Multiprotocol label switching (MPLS) is currently used inside autonomous systems (ASs) for virtual private networks (VPNs) or traffic engineering (TE) purposes. We first discuss the service provider's requirements for the utilization of MPLS label switched paths (LSPs) across AS boundaries. Then we propose a minimum set of extensions to RSVP-TE that allow inter-AS LSPs to be established in accordance with the SP's requirements. We also show how LSP protection techniques can be extended to provide link or node failure protection for the inter-AS links and border routers.
Pelsser, C., & Bonaventure, O. (2003). Extending RSVP-TE to support inter-AS LSPs. Workshop on High Performance Switching and Routing, 2003, HPSR., p. 79-84. https://doi.org/10.1109/HPSR.2003.1226684