V

VBR

Variable Bit Rate: A QoS class, as defined by the ATM Forum, for use in ATM networks that is subdivided into real time (RT) class and non–real time (NRT) class. RT is employed when connections have a fixed timing relationship between samples. Conversely, NRT is employed when connections do not have a fixed time relationship between samples, but still need an assured QoS.

VCC

Virtual Channel Connection: A logical circuit that is created by VCLs. VCCs carry data between two endpoints in an ATM network. Sometimes called a virtual circuit connection.

VIP

1. Versatile Interface Processor: An interface card for Cisco 7000 and 7500 series routers, providing multilayer switching and running the Cisco IOS software. The most recent version of VIP is VIP2.

2. Virtual IP: A function making it possible for logically separated switched IP workgroups to run Virtual Networking Services across the switch ports of a Catalyst 5000.

virtual circuit

Abbreviated VC, a logical circuit devised to assure reliable communication between two devices on a network. Defined by a virtual path connection (VPC)/virtual path identifier (VCI) pair, a virtual circuit can be permanent (PVC) or switched (SVC). Virtual circuits are used in Frame Relay and X.25. Known as virtual channel in ATM. See also: PVC and SVC.

virtual ring

In an SRB network, a logical connection between physical rings, either local or remote.

VLAN

Virtual LAN: A group of devices on one or more logically segmented LANs (configured by use of management software), enabling devices to communicate as if attached to the same physical medium, when they are actually located on numerous different LAN segments. VLANs are based on logical instead of physical connections and thus are tremendously flexible.

VLSM

Variable-Length Subnet Mask: Helps optimize available address space and specify a different subnet mask for the same network number on various subnets.

Voice over ATM

(VoATM) The design and use of voice traffic using ATM networks.

Voice over Frame Relay

(VoFR) The design and use of voice traffic using Frame Relay networks.

VoIP

(Voice over IP) The design and use of voice conversations over IP networks.