ATM Configuration and Troubleshooting Guide

Glossary
UTP Cat 5
Glossary336
UTP Cat 5 A standard that specifies how an
unshielded twisted pair cable should be
installed to ensure a specific quality of
signal.
V
VBR Variable Bit Rate. An ATM traffic type
that is equivalent to guaranteed traffic type.
It is defined by its Peak Rate, Sustainable
Rate, and Burst Tolerance.
VC Virtual circuit. A generic term for any
logical communications medium. Note: VC
does not stand for virtual channel. Virtual
channels are referred to as VCCs (virtual
channel connections). There are three
classes of VCs: permanent, switched, and
smart (or soft) permanent.
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—that is, a higher layer or
ATMM-entity—forprocessing, signifying the
endpoints of a VCC. VCCs are
unidirectional.
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.
VCI Virtual Channel Identifier. The field in
the ATM cell header that labels (identifies) a
particular virtual channel.
Virtual router A group of edge devices
that, together, act like a traditional routed
network. The difference is that the virtual
router’s performance is not limited by
hop-to-hop routing like a traditional routed
network often is.
VPI Virtual Path Identifier. The field in the
ATM cell header that labels (identifies) a
particular virtual path.