ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006

International Telecommunication UnionITU-T

Ethernet OAM and Protection Ethernet OAM and Protection SwitchingSwitching

Hiroshi OhtaSenior Research Engineer, NTT

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 2

ITU-T

Why Ethernet became popular among carriers?

o Reduced equipment costso Ethernet as a universal interfacing

technologyo Can carry any protocol other than IPo 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.

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 3

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

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 4

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

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 5

ITU-T

Y.1731 (Ethernet OAM mechanisms) - 1

o Y.1731 is a superset of IEEE 802.1ago Both Y.1731 and IEEE 802.1ag specify

• CC (Continuity Check): loss of connectivity defect detection

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

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 6

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

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 7

ITU-T

Y.1731 vs. IEEE 802.1ag

o Same specifications (although the ways of description 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.

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 8

ITU-T

OAM mechanisms

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 9

ITU-T

MEG levels

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

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 10

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

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 11

ITU-T

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)

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 12

ITU-T

LB (Loopback)

-

CustomerEquipment

CustomerEquipmentOperator 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.

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 13

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.

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 14

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).

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 15

ITU-T

Test signal

CustomerEquipment

CustomerEquipment

ETH

ETH orSRV

1 2 3 4 5 6 7 8 9

Test signal generationTest 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

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 16

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 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_FPSNC 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

ITU-T Workshop “NGN and its Transport Networks“Kobe, 20-21 April 2006 17

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 also under work. These standards are expected to become available soon.

o These Ethernet-related standards enhance advantages and attractiveness of Ethernet as a transport technology for NGN.