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IP addresses
Each device on a LAN (Local Area
Network) must have a unique address.
This is commonly called the "IP
address". An IP address consists of
four numbers separated by a dot ".",
each number is in the range 0-255.
For example, the address could be
"192.36.253.80". The first three
groups of digits will be common to
all devices connected to the same
segment, which means that all units
within the same segment will have a
common address beginning with
192.36.253.
Data
transport protocols for network
video
The most common protocol for
transmitting data on computer
networks today is the TCP/IP
Protocol suite. TCP/IP acts as a
"carrier" for many other protocols;
a good example is HTTP (Hyper Text
Transfer Protocol), which is used to
browse Web pages on servers around
the world using the Internet.
TCP/IP protocols and ports used for
network video
Common protocols and their port
numbers used for the transfer of
network video include:
|
Protocol |
Transport protocol |
Port |
Common usage |
Network video usage |
FTP
File Transfer Protocol |
TCP |
21 |
Transfer of files over the
Internet/intranets |
Transfer of images or video
from network camera/video
server to an FTP server or
to an application |
SMTP
Send Mail Transfer Protocol |
TCP |
25 |
Protocol for sending e-mail
messages |
A network camera/video
server can send images or
alarm notifications using
its built-in e-mail client |
HTTP
Hyper Text Transfer Protocol |
TCP |
80 |
Used to browse the Web, i.e.
to retrieve Web pages from
Web servers |
The most common way to
transfer video from a
network camera/video server
where the network video
device essentially works as
a Web server, making the
video available for the
requesting user or
application server |
HTTPS
Hypertext Transfer Protocol
over Secure Socket Layer |
TCP |
443 |
Used to access Web pages
securely using encryption
technology |
Secure transmission of video
from network cameras/video
servers can also be used to
authenticate the sending
camera using X.509 digital
certificates |
RTP
Real Time Protocol |
UDP/TCP |
Not defined |
RTP standardized packet
format for delivering audio
and video over the Internet.
Often used in streaming
media systems or
videoconferencing. |
A common way of transmitting
MPEG-based network video
Transmission can be either
unicast (one to one) or
multicast (one to many) |
IP
uses two transport protocols:
Transmission Control Protocol (TCP)
and User Datagram Protocol (UDP).
TCP provides a reliable,
connection-based transmission
channel; it handles the process of
breaking large chunks of data into
smaller packets, suitable for the
physical network being used, and
ensures that data sent from one end
is received on the other. UDP, on
the other hand, is a connectionless
protocol and does not guarantee the
delivery of data sent, thus leaving
the whole control mechanism and
error-checking to the application
itself.
Transmission methods for network
video: Unicasting, Multicasting, and
Broadcasting
There
are different methods for
transmitting data on a computer
network:
-
Unicast - the sender and the
recipient communicate on a
point-to-point basis. Data
packets are sent addressed
solely to one recipient and no
other computers on the network
will need to process this
information.
-
Multicast - communication
between a single sender and
multiple receivers on a network.
Multicast technologies are used
to reduce network traffic when
many receivers want to view the
same source simultaneously by
delivering a single stream of
information to hundreds of
recipients. The biggest
difference compared with
unicasting is that the video
stream only needs to be sent
once. Multicasting (i.e
IP-Multicasting) is commonly
used in conjunction with RTP
transmissions.
-
Broadcast - a one-to-everybody
transmission. On a LAN,
broadcasts are normally
restricted to a specific network
segment and are not in practical
use for network video
transmissions.
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