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QoS using WRED drop preferences in DSCP Assured Forwarding

qos
Advisor

QoS using WRED drop preferences in DSCP Assured Forwarding

I want to use QoS DSCP Assured Forwarding in my network based on a QoS policy that will match packets based on an ACL, remark the DSCP value and assign to a queue. The default queue is WRR, and although for example DSCP AF31 maps to dot1p-3, which maps to a local precedence of 3 and therefore schedules the packet to WRR queue 3, I have to manually remark the packet to local precedence 3 else it won't be scheduled in output queue 3.


However, as the Assured Forwarding model contains drop preferences within each class, so that AF11 has a lower drop preference than AF13, the priority is not recognised because both are put in queue 1. I would like to use WRED, which is a congestion avoidance mechanism that utilizes drop preferences.


When I create a WRED table globally, the table type is "queue" based and the default table does not distinguish amongst the queues and drops preferences, they are all the same so I have to configure them.


Does this mean that, when the WRED table is configured, if I remark a packet as AF11 and remark local precedence as 3, then do the same for a packet AF13,and then use WRED, that AF13 packets will be dropped before AF11 packets? Therefore WRED is DSCP based in that it inherently recognises that AF13 needs to be dropped before AF11?

 

I am using HP5800 R12110P