Quality of Service
Quality of Service (QoS)
Standards Number of queues Packet classifiers
WFQ queue mode
Priority queue mode
Shaping queue mode
IEEE 802.1P, WRED, WFQ, IP TOS based on RFC1275
4 queues per port
Static classifier: All packets received on a port are assigned to a single queue
Dynamic classifier: Packets are assigned to a queue based on their IP TOS or 802.1P
Administrator selectable queue weight. Queue weights are calculated as a percentage of the cumulative weights.
Using WFQ, any queue can burst up to the maximum bitrate of the line. This can occur if no packets in a higher priority queue are waiting to transmit. If you wish to apply strict rules and limit a low priority queue to a fixed amount, use the “egress shaping” command.
Strict priority over all lower queues. Note that Priority queuing can be mixed with other queuing methods to provide a low latency, low jitter service for sensitive services such as VoIP. For example, if the critical queue were assigned a Priority mode, then those packets would transmit on the port before other packets in the buffers.
Apply traffic shaping rules to individual queues. Each queue is assigned a fixed amount of bitrate. The cumulative bitrate of all the queues should not exceed the total line rate of the port.
QoS commands and concepts
network qos [enable disable]
Enable qos support. To disable qos, use network qos disable
network qos interface priority
Sets the packet classifier mode for the port receiving packets.
Where;
Mode is dynamic or static. Dynamic classifier will read the IP TOS or 802.1P precedence bit of the incoming packet. Static classifier assigns all packets received on the port to one of the four queues
Level is the default queue for packets received on the port. When the mode is dynamic, then level is assigned to packets that do not match the classifier. When the mode is set to static, then level applies to all packets received on the port.
The four queues are critical, high, medium, and low.
network qos classification <method>
where method is either 802.1p or tos
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