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Speed, Security and Shifting Specs

How Content Delivery Networks Manage Bandwidth Demands

Speaking at video industry events this year, Charles Kraus noticed the same question popping up at each one: Just how many over-the-top offerings exist? So Kraus, the senior product marketing manager for content delivery network (CDN) services provider Limelight Networks, took on a daunting task, tallying up every OTT offering he could find around the world.

According to his rough data, the number of OTT services available today—small, medium and large, from the most niche-oriented to the most popular—has passed the 3,000 mark. And that’s a low-end approximation, he believes.

The sheer number of online video services—and that number is rapidly growing—means great business for CDN companies. According to Cisco Systems’ 12th Annual Visual Networking Index, released in June, CDNs were responsible for carrying just a bit more than 50 percent of internet traffic worldwide in 2016. By 2021, Cisco forecasts that 71 percent of all internet traffic will run through CDNs, with those services handling a video content load that’s expected to account for more than 80 percent of all internet traffic.

In the 2017 Cisco Visual Networking Index, Cisco forecasts that 71 percent of internet traffic will run through CDNs by 2021, with those services handling a video content load that’s expected to account for more than 80 percent of all internet traffic.

All of this growth has put the backbone of the internet on the X-ray screen. CDNs make up a significant portion of the global internet and offer all kinds of content delivery services including video streaming, downloads and file caching.

The added video traffic has CDNs keen on solving associated challenges: reducing latency, ensuring content security and keeping up to speed with every delivery standard used by content companies. We spoke with Kraus and others in the CDN space about how they’re tackling today’s onslaught of entertainment services.

Latency, Latency, Latency
It’s a painful reality: if you’re watching a live event via an online service, you’ll be behind the over-the-air or satellite broadcast, even if it’s just by a few seconds.

A lot of that lag has to do with the video specifications most widely used today for live digital content delivery, according to Ted Middleton, chief product officer for Verizon Digital Media Services, which operates the Edgecast CDN service.

This graphic from Wowza Media Systems describes a streaming latency and interactivity continuum, where live streaming media performance is a balancing act between playback quality and interactivity. For use cases involving higher degrees of interactivity, lower levels of latency are required to provide a positive user experience.

Take the popular HTTP Live Streaming (HLS) protocol as an example. “Traditional recommendations in the HLS spec typically induce an approximately 30-second time-behind-live [delay], based on the number of segments and segment durations required to generate a live playback manifest,” Middleton says. “Other formats have different recommendations, but nearly all of the modern HTTP-based adaptive bit rate formats have some amount of latency induced in order to provide reliability and reduce buffering.”

It makes sense. The process of delivering live video content digitally must account for internet bandwidth and the number of people viewing at any one time. But that doesn’t make the end user any more patient.

An early July study from live streaming tech company Wowza Media Systems found that any delay of 15 seconds or longer for a live streaming sports app was detrimental to the viewing experience, with spoilers readily accessible on social media. Wowza’s study of live streaming apps in general found latency to be as low as 9 seconds, but also as high as 101 seconds.

“[Live events] happen only once, and there’s no tolerance for error,” says John Bishop, chief technology officer for CDN heavyweight Akamai. “Unlike the earlier days of on-demand streaming, when the occasional glitch was accepted, any hiccup in live delivery today isn’t an inconvenience to the audience—it’s a disruption.”

What Akamai and other CDNs are doing to make live digital video closer to truly “live” is twofold. Their first goal is to ensure they are able to ingest the content at a location as close as possible to its point of origin (with the signal being picked up via a production truck or master control, for example) in order to quickly transcode and deliver across the network. Second, they are coordinating with client-based software (especially video apps, but also hardware) to more easily communicate with CDNs.

“This can help make sure the video is optimized for the viewer’s device capabilities, network type and conditions,” Bishop explains.

Part of facilitating the former is the reason you’ll increasingly hear “CDN” and “edge” in the same sentence in the years to come. A CDN’s best bet for a seamless user experience is to deploy servers and nodes as widely as possible, with the goal of narrowing the geographic distance between the network and the end user.

“One of the critical aspects of providing a quality streaming experience for consumers is moving the content as close to the edge of the network as possible, [something] traditionally done with an edge CDN provider,” according to Ed Haslam, chief marketing officer for Conviva, a digital video analytics firm whose roughly 200 clients (mostly in the OTT space) are reliant on CDN services.

“They’re doing that to decrease the latency when you hit play in the video player. Get the content as close to the viewer as possible to minimize the video start time, which is often critical for consumers,” Haslam says.

Content Security
As CDNs are challenged with handling more content for worldwide audiences, they will need to store it and move it to more locations. Security is one of the primary concerns of content owners, CDN representatives agree.

Limelight’s CDN manages a mix of live and on-demand streaming video traffic.

“As a shared service, the main challenge for us is that not all of our customers have the same content security needs, and many leverage different security solutions,” says Jennifer Cleveland, vice president of content sales for CDN company Level 3. “The challenge becomes making sure our system is flexible enough to work with each customer’s needs, without having to create a completely customized solution for each. It can require extra time and diligence in the onboarding process.”

Limelight’s Kraus echoes those thoughts, noting that CDNs widely offer a “suite of protections for customers” that includes distributed denial-of-service (DDoS) and firewall safeguards that were previously sold separately. He adds that there’s an advantage to having your CDN supply security services. “Because most CDNs are massive global networks, customers are protected without having to do much. The CDNs can absorb things like DDoS attacks. Customers won’t even know they’re being attacked.”

While movies and TV programs may be the most sought after content, Akamai’s Bishop stresses, they are far from the only assets CDNs are being tasked with protecting. “Security doesn’t apply solely to content,” he says. “Web security in general is of vital importance to any organization delivering premium content. Keeping sites and apps up and running, even if they’re under attack, is critical to any organization’s business and brand.”

4K, VR … and Bandwidth Needs
While it may feel like a slow burn so far with regard to 4K and virtual reality (VR) digital content delivery, both applications will increasingly push ISPs and CDNs to figure out how to get high-bit-rate content through low-megabit-per-second pipelines.

Cisco estimates that 4K IP VOD content will account for 30 percent of global VOD traffic by 2021, while combined VR and augmented reality (AR) video traffic will grow 20-fold during the same span.

Wowza looked at latency for several live streaming sports platforms, finding that NCAA March Madness Live and WatchESPN provided the lowest desktop latency. MLB At Bat scored with the fastest TTFF (time to first frame) and end-to-end latency delivery on mobile devices.

While Netflix and other service providers recommend a connection of at least 25 Mb/s to stream 4K content, Akamai’s first-quarter State of the Internet report found that the average download speed for U.S. internet users was less than 19 Mb/s (though still up 22 percent year over year).

“Virtual reality makes it worse,” Limelight’s Kraus says. “Not only do you have to accommodate a 4K stream, you have to accommodate for the adjacent views when a person moves their head up, right, left or down. You have to take that 25 [Mb/s] and multiply it by four. Right now, 4K VR is a dream, with the amount of bandwidth needed.”

Akamai’s Bishop strikes a more optimistic note. CDNs have faced similar challenges in the past, tasked with last-mile delivery of high-definition and higher-frame-rate video content using less than ideal pipelines. “It’s not a matter of throwing more servers at the challenge,” he says. “It’s making the platform smarter and more nimble, being able to deliver the higher bit rates needed for these emerging formats with greater efficiency.” 

Download the September 2017 issue of Digital Video magazine