INTER-AS OPTION B: BALANCED ARCHITECTURE FOR SCALABLE MPLS VPN INTERCONNECTION ACROSS AUTONOMOUS SYSTEM BOUNDARIES

Abstract

This article explores Multi-Protocol Label Switching (MPLS) Virtual Private Network (VPN) interconnection across different Autonomous Systems (ASes), with a focus on Inter-AS Option B implementation. Starting with foundational concepts of MPLS VPNs, including Virtual Routing and Forwarding (VRF) instances, Route Distinguishers, and Route Targets, the article details how Option B creates direct VPN-IPv4 route exchange between Autonomous System Boundary Routers (ASBRs) while preserving MPLS labels. The architecture, operational mechanisms, and protocol interactions are examined, including MP-BGP extensions and label distribution methods. Comparative analysis against Options A and C reveals Option B's balanced position between isolation strength and scalability. Technical implementation aspects cover configuration requirements, traffic engineering considerations, and security implications. Performance metrics demonstrate Option B's effectiveness in real-world deployments, offering service providers a pragmatic solution for MPLS VPN interconnection that combines operational efficiency with appropriate security controls while avoiding the extreme trade-offs presented by alternative options.