Quality of Service (QoS): Managing Bandwidth More Effectively
Using QoS Types To Configure QoS for Outbound Traffic
TableOutbound Port |
| ToS Option: |
| IP Precedence | Differentiated Services |
| (Value = 0 - 7) |
|
IP Packet Sent Out | Depending on the value of the IP | For a given packet carrying a ToS codepoint that the switch has |
an Untagged Port | Precedence bits in the packet’s | been configured to detect: |
in a VLAN | ToS field, the packet will go to one | • Change the codepoint according to the configured policy and |
| of four outbound port queues in | assign the 802.1p priority specified for the new codepoint in |
| the switch: | |
| 1 - 2 = low priority | • Do not change the codepoint, but assign the 802.1p priority |
| 0 - 3 = normal priority | specified for the existing codepoint in the DSCP Policy Table |
| 4 - 5 = high priority | |
| 6 - 7 = high priority | Depending on the 802.1p priority used, the packet will leave the |
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| switch through one of the following queues: |
|
| 1 - 2 = low priority |
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| 0 - 3 = normal priority |
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| 4 - 5 = high priority |
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| 6 - 7 = high priority |
|
| If |
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| codepoint, then the packet is not prioritized by ToS and, by |
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| default, is sent to the “normal priority” queue. |
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IP Packet Sent Out | Same as above, plus the IP Prece- | Same as above, plus the Priority value (0 - 7) will be used to set |
an Untagged Port | dence value (0 - 7) will be used to | a corresponding 802.1p priority in the VLAN tag carried by the |
in a VLAN | set a corresponding 802.1p priority | packet to the next downstream device. Where |
| in the VLAN tag carried by the | assigned priority, the VLAN tag carries a “0” (normal priority) |
| packet to the next downstream | 802.1p setting if not prioritized by other QoS types. |
| device. Refer to table |
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ToS Byte IP | Corresponding | Service Priority Level |
Precedence Bits | 802.1p Priority |
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000 | 1 | Lowest |
001 | 2 | Low |
002 | 0 | Normal |
003 | 3 |
|
004 | 4 |
|
005 | 5 |
|
006 | 6 |
|
007 | 7 | Highest |
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