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It should also be noted that there is latency related to physical
transmission speeds, so if the upload or download does checksums and
verify handshaking, then there will be a delay of the roundtrip at the
speed of light.  Now this seems very fast to most folks, but
electronically it is measurable, and on lines of several miles in
length, it amounts to microseconds per block.  If the block size is say
4K, and you download 4M, that is 1000 blocks.  If the delay is 1usec,
the total delay added is 1ms, or nearly 5000 bytes decrease at 5Mhz.
Also there is additional overhead on normal transmissions that may not
be in place on the speed test, and the speed test probably relates the
bits/sec, which is not the same as the number of usable bytes, since the
TCP uses quite a few bytes per block to specify various things about the
transfer.  All of this slows the response for actual file transfer, in
addition to loading of the sending computer.

	On the speed tests, check both local responders and remote.  I am in
California, I regularly use Irvine and a system in New York.  there is
quite a difference.

Regards,
Les H

On Fri, 2009-08-14 at 23:41 +0800, Ed Greshko wrote:
> Daniel B. Thurman wrote:
> >
> > I have been testing my residential ISP/DSL-Landline
> > connections and wanted to make sure that I was getting
> > what I am paying for. Supposedly, one can use the various
> > website based "speed test" tools to determine their upload
> > and download speeds.
> >
> > Are these "speed test" tools credible and can they
> > be trusted?
> >
> > Of the several sites I have tried, they all more or less
> > seemed to be in close agreement with one another in
> > terms of the bandwidth speeds, i.e. my connection
> > speed is quoted at 768KB/s up and 3MB/s down,
> > and the farther away from central, the more reduced
> > is the speeds are.
> >
> > The average speed tools says that I have measured
> > speeds of 720-30 KB/s up and 2.0-5MB/s down.
> >
> > Why is it however, that when downloading software
> > from the various Linux/M$ and other downloads sites
> > I am seeing on average, speeds of 200-320(max) KB/s
> > and never see anything much faster than that?
> >
> > Is this normal?
> Yes, very normal....
> 
> First, the download speed get from any site can only be as high as their
> upload speed.
> 
> Second, run the web based speed checks from 2 or 3 different sites 
> simultaneously and/or the same site multiple times simultaneously and
> see what the results are then. 
> 
> Those two things should shed some light as to why it is normal.
> 
> Oh, and third, the software download sites probably also have rate
> limits on each upload (from their point of view) so that everyone gets
> the same level of service.
> 
> All of these reasons are the driving force behind the development of
> bittorrent...
> >
> > Has anyone gotten download speeds any faster that
> > what I have reported?
> >
> > What I am trying to determine is if my ISP only shows
> > un-throttled speeds between me & them, but then somehow
> > throttles my bandwidth usage when I am using the Internet,
> > or is it more probable that download speeds are being throttled
> > from the download site itself?
> >
> > Other than by using `speed testers', I have yet to find a download
> > site that pushes out more than 2-300KB/s?
> >
> > I have tried HTTP, FTP & Bittorent and there is very little or no
> > speed improvements as far as I can tell.
> >
> > Just wondering,
> > Dan
> >
> 
> 
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