gloss_V

V

V.21.

V.21 is the modem standard for the trunk interface between a network access device and a packet network. It defines signalling data rates greater than 19.2Kbits/sec.

V.22, V.22 bis.

V.22 is a 1,200-bps duplex modem for use in the public-switched telephone network and on leased circuits. V.22bis is a 2,400-bit modem that uses frequency division multiplexing for use on the public telephone network and on point-to-point leased lines. (The CCITT uses "bis" to denote the second in a series of related standards and "ter" to denote the third in a family.)

V.32, V.32 bis.

V.32 are two-wire duplex modems operating at rates up to 9,600bps (with fallback to 4,800bps) for use in the public telephone network and on leased lines. V.32 bis offers speeds in increments of 4800bps, 7200bps, 9,600bps, 12,000bps, and 14,400bps.

V.34.

Modems that comply with the V.34 standard can operate at rates as high as 28,800bps.

V.35.

Prior to 1988, V.35 was a modem specification that provided data transmission speeds up to 48Kbits/sec. V.35 was then deleted from the V-Series Recommendations.

V.42 error correction, V.42 bis data compression.

The V.42 error-correction standard for modems specifies the use of both MNP4 and LAP-M protocols. V.22, V.22 bis, V.26 ter, and V.32 bis may be used with V.42. With V.42 bis compression, data is compressed at a ratio of about 3.5 to 1, which can yield file-transfer speeds of up to 9,600bps on a 2,400-bps modem. Manufacturers can provide an option that will allow a V.42 bis modem to monitor its compression performance and adjust the ratio accordingly .

value-added reseller (VAR).

Also called an integrator, a VAR is a company that resells manufacturers' products and adds value by installing or customizing the system.

VAX.

Digital Equipment's brand name for its line of minicomputer and workstation hardware is VAX.

vertical wiring subsystem.

The vertical wiring subsystem is the part of the structured wiring system that connects the campus wiring system to the departmental wiring system. It runs in a building's risers.

VINES.

Banyan's NOS based on a Unix core and TCP/IP protocols. VINES supports DOS, Windows, Mac, and OS/2 clients and is especially popular in large enterprise networks. Its crowning feature is StreetTalk, its distributed directory service.

virtual circuit.

A virtual circuit is a shared communications link that appears to the customer as a dedicated circuit. A virtual circuit passes packets sequentially between devices.

Virtual Terminal (VT).

VT is the OSI terminal-emulation protocol.

virus.

A virus has the ability to reproduce by modifying other programs to include a copy of itself. Several types of viruses exist. Bacteria or rabbits do not explicitly damage files but do reproduce and eat up disk space or RAM. A logic bomb lies dormant in a piece of code or program until a predefined condition is met, at which time some undesirable effect occurs. A password catcher mimics the actions of a normal log-on but catches user IDs and passwords for later use. A Trojan horse is a program that appears to function but also includes an unadvertised and malicious feature. A worm scans a system for available disk space in which to run, thereby tying up all available space.

VMS.

VMS is Digital Equipment's proprietary operating system for the VAX.

VTAM

The Virtual Telecommunications Access Method is the IBM software running on the host system. It controls an SNA or APPN network and allows communication between the host operating system and user applications. VTAM maintains the directory of network devices and services, and selects the routes between various Network Control Program devices.

vulnerability analysis.

A vulnerability analysis is a type of risk analysis in which you calculate the effects of a project's success or failure on your overall business.