What is a CDN? How does a CDN Work?
Content Delivery Network is a network of geographically spread servers caching static files and enhancing their delivery
What is a CDN?
When content is sent from the origin server to a web-site visitor, the speed of transfer depends on the physical distance between them to much degree. The more round-trips data has to travel, the longer it will take for a web-page containing it to open. For example, if a user from China tries to access a web-site hosted on an American server, he will have to wait for web-site opening longer than a user accessing it from Mexico. What are content delivery networks? The idea lying at the core of CDN is to reduce the distance between the source of content and the end-user. The fewer miles content has to travel, the faster it will be delivered to a user.
This video explains what is CDN in detail:
Thus, answering the question “What is a content delivery network?” we can say that this is a chain of servers spread around the world or located in mission-critical regions that are used to cache and store content to accelerate its transfer to users.
How CDN works?
First and foremost, it is important to note that CDN does not replace usual web-hosting, it works alongside with it. What is CDN service then? This is an additional network that serves to cache and store static content on geographically distributed servers. Its infrastructure includes the origin server (one that the owner uses to store and upload content) and edge servers distributed across several regions. Edge servers are located in datacenters that are called PoPs (Points of Presence).
When a user sends request for some web-page or content, it is first directed to the origin server and only then the content is transferred to him. When CDN is implemented, requested data is saved on edge servers and sent from them down the road. Consequently, a request is sent to the closest edge server. Thanks to that, content travels shorter distance, and it take less time for web-pages to load./
The picture below perfectly describes how CDN works.
As soon as content is loaded on the original server, it is automatically cached on edge servers after primary requests. If a user sends a request for the content that has never been cached on an edge server, it will be obtained from the original server.
How does a CDN work, if some of edge servers are down? Intellectual system will redirect users to other edge servers located as close to them as possible. The same is done in case of traffic spikes to provide load balancing and prevent server downtime. Besides, this way load on the origin server is reduced. Content delivery network is created to cache static content primarily. That includes:
- Images and videos of different formats;
But how to use a CDN with dynamic content? For this purpose, special CDNs for streaming were created.
Advantages and Disadvantages of a Content Delivery Network (CDN)
Benefits of a CDN
What is CDN benefit? In fact, this technology has a lot of positive effects for online business. Its main advantages include:
- Higher speed of web-site loading and content transfer. The distance between the end user and the server reduces, which requires less hops for the data to overcome.
- Better quality of content such as images and video. Reduction of physical distance between the source and the receiver decreases the chance of data loss and faults.
- Improved security. CDN serves as an additional security level and provides firewall. Users’ requests are filtered through it, which allows identifying a threat and eliminating it before it reaches the origin server and affects it.
- Reliability and 100% uptime. Even if one or several edge servers go out of service, other servers of the network will stay up and serve content for the users. That almost excludes the probability of web-site downtime and provides data back-up, because copies of content are stored throughout the network.
- SEO benefits. The faster a web-site loads, the better it will be ranked in Google. Ideally, it should take up to 3 seconds for a web-page to open fully.
- Excellent user experience. Visitors hate visiting slow pages and don’t hesitate to leave sites that load for ages. The less it takes for your web-site to load, the better will be users’ satisfaction. As the result, you will have lower abandonment rate and more loyal customers.
- Higher conversion rates. This is the outcome of the previous point. The more people like your web-site, the more time and money they spend for the services and vice versa. It is estimated that even one additional second of loading may result into 7% of revenue loss.
It is not possible to figure out exact percentage of speed increase in every separate case, but practice shows that it may boost a web-site by 70%.
Disadvantages of CDN
Although CDN is a very useful and efficient technology, there are some drawbacks. Let’s take a closer look to disadvantages of CDN.
It’s not equally suitable for all businesses
Since CDN is created to serve customers from different regions, it consists of numerous servers that duplicate the content. Websites that are aimed at some certain target audience only will not benefit from CDN. Moreover, it can only make things worse by connecting website visitors with far-off nodes and slowing down page loading.
But if you have a more or less large website with traffic coming from different locations, a correctly chosen CDN network will definitely solve the problem of latency and slow loading.
CDN providers may have completely different pricing policies. Some companies have limitations of services and charge for advanced features, others can have high setup fees or hidden payments. High fees can repel small clients, when companies focus on large businesses. In some companies, pricing policy isn’t transparent, and it’s hard to understand what the tariff plans are based upon – bandwidth, requests, or data transferred. Therefore, it’s important to understand all terms and conditions prior to signing a contract.
Luckily, today there are many CDN providers with acceptable minimum payments: individual clients can find decent CDN services for as low as $5-10 per month! The market is full of providers, and it’s possible to figure out a network that will match your budget and needs.
As far as the vast majority of organizations work with third parties to maintain their CDNs, clients can face the problem of availability of customer support. Will the operator be able to fix issues in time and prevent the same problem from happening again? The best thing you can do is read reviews, order free trials and talk to customer support before starting using a network.
Together with solving arising issues, the CDN provider is also responsible for maintaining every server with patches and updates without interrupting the work of client’s network. Placing your website online business into the hands of an operator is a serious decision. Therefore, you need to pay attention to all factors: how servers are maintained, how applications are updated, how backups are organized, and so on.
Verification of the Best Locations
To top it off, companies need to research the location of the servers provided by CDN operators and find the ones that fit their requirements best, e.g. cover targeted regions. A CDN which servers are located at a huge distance from users is pointless – such service will only result into service disruptions, jittery images and videos, low performance and downtime. Therefore, it’s crucial to find a CDN that covers exactly the regions that you need, because only in this case it will be beneficial for your visitors.
If you have a large website with a lot of assets and pages, as well as international traffic, it’s crucial to have a system that ensures excellent performance and reliability. CDN is able of accelerating and protecting your content – you only need to find a solution that matches your budget and needs.
Do I need CDN?
Today, content delivery networks have become very popular among e-commerce retailers, online video services, social media and other global corporations. Although this technology is helpful for huge companies, it will not necessarily be beneficial for your online business. How can one know whether CDN will be useful for his or her project? The answer to the question is simple.
If your target audience is spread across several geographical regions, CDN will help to distribute web-content and accelerate its delivery improving user experience. Benefit is especially evident when using a network with global coverage – it makes huge difference. On the contrary, web-sites with visitors located in one certain city or region won’t work faster with CDN; it may even make things worse and decrease the speed of delivery.
At the moment, the service is not as expensive as it used to be. Some three years ago it was considered to be a luxury, but now is thought to be a must-have for companies that want to improve connection, boost file transfer speed and make user experience perfect.
What is CDN cost? First and foremost, it depends on the provider. There are free solutions, but their quality is not sufficient, and they are prone to downtime. Cheap CDN solutions may start from a few dollars a month. For instance, you can order a CDN for as low as $10 a month here. The price shall comprise the following elements:
- Level of customer service and technical support.
- Coverage (number of PoPs and their location).
- Speed of connection.
- Security options.
- Duration of contract (if there is any).
Thus, you can always figure out an affordable CDN solution for you business and its costs will be compensated quickly.
CDN vs Infrastructure Expansion
Some international companies are not aware of CDN technology and do not plan to use it preferring to expand infrastructure and lease servers in different regions. Undoubtedly, market leaders can afford such option. But the benefits of CDN are not confined by its price only. It has a few more advantages:
|Price||Reasonably low. More information about our CDN pricing model||Foreign web-hosting is more expensive, especially when it concerns single servers in different locations.|
|Efforts||Information from the origin server is cached on edge servers automatically. When a file on the origin server is edited/renewed, it is altered on edge servers, as well.||User has to upload content on each server separately and constantly update it. That takes much more time and supposes additional expenses.|
|Time||You order CDN once and only need to pay for it monthly. If required, you can switch to a better solution.||Expansion of infrastructure takes months, sometimes – years. You have to spend time for searching servers and customizing them.|
How to choose the right CDN provider?
Search of a suitable content delivery network and provider can be difficult. How to define what is a content delivery network that will work for you? First, you should determine your requirements and peculiarities of your web-site: target audience, the volume of traffic, security features you need, etc. After that, you may search for a company and analyze its services. Take into account several crucial aspects.
Does a CDN service you are offered cover all mission-critical regions? If yes, how many PoPs are provided? To ensure efficient content delivery across several continents, 30+, 50+ or 100+ PoPs should be included.
There are two major pricing models for CDN services: per-gigabyte and pipeline pricing. In the first case, you pay for every gigabyte of traffic used by fact, in the second – pre-pay for a package of gigabytes included (if the limit is exceeded, user pays according to another plan). It is impossible to say which one is better – it depends on a web-site. If your site experiences unpredictable traffic spikes, it is better to select per-gigabyte pricing, while pipeline pricing is suitable for web-sites with even and predictable traffic flow.
Some companies offer discount for contract-based CDN services, but this can be a dangerous option. If a user does not like the quality of service or wants to change a CDN, he can lose money and even stay without compensation. It is better to choose pay-as-you-go option, or opt for short-term contracts (2-4 months maximum).
It is important to have experienced and friendly technical staff helping you. Before using this or that network, make sure that the customer support service is 24/7 available, its agents reply quickly and really help to solve issues. It is convenient to have several means of communication: e-mail, phone, tickets and social media (Skype, WhatsApp, etc.): this way you will be able to contact the staff anytime.
Prior to making an order, you can contact the support service and ask questions. You may also get information about CDN solutions available and ask to find the most optimal configuration for your business. That will allow to evaluate competence, knowledge and friendliness of the agents. A decent provider does its best to have clients satisfied.
Many companies allow checking their CDN before you agree to order the service. That can be done several ways. First, you may get a free trial period (it usually lasts up to 1-2 months) and see how the network would improve speed. Secondly, some companies allow running their CDN using their demo versions or pages of your own web-site. It is worth spending some time and testing several CDN solutions: write down the results ‘before’ and ‘after’ and choose a service that makes the most difference.
CDN is an opportunity to enhance web-site speed and user experience without spending too much money. This is the technology of the future that is already available to you. Order a CDN, and your online business will be much more successful and profitable.