Hello Jose
There’s no single answer to your question. You are correct in that the Bc that you will use will depend on the traffic that you want to shape. As mentioned in the lesson, Bc depends upon the Tc and upon the actual Committed Information Rate or the required shaped speed of the link, like so:
Bc = Tc * CIR
And Tc will depend on the kind of traffic that will be shaped. If you’re shaping voice, Tc should be around 10 ms. So Bc = 10 ms * CIR. Now if your CIR is very large like 5Mbps, then Bc will be 50 kilobits, but if your CIR is relatively small like 128kbps, then Bc = 10 ms * 128kbps = 1280 bits (remember to convert your units when calculating these values).
If you’re going to make your Tc larger because you’re only forwarding non-time-sensitive traffic, then Bc changes accordingly based on the CIR as well.
So really, you have to calculate each situation and determine which value is best.
I hope this has been helpful!
Laz