I was wondering if someone could help me better understand queue mappings. The
below is from the Cisco 3560 QoS guide.
Configuring the CoS-to-DSCP Map
You use the CoS-to-DSCP map to map CoS values in incoming packets to a DSCP
value that QoS uses internally to represent the priority of the traffic.
Configuring the DSCP-to-CoS Map
You use the DSCP-to-CoS map to generate a CoS value, which is used to select
one of the four egress queues.
If the above is true, why do we need four maps for queues?
cos-input-q cos-input queue map keyword
cos-output-q cos-output queue map keyword
dscp-input-q dscp-input queue map keyword
dscp-output-q dscp-output queue map keyword
Wouldn't we only need 2 or 3 since the newly formed CoS forms the map to egress
queue? When would we ever use the dscp-output-q? I assume it all comes down to
what you are trusting but this statement confuses me:
"You use the DSCP-to-CoS map to generate a CoS value, which is used to select
one of the four egress queues. "
Thanks for your input
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