This attribute is a vector of three elements that specify the quality of
service parameters for the backward direction for this connection.
This attribute is used for SPVC connections.
The cdv element specifies the acceptable peak-to-peak Cell Delay
Variation (CDV) of real-time connections (CBR and rt-VBR).
It is signalled through the extended QoS information element.
The ctd specifies the acceptable maximum Cell Transfer Delay
(maxCtd) of real-time connections (CBR and rt-VBR). It is
signalled through the end to end transit delay information element.
The clr specifies the acceptable Cell Loss Ratio (CLR) of CBR, rt-
VBR, and nrt-VBR connections. It is signalled through the extended
QoS information element.