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AXIS P3301/AXIS P3304 - Glossary of Terms
server may contain any number of server and client
programs. A web server is the computer program that
supplies the requested HTML pages or files to the client
(browser).
Sharpness -
This is the control of fine detail within a
picture. This feature was originally introduced into color
TV sets that used notch filter decoders. This filter took
away all high frequency detail in the black and white
region of the picture. The sharpness control attempted to
put some of that detail back in the picture. Sharpness
controls are mostly superfluous in today's high-end TVs.
The only logical requirement for it nowadays is on a VHS
machine.
Simplex -
In Simplex operation, a network cable or
communications channel can only send information in one
direction.
SMTP (Simple Mail Transfer Protocol) -
SMTP is used for
sending and receiving e-mail. However, as it is ‘simple,’ it
is limited in its ability to queue messages at the receiving
end, and is usually used with one of two other protocols,
POP3 or IMAP. These other protocols allow the user to save
messages in a server mailbox and download them
periodically from the server.
SMTP authentication is an extension of SMTP, whereby
the client is required to log into the mail server before or
during the sending of email. It can be used to allow
legitimate users to send email while denying the service to
unauthorized users, such as spammers.
SNMP (Simple Network Management Protocol) -
SNMP
forms part of the Internet Protocol suite, as defined by the
Internet Engineering Task Force. The protocol can support
monitoring of network-attached devices for any conditions
that warrant administrative attention.
Sockets -
Sockets are a method for communication
between a client program and a server program over a
network. A socket is defined as ‘the endpoint in a
connection.’ Sockets are created and used with a set of
programming requests or ‘function calls’ sometimes called
the sockets application programming interface (API).
SSL/TSL (Secure Socket Layer/Transport Layer Security)
These two protocols (SSL is succeeded by TSL) are
cryptographic protocols that provide secure
communication on a network. SSL is commonly used over
HTTP to form HTTPS, as used e.g. on the Internet for
electronic financial transactions. SSL uses public key
certificates to verify the identity of the server.
Subnet/subnet mask -
A subnet is an identifiably separate
part of an organization's network. Typically, a subnet may
represent all the machines at one geographic location, in
one building, or on the same local area network (LAN).
Having an organization's network divided into subnets
allows it to be connected to the Internet with a single
shared network address.
The subnet mask is the part of the IP address that tells a
network router how to find the subnet that the data packet
should be delivered to. Using a subnet mask saves the
router having to handle the entire 32-bit IP address; it
simply looks at the bits selected by the mask.
Switch -
A switch is a network device that connects
network segments together, and which selects a path for
sending a unit of data to its next destination. In general, a
switch is a simpler and faster mechanism than a router,
which requires knowledge about the network and how to
determine the route. Some switches include the router
function. See also
Router
.
TCP (Transmission Control Protocol) -
TCP is used along
with the Internet Protocol (IP) to transmit data as packets
between computers over the network. While IP takes care
of the actual packet delivery, TCP keeps track of the
individual packets that the communication (e.g. requested
a web page file) is divided into, and, when all packets have
arrived at their destination, it reassembles them to re-form
the complete file.
TCP is a connection-oriented protocol, which means that a
connection is established between the two end-points and
is maintained until the data has been successfully
exchanged between the communicating applications.
Telnet -
Telnet is a simple method with which to access
another network device, e.g. a computer. The HTTP
protocol and the FTP protocols allow you to request
specific files from remote computers, but do not allow you
logon as a user of that computer. With Telnet, you log on
as a regular user with whatever privileges you may have
been granted for specific applications and data residing on
that computer.
UDP (User Datagram Protocol) -
UDP is a communications
protocol that offers limited service for exchanging data in
a network that uses the Internet Protocol (IP). UDP is an
alternative to the Transmission Control Protocol (TCP). The
advantage of UDP is that it is not required to deliver all
data and may drop network packets when there is e.g.
network congestion. This is suitable for live video, as there
is no point in re-transmitting old information that will not
be displayed anyway.
Unicast -
Communication between a single sender and a
single receiver over a network. A new connection is
established for each new user.
URL (Uniform Resource Locator) -
An "address" on the
network.
Varifocal lens -
A varifocal lens provides a wide range of
focal lengths, as opposed to a lens with a fixed focal
length, which only provides one.
VPN (Virtual Private Network) -
This creates a secure
"tunnel" between the points within the VPN. Only devices
with the correct "key" will be able to work within the VPN.
The VPN network can be within a company LAN (Local
Area Network), but different sites can also be connected
over the Internet in a secure way. One common use for
VPN is for connecting a remote computer to the corporate
network, via e.g. a direct phone line or via the Internet.
VOP (Video Object Plane) -
A VOP is an image frame in an
H.264 video stream. There are several types of VOP:
- An I-VOP is complete image frame.
- A P-VOP codes the differences between images, as long
as it is more efficient to do so. Otherwise it codes the whole
