Subject: Re: Naming and site-local addresses

From: Dan Lanciani <[email-masked]>
Date: Sun, 10 Nov 2002 15:25:56 -0500 (EST)

Harald Tveit Alvestrand <[email-masked]> wrote:

|This seems to lead me to one of two conclusions:
|
|- Address lookup is significantly more complex in the presence of 
|site-local than if only global-scoped addresses are used
|
|- I missed something.
|
|Comments?

I don't think you missed something.  If anything, site-locals are even more
complex to support than you suggest.  But site-locals (or, more generally,
scoped addresses) are what we got in the face of the questionable assertion
that provider-independent global/routable addresses are too difficult to even
think about supporting.

As long as we are stuck with a totally non-scalable address allocation
system (remember, provider-based aggregated addressing consumes address
space *exponentially* in the number of providers in the service chain)
end users need some way to provision local systems with stable addresses.
So far, nobody has proposed a viable alternative to scoped addresses.

				Dan Lanciani
				ddl@danlan.*com
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From: Harald Tveit Alvestrand <[email-masked]>
Date: Mon, 11 Nov 2002 08:06:18 +0100

> So far, nobody has proposed a viable alternative to scoped addresses.

metro addressing?

btw, my current naive prediction of the way the Internet will evolve is 
that unless new invention occurs, the default-free zone will eventually be 
flat-routing on the number of ISPs in the world, and that this number will 
have 5 digits.

stable addresses for the lifetime of your ISP service contract seems like a 
not too terrible deal, if renumbering is easy.

for IPv6 address allocation schemes, check out 
http://www.ripe.net/ripe/docs/ipv6-sparse.html for some recent thoughts.

                Harald

---

From: Michael Thomas <[email-masked]>
Date: Mon, 11 Nov 2002 09:02:54 -0800 (PST)

> http://www.ripe.net/ripe/docs/ipv6-sparse.html for some recent thoughts.

Harald, 

I think this probably boils down to something
completely non-technical: do people view IP
addresses as "addresses" ala street addresses,
etc, or do they view them as possessions like
(now) phone numbers and email addresses. Though
the net was designed for "addresses", I suspect
that they are viewed more as possessions which is
an obvious problem. 

The only question that remains is whether we are
-- as they say -- pissing up a rope. If we are, we
just need to accept reality and move on from
there.

		Mike

---

From: Harald Tveit Alvestrand <[email-masked]>
Date: Mon, 11 Nov 2002 18:15:36 +0100

> that they are viewed more as possessions which is

my personal opinion is that the only people who feel any possessive 
instinct towards 2002:d90d:1cca:2:210:dcff:fe5a:f1fd are the people who 
have to reconfigure other stuff when it changes.....

unlike domain names or easy-to-remember phone numbers, hanging on to a v6 
address is something you do for practical reasons, not emotional ones.

of course, I could be wrong...

---

From: David Conrad <[email-masked]>
Date: Mon, 11 Nov 2002 11:04:08 -0800

Hi,

> have to reconfigure other stuff when it changes.....

Or the people who are affected when reconfiguration occurs.

Welcome to NATv6.

Rgds,
-drc

---

From: Brian E Carpenter <[email-masked]>
Date: Tue, 12 Nov 2002 09:52:37 +0100

> Or the people who are affected when reconfiguration occurs.

It's our job to stop that happening.

Also, the vast majority of Internet users are not in the least
possessive about their IP address; it's different every time they
connect. Those who are possessive are those who run services of one
kind or another. It's our job to make that possible without forcing
them down the NAThole.

   Brian

---

From: Tim Chown <[email-masked]>
Date: Tue, 12 Nov 2002 09:15:24 +0000

> kind or another. It's our job to make that possible without forcing

And of course the ones who run services of one kind or another would be
in the vast majority in an IPv6 world, rather than the vast minority.

I think NATv6 is inevitable, because some site policy makers will demand
it.  Our "job" is to provide a well-engineered alternative that the
market will demand.   If enough ISP's provide v6 services the right way,
the market demand for those services will mean NATv6 will be naturally
stunted in adoption.  If ISP X enables me to control and view three IPv6
enabled webcams, a secure home filestore, program my tivo/vcr, monitor home
appliances, etc, all in a relatively plug-and-play way, and ISP Y does not,  
because it uses NATv6, then it's highly likely ISP X will flourish and ISP Y 
will fail...

Likewise ISP's offering static /48's will probably flourish over those that
do not (and certainly over those that offer only /64's).  

Tim

---

From: Margaret Wasserman <[email-masked]>
Date: Tue, 12 Nov 2002 05:45:17 -0500

Hi Brian,

>It's our job to stop that happening.

I agree, and I actually consider our job to be even bigger
than this...

We need to create the technologies and policies that will enable a
globally-addressable, "flat" IPv6 Internet.

We need to understand and document how a flat IPv6 Internet can be
deployed in parallel with the existing IPv4 Internet without
introducing serious operational or security problems.

We need to provide enough education regarding the advantages of
a globally-addressable, flat Internet that we can change the way
that large numbers of people think about network architecture.
Remember there are more Internet administrators who were spawned
and trained during a time of widespread NAT use than there are
those of us who remember the flat IPv4 Internet.

AND, in the meantime, we need to avoid advocating NAT or NAT-like
solutions to problems that can be solved without destroying the
global-addressability or "flatness" of the IPv6 Internet.

>kind or another. It's our job to make that possible without forcing

I completely agree.

But, what I don't understand is how the use of overlapping site-local
addresses on globally-attached networks is any better than NAT.

Margaret

---

From: Brian E Carpenter <[email-masked]>
Date: Tue, 12 Nov 2002 12:07:03 +0100

below...

> addresses on globally-attached networks is any better than NAT.

My recollection is that site-local entered the architecture to
cover the somewhat theoretical case of a multi-subnet site that
for whatever reason wasn't connected, and so didn't have a global
prefix. And our problems with SL come from trying to use it
outside that limited scenario. If we keep it inside that scenario,
it seems easy enough to deal with.

So, why not simply deprecate SL for sites that have at least one
global prefix? Or am I too simple minded?

That would then leave us with a couple of real problems to avoid NAT:
multihoming, and easy renumbering.

   Brian

---

From: Margaret Wasserman <[email-masked]>
Date: Tue, 12 Nov 2002 06:23:56 -0500

Hi Brian,

>global prefix? Or am I too simple minded?

If you are too simple minded, then I am right there with you.

My making this exact suggestion is what started the 500+ message
mail storm two weeks ago that has received so much attention on
other lists...

>multihoming, and easy renumbering.

Yes, exactly.  And, it may be easier to determine ways to solve
these problems in a flat address space than it will be to solve the
myriad problems created by the global use of site-locals.

Also, please note that although it has been suggested as an element
of some solutions, the global use of site-locals doesn't actually
solve either of these problems.

Margaret

---

From: Tim Chown <[email-masked]>
Date: Tue, 12 Nov 2002 14:25:37 +0000

> global prefix? Or am I too simple minded?

I think a site getting global connectivity would find it hard to migrate
instantly from site-locals to globals.  The suggestion to prefer globals
over site locals in the default address selection spec, along with Brian's
suggested text a couple of mails back, seems good.   A question is how
does a 100, 10,000 or 1,000,000 node network using site-locals most
efficiently migrate to globals, with minimum disruption, when gaining 
external connectivity?  How long would the process take?
 
> multihoming, and easy renumbering.

Maybe we should promote deployment scenarios that reduce the required
frequency of renumbering, like using static rather than dynamic /48's for
broadband customers.  Perhaps that is an issue for the RIR's as it would
require significantly more than a /32 for an ISP to do static /48's to
a few million customers at an 80%-85% host density ratio.  

Should Christian's renumbering scenario draft be revisited?
http://www.join.uni-muenster.de/drafts/draft-huitema-ipv6-renumber-00.txt
I don't believe it is still current?
Is this a v6ops or an ipv6 WG issue?

Tim

---

From: Markku Savela <[email-masked]>
Date: Tue, 12 Nov 2002 17:12:22 +0200

> From: Tim Chown <[email-masked]>

> suggested text a couple of mails back, seems good.

Why should it be a problem?

- existing connections can continue to use the site locals, presense
  of global connectivity should not touch them in any way.

- as far as I know, source address selection prefers site local if
  destination is site local, and global if destination is global. So,
  if your application gets site local address from your "two-faced
  DNS", it works; if your application gets global address due to
  current global connectivity, global address is used as a source too.

- when global connection goes down, all applications using the global
  addresses will fail, but those using site locals continue to work.

- it seems that it would be advantageous for nodes within the site to
  use sitelocals whenever possible, especially if your global
  connection is via flaky connection.

---

From: Margaret Wasserman <[email-masked]>
Date: Tue, 12 Nov 2002 10:26:48 -0500

I understand the theoretical issue, but is this a real-life issue?

How many huge non-globally-connected IP networks will ever need to
join the Internet?

Margaret

---

From: Michael Thomas <[email-masked]>
Date: Tue, 12 Nov 2002 07:32:01 -0800 (PST)

> kind or another. It's our job to make that possible without forcing

   Internet users, or people who make decisions for those
   internet users? I think the "possessiveness" is directly
   related to the desire for stability, so Joe Webpack 
   probably doesn't care too much about this, but his
   employer's IT department cares a whole lot. Also: we
   haven't seen the fully impact of Joe Peerpack
   (esp VoIP), so it's a bit premature to guess,
   I'd think.

	Mike

---

From: Tim Chown <[email-masked]>
Date: Tue, 12 Nov 2002 15:38:12 +0000

>   connection is via flaky connection.

Indeed, but this is the dilemma between preference for globals to avoid the
site-local scoping "headaches" and preference for site-locals for connection
persistence during renumbering or (dis)connectivity events.

Tim

---

From: Brian E Carpenter <[email-masked]>
Date: Tue, 12 Nov 2002 17:03:27 +0100

> persistence during renumbering or (dis)connectivity events.

Er, but I use global addresses every day on good ol' IPv4, within my
employer's internal network, and they work just fine when external
connectivity is broken. I see no advantage in local addresses here.

    Brian

---

From: Keith Moore <[email-masked]>
Date: Tue, 12 Nov 2002 11:10:50 -0500

> Those who are possessive are those who run services of one
> kind or another.

I think this is a bit too specific - until we produce a good way of
doing renumbering, any site with more than a few hosts has good reason
to want its addresses to be stable, whether or not it thinks it 
is running 'services'. 
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From: Markku Savela <[email-masked]>
Date: Tue, 12 Nov 2002 18:21:42 +0200

> connectivity is broken. I see no advantage in local addresses here.

Well, but that may change in IPv6: when your global connection
disappears, your routers may stop advertising the global prefixes in
RA's, thus your connections using global addressess will fail, because
there is no route (onlink prefix) for them anymore.

Of course, your routers may keep on announcing the global
prefixes. However, there may be some confusion, if your new global
connection brings up a different prefix (site renumbering), and your
old prefix has been assigned to someone else.

I think this is just a choice for site to make, if they know they have
fixed global prefixes, they don't need to configure their routers to
advertise site locals. They just configure the fixed globals. Again,
no problem.
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From: Keith Moore <[email-masked]>
Date: Tue, 12 Nov 2002 11:12:22 -0500

> it. 

which is why we need to make it very clear that NAT is not acceptable
in IPv6.

---

From: Tim Chown <[email-masked]>
Date: Tue, 12 Nov 2002 16:37:26 +0000

> advertise site locals. They just configure the fixed globals. Again,

That may be true, but I was also considering the fact that a discontinuity
event may be between connections where different prefixes are used.  Thus
you could still use the global addresses allocated at the last time of
connection (if you are isolated you can in theory use what you like...), but 
this prefix and the addresses may change with the next connection.  If
you know you'll come back online with the same addresses, you may be able
to make different assumptions (but as Keith said earlier, the applications
won't be aware of this).

Tim

---

From: Keith Moore <[email-masked]>
Date: Tue, 12 Nov 2002 11:12:22 -0500

---

From: Margaret Wasserman <[email-masked]>
Date: Tue, 12 Nov 2002 05:55:28 -0500

Hi Tim,

>Our "job" is to provide a well-engineered alternative that the
>market will demand.

Excellent point, and well put.

Margaret