An index that indicates which level of a multi-rate shaper is
being given its parameters. A multi-rate shaper has some number
of rate levels. Frame Relay's dual rate specification refers to a
'committed' and an 'excess' rate; ATM's dual rate specification
refers to a 'mean' and a 'peak' rate. This table is generalized
to support an arbitrary number of rates. The committed or mean
rate is level 1, the peak rate (if any) is the highest level rate
configured, and if there are other rates they are distributed in
monotonically increasing order between them.