Network architecture
The same execution substrate is deployed in two tiers: a canonical ledger operated by accredited validators, and closed subnets run by banks and consortia. Both anchor to the same Bitcoin chain, so the audit trail of the entire network, canonical and closed, is enumerable from public data.
#Two tiers
- The canonical ledger is the flagship SQRL instance. It is operated by a named set of accredited validators and carries the shared contract registry, the subnet registry and the public asset layer. See Validators and the canonical ledger.
- Subnets are independent SQRL instances run from the same codebase by a bank or consortium. Members hold full subnet state, outsiders see only Bitcoin-anchored commitments, and membership in the wider network comes from registering periodic checkpoints on the canonical ledger. See Subnets and routing.
The same node binary runs the canonical ledger and every subnet: a subnet is a configuration of the stack, not a fork of it.
#The four layers
| Layer | Contents | Permission |
|---|---|---|
| Bank applications | Stablecoins and deposit tokens, bonds and funds, FX corridors, client wallets | Gated |
| Lightning distribution | Partner-run hub nodes, multi-asset channels, AMMs for in-flight FX | Curated |
| SQRL execution | Validator seats, subnets, XRB-settled fees, observer nodes, issuer whitelists, post-quantum attestation and transport | Permissioned |
| Bitcoin settlement | Anchoring, ordering, finality and the public audit trail | Permissionless |
#What stays open, and what is gated
Open: Bitcoin settlement and the complete audit trail; the protocol source, with the reference node MIT licensed; the free T0 execution envelope, under which simple operations such as token transfers stay free; and the XRB market. Anyone can verify the network from the Bitcoin chain alone, run a node from source, and replay the state.
Gated: validator seats and state-root attestation on the canonical ledger; deployment above the free tier; subnet membership and checkpoint registration; cross-subnet routing standing; the AMM operator set; and admission to partner programmes.
Key takeaway
Permission is a property of the execution and governance layers only. If settlement or the token market were gated too, SQRL would be a consortium chain, so that boundary is a design invariant, not a policy.