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.
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 for SAToP
BERT is supported for both unframed and framed modes.
Configuring BERT for SAToP
Before You Begin
Before you run BERT test, you must configure card type and controller.
enable
configure terminal
controller t10/1/1
bert pattern 2^11 interval 5 direction line/system
exit
Note |
To terminate a BERT test during the specified test period, use the no bert command. |
Verifying BERT Configuration for SAToP
Use the following command to verify the BERT configuration for T1/E1 interfaces:
Router# show controllers t1 0/1/1
T1 0/1/1 is up.
Applique type is -48T1E1-CE
Cablelength is short 110
DSX1 BERT pattern : 2^11
DSX1 BERT direction : Line
DSX1 BERT sync : no sync
DSX1 BERT sync count : 0
DSX1 BERT interval : 5
DSX1 BERT time remain : 2
DSX1 BERT total errs : 0
DSX1 BERT total k bits: 0
DSX1 BERT errors (last): 0
DSX1 BERT k bits (last): 0
Last clearing of BERT counters never
No alarms detected.
alarm-trigger is not set
Soaking time: 3, Clearance time: 10
AIS State:Clear LOS State:Clear LOF State:Clear
Framing is ESF, FDL is ansi, Line Code is B8ZS, Clock Source is Line.
BER thresholds: SF = 10e-3 SD = 10e-6
Data in current interval (230 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 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, 0 Fr Loss Secs, 14 Line Err Secs, 0 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 15 Unavailable Secs
1 Path Failures, 0 SEF/AIS Secs
Far End Data
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 4 Fr Loss Secs, 2 Line Err Secs, 0 Degraded Mins
4 Errored Secs, 0 Bursty Err Secs, 4 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, 0 Fr Loss Secs, 14 Line Err Secs, 0 Degraded Mins,
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 15 Unavailable Secs
1 Path Failures, 0 SEF/AIS Secs
Far End
0 Line Code Violations, 0 Path Code Violations,
0 Slip Secs, 4 Fr Loss Secs, 2 Line Err Secs, 0 Degraded Mins,
4 Errored Secs, 0 Bursty Err Secs, 4 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)
Framed SAToP System BERT
| Feature Name | Release Information | Description |
|---|---|---|
| Framed SAToP System BERT |
Cisco IOS XE 17.13.1 |
You can configure SATOP system BERT with framing under CEM circuits on T1 or E1 interfaces and verify if the BERT is stable and transmitted end-to-end. |
System BERT is used between PEs on the core side. This feature is supported only on the 48-port T1/E1 Interface module. You can run a maximum of 16 BERTs at a time.
Note |
For Cisco ASR 920 series aggregation services routers, the framed SAToP system BERT is supported only on the Cisco ASR-920-12SZ-IM router with A900-IMA3G-IMSG Interface Module. |
Restrictions for Framed SAToP System BERT
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Framing change is not allowed while bert is running
Configuring Framed SAToP System BERT
You can configure the framed SAToP system BERT in the following scenarios:
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Scenario 1: PE1—core—PE2
CEM system BERT is configured on both PE1 and PE2.
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Scenario 2: PE1—core—PE2
CEM system BERT is configured on PE1 and loopback local is configured on PE2.
Scenario 1: PE1—CORE—PE2
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Configure system BERT on PE1.
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Configure system BERT on PE2.
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Configure cross-connect on core.
Configure System BERT on PE1
PE1#config terminal
PE1(config)#controller T1 0/4/35
PE1(config-controller)#bert pattern 3-in-24 interval 40 direction system
PE1(config)#end
Configure System BERT on PE2
PE1#config terminal
PE1(config)#controller T1 0/3/17
PE1(config-controller)#bert pattern 3-in-24 interval 40 direction system
PE1(config)#end
Configure Cross Connect on Core
Ensure that the cross connection is UP before configuring BERT.
Scenario 2: PE1—core—PE2
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Configure system BERT on T1 at the PE1 side.
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Apply loopback local on PE2.
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Configure cross-connect on core.
PE1#show run | s 0/4/35
controller T1 0/4/35
threshold sd-ber 6
threshold sf-ber 3
framing esf
linecode b8zs
cablelength short 110
no snmp trap link-status
cem-group 0 framed
interface CEM0/4/35
no ip address
cem 0
Configure System BERT on PE1
PE1#config terminal
PE1(config)#controller T1 0/4/35
PE1(config-controller)#bert pattern 3-in-24 interval 40 direction system
PE1(config)#end
Apply Loopback Local on PE2
PE2(config-controller)#controller T1 0/4/0
PE2(config-controller)#loopback local
PE2(config-controller)#end
Configure Cross Connect on Core
Ensure that the cross connection is UP before configuring BERT.
Verifying Framed SAToP System BERT
Use the following show commands to verify the framed SAToP system BERT configuration:
Scenario 1: PE1—CORE—PE2
Verify the configuration on PE1
PE1#show xconnect all
Legend: XC ST=Xconnect State S1=Segment1 State S2=Segment2 State
UP=Up DN=Down AD=Admin Down IA=Inactive
SB=Standby HS=Hot Standby RV=Recovering NH=No Hardware
XC ST Segment 1 S1 Segment 2 S2
------+---------------------------------+--+---------------------------------+--
UP pri mpls 2.2.2.2:500 UP ac CE0/4/35:0(SATOP T1) UP
PE1#show controller T1 0/4/35 | sec BERT
DSX1 BERT test result: (running)
DSX1 BERT pattern : 3-in-24
DSX1 BERT direction : System
DSX1 BERT sync : sync
DSX1 BERT sync count : 1
DSX1 BERT interval : 100
DSX1 BERT time remain : 01:39:52
DSX1 BERT total errs : 0
DSX1 BERT total k bits: 10759
DSX1 BERT errors (last): 0
DSX1 BERT k bits (last): 10759
Last clearing of BERT counters never
Verify the configuration on PE2
PE1#show xconnect all
Legend: XC ST=Xconnect State S1=Segment1 State S2=Segment2 State
UP=Up DN=Down AD=Admin Down IA=Inactive
SB=Standby HS=Hot Standby RV=Recovering NH=No Hardware
XC ST Segment 1 S1 Segment 2 S2
------+---------------------------------+--+---------------------------------+--
UP pri mpls 3.3.3.3:500 UP ac CE0/3/17:0(SATOP T1) UP
PE1#show controller T1 0/3/17 | sec BERT
DSX1 BERT test result: (running)
DSX1 BERT pattern : 3-in-24
DSX1 BERT direction : System
DSX1 BERT sync : sync
DSX1 BERT sync count : 1
DSX1 BERT interval : 100
DSX1 BERT time remain : 01:39:52
DSX1 BERT total errs : 0
DSX1 BERT total k bits: 10759
DSX1 BERT errors (last): 0
DSX1 BERT k bits (last): 10759
Last clearing of BERT counters never
Scenario 2: PE1—CORE—PE2
Verify the configuration on PE1
PE1#show xconnect all
Legend: XC ST=Xconnect State S1=Segment1 State S2=Segment2 State
UP=Up DN=Down AD=Admin Down IA=Inactive
SB=Standby HS=Hot Standby RV=Recovering NH=No Hardware
XC ST Segment 1 S1 Segment 2 S2
------+---------------------------------+--+---------------------------------+--
UP pri mpls 2.2.2.2:500 UP ac CE0/4/35:0(SATOP T1) UP
PE1#show controller T1 0/4/35 | sec BERT
DSX1 BERT test result: (running)
DSX1 BERT pattern : 3-in-24
DSX1 BERT direction : System
DSX1 BERT sync : sync
DSX1 BERT sync count : 1
DSX1 BERT interval : 100
DSX1 BERT time remain : 01:39:52
DSX1 BERT total errs : 0
DSX1 BERT total k bits: 10759
DSX1 BERT errors (last): 0
DSX1 BERT k bits (last): 10759
Last clearing of BERT counters never
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 for CESoPSN
Before You Begin
Before you run BERT test, you must configure card type and controller.
enable
configure terminal
controller t10/1/1
bert pattern 2^11 interval 5 direction line/system timeslots value speed
exit
Note |
To terminate a BERT test during the specified test period, use the no bert command. |
Verifying BERT Configuration for CESoPSN
Router# show controllers t1 0/1/32
T1 0/1/32 is up
Applique type is NCS4200-48T1E1-CE
Cablelength is short 110
DS0 Bert enabled on the following timeslots : 1-2
Speed : 64 kpbs
DSX1 BERT test result: (running)
DSX1 BERT pattern : 2^15
DSX1 BERT direction : Line
DSX1 BERT sync : sync
DSX1 BERT sync count : 1
DSX1 BERT interval : 1
DSX1 BERT time remain : 00:00:55
DSX1 BERT total errs : 0
DSX1 BERT total k bits: 512
DSX1 BERT errors (last): 0
DSX1 BERT k bits (last): 512
Last clearing of BERT counters never
No alarms detected.
alarm-trigger is not set
Soaking time: 3, Clearance time: 10
AIS State:Clear LOS State:Clear LOF State:Clear
Framing is ESF, FDL is ansi, Line Code is B8ZS, Clock Source is Line.
BER thresholds: SF = 10e-3 SD = 10e-6
Data in current interval (230 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 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, 0 Fr Loss Secs, 14 Line Err Secs, 0 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 15 Unavailable Secs
1 Path Failures, 0 SEF/AIS Secs
Far End Data
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 4 Fr Loss Secs, 2 Line Err Secs, 0 Degraded Mins
4 Errored Secs, 0 Bursty Err Secs, 4 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, 0 Fr Loss Secs, 14 Line Err Secs, 0 Degraded Mins,
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 15 Unavailable Secs
1 Path Failures, 0 SEF/AIS Secs
Far End
0 Line Code Violations, 0 Path Code Violations,
0 Slip Secs, 4 Fr Loss Secs, 2 Line Err Secs, 0 Degraded Mins,
4 Errored Secs, 0 Bursty Err Secs, 4 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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