itu-t ethernet oam

8/10/2019 ITU-T Ethernet OAM

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ITU-T Workshop NGN and its Transport NetworksKobe, 20-21 April 2006

International Telecommunication Union

ITU-T

Ethernet OAM and ProtectionEthernet OAM and Protection

SwitchingSwitching

Hiroshi Ohta

Senior Research Engineer, NTT


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ITU-T Workshop NGN and its Transport NetworksKobe, 20-21 April 2006 2

ITU-T

Why Ethernet became popular among carriers?

o Reduced equipment costs

o Ethernet as a universal interfacing

technologyo Can carry any protocol other than IP

o Recent improvement of bridges High-speed IF (1G, 10G)

Long distance IF (-40km)

Advanced access capabilities (EFM)

More scalable bridges (802.1ad)

o ... however, OAM capability was limited.


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ITU-T

What are OAM (Operation and Maintenance) functions?

o OAM functions include:

Defect detection

Defect information notification Defect localization/isolation

System protection Performance management

o ... without these capabilities, it is almost

impossible to provide "carrier-class" services

o OAM is a "must" for carriers


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ITU-T

Recent standardization status

o ITU-T SG13 consented in Jan. 2006 meeting:

Y.1731 (Ethernet OAM)

o ITU-T SG15 consented in Feb. 2006 meeting: G.8031 (Ethernet protection)

G.8010 amendment 1 (Ethernet architecture)

G.8021 amendment 1 (Ethernet equipment)

o IEEE 802.1ag (CFM):

Draft 6.1, Under WG ballot


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ITU-T

Y.1731 (Ethernet OAM mechanisms) - 1

o Y.1731 is a superset of IEEE 802.1ag

o Both Y.1731 and IEEE 802.1ag specify

CC (Continuity Check): loss of connectivity defectdetection

LB (Loopback): defect localization

LT (Link Trace): verification of network configuration


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ITU-T

Y.1731 (Ethernet OAM mechanisms) - 2

o Y.1731 also specifies:

Fault management

AIS (Alarm Indication Signal): Alarm suppression

Test: throughput, frame loss and bit error measurement

LCK (Locked): indication of service unavailability due to

maintenance activities

MCC (Maintenance Communication Channel) EXP (Experimental OAM)

VSP (Vendor Specific OAM)

Performance management LM (Loss measurement): frame loss measurement

DM (Delay measurement): frame delay measurement


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ITU-T

Y.1731 vs. IEEE 802.1ag

o Same specifications (although the ways ofdescription are different)

CC, LB, LT

o OAM frame is identified by a specific EtherType.

IEEE 802.1ag specifies this value.

o Each OAM function is identified by the value of the"OpCode" field.

32 code points are reserved for IEEE 802.1ag

Other 32 code points for ITU-T.


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ITU-T

OAM mechanisms


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ITU-T

MEG levels

Multiple MEG levels are defined to allow running OAM in different spans


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ITU-T

CC (Continuity Check) - 1

CustomerEquipment

CustomerEquipment

Operator ABridges

Operator BBridges

ETH

ETH orSRV

1 2 3 4 5 6 7 8 9

CustomerEquipment

CustomerEquipment

Operator ABridges

Operator BBridges

ETH

ETH orSRV

1 2 3 4 5 6 7 8 9

MEP transmits CC frames periodically.

If a MEP does not receive any CC frames for 3.5 times of the CC frame

transmission interval, it declares an alarm (loss of connectivity)

MEP MIP

CC frames


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ITU-T

CC (Continuity Check) - 2

Each MEP sends CCframes to all other MEPs

Each receiving MEP

detects loss of CC frames

and unexpected CC frames

CC can be used for defect detection in multipoint-to-multipoint networks.

MEP (MEG end point)

MIP (MEG intermediate point)


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ITU-T

LB (Loopback)

-

Customer

Equipment

Customer

EquipmentOperator A

1 3 4 9

ETH

652 7 8

Operator B

Operator

Case1) MEP to MEP

Case2) MEP to MIP

LB is mainly used for connectivity verification changing the test span.


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ITU-T

LT (Link Trace)

-

CustomerEquipment

CustomerEquipmentOperator A

1 3 4 9

ETH

65

10

2 7 8

1411 12 13

Operator B

Operator

p1

p2

p2

p3

p1

p1 p1

p1

p2

p2

Target Bridge

LT is mainly used for verifying the network configuration.


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ITU-T

AIS (Alarm Indication Signal)

AIS is used for alarm suppression by notifying the bridges in downstream of

the existence of the defect and of the fact that it has already been reported

(and as such, bridges in downstream need to take no action).


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ITU-T

Test signal

Customer

Equipment

Customer

Equipment

ETH

ETH or

SRV

1 2 3 4 5 6 7 8 9

Test signal generation

Test signal detection/measurement

Supports in-service and out-of-service test

Defines Test OAM frames, which includes sequence number and PN pattern for

frame loss and bit error measurement

Bidirectional Test frame uses the same OpCode as the LB (Loopback) OAM frame


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ITU-T

G.8031 (Ethernet protection switching)

o Defines bidirectional 1+1/1:1 and unidirectional 1+1 protection switching.o This version covers point-to-point protection switching only.

ETH_FPSNC

Protection

SwitchingProcess

Protected ETH#A SNC

WEST EAST

SNC

Protection

SwitchingProcess

ETH_FF

Working Transport Entity (for ETH#A)

ETH_FF

Protection Transport Entity (for ETH#A)

ETH#A (Normal Traffic)


ETH_FPSNC

Protection

SwitchingProcess

Protected ETH#A SNC

WEST EAST

SNC

Protection

SwitchingProcess

ETH_FF

Working Transport Entity (for ETH#A)

ETH_FF

Protection Transport Entity (for ETH#A)



1:1 bidirectional protection switching architecture


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ITU-T

Conclusion

o Ethernet is now widely used by carriers.

o Its OAM capabilities were limited but ITU-T

consented Ethernet OAM and other related Draft

Recommendations recently.

o Recommendations on Ethernet architecture,

Ethernet equipment and Ethernet services are alsounder work. These standards are expected to

become available soon.

o These Ethernet-related standards enhanceadvantages and attractiveness of Ethernet as a

transport technology for NGN.

itu-t ethernet oam

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