This is the configured transmit speed for this VDSL modem, and per the MIB, the corresponding modem at the other end of the line must have an equal cvdslLineConfRxSpeed value for the connection to be consistent - the two ends' complementary speed settings have to agree. It's the object to check when a line trains but runs at an unexpectedly asymmetric or lower rate than expected, since a mismatch between this transmit setting and the peer's configured receive setting can prevent full-rate operation. If this is configured for 30 Mbps but the CPE's corresponding receive-speed setting was only provisioned for 15 Mbps, the line will negotiate down rather than reaching its intended full transmit rate.