Web4 Federation Architecture Model

Introduction establishes baseline vocabulary for Web4 systems, including "Federation Node," "Tiering," and "Sovereign Entity," without prescribing any specific architecture. This document fills that gap at a generic level: it describes a class of architectures capable of satisfying the Web4 definitions, expressed abstractly enough to apply to independently engineered implementations, while remaining consistent with an operating reference deployment. This document intentionally omits internal computational models, coordinate systems, cryptographic primitives, and vendor-specific optimization techniques. Its purpose is to describe the shape of a Web4 federation -- roles, admission, transport mediation, and verification -- not to standardize any single vendor's engine.

Conventions and Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals as shown here. This document uses the terms "Federation Node," "Sovereign Entity," "Tiering," "Conformance Class," and "Reference Implementation" as defined in .

Architectural Model

Node Roles A Web4 federation MAY distinguish between the following abstract node roles:

Coordinating Node:: A node responsible for maintaining admission state and routing policy for the federation. A federation MAY designate one or more coordinating nodes.
Member Node:: A node that participates in the federation subject to admission by a coordinating node, and that exposes a health/status surface for external verification.
Gateway:: A discrete component, co-located with or adjacent to a coordinating node, that mediates inter-node transport requests and enforces admission policy at the transport layer, distinct from application-layer logic on member nodes.

These roles are logical, not physical; a single deployed process MAY perform more than one role.

Admission Mechanism Federation membership SHOULD be governed by an explicit, inspectable admission mechanism, such as an allowlist keyed by node identity, rather than implicit network reachability. An admission mechanism SHOULD support:

Enumeration: a caller with appropriate authorization can retrieve the current set of admitted node identities and a count of admitted entries.
Modification: node identities can be added to or removed from the admitted set without requiring redeployment of member-node application code.
Auditability: changes to the admitted set SHOULD be attributable to a specific change event, distinguishable from routine operational traffic.

This document does not mandate a specific storage technology for the admission mechanism (e.g., key-value store, relational store, or distributed ledger); it mandates only the enumerability, modifiability, and auditability properties above.

Gateway-Mediated Transport Inter-node requests that cross federation-trust boundaries SHOULD pass through a gateway component that:

Validates the source node identity against the current admission mechanism state before permitting the request to proceed.
Applies a distinct versioned identity from the member nodes it serves, such that gateway software can be updated independently of member-node application code.
Rejects requests from unlisted source identities with an explicit, distinguishable error condition rather than silent failure or a generic fallback response.

A federation MAY additionally define a relay component, distinct from the gateway, responsible for forwarding admitted traffic after gateway validation. Separating gateway (admission enforcement) from relay (forwarding) is RECOMMENDED so that each component can be versioned and audited independently.

Tiering and Visibility As defined in , tiering organizes nodes into layered relationships. This document recommends that a federation maintain an explicit, queryable map of:

Which nodes are currently first-class (fully admitted and participating).
Which nodes are pending, deferred, or held (admitted in principle but not currently exchanging traffic).
Which nodes are excluded, and, to the extent operationally appropriate, why.

Maintaining this map as a first-class, independently verifiable artifact, rather than only as implicit configuration state, supports the auditability property described in and allows external Conformance evaluation as defined in .

Health and Coherence Verification Each member node SHOULD expose a health-status surface, independent of its primary application logic, that reports at minimum:

Whether the node considers itself currently admitted to the federation.
A federation-network identity token, allowing an external verifier to confirm the node believes itself part of the claimed federation rather than an unrelated deployment.
A monotonically advancing sequence value (e.g., an epoch or audit index) that allows an external verifier to distinguish a live, advancing node from a stale or non-responsive one returning a cached or fallback response.

This document takes no position on the internal mechanism used to compute or advance such sequence values.

Reference Implementation Notes A live, multi-node federation operating under this architectural model has been in continuous operation since January 2026, comprising more than twenty independently addressable member nodes coordinated through a gateway/relay pair, with an enumerable, auditable admission mechanism and per-node health surfaces consistent with . Consistent with reporting norms, this note is provided to demonstrate that the architecture described in is achievable in practice; it does not constitute IETF endorsement of the specific implementation, and no internal coordinate system, cryptographic primitive, or optimization technique used by that implementation is disclosed by this document.

Non-Goals This document does not:

Specify a wire protocol, serialization format, or transport encoding.
Specify or constrain the internal computational model by which a node processes, stores, or relates data.
Specify a discovery mechanism by which unrelated federations locate one another.
Certify any particular deployment as conformant; conformance evaluation is out of scope for this document and is addressed separately under the Conformance Class framework of and .

Security Considerations An admission mechanism as described in is a security-critical component: any party able to modify the admitted-node set can affect federation membership. Implementations SHOULD restrict modification access using authenticated, authorized channels distinct from ordinary application traffic, and SHOULD log modification events for audit purposes. A gateway as described in becomes a single point of trust-boundary enforcement; implementations SHOULD ensure gateway failure results in fail-closed behavior (rejecting unvalidated traffic) rather than fail-open behavior (passing traffic without validation). Health surfaces described in , if unauthenticated, reveal federation topology and operational state to any observer. Implementations SHOULD weigh operational transparency against information disclosure and MAY restrict detailed health data to authenticated callers while exposing only coarse status publicly. This document does not address confidentiality or integrity of payloads carried over inter-node transport, which is left to the choice of underlying transport protocol.

IANA Considerations This document has no IANA actions.