BGP Role Model: Tracking the Adoption of RFC 9234

Route leaks cause issues by directing traffic through unintended network paths. This occurs when the 'valley-free' hierarchy based on relationships between ASes (Autonomous Systems) (customer-provider, peer-peer) is violated, with cases like a 'hairpin turn'—where a customer advertises a path between two providers—being typical examples.

Previously, operators had to directly manage complex and error-prone routing policies, but RFC 9234 simplifies this process by expressing intent directly within the protocol.

The core mechanisms of RFC 9234 are as follows:

• BGP Role: Defines the relationships between adjacent nodes (Provider, Customer, Peer, RS, RS-Client) in advance during eBGP sessions.
• OTC (Only to Customer) Attribute: Marks paths so they do not propagate beyond customers, allowing routers that understand this attribute to reject leaked paths without requiring separate operator policies.

Cloudflare tracked the adoption status of RFC 9234 through its global peering infrastructure. The investigation revealed that some large Tier-1 networks are stripping the OTC attribute from the paths they propagate.

When the OTC attribute is stripped, early adopters find it difficult to fully utilize route leak prevention features. Cloudflare is currently working with these Tier-1 networks to ensure they properly propagate the OTC attribute.