Differentiated Services Code Point (DSCP) remarking can be configured using three main types of configuration with different levels of QoS precedence.

There is a debate between using the terms “marking” or “remarking.” Almost all devices initially mark the DSCP packets with a value. Every packet has one of 64 values, a decimal number from 0 to 63, in the DSCP field. Each of these values, including 0, is a legitimate DSCP. When the packet is processed by a DSCP marker, we can use the term "remarking" the packet, even though the DSCP may not change.

DSCP remarking is performed on ICX devices using different types of configuration:

  • ACL—Traffic matching a specific pattern is remarked.
  • Interface (Physical, LAG, VE)—Traffic entering a physical, LAG, or VE interface (except traffic matched by an ACL) is remarked with a configured value.

ACL Remarking

ACLs can be configured to match a specific pattern and remark DSCP values. When remarking is not enabled using ACLs, a rogue host that wants preferential treatment for all its traffic could mark the DSCP field for its requirements and send the traffic to the device.

For more information on QoS marking using ACLs, refer to "QoS options for IP ACLs" in the RUCKUS FastIron Security Configuration Guide.

Interface (Physical, LAG, VE) Interface Remarking

Packets entering a physical, LAG, or VE interface can be remarked with a configured DSCP value. Remarking at the interface or VLAN level can be referred to as Class of Service (CoS) remarking although the values set are DSCP values. Remember that DSCP remarking configuration at the ACL level takes precedence over the DSCP remarking configuration at the interface level.

When DSCP marking is configured on a given port, the DSCP field of any IPv4 packet received on the port is re-marked to the configured value.

For a configuration example of QoS remarking at the interface level, refer to Configuring DSCP and CoS Remarking at the Interface Level.

For information about the QoS remarking using physical, LAG, or VE interfaces in VXLANs, refer to the "Quality of Service Support" topic in the RUCKUS FastIron Layer 2 Switching Configuration Guide.