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Originally Posted by mmm
Hard disk manufacturers and comms companies usually use whatever definition of k and M that gives them the bigger number, but when you format your harddisk the available space is much smaller!
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Well no, comms companies use the IETC / IEEE definitions of bits which dictate that baseband comms bitrates are expressed decimally, not binary. Check the specifications for 10baseT, fast and gigabit ethernet for more on this, along with specifications for SDH, POS and the defined bitrates for STM and OC circuits (IE an E1 circuit is 2048000 bps, 2.048Mbps).
If we're getting *really* pedantic kilobytes, megabytes, gigabytes indicate decimal quantities, not their binary equivalents kibibytes, mibibytes and gibibytes. Sorry if I've upset any programmers with that one but that's the way it is, officially apparently - see IETC:
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kibi- (Ki-)
a binary prefix meaning 210 = 1024. This prefix, adopted by the International Electrotechnical Commission in 1998, was supposed to replace kilo- for binary applications in computer science. Thus 1024 bytes of storage is officially a kibibyte, not a kilobyte. However, computer professionals generally dislike this unit (they say it sounds like a cat food) so the ambiguity in the size of a kilobyte persists. The prefix is a contraction of "kilobinary." The symbol Ki-, rather than ki-, was chosen for uniformity with the other binary prefixes (Mi-, Gi-, etc.).
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It's not really possible to give an exact figure for overheads as they vary depending on the protocol being used for transfer, MRU, if PPP is involved at any point, multiple sources for the same download. Only thing you can say is that with a packet size x the overhead will be y%.
I was just giving the pure unfettered bitrates, the performance I would recommend users to expect from their new services is as I posted, 120KiB/s for each 1Mbit of download speed, 12KiB/s for each 100k of upload speed. Anything else is a bonus!
The joys of comparing transmission/communication rates with storage rates, telecomms vs IT at its' finest.