NAT v6->v4 and v4->v6 (was Re: WG Action: Conclusion of IP Version 6 )

Mark Smith nanog at
Sun Sep 30 02:10:23 UTC 2007

On Sat, 29 Sep 2007 15:37:50 -1000
Randy Bush <randy at> wrote:

> > The model isn't very new at all.
> no it isn't.  many of us remember atm-1, so atm-2 is no big surprise.

I'd argue it's not the quite same situation. From what I understand of
the way ATM/IP was deployed (ATM core, IP routers at the edge with
direct IP adjacencies over ATM PVCs), the ATM topology wasn't visible
to the IP layer. The IP layer then wasn't able to make informed path
decisions for IP traffic, yet it had no choice but to take
responsibility for choosing those forwarding paths, because that's it's

The model we're talking about seems to me to be that old model on
it's head. The devices at the edge of the core network are fully aware
of the underlying topology of the core network so they can make
informed forwarding decisions. The tunnelling encapsulation only serves
the purpose of transporting protocols/payloads, that aren't native in
the core, from edge-to-edge. The tunnelling function doesn't try to
control or have to take responsibility for the selecting paths taken
across the core.



        "Sheep are slow and tasty, and therefore must remain constantly
                                   - Bruce Schneier, "Beyond Fear"

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