The CIR for a queue defines a limit for scheduling. Packets queued at service ingress queues are serviced by in-profile or out-of-profile schedulers based on the queue’s CIR and the rate at which the packets are flowing. For each packet in a service ingress queue, the CIR is checked with the current transmission rate of the queue. If the current rate is at or below the CIR threshold, the transmitted packet is internally marked in-profile. If the flow rate is above the threshold, the transmitted packet is internally marked out-of-profile.
All 7705 SAR queues support the concept of in-profile and out-of-profile. The network QoS policy applied at network egress determines how or if the profile state is marked in packets transmitted into the network core. This is done by enabling or disabling the appropriate priority marking of network egress packets within a particular forwarding class. If the profile state is marked in the packets that are sent toward the network core, then out-of-profile packets are preferentially dropped over in-profile packets at congestion points in the network.
When defining the CIR for a queue, the value specified is the administrative CIR for the queue. The 7705 SAR maps a user-configured value to a hardware supported rate that it uses to determine the operational CIR for the queue. The user has control over how the administrative CIR is converted to an operational CIR if a slight adjustment is required. The interpretation of the administrative CIR is discussed in Adaptation Rule.
The CIR value for a service queue is assigned to ingress and egress service queues based on service ingress QoS policies and service egress QoS policies, respectively.
The CIR value for a network queue is defined within a network queue policy specifically for the forwarding class. The queue-id parameter links the CIR values to the forwarding classes. The CIR values for the forwarding class queues are defined as a percentage of the network interface bandwidth.