Failure Modes + Device Attributes + Network Edge

Fail-open

When a device or system experiences a failure, it defaults to an “open” state—allowing all traffic or operations to continue. This prioritizes availability over security, ensuring services remain accessible even if the control mechanism is down

Fail-closed

In contrast, a fail-closed configuration shuts down or blocks all traffic when a failure occurs. This approach favors security by denying access until the system is restored, preventing potentially malicious or uncontrolled activity during outages

Active devices

are inline, powered components that can inspect, filter, or modify traffic (e.g., firewalls, IDS/IPS)—they interact directly with network flows

Passive devices

simply observe or replicate traffic without being in the data path; they don’t block or alter packets (e.g., network taps, SPAN ports)

Inline devices

sit directly in the traffic path and enforce security policies in real time (e.g., next-gen firewalls).

Tap/Monitor devices

are deployed out-of-band to copy traffic to analysis tools; they never interrupt or alter the live data stream, preserving performance and avoiding single points of failure

Network Edge

the connection or interface between a device or local network and the internet. The __ is close to the devices it is communicating with and is the entry point to the network