Cisco’s IP Television Solution
In keeping with the AVVID model, Cisco’s IP/TV solution is one member of the
Cisco Content Delivery Network solution set. As you’re well aware, television as
we know it consists of hundreds of channels of programming to choose from, but
you must subscribe to channels to receive them.Television is a broadcast medium,
and uses various mediums to receive the information, such as coaxial cables and
satellite dishes.
IP/TV differs from this only in that the medium is Ethernet networking and
uses the IP architecture for the distribution medium. Cisco’s IP/TV solution uses
numerous devices to create the content delivery portion of the network. Looking
back at Figure 10.20, the media servers are now expanded out to devices with
specific functions. Before these can be discussed, let’s do a quick review of public
television so we have a basis for the Cisco’s IP/TV solution itself.
Public television uses broadcasting to send out the data to subscribers. It is a
form of multicasting in that only subscribers are permitted to see the information,
but it uses a broadcast medium to carry the video and audio. At the source,
a device called a headend communicates with the satellites to first receive the data.
This information is carried in real time from the source (the television studio)
down to the local sites, usually a city.This data is a one-way exchange of information
towards the subscriber, and is a live feed.Think of the evening news you
watch when you get home from work, and this is what you’ll see.
The next type of television concerns the broadcasting of previously recorded
shows, which is still a one-way exchange of data from the studio to the subscriber.
There’s no live person showing up on the screen, just a tape or DVD
being played, or some other form of stored media being played back. After you’ve
had supper in the evening and caught the news mentioned in the previous paragraph,
you might kick back in your easy chair and watch a movie.This is the
second form of television we’re accustomed to seeing.The demands on the network
haven’t changed since the presentation is still one way towards the subscriber
from the source.
Lastly, we sometimes watch public television where a talk show allows guests
from other cities to interact with the main program in order to give feedback
or ask questions. Placing the highest demands upon the broadcast network, this
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378 Chapter 10 • Designing and Implementing Single Site Solutions
scenario uses two-way video and audio, which requires massive amounts of bandwidth
on the broadcast medium.