ITPRC NEWS - April 2001
Table of "Content"
By Irwin Lazar
As I write this I'm sitting
on a train heading back home from the recent "CDN" conference
in New York City. This event, organized by Penton events and Stardust,
focused on promoting the new technology of "Content Delivery
Networks or "CDN's." While the show did have some interesting
content (pardon the pun), there seems to be a few matters at hand that
must be addressed in order to fully understand the technology. These
topics are addressed below.
What the heck is CDN?
Ask ten people at the show for their definition of "CDN"
at it is likely you would have gotten ten different answers. Some folks
think of CDN as the delivery of streaming video or television over the
Internet or private networks, others define it as web-switching or
content-switching, and yet others define it as ways to improve web site
performance. The truth is that a CDN is a bit of all of the above and
then some. In my opinion, a CDN is a network optimized for specific
content, such as static web pages, transaction-based web sites,
streaming media, or even real-time video/audio.
There are two general
approaches to building content delivery networks, the overlay approach
and the network approach.
In the overlay approach,
application specific servers are deployed at various points in the
network to handle the distribution of specific types of content (such as
web graphics or streaming video). Core network infrastructure, including
routers and switches, play no part in content delivery, short of
providing basic connectivity or perhaps guaranteed quality of service
for specific types of traffic. A good example of the overlay model is
the CDN deployed by companies such as Akamai, Digital Island and
Speedera, in which content is replicated to thousands of servers around
the globe. User requests for web content is redirected to the
nearest CDN server in order to improve web site response time. The
overlay approach simplifies management and opens new service
opportunities since CDN service providers don't have to control the
underlying network infrastructure. Offering new services via the overlay
approach is as simple as distributing new code to CDN servers.
In the network approach,
code is deployed into routers and switches that allow them to actually
recognize specific application types and make forwarding decisions based
on pre-defined policies. An example of the network approach is devices
that redirect content requests to local caches or switch traffic coming
into data centers to specific servers optimized to serve certain types
of content. In some cases, the network approach will be jointly used
with the overlay approach (for example, when a switch front-ending a
server farm redirects an HTTP request to an Akamai server). IP Multicast
is a good example of an early network based approach to optimizing the
delivery of specific types of content.
What is CDN Peering?
Recently, several manufacturers of content delivery devices such as
caches and media servers have banded together to create forums and
associations to promote the idea of "content peering." In this
model, dozens of service providers and enterprises would create content
delivery networks and peer these networks via as-of-yet-to-be developed
standards in order to provide global content distribution coverage. A
new IETF working group is also underway to address this issue. The
driving forces behind efforts to establish content peering standards are
hardware manufacturers and smaller CDN providers in an effort to take on
industry behemoth Akamai
The problem with this
approach is that service providers don't have a great record of peering
thus far (think of efforts to implement guaranteed quality of service
across service provider boundaries that have failed miserably). For CDN
peering to work, service providers would have to deploy billing and
management systems that would allow their networks to exchange traffic
and enforce SLA's. Given the current reluctance among many service
providers to peer unless absolutely necessary, the jury is still out on
the future of CDN peering.
One area where CDN peeing
might work is for enterprise customers who are building internal CDN's
on their intranet. Typically these networks are used to distribute
streaming or real-time video such as e-learning and/or corporate
announcements. Enterprises would theoretically be able to use CDN
peering standards to peer their own internal CDN networks with CDN
service providers to make content available both internally and via the
Internet to customers or mobile workers.
What are the market
During the CDN event, many companies exhibited products and services
that allowed CDN's to deliver all sorts of exciting new applications,
everything from collaborative tools to games to pay-per-view television.
The only problem is that nobody seems to have figured out if there is a
business case (i.e. "what will people pay for?") I for one
can't possibly imagine paying to watch a movie on my PC. Gaming seems to
have appeal, but a lot of the CDN systems are reliant upon carriers
being able to deliver high-speed broadband services, with guaranteed
service levels, to residential customers, something that has been
difficult for many carriers to deliver. Given the current focus on P2P -
path to profitability - content providers are going to have to provide a
clear business case before service providers are going to make the
investment to support these applications.
What does the future
So far, the biggest benefit of content delivery networks has been in
improving the performance of web sites. Whether or not content networks
become the basis for a new wave of Internet-based services remains to be
seen. What is needed is a killer application that justifies
One such application might
just well be music distribution. The current court battles over Napster
appear to be winding down and it is entirely possible that the music
sharing service will soon be shutting down. Assuming that SDMI (The
Secure Digital Musical Initiative) can establish some sort of encryption
method that stops illegal copyrighting, it is entirely likely that big
music power houses such as BMG and Columbia will make their entire
catalogs available on a pay-per download basis. Napster in its current
incarnation is a peer-to-peer service; users download music directly
from each other's computers. If the music companies themselves begin to
make their catalogues available for download, they will need to utilize
a content delivery system that insures that their servers aren't crushed
under the load of millions of teenagers trying to download the latest
Brittany Spears hit single. This prospect alone may require content
delivery systems with far more capability than current content delivery
networks. Music companies may also choose to make videos,
promotional clips, and other forms of content available to consumers.
Content delivery networking is a broad term that encompasses many
different technologies, all with the common goal of improving Internet
performance. Content delivery networks have successfully improved the
end user experience for millions of web users. Their emergence as key
infrastructure components to support next generation Internet services
will be based on the development of a strong business case for the
deployment of such services.
The ITPRC has recently launched a page on Content Networking. This
page contains links to additional information about CDN's and also hosts
a CDN mailing list. See www.itprc.com
Irwin Lazar is a Senior
Consultant for The Burton Group. He focuses on strategic planning
and network architecture for Fortune 500 enterprises as well as large
service providers. He is the conference director for MPLScon and
runs The MPLS Resource Center www.mplsrc.com
and The Information Technology Professional's Resource Center www.mplsrc.com.
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