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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 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.