Here is an interesting formula for calculating the data transfer rate vs connection speed of a modem.

  • ([kbps](1000/1024)(1460/1518)) / 8 = [KB/s]

In kilobits, the prefix kilo- refers to 1000, hence the first multiplier.   The 1024 refers to a KiloByte (1KB).   1460 represents the maximum amount of real data that a packet can contain, and 1518 represents the actual size of the packet with overheads for TCP, IP and MAC included.   The final 8 is there because there are 8 bits in a byte.

For example, to work out the maximum transfer rate for a 512kbps line, the formula would look as follows:

  • (512(1000/1024)(1460/1518)) / 8 = 60KB/s (rounded off)

I hope this helps you as it helped me!

Parts of this article © Robin Walker, reproduced with permission.    The original article can be found here.

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