does the network driver subsystem not have a system service interface

[rookie1010]

Hello

According to the following figure
http://www.windowsitlibrary.com/Content/280/01/files/fig6.html

the network driver subsystem in windows NT 4 does not have a system service interface. is there no system service interface or is the dockets emulator/NetBEUI emulator/other kernel-mode TDI clients the system service interface