If I understand correclty, WFQ considered DiffServ, right?
My understanding is that WFW does not rely on predefined classes. Instead it relies on ToS field in the IP header.
Am I right that applications will have that ToS value already defined? From there I just enable #fair-queue and the ToS is already defined and therefore I do not need to configure anything else.
Most applications do not set TOS values, and best practice is to overwrite any TOS values, except from explicitly trusted sources like IP phones or IP telephony servers. You do not want a clever programmer dictating the QOS service levels in your network.
WFQ does not depend on TOS values to function correctly (though the TOS value will influence it). You can have all TOS bytes set to 0X00 and WFQ will still protect small interactive flows against starvation from big transfers like FTPs.
WFQ is the default queuing method for serial links because it works well in a data only network. If you have real time traffic like voice or video, or other requirements to provide special treatment to a particular class of traffic you will need to look at CBWFQ.
You are correct in that all you need to do to use WFQ is to enable fair-queue on the serial interfaces.
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