Brocade FastIron Ethernet Switch Traffic Management Guide - Manual (Page 39)

The above table includes values for default, non-jumbo mode WRR for a stand-alone system. The
hardware queues are calculated using default qosp values from the Default values for scheduling type
for stacking and stand-alone systems (for ICX 6430 platforms) table as follows:
• Queue 3 = 75% (qosp7)
• Queue 2 = 3% (qosp5) + 7% (qosp6) = 10%
• Queue 1 = 3% (qosp2) + 3% (qosp3) + 3% (qosp4) = 9%
• Queue 0 = 3% (qosp0) + 3% (qosp1) = 6%
The hardware queues for mixed WRR and SP mode are calculated as follows:
• Queue 3 is Strict Priority as the default value for qosp7 is SP
• Queue 2 is Strict Priority as default values for qosp5 and qosp6 are SP
• Queue 1 = 15% (qosp2) + 15% (qosp3) + 40% (qosp4) = 70%
• Queue 0 = 15% (qosp0) + 15% (qosp1) = 30%
NOTE
If any qosp value is SP, then the weight of the hardware queue is SP.
Scheduling QoS information
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 mechanism.
Scheduling for the SX-FI48GPP module
The SX-FI48GPP module supports scheduling at the front-end and back-end NP. If egress congestion
occurs at the front-end NP of the SX-FI48GPP module, scheduling is based on four queues instead of
eight. For more information on default configuration for 8 to 4 queue mapping, refer to the Priority
queues for the SX-F148GPP table. If egress congestion occurs at the back-end of the SX-FI48GPP
module, then scheduling is based on eight queues. When SX- FI48GPP ports are running at a reduced
speed (100 Mbps or 10 Mbps), egress congestion usually occurs at the front-end NP.
QoS queuing methods
The following QoS queuing methods are supported in all IronWare releases for the FastIron devices:
• Weighted Round Robin (WRR) - WRR 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 (SP) under weighted queuing. Attempts
to change the qosp7 setting will be 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.
Scheduling QoS information
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