The protocol type of the Multicast Routing Protocol Manager (MRPM) to join to. Together with mgmdRouterEntMrpmEntIndex, this uniquely identifies the MRPM entity. To configure this entity to perform IGMP proxy, instruct it to join to an MRPM performing IGMP proxy, by setting this field to 'igmpproxy'. To configure this entity to perform IGMP snooping, instruct it to join to an MRPM performing IGMP snooping, by setting this field to 'igmpsnooping'. A value of 'none' is not valid. This object cannot be changed while the row is active. The field is not expected to be exposed to end users and is not expected to change during the lifetime of the DC-IGMP entity. As such, this object follows the replaceOnlyWhileDisabled behavior.