Bandwith definition

Ok guys if you can tell me this I'll be impressed.  In computing Bandwith referes to how much data can be moved.  High Bandwith connections allow for faster data transfer.  In electronics it refers to how many frequincies can pass through a filter.  It's computed by subtracting the lower freq. form the higher freq that can pass through the filter.  How is it calculated in computer networking or is it just used as slang and has no real hard meaning or definition.

[Keefe]

In computing, bandwidth is the amount of data that can be transmitted in a fixed amount of time.  Hence, 45 bps would be 45 bits per second.

[Uranium-235]

do I get this right? the more bandwidth, the more data that can be transferred to more computers. So like I can get 1MBPS on my dsl line, but it goes down to a little above half if two people are using it at the same time. With more bandwidth, the transfer rate wouldent go down at much per machine?

[wizbones]

The term bandwidth refers to how much data can be moved at one time from a web server out onto a network and across the Internet. You can think of bandwidth as the diameter of a water pipe. The bigger the diameter of the pipe, the more water you can move, even if the water is moving at the same speed.

POTS (Plain Old Telephone Service) = 64000 BPS (Bytes per second)
ISDN (2 POTS) = 128000 BPS
T1 = (12 ISDNS) = 1,544,000 BPS
Ethernet = (~ 6.5 T1s = 10,000,000 BPS
T3 (28 T1s) = 43,232,000 BPS
FAST ETHERNET (~ 65 T1s) = 100,000,000 BPS
OC3 (3.6 times T3) = 155,000,000 BPS
OC12 (4 times OC3) = 622,000,000 BPS
OC48 ((Internet2) 4 times OC12) = 2,075,136,000 2.4 Gbs/second
OC192 (4 times OC4 = 9.6 Gbs/second

Data transfer (AKA bandwidth usage) refers to how much data/information is sent to or received over a specified period of time. Use the following to determine your monthly data transer:

[Average size of your web page(s) + any graphics included within] * [number of visitors you expect each day * number of pages each visitor will view] * [30 days in a month] = Total Monthly Data Transfer Usage.

If you really want the formula for figuring out the bandwidth of the diferent media, let me know, I'll dig through my books from when I worked for the Telco, but off the top of my head I just cant seem to remember and at the moment cannot find my book LOL

[quote author=wizbones link=board=hardware&num=1010936564&start=0#3 date=01/14/02 at 12:49:55]
The term bandwidth refers to how much data can be moved at one time from a web server out onto a network and across the Internet. You can think of bandwidth as the diameter of a water pipe. The bigger the diameter of the pipe, the more water you can move, even if the water is moving at the same speed.

POTS (Plain Old Telephone Service) = 64000 BPS (Bytes per second)
ISDN (2 POTS) = 128000 BPS
T1 = (12 ISDNS) = 1,544,000 BPS
Ethernet = (~ 6.5 T1s = 10,000,000 BPS
T3 (28 T1s) = 43,232,000 BPS
FAST ETHERNET (~ 65 T1s) = 100,000,000 BPS
OC3 (3.6 times T3) = 155,000,000 BPS
OC12 (4 times OC3) = 622,000,000 BPS
OC48 ((Internet2) 4 times OC12) = 2,075,136,000 2.4 Gbs/second
OC192 (4 times OC4 = 9.6 Gbs/second

Data transfer (AKA bandwidth usage) refers to how much data/information is sent to or received over a specified period of time. Use the following to determine your monthly data transer:

[Average size of your web page(s) + any graphics included within] * [number of visitors you expect each day * number of pages each visitor will view] * [30 days in a month] = Total Monthly Data Transfer Usage.

If you really want the formula for figuring out the bandwidth of the diferent media, let me know, I'll dig through my books from when I worked for the Telco, but off the top of my head I just cant seem to remember and at the moment cannot find my book LOL
[/quote]

I think it's bits per second ( baud rate ). To get to bytes, divide by 8, so a 64K is actually only 8 K bytes.

[wizbones]

My bag guys n gals,

It's actually bits not bytes. I hate it when that happens. Here's a better idea of bits n bauds explained:

Baud rate
Baud rate is a measure of the number of times per second a signal in a communications channel varies, or makes a transition between states (states being frequencies, voltage levels, or phase angles). One baud is one such change. Thus, a 300-baud modem's signal changes state 300 times each second, while a 600- baud modem's signal changes state 600 times per second. This does not necessarily mean that a 300-baud and a 600-baud modem transmit 300 and 600 bits per second, as you'll learn in a few lines.

Determining bits per second
Depending on the modulation technique used, a modem can transmit one bit--or more or less than one bit--with each baud, or change in state. Or, to put it another way, one change of state can transmit one bit--or more or less than one bit.

The number of bits a modem transmits per second is directly related to the number of bauds that occur each second, but the numbers are not necessarily the same.

To illustrate this, first consider a modem with a baud rate of 300, using a transmission technique called FSK (Frequency Shift Keying, in which four different frequencies are turned on and off to represent digital 0 and 1 signals from both modems). When FSK is used, each baud (which is, a gain, a change in state) transmits one bit; only one change in state is required to send a bit. Thus, the modem's bps rate is also 300:


    300 bauds per second X 1 bit per baud  =  300 bps

Similarly, if a modem operating at 1200 baud were to use one change in state to send each bit, that modem's bps rate would be 1200. (There are no 1200 baud modems, by the way; remember that. This is only a demonstrative and hypothetical example.)

Now, consider a hypothetical 300-baud modem using a modulation technique that requires two changes in state to send one bit, which can also be viewed as 1/2 bit per baud. Such a modem's bps rate would be 150 bps:


    300 bauds per second X 1/2 baud per bit  =  150 bps

To look at it another way, bits per second can also be obtained by dividing the modem's baud rate by the number of changes in state, or bauds, required to send one bit:


       300 baud
    ---------------  =  150 bps
    2 bauds per bit


Now for some reality,

First, lest you be misled into thinking that "any 1200 baud modem" should be able to operate at 2400 bps with a two-bits-per- baud modulation technique, remember that I said there are no 1200 baud modems. Medium- and high-speed modems use baud rates that are lower than their bps rates. Along with this, however, they use multiple-state modulation to send more than one bit per baud.

For example, 1200 bps modems that conform to the Bell 212A standard (which includes most 1200 bps modems used in the U.S.) operate at 300 baud and use a modulation technique called phase modulation that transmits four bits per baud. Such modems are capable of 1200 bps operation, but not 2400 bps because they are not 1200 baud modems; they use a baud rate of 300. So:


    300 baud X 4 bits per baud  =  1200 bps


or


         300 baud
    ------------------  =  1200 bps
     1/4 baud per bit


Similarly, 2400 bps modems that conform to the CCITT V.22 recommendation (virtually all of them) actually use a baud rate of 600 when they operate at 2400 bps. However, they also use a modulation technique that transmits four bits per baud:


    600 baud X 4 bits per baud  =  2400 bps


or


         600 baud
    ------------------  = 2400 bps
     1/4 baud per bit


Thus, a 1200-bps modem is not a 1200-baud modem, nor is a 2400-bps modem a 2400-baud modem.

Now let's take a look at 9600-bps modems. Most of these operate at 2400 baud, but (again) use a modulation technique that yields four bits per baud. Thus:


    2400 baud X 4 bits per baud  =  9600 bps


or


         2400 baud
    ------------------  =  9600 bps
     1/4 baud per bit

Allot more than anyone wanted to know I'm sure, but hey what can I say? Nothing right?  ;D

Yes,

Also a T1 line = 24 each 64 kbs digital channel slots when used as  certain types of intertrunking or terminating a digital channel bank. This is the US standard, will be 32 channel slots by European standards. The T1 line is 1.544mbs no matter how it is used.
But when a T1 line is used as Digital Concentrator trunking lines, such as the ADPCM ( Adaptive Differential Pulse Code Modulation Concentrators ) a channel slot measurement becomes insignificant.
Also I believe the ISDN contains two (2) each 64 kbs circuits and one  (1) 8 kb data circuit.

[wizbones]

Correct-a-mondo on the ISDN line