CDN Strategy Blog

Telcos sell flat-fee broadband with unlimited traffic for a fixed price. Competition is strong, prices are going down. To compete, telcos have to offer even faster connections at the same, or lower prices.

With over 85% broadband penetration, the markets are saturated. At the same time, traffic usage is growing strong. To cope with the growing demand of traffic, telcos face deep infrastructural investments. But margins are shrinking.

So it makes sense that telcos look at various ways to tune traffic, to save costs. Some have used brute force blocking of P2P traffic. Others use traffic shaping. Some look at caching content, others look at deploying CDNs.

(On an interesting side note, a federal appeals court has ruled that the USA FCC should not have enforced a policy statement on Comcast who blocked P2P traffic in order to guarantee a working network).

I occasionally get questions why telcos should use a CDN and not deploy a transparent caching solution instead. My answer is that these two don’t do the same job and that they actually may need both.

Transparent caching

Is technically transparent. You can offload any (regular, static) HTTP content out there. But caching (we call this ‘unmanaged’), is not transparent to content publishers. These publishers do not allow anyone to redistribute their content. Doing so may/will cause a lot of legal issues.

Content publishers have legal agreements with content producers. These agreements may cover delivery limitations, QoS guarantee, reporting and quality guarantee.

Content publishers will also have legal agreements with advertisers. They need to report back viewing behaviour, including viewing time, QoS and delivered quality (bit rate).

Breaking into the delivery with a transparent caching solution violates legal agreements between content providers and content publishers. Many countries have laws that prevent telcos from touching the content in any way.

A caching solution is not a good fit for non-HTTP traffic such as (RTSP, MMS, RTMP) streams. There may be RTSP relaying solutions around, but I question if they are fully compliant.

A caching solution is also not a good fit for non-static content like live streams and advanced progressive downloads. You can’t assume that when content is distributed over HTTP, it can be cached.

Content publishers simply don’t know what happens with their content when their content is cached. Even if the caching solution could provide reports, the content publisher wouldn’t know that the content is cached, that reports are available or how to obtain them.

A CDN

Is a managed solution. A CDN can actually use caching technologies to distribute assets, but a CDN can also use alternative mechanisms to distribute content and streams around, for instance via a managed asset distribution engine and a managed live stream relaying engine.

You can’t offload any content using a CDN though: only for those content publisers who allow to do this. A CDN is technically not transparent but from a business perspective it is because the content publisher exactly controls which assets are distributed through the CDN and gets full detailed reports back so they can guarantee their legal agreements with their content producing and advertising partners.

You can use both a a caching solution and a CDN to geo optimize delivery of HTTP assets. In general a caching solution is used to offload generic static HTTP content (if legally allowed) and a CDN is used to offload specific (in many cases premium) content in agreement with the content publisher.

A CDN is not just used for offloading and geo optimizing traffic: it is also used to monetize the network by selling CDN resources to content publishers. Think of telcos selling CDN services into the web / OTT / mobile market.

So in general:

Transparent caching is a better fit for offloading generic static HTTP content that is not premium and / or not limited by legal agreements or laws.

It is basically an unmanaged service for offloading traffic with technical and legal limitations.

CDNs are a much better fit to optimize distribution of all premium content, non-static HTTP delivery, non-HTTP delivery and any other content where rights are limited by legal agreements and laws.

A CDN is a premium, managed service. You can use it to offload traffic, but it also supports many other business models and can be used for many other applications. A CDN requires an agreement between the distributor and the publisher.

Transparent caching and managed CDNs are complementary.