Why Is a CDN Critical for Live Streaming? (Update)
As the video streaming industry continues to expand, so too do demands on the servers that support it. Video content delivery networks (CDNs) have stepped up to better meet streaming demands and help streamers reach wider audiences. In fact, Cisco estimates that 72 percent of all internet traffic crosses a CDN – up from just 56 percent in 2017.
Put simply, CDNs make up the “web” in World Wide Web and the “net” in “internet”. These networks of interconnected servers deployed worldwide ensure speedy and high-quality access to everything online. Well, almost everything. If your streaming partner or infrastructure doesn’t employ the use of a CDN, then you could be lacking the necessary tools for sending high-quality streams to a wider audience – in other words, scalability.
For viral content and geographically dispersed audiences, CDNs are an essential workhorse for any streaming workflow. Beyond that, they help prevent slow video startup times, stream interruptions, and the dreaded spinning wheel of buffering. Finally, CDNs can provide flexible scalability and added stream security. Read on to learn more about how CDNs work and why video CDNs are critical for streaming.
Table of Contents
What Is a Content Delivery Network?
As the name suggests, a CDN – short for both content distribution network and content delivery network – is a system of geographically distributed servers (edge servers) used to transport media files from an origin server to end-user devices.
While a single server is capable of streaming to end-user devices, large audience sizes, disparate audiences, and higher quality streams could present too much strain and lead to traffic bottlenecks. The edge servers in a CDN help to share the processing burden with the origin server, making it easier to stream reliably to larger audiences across greater distances.
History Behind CDNs
CDNs have been around since the late-1990s, the first of which were specifically designed to address higher demands for audio and video streaming and are still responsible for 15-30 percent of internet traffic worldwide. These early CDNs were created to accelerate websites, support growing volumes of content, and reduce latency for video streaming. Over time, CDNs have evolved to become a crucial part of the internet infrastructure, and their popularity continues to grow with the rise of online video streaming.
Of course, it took a while to get here. It used to be that streaming content was delivered via dedicated servers using the Real-Time Messaging Protocol (RTMP). These streams had to be distributed on dedicated RTMP servers, making them resource heavy. They also had their fair share of buffering and caching challenges.
Thankfully, the industry transitioned to HTML5-based technologies in the 2010s. This helped combat buffering and improve caching in one fell swoop. However, it was the move to protocols like Apple HTTP Live Streaming (HLS) and Dynamic Adaptive Streaming over HTTP (MPEG-DASH) that really brought the power of CDNs to streaming. These new technologies could run on traditional HTTP web servers rather than dedicated RTMP servers, making them a more viable option. Today, CDNs are extremely common and a cost effective and reliable way to send large amounts of data across great distances.
How Does a CDN Work?
It’s easy to forget in the age of the internet that distance still matters, even for digital information. We’ve just gotten very good at making it seem like it doesn’t. Combine that with increased volume, and it’s not difficult to see how a single server might struggle to handle multiple streams to a wide audience. To better understand this, let’s look at another form of distribution.
Ever wondered how Amazon ships packages so quickly? There is no central warehouse that houses all of Amazon’s goods. Rather, they have fulfillment centers peppered across the globe. These fulfillment centers store goods as they come in from sellers, making the most popular goods more accessible. As such, if you order something from a seller four states away, you could get it as soon as tomorrow because it’s actually coming from a distribution center in your own city. If that distribution center doesn’t have what you’re looking for, it will request it from another just a little further away.
This is similar to how CDNs operate. Think of the origin server as Amazon’s headquarters, the edge servers as fulfillment centers, and the streamers as independent sellers. If the headquarters is solely responsible for storing, transcoding, and distributing media, then it’s going to take longer, especially across greater distances. The fulfillment centers are there to cast a wider net and share the load.
How Does a Video CDN Work?
When you request to view a stream, the closest edge server to you geographically will try to send it. Either it has the media files cached (stored) and ready to go or it requests the data from another nearby edge server. In this way, media is traveling shorter distances and no single server is overburdened with processing needs. After a stream is initiated from an edge server, the media files remain on that server, ready for another user in the same area.
Delivering video content with a CDN prevents buffering and stream crashes by placing copies of the media files close to viewers. Even for live broadcasts, this caching function makes a big difference. Cached segments from a live stream can drive the startup lag down to sub-five seconds. Plus, it significantly reduces the load on the origin server, thereby ensuring a more reliable viewing experience.
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Types of CDNs
It’s worth noting that while the general principal behind content delivery networks is the same, they can operate somewhat differently, depending on specific needs. From the perspective of a viewer or website visitor, there is functionally no difference between these CDN types. But from the perspective of a developer, choosing the right type of CDN matters.
A push CDN involves copying static files from a web server to a CDN. With push CDN publishing, the process of copying files is consistent and automated, a beneficial approach for websites that have largely static content, as the CDN caches the content locally for future needs and the demands of regularly updating the data are relatively low.
Origin Pull CDN
Origin pull CDNs request data from the origin server only when requested by a client (as opposed to the more automated push CDNs). Once information has been requested, it may be cached locally for future or additional requests. This method reduces demand on the origin server as information is only requested when needed (and when not already locally cached). This is the preferred method for video streaming purposes.
Peer to Peer CDN
A peer-to-peer (P2P) CDN, or PCDN, is a type of content delivery network in which resources are distributed from peer-to-peer networks instead of server-client networks. In PCDN, every peer on the network is both a client and a server, exchanging content with other peers in the network. In contrast to traditional server-client CDN architectures, PCDN can reduce the amount of bandwidth needed to deliver content, as peers can share files with each other rather than each peer having to download content from the origin server.
Who Uses a CDN?
As they were created specifically to improve internet access reliability and speed, just about everyone benefits from content delivery networks. Of course, they may not realize this. The CDN operates in the background, improving load times and providing a more stable online experience for anyone visiting a CDN-based website. As an end-user, you don’t need to worry about how the content is getting to you or whether a CDN is being utilized, but you do get to enjoy the smooth digital experience.
The question of CDN usage gets more complicated when you start talking about content creators and businesses. Individuals or organizations looking to stream content may or may not benefit from a CDN, depending on their streaming method. Popular streaming platforms like YouTube and Facebook Live use CDNs to distribute content. However, more complex or white labeled streaming solutions may not, unless you’ve explicitly incorporated them into your workflow. Building a streaming solution with a CDN requires a great deal of server infrastructure or a partnership with a streaming solution provider that has one.
Companies most in need of a CDN are those who aim to reach wide (and possibly geographically dispersed) audiences and/or require highly secure and reliable streams. Companies like:
- Ecommerce platforms
- Digital publishers
- Financial service providers
- Entertainment platforms
- Internet service providers
Benefits of Using a CDN for Streaming
By connecting servers across the globe, CDNs create superhighways that truncate the time it takes to deliver video streams from origin to end user. Sharing the workload across a network of servers also promotes scalability should viewership increase.
This is the biggest CDN selling point. They are the fastest, most reliable way to get your content in front of numerous viewers anywhere in the world. CDNs can accommodate viral viewership spikes and larger-than-expected live audiences. In this way, CDNs don’t just ready you for a large audience; they also build flexibility into your platform to handle unexpected opportunities.
Speed And Efficiency
Because CDNs quickly distribute content to edge servers, content delivered across them isn’t bogged down by local network conditions or the lengthy physical distance between end users and origin servers. For both live and video on demand (VOD) content, CDNs can deliver cached content with the click of a button.
Streaming through a CDN allows you to achieve the best user experience. CDNs minimize buffering and delays by using speedy superhighways to send streams to vast audiences across the globe. While your ISP or local network may slow delivery down at the first and last leg, the CDN will bypass any traffic in between. Stream quality is also bolstered by the aforementioned flexibility. Unexpected viewership spikes won’t threaten stream quality if your infrastructure can easily scale to support them.
Reliability And Security
Finally, CDNs provide an extra layer of protection through redundancy. Streaming through a CDN can help prevent distributed denial of service (DDoS) attacks, which occur when a site or resource is flooded by multiple, simultaneous attempts to breach it. That’s because a redundant CDN with multiple access points enables failover. By comparison, you won’t have any backup options when streaming with a single server. Additionally, individual CDN edge servers can handle more traffic than origin servers, protecting content distribution from network failures.
While some mega companies elect to build out their own global network of servers, this isn’t practical for most content distributors. CDN services allow broadcasters to outsource infrastructure and maintenance costs while still benefitting from the same global delivery power.
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CDN Options and Alternatives
Sound expensive? It’s true that investing in a reliable and expansive CDN is exactly that – an investment. If you’re concerned about your bottom line, consider whether or not a CDN is right for you or whether a free version may suite your specific needs. Just remember that the popular adage still applies: you get what you pay for.
Paid vs. Free CDN Services
Free CDNs are, well, free. That said, support for these CDNs is limited. If something goes wrong during streaming, you may have no recourse. These free services may offer access to vast numbers of viewers, but those viewers are likely to blame you should any technical difficulties ensue. When the stakes are high, such as with hyped-up live events or important business meetings, your best bet is to use a paid CDN. Paid CDN services, like Wowza CDN, regularly provide more reliable and higher quality streams. Paid CDNs also tend to include more robust support.
Cloud Computing vs. CDN
Cloud computing utilizes servers hosted on the cloud in providing services like storage, software, networking, and computer power on an a la carte basis. This is a cost effective and flexible option for businesses that want to access a range of technology on an as-needed basis. Similar to CDNs, cloud computing involves a network of geographically distributed servers. However, it’s not the same thing. CDNs have a specific mission to deliver large amounts of content as quickly as possible and scale up with viewership. Cloud computing is all about providing a buffet of digital tools and scales up with emerging practical needs.
When NOT to Use a CDN
CDNs provide many benefits, but they don’t make sense for every use case. If you have a small number of viewers and/or your geographical scale is limited, you may not need a CDN. Generally, unless your viewers are widely distributed, you can stream to all your them from a single server. The more elements you introduce into your streaming workflow, the more opportunities for failure, so why make it more complicated than it needs to be? Additionally, a CDN worth its salt costs money. Compare the egress cost of your streams with the cost of a CDN. Note that this number can vary based on deployment. If you’re unsure about whether or not you need a CDN, then consider talking to a streaming provider that can advise you on industry best practices and present solutions scaled to your needs.
What to Look for in a Live Streaming CDN
When it comes to live streaming, the CDN you select must be capable of accommodating a rapid uptick in viewers. Other key considerations include geographic coverage, security, and pricing. If you think you might need a CDN, then consider the following when looking for a CDN-enabled streaming partner.
Live Streaming Support
Will the CDN easily integrate with your streaming server or service to deliver streams to viewers? As we mentioned above, not all CDNs offer live streaming delivery, and by selecting one that broadcasts are already leveraging for video delivery, you’ll benefit from resources to get started. Technical support and documentation on streaming with given CDN can also come in handy.
The whole point of a CDN is to transport content from your servers to your viewers quickly. The round-trip-time (RTT) between each viewer and their local CDN point of presence (PoP) directly influences how fast that content is delivered, so you’ll want good coverage in the areas you’re serving. The ingest point should be close to your streaming server for the same reason. Every CDN provider shares a global map of their network. You’ll want to choose a provider that aligns with the geographic nuances of your audience to ensure efficient video distribution.
Support for adaptive bitrate streaming, sophisticated security measures like digital rights management (DRM), and multi-protocol delivery varies across providers. You’ll want to make sure all of your needs are met when comparing live streaming CDNs. Choose a streaming provider with a proven track record of security awareness and compliance.
If you’re already storing your content on Microsoft Azure or running your streaming server there, then it might make the most sense to use their CDN service as well. Consider the partners you already work with and what additional tools they might offer for a packaged deal.
This one is self-explanatory. Many CDNs charge on a cost-per gigabyte (GB) basis, whereas others are baked into a managed streaming solution like Wowza. Steaming Media Magazine’s Jan Ozer suggests that delivery pricing should be the most significant component of your total streaming costs, but it’s still important to compare your options.
Integrated vs. Third Party
You’re best off with a CDN that’s fully integrated into your video streaming platform. This ensures quick deployment of video-based applications, the simplicity of a single vendor, and – when video analytics are also available – more comprehensive insight across your streaming workflow.
How CDNs are Evolving for Next-Gen Streaming
Increased data, connectivity improvements, and technology advancements have collided to make streaming a part of everyday life. End users expect high-quality content with lightning-fast delivery — and CDNs play a crucial role in meeting these demands.
“Latency will always be a problem. For example, in virtual reality (VR) anything over seven milliseconds will cause motion sickness. When decisions are required to be taken in real-time, you cannot send data to the cloud. You can, however, make use of edge computing and a multi-CDN design.”
Edge computing brings computation and data storage closer to users. This improves response time and saves bandwidth by decentralizing processing and decision-making.
By bringing advanced computational resources into their PoPs on the edge, many CDNs are optimizing their infrastructure to significantly speed up users’ access to information and reduce data access costs for enterprises. This evolution is essential to 5G, and will help power applications like self-driving cars in the coming years.
Another development in the streaming industry is the emergence of low-latency technologies like Web Real-Time Communications (WebRTC), Low-Latency HLS, and low-latency CMAF for DASH. Many CDNs are adding support for these formats, which will enable even speedier video delivery than was previously possible. For interactive experiences like auctions, gambling, and sports broadcasting, the ability to stream real-time video at scale will change the game.
Streaming With Wowza’s Video CDN
Wowza offers a video CDN as part of our cloud-based video streaming platform, Wowza Video. This platform includes a wide range of streaming features, including an integrated best-in-class video player, end-to-end analytics, and an easy-to-use content management system (CMS). This single integrated platform makes it easy to get started fast and scale with your audience.
Wowza’s Real-Time Streaming at Scale combines our Wowza Video API with the ultra-low latency power of WebRTC. Our custom CDN makes it possible to stream at sub-second speeds to a million viewers, including live-to-VOD management capabilities.
Finally, our flagship Wowza Streaming Engine (WSE) product is a highly customizable, developer-friendly solution that makes it possible to tailor our streaming technology to any of your unique needs. For a while, we were offering our CDN as an add-on to WSE. However, we’ve recently started making WSE available as a hybrid cloud solution, making it possible for developers to keep the builder-focused software they love while taking advantage of not only our CDN, but also our player, analytics, and more.
Whether you’re looking to get up and running fast, stream in as close to real-time as possible, or create a custom solution that solves unique challenges, we’ve got the software, the team, and the CDN to get you and your streams where they need to go.
About Sydney Roy (Whalen)
Sydney works for Wowza as a content writer and Marketing Communications Specialist, leveraging roughly a decade of experience in copywriting, technical writing, and content development. When observed in the wild, she can be found gaming, reading, hiking, parenting, overspending at the Renaissance Festival, and leaving coffee cups around the house.