That is awfully expensive for something ipv6 already solves minus the privacy part. I don't see how it can be considered "huge". A slight convenience maybe?
Also, routing everything through a 3rd party is a massive downside.
Here’s the attack:
- You want to get to A
- And you’re on a device B that has access to hole-punch-as-a-service but no direct access to A. Good network administrator / sysadmin!
- Attack NDP (ie ARP spoofing but IPv6 flavored) to trick the firewall just for a moment that you’re A [1] and request the port be opened to your evil server C on the public internet.
- Oops.
EDIT: I agree we definitely need something like UPnP, or maybe even UPnP itself, but it's another adoption problem currently.
AFAIK it doesn't use third party servers and it seems to get through any router just fine...
This can have quite an effect on sync speed. I set it up for my dad and initially his PC and laptop were syncing incredibly slowly. It turned out they both thought his home network was a public one, so everything was going out to a relay server and back.