Glossary
V
Centillion 1200N ATM Switch User Manual
B-83
NTP 297-8103-903
UTOPIA
Universal Test & Operations Interface for ATM: Refers to an electrical interface
between the TC and PMD sublayers of the PHY layer.
UTP
Unshielded Twisted Pair: A cable having one or more twisted pairs, but with no
shield per pair.
V
VBR
Variable Bit Rate: An ATM Forum defined service category which supports
variable bit rate data traffic with average and peak traffic parameters.
VC
Virtual Channel: Existing with a Virtual Tributary, in the terminology of SONET it
is equivalent to a traditional TDM channel. It’s just a fancier for a channel, but
maintaining the (virtual nomenclature of SONET).
A communications channel that provides for the sequential unidirectional transport
of ATM cells.
VCC
Virtual Channel Connection: A concatenation of VCLs that extends between the
points where the ATM service users access the ATM layer. The points at which the
ATM cell payload is passed to, or received from, the users of the ATM Layer (i.e.,
a higher layer or ATM-entity) for processing signify the endpoints of a VCC. VCCs
are unidirectional.
VCCI
Voluntary Control Council for Interference
VCI
Virtual Channel Identifier: A unique numerical tag as defined by a 16 bit field in
the ATM cell header that identifies a virtual channel, over which the cell is to travel.
VCL
Virtual Channel Link: A means of unidirectional transport of ATM cells between
the point where a VCI value is assigned and the point where that value is translated
or removed.
