Implement a managed interface for each external telecommunication service; Establish a traffic flow policy for each managed interface; Protect the confidentiality and integrity of the information being transmitted across each interface; Document each exception to the traffic flow policy with a supporting mission or business need and duration of that need; Review exceptions to the traffic flow policy {{ insert: param, sc-07.04_odp }} and remove exceptions that are no longer supported by an explicit mission or business need; Prevent unauthorized exchange of control plane traffic with external networks; Publish information to enable remote networks to detect unauthorized control plane traffic from internal networks; and Filter unauthorized control plane traffic from external networks.
(a) Implement a managed interface for each external telecommunication service;
(b) Establish a traffic flow policy for each managed interface;
(c) Protect the confidentiality and integrity of the information being transmitted across each interface;
(d) Document each exception to the traffic flow policy with a supporting mission or business need and duration of that need;
(e) Review exceptions to the traffic flow policy {{ insert: param, sc-07.04_odp }} and remove exceptions that are no longer supported by an explicit mission or business need;
(f) Prevent unauthorized exchange of control plane traffic with external networks;
(g) Publish information to enable remote networks to detect unauthorized control plane traffic from internal networks; and
(h) Filter unauthorized control plane traffic from external networks.
External telecommunications services can provide data and/or voice communications services. Examples of control plane traffic include Border Gateway Protocol (BGP) routing, Domain Name System (DNS), and management protocols. See [SP 800-189](#f5edfe51-d1f2-422e-9b27-5d0e90b49c72) for additional information on the use of the resource public key infrastructure (RPKI) to protect BGP routes and detect unauthorized BGP announcements.