A system implemented with a collection of interconnected components. Such components may include routers, hubs, cabling, telecommunications controllers, key distribution centers, and technical control devices.
Sources:
NIST SP 800-171r3
NIST SP 800-172r3
NIST SP 800-37 Rev. 2

  A system implemented with a collection of connected components. Such components may include routers, hubs, cabling, telecommunications controllers, key distribution centers, and technical control devices.
Sources:
NIST SP 800-53 Rev. 5

  An open communications medium, typically the internet, used to transport messages between the claimant and other parties. Unless otherwise stated, networks are assumed to be open and subject to active (e.g., impersonation, session hijacking) and passive (e.g., eavesdropping) attacks at any point between the parties (e.g., claimant, verifier, CSP, RP).
Sources:
NIST SP 800-63-4 [