Keith