A read-only TruthValue indicating, for a head-end unit, that the link is in loopback mode when true, or for a subscriber unit, that its service is disabled when true. Because the meaning of true differs between head-end and subscriber roles, an admin has to know which type of unit they are reading this from before correctly interpreting whether it signals a test mode or an outright service disablement. For example, an admin troubleshooting a subscriber unit that shows no traffic would check p2mpDenyService first, since a true reading there means the unit's service has been deliberately disabled rather than suffering an actual link fault.