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Guidelines for Configuring ECN for Classifying and
Color-Marking Packets
Keep the following points in mind while configuring the marking and mapping of incoming packets using ECN fields in IPv4
headers:
● Currently Dell EMC Networking OS supports matching only the following TCP flags:
○ ACK
○
FIN
○ SYN
○ PSH
○ RST
○ URG
In the existing software, ECE/CWR TCP flag qualifiers are not supported.
● Because this functionality forcibly marks all the packets matching the specific match criteria as ‘yellow’, Dell EMC
Networking OS does not support Policer based coloring and this feature concurrently.
● If single rate two color policer is configured along with this feature, then by default all packets less than PIR would be
considered as “Green” But ‘Green’ packets matching the specific match criteria for which ‘color-marking’ is configured will
be over-written and marked as “Yellow”.
● If two rate three color policer is configured along with this feature then,
○ x < CIR – will be marked as “Green”
○ CIR < x< PIR – will be marked as “Yellow”
○ PIR < x – will be marked as “Red”
But ‘Green’ packets matching the specific match criteria for which ‘color-marking’ is configured will be over-written and marked
as “Yellow”.
Sample configuration to mark non-ecn packets as “yellow” with
Multiple traffic class
Consider the example where there are no different traffic classes that is all the packets are egressing on the default ‘queue0’.
Dell EMC Networking OS can be configured as below to mark the non-ecn packets as yellow packets.
!
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 this policy-map “ecn_0_pmap” will mark all the packets with ‘ecn == 0’ as yellow packets on queue0 (default queue).
Quality of Service (QoS)
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