3. Discard eligibility indicator-based (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 SAS platforms.

3.1. DEI-based classification

DEI-based classification is supported on access ports, access-uplink ports, network ports and hybrid ports as applicable on 7210 SAS platforms. DEI bits in the received packet are used to determine the ingress profile for the packet. If DEI = 0 in the received packet 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, network port 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 the 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.

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 queued up on 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, allowing user an option to enable/disable use of DEI for ingress classification on a per port basis. The initial profile (also known as color) is based on the DEI/CFI bit. If DEI = 0 in the received packet, then the packet can be considered GREEN or in-profile and if DEI = 1, then packet can be considered YELLOW or out-of-profile 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. 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 QoS 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, the software allows only ONE of the following options to be configured:
    1. If DEI-based classification is enabled, network port ingress policy MUST use Dot1p classification criteria with DEI profile for all configured Dot1p values.
      OR
    2. If DEI-based classification is disabled, 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 is in use. In other words, DEI-based classification cannot be used when DSCP based classification is used.
  2. For network IP interface policies DEI-based classification is not supported. In other words, when using EXP-based classification, 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, access-uplink ports, network ports, and hybrid ports. DEI bits 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 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 port egress on access ports and access-uplink ports on 7210 SAS devices configured in access-uplink mode.
  3. 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).
  4. By default, in-profile packets are marked with DEI bit = 0 and out-of-profile packets are marked with DEI bit = 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 command.
Note:

For information about the commands for configuring DEI, see Network QoS policies, Network queue QoS policy command reference, Access egress QoS policies on 7210 SAS-T, 7210 SAS-Sx/S 1/10GE, and 7210 SAS-Sx 10/100GE, Access egress QoS policies for 7210 SAS-Mxp, 7210 SAS-R6, and 7210 SAS-R12, Access egress QoS policy command reference, and the 7210 SAS-Mxp, R6, R12, S, Sx, T Basic System Configuration Guide.

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 network port ingress policy, only Dot1p classification can be used.
  3. DEI classification must be disabled on that port prior to changing the mode from one mode (access/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.
  5. While enabling DEI-based policing on a port, if it is a hybrid port, then 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.
    Note:

    1. Only after attaching a network port ingress QoS policy as mentioned above, can users enable DEI classification on a port.
    2. For more information about DEI classification on a LAG and port, refer to the 7210 SAS-Mxp, R6, R12, S, Sx, T Interface Configuration Guide.
  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. In other words, 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 profile, if DEI classification is enabled on this port.
    Note:

    1. DEI-based classification cannot be configured for IP interfaces.
    2. Only MPLS EXP-based classification is available for IP interfaces.