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AXIS 233D - Glossary
RS-485 - An upgraded version of RS-422 that supports
up to 32 devices on the same connection. RS-485 is an
electrical specification of a two-wire, half-duplex,
multipoint serial connection. It enables the configuration
of inexpensive local networks and multidrop
communications links. It offers high data transmission
speeds (up to 10Mbit/s), and as it uses a differential
balanced line over twisted pair (like RS-422), it can span
relatively large distances (4000 feet or 1200 meters).
RS-485 only specifies the electrical characteristics of the
driver and the receiver. It does not specify or recommend
any data protocol.
RTCP (Real-Time Control Protocol) - RTCP provides
support for real-time conferencing of groups of any size
within an intranet. This support includes source
identification and support for gateways like video bridges
as well as multicast-to-unicast translators. It offers
quality-of-service feedback from receivers to the
multicast group as well as support for the synchronization
of different media streams.
RTP (Real-Time Transport Protocol) - An Internet
protocol for the transport of real-time data, such as video.
It can be used for media-on-demand as well as interactive
services such as Internet telephony.
RTSP (Real Time Streaming Protocol) - A control
protocol, and a starting point for negotiating transports
such as RTP, multicast and unicast, and for negotiating
codecs. RTSP can be considered a “remote control” for
controlling the media stream delivered by a media server.
RTSP servers typically use RTP as the protocol for the
actual transport of video data.
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.
Security surveillance - Network video's advanced
functionality makes it highly suited to the applications
involved in security surveillance. The flexibility of digital
technology enhances security personnel's ability to
protect people, property and assets. Such systems are
therefore an especially attractive option for companies
currently using CCTV.
Server - In general, a server is a computer program that
provides services 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
(web browser).
SMTP (Simple Mail Transfer Protocol) - 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 - An extension of SMTP, where 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 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