iroh is a library to establish peer-to-peer QUIC connections assisted by relay servers. It needs to route UDP datagrams carrying QUIC payloads over relayed and holepunched network paths. While this used to be done outside of QUIC's knowledge, over the past year we have worked to adopt the QUIC multipath proposed standard so that QUIC itself is aware of multiple paths.

This talk will cover iroh's experience of adding QUIC multipath to the Quinn library and the challenges of adopting it. The multipath draft does only cover how to send packets over the wire, and does not specify how path selection works, consequently we'll also cover iroh's choices for path selection as well as changes we will still be experimenting with.

Finally iroh has also moved holepunching into a QUIC extension, which integrates tightly with multipath. The mechanism of how holepunching with multipath support works in iroh will covered as well.