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UniFi - QoS and Prioritization

Overview

This article describes how the UniFi Access Point (UAP) handles Quality of Service (QoS). QoS prioritizes traffic so that traffic passes in order of importance, improving performance for critical network traffic. UniFi supports QoS based on WMM (aka WME).

Table of Contents

  1. UniFi Access Points Mapping
  2. DSCP Values

UniFi Access Points Mapping

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The UniFi AP maps DSCP value to WMM priorities and processes these packets accordingly. The UAP considers either DSCP or COS. It compares COS with DSCP (the first 3 bits) and takes whichever has a higher value to map to WMM AC according to the table below:

DSCP P2 DSCP P1 DSCP P0 DSCP-- DSCP-- DSCP-- DSCP hex 802.1d WMM AC
1 1 1 0 0 0 0x38 7 AC_VO
1 1 0 0 0 0 0x30 6 AC_VO
1 0 1 0 0 0 0x28 5 AC_VI
1 0 0 0 0 0 0x20 4 AC_VI
0 1 1 0 0 0 0x18 3 AC_BE
0 1 0 0 0 0 0x10 2 AC_BK
0 0 1 0 0 0 0x08 1 AC_BK
0 0 0 0 0 0 0x00 0 AC_BE 

DSCP to 802.1d mapping per WMM specifications, as supported by UniFi APs.

DSCP Values

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DSCP values (Decimal): WMM AC

  • 0 to 7: Best Effort
  • 8 to 23: Background
  • 24 to 31: Background
  • 32 to 47: Video (except 46)
  • 46, 48 and above: Voice

On the AP receiving end, 802.11 is on top of the ethernet frame. The access point then sends packets onto the wire the way it receives over-the-air (without 802.11 header). For example, a VoIP phone sends VO packets in DSCP 46 and that will be the DSCP value of the ether frames that AP sends out on wire.

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