This read-write octet string is the group-address counterpart to lportSmdsIaScrnMap, using the identical add or delete plus bitmap encoding but applied to group or multicast SMDS addresses instead of individual ones. An admin manages multicast group membership for this port's SMDS screening policy through this object, adding or removing specific group IDs as customer multicast requirements change. For example, adding a customer to a new SMDS multicast distribution group means writing a SET with the add operation code and the bit corresponding to that group's screen member ID turned on in lportSmdsGaScrnMap.