How Does Using a CDN Affect Performance and Content Access Speed?!

One of the most important advantages of a Content Delivery Network (CDN) is its ability to deliver content quickly and efficiently. CDN performance improvements can be divided into three categories. Explore the Content Delivery Network guide.

How Does a Content Delivery Network (CDN) Improve Load Times?

A Content Delivery Network (CDN) provides significant benefits to the entire internet. Most technology companies, including companies like Google, Apple, and Microsoft, use content delivery networks to reduce loading latency in web page content.

A content delivery network typically places servers at exchange points between different networks. These points (IXPs) are the primary locations where different internet service providers connect with each other to provide access to resources on their respective networks. In addition, the content delivery network places servers in data centers at various locations around the world in high-traffic areas and strategic locations to enable moving traffic as quickly as possible.

A content delivery network excels at delivering content quickly and efficiently. CDN performance improvements can be divided into three categories:

Distance Reduction – Reducing the physical distance between the client and the requested data.
Hardware/Software Improvements – Improving server infrastructure performance, such as using solid-state drives and improving load balancing.
Data Transfer Reduction – Using techniques to reduce file sizes so that initial page loads happen quickly.

To understand the benefits of using a content delivery network, let us explore what data transfer between a client and server looks like normally without a content delivery network.

The Difference in Load Times Between Using a CDN and Not Using One

Regarding the difference in load times between using a CDN and not using one, let us imagine that someone in New York needs to access a website hosted on a server in Singapore. The geographical gap between these locations is large, with a physical distance of approximately 9,520 miles.

Without using a CDN, the data would have to travel this long distance between New York and Singapore to reach the user. This can cause a significant delay in page loading due to the time required for data to travel across this large distance.

On the other hand, when using a CDN, copies of the content are served from servers distributed in different regions of the world, including New York and Singapore. When the user in New York tries to access the site, the content will be loaded from a geographically nearby server, which significantly reduces the page load waiting time.

In summary, using a content delivery network can significantly reduce load times when there is a large geographical gap between the user and the data hosting location.

If the server hosting the website content (the origin server) is located in Singapore, then every request for every web page element must travel from New York to Singapore and back again. This process resembles international air travel with many connections along the way, where every request must travel through a chain of routers over the long journey from point A to point B.

If you want to see a real-world example of the number of different connections (hops) that your computer needs to reach a specific web service from your current location, try using the Traceroute tool on your desktop computer.

What Happened?!

Because the request from New York to Singapore needs to pass through all the router locations along the way, the amount of time (latency) is increased through the total distance and the time each router takes to process the request. Once the origin server processes the request and responds to the requesting client, it then sends the information back through a similar chain of routers before returning to New York. This round-trip measurement is referred to as RTT for "Round-Trip Time" in the field of communications. Let us, temporarily, ignore available bandwidth and the possibility of network congestion, and look at an example of latency factors.

For illustration purposes, let us assume:

It takes 250 milliseconds for the request to travel from New York to Singapore.
Establishing a TCP/IP connection will add 3 instances of 250-millisecond latency.
The web page requires 5 unique elements consisting of images, JavaScript files, and the page itself.

Let us see approximately how long it will take to load this page:

750 milliseconds: A TCP/IP connection is established between the client in New York and the origin server in Singapore.
250 milliseconds: The HTTP request for the page travels from New York to Singapore.
250 milliseconds: The requester in New York receives a response from the origin server in Singapore with status code 200 and the page including all the additional elements needed.
250 milliseconds: Each of the 5 elements is requested by the client in New York.
1500 milliseconds: The five elements are delivered asynchronously to the client from the origin server in Singapore.

In this simple example, the total transit time for this page to load is approximately 3000 milliseconds.

As you can see, every time a request is sent and a response is received, the entire path between the client in New York and the origin site in Singapore is traversed. As websites grow in size and require a greater number of elements, the latency between point A and point B continues to increase.

Let us revisit the example of content hosted in Singapore being served to a web client in New York, but this time the Singapore site uses a content delivery network (CDN) with a server in Atlanta that contains a cached copy of the static site:

It takes 50 milliseconds for the request to travel from New York to Atlanta.
Establishing a TCP/IP connection will add 3 instances of 50-millisecond latency.
The page requires 5 unique elements consisting of images, JavaScript files, and the page itself.
Let us see approximately how long this site will take to load using the content delivery network:

150 milliseconds: A TCP/IP connection is established between the client in New York and the edge server in Atlanta.
50 milliseconds: The HTTP GET request for the page travels from the client to the edge server.
50 milliseconds: The client receives a response from the edge server cache with the page including a list of all the additional elements now required.
50 milliseconds: Each of the 5 elements is requested by the client.
800 milliseconds: The five elements are delivered asynchronously to the client from the edge server.
The total transit time for this page to load is approximately 1100 milliseconds.

In this example, reducing the distance between the client and the content results in an improvement of 1900 milliseconds in latency for static content, representing an improvement of approximately 2 seconds in load time.

By reducing the total distance that all necessary traffic must traverse, every site visitor saves some amount of load time. Since users begin leaving the site (bouncing) very quickly as waiting times increase, this improvement represents a better user experience and a longer time for the user on the page.

How Does CDN Work and Its Method of Loading Content

How Does a Content Delivery Network (CDN) Load Content? What Is Caching?

As mentioned earlier, when a file is requested from the origin server, the request typically needs to travel to that server and back. A CDN improves latency by pulling static content files from the origin server into the distributed CDN network in a process known as caching. Some CDN networks have advanced features that allow selective caching of dynamic content as well. Once the data is cached, the CDN serves the content to the client from the nearest CDN data center.

After completing the TCP handshake, the client device sends an HTTP request to the CDN. If the content has not been cached yet, the CDN will first download the content from the origin by making an additional request between the origin server and the CDN edge server.

Here are the four steps during a typical CDN caching process:

When a user requests a web page, the user's request is routed to the nearest CDN edge server.
The edge server then sends a request to the origin server to obtain the content the user requested.
The origin responds to the edge server's request.
Finally, the edge server responds to the client.

The value of a CDN being closer to the client occurs after the first request to the origin server has already been made. Once the data from the origin server has been cached on the CDN, every subsequent request from the client only needs to travel as far as the nearest edge server. This means that if the nearest edge server is closer than the origin server, latency can be reduced and content can be delivered more quickly.

It is important to keep in mind that the amount of time required to load assets and process requests and responses has not been included yet; so far only the time required to transfer information between these two locations has been calculated. Other important latency factors we will be exploring include data reduction, hard disk speed, and network congestion.

How Does CDN Speed Up Access?

How Does a Content Delivery Network (CDN) Reduce File Sizes to Increase Speed?
In order to improve page load times, CDNs reduce the total amount of data transfer between their caching servers and the client. Both latency and the required bandwidth are reduced when the total amount of data transferred decreases. The result is faster page loading and lower bandwidth costs. Two main elements go into this reduction:

Minification – This is the process of reducing the size of code blocks by removing all elements that help humans understand what is happening. While an engineer needs to break ideas down into logical variable names, spaces, and comments to make code blocks readable and maintainable, the computer can run the code successfully after those characters are removed.

Now that the code snippet has been reduced from eight lines to one line, the overall file size has also been reduced. This means it takes less time to transfer the file, which reduces latency and helps content load faster.

File Compression – File compression is a key component in reducing latency and bandwidth consumption required when transferring data over the internet. GZip is a common compression method and is considered a best practice to use when transferring web pages. Many CDN providers have GZip enabled by default. How large are the savings from GZip compression? In general, compressed files are reduced by 50% to 70% of the original file size.

Also

Regarding CDN hardware improvements, a major benefit comes from using Solid-State Drives (SSD) instead of traditional Hard Disk Drives (HDD); SSDs can open files up to 30% faster than traditional hard drives and are more durable and reliable.

Similar to a record player, a traditional hard disk drive consists of a circular metal disk that spins with a magnetic layer that stores data. The read/write head on an arm accesses the information as the disk spins beneath it. This process is mechanical and is affected by the speed of the disk's rotation. With the emergence of solid-state drives, the use of the old model of hard disk drives has become less common, although they are still produced today and are widely used in many computer systems.

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How Does Using a CDN Affect Performance and Content Delivery Speed?

How Does Using a CDN Affect Performance and Content Access Speed?!