MD
A multicast domain (MD) is composed of VPN instances on PEs that can receive and send multicast data between each other. A PE VPN instance can belong only to one MD. Different VPN instances belong to different MDs. An MD serves a specific VPN. All private multicast data transmitted in the VPN is transmitted in the MD.
Share-group
A share-group is a group that all PE VPN instances in the same MD should join. A VPN instance can join a maximum of one share-group.
Share-MDT
A share-multicast distribution tree (share-MDT) transmits PIM protocol packets and data packets between PEs in the same VPN instance. A share-MDT is built when PIM C-instances join share-groups.
MTI
A multicast tunnel interface (MTI) is the outbound or inbound interface of a multicast tunnel (MT) or an MD. MTIs are used to transmit VPN data between local and remote PEs.
An MTI is regarded as a channel through which the public network instance and a VPN instance communicate. An MTI connects a PE to an MT on a shared network segment and sets up PIM neighbor relationships between PE VPN instances in the same MD.
Switch-group
A switch-group is a group to which all VPN data receivers' PEs join. Switch-groups are the basis of switch-MDT setup.
Switch-MDT
A switch-multicast distribution tree (switch-MDT) implements on-demand multicast data transmission, so a switch-MDT transmits multicast data to only PEs that require the multicast data. A switch-MDT can be built after a share-MDT is set up and VPN data receivers' PEs join a switch-group.