An apparatus comprising a path computation element (PCE) configured to communicate with a path computation client (PCC) and compute a point-to-multipoint (P2MP) path across an autonomous system (AS) domain. Also included is a network component comprising at least one processor configured to implement a method comprising obtaining a computation request for a P2MP path across a plurality of AS domains, attempting to calculate the P2MP path across the AS domains, thereby generating a computed path or a failure reason, and transmitting a reply comprising the computed path or an indication of the failure reason. Included is a method comprising exchanging a request message and a reply message about a P2MP path across an AS domain between a PCC and a PCE.