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© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 1
MPLS –TP Fault OAM
draft-sfv-mpls-tp-fault-00
George [email protected] November, 2009
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 2
Fault Notification
Various server layer faults need to be communicated to their clients so that alarms can be suppressed and/or corrective action taken at the client layer
Three distinct server layer faults have been identifiedAlarm Indication Signal (AIS)
Link Down Indication (LDI)
Lock Report (LKR)
These fault OAM messages are sent from server layer MEPs to client layer MEPs to report the occurrence of a fault
The fault OAM messages are sent in the direction away from the fault
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 3
Sending Fault OAM Messages
MEPs exist at link interfaces (server layer) over which MPLS-TP LSPs (client layer) are cross connected
Note that this includes an MPLS-TP tunnel interfaces if it were used as a link
A MEP is aware of all of its xconnected MPLS-TP LSPs via configuration or signaling
When a fault occurs on a link, the MEP associated with the link interface sends fault messages on each of the xconnected LSPs
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 4
Fault Generation (LDI example)
MEP
PE1PE1 P2P2 P3P3 PE4PE4
TP-LSP TP-LSP
Physical Links Physical Links
Sk
TP LSP 1 is routed PE1 – P2 – P3 – PE4
Link P2 - P3 fails
At P2 IF Down detected by MEP L0; At P3 IF Down detected by MEP L1
MEP L0 sends LDI to MEP So; MEP L1 sends LDI to MEP Sk
XXIF
DownIF
DownIF
DownIF
Down
LDILDI
So MPLS-TP LSP 1
LDILDI
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 5
Alarm Indication Signal (AIS)
AIS may be sent whenever there is a transient defect in the server layer, e.g. during a protection switch
AIS must not be sent if the server layer enters a down state (instead LDI is sent)
When AIS is received by an MPLS-TP LSP’s MEP it is used to suppresses alarms due to CC failure
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 6
Link Down Indication (LDI)
LDI must be sent whenever the server layer enters a down state
When LDI is received by an MPLS-TP LSP’s MEP it is used to
Suppresses alarms due to any CC failure
If no CC failure has occurred (i.e. BFD is up), transition BFD to down with a diag “Path Down”
Note: the above behaviors are examples and are not specified in this draft
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 7
Indicates that the Tunnel or Link has been Administratively Locked and is unavailable to carry client traffic
Otherwise same as LDI
Lock Report (LKR)
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 8
New ACH Codepoint with TLV Header
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | 0xHH MPLS-TP Fault Management |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACH TLV Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~
~ zero or more ACH TLVs ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~
~ MPLS-TP Fault Message ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 9
AIS, LDI and LKR message format 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vers |Flgs |R| OpCode | Refresh Timer | Total TLV Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLVs |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OpCode = AIS, LDI or LKR
R-flag indicates removal of the fault
Refresh time indicates frequency of transmission
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 10
ACH TLVs
Optionally carries Global-ID or ICC
Optionally carries IF_ID of failed interface
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 11
Default sending behavior
OpCode set to AIS, LDI or LKR
R-flag set to zero (not used)
Refresh Timer set to a default value
Message continuously transmitted until condition clears
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 12
OpCode set to AIS, LDI or LKR
R-flag set to zero
Refresh Timer set to configured value
Message transmitted three times at one second intervals
Message continuously transmitted according to refresh timer until condition clears
Optional Behavior
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 13
Used when refresh timer is set long
When fault / lock condition clearsSet R-bit to one
Transmit three times at refresh interval of 1 sec
Optional Clearing Behavior
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 14
Transitioning from AIS to LDI
If the optional sending procedures are being used, the same procedures apply to LDI
The LDI message is transmitted three times at one second intervals before falling back to the advertised refresh interval
There is no need to clear the AIS message
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 15
Suppress alarms due to BFD
Optionally propagate the Alarm (next slide)Note: propagation to TP LSPs is post phase 1 (as we are not supporting hierarchical MPLS-TP Tunnels in phase 1)
Receiving AIS
© 2006 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 16
Next Steps
Adopt as a work group draft
Polish
