>From: Moose <olymoose@xxxxxxxxxxxxx>
>
>I don't think your dial-up speed numbers 'add up'...
>Are you perhaps off by about 10x? Am I missing something?
I think you're missing something; you're off by 10x.
A 56kb (note lower case "b") can pass a maximum of 56,000 BITS per second,
using an asynchronous protocol that requires two bits of overhead per byte
(start/stop bits). Such modems can employ compression, but JPEG images are
already compressed, and so don't go appreciably faster with additional
compression.
That means you get a MAXIMUM of 5.6kB (note upper case "B") BYTES per second
throughput. Typical is more like 3kB.
Given the same speed, cable and DSL are synchronous protocols, and thus have an
automatic 20% advantage, due to the lack of start/stop bits.
>At 30kbps, a 100k image should take about 3-4 sec. to download...
That would be 3kB/s, and a 100kB image will take 34.7 seconds.
I'd be VERY surprised if you are actually getting 25kB throughput over your
56kb modem line. 5.6kB is the theoretical maximum. I get 19kB tops over a
commercial-grade 160kb synchronous IDSL line.
--
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