Quality of Service (QoS)

Q-SYS is a live audio, video, and control system, so real-time performance is critical within the network environment. QoS is required in the Q-LAN network to prevent non-real-time control and bulk communications from affecting performance of time-sensitive clocking, audio, and video traffic.

Q-SYS uses the DSCP field in the IP header to specify traffic priority to the network. The network must inspect, distinguish, and prioritize the following traffic classes. System administrators may choose to trust the DSCP values transmitted by Q-SYS or alternatively reassign new DSCP values based on these values or other distinguishing traffic characteristics. As long as traffic is properly prioritized, it is not necessary to preserve these exact DSCP values through the network.

To assign DSCP values in your Q-SYS design, go to File > Design Properties in Q-SYS Designer. You can select from QLAN, Audinate, and Manual presets.

Select the QLAN preset for Q-LAN traffic optimization.

Priority DSCP Value Binary Equivalent Meaning Traffic Type

Highest

46

101 110

High Priority, Expedited Forwarding (EF)

PTPv2 clock distribution

Second Highest

34

100 010

AF41

Q-SYS audio streams

Third Highest

26

011 010

AF31

Q-SYS video streams

Lowest

0

000 000

Best Effort

Q-SYS control and management traffic (everything else)

Select the Audinate preset for Audinate (Dante) traffic optimization. Refer to the Other Networked Audio topic for Dante networking requirements.

Priority DSCP Value Binary Equivalent Meaning Traffic Type

Highest

56

111 000

CS7

PTPv2 clock distribution

Second Highest

46

101 110

High Priority, Expedited Forwarding (EF)

Q-SYS audio streams

Third Highest

26

011 010

AF31

Q-SYS video streams

Lowest

0

000 000

Best Effort

Control and management traffic (everything else)

You can change the DSCP settings for PTPv2, Q-SYS audio, and Q-SYS video to allow custom QoS mapping. You must, however, maintain the priority hierarchy of:

  • PTPv2 highest
  • Q-SYS Audio second highest
  • Q-SYS Video third highest

Note: PTP, Audio, and Video queue priorities must also be maintained across any uplinks and cannot be shared with any identically-queued packets from other VLANs being sent via the same uplinks in a VLAN trunk.

Q-LAN audio packets must pass from source to destination within 280 μs or less or they are considered too late. You can see detailed network performance statistics by enabling Verbose mode in Q-SYS Core and peripheral Status components in Q-SYS Designer:

  1. Drag a Q-SYS Core or peripheral Status component into the schematic.
  2. In the component Properties pane, set the Verbose property to 'Yes'.
  3. Save and run the design to the Core.
  4. Double-click the Status component to see statistics information:
    • "drop_count" shows the number of packets that were delivered too late (outside of the 280μs time allowed on the network) and have therefore been disregarded by the destination Q-SYS device. This also applies to packets received out of sequential order.
    • "missing_count" is a count of expected packets which were not received by the destination Q-SYS Device.