ITU-T / ATIS Workshop
“Next Generation Technology and Standardization”
Las Vegas, 19-20 March 2006
Ethernet OAM and Protection
Switching
Hiroshi Ohta
Senior Research Engineer, NTT
ITU-T
Why Ethernet became popular among carriers?
o
o
o
o
Reduced equipment costs
Ethernet as a universal interfacing technology
Can carry any protocol other than IP
Recent improvement of bridges
•
•
•
•
o
High-speed IF (1G, 10G)
Long distance IF (-40km)
Advanced access capabilities (EFM)
More scalable bridges (802.1ad)
... however, OAM capability was limited.
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
What is 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
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
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 5.2, next TG ballot will be conducted soon
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
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 defect
detection
• LB (Loopback): defect localization
• LT (Link Trace): verification of network configuration
• AIS (Alarm Indication Signal): alarm suppression
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
Y.1731 (Ethernet OAM mechanisms) - 2
o Y.1731 also specifies:
• Fault management
— 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
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
Y.1731 vs. IEEE 802.1ag
o Same specifications (although the ways of description
are different)
• CC, LB, LT, AIS
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
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
OAM mechanisms
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
MEG levels
Multiple MEG levels are defined to allow running OAM in different spans
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
CC (Continuity Check) - 1
Customer
Equipment
1
Operator A
Bridges
2
3
Operator B
Bridges
4
5
6
7
Customer
Equipment
8
CC frames
ETH
ETH or
SRV
MEP
MIP
• 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)
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
9
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
MEP (MEG end point)
MIP (MEG intermediate point)
CC can be used for defect detection in multipoint-to-multipoint networks.
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
LB (Loopback)
Operator　Customer
Equipment
1
Operator B
Operator A
3
2
4
5
6
7
8
Customer
Equipment
9
Case1) MEP to MEP
ETH
Case2) MEP to MIP
-
LB is mainly used for connectivity verification changing the test span.
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
LT (Link Trace)
Operator　Customer
Equipment
1
Operator B
Operator A
3
p1 p2
2
4
p1
p1
Target Bridge
5
p2
p1
6
7
8
11
12
13
Customer
Equipment
9
p2
p3
10
p1
p2
ETH
-
LT is mainly used for verifying the network configuration.
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
14
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
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
Test signal
Customer
Equipment
1
2
3
4
5
6
7
8
ETH
ETH or
SRV
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
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
Customer
Equipment
9
G.8031 (Ethernet protection switching)
o
o
Defines bidirectional 1+1/1:1 and unidirectional 1+1 protection switching.
This version covers point-to-point protection switching only.
Protected ETH#A SNC
WEST
ETH#A (Normal Traffic)
EAST
Working Transport Entity (for ETH#A)
ETH#A (Normal Traffic)
Protection Transport Entity (for ETH#A)
SNC
ETH_FF
Protection
Switching
Process
ETH_FP
1:1 bidirectional protection switching architecture
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006
ETH_FF
SNC
Protection
Switching
Process
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.
ITU-T
ITU-T / ATIS Workshop “Next Generation Technology and
Standardization“
Las Vegas, 19-20 March 2006