Ethernet OAM and Protection Ethernet OAM and Protection Switching - - PowerPoint PPT Presentation

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I nternational Telecom m unication Union

ITU-T

Ethernet OAM and Protection Ethernet OAM and Protection Switching Switching

Hiroshi Ohta

Senior Research Engineer, NTT

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ITU-T

W hy Ethernet becam e popular am ong carriers?

• Reduced equipment costs
• Ethernet as a universal interfacing

technology

• Can carry any protocol other than IP
• Recent improvement of bridges
• High-speed IF (1G, 10G)
• Long distance IF (-40km)
• Advanced access capabilit ies (EFM)
• More scalable bridges (802.1ad)
• ... however, OAM capability was limited.

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W hat are OAM ( Operation and Maintenance) functions?

• OAM functions include:
• Defect detection
• Defect information notification
• Defect localization/ isolation
• System protection
• Performance management
• ... without these capabilities, it is almost

impossible to provide "carrier-class" services

• OAM is a "must" for carriers

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Recent standardization status

• ITU-T SG13 consented in Jan. 2006 meeting:
• Y.1731 (Ethernet OAM)
• ITU-T SG15 consented in Feb. 2006 meeting:
• G.8031 (Ethernet protection)
• G.8010 amendment 1 (Ethernet architecture)
• G.8021 amendment 1 (Ethernet equipment)
• IEEE 802.1ag (CFM):
• Draft 6.1, Under WG ballot

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Y.1 7 3 1 ( Ethernet OAM m echanism s) - 1

• Y.1731 is a superset of IEEE 802.1ag
• Both Y.1731 and IEEE 802.1ag specify
• CC (Continuity Check): loss of connectivity defect

detect ion

• LB (Loopback): defect localization
• LT (Link Trace): verification of network configuration

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Y.1 7 3 1 ( Ethernet OAM m echanism s) - 2

• Y.1731 also specifies:
• Fault management

—AIS (Alarm Indication S ignal): 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) —VS P (Vendor S pecific OAM)

• Performance management

—LM (Loss measurement): frame loss measurement —DM (Delay measurement): frame delay measurement

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Y.1 7 3 1 vs. I EEE 8 0 2 .1 ag

• Same specifications (although the ways of

description are different)

• CC, LB, LT
• OAM frame is identified by a specific EtherType.

IEEE 802.1ag specifies this value.

• 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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OAM mechanisms

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MEG levels

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

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CC ( Continuity Check) - 1

Customer Equipment Customer Equipment Operator A Bridges Operator B Bridges

ETH ETH or SRV

1 2 3 4 5 6 7 8 9

Customer Equipment Customer Equipment Operator A Bridges Operator B Bridges

ETH ETH or SRV

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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CC ( Continuity Check) - 2

Each MEP sends CC frames 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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LB ( Loopback)

• Customer

Equipment Customer Equipment Operator A 1 3 4 9 ETH 6 5 2 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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LT ( Link Trace)

• Customer

Equipment Customer Equipment Operator A 1 3 4 9 ETH 6 5 10 2 7 8 14 11 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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AI S ( Alarm I ndication 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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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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G.8 0 3 1 ( Ethernet protection sw itching)

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

ETH_FP SNC Protection Switching Process Protected ETH#A SNC WEST EAST SNC Protection Switching Process ETH_FF Working Transport Entity (for ETH#A) ETH_FF Protection Transport Entity (for ETH#A) ETH#A (Normal Traffic) ETH#A (Normal Traffic) ETH_FP SNC Protection Switching Process Protected ETH#A SNC WEST EAST SNC Protection Switching Process ETH_FF Working Transport Entity (for ETH#A) ETH_FF Protection Transport Entity (for ETH#A) ETH#A (Normal Traffic) ETH#A (Normal Traffic)

1:1 bidirectional protection switching architecture

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Conclusion

• Ethernet is now widely used by carriers.
• Its OAM capabilities were limited but ITU-T

consented Ethernet OAM and other related Draft Recommendations recently.

• Recommendations on Ethernet architecture,

Ethernet equipment and Ethernet services are also under work. These standards are expected to become available soon.

• These Ethernet-related standards enhance

advantages and attractiveness of Ethernet as a transport technology for NGN.