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280 Glossary of Terms
Term Definition
or receives any data.
TLS is application protocol-independent. Higher-level protocols can layer on top of the
TLS protocol transparently. Based on Netscape’s SSL 3.0, TLS supersedes and is an
extension of SSL. TLS and SSL are not interoperable. See also, Protocol and SSL.
Translation See IP Address Translation.
Tunneling A technology that enables one network to send its data via another network's
connections. Tunneling works by encapsulating a network protocol within packets
carried by the second network. For example, Microsoft's PPTP technology enables
organizations to use the Internet to transmit data across a Virtual Private Network
(VPN). It does this by embedding its own network protocol within the TCP/IP packets
carried by the Internet. See also, TCP/IP and VPN.
ToS (Type of Service) A field within an IP header which can be used by the device originating
the packet, or by an intermediate networking device, to signal a request for a specific
QoS level. ToS uses three bits to tell a router how to prioritize a packet and one bit
apiece to signal requirements for delay, throughput, and reliability. See also, Packet,
QoS, Router, and Throughput.
URL (Uniform Resource Locator) The standard method used for identifying the location of
information available to the Internet. This is effectively the “address” of a document or
file, expressed in the form: protocol://domain.filename/path.type (for example,
http://www.myfile.com/nextpage.html).
UTC (Coordinated Universal Time) A time scale that couples Greenwich Mean Time (GMT),
which is based solely on the Earth's inconsistent rotation rate, with highly accurate
atomic time. When atomic time and Earth time approach a one second difference, a
leap second is calculated into UTC. UTC was devised on January 1, 1972 and is
coordinated in Paris by the International Bureau of Weights and Measures. UTC, like
GMT, is set at 0 degrees longitude on the prime meridian
VoIP (Voice over IP) An emerging technology for transporting integrated digital voice, video,
and data over IP networks. A major advantage of VoIP and Internet telephony is that it
avoids the tolls charged by ordinary telephone services. See also, Internet and IP.
VPN (Virtual Private Network) A network that is constructed by using public wires to connect
nodes. For example, there are a number of systems that enable you to create networks
using the Internet as the medium for transporting data. These systems use encryption
and other security mechanisms to ensure that only authorized users can access the
network and that the data cannot be intercepted.
VxWorks ® A real-time operating system, manufactured and sold by Wind River Systems of
California, USA. VxWorks program development requires a host machine running Unix
or Windows.
W3C (World Wide Web Consortium) An international consortium of companies involved with
the Internet and the Web. The organization's purpose is to develop open standards so
that the Web evolves in a single direction rather than being splintered among
competing factions. The W3C is the chief standards body for HTTP and HTML. See also,
HTML and HTTP.
WAN (Wide Area Network) Take two local area networks, hook them together, and you've got
a WAN. Wide area networks can be made up of interconnected smaller networks spread
throughout a building, a state, a country, or the entire globe.