Subject: (multi6) Ease of re-numbering

From: "Michel Py" <[email-masked]>
Date: Fri, 26 Oct 2001 07:46:07 -0700

Iljitsch and Brian--

You are both right, but the point that Tim and I are trying to make is
that the pain of renumbering is not reachability (and to that regard
IPv6 will be easier) but all the associated host, server and security
configuration.

In Iljitsch's example, the small ISP does not provide much services,
let's say connectivity, pop/smtp mail and news. These are not a big deal
(besides, the size and geographical location would still be manageable).

What I have to deal with is dozens of frame-relay and point-to-point
circuits to third-party entities including high-inertia ones such as
governments, in several time zones. We don't provide connectivity to
these guys, we provide services. Like it or not, there are still people
that configure batch files based on IP address, static entries in the
lmhosts files, that kind of stuff. And all of these guys have
access-lists all over the place, and so do we. Even in a dream world
where people would actually use DNS and quit configuring static routes,
access-lists and firewall holes are still based on IP and renumbering a
large setup is NOT an afternoon.

Michel.

From: Brian E. Carpenter
Remember that v6 renumbering can include a period of overlap between the
old
and new prefixes, when both will work and neither of them is deprecated.
For
a large site with the kind of issues you describe, I would expect this
overlap
to be quite long - at least a month, why not longer? This will greatly
simplify 
the coordination problem. 

In fact, a single homed site changing to a new provider would become
multihomed during the overlap period; and an n-homed site would become
(n+1)-homed during the overlap period. A good multi6 solution *is* a
renumbering mechanism.
  Brian

From: Iljitsch van Beijnum [mailto:[email-masked]]
 I disagree. I have personally renumbered two relatively small ISPs
(including customers!) a total of three times. That would be 5 - 20
routers and 10 - 40 servers.

When compared to a lazy afternoon of doing nothing, renumbering is a lot
of work. When compared to the routine maintanance that happens anyway
over
a period of several months, the added trouble of renumbering is fairly
negligible.

BTW: changing domains isn't much of a problem: just register a new
address
for your name server.

Iljitsch van Beijnum

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Mon, 29 Oct 2001 10:51:32 +0100 (CET)

> IPv6 will be easier) but all the associated host, server and security

Agree. So the people who make host, server and security products have
their work cut out for them.

> lmhosts files, that kind of stuff.

In my experience, the willingness to renumber has little to do with the
amount of work involved. I've seen massive organizations (not of the scale
you're talking about, but still very big for a single timezone) with many
hard to renumber items renumber without complaints, and fairly small
organizations with simple setups refuse to do so and keep their B block
even if they didn't even need a full /24.

But my real point is that renumbering is not a big deal compared to
maintanance work that has to be carried out anyway:

> And all of these guys have
> access-lists all over the place, and so do we.

And every time you get something new, these access lists have to change. I
used to work for the largest ISP here in The Netherlands, and we pretty
much had to change three access lists on all BGP speaking routers two or
three times a week.

> Even in a dream world

An afternoon is not a useful timeframe for renumbering. Either it has to
be done much quicker (30 seconds or so) or you can take much longer, up to
at least a month.

Is there no way we can come up with a way where hosts can keep their IPv4
address and happily run IPv4, where the other 96 bits are "automagically"
added and removed by a border router? That way, I can forever go on using
213.156.3.172, even if I have to renumber daily from
3ffe:1234:x::213.156.3.172 to 3ffe:1234:y::213.156.3.172 and so on.

It should be easy enough to do this for the local address, the only
problem is where to find the 96 missing bits of the remote address.

Iljitsch

---

From: Eric Gauthier <[email-masked]>
Date: Mon, 29 Oct 2001 15:35:17 -0500

> problem is where to find the 96 missing bits of the remote address.

My impression was that a system could request whatever it wanted to
as the end 64bits of its address and that it 'usually' chose its
MAC.  If that's the case, your system could chose 32-bits of zeros
and then the 32bit combination that corresponds to your IP...  Then,
the normal renumbering rules would apply?

Eric :)

---

From: Iljitsch van Beijnum <[email-masked]>
Date: Tue, 30 Oct 2001 09:29:14 +0100 (CET)

> the normal renumbering rules would apply?

What I want is for the host to use just the 32 bit IPv4 addresses. (The
host then wouldn't even have to run IPv6.) So 1.2.3.4 sends a packet to
5.6.7.8 and a border router would turn that into a packet from
3ffe:ab::1.2.3.4 to 3ffe:cd::5.6.7.8. This way, only the border routers
need to know the IPv6 prefixes and internal hosts can happily run IPv4 or
IPv6 with IPv4 addresses without ever having to renumber.

---

From: Brian E Carpenter <[email-masked]>
Date: Tue, 30 Oct 2001 11:15:21 +0100

Iljitsch van Beijnum wrote:
...
> IPv6 with IPv4 addresses without ever having to renumber.

Er, that can only work within a site; since we have run out of IPv4 addresses,
it can't cross the Internet in the general case. The general case requires
NAT-PT, and anyway you have not given the legacy hosts any benefit from
IPv6.

  Brian