* William Herrin
T-Mobile uses something called 464XLAT. Don't let the "translation" part fool you: it's a tunnel. IPv4 in one side, IPv4 out the other.
464XLAT is not a tunnel. Protocol translation is substantially different from tunneling. With tunneling, the original layer-3 header is kept intact as it is encapsulated inside another layer-3 header. With translation, the original layer-3 header is removed and replaced with another layer-3 header. They come with a different set of trade-offs, such as: - Protocol translation may be lossy (e.g., exotic IPv4 options may not survive the translation to IPv6 and would therefore not reappear after translation back to IPv4). Tunneling, OTOH, is not lossy. - Tunneling moves the original layer-4 header into another encapsulation layer, so e.g. an ACL attempting to match an IPv6 HTTP packet using something like "next-header tcp, dst port 80" will not work. With translation, it will.
Kabel Deutschland uses something called "Dual Stack Lite." It's also a tunnel: the Kabel-owned CPE encapsulates the customer's IPv4 packets within IPv6 and delivers them to the Kabel's IPv4 carrier NAT box.
Yep. DS-Lite is indeed tunneling.
So sure, if you don't mind dissembling a little bit you can say that they moved their "infrastructure" to IPv6-only. In my mind, tunnelling IPv4 over IPv6 where it both enters and exits the carrier's area of control as an IPv4 packet doesn't count as "IPv6-only."
I guess we disagree about the definitions, then. In my view, a dual-stack network is one where IPv4 and IPv6 are running side-by-side like "ships in the night" with no fate sharing. You might be running two different IGP protocols (like OSPFv2 and OSPFv3) and a duplicated set of iBGP sessions. ACLs and the like must exist both for IPv4 and IPv6. And so on. If you turn off one protocol, and the other one keeps on running just like before. This is in contrast with a single-stack network; turn off that single stack, and nothing works. That doesn't mean that cannot simultaneously transport other layer-3 protocols across that single-stack network; just that there is a clear distinction between which is the main layer-3 protocol and others being transported across it. You might very well simultaneously transport IPv6, AppleTalk, and IPX/SPX across an IPv4-only network - but that doesn't mean that the network is "quad-stack" - IMHO, it's still single-stack IPv4.
On Fri, Jan 30, 2015 at 11:44 AM, Tore Anderson <tore@fud.no> wrote:
If everyone could just dual-stack their networks, they might as well single-stack them on IPv4 instead; there would be no point whatsoever in transitioning to IPv6 for anyone.
What do you mean "if"? Carrier NAT means we *can* single-stack on IPv4 for the next 20 to 30 years, if we're so inclined.
I suppose that's true - if you ignore that a number of other folks are deploying IPv6 to deal with their IPv4 exhaustion, and that products and services are being put to market that recommends the use of IPv6 connectivity above NATed IPv4 (e.g., Xbox One). So much earlier than 30 years from now you'll be wanting to have IPv6 in your network anyway, and once you come to that realisation you might also realise that operating a dual-stack network for those 30 years is not going to be any fun at all due to the increased complexity it causes. Especially if the IPv4 part of that dual-stack network is in itself getting increasingly complex due to more and more NAT being added to deal with growth. So IMHO dual-stack is a bad recommendation, or at least it is rather shortsighted. If you're in a position to do single-stack IPv6-only with IPv4 as a service (like T-Mobile USA or Kabel Deutschland), you'll end up with a much simpler network that it'll be much easier to maintain over the years. This also facilitates the use of IPv4 address sharing solutions like lw4o6 and MAP, whose stateless nature makes them vastly superior to traditional stateful Carrier Grade NAT44 boxes. YMMV, of course. Tore