Confusion over speed terminolgy (KBps, Mbps)

[redss]

I've run speed tests and am still confused over the way its calculated: There are 1024 bytes in a kilobyte right? so doesn't that mean that 1 KBps = 1024 Kbps? (captital B meaning bytes, small meaning bits)

Upon completion of using ftp to download a file, it tells me the file size in bytes, the number of seconds it took to download, and the calculated speed in KBps... but it seems to be using 1000 Kilobits per kilobyte, rather than 1024. Is the ftp server wrong?

example, using DOS ftp to retrieve file from angelfire.com: It says

ftp: 3579819 bytes received in 20.89Seconds 171.37Kbytes/sec.

So that's using 1000 Kilobits/kilobyte, but the calculation I get with WS-FTP is even farther off:

Received 3579819 bytes in 21.9 secs, (1.57 Mbps), transfer succeeded

I don't know how this was calculated, because I calculated 1.247 Mbps... the way I got that is:

3579819 bytes * 8 = 28638552 bits
 28638552 bits / 21.9 sec = 1307696 bits/sec
 1307696 / 1024 = 1277 Kbps
 1277 / 1024 = 1.247 MBPS

Does anybody know where my calculation is wrong?
thanks...

 

[InnoTech]

i'm not in the least bit trying to be an ass but as long as you're getting the speed that you are, is there a problem?

you are calculating correctly as far as i can see (8bits= 1 byte) and thats all that matters. however, 1KBps = 8kbps. if you were downloading at 1024kbps it would be 1Mbps.

when the speed test, tests it rounds up and down according to files size ect. so does your FTP cleint. they are NEVER going to be absolutely correct. "Jack of all trades. Master of none."

 

[redss]

Ok my question is: how do I calculate the Mbps from KBps... There is a discrepancy in the way the following 2 websites calculate Mbps:

Mcafee (see

http://promos.mcafee.com/speedometer/test_0600.asp)

uses 1024 megabits/kilobit
(they said my results were 600.005 KB in 4.326 sec which is 138.7 KB/sec which is 1136230 kbps
138.7 KB/sec * 8 bits/byte / 1024 = 1.084 Mbps, which is the calculation THEY use...

BUT bandwidthplace.com (see

http://bandwidthplace.com/speedtest/results.html)

uses 1000
(they said my results were 1,326,595.29 bps and 1.3 Megabits/sec, that is a factor of 1000, unlike mcAfee

So my point is, one of these websites are incorrect... which one is right? (You can check these sites yourself & see what I mean)
I need to be sure of this calculation because I plan to work in network consulting!

 

[InnoTech]

from everything i've leaned the bandwidthplace calculations look better. which would mean that mcaffe's 1136230 kbps would equal 1.14 Mbps. "Jack of all trades. Master of none."

 

[guestgulkan]

You have to take these tramsmission speeds with a pinch of salt.
Like someone said - in the computer world, the quantity
Kilo means 1024. A computer Mega is therefor 1024*1024.
[In the real world Kilo=1000 and Mega=1000000.]

But who wants to divide by 1024 or 1048576 = so most people
just divide by 1000 to get the transmission speeds.

Anyway on a serial link, you may have 8 data bits per byte, but there is the start bit, and a 1.5 stop bit =10.5 bits per byte.

On Ethernet there is all the header bits and checksum bits for both IP and TCP.

So take it all with a pinch of salt.

 

[redss]

Ah ha! I thought I should divide by 8 to derive the kBps from the kbps, but instead I should use 10.5! You said "serial link" so I assume you're talking about dialup? Does cable modem/ethernet also have the same number of start/stop bits?

 

[guestgulkan]

For serial interfaces I was talking about com1, com2 etc on the PC.
Cable modems use Ethernet.