That's a great question.
The requirements stated "shape average of 512Kbps, Tc 10ms, BECN adaptive down to 256Kbs. Then the MQC requirements of 64Kbps and 192Kbps.
With the figures in the solution guide we never send above 256Kbps as the Bc is 25600 and Be is 0. This also breaks the Tc interval requirement of 10ms.
Shouldn't the solution be:
map-class frame-relay FRTS_TO_R5
frame-relay cir 512000
frame-relay bc 2560
frame-relay be 2560
frame-relay mincir 256000
frame-relay adaptive-shaping BECN
(then nest your policy-map)
The logic being that "Bc" should not be above minCIR, and"Be" brings us to the CIR rate of 512Kbps. When you received BECN's you back off to "Bc" to get minCIR.
Or am I looking at this all wrong?