This read-create PtopoChassisIdType indicates, per its source description, the encoding scheme (entPhysicalAlias-based, ifAlias-based, port entPhysicalAlias-based, MAC address, or general network address) used to identify the chassis at the remote end of this physical connection, and it cannot be modified once the row's RowStatus is active. Admins reading this field know how to interpret the accompanying ptopoConnRemoteChassis value, since the same octet string field means different things depending on this type. For example, a value of chasIdMacAddress(4) tells a topology-mapping tool to interpret ptopoConnRemoteChassis as a raw MAC address rather than an alias string.