CDN is nothing but content delivery network or can be called as Content Distribution Network which help you to distribute or deliver your contents across the web. In a normal web host all the files are stored centrally within a web server and delivered from that on demand, hence the site load time is greatly depends upon the capability of that server. A Content Delivery Network system keeps the copies of your files at different servers across a global network. These networks are made up of several dedicated servers which works as distributed hosts of your contents especially the static files such as images, videos, Java scripts, CSS files etc. Users are provided with the contents from the servers located at their nearest/fastest point of presence. The host selection is mainly based on users IP address.
Advantages of CDN
- Fast Browsing experience for the users with less site loading time.
- Reduces the resources usage of your parent host, because the bandwidth eating media and theme files are served through CDN.
- Low connectivity latency because of the distributed servers.
- Bandwidth saving. As your media and theme files are served from the CDN servers, it will save the bandwidth of your main server.
- SEO benefits. Google declared site speed is included in their SERP algorithm and slow loading sites can be downgraded.
- Reducing bounce rate. Bounce rate is proportional to the visitors satisfaction, normally people stay away from a slow loading site. Your site may be an awesome source of information but people will not come back if it loads slow.
- Increase the life of your web hosting plan-Read this article.
Types of CDN
To the visitor, all Content Delivering Networks operate in similar way. Contents will be delivered to the visitors from the possible nearest server. But for a webmaster type of CDN matters. Here the type of CDNs
1. Peer to Peer CDN
This technology utilizes the Peer to Peer protocol. Yes the same popular Torrents protocol. Big companies like AT&T and some Non profit organizations are using Peer to Peer technique for content distribution. In this technique no caching is involved, here users are also the part of CDN. Users accessing the content share the parts with others means while downloading the contents, they do upload also without affecting the normal browsing experience. Because of less hardware and resources usage, many CDN providers offer their P2P service at free of cost. PeerCast, PPS.tv, Freecast etc are some examples of Peer to Peer CDNs
2. Push CDN
As the name suggests, in these type of CDNs the contents are physically pushed to the CDN servers. We can say that those servers act as secondary servers to the main server. Here files are physically hosted at the CDN servers. Main server (Your web server) take the files and push into the CDN servers. Amazon Cloudfront is using this technique. If you have a relatively static site with huge files to download, Push CDN is a best choice. Push CDN is also called as Hosted CDN.
3. Origin Pull CDNs
Origin Pull CDN technology is entirely different from the Push CDN technique. Here the contents stored in their respective web servers only. No physical uploading of contents to the CDN servers. Here the CDN pulls contents from the main servers and caching it. As per the user requests, instead of delivering from the main server, contents will be delivered from the cached copies of the nearest CDN server. CDN will keep the files until it expire. Pull CDN is also known as Relayed CDN. This is a most recommended one for WordPress blogs. However if you don’t want to keep your files in your main server to save the disc space, then have to go for Push CDN.
A main disadvantage of Pull CDN is – average or poor performance to the first requesting user. Let me clarify this. You have published a blog post with some images. Now the content is not synced with the CDN server. For the first user who try to access the content, the CDN has to query the original server, pull the file and serve to user. This process take a little bit delay, but once the content is cached, it will be served from CDN servers. However it can be controlled by setting the content expiration time.
Origin Pull CDN or Relaying CDN can be further sub divided into two categories. Full Site Content Delivery and Partial Site Content Delivery.
Full Site Content Delivery CDN
In a full site CDN system the entire web page is delivered from the CDN. Origin Pull technique is utilized for this . Here the CDN servers pull the whole web site and caches on their servers, then which will be delivered to the users on request.
Partial Site Delivery CDN
Here only the parts of a webpage is delivered through the CDN such as Media files, CSS files, Java scripts etc. This embedded contents redirection is achieved through DNS based request routing or URL rewriting.
How to select a suitable CDN
Selection of a good CDN is mainly depends upon your requirements. Requirement of a highly dynamic WordPress blog can’t be equated with a software downloading site or a video streaming site. Here some factors which affect CDN selection:
Requirements: First analyze your requirement and decide whether you want Pull, Push or a Combination of both. If you have a regularly updated WordPress blog with decent distributed traffic across the globe, then Origin Pull CDN is the best option for you. If you are running a website which offer various software, themes, music, videos etc to download then Push CDN is a better choice. Technology of various CDN service providers are not same. For example Amazon Cloudfront uses Push technology, Cloudfront uses Original Pull and MaxCDN gives both.
Integration: Integration of the CDN with your site very much important. This part is primarily depends upon the platform you use. If we take the case of WordPress, the Plugins like W3 Total Cache help you to integrate your blog with popular CDNs. CDN service providers give you t tutorials and tools to assist the integration. Before selecting a CDN, you must confirm that whether it can be integrated with your site or not. After integration also the system should work on auto pilot mode.
Features: Apart from the basic functions, many CDNs gives you Addons like Real-time statistics, Custom Cname records, Firewalls for spam prevention, File upload via FTP and many more. Just go through the features, compare with the competitors
Cost: Naturally this is one of the most important factor we consider. Prices differ from CDN to CDN. Cost of the CDN is directly proportional to your requirements, specifically bandwidth and storage requirements. Just analyze your data requirement, you will get a fair idea through your Google Analytics stats or Awstats. Predict your future requirements as well and go for a suitable data plan accordingly.
Similar Sites: Just have a look at the similar sites and analyze their content type, traffic, site speed and CDN used. This will help you to select a suitable one. It doesn’t mean that you should blindly go behind the same CDN , which is being used by Mashable.
Your Traffic sources: If most of your traffic is from India, and your CDN service providers don’t have servers in India or nearby, then the Indian site visitors won’t be able to get the desired latency benefit. Here the geographical location of CDN servers are important.
Customer Support: Need not to explain this point, just go through the user reviews and select a right one. Most of the CDN service providers offer 24/7 live chat support. You can assess the technical competency of their support team through a live chat session.
Content is the king but slow delivery of contents to the end users spoil it’s value. Hence we must deliver the same to readers as fast as possible. As a performance booster, integration of a suitable CDN with your site is always paramount.