This draft describes a simple mechanism that ease discovery of remote Autonomous Systems (AS) supporting inter-domain MPLS-based constrained tunnels service (this service is also denoted by Path Computation Service (PCSv)) thanks to the use of Path Computation Elements (PCEs). Remote ASs could be managed by a single or distinct Internet Network Providers (INP). Particularly, this draft describes how Border Gateway Protocol (BGP) is used to announce Path Computation Service unique identifiers across the Internet in order for other PCEs to be able to discover a path towards every AS supporting this Path Computation Service.