[gzread]

The hole punching is so much simpler because you don't need to guess your own address and port - you just know it

[ranger_danger]

Doesn't that assume that your machine is given its own world-routable (and unfiltered) v6 address?

[gzread]

That's how it works in ipv6. If your network doesn't give you an address, it's broken. We do not assume unfiltered since we are talking about hole punching.