U Reference Point

Reference point between a TE1 and an ISDN network. The U reference point understands ISDN signaling techniques and uses a 2-wire connection.

UDP

See User Datagram Protocol.

UMB

A block of upper memory made available by a 386 memory manager into which memory resident software can be loaded.

Unattended Installation

A method of installing Windows remotely with little or no user intervention. Unattended installation uses a distribution server to install Windows on a target computer. See also Distribution Server.

UNC

See Universal Naming Convention.

UNDELETE

Restores files previously deleted with the DEL command.

UNFORMAT

Restores a disk erased by the FORMAT command.

Unicast Routing

One machine sends directly to one destination address.

Unicast Scope

DHCP scope used to assign unicast (point-to-point) addresses. Compare with Multicast Address Dynamic Client Allocation Protocol (MADCAP).

Unicode

A 16-bit character code, defined by the Unicode Consortium and by ISO 10646, that supports a maximum of 65,536 unique characters rather than the 256 characters available in the current ASCII character set. By using two bytes to represent each character, Unicode allows almost all the world’s written languages to be represented in a single character set; for example, the Chinese language defines almost 10,000 basic ideographs. When universally adopted, Unicode will make multilingual software much eaasier to write and maintain. Products such as Novell NetWare and Microsoft Windows NT provide Unicode support. See also American Standard Code for Information Interchange, Double-Byte Character Set, and Extended Binary Coded Decimal Interchange Code.

Uniform Resource Locator (URL)

An Internet standard naming convention for identifying resources available via various TCP/IP application protocols. For example, http://www.microsoft .com is the URL for Microsoft’s World Wide Web server site, and ftp://gateway.dec.com is a popular FTP site. A URL allows easy hypertext references to a particular resource from within a document or mail message. See also Hypertext Transfer Protocol and World Wide Web.

Uninterruptible Power Supply (UPS)

A special battery (or sometimes a generator) that supplies power to an electronic device in the event of a power failure.

Universal Group

A scope for a group on a Windows domain controller. A universal group is used to logically organize users and appear in the global catalog (a special listing that contains limited information about every object in the Active Directory). Universal groups can contain users from anywhere in the domain tree or domain forest, other universal groups, and global groups. See also Domain Controller, Active Directory, Domain Tree, Domain Forest, and Global Group.

Universal Inbox

One inbox folder that receives incoming items from all outside sources and of all types, such as e-mail, voice mail, faxes, pages, etc.

Universal Naming Convention (UNC)

A multivendor, multiplatform convention for identifying shared resources on a network. UNC names follow the naming convention \\computername\sharename.

Universal Serial Bus (USB)

An external bus standard that allows USB devices to be connected through a USB port. USB supports transfer rates up to 12Mbps. A single USB port can support up to 127 devices.

Universally Unique Identifier (UUID)

A unique number used in newer PCs that can be used to identify a computer. The UUID can be used during the prestaging of clients for use with Remote Installation Services (RIS). See also Prestaging and Remote Installation Services (RIS).

UNIX

A multitasking operating system, created by AT&T’s Bell Labs, that is used on a wide variety of computers including Internet servers. See also Multitasking and Internet.

Unnumbered Frames

HDLC frames used for control-management purposes, such as link startup and shutdown or mode specification.

Unshielded Twisted-Pair (UTP)

Copper wiring used in small-to-large networks to connect host devices to hubs and switches. Also used to connect switch to switch or hub to hub.

Unspecified Bit Rate

Abbreviated UBR. A type of Asynchronous Transfer Mode (ATM) service that provides spare bandwidth to noncritical services such as file transfers. See also Asynchronous Transfer Mode, Available Bit Rate, Constant Bit Rate and Variable Bit Rate.

Update Sequence Number (USN)

When a change is made to the database stored on a domain controller – either through a user action or through replication from another domain controller – the domain controller assigns the change an update sequence number (USN). Each domain controller keeps its own USNs and increments the value for each change that occurs. With respect to a single domain controller, you can think of the USN as a change counter. Each domain controller will have different values for changes that occur on its copy of the directory database. These values are not synchronized between domain controllers within a domain.

Upgrade

A method for installing Windows that preserves existing settings and preferences when converting to the newer operating system.

Upgrade Pack

Software in the form of a migration DLL (dynamic link library) used with applications that need to be upgraded to work with Windows.

Upgrade Report

A report generated by the Setup program that summarizes any known compatibility issues that you might encounter during the upgrade. The Upgrade Report can be saved as a file or printed.

Upper Memory

The 384KB of memory between the top of conventional memory and the end of the base memory.

UPS

See Uninterruptible Power Supply.

URL

See Uniform Resource Locator.

USB

See Universal Serial Bus.

UseNet

A massive distributed database of news feeds and special interest groups maintained on the Internet and accessible through most Web browsers.

User

1. Anyone who requests network resources. In most cases, you assign a unique username and password to every individual on your network.
2. In Active Directory, this is a security principal (a user who can log on to the domain). A user may have an e-mail address and/or an Exchange mailbox, making the object mail-enabled and/or mailbox-enabled, respectively.

User Datagram Protocol (UDP)

The User Datagram Protocol (UDP) is a connectionless Transport (host-to-host) layer protocol. UDP does not provide message acknowledgements; rather, it simply transports datagrams. UDP operates at the Transport layer of the OSI model. See also Transmission Control Protocol.

User Manager

A Windows application that administers user accounts and manages policies.

User Manager for Domains

A Windows NT application that administers user accounts, groups, and security policies at the domain level.

Username

A user’s account name in a logon-authenticated system. See also Security.

User Object

An Active Directory object that is a security principal and that identifies individuals that can log on to a domain.

User Principal Name (UPN)

A multi-valued attribute of each user object that the system administrator can set. A UPN allows the underlying domain structure and complexity to be hidden from users; for example, although 50 domains may exist within a forest, users would seamlessly log on as if they were in the same domain. For consistency purposes, system administrators can make the UPN and users’ SMTP address the same.

User Profile

A collection of information for MAPI client configuration that specifies the services a user wants to use and how MAPI client applications are to look and behave. See also Roaming User Profile and Mandatory User Profile.

User Rights Policies

Used to determine what rights users and groups have when trying to accomplish network tasks. User Rights Policies are set through User Manager for Domains. See also User Manager for Domains.

Users Group

A Windows built-in group that includes end users who should have very limited system access. After a clean installation of Windows, the default settings for this group prohibit users from compromising the operating system or program files. By default, all users who have been created on the computer, except Guest, are members of the Users group.

USN

See Update Sequence Number.

Utility Manager

A Windows utility used to manage the three accessibility utilities: Magnifier, Narrator, and On-Screen Keyboard. See also Magnifier, Narrator, and On-Screen Keyboard.

UTP

See Unshielded Twisted-Pair.

UUENCODE

Stands for UNIX-to-UNIX Encode, and is a protocol used to encode binary information within mail messages. UUENCODE is older than MIME. See also MIME.