User's Manual

Glossary 93
UDP (User Datagram Protocol) A communications method that uses the Internet
Protocol (IP) to send a data unit (called a datagram) from one computer to another in a
network. Network applications that have very small data units to exchange may use
UDP rather than TCP.
unicast The one-to-one form of streaming. If RTSP is provided, the user can move
freely from point to point in an on-demand movie.
UTC (universal time coordinated) A standard reference time. UTC is based on an
atomic resonance, and clocks that run according to UTC are often called “atomic
clocks.”
VPN (Virtual Private Network) A network that uses encryption and other technologies
to provide secure communications over a public network, typically the Internet. VPNs
are generally cheaper than real private networks using private lines but rely on having
the same encryption system at both ends. The encryption may be performed by
firewall software or by routers.
WAN (wide area network) A network maintained across geographically separated
facilities, as opposed to a LAN (local area network) within a facility. Your WAN interface
is usually the one connected to the Internet.
wildcard A range of possible values for any segment of an IP address.
WINS (Windows Internet Naming Service) A name resolution service used by
Windows computers to match client names with IP addresses. A WINS server can be
located on the local network or externally on the Internet.
zone transfer The method by which zone data is replicated among authoritative DNS
servers. Slave DNS servers request zone transfers from their master servers to acquire
their data.
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