If wfRsvpSenderAdspecGSSvc is TRUE, this
is the service-specific override of the com-
posed Maximum Transmission Unit general charac-
terization parameter from the ADSPEC. A return
of zero or noSuchValue indicates one of the
following conditions:
the invalid bit was set
the parameter was not present
If wfRsvpSenderAdspecGSSvc is FALSE, this
returns zero or noSuchValue. UNITS, bytes