The Importance Of CDN Selection To Achieve Broadcast-Grade Streaming Experiences - Part 2

CDN Selection is a pivotal point in the streaming delivery chain that makes an important difference to the success of a D2C Streamer.

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Performance and cost results both depend on how the CDN Selector performs. Leading Technology providers are working on optimisations required by the leading D2C Streamers, to push the performance of CDN selection to the next level.

Managing Public And Private CDNs

D2C Streamers are increasingly investing in their own private CDN platforms, dedicated to their own content delivery. CDN Selection solutions may measure each platform in the same way but they should be able to allocate content to each CDN environment using different methods. For example, a private CDN should bring cost and performance benefits that need to be maximised. So, it should have the majority of traffic allocated to it unless there are problems. CDN Selection solutions that initially select using the percentage-based business rule are not ready to support this requirement.

Per Segment Delivery

A recent development in leading CDN Selection solutions is to enable CDN selection on a per video segment basis. A plug-in component at the player determines which CDN to retrieve each segment from based on a range of real-time measurements provided by the client-side analytics. Policies can be set that limit the ability to retrieve from a CDN that is not desirable for the D2C Streamer, if there are performance or business constraints. This low level of granularity will provide D2C Streamers even more methods in the future for optimising their content delivery.

NPAW’s CDN Balancer Business Unit Head, Luis Lopez Chousa states “The per segment approach takes CDN selection capabilities to a new level that could transform streaming performance for the largest audiences. D2C Streamers will be able to know that they are doing everything possible to extract the best performance from their delivery platforms, which is particularly important during the biggest events when the pressure to perform is at its highest.”

Figure 1: Active Switching using Per Segment CDN Selection.

Figure 1: Active Switching using Per Segment CDN Selection.


Completing the CDN selection process is the reporting on decisions made and their results. Leading solutions allow for deep drill-down into session-level data which enables analysts to dissect performance and establish appropriate improvement plans. Real-time alerts of under-performing CDNs or content types can be provided and are connected back to the analytics reports. This feedback loop ensures continuous improvement is embedded in day-to-day CDN selection decisions.


The D2C Streamers taking this subject most seriously are seeing important performance improvements. Jose Jesus, Director of Product for Experience Insights Suite at Conviva, states “Our published reports over the last 7 or 8 years show that the industry has moved from looking at average rebuffering ratio, or the percentage of sessions with less than 2% rebuffering ratio, to measure how many sessions have zero rebuffering, as this represents a proper TV experience. Benchmark rebuffering ratio in Europe and North America, for example, has dropped from 1% to less than 0.1% over the last 7 years because best-in-class D2C Streamers are continuously measuring performance and making improvements.”

Technology Developments

The general technology drive in CDN Selection is for more data, more real-time analytics, and more detail in decision-making. Additionally, some very specific areas are being researched and developed to support D2C Streamers’ future needs.

  • Internet control planes – to prevent risking an overload of a CDN, leading to performance degradation, customer dissatisfaction, and CDN switching, the CDN Selector must know when a CDN is full. This requires some form of control plane for CDN capacity decision-making. The following Streamer Requirements section explains this further.
  • Deep Edge deployments – improving performance most often involves tuning how the players manage the video and working with CDNs to fine-tune capacity availability and locations. The placement of Edge Caching capacity nearer to consumers is a major trend that will ultimately help all D2C Streamers to scale their businesses.
  • Multiple delivery sources – the Per Segment Delivery approach previously mentioned can be extended to incorporate other delivery sources, like WebRTC or Peer to Peer. This could mean that specific segments could be downloaded from a non-CDN source, like a peer, potentially reducing costs and latency for the D2C Streamer.
Streamer Requirements

Advanced D2C Streamers, pushing the boundaries and requiring the very best solutions, describe three specific areas of requirement for their future CDN selection solutions.

First, business rule configuration is a must-have. Solutions that focus on technical selection criteria and do not include the ability to use finely tuned business rules are too simplistic. Fine tuning involves, for example, delivering lower value content on a lower cost / lower performance CDN, while higher value content should use the highest performing CDN. Given that CDNs can differ in each country in terms of features, performance, and price, it is important to use their services intelligently to drive best cost.

Second, the CDN Selector is the initial point of the stream delivery before streams spread out inside the CDNs. The CDN Selector is aware of exactly what type of device/consumer a stream is to be delivered to – for example, mobile vs. SmartTV, or a standard vs. premium customer. Therefore, it should be possible to manipulate the manifest at this point. With this functionality, the right number of users can be sent to specific CDNs with capabilities that best match the delivery requirement.

Third, data integration from 3rd party systems is critical. A prime example is the private CDN platform that D2C Streamers can have very deep insight into, such as capacity availability by server, and the ability to control the amount of available capacity at each PoP. The requirement is to bring that data into the CDN Selection tools. Today, a lot of CDN Selection functionality requires installing an App plug-in which requires opening the App and inserting the data, and time and cost to integrate. It would be more efficient to bring data from the CDN into the CDN Selector that can be used to drive more granular capacity allocation. The basic rule of streaming performance at a CDN level is that the best performance is achieved when the right capacity is available. Pinpointing the right capacity in real-time would be a major benefit to the D2C Streamers.

As Vincenzo Roggio, Head of Distribution at DAZN, states “In our large-scale live event streaming delivery, traffic is spiky. It starts, reaches a high peak, and then stops, many times per day. We need to know exactly how our CDN capacity is performing, and we need to know that during a 2-hour game we are getting optimal decision-making from our tools that help our CDNs to perform their best. We know this leads to the best QoE for our customers, which is business-critical for us. We have a multi-CDN environment and look for every way to continuously improve the performance and efficiency of our content delivery operations.”


CDN Selection has a big role to play in delivering broadcast-grade experiences for streaming viewers. It supports D2C Streamer operations to optimise their CDN performance and cost, both of which are critical to their success as streaming grows.

The leading solutions are laser-focused on improving streaming performance through excellent use of data that delivers clear insights, actionable information, and a continuous improvement capability.

We can see that the streaming world is improving in every respect. Devices are better, encoding standards are sharper, networks are better. But, there is always the chance of encountering network congestion. To protect against this impacting stream performance or cost, analytics must be granular, and CDN selection must be dynamic.

In the end, whether a viewer receives their broadcast-grade streaming experience or not relies heavily on which CDN is selected.

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