Exploring the Principles and Advantages of CDNs

CDN, full name Content Delivery Network, is also known as Content Delivery Network. It is like the “invisible courier” in the Internet world, silently accelerating our network experience. Simply put, CDN is a virtual network composed of servers and data centers distributed in different geographical locations. Its core principle is to cache the content of the source station, such as images, videos, scripts, etc., to the servers of nodes closer to the user. When you browse the web, CDN will intelligently select the nearest node according to your geographic location, network conditions and other factors to deliver the cached content quickly, greatly reducing the distance of data transmission and distributing the content to you with minimal delay. 

Benefits of CDN

Accelerate Access, Say Goodbye to Lag

The primary superpower of a CDN is to make web pages load as fast as lightning.It dramatically reduces network latency by distributing content to nodes all over the place, allowing users to get what they need from the closest node.It's as if you can buy your favorite items at the convenience store at your doorstep, instead of having to go all the way to the big supermarket in the city center to make purchases.When you click on a web link, the data no longer needs to travel long distances from the source, but is delivered directly from a local or neighboring CDN node at high speed.As a result, the access speed of the website has taken a qualitative leap, the waiting time of the user is greatly shortened, and the page response is more responsive, which greatly improves the user experience.

Reduced pressure on the source site, stable operation

The appearance of CDN is like a group of powerful assistants to the source station, which can share a lot of traffic to the nodes around the world. Static images, scripts, stylesheets, etc. will be cached by the CDN in the node close to the user as soon as the user accesses them for the first time. Subsequent access to the same content by other users, directly from the CDN node to obtain, without the source station to repeat the process, which greatly reduces the pressure on the main server, so that the source station can be “lightly loaded”, focusing on dealing with those dynamic, personalized data requests. This not only reduces the load on the source station, but also effectively avoids the risk of server paralysis due to traffic bursts and ensures stable business operation. At the same time, it reduces the resource investment in the source station and lowers the operation cost of the enterprise, which can be said to be multi-purpose.

Break the cross-network bottleneck, unimpeded travel

In your daily life, you may have experienced that when you use Unicom's network to access the website on Telecom's server, the speed is always unsatisfactory, the video lags, and the picture loads slowly. This is due to bandwidth limitations and differences in routing policies between different carriers, resulting in poorer cross-network access quality. A CDN is like a bridge that bridges this gap. It deploys nodes in each operator's network. No matter which operator's network a user uses, CDN can intelligently guide the user to get content from nodes of the same operator or similar networks, ensuring efficient and smooth data transmission, breaking the cross-network bottlenecks, and allowing every user to enjoy smooth and unimpeded network services, greatly improving service quality and user satisfaction.

Escort content security, no worries

In your daily life, you may have experienced that when you use Unicom's network to access websites on Telecom's servers, the speed is always unsatisfactory, with videos lagging and pictures loading slowly. This is due to bandwidth limitations and differences in routing policies between different carriers, resulting in poorer cross-network access quality. A CDN is like a bridge that bridges this gap. It deploys nodes in each operator's network. No matter which operator's network a user uses, CDN can intelligently guide the user to get content from nodes of the same operator or similar networks, ensuring efficient and smooth data transmission, breaking the cross-network bottleneck, and allowing every user to enjoy smooth and unimpeded network services, greatly improving service quality and user satisfaction.

How CDNs work

Request Distribution: Precise Positioning, Fast Response

The moment you type a web address into the address bar of your browser and press the Enter key, a wonderful “Internet relay race” begins. First, your request will be sent to the DNS (Domain Name System) server like an expedited letter. DNS is like the “navigator” of the Internet world, whose task is to analyze the domain name into the corresponding IP address, and find the server that can provide services for you. With the support of CDN, DNS will accurately match you with the nearest CDN node with optimal network conditions through intelligent algorithms that take into account your geographic location, network operator, server load, and many other factors. This node is like the nearest courier station to your home, ready to serve you. Once the node is identified, your request will be delivered quickly. The node server receives the request and processes it according to pre-configured rules. If it happens to have the content you need in the cache, it's a “no brainer” and it will immediately package the content and return it to your browser as quickly as possible so that the page is instantly rendered. If you don't find the content you need in the cache, don't worry, the node server will immediately act as an “errand boy” and send a request to the source server to pull the latest content. After obtaining the content, it will not only deliver the content to you at the first time, but also thoughtfully store the “freshly baked” content in the cache, so that other users can quickly respond to subsequent visits. In this way, through the CDN's intelligent request distribution mechanism, the path of data transmission is greatly shortened, so that you can enjoy the feeling of “flying” every time you surf the Internet.

Load Balancing: Reasonable Distribution, Stable as Mt.

In the busy “traffic” of the network, CDN's load balancing technology plays a crucial role as a “traffic cop”. When a large number of users launch requests to the website at the same time, if there is no reasonable scheduling, it is easy to appear part of the server is crowded, while some servers are idle “traffic jam” situation. CDN's load balancing system is like an experienced traffic police, which always monitors the “road conditions” of each server. It constantly monitors the “road conditions” of each server, that is, the load situation. Its core principle is to distribute a large number of requests from users to multiple servers according to preset algorithms and rules, ensuring that each server can “do its job” and avoiding overload at a single point.

Specifically, it contains a variety of subtle functions: first is the traffic distribution function, it will be based on the performance of the server, the current number of connections, response time and other indicators, dynamically adjust the request traffic allocated to each server, just like the traffic police according to the width of the road, the size of the traffic flow to direct the vehicles to divert, so that the entire network to run in a well-organized manner.

The second is the health check function. The load balancer sends “health inquiries” to the servers on a regular basis, and once a server is found to be faulty or slow in responding, it immediately directs subsequent requests to other normal servers to guarantee the continuity of the service, and never let the individual server's “glitches “ affects the user experience.

Furthermore, the failover function, when the server cluster in a certain region encounters unexpected failures, such as power outages, network interruptions, etc., the load balancing system can quickly respond to the original request sent to the region seamlessly switched to the servers in other available regions, the entire process is almost unnoticeable to the user, just as flights encountered inclement weather temporarily landed in other airports, the travelers can still arrive at their destinations smoothly. Through these powerful functions, CDN load balancing system protects the stable operation of network services, so that you can enjoy smooth and fluid services whenever you surf the Internet.

Content Caching: Intelligent Storage, Fetch as You Go

CDN's content caching is called a “secret weapon” to improve user experience. Imagine, you often visit the web page has some fixed and unchanging pictures, style sheets, script files, etc. If every time you visit, you have to re-download from the distant source station, it would be time-consuming and labor-intensive. edge node servers of CDNs are like “intelligent storage cabinets”, which cache these commonly used and static contents. When you access the same content again, directly from the local “storage cabinet” out, instantly in front of you, the speed, is not faster than you go to the supermarket to get a bottle of water? Moreover, this caching strategy also has a big advantage, that is, it greatly reduces the burden of the source station server. The source station does not have to deal with these repeated requests, can put more “energy” into dealing with those personalized, dynamic data, so that the entire network service more efficient and stable. However, you may be worried that the cached content will not be out of date? Don't worry, CDNs take this into account. The content in the cache is equipped with a “shelf life”, or expiration time. Once this time is exceeded, the CDN will automatically determine whether it needs to re-fetch the latest version from the source, ensuring that you always see the freshest, most accurate content. At the same time, the CDN will also update the cache based on a series of intelligent strategies, such as time-based regular updates, according to the access heat of the content (the greater the number of visits, the more frequent the update), the source station content active push, etc., so that the cache is always kept “energized”, ready to provide you with quality services.

Back to the source strategy: targeted, optimized flow

Back to the source strategy, simply put, is when the user requests content in the CDN cache can not be found, the CDN node how to get content to the source station of a series of rules. This is a technical task, and different strategies have a direct impact on the performance of the CDN and the pressure on the source. Commonly, there are two types of back-to-source strategies: full back-to-source and partial back-to-source. A full repo is like going to the supermarket and purchasing all the ingredients again when the refrigerator is empty. When a user requests any uncached content, the CDN node will launch a request to the source to pull the complete and up-to-date content. Although this strategy can ensure the absolute freshness of the data, but in the peak traffic period, may bring more pressure to the source station, as if the supermarket checkout overcrowded. Part of the back to the source is relatively flexible, it is like targeted procurement, only to obtain the user's current request for a specific part of the content, or according to the content of the updated logo, selectively pulling the source station in the part of the change, not only to meet the user's needs, but also to reduce the burden of the source station, to avoid unnecessary traffic consumption. In addition, CDNs will also cache content that may be used to nodes in advance through intelligent cache warm-up and prefetching strategies to further reduce the occurrence of back-to-source requests. At the same time, CDN vendors will also tailor the most appropriate return strategy for customers based on the content characteristics of the source station, business needs and network conditions, and optimize every bit of bandwidth to ensure efficient and smooth collaboration between the CDN and the source station, so that users can enjoy high-quality network services while saving costs for enterprises.