CB Shaping to a Peak Rate
The shape average command has been used in all the examples so far. However, the command
shape peak mean-rate is also allowed, which implements slightly different behavior as compared
with shape average for the same configured rate. The key actions of the shape peak mean-rate
command are summarized as follows:
■ It calculates (or defaults) Bc, Be, and Tc the same way as the shape average command.
■ It refills Bc + Be tokens (instead of just Bc tokens) into the token bucket for each time
interval.
This logic means that CB Shaping gets the right to send the committed burst, and the excess burst,
every time period. As a result, the actual shaping rate is as follows:
Shaping_rate = configured_rate (1 + Be/Bc)
For instance, the shape peak 64000 command, with Bc and Be defaulted to 8000 bits each, results
in an actual shaping rate of 128 kbps, based on the following formula:
64 (1 + 8000/8000) = 128