Users Guide

class-map match-any class_dscp_40
match ip access-group dscp_40_non_ecn set-color yellow
match ip access-group dscp_40
class-map match-any class_dscp_50
match ip access-group dscp_50_non_ecn set-color yellow
match ip access-group dscp_50
policy-map-input pmap_dscp_40_50
service-queue 2 class-map class_dscp_40
service-queue 3 class-map class_dscp_50
The second example shows how to achieve the desired configuration by specifying ECN match criteria to
classify ECN-capable packets:
ip access-list standard dscp_50_ecn
seq 5 permit any dscp 50 ecn 1
seq 10 permit any dscp 50 ecn 2
seq 15 permit any dscp 50 ecn 3
ip access-list standard dscp_40_ecn
seq 5 permit any dscp 40 ecn 1
seq 10 permit any dscp 40 ecn 2
seq 15 permit any dscp 40 ecn 3
ip access-list standard dscp_50_non_ecn
seq 5 permit any dscp 50 ecn 0
ip access-list standard dscp_40_non_ecn
seq 5 permit any dscp 40 ecn 0
class-map match-any class_dscp_40
match ip access-group dscp_40_non_ecn set-color yellow
match ip access-group dscp_40_ecn
class-map match-any class_dscp_50
match ip access-group dscp_50_non_ecn set-color yellow
match ip access-group dscp_50_ecn
policy-map-input pmap_dscp_40_50
service-queue 2 class-map class_dscp_40
service-queue 3 class-map class_dscp_50
Using A Configurable Weight for WRED and ECN
The switch supports a user-configurable weight that determines the average queue size used in WRED
and Explicit Congestion Notification (ECN) operation on front-end I/O and backplane interfaces.
By default, the switch uses a weight factor of 0 (instantaneous ECN marking), which results in packet
dropping during times of network congestion based on the configured minimum and maximum WRED
thresholds. You can configure different weights for WRED and ECN operation to finely tune how different
types of traffic are handled when a WRED threshold is exceeded.
Benefits of Using a Configurable Weight for WRED with ECN
Using a configurable weight for WRED and ECN allows you to specify how the average queue size is
calculated. In WRED, the average queue size determines when a threshold is exceeded and packets are
dropped; in WRED with ECN, the average queue size determines when packets are marked for later
Quality of Service (QoS)
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