A host needs to join a specific source S for group G in an SSM deployment. Which IGMP message type will the host send to indicate this source-specific join?

For Source-Specific Multicast (SSM), hosts use IGMPv3 to explicitly request traffic from a specific source (S) for a specific group (G). The IGMPv3 Membership Report is the message type used for this purpose, containing an INCLUDE list with the desired source. IGMPv1 and IGMPv2 do not support source-specific joins; they only allow joining a group without specifying a source. IGMPv2 Leave is used to indicate a host is no longer interested in a group. IGMPv3 Leave Group messages are also used to indicate a departure from a group, but they do not initiate a source-specific join.