Entry containing COPS status for a particular interface.
By default each interface has no roles. It then has a role
combination that is the zero length string.
Roles in a role combination for an interface are reported
to the PDP by the PEP. An interface may have multiple roles.
Adding/deleting roles results in changes to the role
combination for an interface. Therefore, a new set of QoS
policies will be used for the interface with the new role
combination.