A virtual circuit is a logical circuit,
as opposed to a point-to-point circuit, created to ensure reliable
communication between two network devices. Two types of virtual
circuits exist: switched virtual circuits (SVCs) and permanent virtual
circuits (PVCs).
SVCs are virtual circuits that are
dynamically established on demand and terminated when transmission is
complete. Communication over an SVC consists of three phases: circuit
establishment, data transfer, and circuit termination. The
establishment phase involves creating the virtual circuit between the
source and destination devices. Data transfer involves transmitting
data between the devices over the virtual circuit, and the
circuit-termination phase involves tearing down the virtual circuit
between the source and destination devices. SVCs are used in
situations where data transmission between devices is sporadic. SVCs
increase bandwidth used due to the circuit establishment and
termination phases, but decrease the cost associated with constant
virtual-circuit availability.
A PVC is a permanently established
virtual circuit that consists of one mode: data transfer. PVCs are
used in situations where data transfer between devices is constant.
PVCs decrease the bandwidth use associated with the establishment and
termination of virtual circuits, but increase costs due to constant
virtual-circuit availability.
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Threaded
Case
Study |
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Washington
Project: WAN
Technology Design
The
WAN technology required for the Washington
District WAN's link to the Internet is a Frame
Relay PVC running at T1 speed. |
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