> UDP-based protocols are well suited for P2P, since hole punching is straightforward if you have predictable port mapping, you cannot disallow it.

... how does that work when the network disallows UDP altogether?

▲

octoberfranklin 14 hours ago | parent [-]

That is not as common as you think, and will get less common as QUIC grows in popularity.

If you're really really desperate you can send UDP packets with fake TCP headers (i.e. you aren't actually doing any congestion control or retransmission) but you have to control both ends of the connection for that.

And there's ICMP.

	▲	bnjms 11 hours ago \| parent [-]
		Blocking UDP to Outside and non-ping udp to Outside is common. It will remain common as long as servers fall back. And exceptions will be made for problem domains.