Content delivery networks (CDNs) are global networks of caching (edge) servers that deliver content efficiently to users.
As CDNs cache content close to end users, they reduce latency, thereby speeding up website, application, and download load times. Boosting customer loyalty and brand trust, as well as improving SEO, are also benefits of this accelerated delivery.
Furthermore, a properly configured CDN mitigates DDoS attacks - by dispersing fake traffic across servers worldwide, a spike in fake traffic will not overwhelm the website.
How Do CDNs Solve Challenges?
Regardless of your comfort level when it comes to technology, two significant challenges that CDNs solve are easily understood:
- An application's or website's performance. Keeping latency to a minimum is the goal here. You may be able to increase user experience and audience loyalty by reducing the distance between your website's hosting environment and where your website's visitors can access your content.
- An application or website is available. When faced with surges - such as sales events, game patches, or DDoS attacks - we want our websites to respond as quickly as possible. The use of distributed servers increases accessibility of our website and app content while reducing vulnerabilities to malicious actors.
Here are some details to dig deeper into.
Performance of the website
Many factors influence the performance of a website or app, including DNS settings, host server settings, and code quality. One aspect, however, cannot be changed: the distance between your web server and your users' location. Getting content to users in Barcelona differs from sending it to Boston visitors, no matter how well you optimize configuration at the web server city-let's say it's located in Berlin.
Content delivery networks are powerful tools. It is important to reduce the transfer time of all website content, including static assets (.css, .html, .jpg, etc.) as well as dynamic assets (data generated dynamically based on user behavior and interaction, or API calls, for example).
Bringing static content (and dynamic content) closer to the user will improve the performance of your website or application significantly.
The availability of the website
First, we can examine how CDNs protect websites and applications from DDoS attacks, and the considerable value they bring to businesses, especially those operating in global markets.
In recent years, DDoS attacks have become more common, and their frequency continues to increase.
- Maintaining on-premise anti-DDoS solutions is both expensive and difficult.
- As CDN servers are distributed across continents, they provide extensive bandwidth for your web server, which can help prevent DDoS attacks. Several CDNs employ additional security and filtering mechanisms that enhance anti-DDoS protection.
- CDNs also prevent overburdened web servers (origin servers). If the origin server cannot handle more client requests than it can handle, the website or application may not be accessible. The origin server has limited compute resources and bandwidth.
In caching (edge) servers, network resources are saved at the origin server by reducing bandwidth consumption.
Additional challenges that CDNs help solve
Traffic encryption: Privacy is paramount, and securely encrypting the transmission of data is essential. Using SSL/TLS encryption assists with security and upholds the integrity of communications. A CDN can encrypt traffic when it passes through edge servers, which is all the more important should your website not have an SSL certificate of its own.
Application security: CDNs can be outfitted with a WAF (web application firewall). This tool is specifically geared to safeguard applications from vulnerabilities, a proactive filter designed to block attacks and common exploits.
Access orchestration: The use of a CDN facilitates another layer of control—you can decide when to grant or deny access to the content of a website or application.
Load balancing: If you are using multiple origin servers, a CDN can operate as a load balancing tool, efficiently distributing incoming requests. This is an effective way to handle traffic congestion and keep content reliably online, all while optimizing server capacity.
CDN: How Do They Work?
CDNs cache content on servers distributed globally. Static assets are retrieved from your website's origin server by the content delivery network when a user requests them for the first time. As a result, the CDN places a copy of these assets in the nearest edge server to the user, caching them for later access.
Having data cached at the edge of the network reduces the distance for communication to travel, making your website content more readily accessible to your visitors in the future. Due to the CDN, the origin server does not have to process the same static requests, resulting in a reduction in latency.
As a result of caching data and spreading multiple requests for the same content across a distributed network, the traffic load becomes more evenly balanced, and delivery becomes more uniform and efficient.
A CDN allows end users to access your website's content from any server in the network, which is the takeaway for business owners. If the closest server is unavailable, communications will be rerouted through another server to keep your website's pages available. This infrastructure ensures uninterrupted uptime for business-oriented websites, which is a crucial requirement.
CDN Components: What Are They?
Our discussion of CDNs and the challenges it seeks to solve has so far focused on reducing latency, ensuring responsiveness and availability of websites and applications, and improving website security. The caching of content across a globally-distributed network is a network "at work," doing what it is designed to do.
In this section, we will examine the design of a content delivery network, the components that make up the CDN, and the roles they play within the CDN's overall concept.
Three entities are involved here: the origin server (you, the client with the hosted website); the caching server (components that make caching and faster distribution possible); and the end users, those visitors who access your website or application through their devices and expect to have a smooth experience.
Keep in mind that two of these entities remain the same without a CDN: the origin server and the end user. As a CDN, we are enhancing the functionality of the former while providing the latter with the best possible experience.
Here are the three points of presence: the origin server, the caching server, and the points of presence.
What Is an Origin Server?
An origin server, like the name implies, is where the original version of your web files is located—the computer where your website is hosted.
If there isn’t a CDN in place, visitors to your website must request information and receive responses directly from your website’s primary source. This method of direct communication can pose considerable demands on the origin server. Specifically: (a) each request routed to your origin means the web server’s workload increases; and (b) the farther away an end user is from the origin, the longer that user will wait for pages to load.
Caching Servers: What Are They?
A content delivery network is incomplete without caching servers. The servers hold copies, or cached versions, of website content retrieved from the origin server, and deliver this stored content on demand. A caching server functions as a reverse proxy, acting as an intermediary between web servers and end users. These requests are intercepted by reverse proxies, forwarded to web servers, and then returned to the site's visitors as responses.
There are physical data centers spread out across the world that host these servers (see below).
Here, caching happens at two levels:
As part of a CDN, edge servers are responsible for performing the first level of caching, among other duties. As close to the end-user as possible, the edge servers reduce round-trip time between end users and the origin servers.
It can be very advantageous for website owners to resolve user requests at the network edge. With edge servers that are physically closer to your site's visitors, you can offer your site's visitors cached content, resulting in a double benefit: faster load times for end users who expect content, which improves customer loyalty, and a reduced workload demand on the origin server, resulting in better uptime reliability and consistency. In times of pronounced traffic surges or sudden spikes, these advantages can be especially useful.
Additionally, edge servers may serve as carriers for additional functionality, such as performing certain computations as a unit for edge computing.
Points of presence (PoP): What Are They?
The term "points of presence" describes the geographical coverage and locations of the network. It is usually the data center hosting the caching (edge or shielding) servers that is considered the point of presence. CDNs are composed of thousands of PoPs distributed around the world.
As a way to describe the extent of your CDN coverage, the term "PoP" can also be used synonymously with "edge servers."
Additional benefits of an effective CDN
Alongside the larger, overarching mission that a CDN is tasked with—minimizing latency and reducing bandwidth consumption, increasing website availability performance, improving and ensuring security across all aspects of the network—there exists other capabilities that website owners can benefit from. Let’s take a quick look.
- Dynamic content acceleration: Dynamically generated assets—content where the information is dependent upon users’ requests—and API calls could have a shorter latency when employing a CDN, since TLS handshaking is established with the edge servers located close to the users awaiting that content, not with the origin.
- File compression: Compressed data travels faster than uncompressed data. The two most widely-used algorithms for compression, Gzip and Brotli, have their own distinct attributes (the former is older, and was initially created to compress files; the latter was designed specifically to compress streams of data for the web). But the bottom line translates to clear value: CDNs harnessing file compression capabilities means reducing the size of data being transmitted, which reduces traffic costs and increases website speed.
- Image optimization: Image formats like WebP and AVIF have functionalities tied to the benefits of compression listed above, as optimizing images helps what is likely a large part of your website’s content get effectively cropped and quickly resized for fast loading on users’ devices. This speed is only enhanced by harnessing the power of a CDN—aside from the user experience benefits your visitors will appreciate, it can also boost your site’s SEO rankings.
- Optimized video streaming: Just as the shift toward mobile is becoming more prevalent, perhaps dominant, with respect to how users access content, so too is the need for website and app owners to ensure they have video available on demand, 24/7 and uninterrupted. Using low latency and ultra-low latency streaming protocols helps provide the best possible user experience. This is especially applicable for businesses focused on broadcasting media or online entertainment, for example, as these sectors benefit from a CDN’s ability to deliver consistent regional coverage, and do so with increased resiliency.
Use Cases of the CDN
Having outlined content delivery networks, their purposes, and how they work, let's conclude with some examples of use cases.
There will be a certain amount of overlap from the info we detailed above, as the challenges CDNs face and the benefits they provide (and how they deliver them) have been discussed in some detail. We've described a lot of value because it applies to real-world situations, but let's take a moment to illustrate how certain industries can leverage CDNs to meet their specific business needs.
Downloads and Updates
An appropriate example here is the gaming industry. Games played via a website or an app can have massive—and massively loyal—audiences, provided everything about the company’s CDN infrastructure runs smoothly. Millions of players are relying on its stability, and the performance that the network delivers. The absolute last thing these companies would want their users to experience is unbearably long download times when online gaming across certain regions of the globe is at its peak—or the day that a much-anticipated update is finally released.
Video Streaming
This scenario is easy to visualize. A broadcast media company or provider delivering video for popular sporting events already depends on solid infrastructure; however, during exceptionally high demand—say, the semi-finals of the World Cup, and in at least four countries every device in the country is counting on optimized, real-time streaming—a broadcast service provider operating in those countries will count on their CDN vendor to balance loads and intelligently route content delivery.
The CDN is tasked with optimizing distribution across its points of presence to ensure live streaming continues without interruption—no goal is missed, so to speak.
Website acceleration
This is also an easy one to picture if we take e-commerce as an example. Everyone has had the frustrating experience waiting for, or being let down by, an inefficient website while simply trying to pay for something. E-commerce is huge, and m-commerce, the “sub-category” of purchasing via mobile, is exploding in its own right. Websites and apps that display products or services for sale, and conduct financial transactions for those sales, should aim for the most accelerated webpage loading time possible.
The value a CDN brings to the table is crystal clear—communication distance is shortened. For an e-commerce company this is transactional in several ways: the faster a page from your website loads (reduced latency), the lower your bounce rate, the higher the conversion rate, and the more your brand trust grows amongst satisfied customers.
In Summary
By using a CDN, websites can reliably distribute content hosted on their servers worldwide and to clients' devices, the end users. Many client requests are fulfilled close to clients' locations by its interconnected network of caching servers.
Through edge servers deployed closer to end users instead of the origin, page loading times are shortened, leading to happy clients with positive user experiences.
In addition, CDN infrastructure is designed to keep site performance optimized and latency at a minimum. An effective CDN can mitigate traffic surges, mitigate DDoS attacks and mitigate surges in traffic as well.
It accelerates static and dynamic content of your websites or applications using AgileCDN's technology. With 2800+ points of presence around the world, our CDN has many built-in web security features.