Oracle Video server, Manual

Page: 26 / 78

Where is Digital Video Used?
1-12 Introducing Oracle Video Server
■
Home shopping
■
Home financial services
■
Medical diagnostics
Asynchronous Transfer Mode (ATM)
Broadband deployment of streamed digital video often uses the Asynchronous
Transfer Mode
(ATM) networking protocol for video delivery. ATM provides a
reliable mechanism for high-speed delivery of large amounts of highly complex
data, using fixed-size delivery packets called cells. Because of its switched,
connection-oriented nature and its fixed cell size of 53 bytes, ATM is an inherently
reliable, scalable networking technology.
ATM can offer several advantages over other networking protocols, including:
■
scalability, to work at different speeds and on different media
■
open-ended growth paths, since ATM is not tied to any physical medium or
speed
■
a single network for delivery of voice, data, and video, thereby improving
efficiency and manageability
■
compatibility with existing physical networks (because ATM is not dependent
on a specific type of physical transport)
In some cases the ATM network is used only for delivery of the video data itself,
and another network is used to deliver system messages between the client and
server. The second network often has less bandwidth than the video network; for
example, using Internet Protocol (IP) over a telephone line.
Digital Subscriber Line (DSL) Transport Systems
One emerging way of delivering video is through DSL (Digital Subscriber Line)
transport systems. DSL was originally intended by telephone companies as a way
to deliver both television and telephone service over existing copper telephone
lines. Using the same copper wires on which much existing telephone service is
based, DSL can provide data access and downloading up to 50 times faster than a
28.8 Kbps modem.
DSL is actually a continuum of a variety of transport systems that can carry about 1
to 6 Mbps. In general, the faster the DSL, the shorter the distance it can reliably
cover. The fastest DSLs can cover only a few miles; the slowest can cover farther.