Catalyzes the initial step of dolichol-linked oligosaccharide biosynthesis in N-linked protein glycosylation pathway: transfers GlcNAc-1-P from UDP-GlcNAc onto the carrier lipid dolichyl phosphate (P-dolichol), yielding GlcNAc-P-P-dolichol. a dolichyl phosphate + UDP-N-acetyl-alpha-D-glucosamine = N-acetyl-alpha-D-glucosaminyl-diphosphodolichol + UMP Protein modification; protein glycosylation. Belongs to the glycosyltransferase 4 family.