What is a Content Delivery Network (CDN)?

A content delivery network (CDN) is a very large system of distributed servers which are at multiple locations over the Internet. The main aim of a CDN is to be able to make content to available to the users. CDNs are the larger chunk which hold the Internet content today which include

a)    Web objects such as text, graphics, URLs, etc.

b)    Downloadable objects like software ,media files, documents, etc.,

c)    Applications such as portals and e-commerce, ondemand streaming media, social networks and live streaming media.

A CDN operator is paid by the content providers who are mainly the media companies and the e-commerce vendors for providing the end users with their content. The CDN pays the network operators and the ISP carriers for hosting its servers. The CDN’s also help in offloading the traffic from the content providers infrastructure, ultimately saving costs.

A CDN generally hosts content in multiple copies on its distributed server system. This practice is commonly known as content replication. A huge CDN network can consist of thousands of servers which commonly aim at delivering content to the user in an efficient and reliable manner. This network is designed to work with the same efficiency and reliability during Maximum traffic times and demand spikes as it would during off peak traffic.

The Benefits of Using a CDN

The various ways in which a CDN could benefit a business, website or company are:

1.    Different domains

Generally browsers set a limit to the number of file downloads to a single domain. The number is generally limited to 4 active connections, meaning which the fifth connection is in queue unless one of the previous ones have downloaded. This is often a practice when downloading large file from a particular site. Since CDN files are on different domains, the browser allows more number of downloads at the same time.

2.    Pre-cached files

There might be a high possibility that a visitor has already visited a site using the CDN. Hence the file has already been cached by the browser and would not be required to download again.

3.    High-capacity infrastructures

Although a CDN might have great hosting, a CDN’s may not be able deliver a good capacity to the scale that is offered by the major players such as Yahoo, Microsoft, Google,etc. It’s always good to use a high end CDN so that it can provide better availability and lower packet loss and latency.

4.    Distributed data centers

Generally when a distant visitor tries to visit a site, their landing is not direct. There is a lot of hopping and skipping before actually getting there. Good CDN’s generally localize their data centers so that it is easily available and can ensure faster and more reliable downloads, especially in the case of trans-continental situations.

5.    Built-in version control

It is generally possible to link up to a particular version of a JavaScript library or CSS file. The “latest” version can be requested if it is necessary.

6.    Usage analytics

Most of the commercially large CDNs generally provide a report of the file since they charge on the basis of bytes. Those reports are generally more accurate than the analytics of the website.

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