Which of the following statements about scheduling on the Nokia 7750 SR is FALSE?

The statement is false because when a queue operates in priority-mode, the egress profile is re-determined based on the scheduling loop that serviced the packet, not the ingress profile. Low-priority traffic is explicitly directed to the above-CIR (or PIR) scheduling loop. Any packet serviced from the above-CIR loop is re-marked as out-of-profile at egress. Therefore, the claim that low-priority traffic scheduled in the above-CIR loop will be considered in-profile at egress is incorrect; it will be considered out-of-profile.

B. This is true. In priority-mode, any packet serviced from the above-CIR loop, including high-priority traffic that has overflowed the CIR, is re-marked as out-of-profile at egress.

C. This is true. In profile-mode, traffic scheduled above-CIR must have been marked out-of-profile at ingress. The egress profile preserves the ingress profile, so it remains out-of-profile.

D. This statement's consequence is true. Profile-mode preserves the ingress profile state at egress. Although the premise is flawed (in-profile traffic is scheduled within-CIR), the principle described is correct.

1. Nokia 7750 SR OS Quality of Service Guide, Release 21.10.R1, Document ID: DG-2110-0111-SR-QSG.

Section: Egress Profile Re-marking: "For priority-based CIR/PIR scheduling, the egress marking is based on the scheduling of the packet. If the packet is scheduled as part of the queue’s CIR, it is marked in-profile. If it is scheduled as part of the queue’s PIR, it is marked out-of-profile." This directly contradicts statement A and supports the reasoning for B.

Section: Queue Scheduling Modes (Profile Mode): "When a queue is in profile mode, the profile of the packet is used to determine how the packet is scheduled... The egress profile of the packet is the same as the ingress profile." This supports the reasoning for C and D.

Section: Queue Scheduling Modes (Priority Mode): "When a queue is in priority mode, the priority of the packet, not its profile, is used to determine how the packet is scheduled. High-priority packets are serviced by the queue’s scheduler before low-priority packets." This clarifies that low-priority traffic is serviced after high-priority, typically from the above-CIR portion.