FINDING · EVALUATION
Some obfs4 bridges exhibited a roughly 24-hour periodic semi-blocking pattern from China, where bridges cycled between reachable and blocked states with a ~24-hour period. This diurnal pattern differed between the two China probe sites and between bridges, and one blocking failure coincided with a documented nationwide GFW outage that also briefly restored access to Google services.
From 2016-fifield-censors — Censors' Delay in Blocking Circumvention Proxies · §4 Results, Figure 3 · 2016 · Free and Open Communications on the Internet
Implications
- Circumvention clients should implement automatic retry with backoff rather than treating a failed connection as permanently blocked; diurnal patterns mean a bridge that fails at one time of day may succeed hours later.
- Monitoring bridge reachability at multiple times of day from multiple vantage points is necessary to distinguish permanent blocking from periodic enforcement gaps.
Tags
Extracted by claude-sonnet-4-6 — review before relying.