Subject: RE: (ngtrans) 6to4

From: Richard Draves <[email-masked]>
Date: Wed, 17 Feb 1999 12:51:39 -0800

>    So if there are a small number of well-known gateways to 
> which 6to4 sites
>    can direct traffic to reach the 6ren, it should be OK. It 
> will not introduce
>    the same kinds of problems seen with configured tunnels in 
> the 6bone. If we
>    allow NUD over 6to4 it would be easy to find a working 
> gateway should one go
>    down.
>    
> => you don't need NUD, only dynamic routing: BGP can/will do it.

Hmm, I don't know enough about BGP to respond very well to this. I guess I
assumed BGP requires peer routers to be configured to know about each other.
In the scenario above, the well-known gateways would not know about all the
6to4 sites sending packets to them.

>  - the standard solution will be to use one part of the embedded IPv4
>    address for routing with the danger to inject a large part of the
>    IPv4 routing table/mess into the IPv6 world.
> For me the second issue is the reason why IPv4 embedded 
> addresses are BAD
> (the IPv4 compatible IPv6 address story has already shown this,
> fortunately they are no more considered as a device to use today)!

Yes, it would be bad to inject the v4 routing table into the v6 world. I
don't see that this would happen. Consider a v6-only node sending to a a
6to4 destination. The packet gets routed based on the 6to4 prefix to the
closest dual-stack router. (Probably a border gateway for the site, if not
closer.) As soon as it reaches the dual-stack router, then packet can be
encapsulated and the v4 infrastructure will route it to the destination
site. The packet won't need to travel very far, with a choice of directions
that would require more granular v6 routing, before being encapsulated.

I guess it does come down to a disagreement over whether the migration to v6
is more likely to happen from the edges or from the core. I'm convinced that
the v4 internet will not be supplanted quickly, and we're best off making v6
run really well over the v4 internet. Maybe in 20+ years v4 will be
sufficiently irrelevant to die off.

Rich