Cisco Catalyst 2960 Series, Configuration Manual

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Table 57: Non- IP Traffic Classifications
Description Non-IP Traffic Classification
Trust the CoS value in the incoming frame (configure the
port to trust CoS), and then use the configurable
CoS-to-DSCP map to generate a DSCP value for the packet.
Layer 2 ISL frame headers carry the CoS value in the 3
least-significant bits of the 1-byte User field.
Layer 2 802.1Q frame headers carry the CoS value in the 3
most-significant bits of the Tag Control Information field.
CoS values range from 0 for low priority to 7 for high
priority.
Trust the CoS value
Trust the DSCP or trust IP precedence value in the incoming
frame. These configurations are meaningless for non-IP
traffic. If you configure a port with either of these options
and non-IP traffic is received, the switch assigns a CoS value
and generates an internal DSCP value from the CoS-to-DSCP
map. The switch uses the internal DSCP value to generate
a CoS value representing the priority of the traffic. Trust the DSCP or trust IP precedence value
Perform the classification based on a configured Layer 2
MAC access control list (ACL), which can examine the
MAC source address, the MAC destination address, and
other fields. If no ACL is configured, the packet is assigned
0 as the DSCP and CoS values, which means best-effort
traffic. Otherwise, the policy-map action specifies a DSCP
or CoS value to assign to the incoming frame. Perform classification based on configured
Layer 2 MAC ACL
After classification, the packet is sent to the policing and marking stages.
IP Traffic Classification
The following table describes the IP traffic classification options for your QoS configuration.
Table 58: IP Traffic Classifications
Description IP Traffic Classification
Trust the DSCP value in the incoming packet (configure the port to trust
DSCP), and assign the same DSCP value to the packet. The IETF defines
the 6 most-significant bits of the 1-byte ToS field as the DSCP. The priority
represented by a particular DSCP value is configurable. DSCP values range
from 0 to 63.
You can also classify IP traffic based on IPv6 DSCP.
For ports that are on the boundary between two QoS administrative
domains, you can modify the DSCP to another value by using the
configurable DSCP-to-DSCP-mutation map.
Trust the DSCP value
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
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Information About QoS