Which of the following statements describes a queue’s weight parameter that is used in the hierarchical scheduling?

In Nokia's hierarchical scheduling, a two-pass process is used to allocate bandwidth. The first pass satisfies the Committed Information Rate (CIR) for queues and schedulers, typically based on strict priority. The weight parameter is not used in this pass. The second pass distributes any remaining bandwidth, known as above-CIR bandwidth. The weight parameter is used in this second pass to determine the proportion of this available above-CIR bandwidth that a queue (or scheduler) receives relative to other queues at the same hierarchical level and priority. A higher weight results in a larger share of the excess bandwidth, up to the queue's Peak Information Rate (PIR).

A. Scheduling up to CIR is governed by strict priority levels to ensure guaranteed bandwidth, not by the weight parameter, which is for sharing excess resources.

B. The term "priority" implies a strict ordering, whereas "weight" defines a proportional share. Weight is used for sharing among peers at the same priority level, not to set the priority itself.

C. The weight parameter is explicitly for sharing above-CIR bandwidth, not for distributing the guaranteed CIR bandwidth, which is allocated in a separate scheduling pass.

1. Nokia 7750 SR OS Quality of Service Guide, Release 21.10.R1, Section: "Hierarchical Scheduling".

Page 103, "Scheduler Operation": "The second pass is the “within-PIR” pass and is executed for each strict priority level. The scheduler distributes the remaining bandwidth to all queues and schedulers that are still not running at their defined PIR. The distribution of bandwidth is based on the configured weight of the queue or scheduler." This directly supports that weight is used for above-CIR (within-PIR) bandwidth sharing.

2. Nokia 7750 SR OS Quality of Service Guide, Release 21.10.R1, Section: "Hierarchical Scheduler Policy".

Page 111, "Scheduler Policy Operation": "The scheduler policy defines the hierarchy and operating parameters for a group of schedulers. The schedulers are defined with a parent parameter that is used to build the hierarchy... Each scheduler is also defined with a weight that is used to determine its precedence for excess bandwidth." This confirms weight's role in distributing excess (above-CIR) bandwidth within the hierarchy.

3. Nokia Application Note: Hierarchical QoS for the 7x50 SR/ESS Family, Part Number: AN-071-H-QOS, Section: "H-QoS Scheduling".

Section 3.2, "Two-Pass Scheduling Process": This document details the two-pass mechanism. It explains that the first pass allocates CIR, and the second pass uses a Weighted Round Robin (WRR) mechanism based on the configured weight to distribute bandwidth between CIR and PIR. This reinforces that weight is for the above-CIR pass.