Subject: RE: Limiting the Use of Site-Local

From: Dan Lanciani <[email-masked]>
Date: Mon, 4 Nov 2002 14:29:49 -0500 (EST)

"Michel Py" <[email-masked]> wrote:

|I support the idea that a _subnet_ should not have both site-local and
|global addresses, not a site. Please also read what I posted earlier
|concerning deprecation.

Could you clarify this position?

Let's say I have an Ethernet segment with 20 workstations and 5 printers.
I determine that two of the workstations need access to the Internet so I
rent 2 global addresses from my ISP.  Are you saying that at this point
for all the workstations to continue using the printers I have to either:

1. Rent an additional 23 global addresses from my ISP making the entire
subnet global -or-

2. Interpose a router between the 2 globally connected workstations and the
remaining 18 workstations plus 5 printers, forcing the 2 globally connected
workstations to use their global addresses to talk to site-locals on the
printers (thus making such connections depend on the ISP).  In order to change
which workstations have global access I would have to move them between subnets.

Or are you saying that site-local and global addresses should not appear
in packets on the same subnet at all (rather than as addresses of a single
machine on a subnet) in which case only #1 would work?

|> In this situation, why/how would "Router B" ever route any
|> packets? The control device(s) will only have site-local
|> addresses, so they can't send packets that will be routed
|> by "Router B", nor can any systems to left of Router B
|> (outside the site?) send packets to the control devices...

I believe Margaret is implying a restriction here that connections cannot be
made between a site-local address and a global address.  That would invalidate
solution #2 above.

I think that a number of constraints on site-local addresses are being bandied
about without much thought as to their impact.  Any one of these constraints
probably makes site-locals useless for the purposes originally promised.  Given
subject of these messages I suppose that could be the idea, but it's going to
cause a lot of confusion...

				Dan Lanciani
				ddl@danlan.*com
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From: Margaret Wasserman <[email-masked]>
Date: Tue, 05 Nov 2002 18:12:47 -0500

Hi Dan,

>rent 2 global addresses from my ISP.

What makes you think that you will "rent" individual addresses from
your ISP in IPv6?  The idea is that every customer site should
receive a /48 allocation, and individual nodes (at the end of
point-to-point links, etc.) should receive a /64.

So far, the ISPs who have deployed IPv6 (there are only a few
right now), have been allocating a /48 or a /64 to every customer.
And, we were successful in getting the 3GPP folks to change their
specs to allocate a /64 to every cell phone...

Margaret

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From: David Conrad <[email-masked]>
Date: Tue, 05 Nov 2002 15:41:11 -0800

Margaret,

On 11/5/02 3:12 PM, "Margaret Wasserman" <[email-masked]> wrote:
> your ISP in IPv6?

What makes you think ISPs will be interested in giving up revenue streams,
particularly given how well they are (not) doing?

Do you think ISPs are charging for address space because it is limited?

Rgds,
-drc

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From: Keith Moore <[email-masked]>
Date: Tue, 05 Nov 2002 19:17:04 -0500

> Do you think ISPs are charging for address space because it is limited?

No, I think ISPs are charging for address space because we have taken
away the alternative of letting customers get routable address space 
of their own.  That doesn't mean that I disagree with the decision
to encourage address aggregation, just that there might be some 
undesirable consequences of that decision even if it was the best 
thing to do.  

Realistically, routing table space and updates and computation are,
with current technology, finite or even scarce resources.  It's hard 
to believe that sooner or later this wouldn't cost something, though 
perhaps not as much as it does now.

Keith

p.s. perhaps somebody would like to explain why my ISP tries to impose
NAT and RFC 1918 addresses on its DSL customers even though the addresses
on the other side of the DSL modem are globals, and even though the DSL
modems they ship won't talk to more than one Ethernet address between 
power cycles?  it's not helping any (hypothetical or otherwise) address 
shortage, and it's not providing any security benefit to their customers.
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