Involved in protein N-glycosylation. Essential for the second step of the dolichol-linked oligosaccharide pathway (By similarity). N-acetyl-alpha-D-glucosaminyl-diphosphodolichol + UDP-N-acetyl-alpha-D-glucosamine = H(+) + N,N'-diacetylchitobiosyl diphosphodolichol + UDP Heterodimer with alg14 to form a functional enzyme. Belongs to the glycosyltransferase 28 family.