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Basic clarification on QoS (CoS-to-DSCP) vs ToS

Hi there, can you help me clarify this:

Let's say I have a Cisco switch 2960, layer 2 switch.

Then if I need to classify and mark a certain application traffic which is connected to a Cisco 2960 switch, I would need to do cos-to-dscp maps.

The reason I need to do that is because at layer 2, we have a frames which do not have knowledge about ToS (IP precedence and DSCP) fields, correct?

The way I understand is that such cos-to-dscp mark is inserted in the application payload which is encapsulated into the IEEE 802.3 frame, correct?

When such frame is forwarded to a layer 3 device for example (which will then be a packet), it will then use the DSCP value to make decisions on how to prioritize and handle the traffic.

Is the understanding above correct?

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