What is CDN? How it works ?

A content delivery network (CDN) is a distributed system of servers, strategically deployed in multiple data centers across the globe. Within a CDN your content is available in many copies throughout these servers. In other words, a CDN is an interconnected system that cache, stores, and distribute your content to many end users simultaneously based on their proximately. The ultimate goal of this technology is to deliver content to thousands of end users with high availability and high performance.

For instance, if your website is based in Los Angeles, the people who are accessing it in San Francisco will receive the content faster than people accessing it from Shanghai. The farther away the person accessing the website or application is, the longer the load time and the more frustrating the user experience becomes.

How Do CDNs Work?

CDNs are made up of a network of servers referred to as “points of presence” or POPs. Each one of these servers (POPs) are expanded in locations all over the world. The CDN server that is located closest to where the user accesses it is called an “edge server.” When a user requests content from a website or application through a CDN, they will be connected to the closest edge server. This ensures the user will receive the best experience possible.

Why we should use CDN?

  •  Faster Performance and Lower Latency

The very first reason to use a CDN is providing an easy way to increase the speed of your websites while lowering the latency simultaneously.

  •  Traditional Web Hosts Can’t Keep Up

traditional web hosting is no longer capable of meeting the demands of websites. A CDN, made up of edge servers which are deployed in different parts of the world, now play a significant role in surpassing the computing resources of traditional web hosting in order to deliver rich and high-quality multimedia content in a reliable and cost-effective way. CDNs now are responsible for a majority of the load on a lot of websites. This can allow for savings on your web host, and also less of your resources being use

  •  SEO Advantages

When it comes to search engine optimization (SEO) page speed is a very important factor as it pertains to page rankings. Most search engines consider the page loading time in their formulas.

Example: Google loves fast websites and announced in 2010 that website speed would begin to affect search engine rankings. The faster your website is, the better chance you have moving up in SERPs.

  •  Reliability

Some websites may go down at one point, which can be very frustrating. Whenever using a CDN, it is true that there is now another point of failure. However, because of how a CDN’s architecture is setup, it actually provides reliability. With a CDN, requests to the specific website are always redirected to the nearest available POP. If one request fails and happens to be down, it simply just passes the request onto the next one.

  •  Traffic Spikes & Scalability

With the majority of resources now being delivered via the content distribution network, your origin server doesn’t have to work as hard.This allows your website to be much more scalable with minimal effort and avoid any downtime scenarios which could actually cost you money.

  •  Better Security & DDoS Protection

A CDN can provide additional security. Since 60%+ of the traffic is being served through the CDN provider, they will mitigate DDoS attacks for you on their edge servers

  •  Lower Costs

a CDN in most cases will most of website’s bandwidth, which in return reduces the load/costs on your origin server.

What is Static Content?

Static content is any content that can be delivered to an end user without having to be generated, modified, or processed. The server delivers the same file to each user, making static content one of the simplest and most efficient content types to transmit over the Internet.

What is Dynamic Content?

Dynamic content is the term used to describe site content that automatically adapts to various pre-defined conditions, such as particular user signals. The content featured on the website will adjust dynamically, so that different users see different content. Dynamic web page: example of server-side scripting (PHP and MySQL).

Dynamic Content Acceleration: What is FEO (Front-end Optimization)?

The term “front end” relates to the interaction between your website and a user’s browser in the context of web services. Front end optimization (FEO), which is also familiar as content optimization, is the process of fine-tuning your website to make it more browser-friendly and quicker to load.

Broadly speaking, FEO focuses on reducing file sizes and minimizing the number of requests needed for a given page to load.

During the FEO process, web designers draw a distinction between the perceived and the actual page load time. Perceived load time is considered because of its impact on the overall user experience while the actual load time is often used as a performance benchmark metric.

How does using CDN affect SEO?

CDNs improve the speed and quality of content that is delivered to the user. CDNs should be seen as part of the solution for search ranking as it is applied to page speed and efficient content delivery, but it is not the only thing that needs to be done to increase search ranking. Think of CDNs as a way to improve upon the technical ranking factors for SEO.

For instance, CDNs help to ensure each version of your website across several servers and locations are identical. CDNs use caching algorithms and canonical headers to help enhance SEO of your website by combatting duplicate content creation issues.

It is obvious that load time impacts its search ranking. SEOs everywhere have stressed page load time and page speed must be considered, and Google has even admitted that page speed does matter. CDNs play a huge part in optimizing page speed and many people aren’t familiar with CDNs or the process in which they can improve page speed.

when it comes to SEO Using a CDN will:

  • Improve the load time of your content
  • Reduce the open connections to your web server
  • Increase user experience and site performances
  • Lower image size sent to the user
  • Minimize traffic spikes at point of origin to save your website stability
  • Help scale in case of high traffic

Will using CDN reduce DDOS attack?

Many organizations also mistakenly believe that Content Delivery Networks (CDN) provide a solution to stopping DDoS attacks. The fact is that a CDN merely addresses the symptoms of a DDoS attack. By absorbing these large volumes of data, a CDN actually let all the information into and through the network, also providing an “all are welcome” approach. In addition, most CDN based DDoS protection solutions only focus on absorbing HTTP/HTTPS DDoS attacks, ignoring all others such as NTP/DNS amplification attacks, which are very common.

CDNs offer two main forms of cloud-based DDoS solutions

  • always-on solutions, which provide symmetric protection for regular operations,
  • on-demand solutions, which offer asymmetric protection for higher threat situations.

What is Anycast DNS?

Anycast is networking technique where the same IP prefix is advertised from multiple locations. The network then decides where to to route a user request to, based on routing protocol expenses and possibly the ‘health’ of the advertising servers. There are several benefits to anycast.

  • First, in steady state, users of an anycast service (DNS is an excellent example) will always connect to the ‘closest’ (from a routing protocol perspective) DNS server. This reduces latency, as well as providing a level of load-balancing (assuming that your consumers are evenly distributed around your network).
  • Another advantage is ease of configuration management. Rather than having to configure different DNS servers depending on where a server/workstation is deployed (Asia, America, Europe), you have only one IP address that is configured in every location.

Packet latency is largely a function of geographic distance. With anycast we tell routers the same server is located at a bunch of different spots around the internet. Because internet routers are always optimizing routes they pick the one closest to your customer. Moving DNS server’s closer mitigates this geographic latency component. While lower latency is the one of the important benefits we also gain resilience at the same time.

Are CDNs valuable for video streaming?

Definition: A video CDN, or video content distribution network, is a large geographically dispersed network of servers delivering live and on-demand, high-quality videos to web-connected devices. These specialized video streaming server networks accelerate delivery through caching, which stores content temporarily on multiple servers throughout the video CDN. When a viewer submits a request, the server caching content nearest the user’s location delivers the video.

To keep up with the rising demand, network service providers realize the need to build their own content distribution networks supporting VOD server (video-on-demand) and IPTV server (Internet Protocol television) technology. Network service providers that deploy their own video CDN can reduce subscriber churn by:

  • Reducing traffic on the primary network, which improves video content and web performance overall.
  • Creating and deploying value-added, targeted services to attract new customers and retain existing subscribers.
  • Content providers also benefit from a video CDN, as customer conversion rates increase and loyalty strengthens.
  • CDN video streaming can greatly accelerate the delivery of video media and make the environment more secure and reliable. CDNs provide a lag free viewing experience, the most important thing for user satisfaction.

Generally, all Top tier CDNs are good for video streaming but every one of it has its own pros and cons. Some of the important factors to keep in mind are:

  1. Geography – Are your viewers distributed all across globe, or mainly concentrated to certain continents or countries like Asia, Europe, USA, China. Reason I am pointing out is certain top tier CDNs have low presence in Asia, especially China while some of the CDNs are generally built for specific areas. Many CDNs specially catering to USA only.
  2. Scale – Are you looking to live stream an international sport event or it is a small Video on Demand service? Only some CDNs in world are currently efficient enough to cater to huge scale worldwide specifically for live streaming.
  3. Pricing – Are you a startup more comfortable with pay-per-use pricing or able to commit considerable bandwidth beforehand. Different CDNs cater to different business models.
  4. Some of top tier CDNs are Akamai, LimeLight, Cloudfront etc. One more thing is do you really need a direct CDN service to build your business, can certain OVPs (Online Video Platforms) who already provide integrated CDN, Player, DRM , Streaming, Analytics services might cater best.

Are CDNs effective for mobile user?

Mobile traffic is increasing which has made it mandatory for mobile websites to be fast and responsive to user requests. Mobile CDNs optimizes this with the Radio Access Network(RAN) acceleration by using the TCP acceleration. It reduces the excessively advanced downloading of video content through video pacing. RAN helps in reducing mobile data traffic through text compression.

Several studies have reported that the visitors requesting content from their mobile devices can easily find a difference of at least 10% faster page upload on servers with a CDN in comparison to the response from sites without a CDN. Users on mobile devices expect performance to be at least similar if not better to what they get on their desktops. Mobile acceleration can also be improved by optimizing the locations of POPs (points of presence)

What is Hybrid CDN?

Hybrid CDN is the solution for medium size company. Basically means, you are still using third party cdn. But on the top of that content delivery, you are going to build your own, so you are boosting that third party cdn. That is because, commercial cdns just simply provide a service for you and hundreds of other companies. So they can’t analyze performance for your personal use case If you want to make sure you are optimizing your content delivery you have to do yourself.

A Hybrid CDN mixes Private and Public CDNs to deliver live and Video on demand content. It optimizes the cost, performance and resilience of your video service. Public CDN gives reach. Private CDN gives cost-effective scalability.

What is Geoblocking?

Geoblocking is the is a form of technological protection measure used to limit end users access to the internet, limit or change the content based on users geographic location. The end user’s location is calculated using geolocation techniques, then the user’s IP address is checked against a blacklist or whitelist; the result of this check is used to determine whether the system will approve or deny access to the content on the Internet, such as films and television shows, primarily for copyright and licensing reasons. There are other uses for geoblocking, such as blocking malicious traffic or to enforce price discrimination, location-aware authentication, fraud prevention, and online gambling.

A good example of this would be in the case of BBC iPlayer. The British Broadcasting Corporation is a public service broadcaster in the U.K run by the British government. The company is funded by tax payers in the United Kingdom; therefore, it is free to all British citizens.

The BBC originally was broadcasting via radio and television in the U.K, but, moving along with technology, they starting streaming their content online. This online service is called BBC iPlayer which allows users to watch live and on-demand movies, TV shows, and sporting events. However, to make sure that it’s only U.K residents accessing their services, BBC iPlayer first checks visitor’s IP addresses to make sure they are originating from the U.K.

If someone outside of the U.K was trying to access BBC iPlayer, she/he would get an error message (HTTP 403 Forbidden) . She/he gets this because BBC iPlayer has checked the IP address and knows that it is not located in the U.K.

Where can I see my purge request result?

Purge request results can be accessed by checking the Purge Stats list from zone details page. If your request was bulk or rest api request then let the application has enough time to be able to finish all the requested operation.

What is the difference between Origin Pull and PoP Pull ?

There are two methods for content distribution in CDN: Origin Pull and PoP Pull. These methods are differentiated as the experience of the first requesting user and the place where the content is stored.

In Origin Pull, the content is available on any server or computer connected to the Internet. The location of the content is then saved to the CDN. In the first user request, content is brought from this location to the nearest point to the end user via the network. There is no need to manually download content to the CDN. Pay As You Go or pay per month according to the bandwidth is used. To use the Origin Pull method, bandwidth planning is needed. The CDN user doesn’t pay the storage fee.

In PoP Pull, the content is uploaded to the CDN and waited for service to end users. In any end-user request, content is served from the nearest CDN node. The PoP Pull method requires storage and bandwidth planning.

Who needs CDN ?

CDNs  are  ultimately  responsible  for  the  performance  and  user  experience of any online service that depends on fast, low latency delivery of files, images, scripts and other content.

They are fundamental to online broadcasters and other Over-The-Top service providers, who either build their own private network for content delivery, or partner with a CDN service provider. CDNs provide a revenue stream for companies with distributed network infrastructure, such as telcos, who can monetize that infrastructure by using it to take CDN services to market – and use CDNs to control traffic flow across that infrastructure, to reduce costs.