Appendices
IP Video Door Station DS06M(P) Operation User Manual
86
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
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.
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.
Time to live (TTL)
is mechanism that limits the lifespan of data in a computer or network.
TTL may be implemented as a counter or timestamp attached to or embedded in the data. Once
the prescribed event count or timespan has elapsed, data is discarded. In computer networking,
TTL prevents a data packet from circulating indefinitely. In computing applications, TTL is used to
improve performance of caching or improve privacy.
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.
Universal Plug and Play (UPnP)
is a set of networking protocols for primarily residential
networks without enterprise class devices that permits networked devices, such as personal
computers, printers, Internet gateways, Wi-Fi access points and mobile devices to seamlessly
discover each other's presence on the network and establish functional network services for data
sharing, communications, and entertainment.
Uniform Resource Locator or Unified Resource Locator (URL)
is a character string that
specifies where a known resource is available on the Internet and the mechanism for retrieving it.
Wireless Application Protocol (WAP)
is a technical standard for accessing information
over a mobile wireless network. A WAP browser is a web browser for mobile devices such as
mobile phones (called "cellular phones" in some countries) that uses the protocol.
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.