This read-write TruthValue indicates whether NCDP is presently running on an ATM Network-to-Network Interface, with the description noting the agent initializes it to true after instantiation and that, by default, all Network-to-Network interfaces participate. An admin can disable NCDP participation on a specific interface if it shouldn't be part of the clock distribution topology, overriding the default of participation. Setting this to false on an interface facing an untrusted or non-NCDP-capable neighbor would exclude that link from the clock tree computation.