Dell UltraSharp 27 User Manual page 38

Connecting the DP cable
Connecting the monitor for DP Multi-Stream Transport (MST) function
NOTE: Supports the DP MST feature. To make use of this feature, your PC
Graphics Card must be certified to at least DP1.2 with MST option.
NOTE: Remove the rubber plug when using DP out connector.
38 | Setting up the monitor
DP (in)