The Committed Information Rate (CIR) for a queue performs two distinct functions:
profile marking by service ingress queues
Service ingress queues (configured in SAP ingress QoS policies or ingress queue group templates) mark packets in-profile or out-of-profile based on the CIR. For each packet in a service ingress queue, the CIR is compared to 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 current rate is above the threshold, the transmitted packet is internally marked out-of-profile. This operation can be overridden by configuring cir-non-profiling under the queue. This allows the queue scheduling priority to continue to be based on the below CIR or above CIR of the queue, but packets are not re-profiled depending on the state of the queue when they are scheduled (below CIR or above CIR). Instead, their profile state remains as out-of-profile, unless they are explicitly classified as in-profile or out-of-profile in which case they remain in-profile or out-of-profile.
scheduler queue priority
The scheduler serving a group of service ingress or egress queues prioritizes individual queues based on their current FIR, CIR, and PIR states. See Queue scheduling for more information about queue scheduling.
All router queues support the concept of in-profile, out-of-profile, together with inplus-profile and exceed-profile at egress only. The network QoS policy applied at network egress determines how or if the profile state is marked in packets transmitted into the service core network. If the profile state is marked in the service core packets, the packets are dropped preferentially at congestion points in the core as follows:
exceed-profile
out-of-profile
in-profile
inplus-profile
When defining the CIR for a queue, the value specified is the administrative CIR for the queue. The router has a number of native rates in hardware that it uses to determine the operational CIR for the queue. The user has some control over how the administrative CIR is converted to an operational CIR if the hardware does not support the exact CIR specified. See Adaptation rule for more information about the interpretation of the administrative CIR.
Although the router is flexible in how the CIR can be configured, there are conventional ranges for the CIR based on the forwarding class of a queue. A service queue associated with the high-priority class normally has the CIR threshold equal to the PIR rate, although the router allows the CIR to be provisioned to any rate below the PIR if this behavior is required. If the service queue is associated with a best-effort class, the CIR threshold is normally set to zero; however, this is flexible.
The CIR for a service queue is provisioned in ingress and egress service queues within service ingress QoS policies and service egress QoS policies respectively. CIRs for network queues are defined within network queue policies. CIRs for queue group instance queues are defined within ingress and egress queue group templates.