Edge Computing is So Fun Part 5. CDN Is The Magic Inside Disney’s Streaming Services

Disney’s streaming platform has become a top competitor in an already crowded field. Credit: Scott McIntyre for The New York Times

Disney+ has skyrocketed to over 100 million subscribers in just 16 months since its launch in November 2019 as user growth exponentially over the course of the pandemic. See Figure 1 (Feb 12, 2021.) It also tops Disney’s original projections of getting to 90 million subscribers for Disney+ within four years. This is a very impressive feat. But what people overlooked was the infrastructure behind it to support the huge spike in subscribers. 

Figure 1. Disney+ Passes 90M Subscribers Three Years Ahead of Schedule

How did Disney do it? Content Delivery Network (CDN) is the magic behind Disney’s Streaming services. Disney+ doesn’t own any delivery infrastructure, they use third-party CDNs. To support the huge surge in subscribers, Disney+ relies on CDN providers such as Akamai, Lumen, Limelight, Edgecast, CloudFront and Fastly for its video content distribution. 

What is Content delivery network? Let’s start with why we need CDN in the first place. Data takes time to travel. Even with optical fiber, it still takes about 160 milliseconds to make the round-trip from New York to Sydney. Just imagine if we have thousands of users in Sydney trying to watch the same movie at the same time and the movie is located on a server in New York. It is going to take a long time.

There is physical limitation on how fast data can travel but we can store the contents on servers closer to the users. Like the real estate business, CDN is about location. By placing the contents in a geographically distributed network of content-caching servers, the delay in content delivery is significantly reduced.

This is how it works. Content providers such as Disney+ provide their contents to their CDN providers to host. The CDN providers copy the contents to a group of servers located in different countries and different Internet Service Provider (ISP) networks, as shown in Figure. 2.

Figure 2. Content is placed closer to the user by employing the servers of the CDN provider than possible using the server of the original content provider. Source: Computing in Communication Networks

Instead of the original content provider, the requests for these contents will go to a local server closest to the users. By keeping the content items in local storage, these edge servers provide a dedicated cache for the original contents. With streaming services such as Disney+, end users can use their media players to start playing the video without having to download the entire video using what we called video streaming.

Video streaming allows the user to download video content while watching it. With streaming, the media player plays the video without actually copying and saving it. Once the video stream from the CDN hits the media player at the end user, the player buffers the stream for few seconds to deliver a smooth playback experience. Please see Figure 3. If a video file is downloaded instead, a copy of the entire file is saved onto a device’s hard drive, and the video cannot play until the entire file is downloaded. 

Thanks to the rapid adoption of 4K UHD TV, the demand for 4K video streaming is growing exponentially. According to Cisco’s VNI Global IP Traffic Forecast, 62% of the connected flat panel TVs will support 4K by 2022. See Figure 4. UHD quality video uses a lot of data. A 4K stream uses about 7.2GB per hour. 

Figure 4. VNI Global IP Traffic Forecast, 2017–2022. Source: Cisco 

As the amount of data increased exponentially, the demand for more powerful CDN has also gone up exponentially. New contents are being created and consumed by more users on more devices in more places. Customer demands are also growing rapidly, creating new opportunities for service providers to deliver compelling experiences wherever customers are consuming or interacting with content. This is driving service providers to adopt new technologies to accelerate CDN development.

CDN providers have to be able to detect spikes in traffic and respond dynamically to support the demand. However, building just for peaks is an expensive proposition. Instead of just adding more CDN servers to support the surge in traffic, service providers need a CDN server architecture that can scale. For CDN servers, CPU, memory, I/O capacity, and network bandwidth are key to reducing service time. With the Speed Select Technology on the Intel® Xeon® Scalable processor, it allows switching between different CPU configurations and requires no hardware or software changes to scale the CPUs to meet performance needs on demand. Service providers can scale up to higher performance CPU configuration when the demand is high and scale back down when the demand is low.

Figure 5. Example of a CDN server -Supermicro 1029P-N32R. Credit: Supermicro.

With more and more people viewing content with their mobile devices, coupled with the growth of real-time content, service providers also need greater memory capacity at the network edge to speed up the delivery of content. Memory is used to store the more frequently-used contents. The greater the memory capacity, the better it is. But large memory system is costly. However, with the Intel Optane DC Persistent Memory, it will provide greater memory capacity and improvement in throughput at a much lower cost than DRAM memory. See Figure 6. With a CPU that is scalable and the added memory capacity, service providers can support spike in demand and improve efficiency without adding more CDN servers.

Figure 6. Intel Optane DC Persistent Memory provides higher throughtput and more memory capacity at a lower cost.

There are many use cases for CDN, but the biggest driver of growth for the CDN market has been, and will likely continue to be, the increasing demand for video over the internet. Distributing video contents over the internet is an extremely complex subject and no trivial task. Without the CDN infrastructure, Disney+’s 100 million subscribers will not be able to enjoy the movies at home during the pandemic. With the advent of 5G, the migration to 8K video, and the proliferation of rich media files, it is going to get even more challenging.