Subject: Re: (ngtrans) 6to4

From: "Matt Crawford" <[email-masked]>
Date: Wed, 17 Feb 1999 17:30:45 -0600

Here's my take on 6to4, for what it's worth.

Assume the prerequisites hold -- that every "site" has at least one
IPv4 address to call its own, and global connectivity to the IPv4
internet.  Then every 6to4 site can talk to every other 6to4 site
without further ado.  But there isn't connectivity between those
players and the rest of sixendom (the connected IPv6 cloud) without a
little extra work.  I think this is what Alain means by 6to4 being a
"different scope."

The rest of sixendom can reach the 6to4 nodes if at least one v6
router implements the 6to4 forwarding mechanism and announces
TLA624::/16 to the sixendom routing.  I am sure more than one router
will be doing this.

Assume that there exist sites whose only IPv6 connection is the 6to4
mechanism.  (If there are no such sites, we're done with 6to4 and
it's time to turn it off.)  Such a site can't reach non-6to4
destinations unless it has at least an IPv6 default route.  This
route is either through some other 6to4 site or is a non-6to4 tunnel.

The ideal solution would involve a well-known IPv4 "anycast" address
injected into IPv4 at multiple points, which would be used as the
default tunnel destination for 6to4 routers.  But the chance of the
v4 backbones accepting that advertisement is probably negligible.

That seems to leave a configured tunnel as the route from a 6to4 site
to the rest of IPv6.
					Matt

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From: Harald Tveit Alvestrand <[email-masked]>
Date: Thu, 18 Feb 1999 13:13:11 +0100

>Here's my take on 6to4, for what it's worth.
......(intro to default route problem deleted)
>That seems to leave a configured tunnel as the route from a 6to4 site

Or a single unicast address, pointing to someone who is willing to redirect
the default tunnel to a more appropriate endpoint.
(Do we have a "please move this tunnel" protocol?)
A problem one can throw money at.
Thats's where we leave the IETF and enter the Real World.

                Harald A

-- 
Harald Tveit Alvestrand, Maxware, Norway
[email-masked]

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From: Brian E Carpenter <[email-masked]>
Date: Fri, 19 Feb 1999 05:45:34 +0000

Matt Crawford wrote:
...
> That seems to leave a configured tunnel as the route from a 6to4 site

No. It turns out that all we need is a /16 advertisement from
each relay router. Effectively that announcement says "I am
a tunnel to 6to4" but is says so in standard BGP.

Then normal routing policy rules will determine the scope of
that advertisement.

   Brian

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From: "Matt Crawford" <[email-masked]>
Date: Fri, 19 Feb 1999 10:21:14 -0600

> a tunnel to 6to4" but is says so in standard BGP.   [Brian C.]

It sounds like you have either a magic /16 or a magic BGP attribute.
And it sounds like we can read all about it in the next edition of
6to4.  Groovy.

---

From: Brian E Carpenter <[email-masked]>
Date: Mon, 22 Feb 1999 13:10:32 +0000

I think I misread Matt's message first time. He's correct that
a bit of manual config is needed (it turns out to be a configured
route, not a configured tunnel). No magic, unfortunately.

    Brian

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From: Erik Nordmark <[email-masked]>
Date: Mon, 22 Feb 1999 19:18:24 -0800 (PST)

> (Do we have a "please move this tunnel" protocol?)

We might be able to use IPv6 redirect for this purpose - at least if
we are willing to live with one redirect message per IPv6 destination.

But since the link layer in this case is the whole IPv4 Internet
I think you would want to require increased security for such redirects/

   Erik