CDN – is short for Content Delivery Network. Most often it is a set of services with a specialized software that accelerate the delivery (“return”) of content to end user. When using this service, the servers are located around the world so that the response time to site visitors is minimal. CDN is suitable to those who need to give statics quickly to many visitors who are far from the company’s servers (the situation is even more acute for companies that have visitors scattered over a large area, that is, even transferring servers “closer” does not make sense – all the same, most will be ” long away”). For those who have a very large amount of files – and the cost of CDN traffic turns out to be lower than the cost of traffic going to uplinks (large sites usually cost different money – local is cheaper, the “global” road.