What is a CDN (Content Delivery Network)?

A CDN is a bunch of strategically placed servers grouped around the world in clusters. Each cluster is commonly known as a POP (Point of presence). The network capacity of these POPs is higher than a standard ISPs backbone capacity, which can result in an impressive increase in the number of concurrent users a website can support.

An example would be if you have a 10Gbit/s capacity backbone (quite impressive), but you have 20 x 10Gbit/s servers. You can only push data at 10Gbits. If you now employ a CDN and those 20+ servers, are on separate 10Gbit/s networks, like the one we use for hybrid hosting, now you can push 200Gbit/s+

One of the most costly things apache does, in terms of performance,  is having to open and close new network connections when new customers connect and eventually leave. This is time consuming and also places an overhead on the network bandwidth.

The use of a CDN places the overhead of opening and closing of these connections to the servers at the edge of the CDN network (“edge servers”).

Usually a CDN caches all of your static content on the edge servers so your main website only has to serve the HTML ( or php’s HTML output). However you can also “proxy” the dynamic data. That might seem slow, but actually it accelerates the application, as the edge servers, whose IPs remain the same to apache, even when serving different customers, are able to make good use of KeepAlives, further reducing apaches need to open and close network connections. (The only downside to Dynamic Acceleration is that you pay for the bandwidth twice, once between your server “the origin” and the CDN’s server “the edge” and once more between the edge and the customer.

If you website warrants it, we can offer Hybrid CDN Hosting, which is basically your high visitor website hosted on standard shared hosting, wrapped with a CDN. This is often much faster than a dedicated server and considerably cheaper if your bandwidth is not too high. This is a particularly good solution for sites that have varied/unpredictable visitor numbers.

These solutions, whilst similar, are custom so if you think your site needs CDN acceleration, raise a support ticket.

Also you can ask us to quickly and temporarily CDN your website should it come under particularly high load, if some of your content goes viral.