The value of vRtrIgmpIfMcacPreRsvdMandBW specifies the bandwidth
pre-reserved for all the mandatory channels on a given interface
in kilo-bits per second(kbps).
If the value of vRtrIgmpIfMcacUnconstrainedBW is '0', no mandatory
channels are allowed. If the value of vRtrIgmpIfMcacUnconstrainedBW
is '-1', then all mandatory and optional channels are allowed.
If the value of vRtrIgmpIfMcacPreRsvdMandBW is equal to the value of
vRtrIgmpIfMcacUnconstrainedBW, then all the unconstrained bandwidth
on a given interface is allocated to mandatory channels configured
through multicast cac policy on that interface and no optional
groups (channels) are allowed.
The value of vRtrIgmpIfMcacPreRsvdMandBW should always be less than
or equal to that of vRtrIgmpIfMcacUnconstrainedBW. An attempt to set
the value of vRtrIgmpIfMcacPreRsvdMandBW greater than that of
vRtrIgmpIfMcacUnconstrainedBW will result in inconsistent value error.