Content Delivery Network Strategies, by Stef van der Ziel

Question: What is the definition of a CDN?

Content owners of course compare CDN’s. But what is a CDN? Some say that CDN’s have become a commodity. I disagree. There are so many different approaches. Comparing CDN’s is comparing apples and pears. I have seen some lists on the net that try to categorize CDN’s into different categories. But IMHO that does not help content owners compare CDN’s.

Historically a CDN is a highly decentralized file distribution & geographical user load balancing platform.  The best example is Akamai who has deployed thousands of servers globally, close to many ISP networks.
Some claim that the Akamai model defines what a CDN is. But today there are so many different approaches, with different technologies, different regions and different market approaches.

For instance, there are CDN’s who use a highly global connected network, but have most servers centralized. SuperPop of MegaPop. The performance could be equal to highly distributed CDN’s, if the network is deep connected. Other CDN’s don’t own a single fiber but rent network resources and use a centralized or distributed application layer CDN. If the networks have great coverage and performance, this can compete with distributed CDN’s. And other CDN’s use P2P technology to distribute assets to end users.

Some CDN’s only focus on a specific region. Other CDN’s only focus on a specific technology. Streaming. Apps. Files. Gaming. And other CDN’s focus on a specific market: Broadcasters. Enterprises.

ISP’s can have a CDN within their own network. Even enterprises can have an on-net CDN.

IMHO you can’t define a CDN. CDN is a term that covers all kinds of distribution services with different approaches, different technologies, different visions and different market approaches.

The CDN industry is far from being a commodity. New technologies and new insights constantly change the industry. There is no single CDN that you can compare 1-on-1 with another one.

Here are some variables to start with. Have fun with categorizing and comparing, let me know when you are done :-)

• Coverage (global, regional, on-net)
• Features (file caching, support for various streaming types (which?), app support)
• Performance (actual peak capacity per delivery type, latency, bursting, uptime)
• Distribution (edge servers based, network based, megapop, overlay)
• Distribution technology (caching, P2P, relaying, managed asset & relay push)
• (Geo) Load balancing technology (DNS, network load balanced, application load balanced, P2P)
• Reporting (limited, in-depth, not realtime, realtime, text, graphical)
• Asset ingest and management (protocols, web based, API or just drop box)
• Live stream setup and management (manual by CDN operator, self service, API)
• Customer support (24*7 or office hours, 1st line helpdesk or actual senior engineers)
• Overall service quality (transparency, information, documentation, ease of use)