zxr10PortGroupCommunicateUnit identifies the communication unit associated with an MCAPS (multi-chassis APS) port group, per its description. An admin uses this to correlate a port group with the specific chassis or unit handling its inter-chassis protection signaling in a multi-chassis APS setup, where the configurable maximum is defined dynamically rather than fixed. For example, a value of 2 here would indicate this MCAPS port group's protection communication is tied to communication unit 2 in the ZXR10 system.