xiangping wu - huawei
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www.huawei.com
For CQR 2010 @ Vancouver2010-6-8
Wu Xiangping & Pant Himanshu
FMEA of Multi Layer Cooperation
in All IP Network
Content
• Background & Problems
• FMEA for Multi Layer Cooperation Analysis
• Summary
HUAWEI TECHNOLOGIES CO., LTD. Page 3
Background
� Growth in All-IP network demands for improvement in
operations, administration and maintenance (OAM).
� Improved OAM has to speed-up failure identification, fault
diagnosis and service restoration as real time services are
sensitive to network performance.
� A major challenge to improve OAM in All-IP network is lack of
cooperation between the different layers of the network.
HUAWEI TECHNOLOGIES CO., LTD. Page 4
The Challenges
� Fault Management
� Each layer of the All-IP network has its own fault detection and recovery
mechanisms, but there is little cooperation among them, which often causes
reliability problems.
� Too many alarms often make the network operators don’t know the exact
cause of the failures, resulting in time-consuming troubleshooting.
� Network KPIs vs. Service QoE
� What are the important KPIs for different network layers, and how do they
affect each other?
� What is the relationship between network KPIs and Service QoE?
HUAWEI TECHNOLOGIES CO., LTD. Page 5
An Example of Problem with Multi-Layer Cooperation
� In the event of a failure, e.g., a fiber cut, the restoration time in optical network may exceed 50 ms due
to the processing latency in the POS interface. This will lead to reconvergence of the IP bearer layer
and then resulting in service(s) impairment.
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B
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A
Metro WDMBackbone
WDM
Customer
side
Interfacing
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Metro WDMBackbone
WDM
Customer
side
Interfacing
Mismatching of the timers setting in different layers could cause reliability problem
HUAWEI TECHNOLOGIES CO., LTD. Page 6
KPI System Layered Architecture based on QoE
Net. Net. KPIsKPIs
Service
KQIs
Service
KPIs
Service
KPIs
Net. Net. KPIsKPIs Net. Net. KPIsKPIs
Carrier Carrier
KPIsKPIsRadio Radio KPIsKPIs
TransmissiTransmissi
on on KPIsKPIsCS CS KPIsKPIs
MSC/MGW
End-user Perceive Level
Service Application Level
Network Performance Level
End-user Level
Operator Level
Vendor Level
Node B RNC
What kind of metrics should be measured for each of the network
layers (radio, core, IP bearing and optical network layers)?
Content
• Background & Problems
• FMEA for Multi Layer Cooperation Analysis
• Summary
HUAWEI TECHNOLOGIES CO., LTD. Page 8
FMEA is A Good Way to Do the Analysis
� What will be the impact on the different network layers and on the
end-users’ services?
� What kind of protection mechanisms in different network layers will
be triggered to deal with the fault?
� What are the trigger conditions for these protection mechanisms?
� What kind of alarms will be triggered for different layers?
� How do these alarms traverse through the network layers?
� How should the alarms be correlated to restore the service with
minimum impact on end-customers?
HUAWEI TECHNOLOGIES CO., LTD. Page 9
FMEA: From Product to Network level
NetworkNetwork
Failure modes and effects
analysis (FMEA) for products
Detect Fail
Mode
Action/Follow-up
Detection
Occurrence
Probability
Severity
Prioritize Risk
Failure modes and effects
analysis (FMEA) for products
Detect Fail
Mode
Action/Follow-up
Detection
Occurrence
Probability
Severity
Prioritize Risk
Fault/EventProtection Detection PrioritySeverity Action/
Follow-UpFault/EventFault/Event
ProtectionProtection DetectionDetection PriorityPrioritySeveritySeverity Action/
Follow-Up
Action/
Follow-Up
HUAWEI TECHNOLOGIES CO., LTD. Page 10
A Practical Network for the Network FMEA
Softswitch
Layer
IP Bearer
Layer
Optical
Layer
Softswitch
Layer
IP Bearer
Layer
Optical
Layer
HUAWEI TECHNOLOGIES CO., LTD. Page 11
Network FMEA Process
IP Bearer Net.IP Bearer Net.Optical Transport Net. Softswitch Net.Fault/Event
Inte
rrup
tion
De
gra
da
tion
OTU
Recei
ve no
light
Shut
off
Laser
Insert PRBS
or all 1
downward
Trig
ge
r op
tica
l lay
er p
rote
ctio
n
<50ms
NA
>100ms
LinkdownTrigger route
reconvengence
B1/B2/B3 BER
Achieve 10-6
SCTP Link switchover
Device failure, service
interrupt
SCTP Link switchover
LOS LOF AIS
LinkDown
SCTP Link switchover
SCTP Link switchover
SCTP Link CongestionPacket loss
in IP layer
B1/B2/B3 Bit Error
Trigger Condition Alarm Protection
Interruption beyond 6s in
single plane
Interruption beyond 7.5s
in dual planes
Packet loss beyond
threshold in dual planes
IP Bearer Net.IP Bearer Net.IP Bearer Net.IP Bearer Net.Optical Transport Net.Optical Transport Net. Softswitch Net.Softswitch Net.Softswitch Net.Fault/Event
Inte
rrup
tion
De
gra
da
tion
OTU
Recei
ve no
light
Shut
off
Laser
Insert PRBS
or all 1
downward
Trig
ge
r op
tica
l lay
er p
rote
ctio
n
<50ms
NA
>100ms
LinkdownTrigger route
reconvengence
B1/B2/B3 BER
Achieve 10-6
SCTP Link switchover
Device failure, service
interrupt
SCTP Link switchover
LOS LOF AIS
LinkDown
SCTP Link switchover
SCTP Link switchover
SCTP Link CongestionPacket loss
in IP layer
B1/B2/B3 Bit Error
Trigger Condition Alarm Protection
Interruption beyond 6s in
single plane
Interruption beyond 7.5s
in dual planes
Packet loss beyond
threshold in dual planesIncreasing Time & Increasing Service Impact (# of customers affected)Increasing Time & Increasing Service Impact (# of customers affected)
HUAWEI TECHNOLOGIES CO., LTD. Page 12
Example: Fiber Cut
Cause: Accidental, ploughing or digging by utility staff
Fiber cut
Loss of connectivity
Service down-time exceeds 2 seconds.
Soft switch layer: SCTP link switchover
IP layer: reroute and re-convergence only if the protection and recovery time on optical layer
exceeds 50ms.
Optical layer: line protection or wavelength protection
Fault/EventFault/Event
SeveritySeverity
ProtectionProtection
Softswitch Layer Alarms:
▪SCTP Link Congestion
▪Post > 6 s delay on single layer
▪SCTP Link switchover
IP Layer Alarms:
▪Link Down
▪Post > 100 ms delay on optical layer
Optical Layer Alarms: LoS, LoF, & AIS
Detection
Alarms
Detection
Alarms
PriorityPriorityHigh: Impacts a large number of end-customers
Action/
Follow-Up
Action/
Follow-Up
Prevent future fiber cuts by
•burying the cable deeper in the ground
•improving liaison with utilities to prevent accidents
Fix immediate fiber cut
Content
• Background & Problems
• FMEA for Multi Layer Cooperation Analysis
• Summary
HUAWEI TECHNOLOGIES CO., LTD. Page 14
Summary
� Cooperation among network layers is important for fault
management and QoE assessment of All IP network;
� FMEA can be an useful tool for the cooperation analysis, especially
for improving the fault management.
� When a fault or event occurs, the operators can know clearly about:
� What kind of protection and restoration actions have been taken in each of the
network layers to deal with this fault or event;
� What alarms will be caused by this fault or event, and which one is the root alarm. So,
the operators can know the actions should be taken for troubleshooting.
� The analysis results can also be used for network design and plan.
Thank youwww.huawei.com
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