Operations and Management Area Working Group T. Mizrahi
Internet Draft Marvell
Intended status: Informational N. Sprecher
Expires: September 2012 Nokia Siemens Networks
E. Bellagamba
Ericsson
Y. Weingarten
Nokia Siemens Networks
March 12, 2012
An Overview of
Operations, Administration, and Maintenance (OAM) Mechanisms
draft-ietf-opsawg-oam-overview-06.txt
Abstract
Operations, Administration, and Maintenance (OAM) is a general term
that refers to a toolset that can be used for fault detection and
isolation, and for performance measurement. OAM mechanisms have been
defined for various layers in the protocol stack, and are used with a
variety of protocols.
This document presents an overview of the OAM mechanisms that have
been defined and are currently being defined by the IETF.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on September 12, 2012.
Mizrahi, et al. Expires September 12, 2012 [Page 1]
Internet-Draft Overview of OAM Mechanisms March 2012
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ................................................. 3
1.1. Background .............................................. 3
1.2. The OAM toolsets ........................................ 4
1.3. IETF OAM Standards ...................................... 5
1.4. Non-IETF OAM Standards .................................. 8
2. Basic Terminology ............................................ 9
2.1. Abbreviations ........................................... 9
2.2. Terminology used in OAM Standards ...................... 10
2.2.1. General Terms ..................................... 10
2.2.2. OAM Maintenance Entities .......................... 11
2.2.3. OAM Maintenance Points ............................ 11
2.2.4. Proactive and On-demand activation ................ 12
2.2.5. Connectivity Verification and Continuity Checks ... 12
2.2.6. Failures .......................................... 13
3. OAM Tools ................................................... 13
3.1. ICMP Ping .............................................. 13
3.2. Traceroute ............................................. 13
3.3. Bidirectional Forwarding Detection (BFD) ............... 14
3.3.1. Overview .......................................... 14
3.3.2. BFD Control ....................................... 14
3.3.3. BFD Echo .......................................... 15
3.4. LSP Ping ............................................... 15
3.5. PWE3 Virtual Circuit Connectivity Verification (VCCV) .. 16
3.6. IP Performance Metrics (IPPM) .......................... 17
3.6.1. Overview .......................................... 17
3.6.2. Control and Test Protocols ........................ 17
3.6.3. OWAMP ............................................. 18
3.6.4. TWAMP ............................................. 18
3.7. MPLS-TP OAM ............................................ 19
Mizrahi, et al. Expires September 12, 2012 [Page 2]
Internet-Draft Overview of OAM Mechanisms March 2012
3.7.1. Overview .......................................... 19
3.7.2. Generic Associated Channel ........................ 19
3.7.3. MPLS-TP OAM Toolset ............................... 20
3.7.3.1. Continuity Check and Connectivity Verification 20
3.7.3.2. Route Tracing ................................ 21
3.7.3.3. Lock Instruct ................................ 21
3.7.3.4. Lock Reporting ............................... 21
3.7.3.5. Alarm Reporting .............................. 21
3.7.3.6. Remote Defect Indication ..................... 22
3.7.3.7. Client Failure Indication .................... 22
3.7.3.8. Packet Loss Measurement ...................... 22
3.7.3.9. Packet Delay Measurement ..................... 22
3.8. Summary of OAM Functions ............................... 23
4. Security Considerations ..................................... 24
5. IANA Considerations ......................................... 24
6. Acknowledgments ............................................. 24
7. References .................................................. 24
7.1. Normative References ................................... 24
7.2. Informative References ................................. 27
1. Introduction
OAM is a general term that refers to a toolset that can be used for
detecting, isolating and reporting connection failures or measurement
of connection performance parameters. The term OAM has been used over
the years in several different contexts, as discussed in [OAM Def].
This term as been associated with the 3 logical abstraction layers:
the forwarding plane, the control plane, and the management plane. In
the context of this document OAM refers to Operations,
Administration, and Maintenance. Hence, management aspects are
outside the scope of this document.
1.1. Background
The communication of a network may be configured and maintained by
use of various tools at different layers - these include use of a
control plane or management plane to configure and maintain the
connectivity of the network from the outside - looking in - and
controlling the connections when the need arises. OAM, on the other
hand, traditionally has been used to maintain the connectivity in-
band with the actual data traffic, i.e. in the data plane.
While the OAM tools may, and quite often do, work in conjunction with
a control-plane or management plane, they are usually defined to be
independent of the control-plane. The OAM tools communicate with the
management plane to raise alarms, and often the on-demand tools may
be activated by the management, e.g. to locate and localize problems.
Mizrahi, et al. Expires September 12, 2012 [Page 3]
Internet-Draft Overview of OAM Mechanisms March 2012
The considerations of the control-plane maintenance tools or the
functionality of the management-plane are out of scope for this
document, which will concentrate on presenting the data-plane tools
that are used for OAM.
1.2. The OAM toolsets
This memo provides an overview of the different sets of OAM
mechanisms defined by the IETF. It is intended for those with little
or no familiarity with the described mechanisms. The set of OAM
mechanisms described in this memo are applicable to IP unicast, MPLS,
pseudowires, and MPLS for the transport environment (MPLS-TP). While
OAM mechanisms that are applicable to other technologies exist, they
are beyond the scope of this memo. This document focuses on IETF
documents that have been published as RFCs, while other ongoing OAM-
related work is outside the scope.
The IETF has defined OAM protocols and mechanisms in several
different fronts:
o ICMP Ping:
ICMP Echo request, also known as Ping, as defined in [ICMPv4], and
[ICMPv6]. ICMP Ping is a very simple and basic mechanism in
failure diagnosis. LSP Ping is to some extent based on ICMP Ping.
o IPPM:
IP Performance Metrics (IPPM) is a working group in the IETF that
defined common metrics for performance measurement, as well as a
protocol for measuring delay and packet loss in IP networks.
o MPLS:
MPLS LSP Ping, as defined in [MPLS OAM], [MPLS OAM FW] and [LSP
Ping], is an OAM mechanism for point to point MPLS LSPs.
o MPLS-TP:
The OAM requirements for MPLS Transport Profile (MPLS-TP) are
defined in [MPLS-TP OAM], and the toolset is described in [TP OAM
FW].
o BFD:
Bidirectional Forwarding Detection (BFD) is defined in [BFD] as a
framework for a lightweight generic OAM mechanism. The intention
is to define a base mechanism that can be used with various
encapsulation types, network environments, and in various medium
types.
Mizrahi, et al. Expires September 12, 2012 [Page 4]
Internet-Draft Overview of OAM Mechanisms March 2012
This document summarizes the OAM mechanisms defined by the IETF. We
first present a comparison of the terminology used in various OAM
standards, and then summarize the OAM functions that each OAM
standard provides.
1.3. IETF OAM Standards
Table 1 summarizes the IETF OAM standards discussed in this document.
The table includes a "Type" column, specifying the nature of each of
the listed documents:
o Tool: documents that define an OAM tool or mechanism.
o Prof.: documents that define a profile or a variant for an OAM
tool that is defined in other documents.
o Inf.: documents that define an infrastructure that is used by OAM
tools.
o Misc.: other OAM related documents, e.g., OAM requirement and
framework documents.
+-----------+--------------------------------------+-----+----------+
| | Title |Type | RFC |
+-----------+--------------------------------------+-----+----------+
|ICMPv4 Ping| Internet Control Message Protocol |Tool | RFC 792 |
| | | | |
+-----------+--------------------------------------+-----+----------+
|ICMPv6 Ping| Internet Control Message Protocol |Tool | RFC 4443 |
| | (ICMPv6) for the Internet Protocol | | |
| | Version 6 (IPv6) Specification | | |
+-----------+--------------------------------------+-----+----------+
|Traceroute | A Primer On Internet and TCP/IP |Tool | RFC 2151 |
| | Tools and Utilities | | |
+-----------+--------------------------------------+-----+----------+
|BFD | Bidirectional Forwarding Detection |Tool | RFC 5880 |
| +--------------------------------------+-----+----------+
| | Bidirectional Forwarding Detection |Prof.| RFC 5881 |
| | (BFD) for IPv4 and IPv6 (Single Hop) | | |
| +--------------------------------------+-----+----------+
| | Generic Application of Bidirectional |Misc.| RFC 5882 |
| | Forwarding Detection | | |
| +--------------------------------------+-----+----------+
Mizrahi, et al. Expires September 12, 2012 [Page 5]
Internet-Draft Overview of OAM Mechanisms March 2012
| | Bidirectional Forwarding Detection |Prof.| RFC 5883 |
| | (BFD) for Multihop Paths | | |
| +--------------------------------------+-----+----------+
| | Bidirectional Forwarding Detection |Prof.| RFC 5884 |
| | for MPLS Label Switched Paths (LSPs) | | |
| +--------------------------------------+-----+----------+
| | Bidirectional Forwarding Detection |Prof.| RFC 5885 |
| | for the Pseudowire Virtual Circuit | | |
| | Connectivity Verification (VCCV) | | |
+-----------+--------------------------------------+-----+----------+
|IETF MPLS | Operations and Management (OAM) |Misc.| RFC 4377 |
|OAM | Requirements for Multi-Protocol Label| | |
|(LSP Ping) | Switched (MPLS) Networks | | |
| +--------------------------------------+-----+----------+
| | A Framework for Multi-Protocol |Misc.| RFC 4378 |
| | Label Switching (MPLS) Operations | | |
| | and Management (OAM) | | |
| +--------------------------------------+-----+----------+
| | Detecting Multi-Protocol Label |Tool | RFC 4379 |
| | Switched (MPLS) Data Plane Failures | | |
| +--------------------------------------+-----+----------+
| | Operations and Management (OAM) |Misc.| RFC 4687 |
| | Requirements for Point-to-Multipoint | | |
| | MPLS Networks | | |
| +--------------------------------------+-----+----------+
| | ICMP Extensions for Multiprotocol |Tool | RFC 4950 |
| | Label Switching | | |
+-----------+--------------------------------------+-----+----------+
|MPLS-TP | Requirements for OAM in MPLS-TP |Misc.| RFC 5860 |
|OAM +--------------------------------------+-----+----------+
| | MPLS Generic Associated Channel |Inf. | RFC 5586 |
| +--------------------------------------+-----+----------+
| | MPLS-TP OAM Framework |Misc.| RFC 6371 |
| +--------------------------------------+-----+----------+
| | Proactive Connectivity Verification, |Tool | RFC 6428 |
| | Continuity Check, and Remote Defect | | |
| | Indication for the MPLS Transport | | |
| | Profile | | |
| +--------------------------------------+-----+----------+
| | MPLS On-Demand Connectivity |Tool | RFC 6426 |
| | Verification and Route Tracing | | |
Mizrahi, et al. Expires September 12, 2012 [Page 6]
Internet-Draft Overview of OAM Mechanisms March 2012
| +--------------------------------------+-----+----------+
| | MPLS Fault Management Operations, |Tool | RFC 6427 |
| | Administration, and Maintenance (OAM)| | |
| +--------------------------------------+-----+----------+
| | MPLS Transport Profile Lock Instruct |Tool | RFC 6435 |
| | and Loopback Functions | | |
| +--------------------------------------+-----+----------+
| | Packet Loss and Delay Measurement for|Tool | RFC 6374 |
| | MPLS Networks | | |
| +--------------------------------------+-----+----------+
| | A Packet Loss and Delay Measurement |Prof.| RFC 6375 |
| | Profile for MPLS-Based Transport | | |
| | Networks | | |
+-----------+--------------------------------------+-----+----------+
|PW VCCV | Pseudowire Virtual Circuit |Inf. | RFC 5085 |
| | Connectivity Verification (VCCV): | | |
| | A Control Channel for Pseudowires | | |
+-----------+--------------------------------------+-----+----------+
|IPPM | Framework for IP Performance Metrics |Misc.| RFC 2330 |
| +--------------------------------------+-----+----------+
| | IPPM Metrics for Measuring |Misc.| RFC 2678 |
| | Connectivity | | |
| +--------------------------------------+-----+----------+
| | A One-way Delay Metric for IPPM |Misc.| RFC 2679 |
| +--------------------------------------+-----+----------+
| | A One-way Packet Loss Metric for IPPM|Misc.| RFC 2680 |
| +--------------------------------------+-----+----------+
| | A Round-trip Delay Metric for IPPM |Misc.| RFC 2681 |
| +--------------------------------------+-----+----------+
| | A One-way Active Measurement Protocol|Tool | RFC 4656 |
| | (OWAMP) | | |
| +--------------------------------------+-----+----------+
| | A Two-Way Active Measurement Protocol|Tool | RFC 5357 |
| | (TWAMP) | | |
+-----------+--------------------------------------+-----+----------+
Table 1 Summary of IETF OAM Related Standards
Mizrahi, et al. Expires September 12, 2012 [Page 7]
Internet-Draft Overview of OAM Mechanisms March 2012
1.4. Non-IETF OAM Standards
In addition to the OAM mechanisms defined by the IETF, the IEEE and
ITU-T have also defined various OAM mechanisms that focus on
Ethernet, and various other transport network environments. These
various mechanisms, defined by the three standard organizations, are
often tightly coupled, and have had a mutual effect on each other.
The ITU-T and IETF have both defined OAM mechanisms for MPLS LSPs,
[ITU-T Y.1711] and [LSP Ping]. The following OAM standards by the
IEEE and ITU-T are to some extent linked to IETF OAM mechanisms
listed above and are mentioned here only as reference material:
o OAM mechanisms for Ethernet based networks have been defined by
both the ITU-T in [ITU-T Y.1731], and by the IEEE in [IEEE
802.1ag]. The IEEE 802.3 standard defines OAM for one-hop Ethernet
links [IEEE 802.3ah].
o The ITU-T has defined OAM for MPLS LSPs in [ITU-T Y.1711].
Table 2 summarizes the OAM standards mentioned in this document. This
document focuses on IETF OAM standards, but these non-IETF standards
are referenced where relevant.
+-----------+--------------------------------------+---------------+
| | Title |Standard/Draft |
+-----------+--------------------------------------+---------------+
|ITU-T | Operation & Maintenance mechanism |[ITU-T Y.1711] |
|MPLS OAM | for MPLS networks | |
| +--------------------------------------+---------------+
| | Assignment of the 'OAM Alert Label' | RFC 3429 |
| | for Multiprotocol Label Switching | |
| | Architecture (MPLS) Operation and | |
| | Maintenance (OAM) Functions | |
| | | |
| | Note: although this is an IETF | |
| | document, it is listed as one of the| |
| | non-IETF OAM standards, since it | |
| | was defined as a complementary part | |
| | of Y.1711. | |
+-----------+--------------------------------------+---------------+
|ITU-T | OAM Functions and Mechanisms for |[ITU-T Y.1731] |
|Ethernet | Ethernet-based Networks | |
|OAM | | |
+-----------+--------------------------------------+---------------+
Mizrahi, et al. Expires September 12, 2012 [Page 8]
Internet-Draft Overview of OAM Mechanisms March 2012
|IEEE | Connectivity Fault Management |[IEEE 802.1ag] |
|CFM | | |
+-----------+--------------------------------------+---------------+
|IEEE | Media Access Control Parameters, |[IEEE 802.3ah] |
|802.3 | Physical Layers, and Management | |
|link level | Parameters for Subscriber Access | |
|OAM | Networks | |
+-----------+--------------------------------------+---------------+
Table 2 Non-IETF OAM Standards Mentioned in this Document
2. Basic Terminology
2.1. Abbreviations
ACH Associated Channel Header
AIS Alarm Indication Signal
BFD Bidirectional Forwarding Detection
CC Continuity Check
CCM Continuity Check Message
CV Connectivity Verification
DM Delay Measurement
FEC Forwarding Equivalence Class
GAL Generic Associated Label
ICMP Internet Control Message Protocol
L2TP Layer Two Tunneling Protocol
LCCE L2TP Control Connection Endpoint
LDP Label Distribution Protocol
LM Loss Measurement
LOC Loss Of Continuity
Mizrahi, et al. Expires September 12, 2012 [Page 9]
Internet-Draft Overview of OAM Mechanisms March 2012
LSP Label Switched Path
LSR Label Switching Router
ME Maintenance Entity
MEG Maintenance Entity Group
MEP MEG End Point
MIP MEG Intermediate Point
MP Maintenance Point
MPLS Multiprotocol Label Switching
MPLS-TP MPLS Transport Profile
MTU Maximum Transmission Unit
OAM Operations, Administration, and Maintenance
PE Provider Edge
PW Pseudowire
PWE3 Pseudowire Emulation Edge-to-Edge
RDI Remote Defect Indication
TTL Time To Live
VCCV Virtual Circuit Connectivity Verification
2.2. Terminology used in OAM Standards
2.2.1. General Terms
A wide variety of terms is used in various OAM standards. Each of the
OAM standards listed in the reference section includes a section that
defines terms relevant to that tool. A thesaurus of terminology for
MPLS-TP terms is presented in [MPLS-TP Term], and provides a good
summary of some of the OAM related terminology.
This section presents a comparison of the terms used in various OAM
standards, without fully quoting the definition of each term. For a
Mizrahi, et al. Expires September 12, 2012 [Page 10]
Internet-Draft Overview of OAM Mechanisms March 2012
formal definition of each term, refer to the references at the end of
this document.
2.2.2. OAM Maintenance Entities
OAM tools are designed to monitor and manage a Maintenance Entity
(ME). An ME, as defined in [TP OAM FW], defines a relationship
between two points of a transport path to which maintenance and
monitoring operations apply.
The following related terms are also quoted from [TP OAM FW]:
o MEP: The two points that define a maintenance entity.
o MEG: The collection of one or more MEs that belongs to the same
transport path and that are maintained and monitored as a group
are known as a Maintenance Entity Group (MEG).
o MIP: In between MEPs, there are zero or more intermediate points,
called Maintenance Entity Group Intermediate Points (MIPs).
A pair of MEPs engaged in an ME are connected by a communication
link, which may be one of several types of connection, e.g. a single
physical connection, a set of physical connections, or a virtual link
such as an MPLS LSP.
The term Maintenance Entity (ME) is used in ITU-T Recommendations
(e.g. [ITU-T Y.1731]), as well as in the MPLS-TP terminology ([TP OAM
FW]). Various terms are used to refer to an ME. For example, BFD does
not explicitly use a term that is equivalent to ME, but rather uses
the term "session", referring to the relationship between two nodes
using a BFD protocol. The MPLS LSP Ping ([LSP Ping]) terminology
simply uses the term "LSP" in this context.
MPLS-TP has defined the terms ME and Maintenance Entity Group (MEG)
in [TP OAM FW], similar to the terms defined by ITU-T. A MEG allows
the monitoring of a compound set of MEs, for example when monitoring
a p2mp MEG that is considered to be the set of MEs between the root
and each individual destination MEP.
2.2.3. OAM Maintenance Points
A Maintenance Point (MP) is a functional entity that is defined at a
node in the network, and either initiates or reacts to OAM messages.
A Maintenance End Point (MEP) is one of the end points of an ME, and
can initiate OAM messages and respond to them. A Maintenance
Intermediate Point (MIP) is an intermediate point between two MEPs,
Mizrahi, et al. Expires September 12, 2012 [Page 11]
Internet-Draft Overview of OAM Mechanisms March 2012
that does not generally initiate OAM frames (one exception to this is
the use of AIS notifications), but is able to respond to OAM frames
that are destined to it. A MIP in MPLS-TP identifies OAM packets
destined to it by the value of the TTL field in the OAM packet. The
term Maintenance Point is a general term for MEPs and MIPs.
The 802.1ag defines a finer distinction between Up MPs and Down MPs.
An MP is a bridge interface, that is monitored by an OAM protocol
either in the direction facing the network, or in the direction
facing the bridge. A Down MP is an MP that receives OAM packets from,
and transmits them to the direction of the network. An Up MP receives
OAM packets from, and transmits them to the direction of the bridging
entity.
MPLS-TP ([TP OAM FW]) uses a similar distinction on the placement of
the MP - either at the ingress, egress, or forwarding function of the
node (Down / Up MPs). This placement is important for localization
of a connection failure.
2.2.4. Proactive and On-demand activation
The different OAM tools may be used in one of two basic types of
activation:
Proactive activation - indicates that the tool is activated on
a continual basis periodically, where messages are sent between
the two MEPs, and errors are detected when a certain number of
expected messages are not received.
On-demand activation - indicates that the tool is activated
"manually" to detect a specific anomaly. In this activation a
small number of OAM messages are sent by a MEP and the reply
message is received.
2.2.5. Connectivity Verification and Continuity Checks
Two distinct classes of failure management functions are used in OAM
protocols, connectivity verification and continuity checks. The
distinction between these terms is defined in [MPLS-TP OAM], and is
used similarly in this document.
Continuity checks are used to verify the liveness of a connection or
a path between two MPs, and are typically sent proactively, though
they can be invoked on-demand as well.
A connectivity verification function allows an MP to check whether it
is connected to a peer MP or not. This function also allows the MP to
Mizrahi, et al. Expires September 12, 2012 [Page 12]
Internet-Draft Overview of OAM Mechanisms March 2012
verify that messages from the peer MP are received through the
correct path, thereby verifying not only that the two MPs are
connected, but also that they are connected through the expected
path. This allows detection of unexpected topology changes. A
connectivity verification (CV) protocol typically uses a CV message,
followed by a CV reply that is sent back to the originator. A CV
function can be applied proactively or on-demand.
Connectivity verification and continuity checks are considered
complementary mechanisms, and are often used in conjunction with each
other.
2.2.6. Failures
The terms Failure, Fault, and Defect are used interchangeably in the
standards, referring to a malfunction that can be detected by a
connectivity or a continuity check. In some standards, such as [IEEE
802.1ag], there is no distinction between these terms, while in other
standards each of these terms refers to a different type of
malfunction.
The terminology used in IETF MPLS-TP OAM takes after the ITU-T, which
distinguishes between these terms in [ITU-T G.806]; The term Fault
refers to an inability to perform a required action, e.g., an
unsuccessful attempt to deliver a packet. The term Defect refers to
an interruption in the normal operation, such as a consecutive period
of time where no packets are delivered successfully. The term Failure
refers to the termination of the required function. While a Defect
typically refers to a limited period of time, a failure refers to a
long period of time.
3. OAM Tools
3.1. ICMP Ping
ICMP provides a connectivity verification function for the Internet
Protocol. The originator transmits an ICMP Echo request packet, and
the receiver replies with an echo reply. ICMP ping is defined in two
variants, [ICMPv4] is used for IPv4, and [ICMPv6] is used for IPv6.
3.2. Traceroute
Traceroute ([TCPIP Tools]) is an application that allows users to
discover the path between an IP source and an IP destination.
Traceroute sends a sequence of UDP packets to UDP port 33434 at the
destination. By default, Traceroute begins by sending three packets,
each with an IP Time-To-Live (TTL) value of one to the destination.
Mizrahi, et al. Expires September 12, 2012 [Page 13]
Internet-Draft Overview of OAM Mechanisms March 2012
These packets expire as soon as they reach the first router in the
path. That router responds by sending three ICMP Time Exceeded
Messages to the Traceroute application. Traceroute now sends another
three UDP packets, each with the TTL value of 2. These messages cause
the second router to return ICMP messages. This process continues,
with ever increasing values for the TTL field, until the packets
actually reach the destination. Because no application listens to
port 33434 at the destination, the destination returns ICMP
Destination Unreachable Messages indicating an unreachable port. This
event indicates to the Traceroute application that it is finished.
The Traceroute program displays the round-trip delay associated with
each of the attempts.
Note that IP routing may be asymmetric. While Traceroute reveals the
path between a source and destination, it may not reveal the reverse
path.
3.3. Bidirectional Forwarding Detection (BFD)
3.3.1. Overview
While multiple OAM mechanisms have been defined for various protocols
in the protocol stack, Bidirectional Forwarding Detection [BFD],
defined by the IETF BFD working group, is a generic OAM mechanism
that can be deployed over various encapsulating protocols, and in
various medium types. The IETF has defined variants of the protocol
for IP ([BFD IP], [BFD Multi]), for MPLS LSPs [BFD LSP], and for PWE3
[BFD VCCV]. The usage of BFD in MPLS-TP is defined in [MPLS-TP CC
CV].
BFD includes two main OAM functions, using two types of BFD packets:
BFD Control packets, and BFD Echo packets.
3.3.2. BFD Control
BFD supports a bidirectional continuity check, using BFD control
packets, that are exchanged within a BFD session. BFD sessions
operate in one of two modes:
o Asynchronous mode (i.e. proactive): in this mode BFD control
packets are sent periodically. When the receiver detects that no
BFD control packet have been received during a predetermined
period of time, a failure is detected.
Mizrahi, et al. Expires September 12, 2012 [Page 14]
Internet-Draft Overview of OAM Mechanisms March 2012
o Demand mode: in this mode, BFD control packets are sent on-demand.
Upon need, a system initiates a series of BFD control packets to
verify the liveness of the session. BFD control packets are sent
independently in each direction.
Each of the end-points of the monitored path maintains its own
session identification, called a Discriminator, both of which are
included in the BFD Control Packets that are exchanged between the
end-points. At the time of session establishment, the Discriminators
are exchanged between the two-end points. In addition, the
transmission (and reception) rate is negotiated between the two end-
points, based on information included in the control packets. These
transmission rates may be renegotiated during the session.
During normal operation of the session, i.e. no failures are
detected, the BFD session is in the Up state. If no BFD Control
packets are received during a fixed period of time, called the
Detection Time, the session is declared to be Down. The detection
time is a function of the negotiated transmission time, and a
parameter called Detect Mult. Detect Mult determines the number of
missing BFD Control packets that cause the session to be declared as
Down. This parameter is included in the BFD Control packet.
3.3.3. BFD Echo
A BFD echo packet is sent to a peer system, and is looped back to the
originator. The echo function can be used proactively, or on-demand.
The BFD echo function has been defined in BFD for IPv4 and IPv6 ([BFD
IP]), but is not used in BFD for MPLS LSPs, PWs, or in BFD for MPLS-
TP.
3.4. LSP Ping
The IETF MPLS working group has defined OAM for MPLS LSPs. The
requirements and framework of this effort are defined in [MPLS OAM
FW] and [MPLS OAM], respectively. The corresponding OAM mechanism
defined, in this context, is LSP Ping [LSP Ping].
LSP Ping is based on ICMP Ping and just like its predecessor may be
used in one of two modes:
o "Ping" mode: In this mode LSP ping is used for end-to-end
connectivity verification between two LERs.
o "Traceroute" mode: This mode is used for hop-by-hop fault
isolation.
Mizrahi, et al. Expires September 12, 2012 [Page 15]
Internet-Draft Overview of OAM Mechanisms March 2012
LSP Ping extends the basic ICMP Ping operation (of data-plane
connectivity verification) with functionality to verify data-plane
vs. control-plane consistency for a Forwarding Equivalence Class
(FEC) and also Maximum Transmission Unit (MTU) problems. The
traceroute functionality may be used to isolate and localize the MPLS
faults, using the Time-to-live (TTL) indicator to incrementally
identify the sub-path of the LSP that is successfully traversed
before the faulty link or node.
It should be noted that LSP Ping supports unique identification of
the LSP within an addressing domain. The identification is checked
using the full FEC identification. LSP Ping is easily extensible to
include additional information needed to support new functionality,
by use of Type-Length-Value (TLV) constructs. The usage of TLVs is
typically not easy to perform in hardware, and is thus typically
handled by the control plane.
LSP Ping supports both asynchronous, as well as, on-demand
activation.
3.5. PWE3 Virtual Circuit Connectivity Verification (VCCV)
VCCV, as defined in [VCCV], provides a means for end-to-end fault
detection and diagnostics tools to be extended for PWs (regardless of
the underlying tunneling technology). The VCCV switching function
provides a control channel associated with each PW (based on the PW
Associated Channel Header (ACH) which is defined in [PW ACH]), and
allows transmitting the OAM packets in-band with PW data (using CC
Type 1: In-band VCCV).
VCCV currently supports the following OAM mechanisms: ICMP Ping, LSP
Ping, and BFD. ICMP and LSP Ping are IP encapsulated before being
sent over the PW ACH. BFD for VCCV supports two modes of
encapsulation - either IP/UDP encapsulated (with IP/UDP header) or
PW-ACH encapsulated (with no IP/UDP header) and provides support to
signal the AC status. The use of the VCCV control channel provides
the context, based on the MPLS-PW label, required to bind and
bootstrap the BFD session to a particular pseudo wire (FEC),
eliminating the need to exchange Discriminator values.
VCCV consists of two components: (1) signaled component to
communicate VCCV capabilities as part of VC label, and (2) switching
component to cause the PW payload to be treated as a control packet.
VCCV is not directly dependent upon the presence of a control plane.
The VCCV capability negotiation may be performed as part of the PW
signaling when LDP is used. In case of manual configuration of the
Mizrahi, et al. Expires September 12, 2012 [Page 16]
Internet-Draft Overview of OAM Mechanisms March 2012
PW, it is the responsibility of the operator to set consistent
options at both ends.
3.6. IP Performance Metrics (IPPM)
3.6.1. Overview
The IPPM working group in the IETF defines common criteria and
metrics for measuring performance of IP traffic ([IPPM FW]). Some of
the key RFCs published by this working group have defined metrics for
measuring connectivity [IPPM Con], delay ([IPPM 1DM], [IPPM 2DM]),
and packet loss [IPPM 1LM].
Alternative protocols for performance measurement are defined, for
example, in MPLS-TP OAM ([MPLS LM DM], [TP LM DM]), and in Ethernet
OAM [ITU-T Y.1731].
The IPPM working group has defined not only metrics for performance
measurement, but also protocols that define how the measurement is
carried out. The One-way Active Measurement Protocol [OWAMP] and the
Two-Way Active Measurement Protocol [TWAMP] define a method and
protocol for measuring delay and packet loss in IP networks.
OWAMP [OWAMP] enables measurement of one-way characteristics of IP
networks, such as one-way packet loss and one-way delay. For its
proper operation OWAMP requires accurate time of day setting at its
end points.
TWAMP [TWAMP] is a similar protocol that enables measurement of two-
way (round trip) characteristics. TWAMP does not require accurate
time of day, and, furthermore, allows the use of a simple session
reflector, making it an attractive alternative to OWAMP.
OWAMP and TWAMP use two separate protocols: a Control plane protocol,
and a Test plane protocol.
3.6.2. Control and Test Protocols
OWAMP and TWAMP control protocols run over TCP, while the test
protocols run over UDP. The purpose of the control protocols is to
initiate, start, and stop test sessions, and for OWAMP to fetch
results. The test protocols introduce test packets (which contain
sequence numbers and timestamps) along the IP path under test
according to a schedule, and record statistics of packet arrival.
Multiple sessions may be simultaneously defined, each with a session
identifier, and defining the number of packets to be sent, the amount
of padding to be added (and thus the packet size), the start time,
Mizrahi, et al. Expires September 12, 2012 [Page 17]
Internet-Draft Overview of OAM Mechanisms March 2012
and the send schedule (which can be either a constant time between
test packets or exponentially distributed pseudo-random). Statistics
recorded conform to the relevant IPPM RFCs.
OWAMP and TWAMP test traffic is designed with security in mind. Test
packets are hard to detect because they are simply UDP streams
between negotiated port numbers, with potentially nothing static in
the packets. OWAMP and TWAMP also include optional authentication
and encryption for both control and test packets.
3.6.3. OWAMP
OWAMP defines the following logical roles: Session-Sender, Session-
Receiver, Server, Control-Client, and Fetch-Client. The Session-
Sender originates test traffic that is received by the Session-
Receiver. The Server configures and manages the session, as well as
returning the results. The Control-Client initiates requests for
test sessions, triggers their start, and may trigger their
termination. The Fetch-Client requests the results of a completed
session. Multiple roles may be combined in a single host - for
example, one host may play the roles of Control-Client, Fetch-Client,
and Session-Sender, and a second playing the roles of Server and
Session-Receiver.
In a typical OWAMP session the Control-Client establishes a TCP
connection to port 861 of the Server, which responds with a server
greeting message indicating supported security/integrity modes. The
Control-Client responds with the chosen communications mode and the
Server accepts the modes. The Control-Client then requests and fully
describes a test session to which the Server responds with its
acceptance and supporting information. More than one test session
may be requested with additional messages. The Control-Client then
starts a test session and the Server acknowledges. The Session-
Sender then sends test packets with pseudorandom padding to the
Session-Receiver until the session is complete or until the Control-
client stops the session. Once finished, the Fetch-Client sends a
fetch request to the server, which responds with an acknowledgement
and immediately thereafter the result data.
3.6.4. TWAMP
TWAMP defines the following logical roles: session-sender, session-
reflector, server, and control-client. These are similar to the
OWAMP roles, except that the Session-Reflector does not collect any
packet information, and there is no need for a Fetch-Client.
Mizrahi, et al. Expires September 12, 2012 [Page 18]
Internet-Draft Overview of OAM Mechanisms March 2012
In a typical TWAMP session the Control-Client establishes a TCP
connection to port 862 of the Server, and mode is negotiated as in
OWAMP. The Control-Client then requests sessions and starts them.
The Session-Sender sends test packets with pseudorandom padding to
the Session-Reflector which returns them with insertion of
timestamps.
3.7. MPLS-TP OAM
3.7.1. Overview
The MPLS working group is currently working on defining the OAM
toolset that fulfills the requirements for MPLS-TP OAM. The full set
of requirements for MPLS-TP OAM are defined in [MPLS-TP OAM], and
include both general requirements for the behavior of the OAM
mechanisms and a set of operations that should be supported by the
OAM toolset. The set of mechanisms required are further elaborated
in [TP OAM FW], which describes the general architecture of the OAM
system as well as giving overviews of the functionality of the OAM
toolset.
Some of the basic requirements for the OAM toolset for MPLS-TP are:
o 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 OAM packets and the user traffic are required to be 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.
3.7.2. Generic Associated Channel
In order to address the requirement for in-band transmission of MPLS-
TP OAM traffic, MPLS-TP uses a Generic Associated Channel (G-ACh),
defined in [G-ACh] for LSP-based OAM traffic. This mechanism is based
on the same concepts as the PWE3 ACH and VCCV mechanisms. However,
to address the needs of LSPs as differentiated from PW, the following
concepts were defined for [G-ACh]:
Mizrahi, et al. Expires September 12, 2012 [Page 19]
Internet-Draft Overview of OAM Mechanisms March 2012
o An Associated Channel Header (ACH), that uses a format similar to
the PW Control Word, is a 4-byte header that is prepended to OAM
packets.
o A Generic Associated Label (GAL). The GAL is a reserved MPLS label
value (13) that indicates that the packet is an ACH packet and the
payload follows immediately after the label stack.
3.7.3. MPLS-TP OAM Toolset
To address the functionality that is required of the OAM toolset, the
MPLS WG conducted an analysis of the existing IETF and ITU-T OAM
mechanisms and their ability to fulfill the required functionality.
The conclusions of this analysis are documented in [OAM Analysis].
The MPLS working group currently plans to use a mixture of OAM
mechanisms that are based on various existing standards, and adapt
them to the requirements of [MPLS-TP OAM]. Some of the main building
blocks of this solution are based on:
o Bidirectional Forwarding Detection ([BFD], [BFD LSP]) for
proactive continuity check and connectivity verification.
o LSP Ping as defined in [LSP Ping] for on-demand connectivity
verification.
o New protocol packets, using G-ACH, to address different
functionality.
o Performance measurement protocols that are based on the
functionality that is described in [ITU-T Y.1731].
The following sub-sections describe the OAM tools defined for MPLS-TP
as described in [TP OAM FW].
3.7.3.1. Continuity Check and Connectivity Verification
Continuity Check and Connectivity Verification are presented in
Section 2.2.5 of this document. As presented there, these tools may
be used either proactively or on-demand. When using these tools
proactively, they are generally used in tandem.
For MPLS-TP there are two distinct tools, the proactive tool is
defined in [MPLS-TP CC CV] while the on-demand tool is defined in
[OnDemand CV].Proactively [MPLS-TP OAM] 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.
Mizrahi, et al. Expires September 12, 2012 [Page 20]
Internet-Draft Overview of OAM Mechanisms March 2012
[TP OAM FW] highlights, when performing Connectivity Verification,
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 proactive tool [MPLS-TP CC CV] is based on extensions to BFD (see
Section 3.3) with the additional limitation that the transmission and
receiving rates are based on configuration by the operator. The on-
demand tool [OnDemand CV] is an adaptation of LSP Ping (See Section
3.4) for the required behavior of MPLS-TP.
3.7.3.2. Route Tracing
[MPLS-TP OAM] 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 a
return path exists. The tool for this is based on the LSP Ping (See
Section 3.4) functionality and is described in [OnDemand CV].
3.7.3.3. Lock Instruct
The Lock Instruct function is used to notify a transport path end-
point of an administrative need to disable the transport path. This
functionality will generally be used in conjunction with some
intrusive OAM function, e.g. Performance measurement, Diagnostic
testing, to minimize the side-effect on user data traffic.
3.7.3.4. Lock Reporting
Lock Reporting is a function used by an end-point of a path to report
to its far-end end-point that a lock condition has been affected on
the path.
3.7.3.5. 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. [TP OAM FW] 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 [TP OAM FW].
Mizrahi, et al. Expires September 12, 2012 [Page 21]
Internet-Draft Overview of OAM Mechanisms March 2012
3.7.3.6. Remote Defect Indication
Remote Defect Indication (RDI) is used proactively by a path end-
point to report to its peer end-point that a defect is detected on a
bidirectional connection between them. [MPLS-TP OAM] points out that
this function may be applied to a unidirectional LSP only if there a
return path exists. [TP OAM FW] points out that this function is
associated with the proactive CC-V function.
3.7.3.7. Client Failure Indication
Client Failure Indication (CFI) is defined in [MPLS-TP OAM] 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.
3.7.3.8. Packet Loss Measurement
Packet Loss Measurement is a function used to verify the quality of
the service. This function indicates the ratio of packets that are
not delivered out of all packets that are transmitted by the path
source.
There are two possible ways of determining this measurement:
o Using OAM packets, it is possible to compute the statistics based
on a series of OAM packets. This, however, has the disadvantage of
being artificial, and may not be representative since part of the
packet loss may be dependent upon packet sizes.
o Sending delimiting messages for the start and end of a measurement
period during which the source and sink of the path count the
packets transmitted and received. After the end delimiter, the
ratio would be calculated by the path OAM entity.
3.7.3.9. 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). 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.
Mizrahi, et al. Expires September 12, 2012 [Page 22]
Internet-Draft Overview of OAM Mechanisms March 2012
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.
Similarly to the packet loss measurement this could be performed in
either of the two ways outlined above.
3.8. Summary of OAM Functions
Table 3 summarizes the OAM functions that are supported in each of
the standards that were analyzed in this section.
+-----------+-------+--------+--------+-----------+-------+--------+
| Standard |Continu|Connecti|Path |Defect |Perform|Other |
| |ity |vity |Discover|Indications|ance |Function|
| |Check |Verifica|y | |Monitor|s |
| | |tion | | |ing | |
+-----------+-------+--------+--------+-----------+-------+--------+
|ICMP Ping | |Echo | | | | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|Traceroute | | |Tracerou| | | |
| | | |te | | | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|BFD |BFD |BFD | | | | |
| |Control|Echo | | | | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|LSP Ping | |"Ping" |"Tracero| | | |
| | |mode |ute" | | | |
| | | |mode | | | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|IPPM | | | | |-Delay | |
| | | | | | measur| |
| | | | | | ement | |
| | | | | |-Packet| |
| | | | | | loss | |
| | | | | | measur| |
| | | | | | ement | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|MPLS-TP |CC |CV/pro- |Route |-Alarm |-LM |-Diagnos|
|OAM | |active |Tracing | Reporting |-DM | tic Tes|
| | |or on- | |-Client | | t |
Mizrahi, et al. Expires September 12, 2012 [Page 23]
Internet-Draft Overview of OAM Mechanisms March 2012
| | |demand | | Failure | |-Lock |
| | | | | Indication| | |
| | | | |-Remote | | |
| | | | | Defect | | |
| | | | | Indication| | |
+-----------+-------+--------+--------+-----------+-------+--------+
Table 3 Summary of OAM Functions
4. Security Considerations
This memo presents an overview of existing OAM mechanisms, and
proposes no new OAM mechanisms. Therefore, this document introduces
no security considerations. However, the OAM mechanism reviewed in
this document can and do present security issues. The reader is
encouraged to review the Security Considerations section of each
document reference by this memo.
5. IANA Considerations
There are no new IANA considerations implied by this document.
6. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
7. References
7.1. Normative References
[LSP Ping] Kompella, K., Swallow, G., "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[MPLS OAM] Nadeau, T., Morrow, M., Swallow, G., Allan, D., and
Matsushima, S., "Operations and Management (OAM)
Requirements for Multi-Protocol Label Switched (MPLS)
Networks", RFC 4377, February 2006.
[MPLS OAM FW] Allan, D., Nadeau, T., "A Framework for Multi-Protocol
Label Switching (MPLS) Operations and Management
(OAM)", RFC 4378, February 2006.
[OAM Label] Ohta, H., "Assignment of the 'OAM Alert Label' for
Multiprotocol Label Switching Architecture (MPLS)
Operation and Maintenance (OAM) Functions", RFC 3429,
November 2002.
Mizrahi, et al. Expires September 12, 2012 [Page 24]
Internet-Draft Overview of OAM Mechanisms March 2012
[MPLS-TP OAM] Vigoureux, M., Ward, D., Betts, M., "Requirements for
OAM in MPLS Transport Networks", RFC 5860, May 2010.
[G-ACh] Bocci, M., Vigoureux, M., Bryant, S., "MPLS Generic
Associated Channel", RFC 5586, June 2009.
[VCCV] Nadeau, T., Pignataro, C., "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel
for Pseudowires", RFC 5085, December 2007.
[PW ACH] Bryant, S., Swallow, G., Martini, L., McPherson, D.,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word
for Use over an MPLS PSN", RFC 4385, February 2006.
[ICMPv4] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, September 1981.
[ICMPv6] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.
[TCPIP Tools] Kessler, G., Shepard, S., "A Primer On Internet and
TCP/IP Tools and Utilities", RFC 2151, June 1997.
[IPPM FW] Paxson, V., Almes, G., Mahdavi, J., and Mathis, M.,
"Framework for IP Performance Metrics", RFC 2330, May
1998.
[IPPM Con] Mahdavi, J., Paxson, V., "IPPM Metrics for Measuring
Connectivity", RFC 2678, September 1999.
[IPPM 1DM] Almes, G., Kalidindi, S., Zekauskas, M., "A One-way
Delay Metric for IPPM", RFC 2679, September 1999.
[IPPM 1LM] Almes, G., Kalidindi, S., Zekauskas, M., "A One-way
Packet Loss Metric for IPPM", RFC 2680, September
1999.
[IPPM 2DM] Almes, G., Kalidindi, S., Zekauskas, M., "A Round-trip
Delay Metric for IPPM", RFC 2681, September 1999.
[OWAMP] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and
Zekauskas, M., "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006.
Mizrahi, et al. Expires September 12, 2012 [Page 25]
Internet-Draft Overview of OAM Mechanisms March 2012
[TWAMP] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and
Babiarz, J., "A Two-Way Active Measurement Protocol
(TWAMP)", RFC 5357, October 2008.
[BFD] Katz, D., Ward, D., "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010.
[BFD IP] Katz, D., Ward, D., "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June
2010.
[BFD Gen] Katz, D., Ward, D., "Generic Application of
Bidirectional Forwarding Detection (BFD)", RFC 5882,
June 2010.
[BFD Multi] Katz, D., Ward, D., "Bidirectional Forwarding Detection
(BFD) for Multihop Paths", RFC 5883, June 2010.
[BFD LSP] Aggarwal, R., Kompella, K., Nadeau, T., and Swallow,
G., "Bidirectional Forwarding Detection (BFD) for MPLS
Label Switched Paths (LSPs)", RFC 5884, June 2010.
[BFD VCCV] Nadeau, T., Pignataro, C., "Bidirectional Forwarding
Detection (BFD) for the Pseudowire Virtual Circuit
Connectivity Verification (VCCV)", RFC 5885, June
2010.
[TP OAM FW] Busi, I., Allan, D., "Operations, Administration and
Maintenance Framework for MPLS-based Transport
Networks ", RFC 6371, September 2011.
[MPLS-TP CC CV] Allan, D., Swallow, G., Drake, J., "Proactive
Connectivity Verification, Continuity Check and Remote
Defect indication for MPLS Transport Profile", RFC
6428, November 2011.
[OnDemand CV] Gray, E., Bahadur, N., Boutros, S., Aggarwal, R. "MPLS
On-Demand Connectivity Verification and Route
Tracing", RFC 6426, November 2011.
[MPLS LM DM] Frost, D., Bryant, S., "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374, September
2011.
[TP LM DM] Frost, D., Bryant, S., "A Packet Loss and Delay
Measurement Profile for MPLS-Based Transport
Networks", RFC 6375, September 2011.
Mizrahi, et al. Expires September 12, 2012 [Page 26]
Internet-Draft Overview of OAM Mechanisms March 2012
[MPLS-TP Fault] Swallow, G., Fulignoli, A., Vigoureux, M., Boutros,
S., "MPLS Fault Management Operations, Administration,
and Maintenance (OAM)", RFC 6427, November 2011.
[TP Lock Loop] Boutros, S., Sivabalan, S., Aggarwal, R., Vigoureux,
M., Dai, X., "MPLS Transport Profile Lock Instruct and
Loopback Functions", RFC 6435, November 2011.
7.2. Informative References
[OAM Def] Andersson, L., Van Helvoort, H., Bonica, R., Romascanu,
D., Mansfield, S., "Guidelines for the use of the OAM
acronym in the IETF ", RFC 6291, June 2011.
[OAM Analysis]Sprecher, N., Fang, L., "An Overview of the OAM Tool
Set for MPLS based Transport Networks", work-in-
progress, draft-ietf-mpls-tp-oam-analysis, March 2012.
[MPLS-TP Term]Van Helvoort, H., Andersson, L., Sprecher, N., "A
Thesaurus for the Terminology used in Multiprotocol
Label Switching Transport Profile (MPLS-TP)
drafts/RFCs and ITU-T's Transport Network
Recommendations", work-in-progress, draft-ietf-mpls-
tp-rosetta-stone, January 2012.
[IEEE 802.1ag]"Connectivity Fault Management", December 2007.
[ITU-T Y.1731]"OAM Functions and Mechanisms for Ethernet-based
Networks", February 2008.
[ITU-T Y.1711]"Operation & Maintenance mechanism for MPLS networks",
February 2004.
[IEEE 802.3ah]"Media Access Control Parameters, Physical Layers, and
Management Parameters for Subscriber Access Networks",
clause 57, September 2004.
[ITU-T G.806] "Characteristics of transport equipment - Description
methodology and generic functionality", January, 2009.
Mizrahi, et al. Expires September 12, 2012 [Page 27]
Internet-Draft Overview of OAM Mechanisms March 2012
Authors' Addresses
Tal Mizrahi
Marvell
6 Hamada St.
Yokneam, 20692
Israel
Email: talmi@marvell.com
Nurit Sprecher
Nokia Siemens Networks
3 Hanagar St. Neve Ne'eman B
Hod Hasharon, 45241
Israel
Email: nurit.sprecher@nsn.com
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
Mizrahi, et al. Expires September 12, 2012 [Page 28]