Internet DRAFT - draft-ama-mpls-fm-rdi
draft-ama-mpls-fm-rdi
Routing Working Group A. Mishra
Internet-Draft O3b Networks
Intended status: Standards Track M. Jethanandani
Expires: May 25, 2018
A. Saxena
Ciena Corporation
November 21, 2017
Reverse Defect Indicator for MPLS FM OAM
draft-ama-mpls-fm-rdi-00.txt
Abstract
This document describes extensions to the MPLS Fault Management
Operations, Administration, and Management (MPLS FM OAM) in RFC 6427
[RFC6427] to support Remote Defect Indication (RDI) functionality.
Specifically, it describes a mechanism for propagating MPLS FM OAM
messages to the upstream Label Edge Router (LER) in MPLS-TP [RFC5921]
bi-directional (associated and co-routed) Label Switched Paths
(LSPs).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Reverse Defect Indicator (RDI) . . . . . . . . . . . . . . . 2
3. Theory of Operations . . . . . . . . . . . . . . . . . . . . 3
3.1. RDI Operation in Associated Bidirectional LSPs . . . . . 3
3.2. RDI Operation in Co-routed Bidirectional LSPs . . . . . . 4
4. IANA Requirements . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Consideration . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The MPLS Fault Management Operations, Administration, and Management
(MPLS FM OAM) in RFC 6427 [RFC6427] describes a method to identify
faults in MPLS transport networks, and a protocol to notify the
upstream Label Edge Router (LER). However, in the case of MPLS-TP
[RFC5921] bi-directional Label Switched Paths (LSPs), the fault must
be coordinated on both, the upstream LER and the downstream LER
(which is the upstream LER for the reverse path).
In typical scenario, the Bidirectional Forwarding Detection (BFD)
protocol, as described in RFC 5880 [RFC5880], detects the fault
signaled by MPLS FM OAM on the upstream LER and propagates the fault
on the reverse LSP to the other MPLS-TP LSP LER. This allows the two
MPLS-TP LERs to coordinate failover to backup LSPs.
This document proposes a mechanism to achieve MPLS FM OAM fault
propagation on the MPLS-TP reverse LSP using a Reverse Defect
Indicator (RDI) MPLS FM OAM message. This allows fast fault
coordination between the bidirectional LSP end-points when the use of
BFD is not feasible.
2. Reverse Defect Indicator (RDI)
The functionality proposed for MPLS FM OAM RDI is achieved by adding
a RDI-flag in the MPLS Fault OAM message .
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+-+-+-+-+-+---+-+-+
|Reserved |RDI|L|R|
+-+-+-+-+-+---+-+-+
Figure 1: RDI-Flag in MPLS FM OAM Flags
where:
L-Flag and R-Flag are as defined in RFC 6427 [RFC6427].
RDI-Flag: Reverse Defect Indication Flag. The RDI-Flag is clear in
the common MPLS FM OAM messages as defined in RFC 6427 [RFC6427].
The RDI-Flag is set to indicate that the message is MPLS FM OAM RDI.
3. Theory of Operations
3.1. RDI Operation in Associated Bidirectional LSPs
------------------>
Forward LSP
+-------+ +-------+
+--> | LSR-1 | --X---> | LSR-2 | --+
| +-------+ Fault +-------+ AIS/LKR
| |
+-------+ --+ +--> +-------+
| LER-A | +-------+ | LER-B |
+-------+ <------RDI----- | LSR-3 | <------RDI----- +-------+
+-------+
Reverse LSP
<------------------
Figure 2: RDI Operation in Associated Bidirectional LSP
Figure 1 depicts an associated bidirectional LSP with:
Forward LSP (LER-A, LSR-1, LSR-2, LER-B)
Reverse LSP (LER-B, LSR-3, LER-A)
Scenario 1, Fault on LER-A: LSR-1 will detect a fault on the server
sub-layer and generate AIS/LKR message on the upstream link for
Forward LSP (towards LSR-2). LSR-2 will process the message and
forward it, unaltered, upstream to LER-B. LER-B will process the
message, set the RDI-Flag and forward it on the associated Reverse
LSP. Because the RDI-Flag is set, LSR-3 does not need to process the
message as the fault is not on the Reverse LSP and forwards it,
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unaltered, towards LER-A. LER-A, if it receives the message (the
fault may only be on the forward LSP on LER-A) processes the message
and discard it (RDI-Flag set received on Reverse LSP indicates the
fault is on the Forward LSP, and vice-versa). When the fault clears,
LSR-1 will issue new set of AIS/LKR messages to clear the previous
fault condition. This message is also propagated using the previous
RDI logic to coordinate fault clear on the Reverse LSP.
Scenario 2, Link fault or LSR fault on Forward LSP: Same logic as
fault on LER-A.
3.2. RDI Operation in Co-routed Bidirectional LSPs
RDI is not a required mechanism in co-routed bidirectional LSPs as
MPLS LSx on either direction of the fault will generate MPLS FM OAM
messages and the fault is propagated to both LERs.
4. IANA Requirements
None.
5. Security Consideration
No additional security impact because of addition of RDI-Flag in MPLS
FM OAM messages.
6. Acknowledgements
7. References
7.1. Normative References
[RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau,
L., and L. Berger, "A Framework for MPLS in Transport
Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010,
<https://www.rfc-editor.org/info/rfc5921>.
[RFC6427] Swallow, G., Ed., Fulignoli, A., Ed., Vigoureux, M., Ed.,
Boutros, S., and D. Ward, "MPLS Fault Management
Operations, Administration, and Maintenance (OAM)",
RFC 6427, DOI 10.17487/RFC6427, November 2011,
<https://www.rfc-editor.org/info/rfc6427>.
7.2. Informative References
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
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Authors' Addresses
Ashesh Mishra
O3b Networks
USA
Email: mishra.ashesh@outlook.com
Mahesh Jethanandani
USA
Email: mjethanandani@gmail.com
Ankur Saxena
Ciena Corporation
3939 North 1st Street
San Jose, CA 95134
USA
Email: ankurpsaxena@gmail.com
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