On Wed, 15 May 2002, George Whiffen wrote:
> 1. My biggest concern is the slowest user i.e. at the end of a modem
> on the other side of the planet.  I thought they would almost certainly
> have modem compression so doing our own compression doesn't
> really help them at all i.e. actual download speeds stay the same, it's
> just we/they do the work rather than the modems.

The modem is only part of the route. All the people between you and the 
modem are paying for that bandwidth, and the costs are getting passed 
along somehow.

> 2. I was surprised when I got ISDN dial-up that it didn't seem
> to have automatic compression on the line, but assumed that was
> going to change.  Am I too hopeful?


> 3. But surely, ASDL, cable, the backbone and decent intranets
> must all do hardware compression, don't they?  Or are they
> secretly not very keen on decreasing network traffic?

None of the above routinely do compression on data. Imagine backbone
routers trying to compress data! The poor things run white-hot just trying
to deal with packet headers. If they actually had to look at the data and
do complicated transforms on it, that'd be the end of the internet.

> 4. Finally, if the network hardware isn't handling compression
> for us, I would have thought it was a good job for a web server.
> I guess I'd have to ask the Apache guys, but I would guess this
> can be really neatly done with some fancy mod_rewrite, custom
> extension or whatever.

There is a module for Apache that does gzip compression. It's called - 
wait for it - mod_gzip. We use it and it seems to work great. Cuts our 
bandwidth bills down.

I think the web server is a very reasonable place to do this compression. 
It divides the work so that it's in direct proportion to the volume of 
generated data. This is both fair and easy to manage.


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