Attaining stable and loop-free inter-domain routing without path vectors

ABSTRACTA sufficient condition for loop-free routing is introduced based on path labels. A path label consists of the identifier of the first node and hop-count length of a path to a destination. This condition is applied to the policy mechanisms used in BGP, which results in BGP-ELF (BGP Enhanced for Loop Freedom). BGP-ELF uses updates, queries, and replies based on path labels to attain multi-path loop-free and stable routing across autonomous systems without the need for path vectors.