Proposal: Native SCION Transport & Multipath Support

Hi everyone,

We have developed a native transport for SCION (a path-aware, next-gen Internet architecture) in go-libp2p. We want to align with the core team before opening a PR, as our implementation introduces some unique multipath behaviors.

1. SCION Addressing (Multiaddr)

To enable dialing and listening on SCION, we have defined a new multiaddr format that encapsulates the SCION ISD-AS (Isolation Domain - Autonomous System) identifier.

Format: /scion/<ISD-AS>/<Host-Multiaddr>

Example:
For a node in ISD 19, AS ffaa:1:f, wrapping a standard UDP/IP endpoint:

/scion/19-ffaa:1:f/ip4/10.0.0.1/udp/123

Status:

• We have registered the codec in multicodec PR #325.
• We have submitted a PR to implement this in go-multiaddr: multiformats/go-multiaddr#285.
• Note: The merge of the go-multiaddr PR is currently a blocker for opening our PR against go-libp2p, as the transport relies on validation logic within that library.

2. Multipath Transport (QUIC)
To leverage SCION's multipath capabilities, our transport differs from standard QUIC:

• Path Pinning: Instead of migrating a single connection, we establish distinct QUIC connections for each available SCION path.
• Pooling: These connections are pooled to allow upper layers (like Bitswap) to stripe requests across multiple paths simultaneously.
• Current Code: netsys-lab/go-libp2p/feature/scion-quic-transport, needs to be rebased on newest version of go-libp2p

Questions for Maintainers:

1. Architecture: Do you see any issues with our "connection pooling" approach (multiple physical connections per logical peer) fitting into the current Transport interfaces?
2. Dependencies: Since we rely on the unmerged go-multiaddr PR, what is the preferred workflow for proposing the transport implementation here?
3. External Components: Any concerns regarding a transport that relies on communication with a local daemon (the SCION dispatcher)?

Thanks!

Start by reviewing the go-libp2p Transport interfaces and the netsys-lab/go-libp2p feature/scion-quic-transport branch, then inspect the linked go-multiaddr and multicodec PRs. Determine whether pooled QUIC connections, SCION dispatcher communication, and the dependency workflow fit the project; done requires maintainer agreement on the architecture and integration path.