Problems with removing NAT from a network

Dan Wing dwing at
Fri Jan 7 10:33:58 CST 2011

> On 1/6/2011 9:28 PM, Dan Wing wrote:
> >> -----Original Message-----
> >> From: Matthew Kaufman [mailto:matthew at]
> >> Not really. Imagine the case where you're on IPv6 and you can only
> >> reach
> >> IPv4 via a NAT64, and there's no progress made on the detection
> >> problem.
> >> And your family member is on a Skype-enabled TV plugged into an
> >> IPv4-only ISP.
> >>
> >> Now you can't get a direct media path between you, even though their
> >> ISP
> >> is giving them IPv4 and your ISP is *claiming* you can "still reach
> the
> >> IPv4 Internet".
> >>
> >> Skype can still make this work by relaying,
> > Skype could make it work with direct UDP packets in about 92% of
> > cases, per Google's published direct-to-direct statistic at
> >
> >
> If one end is behind a NAT64 and there is no mechanism for discovering
> the NAT64's IPv6 interface prefix and mapping algorithm (and at present
> there is not), there is no way to send IPv6 IP packets from the
> IPv6-only host to IPv4 literal addresses (that is to say, addresses
> learned via a mechanism other than DNS responses synthesized by the
> DNS64 part of the NAT64 "solution") on the IPv4 Internet through said
> NAT64.
> That's the case we're discussing here.

There are a bunch of ideas for how to accomplish that.  Several of
the ideas don't require any support by the network infrastructure,

> It breaks Skype, Adobe's RTMFP, BitTorrent, ICE-based NAT traversal,
> etc. Even the protocol described in the referenced document, Jingle (as
> it essentially uses ICE) fails. The candidate IPv4 addresses for the
> end
> that's on the IPv4 Internet (local and STUN-derived) that are delivered
> over Jingle's XMPP path cannot be used by the host that is on IPv6 +
> NAT64 to reach the IPv4 Internet because it has no IPv4 sockets
> available to it and even if it knew that NAT64 existed (which would
> take
> a modification to the Jingle-based apps) and opened an IPv6 socket it
> wouldn't know what IPv6 address to use to reach the IPv4 host because
> there's no discovery mechanism. If you want we can take this back to
> the BEHAVE list now.



> Matthew Kaufman

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