Qos Priorities; Qos Algorithm - HP ProCurve 9304M Manual Supplement

QoS Priorities

You can select one of the following priorities:
• 0 or 1 – These priorities correspond to queue 0, the normal priority queue.
• 2 or 3 – These priorities correspond to queue 1, a higher priority queue.
• 4 or 5 – These priorities correspond to queue 2, a higher priority queue.
• 6 or 7 – These priorities correspond to queue 3, the highest priority queue.
Each port and each module has four queues for outbound traffic.
NOTE: Each module also has a queue in which the module places packets for prioritized transmission onto the
backplane to other modules. However, you do not need to configure these queues. The prioritization queues you
assign to interfaces are used for traffic waiting to be sent to a module for transmission on the interface.

QoS Algorithm

QoS queues are serviced using a chained round-robin scheme. This scheme services each of the four queues on
a given port during a single queue cycle. A queue cycle is one full pass through all four queues. Each queue has
a non-configurable weight that determines how many packets the system processes for each queue during a given
cycle and how many times the queue is processed during the cycle.
You can calculate the minimum guaranteed percentage of a port's bandwidth a set of queue weights yields by
using the following equations:
q3/(q3 + 1) = p3
(1 - p3) * q2/(q2 + 1) = p2
(1 - p3 - p2) * q1/(q1 + 1) = p1
(1 - p3 - p2 -p1) = p0
where:
• p3 is the percentage for queue 3
• p2 is the percentage of what is left over from queue 3 that is allocated to queue 2
• p1 is the percentage of what is left over from queue 2 that is allocated to queue 1
• p0 is the percentage of what is left over from queue 1 that is allocated to queue 0
Quality of Service (QoS) Algorithms
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