A data Communication Historical Series
V & H COORDINATES:
The Vertical and horizontal grid points used to determine straight-line mileage between locations. And this information is normally used for mileage-sensitive product pricing.
V & H MILEAGE:
A representation of the vertical and horizontal mileage between two points: This is based on a geometrically computed approximation of the actual airline miles between two points. Carriers (Telephone Companies) normally keep a set of V & H coordinates in the local offices.
A group of ITU-TS & Consultative Committee International Telegraph and Telephone (CCITT) recommendations and standards: Governs data transmission over telephone lines; i.e. V11 through V54
A CCITT (International Consultative Committee for Telephone and Telegraph) Standard: Provides the electrical characteristics necessary for balanced double-current interchange circuits operating at data rates up to 10 mbps.
CCITT (International Consultative Committee for Telephone and Telegraph) standard for fax transmission at 14,400bps
The International Consultative Committee for Telephone and Telegraph (CCITT) standard for 0-300 bps, full duplex, dial-up MODEMS.
The CCITT Standard for 1200-bps full duplex, dial-up or a leased-line MODEM.
The CCITT Standard for 2400-bps full duplex, dial-up MODEM.
The CCITT Standard for 600- and 1200-bps, dial-up MODEM.
The CCITT list of definitions for interchange circuits between Data Terminal Equipment (DTE) and Data Communication Equipment (DCE).
The CCITT Standard for dial-up automatic calling or answering equipment.
The CCITT Standard for automatic calling and answering equipment on the PSTN
The CCITT Standard for 2400 bps, leased-line MODEM.
The CCITT Standard for 1200 and 2400 bps dial-up MODEM.
The CCITT Standard for 2400 bps full duplex, dial-up MODEM.
The CCITT Standard for 4800 bps, leased-line MODEM.
The CCITT Standard for 2400 and 4800 bps, leased-line MODEM.
The CCITT Standard for 2400 and 4800 bps, dial-up MODEM.
The CCITT Standard for the electrical characteristics of interchange circuits.
The CCITT Standard for 9600 bps, point-to-point, four-wire, leased-line MODEM.
An industry communications standard for a 19.2 Kbps dial-up MODEM
The CCITT Standard for 14.4Kbps, point-to-point, four-wire, leased-line MODEM connections.
Data transmission standard that provides for up to 33,600 bits per second (bps) communications over telephone lines: It defines a full-duplex (two-way) modulation technique and includes error-correcting and negotiation.
The CCITT Standard for data transmission at 48Kbps using 60 to180KHz wide-band circuits.
The CCITT Standard for error-correction.
A MODEM that follows all the V.42 specifications, except for LAPM error control (uses MNP).
A MODEM, which follows all the V.42 specifications: Uses LAPM error control or MNP error controls.
The CCITT Standard for MODEM loop backs.
Data transmission standard that provides for up to 56,000 bits per second (kbps) communications over telephone lines: The transmission speed from the client side MODEM is 33,600 bps, the same as V.34. The transmission speed from the host side MODEM, such as an Internet Service Provider (ISP) or corporate network, is up to 56,000 bps, with an average speed of 40,000 to 50,000 bps. When the host side MODEM does not support this standard, the alternative is V.34.
A new, international standard for 56Kbps data communications: This standard increases the upload speed, allows a data call to be put on hold to take an inbound voice call, and shortens the time to make a connection.
A designation for a MODEM capable of data speeds up to 28.800 bits per second (bps)
Refer to Voice Answer Back
Volts Alternating Current
VACANT CODE INTERCEPT:
A unit that routes all calls dialed with an unassigned first digit to one of the following: an attendant, a busy signal, a reorder signal or a recording.
VACANT NUMBER INTERCEPT:
A unit that routes calls with unassigned numbers to the attendant: May be a busy signal, or a recording.
A technique used by 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 cross check the original for possible changes.
Voice Activity Detection: When enabled on a voice port or a dial peer, silence is not transmitted over the network, only audible speech. When VAD is enabled, the sound quality is slightly degraded but the connection monopolizes much less bandwidth.
Value Added Data Network: Refer to Value Added Network
Digital certificate for data items that can be trusted; can be validated successfully
VALID TRANSMISSION TIMER:
A device, in Fiber-Distributed Data Interface (FDDI) network, that measures the period between valid transmissions on a ring. It helps to detect excessive ring noise, token loss, and other faults.
The formal confirmation process of reviewing or examining a single data element value, a requirements specification, a user interface, an implementation design, plan, schedule, budget, or similar system element.
A test of transmission quality
VALUE ADDED CARRIERS:
References vendors that add special features to services purchased from other carriers and resell the service.
Value Added Network Service: A data transmission network routing data according to available paths. The service assures that the message will be received as it was sent, provides for user security, and provides high speed transmission and conferencing among terminals.
Refer to Vector Adaptive Predictive Coding
References products announced but not yet commercially available. Often used by suppliers to lock in users with the promise of proposed future offerings.
A quantity that can assume or be a variable set of values
VARIABLE LENGTH RECORD:
A record whose total length depends on other related records
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.
DEC (Digital) designation for computer components (xx = model number)
Variable Bit Rate: QoS class defined by the ATM Forum for ATM networks. VBR is subdivided into a real time (RT) class and non-real time (NRT) class. VBR (RT) is used for connections in which there is a fixed timing relationship between samples. VBR (NRT) is used for connections in which there is no fixed timing relationship between samples but still needs a guaranteed QoS.
Visual Basic Script: Program language that can invoke any system function: including starting the system and 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.
See Virtual Circuit
1) Virtual Communications Address: The standard and extended programming API(s) for the Cisco VCO/4K product; uses a byte message scheme to facilitate communications between a controlling host application and the VCO/4K. Both source and destination VCA bytes are used to label and track communications between VCO/4K systems and host applications.
2) See Voice Connecting Arrangement
Refer to Virtual Channel Connection
Virtual Circuit Descriptor
1) Virtual Channel Identifier: 16-bit field in the header of an ATM cell. The VCI, together with the VPI, is used to identify the next destination of a cell as it passes through a series of ATM switches towards its destination. ATM switches use the VPI/VCI fields to identify the next network VCL that a cell needs to transit on its way to its final destination. The function of the VCI is similar to that of the DLCI in Frame Relay.
2) See Virtual Circuit Identifier
Virtual Channel Link: Connection between two ATM devices. A VCC is made up of one or more VCL(s).
Virtual Circuit Number: 12-bit field in a X.25 PLP header that identifies a X.25 virtual circuit; allows DCE to determine how to route a packet through the X.25 network.
Virtual Central Office: VCO represents the Cisco VCO/4K product, an open, host-controlled, telephony switch capable of providing a wide range of enhanced services in the telecommunications market.
Volts Direct Current
Very high bit-rate Digital Subscriber Line: A MODEM for twisted pair access operating at data rates from 12.9 to 52.8 Mbps downstream and 1.5 to 2.3 Mbps upstream, with a corresponding maximum distance up to 3000 feet using 24-gauge twisted pair.
Video Display Terminal or Video Dial Tone
See Video (Visual) Display Unit
Data segment of a SNA message: A vector consists of a length field, a key that describes the vector type, and vector-specific data.
VECTOR ADAPTIVE PREDICTIVE CODING (VAPC):
An audio coding algorithm primarily for use at the lowest transmission bit rates.
A font rendered from a mathematical model, in which each character is defined as a set of lines drawn between points. Vector fonts can be cleanly scaled to any size or aspect ratio.
VENDOR INDEPENDENT MESSAGING (VIM):
An accepted standard for the interface to E-mail functions from Lotus, WordPerfect and others.
VERIFIED ACCOUNT CODES:
Refers to a finite list of carrier verified and predefined account codes.
Very Easy Rodent Oriented Network Index to Computerized Archives: A search tool, like Archie, that searches text in Gopher menus. Now may be obsolete because of other web-based search engines.
VERSATILE INTERFACE PROCESSOR:
A provider of tax rate tables and related software
VERTICLE PARITY / CHARACTER PARITY:
One of many different forms of error detection using a vertical parity count within the bits of each character transmitted. If any error is found, the character or block of characters would normally be re transmitted.
VERTICLE REDUNDANCY CHECK (VRC):
A method of error detection using an extra bit, called a parity bit, in each character for checking purposes. The receiving station detects whether there is an odd or even number of 1's (depending on whether the system uses even or odd parity). Noise or distortion on the line may cause a bit to be lost or added. The error is either noted or the receiving station may initiate a re-transmission.
1) Variance Factor: One of three link attributes exchanged using PTSP(s) to determine the available resources of an ATM network. VF is a relative measure of CRM using the variance of the aggregate cell rate on the link.
2) Voice Frequency: Refer to Voice Grade Band
Voice Frequency Access - A DS-0 option
Voice Grade: See Voice Grade Band
Video Graphics Array
See Voice Grade Data Facility
Voice Grade Frequency: Refer to Voice Grade Band
Very High Frequency: The frequencies between 30 MHz and 300 MHz (TV channels 2 to 13).
VIA NET LOSS (VNL):
The highest possible signal loss (signal level), in decibels, at which a trunk or line facility can still operate: Typical contributing factors are echo, cross talk, noise, and singing.
Voice interface card: Connects the system to either the PSTN or to a PBX; see PBX and PSTN
VLAN ID: The identification of the VLAN, which uses the standard 802.1Q. Being 12 bits, it allows the identification of 4096 VLAN(s).
An expansion board that plugs into a personal computer to provide display capabilities: A computer's display capabilities depend on both the logical circuitry, provided in the video adapter, and the monitor. Each adapter offers several different video modes. The two basic categories of video modes are text and graphics. Within the text and graphics modes, some monitors also offer a choice of resolutions. At lower resolutions a monitor can display more colors.
Modern adapters contain memory, so that the computers RAM (Random Access Memory) is not used for storing display information. In addition, most adapters have their own graphics coprocessor for performing graphics calculations. These adapters are often called graphics accelerators.
VIDEO CONFERENCE / CONFERENCING:
A conference between two or more remote locations with live animated image transmission and display; could employ satellite transmission over a wideband range spanning between 56 kbps to 1.544 mbps (T1 circuit speed).
VIDEO DIAL TONE (VDT):
The visual counterpart to a basic exchange service, audio dial tone, video information is switched over a public network. VDT can be used to connect one or more locations for the transmission and exchange of visual and auditory information.
VIDEO GRAPHICS ARRAY (VGA):
The standard IBM PC video display: Provides medium resolution text and graphics. VGA pixel resolution: 640 X 480.
The frequency needed to transmit moving pictures, requires one to six MHz
See Vendor Independent Messaging
Virtual Integrated Network Service: NOS developed and marketed by Banyan Systems.
1) Versatile Interface Processor: Interface card used in Cisco 7000 and Cisco 7500 series routers. The VIP provides multilayer switching and runs Cisco IOS. The most recent version of the VIP is VIP2.
2) Virtual IP: Function that enables the creation of logically separated switched IP workgroups across the switch ports of the Catalyst 5000 running Virtual Networking Services software.
1) A term generally used to describe the main memory of a virtual (simulated) computer. Using virtual memory, via address space, memory space and address translation/mapping, greater memory capacity is possible and faster processing can occur because only that portion of a program needed at the moment is drawn into memory.
2) From a data communications standpoint, the term virtual may imply infinite capacity of data channels and circuits.
VIRTUAL ADDRESS EXTENSION (VAX):
Digital Equipment's computer systems
A logical point-to-point connection between two devices (processes). Many virtual channels may time-share a single circuit (link).
VIRTUAL CHANNEL CONNECTION (VCC):
The basic unit of switching in BISDN set up between two end users through a network. Normally a variable-rate, full-duplex flow of fixed-size cells is exchanged over the connection.
VIRTUAL CIRCUIT (VC):
A data circuit that exists only for the duration of a call, but is sharing a data channel with other calls on virtual circuits; a packet switching environment providing network facilities with the appearance of a dedicated private line, even though individual packets may constantly be taking variable routes.
Logical circuit created to ensure reliable communication between two network devices. A virtual circuit is defined by a VPI / VCI pair, and can be either permanent (PVC) or switched (SVC). Virtual circuits are used in Frame Relay and X.25. In ATM, a virtual circuit is called a virtual channel.
VIRTUAL CIRCUIT IDENTIFIER (VCI):
In cell relay systems, VCI allows the networks to assign a fixed route for all frames between the network end-points by using simple ‘table look-up’ procedures.
A Company utilizing limited central office administration: Made possible by improved communications and group-ware software.
In ATM, a physical connection between end users that has a defined route and endpoints
A technique for routing messages where the header and tail (end) of the message both move as rapidly as possible: If the header is delayed because a link (connection) it wants to cross (connect to) is being used by some other message, the tail continues to advance, and the message's contents are put into buffers at intermediate nodes. See Packet, Packet Switching and Wormhole Routing.
VIRTUAL IP ADDRESS:
An IP (Internet Protocol) address that is shared among the hosts of a Network Load Balancing cluster: A Network Load Balancing cluster might also use multiple virtual IP addresses, for example, in a cluster of multi-homed Web servers.
A logical rather than a physical LAN comprised of work-groups drawn together for business reasons or for a particular project irrespective of each member's actual location. Members are likely to belong to several such LANs as their job function dictates.
VIRTUAL LOCAL AREA NETWORK (VLAN):
A logical grouping of hosts on one or more LAN(s) that allows communication to occur between hosts as if they were on the same physical LAN.
The technique of making one computer appear to be several computers
Temporary storage used by a computer to run programs that need more memory than it has. For example: Programs could have access to 4 gigabytes of virtual memory on a computers hard drive, even if the computer has only 32 megabytes of RAM (Random Access Memory). The program data that does not currently fit in the computers memory is saved into paging files.
VIRTUAL MEMORY SIZE:
In Task Manager, the amount of virtual memory, or address space, committed to a process.
VIRTUAL MEMORY SYSTEM (VMS):
One of the computer operating systems for Hekimian's REACT 2000 OSS
VIRTUAL NETWORKING SERVICES:
Software on some Catalyst 5000 switches that enables multiple workgroups to be defined across switches and offers traffic segmentation and access control
Logical grouping of virtual circuits that connect two sites
VIRTUAL PRINTER MEMORY:
In a PostScript printer, a part of memory that stores font information: The memory in PostScript printers is divided into two areas: banded memory and virtual memory. The banded memory contains graphics and page-layout information needed to print the document. The virtual memory contains any font information that is sent to the printer either when a user prints a document or downloads fonts.
VIRTUAL PRIVATE LINE:
A service functionally equivalent to a private line, but uses commonly shared circuits rather than dedicated circuits. Such as: AT&T's Software Defined Network (SDN) service, MCI's Vnet, and Sprint's Virtual Private Network (VPN
VIRTUAL PRIVATE NETWORK (VPN):
1) The extension of a private network that encompasses encapsulated, encrypted, and authenticated links across shared or public networks. VPN connections can provide remote access and routed connections to private networks over the Internet.
2) May refer to the Banyan Systems Virtual Networking operating system, based on the Unix system V. This network operating system provides transparent communication across heterogeneous networks.
3) Switched network with special services such as abbreviated dialing: Allows customers to call different area codes without dialing all eleven digits.
Entity in an SRB network that logically connects two or more physical rings together either locally or remotely. The concept of virtual rings can be expanded across router boundaries.
In SNA, a logical connection between sub-area nodes that is physically realized as a particular explicit route
Logical grouping of devices that share a common Layer 3 subnet
Groups of users formed to solve particular problems without taking them away from their assigned location. An option made feasible with group-ware.
VIRTUAL TELECOMMUNICATIONS ACCESS METHOD (VTAM)
Mainframe software interface to data communications devices. VTAM is used by IBM's system network architecture (SNA).
VIRTUAL TELECOMMUNICATIONS NETWORK SERVICE (VTNS):
AT&T Integrated service packages
A portion of a physical interface that has the following characteristics: address space containing only one VPI and all VCI(s) underneath, bandwidth that is rate limited by hardware (VI), and ownership by a controller that uses it to interface to another peer controller.
A computer program file capable of attaching to disks or other files and replicating itself repeatedly, typically without user knowledge or permission: Some viruses attach to files so when the infected file executes, the virus also executes. Other viruses sit in a computer's memory and infect files as the computer opens, modifies or creates the files. Some viruses display symptoms while other viruses damage files and computer systems, but neither pronounced symptoms nor damage is essential in the definition of a virus; a non-damaging virus is still a virus.
There are computer viruses written for several operating systems including DOS, Windows, Amiga, Macintosh, Atari, UNIX, and others. McAfee.com presently detects over 57,000 viruses, Trojans, and other malicious software. Note: The preferred plural is the English form: viruses.
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.
If you receive an e-mail message about a virus, check with a reputable source to ensure the warning is real. Sometimes hoaxes start out as viruses and some viruses start as hoaxes, so both viruses and virus hoaxes should be considered a threat.
Virtual LAN: Group of devices on one or more LAN(s) that are configured, using management software, so they can communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments. Because VLAN(s) are based on logical instead of physical connections, they are flexible.
Very Low Frequency: Refers to the frequencies below 30 KHz.
Virtual LAN Inter-network: Inter-network composed of VLAN(s).
Visitor Location Register: A database that contains temporary information about subscribers who roam into an area controlled by a different MSC. The VLR communicates with the HLR of the subscriber to request data about that subscriber.
Very Large Scale Integration (chip): A term used to describe a very high density microchip containing up to 10,000 circuits.
Variable-Length Subnet Mask: Capability to specify a different subnet mask for the same network number on different subnets. VLSM can help optimize available address space.
Virtual Media Access Control
See Virtual Memory System or Voice Message System
See Via Net Loss
Virtual Networking Services: Software on some Catalyst 5000 switches that enables multiple workgroups to be defined across switches and offers traffic segmentation and access control
Voice over ATM: Voice over ATM enables a router to carry voice traffic, telephone calls and faxes, over an ATM network. When sending voice traffic over ATM, the voice traffic is encapsulated using a special AAL5 encapsulation for multiplexed voice.
VoATM DIAL PEER:
Dial peer connected via an ATM network. VoATM peer’s point to specific VoATM devices
Video on Demand: System using video compression to supply video programs to viewers when requested, via ISDN or cable.
Voice over Frame Relay: VoFR enables a router to carry voice traffic, telephone calls and faxes, over a Frame Relay network. When sending voice traffic over Frame Relay, the voice traffic is segmented and encapsulated for transit across the Frame Relay network using FRF.12 encapsulation.
VoFR DIAL PEER:
Dial peer connected via a Frame Relay network. VoFR peer’s point to specific VoFR devices
Voice over HDLC: Voice over HDLC enables a router to carry live voice traffic, telephone calls and faxes, back-to-back to a second router over a serial line.
VoHDLC DIAL PEER:
Dial peer connected via a HDLC network. VoHDLC peer’s point to specific VoHDLC devices
VOICE ANSWER-BACK (VAB):
A device that provides voice responses to inquiries made from telephone-type terminals. The audio response is composed of a limited, digitized voice vocabulary, prerecorded on a magnetic drum or disk file and produced by an audio response unit.
See Voice Grade Band
VOICE CONNECTING ARRANGEMENT (VCA):
A communications interface arrangement that allows the connections of non-carrier provided voice terminal equipment to the carrier switched telephone network.
See Voice Connecting Arrangement
VOICE / DATA PABX:
A user owned, automatic telephone exchange combining the functions of a voice PABX and a data PABX, sometimes used for DOV services.
VOICE DIGITATION /DIGITIZING:
Refers to the conversion of analog voice signals into binary or digital signals for transmission or storage.
VOICE FREQUENCY (VF):
Frequency in the 300 to 3300 Hz range: Allows reproduction of the voice with reasonable fidelity. See Voice Grade Band
VOICE GRADE (VG):
A line suitable for voice, data, facsimile, or telegraph service: A line with a usable frequency range of about 300-3300 Hz. See Voice Grade Band
VOICE GRADE BAND (CHANNEL):
A telephone line, which provides the necessary frequency range to carry a normal voice conversation: Normal frequency bandwidth is 4000 Hz and usually the voice (conversation) is carried within a usable frequency of 300 to 3600 Hz. A voice grade line can also be divided into a group of frequencies and used to carry several data lines that individually require a smaller frequency range.
VOICE GRADE CHANNEL:
A channel or line offering the minimum bandwidth suitable for voice frequencies: Usually 300 to 3600 KHz. See Voice Grade Band
VOICE GRADE EQUIVALENT:
The usable capacity of a digital circuit divided by 64 Kbps: As in the usable number of DS-0 channels on a circuit.
VOICE GRADE FACILITY (VGF):
A circuit designed to accommodate Direct Distance Dialing (DDD) and is suitable for voice, low-speed data, facsimile, or telegraph service. See Voice Grade Band
VOICE GRADE LINE:
See Voice Grade Band
An automatic answering service that records and replays messages: Voice mail uses a programmable computer with typical options, such as, temporary call routing, monitoring, and reporting.
VOICE MAIL BOX:
The assigned location of one user or a number on a voice mail system
VOICE MAIL MODULE INTERFACE:
Provides for the retrieval of voice message recordings at a later time or date
VOICE MESSAGE SYSTEM (VMS):
A leased service that allows a telephone user access to a voice mail system: They can leave a message for a particular person.
VOICE-OVER DSL (VoDSL):
A type of IP telephony: VoDSL allows multiple telephone lines to be combined into a single telephone line that also includes data transmission capabilities.
VOICE RESPONSE (VR):
The handling of calls by a computerized voice: Or an operator may hand off a call to a voice response system, which will provide information.
VOICE RESPONSE UNIT (VRU):
A device that is able to produce a spoken message from a selection of stored words.
VOICE STORE-AND-FORWARD (VSF):
A private branch exchange (PBX) feature: Permits the storage and remote retrieval of messages.
Refers to a computer-generated voice
VOICE ACTIVATED DIALING:
A feature that allows the user to dial a number by speaking the number or person’s name
VOICE GRADE CHANNEL:
A channel with a frequency bandwidth equivalent to a telephone channel obtained through the public telephone network. Voice grade channels are suitable for transmission of speech, digital or analog data, and facsimile and have a usable frequency range of about 300 to 3600 Hz. See Voice Grade Band
VOICE GRADE DATA FACILITY (VGDF):
A circuit with an approximate bandwidth of 0 to 3600Hz (usable 300 to 3300 Hz): Suitable for data transmission, remote metering, supervisory control, and miscellaneous signaling purposes.
VOICE GRADE DEVICE:
A communications channel that has a bandwidth of approximately 3600Hz, and can pass voice sounds in the bandwidth of approximately 300Hz to 3300Hz.
VOICE GRADE FACILITY (VGF):
A circuit designed to meet Direct Distance Dialing (DDD) network standards. VGF is suitable for voice, data, facsimile, or telegraph service. See Voice Grade Band
Voice over Internet Protocol: Provides for sending voice over a LAN (Local Area Network), or a WAN (Wide Area Network) or the Internet using TCP/IP (Transmission Control Protocol / Internet Protocol) packets.
The capability to carry normal telephony-style voice over an IP-based internet with POTS-like functionality, reliability, and voice quality: VoIP enables a router to carry voice traffic, telephone calls and faxes, over an IP network. In VoIP, the DSP segments the voice signal into frames, which then are coupled in groups of two and stored in voice packets. These voice packets are transported using IP in compliance with ITU-T specification H.323.
VoIP DIAL PEER:
Dial peer connected via a packet network: In the case of Voice over IP, this is an IP network. VoIP peer’s point to specific VoIP devices
A memory device that loses the stored contents during power fluctuations or failures
A memory is considered volatile if it loses stored information when power is removed. A memory that retains its data even when no power is applied is nonvolatile. SRAM (Static Random Access Memory) and DRAM are volatile memories.
The non-permanent image appearing on the screen of a visual display terminal (CRT ‘Cathode Ray Tube’)
The potential difference between two points in a circuit: A one volt potential difference is the force required to force one ampere of current through one ohm of resistance.
1) An area of storage on a hard disk; 2) A virtual disk into which a file system, database management system or other application places data; 3) A volume can be a single disk partition or multiple partitions on one or more physical drives; 4) A volume is formatted by using a file system, such as FAT or NTFS, and has a drive letter assigned to it. A user can view the contents of a volume by clicking its icon in Windows Explorer or in My Computer. A single hard disk can have multiple volumes, and volumes can also span multiple disks.
Virtual Path: One of two types of ATM circuits identified by a VPI. A virtual path is a bundle of virtual channels, all of which are switched transparently across an ATM network based on a common VPI.
Virtual Path Connection: Grouping of VCC(s) that share one or more contiguous VPL.
Virtual Private Dial-up Network: Also known as virtual private dial network. A VPDN is a network that extends remote access to a private network using a shared infrastructure. VPDN(s) use Layer 2 tunnel technologies (L2F, L2TP, PPTP) to extend the Layer 2, and higher parts of the network connection, from a remote user across an ISP network to a private network. VPDN(s) are a cost effective method of establishing a long distance, point-to-point connection between remote dial users and a private network.
Virtual Path Identifier: 8-bit field in the header of an ATM cell. The VPI, together with the VCI, identifies the next destination of a cell as it passes through a series of ATM switches towards its destination. ATM switches use the VPI / VCI fields to identify the next VCL that a cell needs to transit on its way to its final destination. VPI is similar to that of the DLCI in Frame Relay.
Virtual Path Link: Within a virtual path, a group of unidirectional VCL(s) with the same end points. Grouping VCL(s) into VPL(s) reduces the number of connections to be managed, therefore decreasing network control overhead and cost. A VPC is made up of one or more VPL(s).
Virtual Private Network: Enables IP traffic to travel securely over a public TCP/IP network by encrypting all traffic from one network to another. A VPN uses ‘tunneling’ to encrypt all information at the IP level.
A network that appears to its users as a private network although it may be made up of both private and public segments: A VPN may provide the requested bandwidth on demand or fixed bandwidth facilities.
See Voice Response
Vertical Redundancy Checking: A process of character or group (block) Parity Checking.
A VPN Routing / Forwarding instance: A VRF consists of an IP routing table, a derived forwarding table, a set of interfaces that use the forwarding table and a set of rules and routing protocols that determine what goes into the forwarding table. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router.
Virtual Reality Modeling Language: Specification for displaying three-dimensional objects on the World Wide Web; 3-D equivalent of HTML.
See Voice Response Unit
VS / VD:
Virtual Source / Virtual Destination
Vendor-Specific Attribute: An attribute that has been implemented by a particular vendor. It uses the attribute Vendor-Specific to encapsulate the resulting AV pair. Essentially, Vendor-Specific = protocol attribute = value.
Very Small Aperture Terminal (Satellite): VSAT consists of one master earth station (MAS) and numerous two-way satellite terminals. VSAT technology is widely used for data, voice, and fax transmission.
Cisco's virtual switch controller
See Voice Store-and-Forward or Virtual Telecommunications Access Method
Virtual Switch Interface
A VSI master process implementing the master side of the VSI protocol in a VSI controller: Sometimes the whole VSI controller might be referred to as a VSI Master but this is not necessarily correct.
A device that controls a VSI switch: For example, a VSI label switch controller.
Voice Services Provisioning Tool: Provides end-to-end configuration for IP, trunk groups, trunks, routes, and dial plans for VSC3000 and VISM. Also known as Dart
Vertical Tabulation: An ASCII Control character that causes the movement of the vertical printing (or CRT display) position to the next in a series of predetermined printing lines.
Virtual Telecommunications Access Method: An IBM software routine that provides users of 3270 type remote terminal systems access to applications programs through the data communications network. See Virtual Telecommunications Access Method
Virtual Tributary level n: SONET format for mapping a lower-rate signal into a SONET payload. For example, VT-1.5 is used to transport a DS-1 signal.
See Virtual Telecommunications Network Service
Virtual Terminal Protocol: ISO application for establishing a virtual terminal connection across a network.
Virtual Type Terminal: Commonly used as virtual terminal lines
Virtual Wavelength Path: A VWP is a group of one or more channels between source and destination nodes. The term virtual indicates that the signal path can actually travel on different physical wavelengths throughout the network. All channels of the VWP transit via the same path through the network.