Selecting The Queuingm; Configuring The Queues - Foundry Networks Switch and Router Installation And Configuration Manual

As the packet moves through the system, if the packet matches other QoS allocations you have configured, the
packet is moved into a higher queue accordingly. For example, if the TOS values place the packet in qosp1, but
the packet is part of a port-based VLAN that is in qosp3, the packet enters queue qosp3. Packets can enter
higher queues but never enter lower queues as they move through the system.
NOTE: The TOS mapping applies only to IP packets received on 10/100 ports. It does not apply to Gigabit or
POS ports.
Queuing Methods
You can configure a Chassis device to use one of the following queuing methods:
• Weighted – A weighted fair queuing algorithm is used to rotate service among the four queues. The rotation
is based on the weights you assign to each queue. This is the default queuing method and uses a default set
of queue weights. This method rotates service among the four queues, forwarding a specific number of
packets in one queue before moving on to the next one.
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.
• Strict – 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.
Selecting the Queuing Method
Foundry Chassis devices (including the TurboIron/8) use the weighted fair queuing method of packet prioritization
by default. To change the method to strict queuing or back to weighted fair queuing, use one of the following
methods.
USING THE CLI
To change the queuing method from weighted fair queuing to strict queuing, enter the following commands:
BigIron(config)# qos mechanism strict
BigIron(config)# write memory
Syntax: [no] qos mechanism strict | weighted
To change the method back to weighted fair queuing, enter the following commands:
BigIron(config)# qos mechanism weighted
BigIron(config)# write memory
USING THE WEB MANAGEMENT INTERFACE
1. Log on to the device using a valid user name and password for read-write access. The System configuration
dialog is displayed.
2. Click on the Weighted or Strict radio button next to QoS.
3. Click the Apply button to save the change to the device's running-config file.
4. Select the Save link at the bottom of the dialog, then select Yes when prompted to save the configuration
change to the startup-config file on the device's flash memory.

Configuring the Queues

Each of the four queues has the following configurable parameters:
• The queue name
• The minimum percentage of a port's outbound bandwidth guaranteed to the queue
December 2000
IronClad Quality of Service (QoS)
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