Network Working Group N. Sprecher
Internet-Draft Nokia Siemens Networks
Intended status: Informational E. Bellagamba
Expires: January 5, 2011 Ericsson
Y. Weingarten
Nokia Siemens Networks
July 4, 2010
MPLS-TP OAM Analysis
draft-ietf-mpls-tp-oam-analysis-02.txt
Abstract
This document analyzes the set of requirements for Operations,
Administration, and Maintenance (OAM) for the Transport Profile of
MPLS(MPLS-TP) as defined in [MPLS-TP OAM Reqs], to evaluate whether
existing OAM tools (either from the current MPLS toolset or from the
ITU-T documents) can be applied to these requirements. Eventually,
the purpose of the document is to map the set of functions to a set
of tools based on the existing OAM toolset.
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Organization of the document . . . . . . . . . . . . . . . 4
1.3. Contributing Authors . . . . . . . . . . . . . . . . . . . 5
1.4. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Basic OAM infrastructure functionality . . . . . . . . . . . . 5
3. MPLS-TP OAM Functions . . . . . . . . . . . . . . . . . . . . 6
3.1. Continuity Check and Connectivity Verification . . . . . . 7
3.1.1. Documents for CC-V tools . . . . . . . . . . . . . . . 7
3.2. Remote Defect Indication . . . . . . . . . . . . . . . . . 7
3.2.1. Documents for RDI . . . . . . . . . . . . . . . . . . 7
3.3. Route Tracing . . . . . . . . . . . . . . . . . . . . . . 7
3.3.1. Documents for Route Tracing . . . . . . . . . . . . . 8
3.4. Alarm Reporting . . . . . . . . . . . . . . . . . . . . . 8
3.4.1. Documents for Alarm Reporting . . . . . . . . . . . . 8
3.5. Lock Reporting . . . . . . . . . . . . . . . . . . . . . . 8
3.5.1. Documents for Lock Reporting . . . . . . . . . . . . . 8
3.6. Diagnostic . . . . . . . . . . . . . . . . . . . . . . . . 8
3.6.1. Documents for Diagnostic Testing . . . . . . . . . . . 9
3.7. Lock Instruct . . . . . . . . . . . . . . . . . . . . . . 9
3.7.1. Documents for Lock Instruct . . . . . . . . . . . . . 9
3.8. Client Failure Indication . . . . . . . . . . . . . . . . 9
3.8.1. Documents for CFI . . . . . . . . . . . . . . . . . . 9
3.9. Packet Loss Measurement . . . . . . . . . . . . . . . . . 9
3.9.1. Documents for Packet Loss Measurement . . . . . . . . 10
3.10. Packet Delay Measurement . . . . . . . . . . . . . . . . . 10
3.10.1. Documents for Delay Measurement . . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
7. Informative References . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
1.1. Scope
OAM (Operations, Administration, and Maintenance) plays a significant
role in carrier networks, providing methods for fault management and
performance monitoring in both the transport and the service layers
in order to improve their ability to support services with guaranteed
and strict Service Level Agreements (SLAs) while reducing their
operational costs.
[MPLS-TP Reqs] in general, and [MPLS-TP OAM Reqs] in particular
define a set of requirements for OAM functionality in MPLS-Transport
Profile (MPLS-TP) for MPLS-TP Segments, Label Switched Paths (LSPs)
(network infrastructure) and Pseudowires (PWs) (services). One of
the mandates of the joint (IETF and ITU-T) MPLS-TP work-item is the
objective of developing a Transport Profile is to base the toolset on
existing MPLS technologies. In addition, [MPLS-TP Reqs] indicates
the need for the OAM toolset for MPLS-TP to be fully interoperable
with existing MPLS OAM tools.
The purpose of this document is to outline the recommendations of the
MPLS-TP design team and confirmed by the working group for the
toolset that should be defined to fulfill the OAM functionality
requirements as documented in [MPLS-TP OAM Reqs] and [MPLS-TP OAM
Frwk]. Based on the principles cited above, it was determined to
base the MPLS-TP OAM toolset on the following existing MPLS tools:
o LSP-Ping as defined in [LSP Ping].
o Bidirectional Forwarding Detection (BFD) as defined in [BASE BFD]
and refined in [MPLS BFD].
o ITU-T OAM for Ethernet toolset as defined in [Y.1731] this will be
used for functionality guidelines for the performance measurement
tools that are not currently supported in MPLS.
It should be noted that certain extensions and adjustments may be
made to the existing MPLS tools, in order to conform to the transport
environment and the requirements of MPLS-TP.
1.2. Organization of the document
Section 2 of the document provides references to the basic OAM tools
that are provided for MPLS-TP OAM.
Section 3 outlines the different tools that are required for MPLS-TP
OAM and references the documents that will define the appropriate
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tools based on the principles outlined above.
1.3. Contributing Authors
Yaakov Stein (Rad), Annamaria Fulignoli (Ericsson), Italo Busi
(Alcatel Lucent), Huub van Helvoort (Huawei)
1.4. Acronyms
This draft uses the following acronyms:
ACH Associated Channel Header
BFD Bidirectional Forwarding Detection
CC-V Continuity Check and Connectivity Verification
G-ACH Generic Associated Channel Header
LSP Label Switched Path
MPLS-TP Transport Profile for MPLS
OAM Operations, Administration, and Maintenance
PW Pseudowire
RDI Remote Defect Indication
SLA Service Level Agreement
TLV Type, Length, Value
VCCV Virtual Circuit Connectivity Verification
2. Basic OAM infrastructure functionality
[MPLS-TP OAM Reqs] defines a set of requirements on OAM architecture
and general principles of operations which are evaluated below:
o [MPLS-TP OAM Reqs] requires that OAM mechanisms in MPLS-TP are
independent of the transmission media and of the client service
being emulated by the PW.
o [MPLS-TP OAM Reqs] requires that the MPLS-TP OAM must be able to
support both an IP based and non-IP based environment. If the
network is IP based, i.e. IP routing and forwarding are
available, then the MPLS-TP OAM toolset should rely on the IP
routing and forwarding capabilities. On the other hand, in
environments where IP functionality is not available, the OAM
tools must still be able to operate without dependence on IP
forwarding and routing.
o [MPLS-TP OAM Reqs] requires that all OAM protocols support
identification information, at least in the form of IP addressing
structure and be extensible to support additional identification
schemes.
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o It is also required that OAM packets and the user traffic are
congruent (i.e. OAM packets are transmitted in-band) and there is
a need to differentiate OAM packets from user-plane ones.
Inherent in this requirement is the principle that MPLS-TP OAM be
independent of any existing control-plane, although it should not
preclude use of the control-plane functionality.
o [MPLS-TP OAM Reqs] requires a single OAM technology and consistent
OAM capabilities for LSPs, PWs, and Sections.
o [MPLS-TP OAM Reqs] requires allowing OAM packets to be directed to
an intermediate point of a LSP/PW.
The following comprise the document-set that addresses the basic
requirements listed above:
o The [MPLS-TP OAM Frwk] document describes the architecural
framework for conformance to the basic requirements listed above.
It also defines the basic relationships between the MPLS
structures, e.g. LSP, PW, and the structures necessary for OAM
functionality, i.e. the Managed Entity Group, its End-points, and
Intermediate Points.
o The [MPLS G-ACH] document specifies the use of the MPLS-TP in-
band control channel. This is modeled after the VCCV channel
described in [PW ACH] and allows transporting the OAM messages
congruently with the data traffic while allowing the required
identification of the packets. It is expected that all of the OAM
protocols will be used in conjunction with this Generic Associated
Channel.
o The [MPLS-TP ACH TLV] document specifies a basic set of TLV fields
that could be used by different OAM messages, in conjunction with
the Generic Associated Channel, to supply the additional parameter
values necessary for the proper functionality.
o The [MPLS TP Idents] document addresses the need of MPLS-TP to
support different addressing spaces. This document describes
different formats for addresses that could be used to identify the
transport entities in the network and referenced by the different
OAM protocols.
3. MPLS-TP OAM Functions
The following sections discuss the required OAM functions that were
identified in [MPLS-TP OAM Reqs] and expanded upon in [MPLS-TP OAM
Frwk].
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3.1. Continuity Check and Connectivity Verification
Continuity Check and Connectivity Verification (CC-V) are OAM
operations generally used in tandem, and compliment each other.
These functions are generally run proactively, but may also be used
on-demand, either due to bandwidth considerations or for diagnoses of
a specific condition. Proactively [MPLS-TP OAM Reqs] states that the
function should allow the MEPs to monitor the liveness and
connectivity of a transport path. In on-demand mode, this function
should support monitoring between the MEPs and, in addition, between
a MEP and MIP.
The [MPLS-TP OAM Frwk] highlights the need for the CC-V messages to
include unique identification of the MEG that is being monitored and
the MEP that originated the message. The function, both proactively
and in on-demand mode, need to be transmitted at regular rates pre-
configured by the operator.
3.1.1. Documents for CC-V tools
[Pro CC-V] defines the BFD extensions that will be used for proactive
CC-V applications. While [Demand CV] provides the LSP-Ping
extensions that will be used to implement on-demand Connectivity
Verification. Both of these tools will be used together with the
basic tools mentioned above in section 2
3.2. Remote Defect Indication
Remote Defect Indication (RDI) is used by a path end-point to report
to its peer end-point that a defect is detected on a bi-directional
connection between them. [MPLS-TP OAM Reqs] points out that this
function may be applied to a unidirectional LSP only if there a
return path exists. [MPLS-TP OAM Frwk] points out that this function
is associated with the proactive CC-V function
3.2.1. Documents for RDI
The [Pro CC-V] document includes and extension for BFD that would
include the RDI indication in the BFD format, and a specification of
how this indication is to be used.
3.3. Route Tracing
[MPLS-TP OAM Reqs] defines that there is a need for functionality
that would allow a path end-point to identify the intermediate and
end-points of the path. This function would be used in on-demand
mode. Normally, this path will be used for bidirectional PW, LSP,
and sections, however, unidirectional paths may be supported only if
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a return path exists.
3.3.1. Documents for Route Tracing
The [Demand CV] document that specifies the LSP-Ping enhancements for
MPLS-TP on-demand Connectivity Verification includes information on
the use of LSP-Ping for route tracing of a MPLS-TP transport path.
3.4. Alarm Reporting
Alarm Reporting is a function used by an intermediate point of a
path, that becomes aware of a fault on the path, to report to the
end-points of the path. [MPLS-TP OAM Frwk] states that this may
occur as a result of a defect condition discovered at a server sub-
layer. This generates an Alarm Indication Signal (AIS) that
continues until the fault is cleared. The consequent action of this
function is detailed in [MPLS-TP OAM Frwk].
3.4.1. Documents for Alarm Reporting
MPLS-TP defines a new protocol to address this functionality that is
documented in [Fault Mng]. This protocol uses all of the basic
mechanisms detailed in Section 2.
3.5. Lock Reporting
Lock reporting, defined in [MPLS-TP OAM Reqs], is similar to the
Alarm Reporting function described above. It is used by an
intermediate point to notify the end points of a transport path that
an administrative lock condition exists for this transport path.
3.5.1. Documents for Lock Reporting
MPLS-TP defines a new protocol to address this functionality that is
documented in [Fault Mng]. This protocol uses all of the basic
mechanisms detailed in Section 2.
3.6. Diagnostic
The [MPLS-TP OAM Reqs] indicates that there is need to provide a OAM
function that would enable conducting different diagnostic tests on a
PW, LSP, or Section. The [MPLS-TP OAM Frwk] provides two types of
specific tests to be used through this functionality:
o Throughput Estimation - allowing the provider to verify the
bandwidth/throughput of a transport path. This is an out-of-
service tool, that uses special packets of varying sizes to test
the actual bandwidth and/or throughput of the path.
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o Data-plane loopback - this out-of-service tool that causes all
traffic that reaches the target node, either a MEP or MIP, to be
looped back to the originating MEP. For targeting MIPs, a
corouted bi-directional path is required.
3.6.1. Documents for Diagnostic Testing
These diagnostic functions are being defined in a merge of existing
separate individual drafts. The merged document will define a new
G-ACH based protocol message that addresses the Throughput Estimation
tool, and also provide various flavors of loopback functionality.
3.7. Lock Instruct
The Lock Instruct function is an administrative control tool that
allows a path end-point to instruct its peer end-point to lock the
path. The tool is necessary to support single-side provisioning for
administartive locking, according to . This function is used on-
demand.
3.7.1. Documents for Lock Instruct
Work is being done on a document that will specify the new ACH based
protocol format for this tool.
3.8. Client Failure Indication
Client Failure Indication (CFI) is defined in [MPLS-TP OAM Reqs] to
allow the propagation information from one edge of the network to the
other. The information concerns a defect to a client, in the case
that the client does not support alarm notification.
3.8.1. Documents for CFI
Work is being done on a document that will specify the new ACH based
protocol format for this tool.
3.9. Packet Loss Measurement
Packet Loss Measurement is required, by [MPLS-TP OAM Reqs] to provide
a quantification of the packet loss ratio on a transport path. This
is the ratio of the number of user packets lost to the total number
of user packets during a defined time interval. To employ this
function, [MPLS-TP OAM Frwk] defines that the two end-points of the
transport path should exchange counters of messages transmitted and
received within a time period bounded by loss-measurement messages.
The framework warns that there may be small errors in the computation
that result from various issues.
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3.9.1. Documents for Packet Loss Measurement
The [Loss-Delay] describes the protocol formats and procedures for
using the tool. The tool logic is based on the behavior of the
parallel function described in [Y.1731].
3.10. Packet Delay Measurement
Packet Delay Measurement is a function that is used to measure one-
way or two-way delay of a packet transmission between a pair of the
end-points of a path (PW, LSP, or Section), as described in [MPLS-TP
OAM Reqs]. Where:
o One-way packet delay is the time elapsed from the start of
transmission of the first bit of the packet by a source node until
the reception of the last bit of that packet by the destination
node.
o Two-way packet delay is the time elapsed from the start of
transmission of the first bit of the packet by a source node until
the reception of the last bit of the loop-backed packet by the
same source node, when the loopback is performed at the packet's
destination node.
[MPLS-TP OAM Frwk] describes how the tool could be performed (both in
proactive and on-demand modes) for either one-way or two-way
measurement. However, it warns that the one-way delay option
requires precise time synchronization between the end-points.
3.10.1. Documents for Delay Measurement
The [Loss-Delay] describes the protocol formats and procedures for
using the tool. The tool logic is based on the behavior of the
parallel function described in [Y.1731].
4. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
5. Security Considerations
This document does not by itself raise any particular security
considerations.
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6. Acknowledgements
The editors wish to thank the MPLS-TP Design Team members, from both
the IETF and ITU-T leadership teams, in formulating the
recommendations documented here. In particular, we would like to
thank Loa Andersson, Huub van Helvoort, and the Area Directors for
their suggestions and enhancements to the text.
7. Informative References
[LSP Ping]
Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[PW ACH] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, February 2006.
[BASE BFD]
Katz, D. and D. Ward, "Bidirectional Forwarding
Detection", RFC 5880, February 2009.
[MPLS BFD]
Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"BFD For MPLS LSPs", RFC 5884, June 2008.
[MPLS TP Idents]
Bocci, M. and G. Swallow, "MPLS-TP Identifiers",
ID draft-ietf-mpls-tp-identifiers-01.txt, March 2010.
[Pro CC-V]
Allan, D. and G. Swallow, "Proactive Connection
Verification, Continuity Check and Remote Defect
indication for MPLS Transport Profile",
ID draft-ietf-mpls-tp-cc-cv-rdi-00.txt, June 2010.
[Demand CV]
Bahadur, N., Aggarwal, R., Boutros, S., and E. Gray, "MPLS
on-demand Connectivity Verification, Route Tracing and
Adjacency Verification",
ID draft-ietf-mpls-tp-on-demand-cv-00, June 2010.
[MPLS-TP OAM Reqs]
Vigoureux, M., Betts, M., and D. Ward, "Requirements for
OAM in MPLS Transport Networks",
ID draft-ietf-mpls-tp-oam-requirements-05, April 2009.
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[MPLS-TP OAM Frwk]
Busi, I., Niven-Jenkins, B., and D. Allan, "MPLS-TP OAM
Framework and Overview",
ID draft-ietf-mpls-tp-oam-framework-07, July 2010.
[MPLS-TP Reqs]
Niven-Jenkins, B., Nadeau, T., and C. Pignataro,
"Requirements for the Trasport Profile of MPLS",
ID draft-ietf-mpls-tp-requirements-06, April 2009.
[MPLS G-ACH]
Bocci, M., Bryant, S., and M. Vigoureux, "MPLS Generic
Associated Channel", RFC 5586, June 2009.
[MPLS-TP ACH TLV]
Boutros, S., Bryant, S., Sivabalan, S., Swallow, G., and
D. Ward, "Definition of ACH TLV Structure",
ID draft-ietf-mpls-tp-ach-tlv-00, June 2009.
[Fault Mng]
Swallow, G., Fulignoli, A., and M. Vigoureux, "MPLS Fault
Management OAM", ID draft-ietf-mpls-tp-fault-00,
March 2010.
[Loss-Delay]
Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for the MPLS Transport Profile",
ID draft-frost-mpls-tp-loss-delay-00, April 2010.
[Y.1731] International Telecommunications Union - Standardization,
"OAM functions and mechanisms for Ethernet based
networks", ITU Y.1731, May 2006.
Authors' Addresses
Nurit Sprecher
Nokia Siemens Networks
3 Hanagar St. Neve Ne'eman B
Hod Hasharon, 45241
Israel
Email: nurit.sprecher@nsn.com
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Elisa Bellagamba
Ericsson
6 Farogatan St
Stockholm, 164 40
Sweden
Phone: +46 761440785
Email: elisa.bellagamba@ericsson.com
Yaacov Weingarten
Nokia Siemens Networks
3 Hanagar St. Neve Ne'eman B
Hod Hasharon, 45241
Israel
Phone: +972-9-775 1827
Email: yaacov.weingarten@nsn.com
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