Variable Bit Rate. In ATM QoS, VBR specifies that the data stream is entitled to a particular average rate and well-defined burst properties.
Virtual Circuit. In many packet-switching networks, such as ATM and Frame Relay, logical connections called Virtual Circuits are set up between end-point devices.
Virtual Channel Identifier. The VCI is a 16-bit number that appears in the ATM UNI cell header. The VCI defines a particular channel within a Virtual Path (see VPI) that together specify a particular VC.
See VPN.
Virtual Local Area Network. A VLAN is a logical grouping of devices. The switches that define a particular VLAN ensure that it is treated as a broadcast domain distinct from any other VLANs in the network.
Variable Length Subnet Mask. When creating IP subnets, using VLSM means that not all of these subnets must be of equal size.
Virtual Path Identifier. The VPI is an 8-bit number that appears in the ATM UNI cell header. The VPI defines a bundle of Virtual Channels. See VCI.
Virtual Private Network. A VPN is a tunneled connection that is usually encrypted. It is used primarily to create a secure connection between two points that are separated by an untrusted network.
Virtual Router Redundancy Protocol. This protocol is an open standard defined in RFC 2338. It allows two routers to possess the same IP and MAC addresses for redundancy. While only one router is active at a time, the other is capable of quickly becoming active in case it fails. See also HSRP.