3. DEI-based classification and marking

This chapter provides information about the Discard Eligibility Indicator (DEI) feature that describes the requirements for DEI-based classification and marking for 7210 SAS platforms.

Note:

DEI classification and marking is only supported on the 7210 SAS-D and 7210 SAS-Dxp.

3.1. DEI-based classification

The DEI bit in the received packet is used to determine the ingress profile for the packet. If DEI equals zero in the received packet, the packet is considered in-profile or green, and if DEI equals one, the packet is considered out-of-profile or yellow.

The profile assigned on ingress can be used to enable color-aware metering with SAP ingress policing and access-uplink port ingress policing. The profile of the packet can be reassigned by ingress meters/policers. When policing is used on SAP ingress, the final profile of the packet is determined by the meter/policers, based on the configured CIR/PIR rates. If a packet is below CIR rate, it is assigned in-profile/green and if it exceeds the CIR rate and is below the PIR rate, it is assigned out-of-profile/yellow.

The final profile assigned at ingress is used by egress to determine the WRED slope to use. The WRED slope determines whether the packet is eligible to be assigned a buffer and can be queued up on egress queue for transmission.

The following support is available for DEI classification:

  1. Under the port configuration, a command is provided to enable DEI-based classification, which enables the use of DEI for ingress classification on a per-port basis. The initial profile (or color) is based on the DEI/CFI bit. If DEI equals zero in the received packet, the packet is considered in-profile or green, and if DEI equals one, the packet is considered out-of-profile or yellow by the subsequent processing flow in the hardware. The FC classification can be done using MAC or IP criteria.
  2. All the SAPs configured on the port (access or hybrid) can use DEI classification for color-aware metering, if required. When DEI classification is enabled on the port, the user has an option to use color-blind metering for some SAPs and color-aware metering for other SAPs configured on the same port. When using color-blind mode, the ingress profile assigned to the packet based on the DEI bit is ignored.
  3. The user is provided with an option in the SAP-ingress policy to configure a policer as color aware or color blind. In color-aware mode, the DEI bit in the packet determines the ingress profile of the packet. If the user configures the meter/policer mode as color-aware, the DEI bit of the incoming packet is used by the policer as the ingress profile.
  4. When using policing, the final profile of the packet is assigned by the ingress meter (based on configured CIR/PIR rate) in both color-aware and color-blind mode.
  5. For network port policies, DEI-based classification is supported only when dot1p classification criteria are in use; it cannot be used when DSCP-based classification is used.

3.2. DEI-based marking

DEI-based marking is supported on access ports, access-uplink ports, and network ports. The DEI bit can be used to mark the packet to carry the profile (which is assigned by an operator’s trusted node on ingress to the carrier network) to the subsequent nodes in the network. It allows high-priority in-profile packet to be allocated appropriate resources by all the network nodes on the path to the final destination. Similarly, it allows out-of-profile packets to be treated with less preference compared to in-profile packets by all the network nodes on the path to the final destination. The egress marking behavior must be symmetric to the ingress classification behavior.

The following support is available for DEI-based marking:

  1. option to mark DEI bits for port egress on access ports and access-uplink ports
  2. by default, in-profile packets are marked with a DEI bit of 0 and out-of-profile packets are marked with a DEI bit of 1. The user has an option to mark all the packets belonging to an FC with the same DEI value, regardless of its profile, by using the force-de-mark command.
    Note:

    See Network QoS policy command reference and Access egress QoS policy command reference, and refer to the 7210 SAS-D, Dxp, K 2F1C2T, K 2F6C4T, K 3SFP+ 8C Basic System Configuration Guide for information about the CLI commands for DEI.

3.3. Configuration guidelines

The following are configuration guidelines for DEI-based classification and marking:

  1. While disabling DEI-based classification on a port, all the meters used by the SAPs configured on this port must be in color-blind mode. The converse is also true, that is, while attaching a SAP-ingress QoS policy with meter as color aware to a SAP, the DEI-based classification must be enabled on the port where the SAP exists.
  2. While configuring DEI-based classification in a access-uplink network QoS Policy (ingress), only dot1p classification can be used.
  3. DEI classification must be disabled on that port prior to changing the mode (access, access-uplink, network, hybrid) to another mode.
  4. All the ports under a LAG should have the same configuration for DEI classification (either enabled or disabled for all member ports of a LAG). If the LAG configuration changes, the port configuration is also updated accordingly. Port configuration under the LAG cannot be changed.