A method of multicasting real-time video is described. The method begins by establishing a multicast network of machines capable of ingress, forwarding and broadcasting traffic, together with a mapping infrastructure. The multicast network preferably comprises a portion of an overlay network, such as a content delivery network (CDN). A video stream is published to the multicast network by (a) using the mapping infrastructure to find an ingress node in the multicast network, and then receiving the video stream from a publisher at the ingress node. One or more subscribers then subscribe to the video stream. In particular, and for subscriber, this subscription is carried out by (a) using the mapping infrastructure to find an egress node for the requesting client, and then delivering the video stream to the subscriber from the egress node. Preferably, the publisher and each subscriber use WebRTC to publish or consume the video stream, and video stream is consumed in a videoconference.