LAN QoS

Interface commands:
mls qos trust dscp
mls qos trust cos
mls qos trust device cisco-phone

default, or untrusted, state – any marked packets recieved will be overwritten with a value of 0

CoS field only on dot1.q ‘trunked’ packets

Use the MQC to mark packets, if your CoS-to-DSCP map is already marking one value and you need another:

class-map match-all video
match access-group 1
!
access-list 1 permit 10.2.2.2
!
policy-map video
class video
set ip dscp 34
!
int f0/0
service-policy input video

Congestion Management (Queuing)
Weighted Round Robin (WRR) scheduled
Strict Priority & WRR scheduled

Assign CoS values 0-7 to one of the four egress queues:
wrr-queue cos-map 1 0 1 -> queue 1 CoS value 0,1
wrr-queue cos-map 2 2 -> queue 2 CoS value 2
wrr-queue cos-map 3 3 4 6 7 -> queue 3 CoS value 3,4,6,7 – 6 and 7 placed in queue 3 for routing and BPDU and should not be placed any lower due to possible starvation
wrr-queue cos-map 4 5 -> queue 4 ‘priority queue’

WRR Scheduling:
eliminates starving lower priority queues by assinging a weight to each queue, but NO DELAY GUARANTEE
wrr-queue bandwidth 5 10 25 50 -> 5 packets in queue 1, 10 in queue 2, 25 in queue 3, 50 in queue 4

Strict Priority and WRR Scheduling:
wrr-queue bandwidth 5 10 25 0 -> 5 packets in queue 1, 10 in queue 2, 25 in queue 3, 0 makes PRIORITY QUEUE

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