Interface Configuration
7750 SR Interface Configuration Guide Page 119
Per-fp-sap-instance
Per-fp-sap-instance optimization for LAG ports provides the ability to reduce the number of SAP
instance resources consumed by each SAP on a lag.
When the feature is enabled, in the config>lag>access context, a single SAP instance is allocated
on ingress and on egress per each forwarding path instead of one per port. Thanks to an optimized
resource allocation, the SAP scale on a line card will increase, if a LAG has more than one port on
that line card. Because SAP instances are only allocated per forwarding path complex, h/w
reprogramming must take place when as result of LAG links going down or up, a SAP is moved
from one LAG port on a given line card to another port on a given line card within the same
forwarding complex. This results in an increased data outage when compared to per-fp-sap-
instance feature being disabled. During the reprogramming, failover queues are used when SAP
queues are reprogrammed to a new port. Any traffic using failover queues will not be accounted
for in SAPs statistics and will be processed at best-effort priority.
The following rules apply when configuring per-fp-sap-instance on a given LAG:
• Minimum chassis mode D is required.
• Per-fp-sap-ingress-queuing and per-fp-sap-egr-queuing must be enabled.
• The functionality can be enabled/disabled on LAG with no member ports only. Services
can be configured.
Other caveats:
• SAP instance optimization applies to LAG-level. Whether a LAG is sub-divided into sub-
groups or not, the resources are allocated per forwarding path for all complexes LAG’s
links are configured on (i.e. irrespective of whether a given sub-group a SAP is configured
on uses that complex or not).
• Egress statistics continue to be returned per port when SAP instance optimization is
enabled. If a LAG links are on a single forwarding complex, all ports but one will have no
change in statistics for the last interval – unless a SAP moved between ports during the
interval.
• Rollback that changes per-fp-sap-instance configuration is service impacting.
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