Quality of Service (QoS): Managing Bandwidth More Effectively

Using QoS Classifiers To Configure Quality of Service for Outbound Traffic

Table 16-7.How the Switch Uses the ToS Configuration

Outbound Port

 

ToS Option:

 

IP Precedence

Differentiated Services

 

(Value = 0 - 7)

 

 

 

 

IP Packet in an Depending on the value of the IP Precedence bits

Untagged VLAN in the packet’s ToS field, the packet will go to one of four outbound port queues in the switch:

1 - 2 = low priority

0 - 3 = normal priority

4 - 5 = high priority

6 - 7 = high priority

For a given packet carrying a ToS codepoint that the switch has been configured to detect:

Change the codepoint according to the configured policy and assign the 802.1p priority specified for the new codepoint in the DSCP Policy Table (page 15-51).

Do not change the codepoint, but assign the 802.1p priority specified for the existing codepoint in the DSCP Policy Table (page 15-51).

Depending on the 802.1p priority used, the packet will leave the switch through one of the following queues:

1

- 2

= low priority

0

- 3

= normal priority

4

- 5

= high priority

6

- 7

= high priority

 

 

If No-override(the default) has been configured

 

 

for a specified codepoint, then the packet is not

 

 

prioritized by ToS and, by default, is sent to the

 

 

“normal priority” queue.

 

 

 

IP Packet in a

Same as above, plus the IP Precedence value (0

Same as above, plus the Priority value (0 - 7) will

Tagged VLAN

- 7) will be used to set a corresponding 802.1p

be used to set a corresponding 802.1p priority in

 

priority in the VLAN tag carried by the packet to

the VLAN tag carried by the packet to the next

 

the next downstream device.

downstream device. Where No-overrideis the

 

 

assigned priority, the VLAN tag carries a “0”

 

 

(normal priority) 802.1p setting.

 

 

 

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