Streaming Content

[DonE@activate.net]

I realize the initial emphasis of this WG is web content, but streaming
content is often mentioned and it is recognized that at least in the future
it will just as important to deal with streaming media.  And it is also
recognized that most of what is done in the WG will apply to streaming
content.  What I'd like is to be able to use the WG's work as soon as
possible to help solve current needs, so I'd like to help in this process
in a way that will have largest impact for streaming, but not detract from
the main emphasis on web content.

The same CDNP model applies to streaming content as applies to web content,
but the use of CDNs is a lot further along for web content, as shown by the
following table:


                          |                Type of Content
                          |------------------------------------------------
                          |        Web          |        Streaming
   -----------------------+---------------------+--------------------------
                          |                     |
   Matching content & CDN | Manual -> Automated |         Manual
                          |                     |
   -----------------------+---------------------+--------------------------
                          |                     |
   Distribution           |   Semi-Automated    | Manual -> Semi-Automated
                          |                     |
   -----------------------+---------------------+--------------------------
                          |                     |
   Request Routing        |     Automated       |    Manual -> Automated
                          |                     |
   -----------------------+---------------------+--------------------------
                          |                     |
   Accounting             | Manual -> Automated | Manual -> Semi-Automated
                          |                     |
   ------------------------------------------------------------------------

The impression I get is what is currently needed for web content is a way
to automate the current processes involved in matching CP's content with
the appropriate CDN(s) and to be able to collect uniform accounting data
from those CDNs.  Currently CPs are successfully using manual methods to
use multiple CDNs for streaming, but the highest priority need is to
negotiate request routing between the CDNs.

There are a couple of other differences between web serving and serving
streaming media content that need to be understood.  First, CDNs only become
important to webcasters for higher bandwidths.  Webcasting at bit rates
100 kbps or less, which is mostly what has been used up till now,  generally
works fine straight over the Internet with no CDN involved; of course,
international webcasts are a little harder, so CDNs may be needed even at
100 kbps.  Second, webcasters may not be content providers and they may not
have a CDN; that is, they may be in between, owning lots of encoders and
media servers, but having to rely on CDNs to get broadband to their end
users.  Another difference is that webcasters deal with live (CONTINUOUS
MEDIA) as well as on-demand content.  But the CDNP model still applies to
the live case.  The only difference is in the distribution phase, where,
instead of distributing content to the CDNs, some sort of connectivity
between the originating encoder/server/CDN and the destination CDNs needs
to be set up, so that broadband will get from the CP to the end users at
the time of the live event.

The request-routing protocol needs to be fast enough so the time of DNS
lookup is not noticeably increased.  I assume the webcaster owns the parent
CDN that has an algorithm that determines whether a child CDN should be
used.  In the initial implementation, the algorithm would take the IP
address of the end user (client) and the desired content as input and 
use its knowledge of CDN content distribution, CDN footprint and cost
that each CDN is charging the webcaster to make a CDN choice; then the
protocol would ask that CDN whether it can serve the content, and, if so,
would pass the request to that CDN, which would return the IP address of
the surrogate that would serve the content (if not, the parent CDN would
go on to its second choice, possibly itself).  In a later implementation,
the protocol would return a quality metric (whose meaning would be
negotiated off line between the parent and the child CDNs), so the parent
CDN could decide based on current network conditions which CDN to use.