Dell S4820T Configuration Manual page 781

Until Release 9.3(0.0), support is available for classifying traffic based on the 6-bit DSCP field of the IPv4
packet.
As a part of this feature, the 2-bit ECN field of the IPv4 packet will also be available to be configured as
one of the match qualifier. This way the entire 8-bit ToS field of the IPv4 header shall be used to classify
traffic.
The Dell Networking OS Release 9.3(0.0) supports the following QOS actions in the ingress policy based
QOS:
1. Rate Policing
2. Queuing
3. Marking
For the L3 Routed packets, the DSCP marking is the only marking action supported in the software. As a
part of this feature, the additional marking action to set the "color" of the traffic will be provided.
Until Release 9.3(0.0), the software has the capability to qualify only on the 6-bit DSCP part of the ToS
field in IPv4 Header. You can now accept and process incoming packets based on the 2-bit ECN part of
the ToS field in addition to the DSCP categorization. The IPv4 ACLs (standard and Extended) are
enhanced to add this qualifier. This new keyword 'ecn' is present for all L3 ACL types (TCP/UDP/IP/ICMP)
at the level where the 'DSCP' qualifier is positioned in the current ACL commands.
Dell Networking OS supports the capability to contain DSCP and ECN classifiers simultaneously for the
same ACL entry.
You can use the ecn keyword with the ip access-list standard, ip access-list extended, seq, and permit
commands for standard and extended IPv4 ACLs to match incoming packets with the specified ECN
values.
Similar to 'dscp' qualifier in the existing L3 ACL command, the 'ecn' qualifier can be used along with all
other supported ACL match qualifiers such as SIP/DIP/TCP/UDP/SRC PORT/DST PORT/ ICMP.
Until Release 9.3(0.0), ACL supports classification based on the below TCP flags:
• ACK
• FIN
• SYN
• PSH
• RST
• URG
You can now use the 'ecn' match qualifier along with the above TCP flag for classification.
The following combination of match qualifiers is acceptable to be configured for the Dell Networking OS
software through L3 ACL command:
• Classification based on DSCP only
• Classification based on ECN only
Quality of Service (QoS)
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