Glossary - V
- V.22 (protocol, communications)
An IUT-T modem protocol which allowed
data rates of 1200 bits per second. V.22bis doubled
- V.22bis (protocol, communications)
An IUT-T modem protocol which allowed
data rates of 2400 bits per second, twice that of V.22.
- V.32 (protocol, communications)
The IUT-T standard protocol for
modems transmitting at 4800 or 9600 bits per second.
V.32bis extended this to 14400 bps. V32 and V.32bis acheive bidirectional data
transmission not by having different sets of tones at each end but by subtracting what is sent from what is
- V.32bis (protocol, communications)
V.32 twice. An extension of the IUT-T V.32
modem protocol allowing speeds of 7200, 12000 and 14400
bits per second. The modem should select the appropriate speed according
to the current line conditions. See also V.32ter.
- V.32ter - V.32terbo (protocol, communications)
An extension of the IUT-T V.32bis
modem protocol. While waiting for V.34, many modem
manufacturers decided to extend V.32bis to 19.2 kbps.
This was known as V.32ter which some marketroids rechristened V.32 terbo which is not
only misspelled but misses the fact that V.32ter means the third revision of V.32.
- V.34 (protocol, communications)
A modem operating at data signalling rates of up to 28 800
bits per second (2400, 2743, 2800, 3000, 3200 and 3429 and up to 28800 bits
per second) for use on the general switched telephone network and on leased point-to-point 2-wire
During the lengthy process of approval by IUT-T, many manufacturers
released 28.8 kbps modems described as V.FAST. The V.34 recommendation was ratified
by ITU-T on 20 September 1994. Rockwell and US Robotics both have seats on the ITU-T, and have both
released chip set/BIOS combinations that they feel will meet V.34. V.34 modems will also support V.FC if
the manufacturer currently supports V.FC (e.g. Rockwell).
Ref: IUT-T V 34.
- V.34bis (protocol, communications)
A draft IUT-T standard for
modem transmitting at 33600 bps.
- V.35 (protocol, communications, standard)
The IUT-T standard for data
transmission at 48 kilobits per second over 60 - 108 KHz group band
circuits. It contains the 34-pin V.34 connector specifications normally implemented on a modular RJ-45
An IUT-T standard protocol for error
correction between modems which includes MNP
up to level 4.
An extension of the IUT-T V.42
standard modem protocol to included
- Value Added Network (network)
A bogus technological prediction or a foredoomed engineering concept, especially one that fails by
implicitly assuming that technologies develop linearly, incrementally, and in isolation from one another
when in fact the learning curve tends to be highly nonlinear, revolutions are common, and competition is
the rule. The prototype was Vannevar Bush's prediction of "electronic brains" the size of the Empire State
Building with a Niagara-Falls-equivalent cooling system for their tubes and relays, a prediction made at
a time when the semiconductor effect had already been demonstrated. Other famous vannevars have included
magnetic-bubble memory, LISP machines, videotex, and a paper from the late 1970s that computed a purported
ultimate limit on areal density for integrated circuits that was in fact less than the routine densities of
5 years later.
Variable bit rate (ATM)
Information that can be represented digitally by groups of bits (as opposed to streams) is characterized
by a variable bit rate. Most data applications generate VBR traffic,which can tolerate delays and fluctuating throughput.
- VBR-NRT - nrt-VBR
Variable Bit Rate - Non-Real Time (ATM)
One of five ATM Forum-defined service types.
It is used for transmitting traffic where timing information is not critical and which is characterized by
the average and peak cell rates. It is well-suited for long data packets transfers.
- VBR-RT - rt-VBR
Variable Bit Rate - Real Time (ATM)
One of five ATM Forum defined service types
for transmitting traffic that depends on timing information and control and which is characterized by the
average and peak cell rates. It is suitable for carrying traffic such as packetized (compressed) video and
Virtual Circuit (network)
A connection set-up across the network between a source and a destination where a fixed route is chosen
for the entire session and bandwidth is dynamically allocated on
demand by the network as users have traffic to transmit. See also datagram,
Virtual Connection (network)
A connection established between end-users (source and destination), where packets are forwarded along
the same path and bandwidth is not permanently allocated until it
Virtual channel (network, ATM)
A term to describe unidirectional flow of ATM cells
between connecting (switching or end-user) points that share a common identifier number (VCI)
A VC may traverse several virtual paths.
Each physical circuit in an ATM network is pre-configured with some number of virtual paths. Each virtual
path may support many virtual channels. Neither VPs nor VCs are assigned any dedicated
bandwidth. Bandwidth is allocated on demand by the network as users
have traffic to transmit. See VCC.
Virtual Channel Connection (ATM)
Defined as a concatenation of virtual channel links.
Virtual channels in two or more sequential physical circuits can be concatenated to create an end-to-end
connection, called a VCC. A VCC is a specific instance of a SVC or
PVC. A VCC may traverse one end-to-end VPC or several sequential
Virtual Channel Identifier (ATM)
The unique numerical tag used to identify every virtual channel across an ATM network, defined by a
16-bit field in the ATM
cell header. See VC,
Virtual Channel Link (network)
A means of unidirectional transports of ATM cells
between the point where a VCI value is assigned and the point where that value is
translated or removed.
Virtual Control Program Interface
An alternative, and incompatible method for doing the same thing as DOS Protected Mode Interface (DPMI).
V Digital Subscriber Line (communications, protocol, network)
See also DSL.
Visual Display Unit (hardware)
A device incorporating a cathode ray tube (CRT) display, a keyboard and a serial port. A VDU usually also
includes its own display electronics which store the received data and convert it into electrical waveforms
to drive the CRT.
Early VDUs could only display characters in a single preset font, and these were confined to being layed
out in a rectangular grid, reproducing the functionality of the paper-based teletypes they were designed
to replace. Later models added graphics facilities but were still driven via serial communications,
typically with several VDUs attached to a single multi-user computer. This contrasts with the much faster
single bitmap displays integrated into most modern single-user personal computers and workstations.
Video Electronics Standards Association (body, standard)
An industry standards organisation created in 1989 or 1990 mostly(?) concerned with IBM compatible
personal computers. The first standard it created was the
800 x 600 pixel Super VGA (SVGA) display and its
It also defined the VESA Local Bus (VLB). See also PCI.
It is the CRM normalized by the variance of the total cell rate over
a given circuit.
28800 bps, original (working) name for V.34
standard for modem. Most
implementations were incompatible with each other. It is obsolete.
Video Graphics Array (hardware)
A display standard for IBM PCs, with 640 x 480 pixels in
16 colours and a 4:3 aspect ratio. There is also a text mode with 720 x 400 pixels.
IBM technical references define the *product name* of their original VGA display board as "Video Graphics
Array", in contrast to the preceding boards, the "Color Graphics Adapter" (CGA) and "Enhanced Graphics
An obsolete electronic service offering people the privilege of paying to read the weather on their
television screens instead of having somebody read it to them for free while they brush their teeth.
The idea bombed everywhere it wasn't government-subsidised, because by the time videotex was practical
the installed base of personal computers could hook up to time-sharing services and do the things for
which videotex might have been worthwhile better and cheaper. Videotex planners badly overestimated both
the appeal of getting information from a computer and the cost of local intelligence at the user's end.
Like the gorilla arm effect, this has been a cautionary tale to hackers ever since. See also
Vendor Independant Messaging (communications, networking)
An electronic mail API promoted by an
industry group headed by Lotus Development. VIM is a competitor to Microsoft's MAPI.
(By analogy with biological viruses, via SF) A cracker program that searches out other programs and
"infects" them by embedding a copy of itself in them, so that they become Trojan horses. When these
programs are executed, the embedded virus is executed too, thus propagating the "infection". This normally
happens invisibly to the user.
Unlike a worm, a virus cannot infect other computers without assistance. It is propagated by vectors such
as humans trading programs with their friends (see SEX). The virus may do nothing but propagate itself and
then allow the program to run normally. Usually, however, after propagating silently for a while, it starts
doing things like writing "cute" messages on the terminal or playing strange tricks with the display (some
viruses include display hacks). Many nasty viruses, written by particularly antisocial crackers, do
irreversible damage, like deleting all the user's files.
In the 1990s, viruses have become a serious problem, especially among IBM PC and Macintosh users (the lack
of security on these machines enables viruses to spread easily, even infecting the operating system). The
production of special anti-virus software has become an industry, and a number of exaggerated media reports
have caused outbreaks of near hysteria among users; many lusers tend to blame *everything* that doesn't
work as they had expected on virus attacks. Accordingly, this sense of "virus" has passed into popular
usage (where it is often incorrectly used to denote a worm or even a Trojan horse). Compare back door.
Virtual Local Area Network
A network configuration in which users communicate using LAN protocols
as if they were on the same physical LAN, but where they are in fact on physically separate LANs. Software
and/or hardware mask the physical topology of the users and provide a logical topology which is more
suitable to the users' requirements.
- Vector Markup Language (graphics)
- Voice coder, speech is encoded before transmission to reduce the number of bits required to represent speech.
Video on Demand (communications)
A technology that enables the customer to remotely select and play a video, transmitted over communications
links. A planned system using video compression to supply programs to viewers when requested, via
ISDN or cable.
A term to describe a set of virtual channels (VCs) grouped together, between crosspoints
Each physical circuit in an ATM network is pre-configured with some number
of virtual paths. Each virtual path may support many virtual channels. Neither VPs nor VCs
are assigned any dedicated bandwidth. Virtual paths may be used to
construct end-to-end connections, called VPCs.
Virtual Path Connection (ATM)
Virtual paths in two or more sequential physical circuits can be concatenated
to create a logical connection, called a VPC. VPCs must be pre-configured. All Cells
traversing VCs in a VPC are routed the same way.
Virtual Path Connection Identifier/Virtual Channel Identifier (network)
A combination of two numbers, one for identifying the VP and one for VCI.
- Virtual Private Data Network (network, public)
Virtual Path Identifier (ATM)
The 8-bit number in an ATM
UNI cell header
or the 12-bit number in an ATM NNI or B-ICI
cell header identifying the specific virtual path (VP) on which the cell is traversing
on the current physical circuit. The ETSI version of ATM called it VCI. A virtual
connection established using only the VPI is known as a virtual path connection
Virtual Path Link (network, ATM)
The field in the ATM cell
header that labels (identifies) a particular virtual path.
Virtual Private Network (network)
Network resources provided to users, on-demand, by public carriers such that the users view this partition
of the network as a private network (customer-unique addressing,
network management capabilities, dynamic reconfiguration, etc.).
A VPN can also be used using cryptology across Internet, each end of a connexion is controled by a
The network connection appears to the user as an end-to-end, nailed-up circuit without actually involving
a permanent physical connection, as in the case of a leased line. The advantage of the VPNs over the
dedicated private networks is that the former allow a dynamic allocation of network resources.
Virtual Path Terminator (network)
A system that unbundles the VCs of a VP for independent
processing of each VC.
Vertical Redundancy Check (network)
Partity check applied to a single word, not to a complete set of words.
- Virtual Reality Modeling Language (language)
Voice Response Unit (telephone)
Syn IVR (Interactive Voice Response).
Equipment that prompts callers to input information about their accounts or about the nature of their call.
For example, a VRU might be a recording that instructs, "Please enter your account number using your
touch-tone phone," or "If you would like to speak with a sales agent, please press one".
The VRU feeds such information into the ACD so that calls are correctly routed. VRUs can also feed
information to agents in the form of screen pops. VRUs are sometimes called Interactive Voice Response
- Virtual Source/Virtual Destination (ATM)
Virtual Scheduling Algotithm (ATM)
GCRA equivalent algorithm used by ITU
UPC and NPC specifications.
Very Small Aperture Terminal (communications)
A kind of ground station used to contact a communications satellite such as INMARSAT.
Virtual Tributary (network, ATM)
A mechanism of capacity allocation in SONET that subdivides a synchronous
payload envelope into lower-bit-rate envelopes within the SONET signal.
Virtual Telecommunications Access Method
Access method IBM SNA architecture.
Voice Telephony Over ATM (ATM)
ATM Forum specification concerning voice telephony over
Virtual Terminal Protocol
OSI's remote terminal protocol.