BGP-LS Extension for Inter-AS Topology Retrieval

This document specifies the procedure for distributing Border Gateway Protocol-Link State (BGP-LS) key parameters for inter-domain links between two Autonomous Systems (ASes). It defines a new type within the BGP-LS Network Layer Reachability Information (NLRI) for an inter-AS Link, as well as three new type-length-values (TLVs) for the BGP-LS inter-AS Link descriptor. These BGP-LS extensions enable Software-Defined Networking (SDN) controllers to retrieve network topology across inter-AS environments. These extensions and procedures allow network operators to collect inter-domain interconnect information and automatically compute the end-to-end network topology using information provided by the BGP-LS protocol.