DSCP is a 6-bit field in the IP header indicating packet priority. Voice typically uses EF (46), video AF41, best-effort 0.

What Is QoS?

Q: Is QoS needed in a regular office

Highly recommended if you run VoIP or video conferencing on shared bandwidth.

Q: Does QoS work over the public internet

Limited, ISPs do not guarantee customer DSCP marks. MPLS, SD-WAN with carrier QoS, or a dedicated pure VoIP network is more reliable.

2026-05-07 2 min readSIPPER Team

QoS prioritizes traffic on a network so latency-sensitive apps (voice, video) get bandwidth before tolerant apps (email, file transfer).

Definition

QoS marks packets at Layer 2 (CoS / 802.1p) and Layer 3 (DSCP). Switches and routers read these marks and queue traffic by priority. Voice typically uses DSCP EF (46) for top priority.

Usage

Essential on networks carrying voice / video, they are sensitive to latency (over 150 ms is bad), jitter (over 30 ms causes choppiness), and packet loss (over 1 percent breaks audio).

Related Concepts

CoS, DSCP, traffic shaping, bandwidth reservation, RSVP, LLQ (Low Latency Queue).

Frequently Asked Questions

Is QoS needed in a regular office

What is DSCP marking

Does QoS work over the public internet

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