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Comment by eps | Hacker News Reader

Add UDP relays and TCP hole punching and it'll finally be a better take on Hamachi :)

If you read the article, it seems like it has both of those features, though I'm not sure what exactly you mean by "UDP relay".

It has neither.

(Tailscale employee here) UDP relays - that's roughly our DERP relay network. It currently operates over HTTPS because that's the last-resort "most likely to work in hard networks" transport, but adding a UDP option for efficiency is in the books.

TCP hole punching - I don't understand this, can you elaborate? By running Tailscale you can just talk to the machines on your Tailscale network, no hole punching required. At the transport layer we might do NAT traversal shenanigans to get the mesh network up, but that's invisible to the "user layer". I'm guessing you mean something slightly other and I'm just not parsing correctly?

Relays are helpful not only when UDP is blocked, but also when both nodes are behind NAT that does random port overloading and port prediction doesn't work.

TCP hole punching uses symmetrical TCP open trick to establish a proper TCP session between nodes each behind its own NAT. Roughly the same idea as with UDP h/p, but requires a coordinating server to make it work. Useful for cases when UDP punching doesn't work or when UDP is blocked completely.

Oh, that kind of TCP hole punching. No, we don't do that, because we run over UDP only. So far, I don't think we've seen network conditions where UDP is blocked but the NAT is friendly enough to permit TCP traversal (same problems as UDP traversal, only with extra state to manage). I suppose we might get to it eventually, but there's a lot of simpler cases we can handle better first :)

Hamachi was amazing. Just amazing. What.. 15 years ago? I still miss it after LogMeIn bought them.

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