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.

3.1. DEI-Based Classification

DEI-based classification is supported on access ports, network ports, and hybrid ports on 7210 SAS platforms. 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 network 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 meters/policers. based on the configured CIR and PIR rates. If a packet is below the CIR rate, it is assigned in-profile/green, and if it exceeds the CIR rate and is below the PIR rate, the packet is assigned out-of-profile/yellow.

On the 7210 SAS, the behavior is the same when using ingress policing but is different when using ingress queuing. When using SAP-ingress queuing, the profile assigned to the packet by user configuration cannot be reassigned by the ingress meters/policers or by ingress queue rate shapers. Therefore, the user-assigned profile is the final profile assigned to the packet.

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 enqueued on an egress queue for transmission.

Note:

Ingress policing is supported on all 7210 SAS platforms as described in this document.

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 hardware.
  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. On hybrid ports, only one of the following configurations is allowed. This is enforced by the software:
    1. If DEI-based classification is enabled, the network port ingress policy must use dot1p classification criteria with the DEI profile for all configured dot1p values.
    1. If DEI-based classification is disabled, the network port ingress policy can use dot1p or DSCP classification criteria.
  1. 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.
  2. For network IP interface policies, DEI-based classification is not supported. When using EXP-based classification, the DEI bit cannot be used to assign the profile for the packet.

3.2. DEI-Based Marking

DEI-based marking is supported on access ports, network ports, and hybrid 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 packets to be allocated resources by all the network nodes on the path to the final destination. Similarly, it allows out-of-profile packets to be handled with less preference compared to in-profile packets by all the network nodes on the path to the destination. Typically, the egress marking behavior should be symmetric to the ingress classification behavior.

The following support is available for DEI-based marking:

  1. option to mark DEI bits for access SAP-egress on access ports, network ports, and hybrid ports on 7210 SAS devices configured in network mode
  2. option to mark DEI bits for IP and MPLS packets on network ports (DEI marking is supported for MPLS packets only on those platforms that support dot1p marking for MPLS packets. DEI marking is not supported otherwise.)
  3. 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 an FC with the same DEI value, regardless of its profile, 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-M, T, R6, R12, Mxp, Sx, S 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; while attaching a SAP-ingress QoS policy with the meter set 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 network port ingress policy, only dot1p classification can be used.
  3. DEI classification must be disabled on a port before changing the mode (access, network, or 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. The port configuration under the LAG, cannot be changed.
  5. While enabling DEI-based policing on a port, if it is a hybrid port, the network port ingress QoS policy must use only dot1p mappings for classification, and all the configured profiles must be use-dei (not in or out). This is true even if only SAPs are configured on the port.
  6. While configuring the profile on a network port policy for dot1p classification, if the policy is attached to a hybrid port on which DEI classification is enabled, the profile cannot be changed to in or out. Only DEI bits can be used for profile configuration.
  7. While attaching a network QoS policy to a hybrid port, all the dot1p mappings, including the default mapping, should use only the DEI as the profile, if DEI classification is enabled on this port.
  8. Only after attaching a network port ingress QoS policy, as mentioned above, can the user enable DEI classification on a port. Refer to the 7210 SAS-M, T, R6, R12, Mxp, Sx, S Interface Configuration Guide for more information about DEI classification on a LAG or port.
  9. DEI-based classification cannot be configured for IP interfaces. MPLS EXP based classification is available for IP interfaces.