OC = Optical Carrier DS = Digital Service, level 0-3; DS3 ~= T3 ~= OC3 DS0 = 64 Kbps DS1 = 1.554 Kbps OC-1 = 51.85 Mbps OC-3 = 155.52 Mbps OC-12 = 622.08 Mbps OC-24 = 1.244 Gbps OC-48 = 2.488 Gbps