CDN – Content Distribution Network Consulting

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With about 1.5 billion websites live worldwide, getting a website to be relevant online is increasingly becoming a daunting task for all businesses – large or small. Web speed has become an important parameter that webmasters should address because when a website is too slow, visitors run out of patience and abandon the site for a faster one offering similar information or products. Moreover, Google now uses page speed as one of the criteria for ranking web position in search results. Very slow websites may never be found. This problem is worsened when a website visitor is too far from the website server because the high latency and other distance dependent impairments cause long website load times. Most website owners are now resort to using a CDN or content a delivery network to significantly boost their web speed for all potential customers regardless of how far they are from the hosting servers. On this page, we share some important information about CDN, especially for those in the market for one.

What is CDN?

A CDN or Content Delivery Network (also referred to as a Content Distribution Network) is a network of servers geographically distributed for the efficient and fast delivery of content to end users. Content delivered by a CDN can include all the assets required to load a website, documents, images, videos and audio. Most website owners today use some form of CDN either through their web hosting provider or a third part provider.

How does CDN work?

The schematic illustrates the concept of a content delivery network. The content is hosted at the hosting server known as the origin server, such as your web hosting provider’s server. Copies of the content at the origin server is copied, delivered and stored or cached on multiple edge servers. When an end user requests content from the source URL, they are saved with content from the edge server nearest to them. If the origin server is in San Francisco and the end user is in Harare, Zimbabwe, for example, they would receive their content from an edge server in Southern Africa, closest to them.

CDN benefits

CDNs are used to realize a number of benefits, including:

  • Improving latency and website load time
  • Improved availability and redundancy
  • DDOS mitigation
  • Video streaming


 CDN latency and website load time

Latency is the delay between the time an IP packet is sent by the sender and the time it is received by the receiver. Website load time is significantly impacted by the round trip latency between the server and the user. While the actual value of latency can be very modest, it translates into significantly higher website load times. For example, the round trip latency between Los Angeles and New York City is only about 70ms but the impact on load time can be higher than 1s. This is because multiple requests should be sent to the server before the website is loaded. When web servers are located too far from the user, the high latency and other impairments such as packet loss can severely degrade performance, making it undesirable for visitors to return to the site.

When it comes to the success of a website, including its influence and ability to generate revenue, load time is increasingly becoming one of the most important metrics. Most visitors will abandon a website that does not load in 3s, and they will simply move on to a competing web site. Google has also made load time an important metric to rank the position of websites in its search results. If your website is too slow, it might not rank and never be found in Google organic search results. A CDN will address this problem by drastically reducing latency and website load time.

Availability and redundancy

Availability, the opposite of downtime, is the probability that a site is functional at any given time. Availability is a key attribute in Service Level Agreement (SLA) because for mission critical business applications, sites should be available at all times. Latency, packet loss, power outage, and cable damage can all lead to high downtime and, consequently, low availability. Having multiple edge servers in a CDN close to the users does not only ensure low latency but also offer alternative access paths to content. Redundancy is the availability of an alternative network path to a website in the event that the default path fails. Internet users in East Africa and other emerging markets are well aware of the loss of access to some overseas websites whenever a submarine fiber optic cable goes down. By its design, a CDN has multiple redundant paths to the same content, albeit on different servers. With a CDN, a user in East Africa may not need to access USA content over submarine cable because copies of the content may be available locally in Africa.

DDOS Mitigation

DDOS or distributed denial of service is a hacker technique to deny service to a website users by making thousands of simultaneous requests from the site using multiple (distributed) connected devices. Although there are several solutions to address this type of attack, the correction sometimes takes place after some disruptions have already occurred. With CDN, the attack is distributed over multiple servers and will have less of an impact compared to a scenario in which the attack is concentrated only on one server.

CDN is a must for video streaming

Video streaming consumes large amounts of bandwidth. Having thousands of users accessing video content from a single server can result in congestion and poor user experience. By moving copies of the video content to edge servers such congestion is mitigated,

Important considerations when selecting a CDN

Using any CDN provider will offer you significant advantages over relying on a single server to deliver content. However, some CDN providers will offer you more value for your money. Moreover, some providers will be more suited to your specific situation than others. If most of your customers are in Johannesburg, South Africa, for example, there is no point selecting a highly rated CDN provider with thousands of servers outside Africa. Evaluate CDN providers against important features including:

  • CDN global reach and QoS
  • CDN Speed
  • Pricing model
  • CDN provider’s customer support
  • Dynamic content delivery capability
  • Maximum size that can be cached
  • Comprehensive analytics


CDN global reach and quality of service

Different CDN providers focus on different geographical regions. At a minimum, you should ensure that the CDN provider has edge servers in or near the cities where your customers are located. If you are doing business globally, your CDN provider should have global reach, with edge servers around the world. For good user experience for your customers around the world, the provider should guarantee global quality of service (QoS). When CDN providers use the public Internet to deliver your data, the CDN may be subjected to local poor quality Internet access especially in emerging markets. Insisting on QoS guarantees ensures high quality user experience for your clients.

CDN speed

Check out reviews to find out actual speed experienced by others already using the CDN of interest. The whole point of using the CDN is to improve speed and at a minimum, your CDN should be faster than accessing your site without the CDN.

Pricing model

CDN pricing models can be complex and the onus is on you, the user, to choose the provider and pricing model that makes the best sense for your business goals. There are three typical pricing components charged by CDN providers namely; a fixed cost, bandwidth cost and cost for requests. The bandwidth cost varies with location and decreases with the bandwidth consumed. For example, in 2020 the Google Cloud CDN pricing is $0.08/GB for the first TB, $0.055/GB for the next 140TB, $0.03/GB for the next 850TB and $0.02/GB for > 1000 TB in North America. Corresponding costs in China are $0.20, $0.17, $0.16 and $0.145. In addition to bandwidth costs, Google also charges for Cache egress, cache fill, HTTP/HTTPS cache lookup requests and cache invalidation. Other providers have much simpler models where they charge only for bandwidth usage. Others, such as Cloudflare, even offer fixed price plans for personal websites and small businesses which include a free plan, Pro ($20), business ($100). They also offer an Enterprise plan which is charged per bandwidth usage.

CDN provider customer support

Customer support could well be the most important differentiator between two technically sound CDNs. As you migrate from using a single origin server to a CDN, you are probably entering an unfamiliar territory and you may run into a few technical issues. Quick and timely responses to your issues are imperative to ensure seamless continuity for your website visitors.

Dynamic content delivery capability

While all content delivery networks can handle static content, not all of them will properly handle dynamic content well. Static content such as style sheets, JavaScript, images, videos and audio do not change and can be easily cached. The CDN updates the content periodically with new static content from the origin so that the content on the edge servers is a true reflection of the origin content.

Dynamic content, on the other hand, is typically generated on the fly when a website visitor opens that page. It executes code and usually has to access a database to complete its task. Social media sites that serve different content to different users, stock prices, basketball scores, and news content that change rapidly are good examples of dynamic content. Dynamic content is difficult to cache so many CDN providers either cache the static components of sites and have the dynamic components accessed directly from the origin or update the edge servers as frequently as possible. Some CDN providers have special capabilities to automatically update the edge servers whenever there is a change on the origin. If you have dynamic content, it is imperative that you chose a CDN provider that can best handle your content.

Maximum file size that can be cached

Many CDNs are optimized for small size delivery and impose a limit on the file size that can be delivered to edge servers. On the other hand, CDNs targeting enterprise customers are optimized for large file transfer and may not impose limits on file sizes. Microsoft Azure, for example, does not have a file size cap while Cloudflare limits file sizes to 512MB for the Free, Pro and Business plans while the limit for Enterprise accounts is 5G. Consider the maximum size of your files as you make a decision on a CDN provider.

Comprehensive analytics

When you pay for a CDN service, you want to have a very good understanding of what it is that the CDN is doing for you. A good CDN comes with comprehensive analytics that will help you understand what goes on in the network. Analytics should include web traffic requests by country, cached vs uncached content, bandwidth usage, and unique visitors to your website. CDNs that include security will also show you the number of attacks attempted and foiled.

The FiberGuide CDN proposal service

FiberGuide is a one stop consulting service for CDN services. Let us handle the arduous task of evaluating your requirements against the multitude of CDN providers in our network. Contact us with details of your requirements and we will get back to you with a proposal free of charge.

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