Audio
Streaming
Network Protocols
Designing a
network protocol which supports streaming media can be quite involved.
The following
issues are noteworthy:
Protocols called
Datagram, such as the User Datagram Protocol, send the media stream as
a series
of small components of data. Although this is simple and efficient, the
protocol does not contain any provision to guarantee delivery of the
data
stream. In fact, the onus is placed on the user to detect any loss or
corruption in the data, and to reinstate such data using error
correction
methods. If some of the data is lost, the media stream may incur what
is called
a dropout.
The following
protocols have been particularly designed to deliver streaming media
over
networks:
Real-time
Streaming Protocol, Real-time Transport Protocol, and the Real-time
Transport
Control Protocol.
Dependable
protocols, such as the Transmission Control Protocol, ensure the
correct
delivery of each bit in the media stream. However, in order to achieve
this,
they use a system of timeouts and retries, which makes them more
complex to
implement. The downside is that when the network suffers from is a loss
of
data, the media stream is put on hold while the protocol handlers
detect the
loss and retransmit the missing data. By buffering the display data, it
is
possible to reduce this effect quite noticeably.
When using
Unicast protocols, an alternative copy of the data stream is sent from
the
server to each user. Unicast is most commonly used for most Internet
connections. However, it does not perform well when large numbers of
users want
to view the same program at the same time. When there are many
recipients
receiving Unicast content streams independently, there tends to be data
replication with consequent server/network loads. Even when the
streaming
content is the same as that provided by the associated streaming
server, there
will still be a requirement for multiple connections from the Unicast
Connections.
However,
Multicast protocols were developed in order to minimise this sort of
replication. Such protocols send just one stream from the source to a
group of
recipients. Whether Multicast transmissions are feasible depends on the
network
infrastructure and type. One possible downside of multicasting is the
loss of
the ability to utilise video on demand. In the case of continuously
streaming
radio or television material, the user will be unable to control
playback. The
use of servers with the ability to cache, digital set top boxes, and
buffered
media players are all methods which will tend to limit this problem.
The ability to
send a single data stream to a number of end users on a computer
network is
available with IP Multicast. Since routers and firewalls must allow the
flow of
data destined for multicast groups, this must be considered when
deploying IP
multicast.
In the case of
educational, government, and corporate intranets where the organization
that is
serving the content has control over the network between server and
recipients,
then routing protocols such as IGMP and PIM can be used to deliver
stream
content to multiple LAN segments.
Arranging for pre-recorded
streams to be sent between computers forms the basis for Peer-to-peer
(P2P)
protocols. In this way, the server and its network connections are free
from
experiencing bottlenecks. There are, however, certain matters that may
need to
be resolved when using of such an arrangement. These include technical,
effectiveness, accuracy of data, and various legal issues
Audio
Streaming – How To Succeed
Peter
Radford writes Articles with Websites on a
wide range of subjects. Audio Streaming
Articles cover History, Development, Multimedia, Protocols.
His Website
contains
over 60 Audio Streaming Articles
View his Website
at: audio-streaming-how-to-succeed.com
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