small correction Re: Content Delivery Networks

Can anyone give a breakdown of the different kinds of content
deliver networks? For example, we have Akamai, which appears to be
a pure Layer 3 network that is tailored to pushing relatively small
files like web pages and we have Lime Light Networks, which is a
mix of Layer 1 and Layer 3, that focuses on bigger files like video

I am not sure why you would say Akamai is "tailored to pushing
relatively small files", since I do not believe they say that
anywhere. LLNW does say they are focused on larger files. (I
believe LLNW claims Akamai is focused on smaller files, but do you
believe what Akamai says about LLNW?)

I can confirm that Akamai does not have a backbone. Neither does
Panther Express, CacheFly, or Mirror Image. While Level 3 (who owns
Digital Island, which they bought from Savvis, who got that when they
acquired Exodus, who bought way DI back when), LLNW, and at&t all
have their own backbones.

Any insights out there? And what are the major challenges in making
scalable content delivery networks?

Myriad. Some are hard to overcome, some are very hard. Keyword here
being "scalable" - which you failed to define. What is "scalable" to
you? 100 Gbps? 500 Gbps? The latter is medium-hard in the US, the
former is nearly impossible in South Africa.

Which brings us to geography. Are you US-centric? European?
Asian? Six continents? Just a few specific countries?

Plus, as you mention above, there's file size. How about streaming
vs. HTTP? Optimize for latency or throughput?

Did I mention cost?

Etc., etc.

If someone asked "what are the major challenges in making scalable
backbones?", how would you answer?