# QoS
> Quality of Service – network mechanisms that prioritize VoIP traffic for reliable call quality

QoS (Quality of Service) prioritizes VoIP packets on a network to ensure clear, uninterrupted calls.

## What is QoS?
Quality of Service (QoS) refers to the set of technologies and policies that manage network traffic to ensure certain types of data — particularly real-time voice and video — receive priority treatment. Without QoS, VoIP packets compete with all other traffic, leading to [jitter](/voip-glossary/jitter/), [latency](/voip-glossary/latency/), and packet loss.

## QoS mechanisms
Common QoS techniques include DSCP (Differentiated Services Code Point) marking, traffic shaping, priority queuing, and bandwidth reservation. In enterprise networks, QoS policies are typically configured on routers and switches to prioritize [RTP](/voip-glossary/rtp/) media streams.

## QoS for mobile softphones
On mobile networks, QoS is harder to control since the carrier manages the radio link. [Softphone](/voip-glossary/softphone/) apps compensate with adaptive codecs, jitter buffers, and packet loss concealment algorithms.

## Related Terms
- [Jitter](/voip-glossary/jitter/)
- [Latency](/voip-glossary/latency/)
- [MOS](/voip-glossary/mos/)