March 10, 2011
By Dom Robinson Contributing Editor
Featured Articles
For the rest of the Spring 2011 (Sourcebook) issue of Streaming Media magazine please click here

Telcos and the State of Content Delivery

I am regularly being asked about the telcos’ activity in the CDN space. It has become clear from writings by Dan Rayburn (see www.cdnlist.com) and from vendors (see www.bluecoat.com and www.jet-stream.com) that more and more telcos are becoming active in the content delivery space. So Streaming Media asked me to review this activity and to share my thoughts.

My first thought is that the world can always use more TLAs (three-letter acronyms), so I would like to introduce a new one: the TDN—short for telecontent delivery network.

Although some might argue it’s only a nuanced version of a CDN, I’ve concluded that the TDN differs from the CDN in some key ways that I will break out in a moment. When telcos say they are “becoming CDNs,” that’s a little like a wasp declaring it is becoming a bee. There are many similarities, and sometimes it takes an expert to distinguish the two, but they are undeniably distinct.

Rayburn also draws a distinction: his CDN list’s notes distinguish Pure-Play CDNs from Non-Pure-Play CDNs. I think it is time to distinguish even further. If these were organic life forms, then we could be looking at the separation within the binomial taxonomy at (for example) a “class” or “order” level. Yes, both TDNs and CDNs are service offerings enabling the delivery of content, and both offer networked delivery of content. However, there are significant distinctions within the definition of the word “network” when we dig below the surface.

TDN vs. CDN: What’s the Difference?

For a CDN, the network may physically consist of many networks, each with autonomous owners (autonomous systems or “AS” in internet terms), making the topology of the service something that is run with the agreement of the owners of these many networks. These may well include core networks that the CDN operates itself, or there may be a set of complex commercial leases of various network links from a number of telcos, which makes private links between all the other ASs. In effect, since each ISP is defined by its AS, this would mean that such a CDN would more than likely also be technically an ISP. However, CDNs rarely (as far as I know) offer subscriber access to business or home users in the way that we more commonly perceive an ISP to do. (Confusing, eh?)

A TDN, while it will also consist of multiple physical networks, will differ. While TDNs may comprise multiple ASs, this is usually a legacy from whatever acquisitions telcos perform to create their networks. As the acquisitions are completed, the control of the AS is centralised. While there may be several “autonomous” systems, there is a single policymaker deciding on the architecture and use of the networks. And while they may have legacy technological differences, a single entity makes decisions about every aspect of those networks. No “agreement” has to be made outside of the telco. Since the decision making is centralised, there are fewer commercial barriers and, in theory, the costs of internal utilisation are exactly that: internal to the telco.

This then starts to reveal a dramatically different landscape, almost literally, for the TDN and the CDN. And yet we see them both courting the same end customers and purporting to offer the same service.

Content Delivery Logistics

This is unarguably odd: to draw a non-IT comparison, this is like an air freight company (the CDN) and a rail freight company (TDN) attempting to win a logistics contract. For the sake of this analogy, let’s also consider the local road courier services that take the “stuff” from the depot to the homes and businesses akin to the ISP. Also, weather here is analogous to network prices and conditions.