Provider MSTP is specified in IEEE-802.1ad-2005. It uses a provider bridge group address instead of a regular bridge group address used by STP, RSTP, and MSTP BPDUs. This allows for implicit separation of source and provider control planes.
The 802.1ad access network sends PBB PE P-MSTP BPDUs using the specified MAC address and also works over QinQ interfaces. P-MSTP mode is used in PBBN for core resiliency and loop avoidance.
Similar to regular MSTP, the STP mode (for example, PMSTP) is only supported in VPLS services where the m-VPLS flag is configured.