Quality of Service (QoS): Managing Bandwidth More Effectively
Introduction
■ Configuring a priority for outbound packets and a service (prior- ity) policy for use by downstream devices:
• DSCP Policy: This feature enables you to set a priority policy in outbound IP packets. (You can configure downstream devices to read and use this policy.) This method is not dependent on
– Change the codepoint (the upper six bits) in the ToS byte.
– Set a new 802.1p priority for the packet.
(Setting DSCP policies requires IPv4 inbound packets. Refer to the “IPv4” entry under “Terminology” on page
• 802.1p Priority Rules: An outbound,
| switch. This priority setting ranges from 0 to 7, and can be used by |
| downstream devices having up to eight outbound port queues. Thus, |
| while packets within the switch are assigned to the outbound queue |
| priorities as shown in table |
| priority for use by downstream devices that implement different |
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| an 802.1p priority setting, QoS can override this setting if configured |
| with an 802.1p priority rule to do so. |
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N o t e | If your network uses only one VLAN (and therefore does not require |
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| your traffic by configuring the ports as tagged VLAN members on the |
| links between devices you want to honor traffic priorities. |
| Rule and Policy Limits: The following maximum number of priority |
| rules and/or DSCP policies, in any combination, are allowed: |
| •2510G Switches: 120 |
| You can configure a QoS priority of 0 through 7 for an outbound packet. When |
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| the packet is then sent to a port, the QoS priority determines which outbound |
queue the packet uses:
TableQoS Priority Setting | Outbound Port Queue |
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1 - 2 | low priority |
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0 - 3 | normal priority |
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4 - 5 | medium priority |
6 - 7 | high priority |
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