Which metric measures the percentage of time that the service is usable?

• A. Frame Delay(FD)
• B. Frame Loss Ratio(FLR)
• C. Availability
• D. Inter-frame Delay Variation(IFDV)

Answer: (C)

Availability is the metric that captures whether the service is usable over time. It expresses the percentage of total monitoring time during which the service is up and reachable, reflecting uptime and any periods of downtime. It’s typically calculated as (uptime / total time) × 100, so even brief outages reduce the percentage. Frame Delay measures latency, Frame Loss Ratio tracks how many frames are lost, and Inter-frame Delay Variation looks at jitter; these reflect quality and performance rather than overall uptime. So availability best quantifies the fraction of time the service remains usable.