What is QoS in voice networks?

• A. Mechanisms that prioritize time-sensitive voice/video traffic.
• B. A method to compress voice codecs.
• C. A policy to encrypt calls end-to-end.
• D. A system to authenticate devices.

Answer: (A)

Quality of Service in voice networks is about ensuring that voice packets get preferred handling so calls stay clear and responsive. Voice is time-sensitive, so when network congestion happens, QoS mechanisms prioritize these packets to keep latency low, jitter minimal, and loss rare. This is done by classifying traffic, marking it (for example with DSCP values), and then queuing and scheduling it to get precedence or reserved bandwidth. You might use strict or weighted priority queuing, combined with shaping or policing, to protect voice flows even when data traffic is heavy. The other options describe techniques for reducing bandwidth (compression), securing traffic (encryption), or verifying devices (authentication), which are not what QoS manages.