This is the windowSize corresponding to the given packet size and
throughput class. All Vcs using the windowSize matrix support
large Vc windows on both ends of the Vc, and support the signalling
of the chosen Vc window size from the destination (called) end to
the source (calling) end. This is the only matrix supported.
The windowSize should be configured in the same way network
wide, though it can be upgraded on a module by module basis. Vcs
using the windowSize matrix will run properly if the matrices on
different nodes differ since the Vc window is selected by the
destination (called) side of the Vc.