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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
(Value = 0 - 7)
Differentiated Services
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-override is the
assigned priority, the VLAN tag carries a “0”
(normal priority) 802.1p setting.
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