What Is a CDN and Why Is It Critical to Live Streaming? (Update)April 14, 2022
Video streaming is skyrocketing, causing exponential growth in the content delivery network (CDN) market. Cisco estimates that 72 percent of all internet traffic crosses a CDN — up from 56 percent in 2017.*
Put simply, CDNs make up the webs in World Wide Web and the nets in internet. Made up of interconnected servers deployed across the world, they ensure speedy, high-quality access to all things online.
For viral content and geographically dispersed audiences, CDNs are an essential workhorse of any streaming workflow. Beyond that, they solve for slow video startup times, stream interruptions, and that dreaded spinning wheel that we call buffering.
So what exactly is a CDN, and why are video CDNs critical to streaming? Read on to learn more.
Table of Contents
- What Is a CDN?
- How Does a CDN Work?
- How Does a Video CDN Work?
- Types of CDNs
- Benefits of Using a CDN for Streaming
- Paid vs. Free Video CDN Services
- When Not to Use a CDN
- What to Look for in a Live Streaming CDN
- How CDNs Are Evolving for Next-Gen Streaming
- Streaming to a Video CDN With Wowza
What Is a CDN?
As the name suggests, a CDN — short for both content distribution network and content delivery network — is a system of geographically distributed servers used to transport media files. These networks remove the bottleneck of traffic that could result from delivering content with a single server by distributing text, image, and video data to edge locations across the world.
As a result, the edge servers share the burden with the origin server. Instead of each viewer’s request to view a stream traversing the entire internet to one central location, the CDN server closest to them provides the content and processing power needed. As such, the load is spread across many cooperating servers.
How Does a CDN Work?
Ever wondered how Amazon ships packages so quickly? A CDN works in the same way. Think of Amazon’s headquarters as an origin server and Amazon’s distribution centers as edge servers.
When you submit an order to Amazon, the distribution center closest to you attempts to fill it. That warehouse will either have the product available to send directly or request it from another distribution center.
Likewise, when you attempt to stream a video from a CDN, the edge server closest to you tries to deliver it. The server will either have the media files cached or send a request to another server that does.
Amazon streamlines delivery by distributing goods from these local warehouses rather than shipping each item directly from their central hub. Similarly, CDNs streamline delivery by sending content from local servers rather than sending it directly from the distant origin server each time.
How Does a Video CDN Work?
As described above, a CDN uses an extensive network of servers placed strategically around the globe to distribute video streams quickly. Once a stream is posted or goes live, it populates all over the world. When a user pushes play, the CDN server closest to them delivers it. That way, after the stream has been initiated, the media files remain ready for another user in the same area.
It used to be that streaming content was delivered via dedicated servers using the Real-Time Messaging Protocol (RTMP). Thankfully, the industry transitioned to HTML5- based technologies in the 2010s. This helped combat buffering and improve caching efficiency in one fell swoop.
More specifically, the move to protocols like Apple HTTP Live Streaming (HLS) and Dynamic Adaptive Streaming over HTTP (MPEG-DASH) brought the power of CDNs to streaming. That’s because these new technologies ran on plain-old HTTP web servers rather than dedicated RTMP servers.
Today, 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 functionality 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.
Types of CDNs
All well-known websites use one or more CDNs. For example, Google, Facebook, and Amazon have proprietary CDNs, and each one specializes in the particular type of service they provide. For platforms like Netflix that revolve around video distribution, an in-house network that’s purpose-built for streaming might be involved. We refer to these types of networks as video CDNs.
Alternatively, when it comes to commercial CDNs, some are much better suited for static websites. In contrast, others focus on specific regions (such as CDNvideo for Russia, Alibaba for China, and GS Neotek for South Korea and Asia). The right CDN for your workflow all depends on what you’re trying to achieve.
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 improves scalability should viewership increase.
Specific benefits of streaming with a CDN include:
- Scalability. This is the biggest selling point of using a CDN. It’s 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.
- Quality. 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.
- Speed. 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.
- 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.
- Affordable infrastructure. 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 benefiting from the same global delivery power.
Paid vs. Free Video CDN Services
Free CDNs won’t break the bank — but you’ll get what you pay for. Support is limited, and if something goes wrong during streaming, there may be no recourse.
These free services may offer access to vast numbers of viewers, but viewers will assume it’s your fault 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.
Using the Wowza CDN or another paid service comes with a near-guarantee of reliability and quality. We designed our service for getting live video data to users with high reliability and availability.
When Not to Use a CDN
CDNs provide many benefits, but they don’t make sense for every use case. A CDN isn’t the best fit for the following scenarios:
- Small-scale streaming. If you have a small number of viewers and/or your geographic scale is limited, you probably don’t need a CDN. Generally, unless they’re widely distributed, you can stream to all your users from a single server. The more elements you introduce into your streaming workflow, the more opportunities for failure — so why do so unless you must?
- Limited budget. We recommend that you compare the egress cost to the cost of a CDN, as this can vary based on deployment. As covered in the prior section, there are both paid and free CDN options available.
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. Geographic coverage is also a key consideration, and pricing always comes into play. Here’s our list of qualities to look for when deciding on a video CDN.
- Live streaming support. That is, will the CDN easily integrate with your streaming server or service to deliver live streams to viewers? As we mentioned above, not all CDNs offer live streaming delivery, and by selecting one that broadcasters are already leveraging for video delivery, you’ll benefit from resources to get started. Technical support and documentation on streaming with a given CDN can also come in handy.
- Proximity. As they say: location, location, location. 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.
- Feature set. 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.
- Cost-efficiencies. 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.
- Pricing. 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. Streaming 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 solution vs. third-party providers. 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.
Network World contributor Matt Conran explains:
“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 to a Video CDN With Wowza
Wowza offers a video CDN as part of our video streaming platform, and its also available as an add-on feature for Wowza Streaming Engine.
In addition, Wowza’s technology supports seamless delivery to Facebook Live, YouTube Live, or any CDN of your choosing.
The Stream Targets feature allows content distributors to select one or more destinations — such as a third-party CDN — to distribute the live stream. This one-in, many-out approach ensures scalability with ease.
Available Stream Target Destinations Include:
- Social media websites such as YouTube Live or Facebook Live
- Another single destination in a point-to-point connection
With over a decade of experience powering streaming for more than 35,000 organizations, Wowza’s full-service platform is the gold standard for video technology. We provide our customers with the most reliable and scalable video solutions on the market by integrating CDN technology into our full-services platform.
Explore our product portfolio to learn more.