| CPC H04L 41/0645 (2013.01) [H04L 43/12 (2013.01); H04L 45/16 (2013.01)] | 20 Claims |

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1. A method comprising:
at a network controller that is configured to control routers configured to forward a multicast flow downstream from a first hop router that is a root of a multicast tree formed by the routers to last hop routers that terminate branches of the multicast tree, respectively:
collecting operational configuration information from the routers and constructing a topological view of the multicast tree based on the operational configuration information;
causing the routers to forward multicast probes downstream from the first hop router along all of the branches toward the last hop routers to trace the multicast tree;
receiving, from particular ones of the last hop routers that received the multicast probes, indications that the multicast probes were received; and
detecting failures in the multicast tree based on the indications and the topological view.
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