[nsp] How to determine Bc for traffic-shaping

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Hello,

I have a question how to determine Bc value for frame-relay
traffic-shaping.

We can see interval timer by command as follows.

ROUTER-1>sh frame pvc 30
:
  cir 640000 bc 330000 be 144000 limit 23155 interval 65
: ^^
<<< part of configuration >>>
map-class frame-relay fast_vc
 frame-relay cir out 640000
 frame-relay bc out 330000
 frame-relay be out 144000

Cisco document describes this value is less than 125msec, and calculation
is,
interval(Tc) = Bc / CIR

But we encounter this is not correct when we use over 640Kbps cir value.
I expect internal calculation by watching tendency.
And result is as follows.

if( CIR <= 640000) {
  I = Bc / CIR;
  if (I > 125) {
    I = 125;
  }
} else {
  I = Bc / CIR;
  while (I > 80000 / CIR) {
   I = I / 2;
  }
}
Tc = I;

I wonder if we can determine Bc value by using this Tc and CIR.
Bc = Tc * CIR

Any opinion is appreciated.

Thanks.

-----
Kouji Baba

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