Performance measurements
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Introduction
In performance monitoring, the integrity of a signal is continuously verified as it is
carried along the fiber. The results of this measurement is analyzed, compared against
predefined threshold values for errors, stored on the NE and displayed on the ITM CIT
as performance monitoring data. The thresholds must be defined according to your
maintenance policy and then configured on the ITM CIT.
Performance measurements can be done on incoming:
• VC-12, VC11, VC4, and VC-3 terminating in the unit;
• MS1 and MS4;
• P12 (ISDN) in egress (SDH to PDH) and ingress (PDH to SDH) ways;
• as well as on LAN or WAN ports.
To measure LAN performance parameters on the 1643 AM or 1643 AMS, a
TransLAN
®
card is required in Tributary slot 2. This card offers four Ethernet LAN
ports of different bitrates (2, 4, 6, 8 or 10 Mbits/s).
How to measure PM
Even Bit Interleaved Parity (BIP) is the method used to measure performance. The
signal integrity is indicated by bit errors in the interface signal.
This method looks at the content of the signal. When a signal is transmitted a BIP
check is performed on each STM frame. In this check, the amount of “1” and “0” of
the payload is calculated. If the result is an even number, then a “0” is put in the
B-Byte of the overhead section of the STM-n next frame. Otherwise if the result is an
odd number, then a “1” is put in the B-Byte. At the termination point, a BIP check is
performed again on the payload of the received signal and the outcome is compared to
the value at transmission.
If there is a discrepancy between the two readings, an error is concluded. Proactive
maintenance events are called Threshold Crossing Alerts and are typically raised when
too many errored seconds (number of errored frames in one second) are being detected.
Parity violations are counted to derive performance data in 15 minutes, and 24 hours
measuring intervals, called bins.
Where to measure PM
The quality of the transmission in the network is measured at each termination points,
that is where signals are terminated in the network element.
A VC-12 is for example terminated at the PDH 2 Mbit/s physical interface. At the
process of termination the appropriate overhead bytes are terminated to provide
information about the signal being terminated. Selecting the appropriate TPs to be
monitored during the configuration step requires preparation and planning.
Performance monitoring
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10-8
Alcatel-Lucent - Proprietary
See notice on first page
365-312-807R7.2
Issue 4, May 2007
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