Mailinglist Archive: opensuse-edu (225 mails)

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Re: [suse-linux-uk-schools] ADSL speeds into school
  • From: ian <ian.lynch2@xxxxxxxxxxxx>
  • Date: Sun, 11 May 2003 12:01:23 +0000 (UTC)
  • Message-id: <1052654529.2163.1626.camel@xxxxxxxxxxxxxxxxxxxxx>
On Sun, 2003-05-11 at 11:50, David Bowles wrote:
> Now there's one aspect of downloading that I don't understand. Where
> I'm living now is so far from my local exchange (over 7KM) there is no
> way I could get broadband even if BT made my exchange broadband ready.
> Consequently I'm still using a bog standard V90 modem connection.
> Here's my problem: Given that my connection to my ISP (Freeserve) runs
> at around 40Kbps, I'd expect this to be the main limiting factor when
> downloading files. As a consequence I'd expect the data-stream coming
> into my PC to approach 40Kbps at least part of the time (dead of night
> with both the UK and US fast asleep). In practice my download rates
> rarely get beyond half this figure. Most of the time it's far less
> than this than this no matter what sites I'm downloading from.
> Can someone explain why this is so? Where is the real-world choke
> point, given that other users with ASDL can achieve far higher speeds
> downloading from the same sites? Is there any way around this, apart
> from upgrading to ISDN which will no doubt suffer from the same
> problem.

The difference between a 64k ISDN channel and a 56k modem is that the
ISDN is 64k uncompressed whereas a modem achieves 56k by compressing the
data. If you download something that is already optimally compressed, eg
a Mpeg video, there is going to be no advantage in compressing the data
again - in fact it could slow things down by wasting time trying to do
the impossible! Try zipping an mpeg file and see how much smaller it
gets. You can also find servers that are heavily loaded being a limiting
factor too.

> Finally, is there any way of getting my own or some other ISP to
> temporarily cache the files while I am downloading them. This would
> eliminate the time overhead of constantly having to negotiate packet
> requests over long distance multi-jump Internet connections.

Doubt this would make any significant difference to your current limits.
ISDN will improve it but its expensive. The satellite system is probably
worth looking into.

> Thanks in advance,
> David Bowles
ian <ian.lynch2@xxxxxxxxxxxx>

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