Brocade FastIron Ethernet Switch Traffic Management Guide - Manual (Page 40)

NOTE
Queue cycles on the Brocade FastIron devices (except on ICX 6650) are based on bytes. These
devices service a given number of bytes (based on weight) in each queue cycle. The QoS WRR on
ICX 6650 is configured to operate in packet count mode.
• Strict Priority (SP) - SP 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 Brocade 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 Brocade device
assigns strict priority to traffic in qosp7 and qosp6, and weighted round robin priority to traffic in qosp0
through qosp5. Thus, the Brocade 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
Brocade stackable devices that are operating as members of a stack reserve queue 7 for stacking
functions. For more information, refer to
QoS for Brocade stackable devices on page 19.
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 as shown in
Bandwidth allocations of the hybrid WRR and SP queues on page 41.
Default bandwidth for combined SP and WRR queueing methods TABLE 23
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)
Quality of Service
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