255-700-025
3-29
PacketStar
™
Access Concentrator 60 User Guide
, Issue 1
Release 6.3.0
Chapter 3 System Features
AC 60 Software Features
circuit level connections, where the circuit virtual channel (VC) flows are
identified by the payload type (PT) values.
Characteristics of OAM F4 Cells
•
Bidirectional
•
Have the same VPI value as user cells for VPC
•
Identified by one or more preassigned VCIs for both directions
•
In the same physical route for fault correlation and performance
information
Characteristics of OAM F5 Cells
•
Bidirectional
•
Have the same VPI/VCI values as the user cells for the VCC
•
Adentified by one or more preassigned VCIs for both directions
•
In the same physical route for fault correlation and performance
information
Fault Management Functions
Alarm surveillance functions are designed to aid in physical layer detection
and notification of network faults. Alarm surveillance measures are
performed on a continuous basis by features within network elements and
management systems. They monitor network elements for anomalies,
defects, and failures.
The three major aspects of the fault management functions are:
•
Detecting
•
Reporting
•
Localizing
Detection
Detection (continuity checks): periodically verifies connection integrity.
The activation/deactivation OAM mechanism is used to remotely start and
stop the generation of cells that perpetually monitor performance and
continuity. These mechanisms can indicate to the far end a connection is
alive, even if no user data traffic has been recently transmitted. When a
connection activates the continuity mechanism, continuity check cells are
inserted by the originating end point, either at predefined time intervals (for
example, a few seconds apart), or when the connection has been idle for a
given time interval (for example, a second to two seconds).
Continuity Checks at Connection or Segment End Points
End points, either connection or segment, use activation procedures to
request continuity checking with the opposite end point. The requesting end
point specifies the direction of the continuity checking (from the requesting
end point, to the requesting end point, or both directions). If the far end
