The FC of an access egress packet can be changed to redirect the packet to an alternate queue than the ingress FC determination would have used. The profile of an access egress packet can also be changed to modify the congestion behavior within the egress queue. In both cases, egress marking decisions are based on the new FC and profile, instead of the FC or profile determined at ingress.
The SAP egress QoS policy supports the use of reclassification rules to override the ingress FC and profile of packets that egress a SAP where the QoS policy is applied.
dot1p, IP precedence, and DSCP entries can be defined, each with an explicit FC or profile override parameters. The reclassification logic for each entry follows the same basic hierarchical behavior as the classification rules within the SAP ingress QoS policy. IP DSCP entries have the highest match priority, followed by IP precedence and dot1p.
If the IP precedence values overlap with DSCP values by matching the same IP header TOC field, the DSCP entry parameters override or remove the IP precedence parameters. When none of the matched entries override a parameter, the ingress classification is preserved; that is, the FC and profile assigned by SAP/network ingress classification rules is carried over and used at egress.
The egress queue shaper does not reassign the profile for the packet. By default, the profile is assigned a value of undefined at access SAP egress when the profile is not defined explicitly by the user in the service egress policy reclassification entry. A value of undefined specifies that the profile assigned at ingress is carried over. Therefore, the user can use egress reclassification to assign only an FC without specifying a profile. The profile assigned at ingress by either the ingress classification entry or the ingress shaper is carried over. The egress classification entry modifies the profile only if the user explicitly configures the profile as in or out.
This capability is supported on access SAP egress for all services.