So, what is DERP and its "regions"?

[Winterhuman]

From what I understand, DERP is a STUN and TURN-style relaying protocol borrowed from Tailscale. What I don't understand is what DERP regions are and why, or if, they're required or recommended; what functionality does it provide?

[Winterhuman]

@b5 Friendly ping (not sure who to ping specifically about the DERP parts of the codebase)

[flub]

The current derp regions design is copied directly from tailscale, which is an entirely closed system. We want to enable anyone to run their own derp servers and I don't think we've entirely figured out how derp regions should work in that respect.

Having said that, derp regions as they are now are:

• Each region can be thought off as one logical derp server (though there could be multiple meshed derp servers handling a region).
• Derp servers do not mesh between regions.
• Each iroh node has a home derp region (if derp is enabled).
  • It connects to this when it is accepting new connections.
• To contact an iroh node you need (derp_region, peer_id).
  • Regadless of your own derp region, you connect to dial a peer you connect to the derp region of the peer.
  • This derp server will do all the connection establishment and holepunching for you.

However right now regions are only identified by a u16 which is a bit poor for the goal of letting anyone run their own network I think. We'll have to figure these out better.