Cisco WS-C3750-48PS-S Software Configuration Manual page 630

Understanding QoS
Figure 32-3 Classification Flowchart
configuration for classification.
IP and
non-IP
traffic
Check if packet came
with CoS label (tag).
Yes
Use CoS Assign default
from frame. port CoS.
Generate DSCP from
CoS-to-DSCP map.
Use the DSCP value to
generate the QoS label.
Done
Are there any (more) QoS ACLs
configured for this interface?
Yes
Read next ACL. Is there
a match with a "permit" action?
Yes
Assign the DSCP or CoS as specified
by ACL action to generate the QoS label.
Catalyst 3750 Switch Software Configuration Guide
32-6
Start
Read ingress interface
Trust DSCP or Trust IP
IP precedence precedence
(non-IP traffic). (IP traffic).
No
Generate the DSCP based on
IP precedence in packet. Use
the IP-precedence-to-DSCP
map. Use the DSCP value to
generate the QoS label.
No
No
Assign the default
DSCP (0).
Done
Trust CoS (IP and non-IP traffic).
Trust DSCP (IP traffic).
Assign DSCP identical
to DSCP in packet.
(Optional) Modify the
DSCP by using the
DSCP-to-DSCP-mutation
map. Use the DSCP
value to generate
the QoS label.
Done
Check if packet came
with CoS label (tag).
Yes
Use the CoS value to
generate the QoS label.
Generate the DSCP by using
the CoS-to-DSCP map.
Chapter 32 Configuring QoS
No
Assign the default port
CoS and generate a
DSCP from the
CoS-to-DSCP map.
Done
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