external communications traffic

Network data flows—packets, sessions, and protocol exchanges—that cross an organizational boundary, moving between an internal network and an external one (typically the public internet or a third-party network). It is distinguished from purely internal traffic by its traversal of a managed interface such as a firewall, gateway, or proxy, where boundary-protection controls are applied: enforcing traffic-flow policies, blocking spoofed-source packets, filtering unauthorized protocols, and preventing cleartext transmission of sensitive data. In NIST SP 800-53 (SC-7), boundary protection is framed around monitoring and controlling communications at the external boundary through managed interfaces—gateways, routers, firewalls, and similar devices—that sit between internal organizational networks and external networks. NIST SP 800-171 (§ 3.13.1) uses the concept operationally, for example by restricting external web communications traffic to designated web servers and prohibiting traffic that appears to spoof internal addresses. CIS Control 12 (Boundary Defense) similarly directs organizations to control the flow of traffic through network borders using firewalls, proxies, DMZ perimeter