This attribute specifies the default cell delay variation tolerance
(CDVT) for all connections of the nrt-VBR service category. An
override to this default may be specified for a provisioned
connection under the Vcd Tm or Vpd Tm component.
If Usage Parameter Control (UPC) is enabled for a connection,
CDVT is used by the UPC function to decide whether a cell is
conforming or non-conforming based on the connection's traffic
descriptor type. The larger the CDVT value, the more tolerant is the
UPC of bandwidth usage beyond the traffic contract.