I'd like to know how the inter-connection between edge servers work in
a CDN. "Edge-server" are located close to the access point of the
users of an ISP for example. These big servers cache data on the
"edge" of the network so that for example you can download data
quickly from websites offering video download (e.g. movielink).

I understand the principle of the d/l by end end-user. But how are
these edge servers updated with new content? Each time a new movie is
made available on a site offering VOD, is the movie systematically
replicated to every edge server?

My company wanted to release shows (VOD) on the net. We got good price
from a CDN but the price dramatically increased when we told him it
was a daily show and therefore new content had to be ready every day.
They said "the cost of pre-populating" was too high. And I do not
understand that very well.

Are there alternative when you have content that is new every day and
you want to make it available online.

Thanks.

How the edge servers are updated all depends on the company that you
are using for this service. Generally they will either poll your
servers at a specific time to download new content, or they will
periodically check to see if the version that they have is currently
the most recent.

Many ISPs have passive proxy servers that fulfill this type of
function to save themselves bandwidth. Basically when one of their
users tries to access the content for the first time the passive proxy
will cache the data and when the next users tries to access the data
the passive proxy will poll the server to see if the data is still
current, if it is then the passive proxy will feed the content
directly to the user, not needing to download it again. If the data is
out of date then a re-download occurs and the passive proxy server
caches it again. This works with websites, downloads and many video
feeds, but likely not most streaming video/audio.

Content delivery hosting is not going to be cheap, the only thing I
can suggest is to shop around and evaluate the different options
available based on your criteria.