Overview of BERT
Bit Error Rate Testing (BERT) is used to test the integrity of the physical line.
The interface contains on board BERT circuitry. With this circuitry, the interface software can send and detect a programmable pattern that is compliant with CCITT/ITU O.151, O.152, O.153 pseudo-random, and repetitive test patterns. BERTs allow you to test cables and signal problems in the field.
The bit error rate (BER) is determined by comparing the erroneous bits received with the total number of bits received. You can display and analyze the total number of error bits transmitted and the total number of bits received on the link. You can retrieve error statistics anytime during the BERT.
Both the total number of bits and the error bits received are available for analysis. You can select the testing period from 1 minute to 24 hours and you can also retrieve the error statistics anytime during the BERT test.
Running a BERT Test
When running a BERT test, the system expects to receive the same pattern that it transmits. To help ensure this, two common options are available:
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Use a loopback somewhere in the link or network
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Configure remote testing equipment to transmit the same BERT test pattern at the same time.
The BERT runtime engine can be kept running until the interval completes or can be stopped by unconfiguring it anytime.
Types of BERT
BERT is supported in two directions:
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Line - supports BERT in TDM direction
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System - supports BERT in PSN direction
BERT engines uses different BERT patterns for transmission for each mode. The supported BERT patterns on each card is described.
BERT Restrictions
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BERT is not supported on the following modes:
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T3—Framing M-13, non-channelized
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E3—Framing G832, channelized
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When the BERT is initiated with pattern 0s and 1s from the local end and the loopback local is applied from the far end, then the BERT syncing does not happen. Since the BERT process is asserted as LOS alarms for all 0s and AIS alarms for all 1s BERT patterns. Whereas the BERT syncing behaves properly when the BERT is initiated from both the local and the far end.
For all 1s on T3 or E3, the BERT behaviour is not asserted as AIS and the BERT syncing happens as usual.
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In the unframed mode, BERT sync is not stable and may generate alarms until Cisco IOS XE Fuji 16.9.4.
Note
Framing type should be similar in all routers end to end.
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System BERT is not supported for any pattern in framed SATOP for releases earlier to Cisco IOS XE 17.13.1.
Starting with Cisco IOS XE 17.13.1, system BERT is supported for any pattern in the framed SAToP on T1/E1 interface module.
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System BERT is not configurable, without cem-group configuration.
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Path modes, unframed modes, and concatenation modes are not supported.
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The default BERT pattern supported is PRBS. The QRSS pattern is supported only on T1 or E1 level and the STS-1E path level for pattern 2^20-O151.
BERT Restrictions for Cisco IOS XE Bengaluru 17.4.1 release
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When the BERT is initiated from the local end and the loopback local is applied from the far end, then BERT syncing does not happen. Since the BERT process is asserted as LOS alarms for all 0s and AIS alarms for all 1s BERT patterns. Whereas the BERT syncing behaves properly when the BERT is initiated from both the local and the far end.
BERT Patterns on T3/E3 Interface Module
Bit error rate testing (BERT) is supported on T3/E3 interfaces.
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You can run 16 BERTs at a time.
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The test can be either of the T1/E1 or the T3/E3 interface.
|
Feature Name |
Release Information |
Description |
|---|---|---|
| Support for all 0s and 1s BERT Patterns |
Cisco IOS XE Bengaluru 17.4.1 |
Support for all 0s and 1s BERT patterns on T3 or E3 interfaces. |
| Support for 3-in-24 BERT Patterns | Cisco IOS XE Dublin 17.11.1 |
Support for 3-in-24 BERT patterns on T3 or E3 interfaces. |
The BERT patterns on the 48-port T3/E3 interface module are:
|
Keyword |
Description |
|---|---|
|
All 1s 1 |
Pseudo-random binary test pattern consisting of all 1’s that is used to test alternating line volt and repeaters. |
|
All 0s |
Pseudo-random binary test pattern consisting of all 0’s that is used for test line coding. |
|
2^15-1 O.151 |
Pseudo-random O.151 test pattern consisting of a maximum of 14 consecutive zeros and 15 consecutive ones. The length of this pattern is 32,768 bits. |
|
2^20-O.151 |
Pseudo-random O.151 test pattern consisting of a maximum of 19 consecutive zeros and 20 consecutive ones. The length of this pattern is 1,048,575 bits. |
|
2^20-O.153 |
Pseudo-random O.153 test pattern consisting of a maximum of 19 consecutive zeros and 20 consecutive ones. The length of this pattern is 1,048,575 bits. |
|
2^23-1 O.151 |
Pseudo-random 0.151 test pattern consisting of a maximum of 22 consecutive zeros and 23 consecutive ones. The length of this pattern is 8,388,607 bits. |
|
2^9 2 |
Pseudo-random binary test pattern consisting of a maximum of eight consecutive zeros and nine consecutive ones. The length of this pattern is 511 bits. |
|
2^11 3 |
Pseudo-random binary test pattern consisting of a maximum of ten consecutive zeros and eleven consecutive ones. The length of this pattern is 2048 bits. |
|
3-in-24 4 |
Pseudo-random binary test pattern consisting of repeating 24-bit sequence that contains three ones, fifteen consecutive zeros, and 12.5 percent average one’s density. |
Note |
If All 1's BERT pattern is tested on the system side, then ensure that you need to start all 1's pattern from both sides of the end points. Configuring BERT on one side and loopback on other side of the end points is not supported. The router treats all 1's pattern as AIS alarm and BERT will not come in sync with the other side configuration of the end point. |
BERT for CESoPSN
BERT is supported at the TDM side and pseudowire side. BERT can be used either at NxDS0 or DS1 but not together.
BERT is supported on following controllers:
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T1—NxDS0, DS1
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T3—NxDS0, DS1 (channelised), clear channel DS3.
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OCX—NxDS0, DS1 (channelised),DS3(channelised), clear channel DS3,STS1,STS-nc,VT-1.5,VT1.5 T1
Configuring BERT - T3 or E3 Interfaces for SAToP
Before You Begin
Before you configure BERT for clear channel T3 or E3 interfaces, ensure that controller and CEM are configured.
enable
configure terminal
controller t3 0/0/1
no channelized
bert pattern 0s interval 30 direction line
exit
enable
configure terminal
controller t3 0/0/1
channelized
t1 1 bert pattern 0s interval 30 direction line
exit
Note |
To terminate a BERT test during the specified test period, use the no bert command. |
You can view the results of a BERT test at the following points of time:
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After you terminate the test using the no bert command
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After the test runs completely
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Anytime during the test (in real time)
Verifying the BERT for T3/E3 Interfaces
Router# show controllers t3 0/4/40 | sec BERT
BERT test result (running)
Test Pattern : 2^15, Status : Not Sync, Sync Detected : 0
DSX3 BERT direction : Line
Interval : 5 minute(s), Time Remain : 3 minute(s)
Bit Errors (since BERT started): 0 bits,
Bits Received (since BERT started): 0 Kbits
Bit Errors (since last sync): 0 bits
Bits Received (since last sync): 0 Kbits
Router# sh controller t3 0/3/0 | be T1 1
T1 1 is up
timeslots:
FDL per AT&T 54016 spec.
Receiver is getting AIS.
Framing is ESF, Clock Source is Internal
BERT test result (running)
Test Pattern : 2^23, Status : Not Sync, Sync Detected : 0
Interval : 5 minute(s), Time Remain : 00:01:44
Bit Errors (since BERT started): 299 Mbits,
Bits Received (since BERT started): 299 Mbits
Bit Errors (since last sync): 0 bits
Bits Received (since last sync): 0 Kbits
Direction : Line
Data in current interval (250 seconds elapsed):
Near End
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs
0 Unavailable Secs, 0 Stuffed Secs
0 Path Failures, 0 SEF/AIS Secs
Far End
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs
0 Unavailable Secs 0 Path Failures
Data in Interval 1:
Near End
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 2 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
2 Errored Secs, 0 Bursty Err Secs, 2 Severely Err Secs
0 Unavailable Secs, 0 Stuffed Secs
1 Path Failures, 2 SEF/AIS Secs
Far End
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 2 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
3 Errored Secs, 0 Bursty Err Secs, 3 Severely Err Secs
0 Unavailable Secs 0 Path Failures
Total Data (last 1 15 minute intervals):
Near End
0 Line Code Violations,0 Path Code Violations,
0 Slip Secs, 2 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,
2 Errored Secs, 0 Bursty Err Secs, 2 Severely Err Secs
0 Unavailable Secs, 0 Stuffed Secs
1 Path Failures, 2 SEF/AIS Secs
Far End
0 Line Code Violations,0 Path Code Violations
0 Slip Secs, 2 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,
3 Errored Secs, 0 Bursty Err Secs, 3 Severely Err Secs
0 Unavailable Secs, 0 Path Failures
Configuring BERT - T3 or E3 Interfaces for CESoPSN
Before You Begin
Before you configure BERT for clear channel T3 or E3 interfaces, ensure that the controller and CEM are configured.
To run a BERT on the T3 interface, use the following commands:
configure terminal
controller t3 0/5/0
t1 1 bert timeslots 1 pattern 2^15 interval 1
To run a BERT on the E3 interface, use the following commands:
config terminal
controller e3 0/5/0
e1 1 bert timeslots 1 pattern 2^15 interval 1
Note |
To terminate a BERT test during the specified test period, use the no bert command. |
You can view the results of a BERT test at the following points of time:
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After you terminate the test using the no bert command
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After the test runs completely
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Anytime during the test (in real time)
Verifying BERT for CESoPSN on T3 or E3 Interface
Router# show controllers t3 0/5/0
T3 0/5/0 is up.
Hardware is -48T3E3-CE
Applique type is Channelized T3
No alarms detected.
MDL transmission is disabled
FEAC code received: No code is being received
Framing is C-BIT Parity, Line Code is B3ZS, Cablelength Short less than 225ft
BER thresholds: SF = 10e-3 SD = 10e-6
Clock Source is internal
Equipment customer loopback
Data in current interval (240 seconds elapsed):
Near End
0 Line Code Violations, 0 P-bit Coding Violations
0 C-bit Coding Violations, 0 P-bit Err Secs
0 P-bit Severely Err Secs, 0 Severely Err Framing Secs
0 Unavailable Secs, 0 Line Errored Secs
0 C-bit Errored Secs, 0 C-bit Severely Errored Secs
0 Severely Errored Line Secs, 0 Path Failures
0 AIS Defect Secs, 0 LOS Defect Secs
Far End
0 Errored Secs, 0 Severely Errored Secs
0 C-bit Unavailable Secs, 0 Path Failures
0 Code Violations, 0 Service Affecting Secs
Data in Interval 1:
Near End
0 Line Code Violations, 0 P-bit Coding Violations
0 C-bit Coding Violations, 0 P-bit Err Secs
0 P-bit Severely Err Secs, 0 Severely Err Framing Secs
20 Unavailable Secs, 20 Line Errored Secs
0 C-bit Errored Secs, 0 C-bit Severely Errored Secs
20 Severely Errored Line Secs, 1 Path Failures
0 AIS Defect Secs, 20 LOS Defect Secs
Far End
0 Errored Secs, 0 Severely Errored Secs
0 C-bit Unavailable Secs, 0 Path Failures
0 Code Violations, 0 Service Affecting Secs
Total Data (last 1 15 minute intervals):
Near End
0 Line Code Violations, 0 P-bit Coding Violations,
0 C-bit Coding Violations, 0 P-bit Err Secs,
0 P-bit Severely Err Secs, 0 Severely Err Framing Secs,
20 Unavailable Secs, 20 Line Errored Secs,
0 C-bit Errored Secs, 0 C-bit Severely Errored Secs
20 Severely Errored Line Secs, 1 path failures
0 AIS Defect Secs, 20 LOS Defect Secs
Far End
0 Errored Secs, 0 Severely Errored Secs
0 C-bit Unavailable Secs, 0 Path Failures
0 Code Violations, 0 Service Affecting Secs
T1 1 is down
timeslots: 1-24
FDL per AT&T 54016 spec.
Receiver has remote alarm.
Framing is ESF, Clock Source is Recovered 1
BERT running on timeslots 1,
BERT test result (running)
Test Pattern : 2^15, Status : Sync, Sync Detected : 0
Interval : 0 minute(s), Time Remain : 00:00:37
Bit Errors (since BERT started): 0 bits,
Bits Received (since BERT started): 137 Kbits
Bit Errors (since last sync): 0 bits
Bits Received (since last sync): 137 Kbits
Direction : Line
Near End
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs
0 Unavailable Secs, 0 Stuffed Secs
0 Path Failures, 0 SEF/AIS Secs
Far End
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs
0 Unavailable Secs 0 Path Failures
Data in Interval 1:
Near End
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 2 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
2 Errored Secs, 0 Bursty Err Secs, 2 Severely Err Secs
0 Unavailable Secs, 0 Stuffed Secs
1 Path Failures, 2 SEF/AIS Secs
Far End
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 2 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
3 Errored Secs, 0 Bursty Err Secs, 3 Severely Err Secs
0 Unavailable Secs 0 Path Failures
Total Data (last 1 15 minute intervals):
Near End
0 Line Code Violations,0 Path Code Violations,
0 Slip Secs, 2 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,
2 Errored Secs, 0 Bursty Err Secs, 2 Severely Err Secs
0 Unavailable Secs, 0 Stuffed Secs
1 Path Failures, 2 SEF/AIS Secs
Far End
0 Line Code Violations,0 Path Code Violations
0 Slip Secs, 2 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,
3 Errored Secs, 0 Bursty Err Secs, 3 Severely Err Secs
0 Unavailable Secs, 0 Path Failures
You can view the results of a BERT test at the following times:
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After you terminate the test using the no bert command
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After the test runs completely
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Anytime during the test (in real time)
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