Maint Log 20251206

Routing Policy

Path Prepending

We have refactored the BGP filter logic governing AS Path prepending to ensure deterministic behavior. Previously, multiple community tags could result in cumulative prepending operations, leading to unintentionally excessive AS path lengths. The new implementation enforces a "maximum-value wins" strategy: the filter now evaluates all present community tags, identifies the one requesting the highest prepend count, and applies the operation exactly once.

Traffic Engineering

To provide more granular control over traffic ingress, we have expanded the BGP community definitions to include region-specific prepend triggers. Operators can now apply 1x, 2x, or 3x AS Path prepends targeted at specific geographic regions. This allows for regional traffic engineering, permitting the deprioritization of routes in specific regions without negatively impacting global route preferability or convergence.

Peers Adjustment

The policy regarding underperforming transit peers -- particularly those located in the China region -- has been revised to prioritize connectivity over strict quality filtering. Previously, peers exhibiting sub-optimal transit performance were tagged with NO_EXPORT, effectively removing them from the routing table. We have shifted this to a "soft-deprioritization" model: instead of suppressing these routes entirely, the network now applies aggressive AS Path prepending. This strategy discourages traffic flow via these links under normal conditions while preserving them as valid backup paths.