CDN Performance Monitoring: Improving Content Delivery

February 6, 2024
Ann Oliver

With businesses now keeping faster content delivery and seamless knowledge sharing at the forefront, the adoption of Content Delivery Networks (CDN) is burgeoning. 

Case in point: Around 4,148 of the top 100,000 websites today deliver their content to the end users through CDN, which is more than 41% of the total websites, according to The Insight Partners

However, as CDNs have become more sophisticated and global in scale, monitoring and optimizing their performance has become critical to ensure efficient and quick content delivery to users. 

In this article, we will have a complete breakdown of CDN performance monitoring.

What is a CDN?

A CDN is a network of geographically distributed servers and data centers where static content (sometimes dynamic), such as images, CSS scripts, videos, etc., are stored and cached. So, instead of the origin server, these edge servers, scattered across the globe, send users the cached version of website content. 

While addressing a user's content request, a CDN uses the edge server nearest to that user. It means, leveraging a CDN to cache your website content for specific times means you now get the opportunity to decrease the distance between the CDN edge server serving your content and the end-users requesting this content. 

CDN servers also compress the size of the content and enable low latency and faster web page loading. The result is faster delivery of content and augmented viewing experience, which are driving businesses to leverage CDNs for delivering their content to users. 

This increasing adoption trend of CDN is causing the global CDN market to grow steadily, and the current positive progression is expected to be maintained until 2030.

The global CDN market is predicted to rise from $23.25 billion in 2023 to $105.55 billion by 2032, increasing at a CAGR of 3.7%.

CDN servers, being distributed throughout different locations across the globe, are required to perform optimal performance monitoring to ensure efficient service. 

The aim is to measure and evaluate the CDN's efficiency, reliability, and responsiveness. It enables optimal traffic distribution across edge servers, your websites are always up and running, and cyberattacks, like DDoS, are mitigated effectively. 

CDN performance Monitoring Metrics

 To ensure effective monitoring of CDN performance, the following key factors should be tracked:

  • Latency: When it comes to CDN performance monitoring, tracking latency and the response time of a website is critical.

    In the context of CDN, latency is the time delay it takes for a content request to hit a nearby edge server, and back to the requesting end-user. Latency plays a critical role in your CDN monitoring strategy, as it directly impacts a website loading speed.

    The lower the latency, the higher the load speed a website can attain. Monitoring latency enables CDN users to optimize server placement, pinpoint network bottlenecks, and decrease it wherever feasible.

    Factors that influence the latency include network traffic, distance between an end-user and the server delivering them the requested content, efficiency of routing protocols, etc. 
  • Cache Hit Ratio (CHR): Cache hit ratio is the measurement of how many content requests an edge server can address compared to the total number of requests it gets.

    CHR monitoring helps offload the origin server and optimize cache techniques, thus ultimately improving the performance. A high-performing CDN will have a high cache hit ratio.
  • Time to First Byte (TTFB): TTFB is another critical metric that impacts CDN performance. It denotes the time delay between a client requesting content and receiving the first byte of data.

    TTFB is impacted by a slew of factors - latency, response time, DNS resolution time, etc. The lower the TTFB, the more responsive the CDN server.
  • Throughput and Bandwidth: Throughput denotes the rate at which data is transferred between a user device and a caching server. It's an indication of how capable a CDN is in handling a specific load of network traffic.

    The higher the throughput, the faster the CDN is in serving numerous users. On the other hand, bandwidth refers to the data volume a CDN can handle in a specific timeframe. Higher bandwidth helps transfer a large volume of data in a shorter time, enabling faster content delivery.
  • Request Rate and Error Rate: Request rate is the number of content requests users send to the edge server in a specific period. The higher request rate indicates that the network is experiencing heavy traffic and increased website activity that may require resource scaling.

    On the other hand, the error rate is the percentage of content requests received by the caching server that results in error. Monitoring error rates helps businesses pinpoint and troubleshoot issues that may impede streamlined user experience.

Consequences of Not Having CDN Performance Monitoring in Place

Without robust CDN performance monitoring, you may face several issues:

  • Increased Mean-Time-to-Resolution: Having no CDN performance monitoring in place means that in the event of a performance issue, such as server overload, network congestion, etc., you have to investigate the causes and analyze it manually.

    Needless to mention, the manual approach of identifying bottlenecks is an arduous process that only prolongs the MTTR. The result is longer operational disruption, in some cases, downtimes, and dissatisfied customers. 
  • Poor Visibility to Performance Issues: Unless you regularly monitor your CDN's performance metrics, you cannot have real-time visibility into potential performance issues.

    It can result in delayed mitigation of anomalies that may cause operational disruptions. In addition, failing to have protective measures early in place and identifying the areas for improvements in your CDN infrastructure can negatively impact conversion rates, customer experience, and business ROI.  
  • Inefficient Resource Allocation: Without proper monitoring, you can't enable optimized resource allocation. Inefficient resource allocation results in wasted resources, piled-up operation costs, and over or underutilized server resources.

In short, efficient performance monitoring is critical to ensure improved webpage load time and streamlined content delivery. Now, let's go through some strategies that will help efficiently monitor CDN performance.

Tools for Effective CDN Performance Monitoring

Every expert engineer should get a hold of the following monitoring tools to ensure optimal CDN performance. 

Synthetic Monitoring

Proactive and continuous monitoring is critical to ensure potential incidents within a CDN infrastructure are identified before they cause operational disruptions or affect user experience. 

Synthetic monitoring helps operators improve CDN performance by collecting performance data instead of real user data. Such tools simulate user interactions and send requests to web applications or websites to reckon performance metrics.

With a synthetic monitoring tool, you can:

  • Track and analyze the aforementioned performance metrics, such as response time, availability, and latency.
  • Take a close eye on the last mile network (mapping end-users to PoPs) that helps verify if the CDN is performing optimally or not. Ensure end-users are being directed to the appropriate Point of Presence (PoP) of the CDN.
  • Monitor CDN performance across various types of devices, locations, and networks
  • Find areas that can be improved and optimize a website, web app, content, etc.
  • Evaluate content using A/B testing to understand the impact of any changes in it on end-users

Real-Time Data Analytics Tool

Real-time data analytics tools provide invaluable benefits for CDN performance optimization. Getting real-time insight and visibility into network parameters, such as throughput, traffic patterns, and server load, helps CDN operators make data-based decisions, optimize resource allocation based on traffic patterns, enhance caching strategies, and quickly track down and address performance bottlenecks. 

In addition, load imbalances across cache servers, that can cause performance degradation, can be easily identified and addressed by leveraging real-time analytics. 

Real User Monitoring (RUM)

Even though synthetic monitoring tools can offer insight into CDN performance, they sometimes fail to provide the actual user experience. 

This is where RUM comes into the scene. RUM helps decipher how optimally a CDN system is functioning by consolidating authentic data from visitors. It gathers and analyses data related to real user interactions with a website or web app. 

In addition, it leverages SDKs or Javascript to track key performance metrics such as server load, page loading speed, load time, error rates, etc. The aim is to help get a holistic view of customer experience. 

Some market-leading RUM tools that can optimise CDN performance from the end-user side include Google Analytics, App Dynamics, New Relics, etc. 

Multi-CDN Monitoring

Multi-CDN is an approach by large-scale businesses that leverages CDN services from multiple CDN vendors to deliver cached content to their end-users. For a website with a massive network load, using multi-CDN stands as a strategic imperative that, by redistributing loads among multiple providers, enables faster content delivery and more streamlined performance.

Multi-CDN, however, poses greater performance monitoring challenges to CDN operators and engineers. To ensure all CDN infrastructures are performing optimally, operators should deploy both synthetic and RUN tools along with API integration systems to get real-time visibility into each CDN provider. Thus, they can identify and address all bottlenecks promptly and efficiently. 

Anomaly Detection

Anomaly detection can help quickly detect performance issues that can impede optimal CDN performance. 

While traditional conventional threshold-based monitoring may sometimes fail to pinpoint minor issues, anomaly detection systems powered by machine learning can detect subtle issues that indicate underlying problems. Thus, proactive measures can be taken before these issues turn into escalating operational disruptions.  

Deploying anomaly detection systems can:

  • Automatically pinpoint abnormal patterns in traffic, performance metrics, and network.
  • Make the system auto-adapt to changing traffic and network patterns.
  • Reduce the likelihood of false alarms

Best Practices to Optimize CDN Performance

Check out the following tips and implement them as your CDN strategy to optimize its performance. 

Place Your Origin Near to Your Cache Server

While placing your origin server, make sure it's located where most of your visitors are from. For example, for a website that experiences traffic from mostly Asia, placing an origin server in America isn't viable at all. 

In this case, placing the origin server somewhere in Asia can help reduce latency between the CDN and origin server while simultaneously avoiding cache miss response. 

For websites that can't keep their origin server closer to the cache server, the most viable option is to use an Origin Shield. An Origin Shield is a cache layer that can optimize cache miss responses by speeding up content retrieval and offloading the origin server.

Use Online Tools

Another effective way to monitor how optimal a CDN's performance is to test it with high-end tools. You can either use the tools that come with your CDN service by default, or leverage third-party ones. 

Clearly Define KPIs

Make sure you define the Key Performance Indicators (KPIs) against your company goals and scope to ensure the CDN performance is tracked and optimized accurately. 

Use CDN Dashboard

Count on investing in a CDN that comes with interactive dashboards. These dashboards offer complete visibility in performance anomalies exerting the CDN's capability of enabling customizable, real-time alerts, tracking KPIs, etc. 

Analyze Server Logs

Enable periodic server log review using high-end log analysis tools to monitor your CDN performance. Server logs provide in-depth insight into user requests, CHR, response times, and server responses, helping boost CDN performance. 

Having this information at hand allows for faster identification and response to potential issues and troubleshooting of bottlenecks, ultimately leading to optimized performance. 

Conduct Load Testing

Conducting load testing simulating real-world scenarios is the most viable way to gauge a CDN's performance under different traffic loads. It helps better understand a CDN's capacity limitations and allows for smooth and faster content delivery during sudden spikes by enabling businesses to configure their CDN setting based on load.

Ann Oliver
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