When enabling MSTP, you define one or more MSTP regions. An MSTP region defines a logical
domain where multiple spanning-tree instances (MSTIs) can be administered independently of MSTIs
in other regions, setting the boundary for bridge protocol data units (BPDUs) sent by one MSTI. An
MSTP region is a group of switches that is defined by three parameters:
Region name—User-defined alphanumeric name for the region.
Revision level—User-defined value that identifies the region.
Mapping table—Numerical digest of VLAN-to-instance mappings.
https://www.juniper.net/documentation/us/en/software/junos/stp-l2/topics/topic-map/spanningtree-configuring-mstp.html
