Subject: Re: IPv6 Multi-homing BOF at NANOG 35

From: Dan Lanciani <[email-masked]>
Date: Thu, 13 Oct 2005 16:38:16 -0400 (EDT)

Paul Jakma <[email-masked]> wrote:

|On Mon, 10 Oct 2005, Brian E Carpenter wrote:
|
|> The point of shim6 is to *avoid* the need for PI-like space for 
|> multihomed sites, so that we don't do to the IPv6 BGP table what 
|> multihoming is doing to the IPv4 BGP table. We need IPv6 to scale 
|> vastly more than IPv4, so this is essential.
|
|The problem isn't PI addressing, it's advertising tiny prefixes in 
|the routing table. PI addressing *without* global-routing-table 
|visibility *would* obviously scale for routing. We just don't have a 
|way to do this.

We might have a way to do it by fully separating locators and identifiers,
but it would require pervasive changes to existing implementations and a
new economic model for address allocation.  Shim6 leverages a partial
separation of locators and identifiers to provide a solution to a somewhat
limited problem space while still requiring pervasive changes to existing
implementations, but it does preserve the economic model.

My concern is that adoption of shim6 will be an impediment to development
of a more general locator/identifier separation solution both because the
mapping functions might clash and because many will object to changing
existing implementations a *second* time for what might be perceived to be
only a marginal gain for users (and possibly even a loss for providers).

|> I hope the proposed BOF will make this clearer. I personally think 
|> that shim6 will be really cool for ISPs, although as Geoff says it 
|> will take a while to deploy and during that time we'll need a 
|> PI-like approach.
|
|We'll always need PI. The Independence part of PI is what people 
|/really/ want. They don't want multiple-PA (they can do that already 
|relatively easily). If people can not get globally-unique PI 
|addresses they will use private PI space and use address translation.

Indeed.  NAT is simply a response to the economic models of address
allocation.  Any technical "solutions" that perpetuate those models
will also perpetuate the demand for NAT.

				Dan Lanciani
				ddl@danlan.*com

--------------------------------------------------------------------
IETF IPv6 working group mailing list
[email-masked]
Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6
--------------------------------------------------------------------

---

From: Brian E Carpenter <[email-masked]>
Date: Fri, 14 Oct 2005 13:44:17 +0200

...
> only a marginal gain for users (and possibly even a loss for providers).

I believe that a true id/loc split is a much more fundamental change
than IPv4 to IPv6 and on a completely different scale of cost and decade.
...
> will also perpetuate the demand for NAT.

The smallest allocation granularity for IPv6 is supposed to be a prefix,
not an address, for that reason.

    Brian