https://www.juniper.net/documentation/us/en/software/junos/multicast/topics/topic-map/mcast-pim-designated-router.html
Configuring a Designated Router for PIM | Junos OS | Juniper Networks
A designated router (DR) sends periodic join messages and prune messages toward a group-specific rendezvous point (RP) for each group for which it has active...
designated routerjunos osconfiguringpimjuniper