Why do they feel the need to call NAT64 by some new weird “4via6” name?
bradfitz · 1h ago
I'm largely responsible for this, so I'll try to answer.
Technically it's not NAT64 today. Different prefix for one, but it's also not translated at the IP layer (yet). For TCP, we terminate the TCP in tailscaled and make a new TCP connection out and switch them together, so packets are not 1:1 end-to-end.
We also had grander plans for the 32 "site-id" bits in the middle there. Instead of just a 8-bit (now 16-bit) "site ID" number in there, you could actually put the 32-bit CGNAT IPv4 address of any peer of yours, and then access its IPv4 space relative to that node, without any configuration.
Say you have an Apple TV plugged in at home.
Then you're at a coffee shop and want to access something on your LAN and don't have a subnet router set up.
You should be able to `ssh 10-0-0-5-via-appletv.foo-bar.ts.net` and have MagicDNS map that "appletv" as the "Site ID" and put its 32-bit CGNAT address in, and then parse out the 10.0.0.5 as the lower 32-bits, and then have Tailscale route your packets via your home Apple TV node.
All subject to ACLs, of course, but we could make it a default or easy-to-enable recommended default that you could do such things as an admin for your self-owned devices.
So why it's called "4via6"? That was just kinda a temporary internal name that ended up leaking out to docs/KB and now a blog post, apparently. :)
Sesse__ · 1h ago
> Technically it's not NAT64 today. Different prefix for one, but it's also not translated at the IP layer (yet).
Different prefix? You can run NAT64 with any prefix you'd like (well, as long as it's at least a /96); the “well-known” 64:ff9b::/96 prefix isn't mandatory at all (you typically send down the prefix either through DHCPv6 or in a special RA sub-option), and was standardized long after NAT64.
But OK, it's basically a less-capable NAT64 that doesn't work with UDP or even ping?
> We also had grander plans for the 32 "site-id" bits in the middle there. Instead of just a 8-bit (now 16-bit) "site ID" number in there, you could actually put the 32-bit CGNAT IPv4 address of any peer of yours, and then access its IPv4 space relative to that node, without any configuration.
OK, so those plans were basically 6rd? (Or 6to4, if you want.)
> So why it's called "4via6"? That was just kinda a temporary internal name that ended up leaking out to docs/KB and now a blog post, apparently. :)
You are aware that the name is already in use for something else entirely, right? (Basically 4rd + 464XLAT.)
bradfitz · 42m ago
> that doesn't work with UDP or even ping?
I never said it didn't work with UDP or ping. I described what it does differently for TCP.
Anyway, I'm sorry we offended you with its name.
I personally think it would've been more offensive to use an existing spec name and then not implement the spec of that name perfectly. (which is likely if our needs/goals only 90% overlap with the spec we pick)
At least if we screw up this implementation, we didn't tarnish anybody else's spec or its name.
ko_pivot · 1h ago
Most people working outside the network layer are not familiar with the basics of IPv6 and how it interops with v4 systems. In fact, I would bet that many AWS admins are not familiar with dualstack VPC configurations, for example. This product name communicates clearly to those users what the value prop is.
Sesse__ · 1h ago
How does inventing a new name that nobody else uses help new users? Are you saying that the name is dramatically much better and that guessing what 4via6 would be is significantly simpler than guessing what NAT64 would be? (I certainly couldn't guess it until I read through the entire blog post and saw the addressing part at the bottom, but maybe I don't have an AWS admin mind.)
danielbln · 1h ago
As far as I understand it, both involve translating between IPv6 and IPv4, but NAT64 is a broad standard for general IPv6-to-IPv4 internet access, whereas Tailscale's 4via6 is more specific feature to solve a niche problem of overlapping private IP ranges within a Tailscale VPN environment using some proprietary addressing scheme. But it's been a while since I was deep in network land.
SparkyMcUnicorn · 1h ago
Maybe because it's not exactly NAT64, even though it has the same goal?
kingforaday · 1h ago
Don't forget 6to4 and Teredo. Different names for different things.
Arnt · 3h ago
Reminds me of the network a friend described. After a couple of mergers and sales, they had so much NAT that one particular cron job tab used an internal server-to-server connection that passed through five NAT instances.
And this tailscale product seems to say "this product makes that kind of situation less awful" which I'm sure is somehow good but I can't help thinking that "less awful" is going to mean "still awful" for most deployments.
Technically it's not NAT64 today. Different prefix for one, but it's also not translated at the IP layer (yet). For TCP, we terminate the TCP in tailscaled and make a new TCP connection out and switch them together, so packets are not 1:1 end-to-end.
We also had grander plans for the 32 "site-id" bits in the middle there. Instead of just a 8-bit (now 16-bit) "site ID" number in there, you could actually put the 32-bit CGNAT IPv4 address of any peer of yours, and then access its IPv4 space relative to that node, without any configuration.
Say you have an Apple TV plugged in at home.
Then you're at a coffee shop and want to access something on your LAN and don't have a subnet router set up.
You should be able to `ssh 10-0-0-5-via-appletv.foo-bar.ts.net` and have MagicDNS map that "appletv" as the "Site ID" and put its 32-bit CGNAT address in, and then parse out the 10.0.0.5 as the lower 32-bits, and then have Tailscale route your packets via your home Apple TV node.
All subject to ACLs, of course, but we could make it a default or easy-to-enable recommended default that you could do such things as an admin for your self-owned devices.
So why it's called "4via6"? That was just kinda a temporary internal name that ended up leaking out to docs/KB and now a blog post, apparently. :)
Different prefix? You can run NAT64 with any prefix you'd like (well, as long as it's at least a /96); the “well-known” 64:ff9b::/96 prefix isn't mandatory at all (you typically send down the prefix either through DHCPv6 or in a special RA sub-option), and was standardized long after NAT64.
But OK, it's basically a less-capable NAT64 that doesn't work with UDP or even ping?
> We also had grander plans for the 32 "site-id" bits in the middle there. Instead of just a 8-bit (now 16-bit) "site ID" number in there, you could actually put the 32-bit CGNAT IPv4 address of any peer of yours, and then access its IPv4 space relative to that node, without any configuration.
OK, so those plans were basically 6rd? (Or 6to4, if you want.)
> So why it's called "4via6"? That was just kinda a temporary internal name that ended up leaking out to docs/KB and now a blog post, apparently. :)
You are aware that the name is already in use for something else entirely, right? (Basically 4rd + 464XLAT.)
I never said it didn't work with UDP or ping. I described what it does differently for TCP.
Anyway, I'm sorry we offended you with its name.
I personally think it would've been more offensive to use an existing spec name and then not implement the spec of that name perfectly. (which is likely if our needs/goals only 90% overlap with the spec we pick)
At least if we screw up this implementation, we didn't tarnish anybody else's spec or its name.
And this tailscale product seems to say "this product makes that kind of situation less awful" which I'm sure is somehow good but I can't help thinking that "less awful" is going to mean "still awful" for most deployments.