3. Discard Eligibility Indicator (DEI) based Classification and Marking

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

Note:

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

3.1. DEI-based Classification

DEI bit in the received packet is used to determine the ingress profile for the packet. If in the received packet, DEI = 0, then the packet is considered to be GREEN or in-profile and if DEI = 1, then the packet is considered to be YELLOW or out-of-profile. The profile assigned at the 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 green/in-profile and if it exceeds the CIR rate and is below the PIR rate, it is assigned yellow/out-of-profile.

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, allowing user an option to enable/disable use of DEI for ingress classification on a per port basis. Initial profile (also known as color) is based on DEI/CFI bit. If in the received packet, DEI = 0, then packet can be considered to be GREEN or in-profile and if DEI = 1, then packet can be considered to be YELLOW or out-of-profile by the subsequent processing flow in 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 user so desires. The user has an option to use color-blind metering for some SAPs and color-aware metering for some other SAPs configured on the same port when DEI classification is enabled on the 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 user configures meter/policer mode as color-aware, then incoming packet DEI bit 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 policy, DEI-based classification is supported only when dot1p classification criteria is in use. In other words, 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. DEI bit can be used to mark the packet to carry the profile, assigned by an operator’s trusted node at the ingress to the carrier’s 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 DEI bit of 0 and out-of-profile packets are marked with DEI bit of 1. The user has an option to mark all the packets belonging to a FC to the same DEI value irrespective of its profile using the “force-de-mark” option.
    Note:

    See the Network QoS Policy Command Reference, Access Egress QoS Policy Command Reference, and the 7210 SAS-D, Dxp, K 2F1C2T, K 2F6C4T, K 3SFP+ 8C Basic System Configuration Guide for more 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 have been enabled on the port on which 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 from one mode (access/access-uplink/network/hybrid) to another mode.
  4. All the ports under a LAG should have the same configuration for DEI classification (enable/disable). If the LAG configuration changes, the port configuration also will be updated accordingly. Port configuration under the LAG cannot be changed.