I’ve set up an ftp server. My ISP is giving me an ADSL connection with an
speed they say is 768k for uploads and 8meg down. And yet I’m seeing my uploads are
around 85k and 90k.
I need faster uploads. Can I change something about my system to make that
There’s one big potential point of confusion here, so let’s take this
opportunity to review upload and download speeds, what they really mean, and
what you can do to maximize them.
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The person asking the question had also gone to some of the on-line speed
testing sites, such as that at Broadband
Reports. The numbers being show there more-or-less matched the figures that
his ISP was providing.
That’s actually good news. And, to be honest, I’m quite jealous. 768k up /
8meg down looks wonderful to me – because of telephone company limitations (and
no cable in my area) I’m limited to 128k up and 768k down. Once upon a time
that was blazingly fast. Now, not so much. Did I mention I’m jealous?
But just what do those numbers mean?
First, realize that they’re measurements in bits per second
or bps. That means on my DSL connection, I can upload at a maximum
speed of 128k, or 131,072 (128 x 1,024) bps. Similarly, I can download at a
maximum of 785,432 (768 x 1,024) bps. My faster questioner can upload at
785,432 bps and download at a whopping 8,388,608 (8 x 1,024 x 1,024) bps.
But we measure downloads and file sizes in bytes not bits. So a
more meaningful number might be the download speed in Bytes per second (Bps –
notice that the “B” is capitalized? Subtle.) With 8 bits to a byte, a speed of
768k bits per second works out to … 98,304 Bytes per
second, or 96KBps.
So when you say that you’re seeing uploads at around “85k and 90k” it leads
me to wonder if you’re measuring your uploads in Bytes per second, and
comparing to the line speed expressed in bits per second. If that’s
the case, then the numbers you’re seeing are quite reasonable.
Why aren’t they actually at the 96KBps I calculated your line speed to be in
Bytes per second?
In a word: overhead. If you’re measuring based on file size, then the
communications protocols involved in transferring that file break it up into
“chunks”, adding a little bit of overhead data to each chunk to create a packet
that can then be properly reassembled into the original file. There are also
overhead delays involved in most communications protocols – the time it takes
to start sending each packet and the time it takes to verify and acknowledge
back that the packet was properly received.
internet is most likely your real bottleneck.”
Because of that overhead, I typically just divide by 10 for a rough estimate
of actual, effective transfer rate. My 768kbps DSL roughly downloads
at around 76KBps, or 76k Bytes per second. Very roughly. But it’s slightly
easier math, then, to see about how long my next download will take.
And of course other network traffic can affect the effective speed as well.
If you’re downloading your email while you’re uploading a file on the same
internet connection, both operations will slow down some. If you’re on cable,
you’re actually sharing your bandwidth with your neighbors – so if they’re doing something
internet-intensive, that could also impact your speeds.
The bottom line here is that your connection to the internet is most likely
your real bottleneck. Barring other software on your machine that’s ‘clogging
the line’ trying to do something on the internet at the same time you are,
you’re at the mercy of the capacity of that line, and what your ISP can provide