Every now and then I come across some really basic information which we all know but, when we need it, never can remember exactly. Here is some useful information comparing the bandwidth capacity (speed) of various common telecom and network facilities:

Dial-up
An analog modem using twisted pair copper phone lines.

 Bell 103             300    bit/s
 Bell 212            1200    bit/sec
 v.22bis             2400    bit/sec
 v.32                   9.6  Kbit/sec
 v.32bis               14.4  Kbit/s
 v.34                  33.6  Kbit/s
 v.90                  53.3  Kbit/s
   v.90 up*            33.6  Kbit/sec
 v.92                  53.3  Kbit/sec
   v.92 up*            48.0  Kbit/sec
 56k                   53.3  Kbit/s
 ISDN                 128.0  Kbit/s

Cable
Uses coaxial copper cable.

 Average                2.00 Mbit/s
   Maximum             10.00 Mbit/s
   Upstream avg*      500.0  Kbit/s

DSL
Digital Subscriber Line uses twisted pair copper phone lines.

 IDSL                 128.0  Kbit/s
 UADSL                  1.5  Mbit/s
   UADSL up*          512.0  Kbit/s
 HDSL                   1.50 Mbit/s
 SDSL                   2.00 Mbit/s
 RADSL                  7.00 Mbit/s
   RADSL up*            1.00 Mbit/s
 ADSL                   8.00 Mbit/s
   ADSL up*             1.00 Mbit/s
 VDSL                  51.64 Mbit/s
   VDSL up*            19.20 Mbit/s

T-carrier
Usually delivered by fiber optic or microwave, although T1 may use two twisted pair copper phone lines.

 T-1                    1.54 Mbit/s
 T-3                   44.74 Mbit/s

Optical Carrier
Fiber optic point-to-point, often used for "backbone" facility.

 OC-3                 155.52 Mbit/s
 OC-12                622.08 Mbit/s
 OC-48              2,488.32 Mbit/s
 OC-96              4,976.64 Mbit/s
 OC-192             9,953.28 Mbit/s
 OC-255            13,219.20 Mbit/s

Ethernet
Used for local area networks (LANs) over multiple twisted pair copper cable, except for the obsolete 10base2 which uses coaxial cable.

10base2 2.00 Mbit/s
10baseT 10.00 Mbit/s
100baseT 100.00 Mbit/s
Gigabit Ethernet 1,000.00 Mbit/s


Wireless
May be fixed or mobile.

 HomeRF                 1.20 Mbit/s

 WiFi
   802.11a             54.00 Mbit/s
   802.11b             11.00 Mbit/s
   802.11g             54.00 Mbit/s
   802.11n            100.00 Mbit/s

 CSD                    9.6  Kbit/s
 CDMA                  14.4  Kbit/s
 iDEN                  19.2  Kbit/s
 CDPD                  19.2  Kbit/s
 1XRTT                144.0  Kbit/s
 HSCSD                 56.0  Kbit/s
 CDMA 2.5G             64.0  Kbit/s
 GPRS                 171.2  Kbit/s
 EDGE                 384.0  Kbit/s
 3G                   384.0  Kbit/s
 UMTS                   2.00 Mbit/s
 3G1xEV-DO              2.40 Mbit/s
 3G1xEV-DV              5.00 Mbit/s

*Note: Some connections are asymmetrical, they download faster than they upload.


An explanation of Bits(b), Bytes(B), and Baud
Bits and bytes are a measurement of electronic information. A byte is always 8 bits. Communications speeds are usually measured in bits per second while many computer operations are measured in bytes per second. A "56k" modem is 56 kilobits and a "2m" DSL connection is 2 megabits per second. "128MB" of RAM is 128 megabytes. Ideally when abbreviations are used, b means bits and B means bytes. Baud rate is another measure of transmission speed and is the number of actual signals sent per second. At one time it was equal to the bits per second, but modern technology allows us to send more than one bit per electric signal.


Mega and kilo
Communications device specifications are usually given in Kilo, meaning 1,000, and mega, meaning 1,000,000. Examples include modems and Ethernet.

Computer storage, such as hard drives, memory and file size, are ususally measured in Kilo, meaning 1,024, and mega, meaning 1,048,576.

Traditionally kilo means one thousand exactly. In the communications world engineers call a thousand bits transmitted in a second 1 kilobit per second. While 1000 is a nice round number for humans to work with, it isn't for computers. Mathematically speaking, humans use decimal or base 10 numbers and computers use binary or base 2 numbers. 1024 is 2 to the power of 10 which is a significant binary value and so is represented by kilo in the computer world. Mega is similar except it means 1,000,000 when describing a communications device and means 1,048,576 (i.e., 1024 kilo) when describing computer devices. Ideally when abbreviations are used, k means 1000 and K means 1024, but this notation convention is not always observed.


Based on information provided by various sources
including Bandwidth Place (http://www.bandwidthplace.com)