Retiring, March 2020 - sorry, you have missed our final public course.
The Coronavirus situation has lead us to suspend public training - which was on the cards anyway, with no plans to resume
Please ask about private 'maintenance' training for Python, Tcl, Perl, PHP, Lua, etc
Happily continuing private consultancy / programming work
Routing Network Traffic - Proxies, Redirects and DNS
If you point a domain at web server "X" when it's really hosted on web server "Y", you can either have web server "X" forward the request as a proxy, or you can have server "X" instruct the browser to try "Y" instead ... that's a redirect.
Which is best? A proxy forward hides server "Y" from the browser, but if server "X" has limited bandwidth it will use some of it up. The extra step will also be marginally slower. However, a redirect requires the browser to make a second request of a new server, and server "Y" will not be transparent to the browser.
When you visit a new web site, you'll call up a page based on the domain name ... however, the domain name does NOT tell the structure of the internet how traffic should be routes to the site as it's not based on the network structure - an IP address is required. So the Domain Name Service (DNS) is used to convert the domain name into an IP address, which does reflect the structure.
It works like this - your system (in the imserve.com domain in the example shown here) contacts its DNS server, which knows about DNS servers for its parent and child domains. So it can ask the .com server, which can ask the root server, which can ask .net, which can ask .wellho.net ... and the IP address then gets passed back doen the chain. Having completed that shenanigans, the original machine caches the IP address to save it the bother next time, and uses the IP address directly. (written 2009-05-01, updated 2009-05-02)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articlesA052 - Web Application Deployment - Networking - General 
TCP v UDP / Client v Server - Python examples - (2010-03-25) 
Routers, Firewalls and multilayer servers - (2009-05-01) 
Our new .eu top level domain - (2006-06-19)
Some other Articles
Class Loading and Variable Conversion in JavaMy four feet!What is a JSP tag library?Routing Network Traffic - Proxies, Redirects and DNSVariable scope in Java Servlets and other web applicationsA very easy JSP (Java Server Page)An evening excursion to Devizes and AveburyUsing the internet to remotely check for power failure at home (PHP)Looking for a career change - Physician to Web Site Designer
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