Service Egress and Ingress QoS Policies
Quality of Service Guide 197
Overrides
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 (in or out) can also be changed to modifying the congestion behavior
within the egress queue. In both cases, egress marking decisions will be 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 will not be
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 will match the same IP header TOS field, the DSCP entry
parameters will override or remove the IP precedence parameters. When none of the matched
entries override a parameter, the ingress classification is preserved.
Egress Criteria Classification Directly to Policer
It is possible to classify traffic directly to a policer, independent of the policer/queue assigned
to the traffic’s forwarding class. This is supported at SAP egress by configuring a policer in
the action statement within an ip-criteria or ipv6-criteria statement.
The policed traffic by default exits through one of the following methods:
• A queue in the policer-output-queues queue group that is automatically created on
an access or hybrid port with the queue used that was chosen by the forwarding class
definition in that queue group. If the forwarding class is modified in the action
statement then the new forwarding class selects the queue to be used.
• A specific queue in a user configured queue group. For SAP egress, this requires the
use of the port-redirect-queue-group queue parameter in the criteria action
statement with the queue group name being specified when the egress QoS policy is
applied to the SAP. For subscribers, the queue group to be used is selected using the
inter-dest-id associated with the subscriber and configured as the host-match dest
under the port access queue group configuration.
To Next Page
Loading...
