Internet DRAFT - draft-boutros-mpls-tp-cv-cc
draft-boutros-mpls-tp-cv-cc
Network Working Group Sami Boutros (Ed.)
Internet Draft Siva Sivabalan (Ed.)
Intended status: Standards Track George Swallow (Ed.)
Expires: February 2010
Cisco Systems, Inc.
Martin Vigoureux (Ed.)
Alcatel-Lucent
A. Fulignoli (Ed.)
Ericsson
July 6, 2009
Connection Verification and Continuity Check for MPLS Transport
Profile Label Switched Path
draft-boutros-mpls-tp-cv-cc-00.txt
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Abstract
Connection Verification (CV) and Continuity Check (CC) are
important Operations, Administration, and Management (OAM)functions
of MPLS Transport Profile (MPLS-TP). This document specifies
methods for CV and CC for MPLS-TP Label Switched Path (LSP) using
Bidirectional Forwarding Detection (BFD).
Table of Contents
1. Introduction...................................................2
2. Terminology....................................................3
3. MPLS-TP Connection Verification and Continuity Check Mechanism.3
3.1. MPLS-TP CV/CC Message format..............................4
3.2. BFD Profile for MPLS-TP...................................5
4. Operation......................................................6
5. Security Considerations........................................7
6. IANA Considerations............................................7
7. References.....................................................7
7.1. Normative References......................................7
7.2. Informative References....................................7
Author's Addresses................................................8
Full Copyright Statement..........................................9
Intellectual Property Statement...................................9
1. Introduction
In traditional transport networks, circuits are provisioned on
multiple switches. Service Providers (SP) need OAM tools to detect
mis-connectivity and loss of continuity of transport circuits. MPLS-
TP LSPs [6] emulating traditional transport circuits need to provide
the same CC and CV capabilities as mentioned in [2]. This document
describes the use of BFD [3] for CV and CC of an MPLS-TP LSP between
2 Maintenance End Points (MEPs). The mechanism specified in this
document is restricted only to BFD asynchronous mode. The proposed
method uses BFD state machine defined in Section 6.2 of [3].
Moreover, this document recommends the use of BFD for the Pseudowire
Virtual Circuit Connectivity Verification (VCCV)as defined in [5].
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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document are to be interpreted as described in RFC-2119 [1].
2. Terminology
ACH: Associated Channel Header
BFD: Bidirectional Forwarding Detection
CV: Connection Verification
EOS: End of Stack
GAL: Generalized Alert Label
LSR: Label Switching Router
MEP: Maintenance End Point
MIP: Maintenance Intermediate Point
MPLS-OAM: MPLS Operations, Administration and Maintenance
MPLS-TP: MPLS Transport Profile
MPLS-TP LSP: Bidirectional Label Switch Path representing a circuit
MS-PW: Mult-Segment PseudoWire
NMS: Network Management System
PW: PseudoWire
RR: Record Route
TLV: Type Length Value
TTL: Time To Live
RDI: Remote defect indication.
3. MPLS-TP Connection Verification and Continuity Check Mechanism
The proposed mechanism is based on a new code point in the Generic
Associated Channel Header (G-ACH) described in [8]. Under MPLS label
stack of the MPLS-TP LSP, the ACH with "MPLS-TP Connection
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Verification/Continuity Check (CV/CC)" code point indicates that the
message is an MPLS-TP CV/CC message.
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| Flags | 0xHH MPLS-TP CV/CC Code Point |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: ACH Indication of MPLS-TP Connection Verification
The first nibble (0001b) indicates the ACH.
The version and the reserved values are both set to 0 as specified in
[8].
MPLS-TP CV/CC code point = 0xHH. [HH to be assigned by IANA from the
PW Associated Channel Type registry.]
3.1. MPLS-TP CV/CC Message format
The format of an MPLS-TP CV/CC Message format is shown below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Label (EOS) | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACH |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
| |
~ Destination and Source Node-IDs of the MPLS-TP LSP ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ BFD Control Packet ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: MPLS-TP CV/CC Message
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As shown in Figure 2, BFD Control packet as defined in [3] is
transmitted as MPLS labeled packets along with GAL, G-ACH, and TLVs
carrying the Destination and Source Node-IDs of the MPLS-TP LSP as
defined in a new IETF draft to be published soon.
The TTL field of the GAL MUST be set to at least 1, and the GAL will
be the end of stack label.
The discriminator values in the BFD control packet will be set to the
LIH (Logical Interface Handle) at each side of the MPLS-TP LSP.
Combination of the Source/Destination Node-IDs and discriminator
value (from the BFD packet) represents MEP-ID, i.e., the combination
of the source node address and my discriminator is the Source MEP-ID,
and the combination of the destination node address and your
discriminator is the peer MEP-ID. Note that the format of Node ID is
defined in [7].
In this mode of operation, the IP/UDP headers for the BFD control
packets are omitted from the BFD encapsulation.
Furthermore, BFD is used not only for fault detection but also for
mis-insertion and for Remote Defect Indication (RDI). Reception of a
BFD control packet having an unexpected source Node-ID, destination
Node-ID or discriminator(s) is considered a BFD mis-insertion fault.
Reception of BFD control packet with a diagnostic code of 1 (Control
Detection Time Expired) or 5 (Path down) is considered an RDI fault.
3.2. BFD Profile for MPLS-TP
BFD MUST run in asynchronous mode as described in [3].
In all BFD control packets sent, both "Desired Min TX Interval" and
"Required Min RX Interval" MUST be set to the operator configured
values for BFD transmission period for the MPLS-TP LSP. If the
received BFD packets have different "Desired Min TX Interval field"
than the one used for the transmitted packets, the BFD session MUST
NOT come up by default, except if the behavior is overridden by an
operator using explicit configuration.
By default the transmission rates MUST be the same at both end of the
MPLS-TP LSP (both working and protecting).
The "my discriminator" field in the BFD control packets is set to the
MPLS-TP LSP's local LIH (Logical Interface Handle) and the "your
discriminator" field is initially set to zero. During BFD session
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negotiation, the "my discriminator" field in the received BFD packets
MUST match the remote discriminator.
4. Operation
Single-hop BFD initialization procedures described in [4] are
followed. As mentioned before, only asynchronous mode is supported.
The operation of BFD over MPLS-TP LSP is symmetrical. Both endpoints
of the bidirectional MPLS-TP LSP MUST send BFD messages inband in the
MPLS-TP LSP using the defined code point.
Both MEPs at the end of an MPLS-TP LSP need to bootstrap the BFD
session and start sending BFD control packets encapsulated within
MPLS-TP CV/CC message described in this document. MPLS-TP LSP labels
at both ends of the MPLS-TP LSP will be used as the de-multiplexer
for the received BFD packets, and no discriminator values will be
used.
A single BFD session per MPLS-TP LSP will exist between the MEP's of
the MPLS-TP LSP. Both MEP's will be sending initial BFD Control
packets with a "Your Discriminator" field of zero, and BFD Control
packets received with a "Your Discriminator" field of zero are
associated to the BFD session bound to the MPLS-TP LSP.
Both "Desired Min TX Interval" and "Required Min RX Interval" MUST be
set to the configured BFD transmission period for the MPLS-TP LSP.
Assume an MPLS-TP LSP that spans across LSR-A, LSR-B and LSR-C. LSR-A
LSR-C act as the MEPs whereas LSR-B act as a MIP for the MPLS-TP LSP.
Furthermore, assume that on both LSR-A and LSR-C the operator
provision the BFD detection time multiplier as per [3].
If LSR-A receives a BFD control message that has a destination node
identifier different from it's identifier, or has an unexpected
source node identifier, or non-zero your discriminator value or has a
my discriminator value different from what LSR-A is expecting, LSR-A
declares that the MPLS-TP LSP is down in its receive direction. In
this case, LSR-A signals LSR-C that the BFD session is down using the
State (Sta) with diagnostic code 5 (Path down).
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If LSR-A stops receiving BFD control messages from LSR-C for a period
of detection time multiplier (calculation of Detection Time is
defined in[3]), LSR-A declares that the MPLS-TP LSP is down in its
receive direction, and signals this to the remote end via the State
(Sta) with Diagnostic code 1(Control Detection Time Expired). In
turn, LSR-C declares the MPLS-TP LSP is down in its transmit
direction setting the State to Down with Diagnostic code 3 (Neighbor
signaled session down) in its control messages to LSR-A.
5. Security Considerations
The security considerations for the authentication TLV need further
study.
6. IANA Considerations
To be added.
7. References
7.1. Normative References
[1] Bradner. S, "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March, 1997.
[2] Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM in
MPLS Transport Networks", draft-ietf-mpls-tp-oam-requirements-
02 (work in progress), June 2009.
[3] Katz, D., and D. Ward, "Bidirectional Forwarding Detection",
draft-ietf-bfd-base-09 (work in progress), August 2009.
[4] Katz, D., and D. Ward, "Generic Application of BFD", draft-
ietf-bfd-generic-05 (work in progress), February 2009.
[5] T. Nadeau, et. Al, Bidirectional Forwarding Detection (BFD) for
the Pseudowire Virtual Circuit Connectivity Verification
(VCCV), draft-ietf-pwe3-vccv-bfd-05, June 2009.
7.2. Informative References
[6] M. Bocci, et. al., "A Framework for MPLS in Transport
Networks", draft-ietf-mpls-tp-framework-01.txt, Work in
Progress, June 2009.
[7] S. Boutros, et. al., "Definition of ACH TLV Structure", draft-
bryant-mpls-tp-ach-tlv-01.txt, Work in Progress, May 2009.
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[8] M. Bocci, et. al., "MPLS Generic Associated Channel", RFC 5586,
June, 2009.
Author's Addresses
Sami Boutros
Cisco Systems, Inc.
3750 Cisco Way
San Jose, California 95134
USA
Email: sboutros@cisco.com
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario, K2K 3E8
Canada
Email: msiva@cisco.com
George Swallow
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough , MASSACHUSETTS 01719
United States
Email: swallow@cisco.com
David Ward
Cisco Systems, Inc.
3750 Cisco Way
San Jose, California 95134
USA
Email: wardd@cisco.com
Stewart Bryant
Cisco Systems, Inc.
250, Longwater, Green Park,
Reading RG2 6GB, UK
UK
Email: stbryant@cisco.com
Martin Vigoureux
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Alcatel-Lucent
Email: martin.vigoureux@alcatel-lucent.com
Annamaria Fulignoli (Editor)
Ericsson
Email: annamaria.fulignoli@ericsson.com
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