Content Distribution Networks (CDN)

According to Cisco’s recent Visual Networking Index, IP video traffic, is set to account for 82% of all consumer Internet traffic by 2020.

Based on this forecast, any organisation contemplating on providing OTT streaming services, is going to struggle to achieve this on their own (unless they have very deep pockets). Which is where content distribution networks (CDN) are able to assist.

History

The concept of CDN’s have been around for over 30 years, in the form of server farms, hierarchical caching, and caching proxy deployments.

However, as the World Wide Web (WWW) exploded in popularity in the mid-late 1990s, leading network engineers realised that the architecture of the Internet was not designed to scale to meet the rapidly increasing level of network traffic.

It was around this time that the world’s first CDN (Akamai) emerged, from an entrepreneurship competition at MIT.

How They Work

Simplistically, a CDN is nothing more than a network of dedicated caching servers, whose main purpose is to distribute, and cache, content closer to the end-users who are consuming it.

Take for example a user who’s trying to download a webpage, a software update, or an audio/video file. Rather than have the user’s request traverse the internet, to fetch their content from the origin server (possibly located on the other side of the world). The CDN is able to respond to the user’s request, and serve the object from an “Edge” server/node, closer to the end user (often from within their own country, or ISP).

Being able to serve this content closer to end users has a number of benefits, beyond the obvious – including:

• Offloading request/response load from the origin
• Providing scale on demand,
• Improving performance,
• Added Security resilience

The recent UEFA Euro 2016 football tournament that took place in July.  24 of Europe’s top football/soccer teams, played 51 matches, across 10 venues in France. All matches were streamed live, with the final hitting 3.3 million concurrent streams @ 7.3 Tbps at peak, during the match’s overtime period. Achieving this sort of scale, and capacity, without a CDN, just wouldn’t be possible.

Caching

Apart from the obvious benefit of caching content closer to end users, CDN’s also provide a number of other benefits, including:

• Reduced CapEx on web, and storage, infrastructure.
• Lower round-trip latency (i.e. potentially resulting in faster start-up and load times).
• The ability to dynamically scale, to accommodate planned, or unplanned, traffic spikes/events.
• Failover/DR functionality – by being able to serve ‘stale’ content from cache, on the rare occasions an origin should fail.

Performance

Whilst the majority of CDN’s provide basic caching, and offload, larger CDN’s may also provide a number of performance, and workflow, related benefits, including:

• The ability to parse HTML at the Edge, prior to it being served to end users. This allows the CDN to ‘prefetch’ any objects contained within the HTML, and cache them, prior to the end user’s browser requesting them. Subsequently resulting in faster, response/delivery times.
• TCP optimisations such as slow start, timeout, and recovery tuning all assist in establishing, maintaining, and re-connecting.
• Dynamically detecting, requests from mobile, or desktop systems, at the edge, and redirecting these to device specific pages/video content.
• In some instances, the CDN can also provide transcoding, and stream packaging functionality. Allowing customers to upload a single, HD, mezzanine video file, that can then be transcoded into n’ number of renditions, dynamically segmented, wrapped, and served, in a HDS/HLS or DASH format, to desktop, or mobile, devices. This feature not only assists in reducing CapEx on costly video encoding hardware, it greatly simplifies the video workflow.

Security

Generally speaking, Media and OTT service providers don’t see themselves as high value targets for hackers, or malicious actors.

Preferring to (incorrectly) presume that Government, Financial, or Military institutions provide better bragging rights, or financial gain.

The reality is, in this day and age, any organisation is a potential target, with OTT service providers being no exception.

For example, let’s say an OTT service decides to stream a controversial, politically sensitive, movie, that some malicious actors/organisations have very strong opinion on.

All it would take, would be for a disgruntled hacktivist to decide to make a point, and attack the OTT service’s origin/database/authentication, or DNS server, and the OTT service would be offline. With end users being unable to access said organisation’s applications, websites, or video content.

This would subsequently result in a potential loss of revenue, damaged brand reputation, and seriously annoyed/frustrated users (especially if they’re trying to watch the latest episode of Game of Thrones!)

With this in mind, it’s worth considering that larger CDN’s, by their very ‘distributed’ nature, are well suited to managing, and mitigating, common security related scenarios, including:

• Providing DDOS protection at the Edge, rather than at the OTT service provider’s origin/firewall.
• Authenticating users at the Edge, as opposed to directly at the OTT service provider’s origin/authentication system.
• Geo-blocking unauthorised users at theEdge, often within their own geographical region, rather than at the OTT service provider’s origin

Monitoring and Reporting

Historic influential thinker, and one of the founding fathers of business management theory, Peter Drucker, once famously stated “if you can’t measure it, you can’t improve it”. This rational still rings true today – especially within the streaming media industry.

Metrics and analytics, are a core component of the success of any OTT service provider. Not only to help organisations measure the performance, and quality of experience, of their platform, but they’re critical for the continual improvement of products, and services.

This requires the ability to:

• Monitor the quality of service of streams being served to end-users,
• Measure peak throughput, and audience concurrency,
• Observe network conditions and capacity,
• Track number of plays, play duration, and title metadata,
• Capture client-side analytics such as buffering, errors, start-up times, as well as advertising specific metrics.

Apart from the obvious business benefits of having visibility into the above metrics, analytics reporting can also be very useful for support teams in diagnosing, and troubleshooting, stream related issues.

Whilst not all CDN’s provide client-side analytics, at a minimum they should provide a comprehensive set of tools, and dashboards, to monitor, and capture, as many of the streaming media data points as possible.

So as you see, at their most basic, CDN’s provide a number of benefits to OTT service providers. However, as consumer demand for high bitrate video content continues to grow, at an exponential rate, their role in the OTT ecosystem becomes almost mandatory (unless you’ve got the capability to build out your own distribution network…but that’s a story for another time).

Matt Voerman is a Senior (Media) Engagement Manager for Akamai Technologies.
The views, and opinions, expressed on this site are his own, and not those of his employer’s.