User Guide

44
AXIS 209FD/FD-R/FD-R M12
Router - A device that determines the next network point to which a
packet should be forwarded on its way to its final destination. A
router creates and/or maintains a special routing table that stores
information on how best to reach certain destinations. A router is
sometimes included as part of a network switch. See also switch.
Server - In general, a server is a computer program that provides
se
rvices to other computer programs in the same or other computers.
A computer running a server program is also frequently referred to as
a server. In practice, the 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 origina
lly 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
c
hannel can only send information in one direction.
SMTP (Simple Mail Transfer Protocol) - SMTP is used for sending
a
nd 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
re
quired to log into the mail server before or during the sending of
mail. 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
p
rogram 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 Laye
r Security)
These two protocols (SSL is succeeded by TSL) are cryptographic
p
rotocols 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
o
rganization'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
se
gments 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
Interne
t 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
conne
ction 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
netwo
rk 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.
TVL (TV Lines) - A method of defining resolutions in analog video.
UDP (User Datagram Protocol) - UDP is a communications protocol
tha
t 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
recei
ver over a network. A new connection is established for each
new user.
URL (Uniform Resource Locator) - An “address” on the network.
USB - (Universal Serial Bus) A plug-and-play interface between a
computer and perip
heral devices, e.g. scanners, printers, etc.
Varifocal lens - A varifocal lens provides a wide range of focal
lengths, a
s opposed to a lens with a fixed focal length, which only
provides one.
VPN (Virtual Private Network) - This creates a secure “tunnel”
betwe
en 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 MPEG-4
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
eff
icient to do so. Otherwise it codes the whole image, which may also
be a completely new image.
WAN (Wide-Area-Network) - Similar to a LAN, but on a larger
geogra
phical scale.
W-LAN (Wireless LAN) - A wireless LAN is a wireless local area
netwo
rk that uses radio waves as its carrier: where the network
connections for end-users are wireless. The main network structure
usually uses cables.
Web server - A Web server is a program, which allows Web
browsers to
retrieve files from computers connected to the Internet.
The Web server listens for requests from Web browsers and upon
receiving a request for a file sends it back to the browser.
The primary function of a Web server is to serve pages to other
remote
computers; consequently, it needs to be installed on a
computer that is permanently connected to the Internet. It also
controls access to the server whilst monitoring and logging server
access statistics.
WEP (Wireless Equivalent Privacy) - A wireless security protocol,
s
pecified in the IEEE 802.11 standard, which is designed to provide a
wireless local area network (WLAN) with a level of security and
privacy comparable to that usually expected of a wired LAN. Security
is at two different levels; 40-bit and 128-bit encryption. The higher
the bit number, the more secure the encryption.
WINS (Windows Internet Naming Service) - Part of the Microsoft
Windows NT Se
rver, WINS manages the association of workstation
names and locations with IP addresses, without the user or
administrator having to be involved in each configuration change.