- Van (Value Added Network)/Vans (Value Added Network Service) A data transmission network which guarantees data security and integrity through added computer control and communications, from the sender to the recipient often in the manner of a door-to-door courier or freight forwarder.
- Vaporware Products announced but not yet commercially available. Often used by suppliers to lock users in with the promise of great things to come.
- Videoconferencing Video and audio communication between two or more parties via a video-codec (coder/decoder) at either end linked by digital circuits. Formerly needing in excess of 300Mbit/s bandwidth, systems are now available offering acceptable quality for general use at 128Kbit/s and high-quality 71KHz audio. Factors influencing the growth of videoconferencing are improved compression technology, reduced cost through VLSI chip technology, low-cost switched digital networks - particularly ISDN - the emergence of standards and applications. Main players include BT, PictureTel and Compression Labs Inc.
- Videoconferencing standards ITU-TS H.261 was the standards watershed. Announced in November 1990, it relates to the decoding process used when decompressing videoconferencing pictures, providing a uniform process for codecs to read the incoming signals. Originally defined by Compression Labs Inc. Other important standards are H.221: communications framing; H.230 control and indication signals and H.242d: call set-up and disconnect. Encryption, still-frame graphics coding and data transmission standards have still to be developed.
- Videotex Term invented by the ITU to describe TV equipment used to display computer-based data, whether sent via a telephone (often called viewdata) or a broadcasting charnel (Teletext). ITU distinguishes between interactive or broadcast videotex.
- VIM (Vendor Independent Messaging) Standard for the application interface to e-mail from Lotus, WordPerfect and others. It will include MAPI compliance.
- Vines Banyan Systems' Virtual Networking operating system is based on Unix system V. This network operating system provides transparent communication across heterogeneous networks and is more expansive in concept, although attracting far fewer users, than Novell's NetWare.
- Virtual circuit A link that seems and behaves like a dedicated point to point line or a system that delivers packets in sequence, as happens on an actual point to point network. In reality, the data is delivered across a network via the most appropriate route. The sending and receiving devices do not have to be aware of the options and the route is chosen only when a message is sent. There is no prearrangement, so each virtual connection exists only for the duration of that one transmission.
- Virtual Container (VC) SDH defines a number of Containers, each corresponding to an existing plesiochronous rate. Information from a plesiochronous signal is mapped into the relevant container along with control information known as the "path overhead". The container plus path overhead form a VC.
- Virtual LAN A logical rather than a physical LAN comprising workgroups 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. Such LANs await the maturity of high-speed transmission technologies such as ATM before they can exist in any viable form.
- Virtual teams Ad hoc groups of users formed to solve particular problems without taking them away from their desks. A useful option made feasible with groupware.
- Virtual company Company built on the basis of teleworking with limited central office administration. Made possible by improved communications and groupware software, it is a phenomenon of the future.
- Virus Code that attaches itself to a program and makes copies of itself. It may or may not cause accidental or malicious damage, but is a serious nuisance particularly in a networked environment and where dependence on IT is heavy. Anti-virus applications such as Norton are available, but security should be augmented by procedures and regular backups.
- VMD MMS Virtual Manufacturing Device (VMD) mean?
To understand the concept of a virtual system, the following saying may help.
|If it's there and you can see it
|If it's there and you can't see it
|If it's not there and you can see it
|If it's not there and you can't see it
The MMS VMD represents all objects and services made available by a system compliant to MMS. How the VMD is implemented is totally outside the standard.
- Voice-grade channel, Voice-grade line A channel or line offering the minimum bandwidth suitable for voice frequencies, usually 300bit/s to 3.4Kbit/s.
- Voice Mail A system that records, stores and retrieves voice messages; either a standalone device or those that integrate to some extent with a user's phone system. Standalone voice mail is similar to a collection of answering machines but able to instruct each machine (voice mailbox) to carry out a range of features such as call forwarding. Messages can be delivered at a pre-arranged time, tagged and edited. Integrated systems indicate messages waiting via a light on a user's phone and/or an alphanumeric display. If the phone rings for a specified number of rings, it can default to a mailbox which delivers its invitation to leave a message and records the results.
- VPN (Virtual Private Network) The provision of private voice and data networking from the public switched network through advanced public switches. 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. VPNs retain the advantages of private networks but add benefits like capacity on demand.
- VSAT (Very Small Aperture Terminal) One-meter diameter satellite dishes used by remote sites, as opposed to the 3m dishes used by head office, in a satellite-linked network. The central office is able to broadcast or multicast data to the remote sites. In Europe, regulatory restrictions are gradually being lifted to allow two-way transmission. The US does not labor under the same protectionism and so has a flourishing VSAT community that allows the remote site to reply using the same link.
- V.Fast Forerunner to the V.34 modem standard due for ratification by 1995. V.Fast modems send a 1Mbyte file typically in under 1.5 minutes.
- V Series A group of ITU-TS recommendations governing data transmission over telephone lines. Series includes:
- V.21 300bit/s duplex modem for use over PSTN
- V.22 1200bit/s duplex modem for use over PSTN and leased lines
- V.22 bis 2.4Kbit/s duplex modem for use over PSTN and leased lines.
- V.23 600/1200bit/s modem for use over PSTN.
- V.24 Definitions of interchange circuits between DTE and DCE.
- V.25 bis Automatic calling and answering equipment on the PSTN.
- V.26 2.4Kbit/s modem for use over leased lines
- V.26 bis 2400/1200bit/s half duplex modem for use over PSTN.
- V.26 ter 2400/1200 bit/s full duplex modern for use over PSTN.
- V.27 4.8Kbit/s modem for use over leased lines.
- V.27 bis 4800/2400bit/s modem for use over leasedline.
- V.27 ter 4800/2400bit/s modem for use over PSTN
- V.29 9.6Kbit/s modem for use over leased lines.
- V.32 Up to 9.6Kbit/s bps modern for use over PSTN or leased lines.
- V.32 bis Up to 14.4Kbit/s modem for use over PSTN or leased lines.
- V.42 Error control procedures.
- V.42 bis Data compression technique for use with V.42
- VTAM (Virtual Telecommunications Access Method) An IBM software routine: the virtual access method for 3270 systems.