Free Resources: TeleGeography Research

Below are the standard metric prefixes used in the SI (Système International) conventions for scientific measurement. With units of time (e.g., gigabits per second) or things that come in powers of 10, they retain their usual meanings of multiplication by powers of 1,000 = 103. When used with bytes (e.g., gigabytes of data storage) or other things that naturally come in powers of 2, they usually denote multiplication by powers of 1,024 = 210.

Base 10

1 Kilobit/s	=	1,0001 = 103	=	1,000
1 Megabit/s	=	1,0002 = 106	=	1,000,000
1 Gigabit/s	=	1,0003 = 109	=	1,000,000,000
1 Terabit/s	=	1,0004 = 1012	=	1,000,000,000,000
1 Petabit/s	=	1,0005 = 1015	=	1,000,000,000,000,000
1 Exabit/s	=	1,0006 = 1018	=	1,000,000,000,000,000,000
1 Zettabit/s	=	1,0007 = 1021	=	1,000,000,000,000,000,000,000
1 Yottabit/s	=	1,0008 = 1024	=	1,000,000,000,000,000,000,000,000

Base 2

1 Kilobyte	=	1,0241 = 210	=	1,024
1 Megabyte	=	1,0242 = 220	=	1,048,576
1 Gigabyte	=	1,0243 = 230	=	1,073,741,824
1 Terabyte	=	1,0244 = 240	=	1,099,511,627,776
1 Petabyte	=	1,0245 = 250	=	1,125,899,906,842,624
1 Exabyte	=	1,0246 = 260	=	1,152,921,504,606,846,976
1 Zettabyte	=	1,0247 = 270	=	1,180,591,620,717,411,303,424
1 Yottabyte	=	1,0248 = 280	=	1,208,925,819,614,629,174,706,176

Measuring Telecommunications Bandwidth—DS-0 to OC-192

Carrier Technology	Data Rate (Mbps)	Description	64 Kbps Circuits*

DS-0	0.064	Base rate in the Digital Signal (DS) level hierarchy	1
T-1 (DS-1)	1.544	Primary level of the American T-carrier multiplexing system; capacity is the same as a DS-1 carrier	24
T-2 (DS-2)	6.312	Four times the capacity of T-1	96
T-3 (DS-3)	44.736	28 times the capacity of T-1	672
T-4 (DS-4)	274.176	168 times the capacity of T-1	4,032

E-1	2.048	Primary level of the European E-carrier multiplexing system	30
E-2	8.448	Carries four multiplexed E-1 signals	120
E-3	34.368	Carries four E-2 signals	480
E-4	139.264	Carries four E-3 signals	1,920
E-5	565.148	Carries four E-4 signals	7,680

OC-1/STS-1	51.840	Basic signaling rate of SONET hierarchy	672
OC-3/STM-1	155.520	Exactly three times the capacity of OC-1**	2,016
OC-12/STM-4	622.080	12 times the capacity of OC-1	8,064
OC-24	1,244.160	24 times the capacity of OC-1	16,128
OC-48/STM-16	2,488.320	48 times the capacity of OC-1	32,256
OC-192/STM-64	9,953.280	192 times the capacity of OC-1	129,024

“T” T-carrier system in U.S., Canada, and Japan with 1.544 Mbps as the primary level (24 voice channels x 64 Kbps per channel).

“DS” Digital Signal that travels on the T-carrier or E-carrier.

“E” Used in countries other than U.S., Canada, and Japan. The hierarchy was established by the CEPT (Conférence Européenne des Postes et Télécommunications) with 2.048 Mbps as the primary level ([30 voice channels + 2 channels for overhead] x 64 Kbps per channel).

“OC” Optical Carrier interface designed to work with STS-n (Synchronous Transport Signal) signaling rate in a SONET (Synchronous Optical Network).

“STM” Synchronous Transport Module refers to a large carrier (base signal 155.52 Mbps) in a SONET.

“STS” Synchronous Transport Signal is the electrical counterpart to the Optical Carrier (OC).

Notes:

* The number of 64 Kbps is presented for comparative purposes only. The actual number of simultaneous conversations possible over a given carrier may vary depending on the encoding scheme used.

** In the "E" and "T" hierarchies, each higher level is set to be "almost but not exactly" a multiple of the bit rate for the previous order (plesiochronous).

To eliminate problems associated with plesiochronous multiplexing, SONET, a synchronous hierarchy, was defined in the United States in 1986. As a result, the "OC" and "STM" carriers are exact bit-rate multiples of their primary levels, OC-1 and STM-1, respectively.

Source: TeleGeography research, Alcatel, Newton's Telecommunications Dictionary