Glossary: CCNA & General Networking Terms 


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User Agent. An OSI application process that represents a human user or organization in the X.400 Message Handling System. Creates, submits, and takes delivery of messages on the user's behalf. [Source: RFC1208]
Unsolicited Bulk Email.
Unsolicited Commercial Email.
Universities and Colleges Information Systems Association, with several subgroups, including UCISA-NG, the Networking Group (which is an Affiliated Group of the JANET National User Group).
See: User Datagram Protocol
University for industry, not strictly a University, nor for Industry.
UHI Network
University of Highlands and Islands Network.
the UK Education and Research Networking Association; funded by the Joint Information Systems Committee of the Higher Education Funding Councils and others to manage the academic network and its developments. Formerly the JNT.
University of London Computer Centre, CCNA of various networking facilities.
An address which only one host will recognize. See also: broadcast, multicast. [Source: RFC1983]
Uniform Resource Locator (URL)
A URL is a compact (most of the time) string representation for a resource available on the Internet. URLs are primarily used to retrieve information using WWW. The syntax and semantics for URLs are defined in RFC 1738. See also: World Wide Web. [Source: RFC1983]
Universal Time Coordinated (UTC)
This is Greenwich Mean Time. [Source: MALAMUD]
This was initially a program run under the UNIX operating system that allowed one UNIX system to send files to another UNIX system via dial-up phone lines. Today, the term is more commonly used to describe the large international network which uses the UUCP protocol to pass news and electronic mail. See also: Electronic Mail, Usenet. [Source: RFC1392]
Unrouteable Address
Certain ranges of IP addresses are designated in RFC 1918 as exclusively for internal use. These are to, to, and to A correctly configured router will not allow packets from any of these addresses through to the Internet. The only way that information can pass between hosts with any of these IP addresses and the outside world is to have a device (typically a firewall) that translates between these internal addresses and a specific collection of IP addresses that are assigned in the normal way. The internal IP addresses can be safely re-used in many such locations. See also: Network Address Translation, IP Address.
urban legend
A story, which may have started with a grain of truth, that has been embroidered and retold until it has passed into the realm of myth. It is an interesting phenonmenon that these stories get spread so far, so fast and so often. Urban legends never die, they just end up on the Internet! Some legends that periodically make their rounds include "The Infamous Modem Tax," "Craig Shergold/Brain Tumor/Get Well Cards," and "The $250 Cookie Recipe". [Source: LAQUEY]
See: Uniform Resource Locator
A collection of thousands of topically named newsgroups, the computers which run the protocols, and the people who read and submit Usenet news. Not all Internet hosts subscribe to Usenet and not all Usenet hosts are on the Internet. See also: Network News Transfer Protocol, UNIX-to-UNIX CoPy. [Source: NWNET]
User Datagram Protocol (UDP)
An Internet Standard transport layer protocol defined in STD 6, RFC 768. It is a connectionless protocol which adds a level of reliability and multiplexing to IP. See also: connectionless, Transmission Control Protocol. [Source: RFC1392]
See: Universal Time Coordinated
See: UNIX-to-UNIX CoPy
A program which reverses the effect of uuencode. See also: uuencode. [Source: RFC1983]
A program which reversibly converts a binary file in ASCII. It is used to send binary files via email, which generally does not allow (or garbles) the transmission of binary information. The original binary can be restored with uudecode. The encoding process generally creates an ASCII file larger than the original binary, so compressing the binary before running uuencode is highly recommended. [Source: RFC1983]


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