I would like to build my own Content Distrobution Network and I have come across a blog post showing how to do it with one of Google's services. But I can't understand it. Here's a few more questions.
Are images hosted in Flickr considered to be "in a CDN"?
If I create a subdomain within my domain, put directories for files in there, and link from my site to that subdomain, is that considered a CDN?
A content distrobution network (CDN) is not just another place on your website. A CDN is a way of distributing content to different geographical/network locations.
CDNs receive requests based on DNS redirection at the client ISP's side of the request.
from wikipedia:
A content delivery network or content distribution network (CDN) is a system of computers containing copies of data, placed at various points in a network so as to maximize bandwidth for access to the data from clients throughout the network. A client accesses a copy of the data near to the client, as opposed to all clients accessing the same central server so as to avoid bottleneck near that server.
I suppose that once you replicate content across some computers around the world, any url should be fine.