This attribute specifies the number of multicast branches that can be
enabled on this FP.
A multicast branch is used for cell replication on a VCC connection
whose Vcc distributionType is pointToMultipoint. A branch
represents one ATM destination for the replicated cells.
Increasing the value of this attribute reduces the memory
available for the cell and frame memorys.
This attribute is ignored for the 1pOC48SmSrAtm card as it does
not support multicast connections.
For CQC based ATM FPs, the maximum value for this attribute is
10752.