QoS color aware and color blindness?

Question

QoS - Color Aware and Color Blind mode.

1. Is color - red, yellow and green is a kind of analogy for violate, exceed and conform traffic rate. If so, whey did they come for the colors here.

I mean there is no where in the packet or frames the color bits are stored. I think it is internal to the system. Am I correct? If not then where is it stored in the frame?

2. What's the use of pre-color then ?

3. What is color blind? Is it like either conform or violate? That is there is no such yellow.

Dual Rate - 3 color meter talks about -

2 buckets that's why two rate - one for CIR and another for PIR.

next 3 colors are conform - green, exceed - yellow and violate - red.

Why they have used colors here - just conform is enough and why it needs to be called with color green also. why exceed terminology is enough and why it needs to be called with yellow color? Why violate terminology is enough and why it needs to be called with red color?

Please explain, I am finding these colors and color blind things quite confusing.

Answer 1

Colors are just an analogy for humans.

QoS is realized with different traffic queues in a device and packets/frames are mapped to these queues by your QoS rules.

E.g. you have a high, a standard, and a low priority queue. You map VoIP to high, ICMP to low and keep the rest standard. You set the queue scheduling to 3:1, so in case of congestion 3 high packets are forwarded, but only 1 standard packet (or 3 standard packets for 1 low packet). Packets exceeding its queue capacity are dropped.

Additionally, you can police traffic using QoS rate limiting. E.g. you limit YouTube traffic to 1 Mbit/s per user or 10 Mbit/s for the whole network (if your device supports this kind of control). Excess rate traffic is dropped.