ATM Configuration and Troubleshooting Guide

Glossary
unshielded twisted pair
Glossary 335
PVC Permanent Virtual Circuit. A channel
through a network provided by a carrier
between two end points for dedicated
long-term information transfer between two
locations. Contrast with SVC.
S
single point of failure (SPOF). Any single
element in the Highly Available system that
may fail.
SDH Synchronous Digital Hierarchy.
International version of SONET that is
based on 155 Mbit/s increments (instead of
SONET’s 51 Mbit/s increments).
SDU Service Data Unit. A unit of interface
information whose identityis preserved from
one end of a layer connection to the other.
shortcut route Within an MPOA system,
an established route for a specific data flow.
A shortcut is shorter than the default route.
SONET Synchronous Optical Network. A
set of standards for the digital transmission
of information over fibre optics. Based on
increments of 51 Mbps.
Stationary IP address An
MC/ServiceGuard concept. Each active
network interface in each node in an
MC/ServiceGuard cluster has a unique IP
address called the stationary IP address.
This IP address is not associated with a
package and is not transferrable to another
node.
SVC Switched Virtual Circuit. A channel
established on demand that is used for
transferring information between two
locations. The connection is established by
network signalling, and lasts only for the
duration of the transfer. It is the data
communicationsequivalent of adialedphone
call.
T
threshold Within MPOA, the maximum
number of packets that can be forwarded
over the default route to a specific address
during a fixed amount of time. When the
threshold is exceeded, a shortcut route is
established.
U
UBR Unspecified Bit Rate. An ATM traffic
type that is equivalent to “Best Effort”. UBR
is defined by its Peak Rate.
UNI User-Network Interface. ATM Forum
standard that defines how private CPE
interacts with private ATM switches. A
connection that directly links a user's device
to an ATM network (usually, through an
ATM switch). Also, the physical and
electrical demarcation point between the
user device and the ATM switch.
There are two types of ATM UNI:
Private UNI — used to interconnect an ATM
end-device with an ATM switch that isnot in
the public network; for example, a switch
that is managed as part of the same
corporate network.
Public UNI — used to interconnect an ATM
end device with an ATM switch that is in the
public network.
unshielded twisted pair Cabling
comprising pairs of cable for carrying
different signals.