Spec-12-HLC-Bounded-Skew
What this spec defines
Bounds for remote Hybrid Logical Clock values accepted during federation ingest. Limits how far a remote HLC may advance local ordering relative to the receiver's wall clock and policy.
Extraction status
This file contains the ADR-020 §9 (modular specs) prose extraction for R-19
bounded-skew behavior. The basic HLC field and local advance rules
live in Spec-01-Fact-Model; federation ingest context lives in
Spec-05-Federation-Trust.
Purpose
HLC values preserve causal ordering, but accepting arbitrarily far-future remote HLCs lets a peer distort ordering and conflict resolution. Bounded skew limits how far a remote HLC may advance local ordering.
Inbound bound
On federation ingest, a node MUST compare the inbound fact's HLC wall component against its current wall clock. If the inbound HLC exceeds the configured bound, the node MUST reject or quarantine the fact according to local policy.
Default production posture: reject excessive skew.
Development deployments MAY choose warn/quarantine modes when explicitly configured.
Audit and metrics
Nodes SHOULD emit an audit event for rejected or quarantined skew violations. Metrics SHOULD include accepted skew distribution and rejected-skew counts so operators can distinguish clock drift from hostile peers.
Conflict resolution relationship
Conflict resolution may use HLC ordering as a tie-breaker. Facts rejected for bounded-skew violation MUST NOT participate in normal conflict ordering.
Out of scope
This spec does not define NTP configuration, wall-clock synchronization operations, or replay nonce windows.