Calculating Transfer Rate

[Neil]

I was attempting to see what kind of transfer rates we were getting over a
T1 line, so I transferred a large file using WS_FTP from one machine to
another. I took the MBytes transferred and multiplied by 8 and divided by
seconds to get Mbits per second. However, I noticed that my number was
different from the transfer rate that WS_FTP gave for the transfer. I
figured out that they took the MBytes and multiplied by 10, instead of 8, to
get Mbits.

Here's a sample transfer:

Bytes: 105,615,360
MBytes: 100.72
Transfer time: 401 seconds
My calculated transfer rates (using 8 bits/byte): 2.01 Mbits/sec
WS_FTP's declared transfer rate: 2.52 Mbits/sec

Any ideas as to why they use 10 bits/byte to calculate the transfer rate?

Thanks!

Neil

 

[daytripper]

I was attempting to see what kind of transfer rates we were getting over a
T1 line, so I transferred a large file using WS_FTP from one machine to
another. I took the MBytes transferred and multiplied by 8 and divided by
seconds to get Mbits per second. However, I noticed that my number was
different from the transfer rate that WS_FTP gave for the transfer. I
figured out that they took the MBytes and multiplied by 10, instead of 8, to
get Mbits.

Here's a sample transfer:

Bytes: 105,615,360
MBytes: 100.72
Transfer time: 401 seconds
My calculated transfer rates (using 8 bits/byte): 2.01 Mbits/sec
WS_FTP's declared transfer rate: 2.52 Mbits/sec

Any ideas as to why they use 10 bits/byte to calculate the transfer rate?

Yeah: they're providing the "uncooked" data rate (before the 8b/10b decoding)
instead of the "cooked" rate (after the 8b/10b decoding).

Either metric is perfectly legit, as long as it is used consistently when
comparing...

/daytripper

 

[Neil]

Here's a note from the WS_FTP knowledgebase:


Question/Problem: Why do the transfer rates in WS_FTP appear to be
calculated incorrectly?

Answer/Solution: The rates displayed by WS_FTP Pro are correct. In the
WS_FTP Pro classic interface, the transfer rate is displayed in either
kilobits per second (Kbps) or in kilobytes per second (KBps), depending on
the option selection on the Advanced tab of the Options dialog box. Note
that "start" and "stop" bits (overhead) are also included in the computation
(effectively 10 bits for each byte transferred).

In the Explorer interface, the transfer rate is always displayed in bytes
per second; you cannot change this. Again, "start" and "stop" bits
(overhead) are also included in the computation; this adds about 10 bits for
each byte transferred.

Neil