[Kazik24]

Excuse me if this is explained somewhere, but how does noq/iroh relays QUIC packets between peers? How does relay know which QUIC packets it receives should be sent where, since QUIC is famously hard to track? Do you stream to relay new/retire_connection_id packets through different connection so that it can link them to specific peers? Or is the relayed QUIC wrapped in different protocol?

[matheus23]

noq doesn't implement any relaying logic itself. From the perspective of noq, iroh relays are another IP subnet that it's sending packets to and receives packets from, so just another path.

> Or is the relayed QUIC wrapped in different protocol?

Yes, that's what's happening.

On the iroh/iroh-relay side, we implement this relaying using WebSockets. The datagrams are wrapped with a header saying which EndpointId (ed25519 public key) we want the packet to be relayed to. Because of a handshake between iroh clients and iroh relays, the relay knows and has authenticated the source EndpointId of datagrams it relays.

So yeah, we're tunneling QUIC datagrams through HTTPS over TCP (we encrypt twice). The relay really is just a fallback and for coordination. We specifically made these choices for maximum ubiquity for the fallback (not affected by UDP blocking, looks like "normal" traffic).