Abstract: When packet loss or bit errors occur on an IP RAN, alarms are reported but no protection
switching is triggered.
Sub-product Line: Network Solutions Dept. Product Type: ATN 910/950, CX600 series
[Problem Description]
On the wireless base stations: 3G base stations become unreachable to the NMS and some
E1 channels are unavailable on 2G base stations. At the same time, On the IP RAN: alarms
indicating abnormal
optical power and CRC bit error threshold-crossing are reported, and BFD status jitters occur.
Trigger conditions:
This problem occurs in either of the following conditions:
On the IP RAN, packet loss occurs on links or bit errors occur on optical ports.
Packet loss or bit errors occur on an ME network or WDM network that the IP RAN traverses.
Fault symptoms:
On the wireless base stations: The voice service quality decreases (the call drop rate increases),
some E1 channels are unavailable, and base stations become unreachable to the NMS (especially
when management channels are provided by TDM ports).
On the IP RAN: alarms indicating abnormal optical power（optical module errors） and CRC bit
error threshold-crossing（CRC error alarm notification） are reported, and BFD status jitters occur.
Judgment methods:
This problem occurs if alarms indicating abnormal optical power and CRC bit error threshold-crossing
are reported, and BFD status jitters occur.
[Root Cause]
On the ATN/CX600, alarms related to bit errors or packet loss are reported but do not trigger protection
switching.
[Impact and Risks]
On the wireless base stations: The voice service quality decreases (the call drop rate increases), some
E1 channels are unavailable, and base stations become unreachable to the NMS (especially when
management channels are provided by TDM ports).
[Measures and Solutions]
Recovery Measure:
When the protection link is functional, disable the faulty port on the working link to trigger protection
switching.
Solution:
Protection against packet loss (based on end-to-end detection) and protection against port bit errors
(based on port detection) will be provided in ATN/CX600 versions to be released in 2012Q2.
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