SR policies provide the ability to collect statistics for ingress and egress traffic. In both cases, traffic statistics are collected without any forwarding class or QoS distinction.
Traffic statistics collection is enabled as follows:
config>router>segment-routing>sr-policies>ingress-statistics
Ingress traffic collection only applies to binding-sid SR policies as the statistic index is attached to the ILM entry for that label. The traffic statistics provide traffic for all the instances that share the binding SID. The statistic index is released and statistics are lost when ingress traffic statistics are disabled for that binding SID, or the last instance of a policy using that label is removed from the database.
config>router>segment-routing>sr-policies>egress-statistics
Egress traffic statistics are collected globally, for all policies at the same time. Both static and signaled policies are subject to traffic statistics collection. Statistic indexes are allocated per segment list, which allows for a fine grain monitoring of traffic evolution. Also, statistic indexes are only allocated at the time the segment list is effectively programmed. However, the system allocates at most 32 statistic indexes across all the instances of a policy. Therefore, in the case where an instance of a policy is deprogrammed and a more preferred instance is programmed, the system behaves as follows:
If the segment list IDs of the preferred instance are different from any of the segment list IDs of any previously programmed instance, the system allocates new statistic indexes. While that condition holds, the statistics associated with a segment list of an instance strictly reflect the traffic that used that segment list in that instance.
If some of the segment list IDs of the preferred instance are equal to any of the segment list IDs of any previously programmed instance, the system reuses the indexes of the preferred instance and keeps the associated counter value and increment. In this case, the traffic statistics provided per segment list not only reflect the traffic that used that segment list in that instance. It incorporates counter values of at least another segment-list in another instance of that policy.
In all cases, the aggregate values provided across all instances truly reflect traffic over the various instances of the policy.
Statistic indexes are not released at deprogramming time. They are, however, released when all the instances of a policy are removed from the database, or when the egress-statistics command is disabled.