QoS scheduling and queuing methods

Scheduling is the process of mapping a packet to an internal forwarding queue based on its QoS information and servicing the queues according to a queuing method.

The following QoS queuing methods are supported for the FastIron devices:
  • Weighted Round Robin (WRR)—This method ensures that all queues are serviced during each cycle. A WRR algorithm is used to rotate service among the eight queues on the FastIron devices. The rotation is based on the weights you assign to each queue. This method rotates service among the queues, forwarding a specific number of packets in one queue before moving on to the next one.
    Note: In stacking mode, the qosp7 queue is reserved as Strict Priority under weighted queuing. Attempts to change the qosp7 setting are ignored.

    WRR is the default queuing method and uses a default set of queue weights.

    The number of packets serviced during each visit to a queue depends on the percentages you configure for the queues. The software automatically converts the percentages you specify into weights for the queues.

    Note: Queue cycles on the FastIron devices are based on bytes. These devices service a given number of bytes (based on weight) in each queue cycle.
  • Strict Priority (SP)—This ensures service for high-priority traffic. The software assigns the maximum weights to each queue, to cause the queuing mechanism to serve as many packets in one queue as possible before moving to a lower queue. This method biases the queuing mechanism to favor the higher queues over the lower queues.

    For example, strict queuing processes as many packets as possible in qosp3 before processing any packets in qosp2, then processes as many packets as possible in qosp2 before processing any packets in qosp1, and so on.

  • Hybrid WRR and SP—This configurable queueing mechanism combines both the SP and WRR mechanisms. The combined method enables the device to give strict priority to delay-sensitive traffic such as VoIP traffic, and weighted round robin priority to other traffic types.

    By default, when you select the combined SP and WRR queueing method, the device assigns strict priority to traffic in qosp7 and qosp6, and weighted round robin priority to traffic in qosp0 through qosp5. Thus, the device schedules traffic in queue 7 and queue 6 first, based on the strict priority queueing method. When there is no traffic in queue 7 and queue 6, the device schedules the other queues in round-robin fashion from the highest priority queue to the lowest priority queue.

    Note: Stackable devices that are operating as members of a stack reserve queue 7 for stacking functions. For more information, refer to QoS for Ruckus ICX stackable devices.

    By default, when you specify the combined SP and WRR queuing method, the system balances the traffic among the queues as shown in the following table. If desired, you can change the default bandwidth values.

Table 1. Default bandwidth for combined SP and WRR queueing methods

Queue

Default bandwidth

qosp7

Strict Priority (highest priority)

qosp6

Strict Priority

qosp5

25%

qosp4

15%

qosp3

15%

qosp2

15%

qosp1

15%

qosp0

15% (lowest priority)