Compute token-bucket shaper parameters — committed burst, excess burst and interval — from CIR and Tc.
A shaper is a bucket refilled with Bc bits every Tc milliseconds; traffic is metered out at line rate until the bucket empties, then waits for the next interval. Small Tc values give smoother output and lower jitter, at the cost of more scheduler work. Tc chosen too large produces bursts long enough to overflow carrier buffers and drop voice, while Tc too small wastes CPU and can under-run the committed rate.
Traffic Shaping
Bc = CIR × Tc, so Tc = Bc ÷ CIR; the shaper releases Bc bits every Tc and 1000 ÷ Tc intervals fit in a second.
Bc = CIR × Tc, so Tc = Bc ÷ CIR; the shaper releases Bc bits every Tc and 1000 ÷ Tc intervals fit in a second. A shaper is a bucket refilled with Bc bits every Tc milliseconds; traffic is metered out at line rate until the bucket empties, then waits for the next interval. Small Tc values give smoother output and lower jitter, at the cost of more scheduler work.
Tc chosen too large produces bursts long enough to overflow carrier buffers and drop voice, while Tc too small wastes CPU and can under-run the committed rate.
This calculator takes 4 inputs: Committed information rate (CIR), Shaping interval Tc, Excess burst as share of Bc, Physical line rate. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.