DSCP-based QoS Configuration

RUCKUSFastIron releases support basic DSCP-based QoS (also called Type of Service [ToS]-based QoS). However, the FastIron family of switches does not support other advanced DSCP-based QoS features.

RUCKUSFastIron releases also support marking of the DSCP value. The software can read Layer 3 Quality of Service (QoS) information in an IP packet and select a forwarding queue for the packet based on the information. The software interprets the value in the six most significant bits of the IP packet header 8-bit ToS field as a DSCP value and maps that value to an internal forwarding priority.

Note: MAC ACLs and DSCP marking cannot be configured on the same port.

The internal forwarding priorities are mapped to one of the eight forwarding queues (qosp0 through qosp7) on the RUCKUS device. During a forwarding cycle, the device gives more preference to the higher-numbered queues, so that more packets are forwarded from these queues. For example, queue qosp7 receives the highest preference, while queue qosp0, the best-effort queue, receives the lowest preference.

Application Notes for DSCP-Based QoS

  • DSCP-based QoS is not automatically honored for routed and switched traffic. The default is IEEE 802.1p to CoS mapping. To honor DSCP-based QoS, you must either use an ACL or enable trust DSCP.
  • When DSCP marking is enabled, the device changes the contents of the inbound packet ToS field to match the DSCP-based QoS value.

Using ACLs to Honor DSCP-Based QoS

This section shows how to configure RUCKUS devices to honor DSCP-based QoS for routed and switched traffic.

DSCP-based QoS is not automatically honored for switched traffic. The default is IEEE 802.1p to CoS mapping. To honor DSCP-based QoS, you must enter the trust dscp command at the interface level of the CLI.

When the trust dscp command is enabled, the interface honors the Layer 3 DSCP value. By default, the interface honors the Layer 2 CoS value.

Note: On RUCKUS 7650 device, configuring the trust dscp command to honor DSCP-based QoS classification on the ingress port works on all traffic except GRE tunnels; classification on these remains based on Layer 2 (IEEE 802.1p) trust. For GRE tunnels, you can use ACLs to configure classification based on the DSCP value.

Remarking Configuration Considerations and Limitations

Keep the following considerations in mind when configuring remarking.

For a router image:

  • When DSCP remarking is enabled on a virtual interface (VE), an ingress ACL applied to the VLAN to which the VE belongs honors the DSCP remarking value configured on the VE.
  • When PCP remarking is enabled on a VE, an egress ACL applied on the VLAN to which the VE belongs honors the PCP remarking value configured on the VE.
  • DSCP/PCP remarking is not supported on tagged interfaces in the router image.
  • When DSCP remarking is enabled on a Layer 3 physical or LAG interface, an ingress ACL applied to the physical or LAG interface honors the DSCP remarking value configured for the physical or LAG interface.

For a switch image:

  • When DSCP remarking is enabled on a physical or LAG interface, an ingress ACL applied to the physical or LAG interface honors the DSCP remarking value configured for the physical or LAG interface.
  • DSCP/PCP remarking is not supported in an ACL applied to a selective port of a VLAN.
  • DSCP/PCP remarking cannot be enabled on an interface, LAG, or VE when an existing ACL with DSCP/802.1p marking options in a filter statement has already been applied to the interface, LAG, or VE. Likewise, DSCP/802.1p marking options in ACL filter statements are not supported on an interface, LAG, or virtual interface when DSCP/PCP remarking has already been enabled on the interface, LAG, or virtual interface.

Parent topic: Quality of Service