Glossary E-19
V.35
A data communications interface standard adopted by the CCITT. Often used for data circuits
operating at 56 Kbps and above.
VAD (Voice Activity Detection)
Used to statistically compress voice by not sending packets in the absence of speech.
VBR (Variable Bit Rate)
Connection type for variable bit rate traffic such as bursty data. Compare with CBR and ABR.
VC_Q
Frame relay buffer allocation parameter that specifies the maximum queue size reserved in the
FRP card for the FR connection.
virtual circuit
A circuit that acts like it is an individual transmission path but is actually shared with other
circuits over a single transmission path. Compare with PVCs.
VNS
The adjunct processor used in the INS Voice Network Switching application. The VNS is
co-located with and connected to an IGX or IPX switch.
Voice Network Switching
An INS application used to provide voice or data switched virtual circuits over a Cisco WAN
switching network for PBXes using either QSIG or DPNSS signalling.
VS/VD (Virtual Source/Virtual Destination)
ATM Forum Traffic Management 4.0 method of providing congestion flow control for ABR
connection types. Resource Management (RM) cells are used to convey management
information between sources and destinations.
vt (virtual terminal)
An IPX control terminal that is the active control terminal at one node but is physically attached
to another node.
W
WAN (Wide Area Network)
A network of transmission circuits generally spanning a large region or territory for transmission
of voice and data between widespread end users. An IGX/BPX network is an example of a WAN.
X
X.21
A CCITT standard for data interfaces transmitting at rates up to approximately 2 Mbps.
X.25
A commonly-used standard that defines the protocol for low-speed data packet networks.
