MNP 10 The tenth level of MNP that is used in cellular modems and in those situations where line quality is poor
V. FAST Proprietary, pseudo-standard from Hayes and Rockwell for modems transmitting at data rates up to 28,800 bps; served as a migration path for 34
V.42 ITU-T standard for modem error correction. Uses LAPM as the primary error- correcting protocol, with MNP classes 1 through 4 as an alternative.
V.42 bis ITU-T standard that enhances V.42 by incorporating the British Telecom Lempel Ziv data compression technique to V.42 error correction. Most V.32, V.32 bis, and V.34 compliant modems come with V.42 or V.42 bis or MNP.
V.90 ITU-T standard for 57,600 bps modems (commonly called “56K modems”) in which asymmetric data rates apply (i.e., the send and receive rates are different).
Depending on telephone line conditions, upstream rates (send) are restricted to 33,600 bps, and downstream rates (receive) are restricted to 57,600 bps. V.90 modems are designed for connections that are digital at one end and have involve only two analog-digital conversions each way.
vBNS An acronym for very high speed backbone network service, which is another National Science Foundation-funded research and educational network.
The vBNS is a nationwide backbone network that currently operates at 622 Mbps (OC-12) and is accessible to only those involved in high-bandwidth research activities. The backbone is expected to be upgraded to OC-48 (2.488 Gbps) in 1999.
VDSL An acronym for very high-speed digital subscriber line, which is a DSL variant that provide asymmetric service over fiber. Downstream rates range from 13 Mbps to 52 Mbps; upstream rates range from 1.5 Mbps to 2.3 Mbps. Suitable for Internet/intranet access, video-on-demand, database access, remote LAN access, and high-definition TV.
Virtual Channel Connection (VCC) A virtual circuit that provides a logical connection between an ATM source and destination. Data can only be transmitted in one direction via a VCC. A VCC is denoted by a virtual channel identifier (VCI), which is included as part of the ATM cell header. Multiple virtual channels that share the same connection can be packaged into a single virtual path.
Virtual Channel Identifier (VCI) A parameter used to identify ATM virtual channels. VCI information is carried within an ATM cell header.
Virtual Circuit A nondedicated connection through a shared medium that gives the high- level user the appearance of a dedicated, direct connection from the source node to the destination node.
Virtual Path Connection (VPC) A semi-permanent connection that provides a logical collection of ATM virtual channels that have the same end points. More specifically, a VPC carries a group of virtual channels all of which have the same end points. Virtual paths enable any connection that uses the same network path from source to destination to be bundled into a single unit. A virtual path identifier (VPI) is used denote a virtual path and is included in a cell’s header. A virtual path can also provide a form of traffic control by logically (not physically) partitioning network traffic based on the type of data being carried and associated quality of service.
Virtual Path Identifier (VPI) A parameter used to identify ATM virtual path. VPI information is carried within an ATM cell header.
VLAN An acronym for “virtual local area network.” Nodes comprising a VLAN are not physically connected to the same medium. Instead, they are connected in a virtual sense using specially designed software that groups several ports in a switch into a single work
group. Nodes connected to these ports are considered to be part of a workgroup, and network traffic from any node/port is (usually) limited to only those nodes or ports assigned to the workgroup.
VOFR An acronym for voice over frame relay, which refers to transmitting voice signals over a frame relay network.
Voice Over IP (VOIP) A technology that enables users to place telephone calls across the Internet.
VPN An acronym for virtual private network, which refers to an IP connection between two sites over a public IP network that has its payload traffic encrypted so that only source and destination nodes can decrypt the traffic packets. A VPN enables a publicly accessible network to be used for highly confidential, dynamic, and secure data transmissions.
WAN An acronym for wide are network, which interconnects computing resources that are widely separated geographically (usually over 100 km). This includes towns, cities, states, and countries. A WAN generally spans an area greater than five miles (eight kilometers). A WAN can be thought of as consisting of a collection of LANs.
Wavelength A measure of the length of a wave. It is the distance an electrical or light signal travels in one complete cycle.
Wavelength Division Multiplexing (WDM) A multiplexing method used with fiber- optic cables. Involves the simultaneous transmission of light sources over a single fiber- optic channel. Light sources of different wavelengths are combined by a WDM multiplexer and transmitted over a single line. When the signals arrive, a WDM demultiplexer separates them and transmits them to their respective destination receivers.
Wire A general term used to describe the physical layer of a network. The three main physical attributes of wire are conductor, insulation, and outer jacket. Wire also has three important electrical characteristics that can directly affect the quality of the signal transmitted across it: capacitance, impedance, and attenuation. Signal quality is affected most by the combination of attenuation and capacitance. The two primary forms of wire are copper and fiber. Also called cable.
Wireless Communications A type of communications in which signals travel through space instead of through a physical cable. There are two general types of wireless communication: radio transmission and infrared transmission.
Wire Speed A unit of measure used to describe a device’s maximum (i.e., fastest) filtering and forwarding rates. In Ethernet/802.3, wire speed is equal to 14,880
frames per second. This is frequently reported as 14,880 packets per second. (See Box 8-3.)
WLAN An acronym for wireless LAN.
Workgroup Switch A term used to describe one application of an Ethernet switch. A workgroup switch partitions a single, shared medium into multiple, shared media and supports more than MAC address per port. Also called segment
switches.
Workstation A computer system that has its own operating system and is connected to a network. A workstation can be a personal computer such as a Macintosh or Intel-based PC, a graphics workstation such as those manufactured by Sun Microsystems, a super- minicomputer such as IBM’s AS/400, a super-
microcomputer such as DEC’s Alpha, or a mainframe such as an IBM ES-9000.
Also called host, server, desktop, or client.