An access egress packet’s forwarding class can be changed to redirect the packet to an alternate queue than the ingress forwarding class determination would have used. An access egress packet’s profile can also be changed to modifying the congestion behavior within the egress queue. In both cases, egress marking decisions are based on the new forwarding class and profile as opposed to the egress forwarding class or profile. The exception is when ingress remarking is configured. An ingress remark decision is not affected by egress forwarding class or egress profile overrides.
The SAP egress QoS policy allows reclassification rules that are used to override the ingress forwarding class and profile of packets that egress a SAP where the QoS policy is applied.
Dot1p, IP precedence, DSCP, and IP quintuple entries can be defined, each with an explicit forwarding class 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. Dot1p, IP precedence, and DSCP have the lowest match priority while the IP criteria (quintuple) entries have the highest.
When an optional parameter (such as profile) for Dot1p, IP precedence, or DSCP entries is not specified, the value from the lower priority IP quintuple match for that parameter is preserved. If the IP precedence values overlap with DSCP values in that they match the same IP header TOS 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.