BFD stands for which term?

• A. Inter-frame Delay Variation
• B. Frame Delay
• C. Bidirectional Forwarding Detection
• D. Frame Loss Ratio

Answer: (C)

Fast detection of a failure along the path between two devices is essential for quick rerouting in a WAN. Bidirectional Forwarding Detection is a lightweight protocol that checks the forwarding path by exchanging small control packets at a configurable interval to verify that both directions of the path are alive. If a device stops receiving these packets within the agreed detection time, the path is considered down, triggering rapid failover or reroute. This rapid detection is especially valuable in MEF SD-WAN, where multiple transport options and dynamic path selection rely on fast switching to maintain service continuity. The other terms are metrics about frames themselves—delay, jitter, or frame loss—not a protocol for detecting forwarding failures. So the term described is Bidirectional Forwarding Detection.