The exhibit displays the creation of a SAP-ingress QoS policy (ID 100) designed to classify ICMP traffic into forwarding class "af", which is then mapped to queue 3. The observed behavior, where all traffic is placed in queue 1, indicates that the default QoS handling is being used. In Nokia's SR OS, a QoS policy has no effect on traffic until it is explicitly applied to a service object, such as a Service Access Point (SAP). The most probable reason for the observed behavior is that the operator has created the policy but has not yet associated it with the specific SAP's ingress context. Without this association, the SAP uses the default QoS policy, which maps all traffic to the Best Effort (BE) forwarding class and directs it to queue 1.

A. This describes the default behavior but does not explain the root cause of why the specific ICMP classification rule is being ignored.

B. If the SAP were shut down, no traffic would be processed or queued, contradicting the problem description.

C. The configuration match protocol icmp is the correct syntax for matching ICMP traffic within an IP criteria entry in SR OS.

D. The absence of a CIR or rate configuration on a queue does not prevent it from accepting packets; it simply uses default scheduling parameters.

1. Nokia 7750 SR OS Quality of Service Guide, Release 21.10.R1, Document Part Number: 3HE 17279 AAAD TQZZA, Section: SAP Ingress Policies. This guide details the process for QoS policy configuration. It distinguishes between creating a policy (in the config>qos context) and applying it to a service entity. The section "Applying SAP Ingress Policies" states: "You can apply SAP ingress policies to ingress SAPs... Use the following CLI syntax to apply a SAP ingress policy: config>service>sap>ingress>qos policy-id". This confirms that application is a separate, mandatory step for the policy to take effect.

2. Nokia 7750 SR OS Quality of Service Guide, Release 21.10.R1, Document Part Number: 3HE 17279 AAAD TQZZA, Section: Default SAP Ingress Policy (Policy ID 1). This section describes the system's behavior when no explicit policy is applied to a SAP. It states: "When a SAP is created, the default SAP ingress QoS policy is applied... All traffic is treated as in-profile Best Effort (BE). The default policy creates all 8 forwarding class queues." This directly supports the observation that without an applied policy, all traffic defaults to the BE forwarding class, which is mapped to queue 1.