[techtalk] HELP! Webserver compromised?!?

[jenn at simegen.com]

Michelle Murrain wrote:

 
> I know about mod_proxy, and the general idea of proxy servers, etc. But how 
> does it make any sense in terms of saving bandwidth, for me, for example, to 
> relay through a different server, to fetch web pages? The web pages and 
> associated files are the same size, whether I get them through another server 
> or on my own, and so I'm using the same bandwidth to retrieve the files. 
> Further, it would inevitably be slower to get those pages, since I'm going 
> through another server. 

Part of the answer is that a proxy is actually a caching proxy server -
or at least, the ones I'm familiar with usually are.
So the proxy server only pulls the page down once, and is actually 
a temporary mirror site. They usually send a 'has this page changed'
packet to the origin site .. but as that's barely larger than a ping, 
it's much more rapid than having to pull the whole page down for you.


An example of the use of a proxy server:

My husband and I both like to read the same comics.
If we both fetch our comics through a proxy server on our local LAN, 
the second person to read the comics gets them MUCH faster - 100Meg
ethernet vs cablemodem+internet - and doesn't cost us bandwidth.
(Ok, we use a flat-rate provider. But we still get it faster.)


How about for the first person? Why does our proxy server  point
to our provider's server?
Well:
Most of those comics are hosted in the USA, our computers are in 
Australia. So there's the trans-pacific link to contend with.
Anything which is on THIS side of the link is faster to pull
down than things on the US side.

That's true even if you don't have to cross a high-latency,
always-busy link - a closer server is going to be faster.

Then there's Yet Another Reason: every hit on a proxy server
reduces the number of hits to the origin sites. So the origin
server has less load, and handles /its/ hits faster.
Most proxy servers save their ISPs enough in bandwidth costs
to ensure the ISP (or other proxy-host) can afford to keep
them powerful enough to give fast responses.
Especially on this island/continent, where our backbone
providers have an effective monopoly. :(


In short, it's actually *faster* if the proxy has the web page
in its cache. If not, the proxy is only barely slower than a
router. So you average out faster, over several pages, even if
every Nth page is slower.




Jenn V.
-- 
     "Do you ever wonder if there's a whole section of geek culture
             you miss out on by being a geek?" - Dancer.

jenn at simegen.com     Jenn Vesperman     http://www.simegen.com/~jenn/