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When you use ECN to classify and color-mark packets in an ingress class map, take into account:
● When all matching packets are marked for yellow treatment, policer-based coloring is not supported at the same time.
● If a single-rate two-color policer is configured at the same time as ECN-matched packets are set for yellow handling, by
default all packets less than PIR are marked for “green” handling. All green packets selected by ECN match criteria and
color-marked yellow are over-written and marked for yellow handling.
● If a two-rate three-color policer is configured at the same time as ECN-matched packets are set for yellow handling:
○ x < CIR is marked as green.
○ CIR < x< PIR is marked as yellow.
○ PIR < x is marked as red.
Green packets matching the ECN criteria for which yellow color-marking is configured are overwritten and marked as yellow.
Example: Color-marking non-ECN Packets in One Traffic Class
The following example shows how to mark non-ECN packets for “yellow” handling when all packets egress on the default queue
0. Non-ECN-capable packets have the ECN field in their packet headers set to 0.
ip access-list standard ecn_0
seq 5 permit any ecn 0
class-map match-any ecn_0_cmap
match ip access-group ecn_0 set-color yellow
policy-map-input ecn_0_pmap
service-queue 0 class-map ecn_0_cmap
Applying the policy map “ecn_0_pmap” marks all incoming packets with the ECN field set to 0 for “yellow” handling on queue 0
(default queue).
Example: Color-marking non-ECN Packets in Different Traffic
Classes
The following examples both show how to mark non-ECN packets for “yellow” handling when packets with DCSP 40 egress on
queue 2 and packets with DSCP 50 egress on queue 3. Non-ECN-capable packets have the ECN field in their packet headers
set to 0.
The first example shows how to achieve the desired configuration without specifying ECN match criteria to classify ECN-
capable packets:
ip access-list standard dscp_50
seq 5 permit any dscp 50
ip access-list standard dscp_40
seq 5 permit any dscp 40
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
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
Quality of Service (QoS)
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