>There is talk of providing 1, 2-8 Mb broadband. Some providers talk about, say, 512 Kbps.
>
>This made me think: just what IS 2 Mb broadband? OK the bandwidth but there's no time element in there. For instance, what DOES 2 Mb work out at as Kbps?
>
>Anyone?

Digital bandwidth is measured in bps (bits per second - not bytes!), kbps, Mbps, etc. Unlike the usage of "kilo" for data storage (= 1024; this is standard, except amongst vendors of hard disks...), in transmission speeds, "kilo" means exactly a 1000.

"2 Mb" is probably just short for "2 Mbps"

So, the calculations for the (theoretical) download speed of a 2 MB file are as follows:

2 MB = 2 * 1024 * 1024 = 2097152 bytes = 16777216 bits.

16777216 bits / 2 million bps = 8.388608 seconds; slightly over 8 seconds.

All this is very theoretical; several factors can make the download slower:

1) Even under ideal conditions, there is always some overhead in transmitting individual data packets (source and destination address for each packet, and some other header data, for a start). Under not-so-ideal conditions, overhead can be larger (lost packets have to be retransmitted).

2) The server on the other side may be quite busy.

3) TCP, in its current implementation, doesn't always take maximum advantage of available bandwidth.