SCION Inter-Domain Routing#

Tilmann Zäschke - ETH Zürich

• Why: SCION has crossed from research architecture to regulated critical-infrastructure deployments (Swiss banking, payments, healthcare, power). For anyone whose remit covers inter-domain security and next-gen network identity/trust, this is the most concrete clean-slate architecture actually in production.
• What: A 2026 status briefing by the ETH group. Trust model: Isolation Domains (ISDs) — groups of ASes with self-governed trust roots and no third-party CAs, ASes authenticated via X.509 certificates. Path-awareness: endpoints build end-to-end paths from beaconed segments and select among them (latency, bandwidth, geolocation — enabling geofencing and hijack prevention), with failover in ~RTT and concurrent multi-path use. Real deployments: SSFN (Secure Swiss Finance Network, ~300 finance institutions, governed by Swiss National Bank and SIX), SEPN (EFTPOS payments), HIN (healthcare), SSUN (planned all Swiss electricity market partners by 2030), SCIERA (research/education). Public network: 242 registered ASes, 98 publicly reachable, median 204 paths per destination (max 5,828); fastest path median 4 hops / 4.1 ms. Specs: data plane and control plane drafts are with the RFC editor (independent submission stream); reference implementation v0.15.0 adds NAT support; native SCION endhost apps expected to bring 100k+ native users by end of year; client libraries in Go, Rust, C, Java, Python, plus a Chromium plugin.
• How: Control plane: beacon service propagates path segments, path servers store them, certificate service manages inter-AS keys. Data plane: packets carry the end-to-end path; border routers forward per-path. Deployment needs no changes to intra-AS infrastructure; legacy endpoints attach via SCION gateways (SIGs) translating IP ↔ SCION.
• Where applicable: Inter-AS/critical-infrastructure connectivity — multi-ISP L2/L3 services with enforceable governance and path control. Not a DC fabric or general-Internet technology yet; the deployment footprint is heavily Swiss/European, and the ecosystem is still anchored on ETH tooling and Anapaya as the commercial vendor.