Vaccination

A technique of some anti-virus programs to store information about files in order to notify the user about file changes. Internal vaccines store the information within the file itself, while external vaccines use another file to verify the original for possible changes.

Vampire Tap

A specific type of Ethernet transceiver on a Thicknet network. The vampire tap does not break the Thicknet cable, but instead pierces the jacket of the cable to contact the center conductor.

Variable Bit Rate (VBR)

A connection-oriented Asynchronous Transfer Mode service for real-time applications for which minor data loss is acceptable, and for non-real-time VBR applications such as transaction processing. See also Asynchronous Transfer Mode, Available Bit Rate, Constant Bit Rate, and Unspecified Bit Rate.

Variable-Length Subnet Mask (VLSM)

Helps optimize available address space and specify a different subnet mask for the same network number on various subnets. Also commonly referred to as “subnetting a subnet.”

Variant

A modified version of a virus. Usually produced on purpose by the virus author or another person amending the virus code. If changes to the original are small, most anti-virus products will also detect variants. However, if the changes are large, the variant may go undetected by anti-virus software.

VBR

See Variable Bit Rate.

VBS

See Visual Basic Script.

VBSQL

One of the interfaces provided with the native API of SQL Server. VBSQL is designed for use from Visual Basic and Visual Basic for Applications (VBA) applications.

VCC

See Virtual Channel Connection.

VDM

See Virtual DOS Machine.

VER

Displays the MS-DOS version.

VERIFY

Directs MS-DOS to verify that your files are written correctly to a disk.

Version ID

An internal record used to identify which server in a replication partnership has the more recent version of a registration.

Vertical Partitioning

In SQL Server replication, a method by which you can publish only certain columns of a table. This is often referred to as a vertical filter. See also Horizontal Partitioning.

VFAT

An extension of the FAT file system; VFAT allows long filenames up to 255 characters. Windows 95 and Windows NT use the VFAT file system.

VGA

Video Graphics Array; has all modes of EGA, but with 16 colors.

Video Adapter

The hardware device that outputs the display to the monitor.

View

In SQL Server, an object that is usually created to exclude certain columns from a table or to link two or more tables together. A view appears very much like a table to most users.

VIP

See Virtual IP.

Virtual Channel Connection (VCC)

A logical circuit that is created by VCLs. VCCs carry data between two endpoints in an ATM network. Sometimes called a virtual circuit connection.

Virtual Circuit

The logical connection made between two devices across a shared communications path. There is no dedicated physical circuit between the devices, even though they are acting as though there is one.

Virtual Circuit Packet Switching

Virtual circuits operate by establishing a formal connection between two devices in communication. When devices begin a session, they negotiate communication parameters, such as maximum message size, communication windows, and network paths. This negotiation establishes a virtual circuit, which is a well-defined path through the internetwork by which the devices communicate. This virtual circuit generally remains in effect until the devices stop communicating.

Virtual DOS Machine (VDM)

The DOS environment created by Windows NT for the execution of DOS and Win16 applications. See also Microsoft Disk Operating System and Win16.

Virtual Interface Processor (VIP)

An interface card for Cisco 7000 and 7500 series routers, providing multilayer switching and running the Cisco IOS software. The most recent version of VIP is VIP2.

Virtual IP (VIP)

A function making it possible for logically separated switched IP workgroups to run Virtual Networking Services across the switch ports of a Catalyst 5000.

Virtual LAN

A group of devices on one or more logically segmented LANs (configured by use of management software), enabling devices to communicate as if attached to the same physical medium, when they are actually located on numerous different LAN segments. VLANs are based on logical instead of physical connections and thus are tremendously flexible.

Virtual Memory

A kernel service that stores memory pages not currently in use on a mass storage device to free up the memory occupied for other uses. Virtual memory hides the memory swapping process from applications and higher level services. See also Swap File and Kernel.

Virtual Private Network (VPN)

A private network that uses links across private or public networks (such as the Internet). When data is sent over the remote link, it is encapsulated, encrypted, and requires authenticating services.

Virtual Ring

In an SRB network, a logical connection between physical rings, either local or remote.

Virtual Root

A shortcut pointer to a physical storage location. Virtual roots are normally defined to allow users and applications to connect with a short “friendly” path instead of navigating a complex heirarchy. Internet Information Server (IIS) uses the concept of virtual roots to expose resources provided by a Web server.

Virtual Server

An instance of any service type normally implemented in IIS. For example, a virtual server can be an instance of FTP, IMAP, Instant Messaging (RVP), HTTP, NNTP, POP, or SMTP. An Exchange 2000 server can host multiple virtual servers of the same type on each computer. Each virtual server can have its own configuration properties, such as bound IP addresses, port number, and authentication type.

Viruses

Viruses are created intentionally with the aim of injuring or altering your machines. Viruses can be spread through computer systems in many ways, but the most common is through an executable file.

Virus Hoaxes

Hoaxes are not viruses, but are usually deliberate or unintentional e-messages warning people about a virus or other malicious software program. Some hoaxes cause as much trouble as viruses by causing massive amounts of unnecessary e-mail. Most hoaxes contain one or more of the following characteristics:

• Warnings about alleged new viruses and its damaging consequences
• Demands the reader forward the warning to as many people as possible
• Pseudo-technical "information" describing the virus
• Bogus comments from officials: FBI, software companies, news agencies, etc.

Visual Basic Script (VBS)

Visual Basic Script is a programming language that can invoke any system function – including starting, using and shutting down other applications – without user knowledge. VBS programs can be embedded in HTML files and provide active content via the Internet. Since not all content is benign, users should be careful about changing security settings without understanding the implications. This file type has the extension VBS.

VLAN

See Virtual LAN.

VLAN Trunk Protocol (VTP)

Used to update switches in a switch fabric about VLANs configured on a VTP server. VTP devices can be a VTP server, client, or transparent device. Servers update clients. Transparent devices are only local devices and do not share information with VTP clients. VTPs send VLAN information down trunked links only.

VLSM

See Variable-Length Subnet Mask.

Voice Mail

The storage and movement of voice messages.

VOL

Displays a disk volume label and serial number.

Volume

A collection of data indexed by directories containing files and referred to by a drive letter. Volumes are normally contained in a single partition, but volume sets and stripe sets extend a single volume across multiple partitions.

Volume

A storage area on a Windows dynamic disk. Dynamic volumes cannot contain partitions or logical drives. Windows dynamic storage supports three dynamic volume types: simple volumes, spanned volumes, and striped volumes. Dynamic volumes are accessible only to Windows 2000 and later operating systems; they are not accessible through DOS, Windows 9x, or Windows NT.

Volume Label

An identifying label written to a disk when a disk is first formatted.

VPN

See Virtual Private Network.

VSAFE

Continuously monitors your computer for viruses.

VTP

See VLAN Trunk Protocol.