draft-ietf-opsawg-oam-overview-08.txt   draft-ietf-opsawg-oam-overview-09.txt 
Operations and Management Area Working Group T. Mizrahi Operations and Management Area Working Group T. Mizrahi
Internet Draft Marvell Internet Draft Marvell
Intended status: Informational N. Sprecher Intended status: Informational N. Sprecher
Expires: July 2013 Nokia Siemens Networks Expires: January 2014 Nokia Siemens Networks
E. Bellagamba E. Bellagamba
Ericsson Ericsson
Y. Weingarten Y. Weingarten
January 9, 2013 July 9, 2013
An Overview of An Overview of
Operations, Administration, and Maintenance (OAM) Mechanisms Operations, Administration, and Maintenance (OAM) Mechanisms
draft-ietf-opsawg-oam-overview-08.txt draft-ietf-opsawg-oam-overview-09.txt
Abstract Abstract
Operations, Administration, and Maintenance (OAM) is a general term Operations, Administration, and Maintenance (OAM) is a general term
that refers to a toolset that can be used for fault detection and that refers to a toolset for fault detection and isolation, and for
isolation, and for performance measurement. OAM mechanisms have been performance measurement. OAM mechanisms have been defined for various
defined for various layers in the protocol stack, and are used with a layers in the protocol stack, and are used with a variety of
variety of protocols. transport protocols.
This document presents an overview of the OAM mechanisms that have This document presents an overview of the data plane OAM tools that
been defined and are currently being defined by the IETF. have been defined by the IETF.
Status of this Memo Status of this Memo
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Table of Contents Table of Contents
1. Introduction ................................................. 3 1. Introduction ................................................. 3
1.1. The Building Blocks of OAM .............................. 3 1.1. Background .............................................. 4
1.2. Forwarding Plane vs. Management Plane ................... 4 1.2. Target Audience.......................................... 4
1.3. The OAM toolsets ........................................ 4 1.3. OAM-related Work in the IETF ............................ 5
1.4. IETF OAM Documents ...................................... 6 1.4. Focusing on Data Plane OAM Tools ........................ 6
1.5. Non-IETF OAM Documents ................................. 10 2. Terminology .................................................. 6
2. Basic Terminology ........................................... 12 2.1. Abbreviations ........................................... 6
2.1. Abbreviations .......................................... 12 2.2. Terminology used in OAM Standards ....................... 8
2.2. Terminology used in OAM Standards ...................... 13 2.2.1. General Terms ...................................... 8
2.2.1. General Terms ..................................... 13 2.2.2. Functions, Mechanisms, Tools and Protocols ......... 8
2.2.2. OAM Maintenance Entities .......................... 13 2.2.3. Data Plane, Control Plane and Management Plane ..... 9
2.2.3. OAM Maintenance Points ............................ 14 2.2.4. The Players ....................................... 10
2.2.4. Proactive and On-demand activation ................ 15 2.2.5. Proactive and On-demand Activation ................ 11
2.2.5. Connectivity Verification and Continuity Checks ... 15 2.2.6. Connectivity Verification and Continuity Checks ... 11
2.2.6. Failures .......................................... 15 2.2.7. Failures .......................................... 12
3. OAM Tools ................................................... 16 3. OAM Functions ............................................... 12
3.1. IP Ping and Traceroute ................................. 16 4. OAM Mechanisms in the IETF - a Detailed Description.......... 13
3.1.1. Ping .............................................. 16 4.1. IP Ping ................................................ 13
3.1.2. Traceroute......................................... 16 4.2. IP Traceroute .......................................... 14
3.2. Bidirectional Forwarding Detection (BFD) ............... 17 4.3. Bidirectional Forwarding Detection (BFD) ............... 15
3.2.1. Overview .......................................... 17 4.3.1. Overview .......................................... 15
3.2.2. BFD Control ....................................... 17 4.3.2. Terminology ....................................... 15
3.2.3. BFD Echo .......................................... 18 4.3.3. BFD Control ....................................... 15
3.3. MPLS OAM ............................................... 18 4.3.4. BFD Echo .......................................... 16
3.4. MPLS-TP OAM ............................................ 19 4.4. MPLS OAM ............................................... 16
3.4.1. Overview .......................................... 19 4.5. MPLS-TP OAM ............................................ 17
3.4.2. Generic Associated Channel ........................ 19 4.5.1. Overview .......................................... 17
3.4.3. MPLS-TP OAM Toolset ............................... 20 4.5.2. Terminology ....................................... 17
3.4.3.1. Continuity Check and Connectivity Verification 20 4.5.3. Generic Associated Channel ........................ 19
3.4.3.2. Route Tracing ................................ 21 4.5.4. MPLS-TP OAM Toolset ............................... 19
3.4.3.3. Lock Instruct ................................ 21 4.5.4.1. Continuity Check and Connectivity Verification 20
3.4.3.4. Lock Reporting ............................... 21 4.5.4.2. Route Tracing ................................ 20
3.4.3.5. Alarm Reporting .............................. 21 4.5.4.3. Lock Instruct ................................ 20
3.4.3.6. Remote Defect Indication ..................... 22 4.5.4.4. Lock Reporting ............................... 21
3.4.3.7. Client Failure Indication .................... 22 4.5.4.5. Alarm Reporting .............................. 21
3.4.3.8. Packet Loss Measurement (LM) ................. 22 4.5.4.6. Remote Defect Indication ..................... 21
3.4.3.9. Packet Delay Measurement (DM) ................ 22 4.5.4.7. Client Failure Indication .................... 21
3.5. PWE3 OAM ............................................... 23 4.5.4.8. Performance Monitoring ....................... 21
3.5.1. PWE3 OAM using Virtual Circuit Connectivity Verification 4.5.4.8.1. Packet Loss Measurement (LM) ............ 22
(VCCV) ................................................... 23 4.5.4.8.2. Packet Delay Measurement (DM) ........... 22
3.5.2. PWE3 OAM using G-ACh .............................. 24 4.6. Pseudowire OAM ......................................... 23
3.6. OWAMP and TWAMP......................................... 24 4.6.1. Pseudowire OAM using Virtual Circuit Connectivity
3.6.1. Overview .......................................... 24 Verification (VCCV) ...................................... 23
3.6.2. Control and Test Protocols ........................ 24 4.6.2. Pseudowire OAM using G-ACh ........................ 24
3.6.3. OWAMP ............................................. 25 4.6.3. Attachment Circuit - Pseudowire Mapping ........... 24
3.6.4. TWAMP ............................................. 26 4.7. OWAMP and TWAMP......................................... 24
3.7. Summary of OAM Functions ............................... 26 4.7.1. Overview .......................................... 24
4. Security Considerations ..................................... 27 4.7.2. Control and Test Protocols ........................ 25
5. IANA Considerations ......................................... 27 4.7.3. OWAMP ............................................. 25
6. Acknowledgments ............................................. 27 4.7.4. TWAMP ............................................. 26
7. References .................................................. 28 4.8. TRILL .................................................. 26
7.1. Normative References ................................... 28 4.9. Summary of OAM Mechanisms .............................. 27
7.2. Informative References ................................. 31 4.10. Summary of OAM Functions .............................. 29
5. Security Considerations ..................................... 30
6. IANA Considerations ......................................... 31
7. Acknowledgments ............................................. 31
8. References .................................................. 31
8.1. Informative References ................................. 31
Appendix A. List of OAM Documents .............................. 36
A.1. List of IETF OAM Documents ............................. 36
A.2. List of Selected Non-IETF OAM Documents ................ 41
1. Introduction 1. Introduction
OAM is a general term that refers to a toolset for detecting, OAM is a general term that refers to a toolset for detecting,
isolating and reporting connection failures and performance isolating and reporting failures and for monitoring the network
degradation. performance.
This document summarizes the OAM tools and mechanisms defined in the There are several different interpretations to the "OAM" acronym.
IETF. This document refers to Operations, Administration and Maintenance,
as recommended in [OAM-Def].
The term OAM in this document refers to Operations, Administration This document summarizes the OAM tools and mechanisms defined in the
and Maintenance [OAM-Def], focusing on the forwarding plane of OAM. IETF. This document focuses on data plane OAM tools. Hence, control
Hence, management aspects are outside the scope of this document. and management aspects of OAM are outside the scope of this document.
1.1. The Building Blocks of OAM 1.1. Background
An OAM protocol is run in the context of a Maintenance Domain, OAM was originally used in traditional transport technologies such as
consisting of two or more nodes that run the OAM protocol, referred E1 and T1, evolving into PDH and then later in SONET/SDH. ATM was
to as Maintenance Points (MP). probably the first technology to include inherent OAM mechanisms from
day one, while in other transport technologies OAM was typically
defined in an ad hoc manner after the technology was already defined
and deployed. Packet-based networks were traditionally considered
unreliable and best-effort, but as packet-based networks evolved,
they have become the common transport for both data and telephony,
replacing traditional transport protocols. Consequently, packet-based
networks were expected to provide a similar "carrier grade"
experience, and specifically to support OAM.
This subsection provides a brief summary of the common tools used by OAM typically has a multi-layer architecture; each transport
OAM protocols. An OAM protocol typically supports one or more of the technology has its own OAM mechanisms. Moreover, OAM can be used at
tools described below. different levels of hierarchy in the network to form a multi-layer
OAM solution, as shown in the example in Figure 1.
o Continuity Checking (CC): Figure 1 illustrates a network in which IP traffic between two
Used for verifying the liveness of a connection between two MPs. customer edges is transported over an MPLS provider network. MPLS OAM
is used at the provider-level for monitoring the connection between
the two provider edges, while IP OAM is used at the customer-level
for monitoring the end-to-end connection between the two customer
edges.
o Connectivity Verification (CV): |<-------------- Customer-level OAM -------------->|
Allows an MP to check whether it is connected to a peer MP, and to IP OAM (Ping, Traceroute, OWAMP, TWAMP)
verify that messages from the peer MP are received through the
expected path.
o Path Discovery / Fault Localization: |<- Provider-level OAM ->|
An MP uses this mechanism to trace the route to a peer MP, i.e., MPLS OAM (LSP Ping)
to identify the nodes along the path to the peer MP. When a
connection fails, this mechanism also allows the MP to detect the
location of the failure.
o Performance Monitoring: +-----+ +----+ +----+ +-----+
Consists of 3 main functions | | | |========================| | | |
| |-------| | MPLS | |-------| |
| | IP | | | | IP | |
+-----+ +----+ +----+ +-----+
Customer Provider Provider Customer
Edge Edge Edge Edge
o Loss Measurement (LM) - monitors the packet loss rate of a Figure 1 Example: Multi-layer OAM
connection.
o Delay Measurement (DM) - monitors the delay and delay 1.2. Target Audience
variation between MPs.
o Throughput measurement - monitors the throughput of a The target audience of this document includes:
connection.
1.2. Forwarding Plane vs. Management Plane o Standard development organizations - both IETF working groups and
non-IETF organizations can benefit from this document when
designing new OAM protocols, or when looking to reuse existing OAM
mechanisms for new transport technologies.
While the OAM tools may, and quite often do, work in conjunction with o Network equipment vendors and network operators - can use this
a control-plane or management plane, they are usually defined to be document as an index to existing IETF OAM mechanisms, and their
independent of the control-plane. The OAM tools communicate with the connection to various transport technologies.
management plane to raise alarms, and often the on-demand tools may
be activated by the management, e.g. to locate and localize problems.
The considerations of the control-plane maintenance tools or the It should be noted that this document is not necessarily suitable for
functionality of the management-plane are out of scope for this beginners without any background in OAM.
document, which will concentrate on presenting the forwarding-plane
tools that are used for OAM.
1.3. The OAM toolsets 1.3. OAM-related Work in the IETF
This memo provides an overview of the different sets of OAM This memo provides an overview of the different sets of OAM
mechanisms defined by the IETF. It is intended for those with little mechanisms defined by the IETF. The set of OAM mechanisms described
or no familiarity with the described mechanisms. The set of OAM in this memo are applicable to IP unicast, MPLS, pseudowires, MPLS
mechanisms described in this memo are applicable to IP unicast, MPLS, for the transport profile (MPLS-TP), and TRILL. While OAM mechanisms
pseudowires, and MPLS for the transport environment (MPLS-TP). While that are applicable to other technologies exist, they are beyond the
OAM mechanisms that are applicable to other technologies exist, they scope of this memo.
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 IP Ping and Traceroute:
Ping is a very simple and common application for failure diagnosis
that uses ICMP Echo requests, as defined in [ICMPv4], and
[ICMPv6].
Traceroute ([TCPIP-Tools], [NetTools]) is an application that
allows users to trace the path between an IP source and an IP
destination, i.e., to identify the nodes along the path.
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.
o MPLS OAM:
MPLS LSP Ping, as defined in [MPLS-OAM], [MPLS-OAM-FW] and [LSP-
Ping], is an OAM mechanism for point to point MPLS LSPs. It
includes two main functions: Ping and Traceroute.
o MPLS-TP OAM:
MPLS-TP OAM is defined in a set of RFCs. The OAM requirements for
MPLS Transport Profile (MPLS-TP) are defined in [MPLS-TP-OAM].
Each of the tools in the OAM toolset is defined in its own RFC, as
specified in Section 1.4.
o PWE3 OAM:
The PWE3 OAM architecture defines control channels that support
the use of existing IETF OAM tools to be used for a pseudowire
(PW). The control channels that are defined in [VCCV] and [PW-G-
ACH] may be used in conjunction with ICMP Ping, LSP Ping, and BFD
to perform CC and CV functionality. In addition the channels
support use of any of the MPLS-TP based OAM tools for completing
their respective OAM functionality for a PW.
o OWAMP and TWAMP:
The One Way Active Measurement Protocol (OWAMP) and the Two Way
Active Measurement Protocols (TWAMP) are two protocols defined in
the IP Performance Metrics (IPPM) working group in the IETF. These
protocols allow delay and packet loss measurement in IP networks.
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.
1.4. IETF OAM Documents
Table 1 summarizes the IETF OAM related RFCs 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 This document focuses on IETF documents that have been published as
framework documents. RFCs, while other ongoing OAM-related work is outside the scope.
+-----------+--------------------------------------+-----+----------+ The IETF has defined OAM protocols and mechanisms in several
| | Title |Type | RFC | different contexts. We roughly categorize these efforts into a few
+-----------+--------------------------------------+-----+----------+ sets of OAM-related RFCs, listed in Table 1. Each category defines a
|IP Ping and| Internet Control Message Protocol |Tool | RFC 792 | logically-coupled set of RFCs, although the sets are in some cases
|Traceroute | [ICMPv4] | | | intertwined by common tools and protocols.
| +--------------------------------------+-----+----------+
| | Internet Control Message Protocol |Tool | RFC 4443 |
| | (ICMPv6) for the Internet Protocol | | |
| | Version 6 (IPv6) Specification | | |
| | [ICMPv6] | | |
| +--------------------------------------+-----+----------+
| | A Primer On Internet and TCP/IP |Tool | RFC 2151 |
| | Tools and Utilities [TCPIP-Tools] | | |
| +--------------------------------------+-----+----------+
| | FYI on a Network Management Tool |Tool | RFC 1147 |
| | Catalog: Tools for Monitoring and | | |
| | Debugging TCP/IP Internets and | | |
| | Interconnected Devices [NetTools] | | |
| +--------------------------------------+-----+----------+
| | Extended ICMP to Support Multi-Part |Tool | RFC 4884 |
| | Messages [ICMP-MP] | | |
| +--------------------------------------+-----+----------+
| | ICMP Extensions for Multiprotocol |Tool | RFC 4950 |
| | Label Switching [ICMP-Ext] | | |
| +--------------------------------------+-----+----------+
| | Extending ICMP for Interface and |Tool | RFC 5837 |
| | Next-Hop Identification [ICMP-Int] | | |
+-----------+--------------------------------------+-----+----------+
|BFD | Bidirectional Forwarding Detection |Tool | RFC 5880 |
| | [BFD] | | |
| +--------------------------------------+-----+----------+
| | Bidirectional Forwarding Detection |Prof.| RFC 5881 |
| | (BFD) for IPv4 and IPv6 (Single Hop) | | |
| | [BFD-IP] | | |
| +--------------------------------------+-----+----------+
| | Generic Application of Bidirectional |Misc.| RFC 5882 |
| | Forwarding Detection [BFD-Gen] | | |
| +--------------------------------------+-----+----------+
| | Bidirectional Forwarding Detection |Prof.| RFC 5883 |
| | (BFD) for Multihop Paths [BFD-Multi] | | |
| +--------------------------------------+-----+----------+
| | Bidirectional Forwarding Detection |Prof.| RFC 5884 |
| | for MPLS Label Switched Paths (LSPs) | | |
| | [BFD-LSP] | | |
| +--------------------------------------+-----+----------+
| | Bidirectional Forwarding Detection |Prof.| RFC 5885 |
| | for the Pseudowire Virtual Circuit | | |
| | Connectivity Verification (VCCV) | | |
| | [BFD-VCCV] | | |
+-----------+--------------------------------------+-----+----------+
|MPLS OAM | Operations and Management (OAM) |Misc.| RFC 4377 |
| | Requirements for Multi-Protocol Label| | |
| | Switched (MPLS) Networks [MPLS-OAM] | | |
| +--------------------------------------+-----+----------+
| | A Framework for Multi-Protocol |Misc.| RFC 4378 |
| | Label Switching (MPLS) Operations | | |
| | and Management (OAM) [MPLS-OAM-FW] | | |
| +--------------------------------------+-----+----------+
| | Detecting Multi-Protocol Label |Tool | RFC 4379 |
| | Switched (MPLS) Data Plane Failures | | |
| | [LSP-Ping] | | |
| +--------------------------------------+-----+----------+
| | Operations and Management (OAM) |Misc.| RFC 4687 |
| | Requirements for Point-to-Multipoint | | |
| | MPLS Networks [MPLS-P2MP] | | |
+-----------+--------------------------------------+-----+----------+
|MPLS-TP | Requirements for OAM in MPLS-TP |Misc.| RFC 5860 |
|OAM | [MPLS-TP-OAM] | | |
| +--------------------------------------+-----+----------+
| | MPLS Generic Associated Channel |Inf. | RFC 5586 |
| | [G-ACh] | | |
| +--------------------------------------+-----+----------+
| | MPLS-TP OAM Framework |Misc.| RFC 6371 |
| | [TP-OAM-FW] | | |
| +--------------------------------------+-----+----------+
| | Proactive Connectivity Verification, |Tool | RFC 6428 |
| | Continuity Check, and Remote Defect | | |
| | Indication for the MPLS Transport | | |
| | Profile [TP-CC-CV] | | |
| +--------------------------------------+-----+----------+
| | MPLS On-Demand Connectivity |Tool | RFC 6426 |
| | Verification and Route Tracing | | |
| | [OnDemand-CV] | | |
| +--------------------------------------+-----+----------+
| | MPLS Fault Management Operations, |Tool | RFC 6427 |
| | Administration, and Maintenance (OAM)| | |
| | [TP-Fault] | | |
| +--------------------------------------+-----+----------+
| | MPLS Transport Profile Lock Instruct |Tool | RFC 6435 |
| | and Loopback Functions [Lock-Loop] | | |
| +--------------------------------------+-----+----------+
| | Packet Loss and Delay Measurement for|Tool | RFC 6374 |
| | MPLS Networks [MPLS-LM-DM] | | |
| +--------------------------------------+-----+----------+
| | A Packet Loss and Delay Measurement |Prof.| RFC 6375 |
| | Profile for MPLS-Based Transport | | |
| | Networks [TP-LM-DM] | | |
+-----------+--------------------------------------+-----+----------+
|PWE3 OAM | Pseudowire Virtual Circuit |Inf. | RFC 5085 |
| | Connectivity Verification (VCCV): | | |
| | A Control Channel for Pseudowires | | |
| | [VCCV] | | |
| +--------------------------------------+-----+----------+
| | Bidirectional Forwarding Detection |Prof.| RFC 5885 |
| | for the Pseudowire Virtual Circuit | | |
| | Connectivity Verification (VCCV) | | |
| | [BFD-VCCV] | | |
| +--------------------------------------+-----+----------+
| | Using the Generic Associated Channel |Inf. | RFC 6423 |
| | Label for Pseudowire in the MPLS | | |
| | Transport Profile (MPLS-TP) | | |
| | [PW-G-ACh] | | |
| +--------------------------------------+-----+----------+
| | Pseudowire (PW) Operations, |Misc.| RFC 6310 |
| | Administration, and Maintenance (OAM)| | |
| | Message Mapping [PW-Map] | | |
+-----------+--------------------------------------+-----+----------+
|OWAMP and | A One-way Active Measurement Protocol|Tool | RFC 4656 |
|TWAMP | [OWAMP] | | |
| +--------------------------------------+-----+----------+
| | A Two-Way Active Measurement Protocol|Tool | RFC 5357 |
| | [TWAMP] | | |
| +--------------------------------------+-----+----------+
| | Framework for IP Performance Metrics |Misc.| RFC 2330 |
| | [IPPM-FW] | | |
| +--------------------------------------+-----+----------+
| | IPPM Metrics for Measuring |Misc.| RFC 2678 |
| | Connectivity [IPPM-Con] | | |
| +--------------------------------------+-----+----------+
| | A One-way Delay Metric for IPPM |Misc.| RFC 2679 |
| | [IPPM-1DM] | | |
| +--------------------------------------+-----+----------+
| | A One-way Packet Loss Metric for IPPM|Misc.| RFC 2680 |
| | [IPPM-1LM] | | |
| +--------------------------------------+-----+----------+
| | A Round-trip Delay Metric for IPPM |Misc.| RFC 2681 |
| | [IPPM-2DM] | | |
+-----------+--------------------------------------+-----+----------+
Table 1 Summary of IETF OAM Related RFCs
1.5. Non-IETF OAM Documents The discussion in this document is ordered according to these
categories.
In addition to the OAM mechanisms defined by the IETF, the IEEE and +--------------+------------+
ITU-T have also defined various OAM mechanisms that focus on | Category | Transport |
Ethernet, and various other transport network environments. These | | Technology |
various mechanisms, defined by the three standard organizations, are +--------------+------------+
often tightly coupled, and have had a mutual effect on each other. |IP Ping | IPv4/IPv6 |
The ITU-T and IETF have both defined OAM mechanisms for MPLS LSPs, +--------------+------------+
[ITU-T-Y1711] and [LSP-Ping]. The following OAM standards by the IEEE |IP Traceroute | IPv4/IPv6 |
and ITU-T are to some extent linked to IETF OAM mechanisms listed +--------------+------------+
above and are mentioned here only as reference material: |BFD | generic |
+--------------+------------+
|MPLS OAM | MPLS |
+--------------+------------+
|MPLS-TP OAM | MPLS-TP |
+--------------+------------+
|Pseudowire OAM| Pseudowires|
+--------------+------------+
|OWAMP and | IPv4/IPv6 |
|TWAMP | |
+--------------+------------+
|TRILL OAM | TRILL |
+--------------+------------+
Table 1 Categories of OAM-related IETF Documents
o OAM mechanisms for Ethernet based networks have been defined by 1.4. Focusing on Data Plane OAM Tools
both the ITU-T in [ITU-T-Y1731], and by the IEEE in [IEEE802.1ag].
The IEEE 802.3 standard defines OAM for one-hop Ethernet links
[IEEE802.3ah].
o The ITU-T has defined OAM for MPLS LSPs in [ITU-T-Y1711], and OAM tools may, and quite often do, work in conjunction with a control
MPLS-TP OAM in [ITU-G8113.1] and [ITU-G8113.2]. plane and/or management plane. The OAM tools communicate with the
management plane to raise alarms, and often OAM tools may be
activated by the management (as well as by the control plane), e.g.
to locate and localize problems.
Table 2 summarizes the OAM standards mentioned in this document. This The considerations of the control plane maintenance tools and the
document focuses on IETF OAM standards, but these non-IETF standards functionality of the management plane are out of scope for this
are referenced where relevant. document, which concentrates on presenting the data plane tools that
are used for OAM.
+-----------+--------------------------------------+---------------+ Since OAM protocols are used for monitoring the data plane, it is
| | Title |Standard/Draft | imperative for OAM tools to be capable of testing the actual data
+-----------+--------------------------------------+---------------+ plane in as much accuracy as possible. Thus, it is important to
|ITU-T | Operation & Maintenance mechanism | ITU-T Y.1711 | enforce fate-sharing between OAM traffic and the user-traffic it
|MPLS OAM | for MPLS networks [ITU-T-Y1711] | | monitors.
| +--------------------------------------+---------------+
| | Assignment of the 'OAM Alert Label' | RFC 3429 |
| | for Multiprotocol Label Switching | |
| | Architecture (MPLS) Operation and | |
| | Maintenance (OAM) Functions | |
| | [OAM-Label] | |
| | | |
| | 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 ITU-T Y.1711. | |
+-----------+--------------------------------------+---------------+
|ITU-T | Operations, administration and |ITU-T G.8113.2 |
|MPLS-TP OAM| Maintenance mechanisms for MPLS-TP | |
| | networks using the tools defined for | |
| | MPLS [ITU-G8113.2] | |
| | | |
| | Note: this document describes the | |
| | OAM toolset defined by the IETF for | |
| | MPLS-TP, whereas ITU-T G.8113.1 | |
| | describes the OAM toolset defined | |
| | by the ITU-T. | |
| +--------------------------------------+---------------+
| | Operations, Administration and |ITU-T G.8113.1 |
| | Maintenance mechanism for MPLS-TP in | |
| | Packet Transport Network (PTN) | |
| +--------------------------------------+---------------+
| | Allocation of a Generic Associated | RFC 6671 |
| | Channel Type for ITU-T MPLS Transport| |
| | Profile Operation, Maintenance, and | |
| | Administration (MPLS-TP OAM) | |
| | [ITU-T-CT] | |
| | | |
| | 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 ITU-T G.8113.1. | |
+-----------+--------------------------------------+---------------+
|ITU-T | OAM Functions and Mechanisms for |[ITU-T-Y1731] |
|Ethernet | Ethernet-based Networks | |
|OAM | | |
+-----------+--------------------------------------+---------------+
|IEEE | Connectivity Fault Management | IEEE 802.1ag |
|CFM | [IEEE802.1ag] | |
| | | |
| | Note: CFM was originally published | |
| | as IEEE 802.1ag, but is now | |
| | incorporated in the 802.1Q standard.| |
+-----------+--------------------------------------+---------------+
|IEEE | Media Access Control Parameters, | IEEE 802.3ah |
|802.3 | Physical Layers, and Management | |
|link level | Parameters for Subscriber Access | |
|OAM | Networks [IEEE802.3ah] | |
| | | |
| | Note: link level OAM was originally | |
| | defined in IEEE 802.3ah, and is now | |
| | incorporated in the 802.3 standard. | |
+-----------+--------------------------------------+---------------+
Table 2 Non-IETF OAM Standards Mentioned in this Document
2. Basic Terminology 2. Terminology
2.1. Abbreviations 2.1. Abbreviations
ACH Associated Channel Header ACH Associated Channel Header
AIS Alarm Indication Signal AIS Alarm Indication Signal
ATM Asynchronous Transfer Mode
BFD Bidirectional Forwarding Detection BFD Bidirectional Forwarding Detection
CC Continuity Check CC Continuity Check
CV Connectivity Verification CV Connectivity Verification
DM Delay Measurement DM Delay Measurement
FEC Forwarding Equivalence Class FEC Forwarding Equivalence Class
G-ACh Generic Associated Channel
GAL Generic Associated Label GAL Generic Associated Label
ICMP Internet Control Message Protocol ICMP Internet Control Message Protocol
L2TP Layer Two Tunneling Protocol
LCCE L2TP Control Connection Endpoint
LDP Label Distribution Protocol LDP Label Distribution Protocol
LER Label Edge Router
LM Loss Measurement LM Loss Measurement
LSP Label Switched Path LSP Label Switched Path
LSR Label Switched Router
ME Maintenance Entity ME Maintenance Entity
MEG Maintenance Entity Group MEG Maintenance Entity Group
MEP MEG End Point MEP MEG End Point
MIP MEG Intermediate Point MIP MEG Intermediate Point
MP Maintenance Point MP Maintenance Point
skipping to change at page 13, line 4 skipping to change at page 7, line 39
MEG Maintenance Entity Group MEG Maintenance Entity Group
MEP MEG End Point MEP MEG End Point
MIP MEG Intermediate Point MIP MEG Intermediate Point
MP Maintenance Point MP Maintenance Point
MPLS Multiprotocol Label Switching MPLS Multiprotocol Label Switching
MPLS-TP MPLS Transport Profile MPLS-TP MPLS Transport Profile
MTU Maximum Transmission Unit MTU Maximum Transmission Unit
OAM Operations, Administration, and Maintenance OAM Operations, Administration, and Maintenance
PW Pseudowire PDH Plesiochronous Digital Hierarchy
PE Provider Edge
PW Pseudowire
PWE3 Pseudowire Emulation Edge-to-Edge PWE3 Pseudowire Emulation Edge-to-Edge
RBridge Routing Bridge
RDI Remote Defect Indication RDI Remote Defect Indication
SDH Synchronous Digital Hierarchy
SONET Synchronous Optical Networking
TRILL Transparent Interconnection of Lots of Links
TTL Time To Live TTL Time To Live
VCCV Virtual Circuit Connectivity Verification VCCV Virtual Circuit Connectivity Verification
2.2. Terminology used in OAM Standards 2.2. Terminology used in OAM Standards
2.2.1. General Terms 2.2.1. General Terms
A wide variety of terms is used in various OAM standards. Each of the A wide variety of terms is used in various OAM standards. This
OAM standards listed in the reference section includes a section that section presents a comparison of the terms used in various OAM
defines terms relevant to that tool. A thesaurus of terminology for standards, without fully quoting the definition of each term.
MPLS-TP terms is presented in [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 An interesting overview of the term OAM and its derivatives is
standards, without fully quoting the definition of each term. For a presented in [OAM-Def]. A thesaurus of terminology for MPLS-TP terms
formal definition of each term, refer to the references at the end of is presented in [TP-Term], and provides a good summary of some of the
this document. OAM related terminology.
2.2.2. OAM Maintenance Entities 2.2.2. Functions, Mechanisms, Tools and Protocols
OAM tools are designed to monitor and manage a Maintenance Entity OAM Function
(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]: OAM is a group of functions that provide network fault indication,
performance information, and data and diagnosis functions (based on
the definition of OAM in the ATM Forum Glossary).
o MEP: The two points that define a maintenance entity. This definition implies that OAM functions are the atomic building
blocks of OAM, where each function defines an OAM capability.
o MEG: The collection of one or more MEs that belongs to the same Typical examples of OAM functions are presented in Section 3.
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, OAM Protocol
called Maintenance Entity Group Intermediate Points (MIPs).
A pair of MEPs engaged in an ME are connected by a communication A protocol used for implementing one or more OAM functions.
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 The OWAMP-Test [OWAMP] is an example of an OAM protocol.
(e.g. [ITU-T-Y1731]), 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) OAM Mechanism
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 An OAM Mechanism, sometimes referred to as an OAM tool, is a
mechanism that implements one or more OAM functions.
A Maintenance Point (MP) is a functional entity that is defined at a In some cases an OAM protocol *is* an OAM mechanism, e.g., OWAMP-
node in the network, and either initiates or reacts to OAM messages. Test. In other cases an OAM mechanism uses a set of protocols that
A Maintenance End Point (MEP) is one of the end points of an ME, and are not strictly OAM-related; for example, Traceroute (Section 4.2.)
can initiate OAM messages and respond to them. A Maintenance can be implemented using UDP and ICMP messages, without using an OAM
Intermediate Point (MIP) is an intermediate point between two MEPs, protocol per se.
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. The terms tool and mechanism are used interchangeably in this
An MP is a bridge interface, that is monitored by an OAM protocol document.
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 2.2.3. Data Plane, Control Plane and Management Plane
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 Data Plane
The Data Plane is typically described as the hardware and software
components responsible for receiving a packet, performing lookups to
identify the packet's destination and possible actions that need to
be performed on the packet, and forwarding the packet out through the
appropriate outgoing interface (based on [Cont]).
The Data Plane is also known as the Forwarding Plane or the User
Plane.
Control Plane
The Control Plane, as described in [Cont], is generally described as
the hardware and software components for handling packets destined to
the device itself as well as building and sending packets originated
locally on the device.
Management Plane
This term Management Plane, as described in [Mgmt], is used to
describe the exchange of management messages through management
protocols (often transported by IP and by IP transport protocols)
between management applications and the managed entities such as
network nodes.
Data Plane vs. Control Plane vs. Management Plane
The distinction between the planes is at times a bit vague. For
example, the definition of "Control Plane" above may imply that OAM
tools such as ping, BFD and others are in fact in the control plane.
This document focuses on data plane OAM tools, i.e., tools used for
monitoring the data plane. While these tools could arguably be
considered to be in the control plane, these tools monitor the data
plane, and hence it is imperative to have fate-sharing between OAM
traffic and the data plane traffic it monitors.
Another potentially vague distinction is between the management plane
and control plane. The management plane should be seen as separate
from, but possibly overlapping with, the control plane (based on
[Mgmt]).
2.2.4. The Players
An OAM mechanism is used between two (or more) "players". Various
terms are used in IETF documents to refer to the players that take
part in OAM. Table 2 summarizes the terms used in each of the
categories discussed in this document.
+--------------------------+--------------------------+
| Category | Terms |
+--------------------------+--------------------------+
| Ping / Traceroute |-Host |
| ([ICMPv4], [ICMPv6], |-Node |
| [TCPIP-Tools]) |-Interface |
| |-Gateway |
+ ------------------------ + ------------------------ +
| BFD [BFD] | System |
+ ------------------------ + ------------------------ +
| MPLS OAM [MPLS-OAM-FW] | LSR |
+ ------------------------ + ------------------------ +
| MPLS-TP OAM [TP-OAM-FW] |-End Point - MEP |
| |-Intermediate Point - MIP |
+ ------------------------ + ------------------------ +
| Pseudowire OAM [VCCV] |-PE |
| |-LCCE |
+ ------------------------ + ------------------------ +
| OWAMP and TWAMP |-Host |
| ([OWAMP], [TWAMP]) |-End system |
+ ------------------------ + ------------------------ +
| TRILL OAM [TRILL-OAM] |-RBridge |
+--------------------------+--------------------------+
Table 2 Maintenance Point Terminology
2.2.5. Proactive and On-demand Activation
The different OAM tools may be used in one of two basic types of The different OAM tools may be used in one of two basic types of
activation: activation:
o Proactive activation - indicates that the tool is activated on a Proactive
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.
o On-demand activation - indicates that the tool is activated Proactive activation - indicates that the tool is activated on a
"manually" to detect a specific anomaly. In this activation a continual basis, where messages are sent periodically, and errors are
small number of OAM messages are sent by a MEP and the reply detected when a certain number of expected messages are not received.
message is received.
2.2.5. Connectivity Verification and Continuity Checks On-demand
On-demand activation - indicates that the tool is activated
"manually" to detect a specific anomaly.
2.2.6. Connectivity Verification and Continuity Checks
Two distinct classes of failure management functions are used in OAM Two distinct classes of failure management functions are used in OAM
protocols, connectivity verification and continuity checks. The protocols, connectivity verification and continuity checks. The
distinction between these terms is defined in [MPLS-TP-OAM], and is distinction between these terms is defined in [MPLS-TP-OAM], and is
used similarly in this document. used similarly in this document.
Continuity checks are used to verify the liveness of a connection or Continuity Check
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 Continuity checks are used to verify that a destination is reachable,
is connected to a peer MP or not. This function also allows the MP to and are typically sent proactively, though they can be invoked on-
verify that messages from the peer MP are received through the demand as well.
correct path, thereby verifying not only that the two MPs are
connected, but also that they are connected through the expected Connectivity Verification
path. This allows detection of unexpected topology changes. A
connectivity verification (CV) protocol typically uses a CV message, A connectivity verification function allows Alice to check whether
followed by a CV reply that is sent back to the originator. A CV she is connected to Bob or not. This function also allows Alice to
function can be applied proactively or on-demand. verify that messages from Bob 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, allowing detection
of unexpected topology changes. It is noted that while the CV
function is performed in the data plane, the "expected path" is
predetermined either in the control plane or in the management plane.
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 Connectivity verification and continuity checks are considered
complementary mechanisms, and are often used in conjunction with each complementary mechanisms, and are often used in conjunction with each
other. other.
2.2.6. Failures 2.2.7. Failures
The terms Failure, Fault, and Defect are used interchangeably in the The terms Failure, Fault, and Defect are used interchangeably in the
standards, referring to a malfunction that can be detected by a standards, referring to a malfunction that can be detected by a
connectivity or a continuity check. In some standards, such as connectivity or a continuity check. In some standards, such as
[IEEE802.1ag], there is no distinction between these terms, while in 802.1ag [IEEE802.1Q] , there is no distinction between these terms,
other standards each of these terms refers to a different type of while in other standards each of these terms refers to a different
malfunction. type of malfunction.
The terminology used in IETF MPLS-TP OAM takes after the ITU-T, which 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 distinguishes between these terms in [ITU-T-G.806];
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 Fault
3.1. IP Ping and Traceroute The term Fault refers to an inability to perform a required action,
e.g., an unsuccessful attempt to deliver a packet.
3.1.1. Ping Defect
The term Defect refers to an interruption in the normal operation,
such as a consecutive period of time where no packets are delivered
successfully.
Failure
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 Functions
This subsection provides a brief summary of the common OAM functions
used in OAM-related standards. These functions are used as building
blocks in the OAM standards described in this document.
o Connectivity Verification (CV) and/or Continuity Checks (CC):
As defined in Section 2.2.6.
o Path Discovery / Fault Localization:
This mechanism can be used to trace the route to a destination,
i.e., to identify the nodes along the route to the destination.
When more than one route is available to a specific destination,
this mechanism traces one of the available routes. When a failure
occurs, this mechanism also allows to detect the location of the
failure.
Note that the term route tracing (or Traceroute) that is used in
the context of IP and MPLS, is sometimes referred to as path
tracing in other transport technologies, such as TRILL.
o Performance Monitoring:
Typically refers to:
o Loss Measurement (LM) - monitors the packet loss rate.
o Delay Measurement (DM) - monitors the delay and delay
variation.
4. OAM Mechanisms in the IETF - a Detailed Description
This section presents a detailed description of the sets of OAM-
related mechanisms in each of the categories in Table 1.
4.1. IP Ping
Ping is a common network diagnosis application for IP networks that Ping is a common network diagnosis application for IP networks that
uses ICMP. The ICMP Echo request/reply exchange is a connectivity uses ICMP. 'Ping' is an abbreviation for Packet internet groper
verification function for the Internet Protocol. The originator [NetTerms]. As defined in [NetTerms], it is a program used to test
transmits an ICMP Echo request packet, and the receiver replies with reachability of destinations by sending them an ICMP echo request and
an Echo reply. ICMP ping is defined in two variants, [ICMPv4] is used waiting for a reply.
for IPv4, and [ICMPv6] is used for IPv6.
3.1.2. Traceroute The ICMP Echo request/reply exchange in Ping is used as a continuity
check 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.
Ping implementations typically use ICMP messages. UDP Ping is a
variant that uses UDP messages instead of ICMP echo messages.
Ping is a single-ended continuity check, i.e., it allows the
*initiator* of the Echo request to test the reachability. If it is
desirable for both ends to test the reachability, both ends have to
invoke Ping independently.
Note that since ICMP filtering is deployed in some routers and
firewalls, the usefulness of Ping is sometimes limited in the wider
internet. This limitation is equally relevant to Traceroute.
4.2. IP Traceroute
Traceroute ([TCPIP-Tools], [NetTools]) is an application that allows Traceroute ([TCPIP-Tools], [NetTools]) is an application that allows
users to discover the path between an IP source and an IP users to discover a path between an IP source and an IP destination.
destination. Traceroute sends a sequence of UDP packets to UDP port
33434 at the destination. By default, Traceroute begins by sending
three packets (the number of packets is configurable in most
Traceroute implementations), each with an IP Time-To-Live (TTL) value
of one to the destination. 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 The most common way to implement Traceroute [TCPIP-Tools] is
path between a source and destination, it may not reveal the reverse described as follows. Traceroute sends a sequence of UDP packets to
UDP port 33434 at the destination. By default, Traceroute begins by
sending three packets (the number of packets is configurable in most
Traceroute implementations), each with an IP Time-To-Live (or Hop
Limit in IPv6) value of one to the destination. These packets expire
as soon as they reach the first router in the path. Consequently,
that router sends three ICMP Time Exceeded Messages back 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.
It is noted that Traceroute is an application, and not a protocol. As
such, it has various different implementations. One of the most
common ones uses UDP probe packets, as described above. Other
implementations exist that use other types of probe messages, such as
ICMP or TCP.
Note that IP routing may be asymmetric. While Traceroute discovers a
path between a source and destination, it does not reveal the reverse
path. path.
A few ICMP extensions ([ICMP-Ext], [ICMP-MP], [ICMP-Int]) have been A few ICMP extensions ([ICMP-MP], [ICMP-Int]) have been defined in
defined in the context of Traceroute. These extensions augment the the context of Traceroute. These documents define several extensions,
ICMP Destination Unreachable message, and can be used by Traceroute including extensions to the ICMP Destination Unreachable message,
applications. that can be used by Traceroute applications.
3.2. Bidirectional Forwarding Detection (BFD) 4.3. Bidirectional Forwarding Detection (BFD)
3.2.1. Overview 4.3.1. Overview
While multiple OAM mechanisms have been defined for various protocols While multiple OAM mechanisms have been defined for various protocols
in the protocol stack, Bidirectional Forwarding Detection [BFD], in the protocol stack, Bidirectional Forwarding Detection [BFD],
defined by the IETF BFD working group, is a generic OAM mechanism defined by the IETF BFD working group, is a generic OAM mechanism
that can be deployed over various encapsulating protocols, and in that can be deployed over various encapsulating protocols, and in
various medium types. The IETF has defined variants of the protocol 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 for IP ([BFD-IP], [BFD-Multi]), for MPLS LSPs [BFD-LSP], and for
[BFD-VCCV]. The usage of BFD in MPLS-TP is defined in [MPLS-TP-CC- pseudowires [BFD-VCCV]. The usage of BFD in MPLS-TP is defined in
CV]. [TP-CC-CV].
BFD includes two main OAM functions, using two types of BFD packets: BFD includes two main OAM functions, using two types of BFD packets:
BFD Control packets, and BFD Echo packets. BFD Control packets, and BFD Echo packets.
3.2.2. BFD Control 4.3.2. Terminology
BFD operates between two *systems*. The BFD protocol is run between
two systems after establishing a *session*.
4.3.3. BFD Control
BFD supports a bidirectional continuity check, using BFD control BFD supports a bidirectional continuity check, using BFD control
packets, that are exchanged within a BFD session. BFD sessions packets, that are exchanged within a BFD session. BFD sessions
operate in one of two modes: operate in one of two modes:
o Asynchronous mode (i.e. proactive): in this mode BFD control o Asynchronous mode (i.e. proactive): in this mode BFD control
packets are sent periodically. When the receiver detects that no packets are sent periodically. When the receiver detects that no
BFD control packet have been received during a predetermined BFD control packets have been received during a predetermined
period of time, a failure is detected. period of time, a failure is detected.
o Demand mode: in this mode, BFD control packets are sent on-demand. 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 Upon need, a system initiates a series of BFD control packets to
verify the liveness of the session. BFD control packets are sent check the continuity of the session. BFD control packets are sent
independently in each direction. independently in each direction.
Each of the end-points of the monitored path maintains its own Each of the end-points (referred to as systems) of the monitored path
session identification, called a Discriminator, both of which are maintains its own session identification, called a Discriminator,
included in the BFD Control Packets that are exchanged between the both of which are included in the BFD Control Packets that are
end-points. At the time of session establishment, the Discriminators exchanged between the end-points. At the time of session
are exchanged between the two-end points. In addition, the establishment, the Discriminators are exchanged between the two-end
transmission (and reception) rate is negotiated between the two end- points. In addition, the transmission (and reception) rate is
points, based on information included in the control packets. These negotiated between the two end-points, based on information included
transmission rates may be renegotiated during the session. in the control packets. These transmission rates may be renegotiated
during the session.
During normal operation of the session, i.e. no failures are During normal operation of the session, i.e. no failures are
detected, the BFD session is in the Up state. If no BFD Control detected, the BFD session is in the Up state. If no BFD Control
packets are received during a fixed period of time, called the packets are received during a period of time called the Detection
Detection Time, the session is declared to be Down. The detection Time, the session is declared to be Down. The detection time is a
time is a function of the negotiated transmission time, and a function of the pre-configured or negotiated transmission time, and a
parameter called Detect Mult. Detect Mult determines the number of parameter called Detect Mult. Detect Mult determines the number of
missing BFD Control packets that cause the session to be declared as missing BFD Control packets that cause the session to be declared as
Down. This parameter is included in the BFD Control packet. Down. This parameter is included in the BFD Control packet.
3.2.3. BFD Echo 4.3.4. BFD Echo
A BFD echo packet is sent to a peer system, and is looped back to the 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. originator. The echo function can be used proactively, or on-demand.
The BFD echo function has been defined in BFD for IPv4 and IPv6 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 ([BFD-IP]), but is not used in BFD for MPLS LSPs, PWs, or in BFD for
MPLS-TP. MPLS-TP.
3.3. MPLS OAM 4.4. MPLS OAM
The IETF MPLS working group has defined OAM for MPLS LSPs. The The IETF MPLS working group has defined OAM for MPLS LSPs. The
requirements and framework of this effort are defined in [MPLS-OAM- requirements and framework of this effort are defined in
FW] and [MPLS-OAM], respectively. The corresponding OAM mechanism [MPLS-OAM-FW] and [MPLS-OAM], respectively. The corresponding OAM
defined, in this context, is LSP Ping [LSP-Ping]. mechanism defined, in this context, is LSP Ping [LSP-Ping].
LSP Ping is based on ICMP Ping and just like its predecessor may be LSP Ping is modeled after the Ping/Traceroute paradigm and thus it
used in one of two modes: may be used in one of two modes:
o "Ping" mode: In this mode LSP ping is used for end-to-end o "Ping" mode: In this mode LSP Ping is used for end-to-end
connectivity verification between two LERs. connectivity verification between two LERs.
o "Traceroute" mode: This mode is used for hop-by-hop fault o "Traceroute" mode: This mode is used for hop-by-hop fault
isolation. isolation.
LSP Ping extends the basic ICMP Ping operation (of data-plane LSP Ping extends the basic ICMP Ping operation (of data-plane
connectivity verification) with functionality to verify data-plane connectivity verification) with functionality to verify data-plane
vs. control-plane consistency for a Forwarding Equivalence Class vs. control-plane consistency for a Forwarding Equivalence Class
(FEC) and also Maximum Transmission Unit (MTU) problems. The (FEC) and also Maximum Transmission Unit (MTU) problems. The
traceroute functionality may be used to isolate and localize the MPLS Traceroute functionality may be used to isolate and localize the MPLS
faults, using the Time-to-live (TTL) indicator to incrementally faults, using the Time-to-live (TTL) indicator to incrementally
identify the sub-path of the LSP that is successfully traversed identify the sub-path of the LSP that is successfully traversed
before the faulty link or node. before the faulty link or node.
It should be noted that LSP Ping supports unique identification of It should be noted that LSP Ping supports unique identification of
the LSP within an addressing domain. The identification is checked the LSP within an addressing domain. The identification is checked
using the full FEC identification. LSP Ping is easily extensible to using the full FEC identification. LSP Ping is easily extensible to
include additional information needed to support new functionality, include additional information needed to support new functionality,
by use of Type-Length-Value (TLV) constructs. The usage of TLVs is by use of Type-Length-Value (TLV) constructs. The usage of TLVs is
typically not easy to perform in hardware, and is thus typically typically not easy to perform in hardware, and is thus typically
handled by the control plane. handled by the control plane.
LSP Ping supports both asynchronous, as well as, on-demand LSP Ping supports both asynchronous, as well as, on-demand
activation. activation.
3.4. MPLS-TP OAM 4.5. MPLS-TP OAM
3.4.1. Overview 4.5.1. Overview
The MPLS working group is currently working on defining the OAM The MPLS working group has defined the OAM toolset that fulfills the
toolset that fulfills the requirements for MPLS-TP OAM. The full set requirements for MPLS-TP OAM. The full set of requirements for MPLS-
of requirements for MPLS-TP OAM are defined in [MPLS-TP-OAM], and TP OAM are defined in [MPLS-TP-OAM], and include both general
include both general requirements for the behavior of the OAM requirements for the behavior of the OAM mechanisms and a set of
mechanisms and a set of operations that should be supported by the operations that should be supported by the OAM toolset. The set of
OAM toolset. The set of mechanisms required are further elaborated mechanisms required are further elaborated in [TP-OAM-FW], which
in [TP-OAM-FW], which describes the general architecture of the OAM describes the general architecture of the OAM system as well as
system as well as giving overviews of the functionality of the OAM giving overviews of the functionality of the OAM toolset.
toolset.
Some of the basic requirements for the OAM toolset for MPLS-TP are: 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 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 based environment. If the network is IP based, i.e. IP routing and
forwarding are available, then the MPLS-TP OAM toolset should rely forwarding are available, then the MPLS-TP OAM toolset should rely
on the IP routing and forwarding capabilities. On the other hand, on the IP routing and forwarding capabilities. On the other hand,
in environments where IP functionality is not available, the OAM in environments where IP functionality is not available, the OAM
tools must still be able to operate without dependence on IP tools must still be able to operate without dependence on IP
forwarding and routing. forwarding and routing.
o OAM packets and the user traffic are required to be congruent 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 (i.e. OAM packets are transmitted in-band) and there is a need to
differentiate OAM packets from user-plane ones. Inherent in this differentiate OAM packets from data plane ones. Inherent in this
requirement is the principle that MPLS-TP OAM be independent of requirement is the principle that MPLS-TP OAM be independent of
any existing control-plane, although it should not preclude use of any existing control-plane, although it should not preclude use of
the control-plane functionality. the control-plane functionality.
3.4.2. Generic Associated Channel 4.5.2. Terminology
Maintenance Entity (ME)
The MPLS-TP 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 term Maintenance Entity (ME) is used in ITU-T Recommendations
(e.g. [ITU-T-Y1731]), as well as in the MPLS-TP terminology
([TP-OAM-FW]).
Maintenance Entity Group (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 (based on [TP-OAM-FW]).
Maintenance Point (MP)
A Maintenance Point (MP) is a functional entity that is defined at a
node in the network, and can initiate and/or react to OAM messages.
This document focuses on the data-plane functionality of MPs, while
MPs interact with the control plane and with the management plane as
well.
The term MP is used in IEEE 802.1ag, and was similarly adopted in
MPLS-TP ([TP-OAM-FW]).
Maintenance End Point (MEP)
A Maintenance End Point (MEP) is one of the end points of an ME, and
can initiate OAM messages and respond to them (based on [TP-OAM-FW]).
Maintenance Intermediate Point (MIP)
In between MEPs, there are zero or more intermediate points, called
Maintenance Entity Group Intermediate Points (based on [TP-OAM-FW]).
A Maintenance Intermediate Point (MIP) is an intermediate point 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.
Up and Down MEPs
The IEEE 802.1ag [IEEE802.1Q] defines a distinction between Up MEPs
and Down MEPs. A MEP 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 MEP is a MEP that receives OAM
packets from, and transmits them to the direction of the network. An
Up MEP 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 MEP - either at the ingress,
egress, or forwarding function of the node (Down / Up MEPs). This
placement is important for localization of a failure.
The distinction between Up and Down MEPs was defined in [TP-OAM-FW],
but has not been used in other MPLS-TP RFCs, as of the writing of
this document.
4.5.3. Generic Associated Channel
In order to address the requirement for in-band transmission of MPLS- In order to address the requirement for in-band transmission of MPLS-
TP OAM traffic, MPLS-TP uses a Generic Associated Channel (G-ACh), 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 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, on the same concepts as the PWE3 ACH and VCCV mechanisms. However,
to address the needs of LSPs as differentiated from PW, the following to address the needs of LSPs as differentiated from PW, the following
concepts were defined for [G-ACh]: concepts were defined for [G-ACh]:
o An Associated Channel Header (ACH), that uses a format similar to 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 the PW Control Word, is a 4-byte header that is prepended to OAM
packets. packets.
o A Generic Associated Label (GAL). The GAL is a reserved MPLS label 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 value (13) that indicates that the packet is an ACH packet and the
payload follows immediately after the label stack. payload follows immediately after the label stack.
3.4.3. MPLS-TP OAM Toolset It should be noted that while the G-ACh was defined as part of the
MPLS-TP definition effort, the G-ACh is a generic tool that can be
used in MPLS in general, and not only in MPLS-TP.
4.5.4. MPLS-TP OAM Toolset
To address the functionality that is required of the OAM toolset, the 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 MPLS WG conducted an analysis of the existing IETF and ITU-T OAM
mechanisms and their ability to fulfill the required functionality. mechanisms and their ability to fulfill the required functionality.
The conclusions of this analysis are documented in [OAM-Analys]. The The conclusions of this analysis are documented in [OAM-Analys]. The
MPLS working group currently plans to use a mixture of OAM mechanisms MPLS working group currently plans to use a mixture of OAM mechanisms
that are based on various existing standards, and adapt them to the that are based on various existing standards, and adapt them to the
requirements of [MPLS-TP-OAM]. Some of the main building blocks of requirements of [MPLS-TP-OAM]. Some of the main building blocks of
this solution are based on: this solution are based on:
skipping to change at page 20, line 42 skipping to change at page 20, line 14
o New protocol packets, using G-ACH, to address different o New protocol packets, using G-ACH, to address different
functionality. functionality.
o Performance measurement protocols that are based on the o Performance measurement protocols that are based on the
functionality that is described in [ITU-T-Y1731]. functionality that is described in [ITU-T-Y1731].
The following sub-sections describe the OAM tools defined for MPLS-TP The following sub-sections describe the OAM tools defined for MPLS-TP
as described in [TP-OAM-FW]. as described in [TP-OAM-FW].
3.4.3.1. Continuity Check and Connectivity Verification 4.5.4.1. Continuity Check and Connectivity Verification
Continuity Check and Connectivity Verification are presented in Continuity Check and Connectivity Verification are presented in
Section 2.2.5. of this document. As presented there, these tools may Section 2.2.6. of this document. As presented there, these tools may
be used either proactively or on-demand. When using these tools be used either proactively or on-demand. When using these tools
proactively, they are generally used in tandem. proactively, they are generally used in tandem.
For MPLS-TP there are two distinct tools, the proactive tool is For MPLS-TP there are two distinct tools, the proactive tool is
defined in [TP-CC-CV] while the on-demand tool is defined in defined in [TP-CC-CV] while the on-demand tool is defined in
[OnDemand-CV]. In on-demand mode, this function should support
[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. monitoring between the MEPs and, in addition, between a MEP and MIP.
[TP-OAM-FW] highlights, when performing Connectivity Verification, [TP-OAM-FW] highlights, when performing Connectivity Verification,
the need for the CC-V messages to include unique identification of the need for the CC-V messages to include unique identification of
the MEG that is being monitored and the MEP that originated the the MEG that is being monitored and the MEP that originated the
message. message.
The proactive tool [TP-CC-CV] is based on extensions to BFD (see The proactive tool [TP-CC-CV] is based on extensions to BFD (see
Section 3.2. ) with the additional limitation that the transmission Section 4.3.) with the additional limitation that the transmission
and receiving rates are based on configuration by the operator. The and receiving rates are based on configuration by the operator. The
on-demand tool [OnDemand-CV] is an adaptation of LSP Ping (see on-demand tool [OnDemand-CV] is an adaptation of LSP Ping (see
Section 3.3. ) for the required behavior of MPLS-TP. Section 4.4.) for the required behavior of MPLS-TP.
3.4.3.2. Route Tracing 4.5.4.2. Route Tracing
[MPLS-TP-OAM] defines that there is a need for functionality that [MPLS-TP-OAM] defines that there is a need for functionality that
would allow a path end-point to identify the intermediate and end- 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. points of the path. This function would be used in on-demand mode.
Normally, this path will be used for bidirectional PW, LSP, and Normally, this path will be used for bidirectional PW, LSP, and
sections, however, unidirectional paths may be supported only if a sections, however, unidirectional paths may be supported only if a
return path exists. The tool for this is based on the LSP Ping (see return path exists. The tool for this is based on the LSP Ping (see
Section 3.3. ) functionality and is described in [OnDemand-CV]. Section 4.4.) functionality and is described in [OnDemand-CV].
3.4.3.3. Lock Instruct 4.5.4.3. Lock Instruct
The Lock Instruct function [Lock-Loop] is used to notify a transport The Lock Instruct function [Lock-Loop] is used to notify a transport
path end-point of an administrative need to disable the transport path end-point of an administrative need to disable the transport
path. This functionality will generally be used in conjunction with path. This functionality will generally be used in conjunction with
some intrusive OAM function, e.g. Performance measurement, Diagnostic some intrusive OAM function, e.g. Performance measurement, Diagnostic
testing, to minimize the side-effect on user data traffic. testing, to minimize the side-effect on user data traffic.
3.4.3.4. Lock Reporting 4.5.4.4. Lock Reporting
Lock Reporting is a function used by an end-point of a path to report 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 to its far-end end-point that a lock condition has been affected on
the path. the path.
3.4.3.5. Alarm Reporting 4.5.4.5. Alarm Reporting
Alarm Reporting is a function used by an intermediate point of a Alarm Reporting [TP-Fault] provides the means to suppress alarms
path, that becomes aware of a fault on the path, to report to the following detection of defect conditions at the server sub-layer.
end-points of the path. [TP-OAM-FW] states that this may occur as a Alarm reporting is used by an intermediate point of a path, that
result of a defect condition discovered at a server sub-layer. This becomes aware of a fault on the path, to report to the end-points of
generates an Alarm Indication Signal (AIS) that continues until the the path. [TP-OAM-FW] states that this may occur as a result of a
fault is cleared. The consequent action of this function is detailed defect condition discovered at a server sub-layer. This generates an
in [TP-OAM-FW]. Alarm Indication Signal (AIS) that continues until the fault is
cleared. The consequent action of this function is detailed in
[TP-OAM-FW].
3.4.3.6. Remote Defect Indication 4.5.4.6. Remote Defect Indication
Remote Defect Indication (RDI) is used proactively by a path end- 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 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 bidirectional connection between them. [MPLS-TP-OAM] points out that
this function may be applied to a unidirectional LSP only if there a 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 return path exists. [TP-OAM-FW] points out that this function is
associated with the proactive CC-V function. associated with the proactive CC-V function.
3.4.3.7. Client Failure Indication 4.5.4.7. Client Failure Indication
Client Failure Indication (CFI) is defined in [MPLS-TP-OAM] to allow Client Failure Indication (CFI) is defined in [MPLS-TP-OAM] to allow
the propagation information from one edge of the network to the the propagation information from one edge of the network to the
other. The information concerns a defect to a client, in the case other. The information concerns a defect to a client, in the case
that the client does not support alarm notification. that the client does not support alarm notification.
3.4.3.8. Packet Loss Measurement (LM) 4.5.4.8. Performance Monitoring
The definition of MPLS performance monitoring was motivated by the
MPLS-TP requirements [MPLS-TP-OAM], but was defined generically for
MPLS in [MPLS-LM-DM]. An additional document [TP-LM-DM] defines a
performance monitoring profile for MPLS-TP.
4.5.4.8.1. Packet Loss Measurement (LM)
Packet Loss Measurement is a function used to verify the quality of Packet Loss Measurement is a function used to verify the quality of
the service. This function indicates the ratio of packets that are the service. Packet loss, as defined in [IPPM-1LM] and [MPLS-TP-OAM],
not delivered out of all packets that are transmitted by the path indicates the ratio of the number of user packets lost to the total
source. number of user packets sent during a defined time interval.
There are two possible ways of determining this measurement: There are two possible ways of determining this measurement:
o Using OAM packets, it is possible to compute the statistics based o Using OAM packets, it is possible to compute the statistics based
on a series of OAM packets. This, however, has the disadvantage of on a series of OAM packets. This, however, has the disadvantage of
being artificial, and may not be representative since part of the being artificial, and may not be representative since part of the
packet loss may be dependent upon packet sizes. packet loss may be dependent upon packet sizes and upon the
implementation of the MEPs that take part in the protocol.
o Sending delimiting messages for the start and end of a measurement o Sending delimiting messages for the start and end of a measurement
period during which the source and sink of the path count the period during which the source and sink of the path count the
packets transmitted and received. After the end delimiter, the packets transmitted and received. After the end delimiter, the
ratio would be calculated by the path OAM entity. ratio would be calculated by the path OAM entity.
3.4.3.9. Packet Delay Measurement (DM) 4.5.4.8.2. Packet Delay Measurement (DM)
Packet Delay Measurement is a function that is used to measure one- 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 way or two-way delay of a packet transmission between a pair of the
end-points of a path (PW, LSP, or Section). Where: end-points of a path (PW, LSP, or Section). Where:
o One-way packet delay is the time elapsed from the start of o One-way packet delay, as defined in [IPPM-1DM], is the time
transmission of the first bit of the packet by a source node until elapsed from the start of transmission of the first bit of the
the reception of the last bit of that packet by the destination packet by a source node until the reception of the last bit of
node. that packet by the destination node.
o Two-way packet delay is the time elapsed from the start of o Two-way packet delay, as defined in [IPPM-2DM], is the time
transmission of the first bit of the packet by a source node until elapsed from the start of transmission of the first bit of the
the reception of the last bit of the loop-backed packet by the packet by a source node until the reception of the last bit of the
same source node, when the loopback is performed at the packet's loop-backed packet by the same source node, when the loopback is
destination node. performed at the packet's destination node.
Similarly to the packet loss measurement this could be performed in For each of these two metrics, the DM function allows the MEP to
either of the two ways outlined above. measure the delay, as well as the delay variation. Delay measurement
is performed by exchanging timestamped OAM packets between the
participating MEPs.
3.5. PWE3 OAM 4.6. Pseudowire OAM
3.5.1. PWE3 OAM using Virtual Circuit Connectivity Verification (VCCV) 4.6.1. Pseudowire OAM using Virtual Circuit Connectivity Verification
(VCCV)
VCCV, as defined in [VCCV], provides a means for end-to-end fault VCCV, as defined in [VCCV], provides a means for end-to-end fault
detection and diagnostics tools to be extended for PWs (regardless of detection and diagnostics tools to be extended for PWs (regardless of
the underlying tunneling technology). The VCCV switching function the underlying tunneling technology). The VCCV switching function
provides a control channel associated with each PW (based on the PW provides a control channel associated with each PW. [VCCV] defines
Associated Channel Header (ACH) which is defined in [PW-ACH]), and three Control Channel (CC) types, i.e., three possible methods for
allows transmitting the OAM packets in-band with PW data (using CC transmitting and identifying OAM messages:
Type 1: In-band VCCV).
o CC Type 1: In-band VCCV, as described in [VCCV], is also referred
to as "PWE3 Control Word with 0001b as first nibble". It uses the
PW Associated Channel Header [PW-ACH].
o CC Type 2: Out-of-band VCCV [VCCV], is also referred to as "MPLS
Router Alert Label". In this case the control channel is created
by using the MPLS router alert label [RFC3032] immediately above
the PW label.
o CC Type 3: TTL expiry VCCV [VCCV], is also referred to as "MPLS PW
Label with TTL == 1", i.e., the control channel is identified when
the value of the TTL field in the PW label is set to 1.
VCCV currently supports the following OAM mechanisms: ICMP Ping, LSP VCCV currently supports the following OAM mechanisms: ICMP Ping, LSP
Ping, and BFD. ICMP and LSP Ping are IP encapsulated before being Ping, and BFD. ICMP and LSP Ping are IP encapsulated before being
sent over the PW ACH. BFD for VCCV [BFD-VCCV] supports two modes of sent over the PW ACH. BFD for VCCV [BFD-VCCV] supports two modes of
encapsulation - either IP/UDP encapsulated (with IP/UDP header) or encapsulation - either IP/UDP encapsulated (with IP/UDP header) or
PW-ACH encapsulated (with no IP/UDP header) and provides support to PW-ACH encapsulated (with no IP/UDP header) and provides support to
signal the AC status. The use of the VCCV control channel provides signal the AC status. The use of the VCCV control channel provides
the context, based on the MPLS-PW label, required to bind and the context, based on the MPLS-PW label, required to bind and
bootstrap the BFD session to a particular pseudo wire (FEC), bootstrap the BFD session to a particular pseudo wire (FEC),
eliminating the need to exchange Discriminator values. eliminating the need to exchange Discriminator values.
VCCV consists of two components: (1) signaled component to VCCV consists of two components: (1) signaled component to
communicate VCCV capabilities as part of VC label, and (2) switching communicate VCCV capabilities as part of VC label, and (2) switching
component to cause the PW payload to be treated as a control packet. 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. VCCV is not directly dependent upon the presence of a control plane.
The VCCV capability negotiation may be performed as part of the PW The VCCV capability negotiation may be performed as part of the PW
signaling when LDP is used. In case of manual configuration of the signaling when LDP is used. In case of manual configuration of the
PW, it is the responsibility of the operator to set consistent PW, it is the responsibility of the operator to set consistent
options at both ends. options at both ends. The manual option was created specifically to
handle MPLS-TP use cases where no control plane was a requirement.
However, new use cases such as pure mobile backhaul find this
functionality useful too.
3.5.2. PWE3 OAM using G-ACh 4.6.2. Pseudowire OAM using G-ACh
As mentioned above, VCCV enables OAM for PWs by using a control As mentioned above, VCCV enables OAM for PWs by using a control
channel for OAM packets. When PWs are used in MPLS-TP networks, channel for OAM packets. When PWs are used in MPLS-TP networks,
rather than the control channels defined in VCCV, the G-ACh can be rather than the control channels defined in VCCV, the G-ACh can be
used as an alternative control channel. The usage of the G-ACh for used as an alternative control channel. The usage of the G-ACh for
PWs is defined in [PW-G-ACh]. PWs is defined in [PW-G-ACh].
3.6. OWAMP and TWAMP 4.6.3. Attachment Circuit - Pseudowire Mapping
3.6.1. Overview The PWE3 working group has defined a mapping and notification of
defect states between a pseudowire (PW) and the Attachment Circuits
(ACs) of the end-to-end emulated service. This mapping is of key
importance to the end-to-end functionality. Specifically, the mapping
is provided by [PW-MAP], by [L2TP-EC] for L2TPv3 pseudowires, and
Section 5.3 of [ATM-L2] for ATM.
4.7. OWAMP and TWAMP
4.7.1. Overview
The IPPM working group in the IETF defines common criteria and The IPPM working group in the IETF defines common criteria and
metrics for measuring performance of IP traffic ([IPPM-FW]). Some of metrics for measuring performance of IP traffic ([IPPM-FW]). Some of
the key RFCs published by this working group have defined metrics for the key RFCs published by this working group have defined metrics for
measuring connectivity [IPPM-Con], delay ([IPPM-1DM], [IPPM-2DM]), measuring connectivity [IPPM-Con], delay ([IPPM-1DM], [IPPM-2DM]),
and packet loss [IPPM-1LM]. and packet loss [IPPM-1LM]. It should be noted that the work of the
IETF in the context of performance metrics is not limited to IP
Alternative protocols for performance measurement are defined, for networks; [PM-CONS] presents general guidelines for considering new
example, in MPLS-TP OAM ([MPLS-LM-DM], [TP-LM-DM]), and in Ethernet performance metrics.
OAM [ITU-T-Y1731].
The IPPM working group has defined not only metrics for performance The IPPM working group has defined not only metrics for performance
measurement, but also protocols that define how the measurement is measurement, but also protocols that define how the measurement is
carried out. The One-way Active Measurement Protocol [OWAMP] and the carried out. The One-way Active Measurement Protocol [OWAMP] and the
Two-Way Active Measurement Protocol [TWAMP] define a method and Two-Way Active Measurement Protocol [TWAMP] define a method and
protocol for measuring delay and packet loss in IP networks. protocol for measuring performance metrics in IP networks.
OWAMP [OWAMP] enables measurement of one-way characteristics of IP OWAMP [OWAMP] enables measurement of one-way characteristics of IP
networks, such as one-way packet loss and one-way delay. For its networks, such as one-way packet loss and one-way delay. For its
proper operation OWAMP requires accurate time of day setting at its proper operation OWAMP requires accurate time of day setting at its
end points. end points.
TWAMP [TWAMP] is a similar protocol that enables measurement of two- TWAMP [TWAMP] is a similar protocol that enables measurement of both
way (round trip) characteristics. TWAMP does not require accurate one-way and two-way (round trip) characteristics.
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, OWAMP and TWAMP are both comprised of two separate protocols:
and a Test plane protocol.
3.6.2. Control and Test Protocols o OWAMP-Control/TWAMP-Control: used to initiate, start, and stop
test sessions and to fetch their results. Continuity Check and
Connectivity Verification are tested and confirmed by establishing
the OWAMP/TWAMP Control Protocol TCP connection.
o OWAMP-Test/TWAMP-Test: used to exchange test packets between two
measurement nodes. Enables the loss and delay measurement
functions, as well as detection of other anomalies, such as packet
duplication and packet reordering.
It should be noted that while [OWAMP] and [TWAMP] define tools for
performance measurement, they do not define the accuracy of these
tools. The accuracy depends on scale, implementation and network
configurations.
Alternative protocols for performance monitoring are defined, for
example, in MPLS-TP OAM ([MPLS-LM-DM], [TP-LM-DM]), and in Ethernet
OAM [ITU-T-Y1731].
4.7.2. Control and Test Protocols
OWAMP and TWAMP control protocols run over TCP, while the test OWAMP and TWAMP control protocols run over TCP, while the test
protocols run over UDP. The purpose of the control protocols is to protocols run over UDP. The purpose of the control protocols is to
initiate, start, and stop test sessions, and for OWAMP to fetch initiate, start, and stop test sessions, and for OWAMP to fetch
results. The test protocols introduce test packets (which contain results. The test protocols introduce test packets (which contain
sequence numbers and timestamps) along the IP path under test sequence numbers and timestamps) along the IP path under test
according to a schedule, and record statistics of packet arrival. according to a schedule, and record statistics of packet arrival.
Multiple sessions may be simultaneously defined, each with a session Multiple sessions may be simultaneously defined, each with a session
identifier, and defining the number of packets to be sent, the amount 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, of padding to be added (and thus the packet size), the start time,
and the send schedule (which can be either a constant time between and the send schedule (which can be either a constant time between
test packets or exponentially distributed pseudo-random). Statistics test packets or exponentially distributed pseudo-random). Statistics
recorded conform to the relevant IPPM RFCs. recorded conform to the relevant IPPM RFCs.
OWAMP and TWAMP test traffic is designed with security in mind. Test OWAMP and TWAMP test traffic is designed with security in mind. Test
packets are hard to detect because they are simply UDP streams packets are hard to detect because they are simply UDP streams
between negotiated port numbers, with potentially nothing static in between negotiated port numbers, with potentially nothing static in
the packets. OWAMP and TWAMP also include optional authentication the packets. OWAMP and TWAMP also include optional authentication
and encryption for both control and test packets. and encryption for both control and test packets.
3.6.3. OWAMP 4.7.3. OWAMP
OWAMP defines the following logical roles: Session-Sender, Session- OWAMP defines the following logical roles: Session-Sender, Session-
Receiver, Server, Control-Client, and Fetch-Client. The Session- Receiver, Server, Control-Client, and Fetch-Client. The Session-
Sender originates test traffic that is received by the Session- Sender originates test traffic that is received by the Session-
Receiver. The Server configures and manages the session, as well as Receiver. The Server configures and manages the session, as well as
returning the results. The Control-Client initiates requests for returning the results. The Control-Client initiates requests for
test sessions, triggers their start, and may trigger their test sessions, triggers their start, and may trigger their
termination. The Fetch-Client requests the results of a completed termination. The Fetch-Client requests the results of a completed
session. Multiple roles may be combined in a single host - for session. Multiple roles may be combined in a single host - for
example, one host may play the roles of Control-Client, Fetch-Client, example, one host may play the roles of Control-Client, Fetch-Client,
skipping to change at page 26, line 5 skipping to change at page 26, line 26
describes a test session to which the Server responds with its describes a test session to which the Server responds with its
acceptance and supporting information. More than one test session acceptance and supporting information. More than one test session
may be requested with additional messages. The Control-Client then may be requested with additional messages. The Control-Client then
starts a test session and the Server acknowledges. The Session- starts a test session and the Server acknowledges. The Session-
Sender then sends test packets with pseudorandom padding to the Sender then sends test packets with pseudorandom padding to the
Session-Receiver until the session is complete or until the Control- Session-Receiver until the session is complete or until the Control-
client stops the session. Once finished, the Fetch-Client sends a client stops the session. Once finished, the Fetch-Client sends a
fetch request to the server, which responds with an acknowledgement fetch request to the server, which responds with an acknowledgement
and immediately thereafter the result data. and immediately thereafter the result data.
3.6.4. TWAMP 4.7.4. TWAMP
TWAMP defines the following logical roles: session-sender, session- TWAMP defines the following logical roles: session-sender, session-
reflector, server, and control-client. These are similar to the reflector, server, and control-client. These are similar to the
OWAMP roles, except that the Session-Reflector does not collect any OWAMP roles, except that the Session-Reflector does not collect any
packet information, and there is no need for a Fetch-Client. packet information, and there is no need for a Fetch-Client.
In a typical TWAMP session the Control-Client establishes a TCP In a typical TWAMP session the Control-Client establishes a TCP
connection to port 862 of the Server, and mode is negotiated as in connection to port 862 of the Server, and mode is negotiated as in
OWAMP. The Control-Client then requests sessions and starts them. OWAMP. The Control-Client then requests sessions and starts them.
The Session-Sender sends test packets with pseudorandom padding to The Session-Sender sends test packets with pseudorandom padding to
the Session-Reflector which returns them with insertion of the Session-Reflector which returns them with insertion of
timestamps. timestamps.
3.7. Summary of OAM Functions 4.8. TRILL
Table 3 summarizes the OAM functions that are supported in each of The requirements of OAM in TRILL are defined in [TRILL-OAM]. The main
the categories that were analyzed in this section. challenge in TRILL OAM is that traffic between RBridges RB1 and RB2
may be forwarded through more than one path. Thus, an OAM protocol
between RBridges RB1 and RB2 must be able to monitor all the
available paths between the two RBridge.
+-----------+-------+--------+--------+-----------+-------+--------+ During the writing of this document the detailed definition of the
| Standard |Continu|Connecti|Path |Defect |Perform|Other | TRILL OAM tools are still work in progress. This subsection presents
| |ity |vity |Discover|Indications|ance |Function| the main requirements of TRILL OAM.
| |Check |Verifica|y | |Monitor|s |
| | |tion | | |ing | |
+-----------+-------+--------+--------+-----------+-------+--------+
|IP Ping | |Echo | | | | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|IP | | |Tracerou| | | |
|Traceroute | | |te | | | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|BFD |BFD |BFD | | | | |
| |Control|Echo | | | | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|MPLS OAM | |"Ping" |"Tracero| | | |
|(LSP Ping) | |mode |ute" | | | |
| | | |mode | | | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|MPLS-TP |CC |CV/pro- |Route |-Alarm |-LM |-Diagnos|
|OAM | |active |Tracing | Reporting |-DM | tic Tes|
| | |or on- | |-Client | | t |
| | |demand | | Failure | |-Lock |
| | | | | Indication| | |
| | | | |-Remote | | |
| | | | | Defect | | |
| | | | | Indication| | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|PWE3 OAM |BFD |-BFD |LSP-Ping| | | |
| | |-ICMP | | | | |
| | | Ping | | | | |
| | |-LSP- | | | | |
| | | Ping | | | | |
+ --------- + ----- + ------ + ------ + --------- + ----- + ------ +
|OWAMP and | | | | |-Delay | |
|TWAMP | | | | | measur| |
| | | | | | ement | |
| | | | | |-Packet| |
| | | | | | loss | |
| | | | | | measur| |
| | | | | | ement | |
+-----------+-------+--------+--------+-----------+-------+--------+
Table 3 Summary of OAM Functions
4. Security Considerations The main requirements defined in [TRILL-OAM] are:
o Continuity Checking (CC) - the TRILL OAM protocol must support a
function for CC between any two RBridges RB1 and RB2.
o Connectivity Verification (CV) - connectivity between two RBridges
RB1 and RB2 can be verified on a per-flow basis.
o Path Tracing - allows an RBridge to trace all the available paths
to a peer RBridge.
o Performance monitoring - allows an RBridge to monitor the packet
loss and packet delay to a peer RBridge.
4.9. Summary of OAM Mechanisms
This subsection provides a short summary of each of the OAM mechanism
categories described in this document.
A detailed list of the RFCs related to each category is given in
Appendix A.1.
+-----------+------------------------------------------+------------+
| Category | Description | Transport |
| | | Technology |
+-----------+------------------------------------------+------------+
|IP Ping | Ping ([IntHost], [NetTerms]) is a simple | IPv4/IPv6 |
| | application for testing reachability that| |
| | uses ICMP Echo messages ([ICMPv4], | |
| | [ICMPv6]). | |
+-----------+------------------------------------------+------------+
|IP | Traceroute ([TCPIP-Tools], [NetTools]) is| IPv4/IPv6 |
|Traceroute | an application that allows users to trace| |
| | the path between an IP source and an IP | |
| | destination, i.e., to identify the nodes | |
| | along the path. If more than one path | |
| | exists between the source and destination| |
| | Traceroute traces *a* path. The most | |
| | common implementation of Traceroute | |
| | uses UDP probe messages, although there | |
| | are other implementations that use | |
| | different probes, such as ICMP or TCP. | |
+-----------+------------------------------------------+------------+
|BFD | Bidirectional Forwarding Detection (BFD) | generic |
| | 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. | |
+-----------+------------------------------------------+------------+
|MPLS OAM | MPLS LSP Ping, as defined in [MPLS-OAM], | MPLS |
| | [MPLS-OAM-FW] and [LSP-Ping], is an OAM | |
| | mechanism for point-to-point and | |
| | point-to-multipoint MLPS LSPs. | |
| | It includes two main functions: Ping and | |
| | Traceroute. | |
| | It is noted that while this category | |
| | focuses on LSP Ping, other OAM mechanisms| |
| | can be used in MPLS networks, e.g., BFD. | |
+-----------+------------------------------------------+------------+
|MPLS-TP OAM| MPLS-TP OAM is defined in a set of RFCs. | MPLS-TP |
| | The OAM requirements for MPLS Transport | |
| | Profile (MPLS-TP) are defined in | |
| | [MPLS-TP-OAM]. Each of the tools in the | |
| | OAM toolset is defined in its own RFC, as| |
| | specified in Section A.1. | |
+-----------+------------------------------------------+------------+
|Pseudowire | The PWE3 OAM architecture defines control| Pseudowire |
|OAM | channels that support the use of existing| |
| | IETF OAM tools to be used for a pseudo- | |
| | wire (PW). The control channels that are| |
| | defined in [VCCV] and [PW-G-ACh] may be | |
| | used in conjunction with ICMP Ping, LSP | |
| | Ping, and BFD to perform CC and CV | |
| | functionality. In addition the channels | |
| | support use of any of the MPLS-TP based | |
| | OAM tools for completing their respective| |
| | OAM functionality for a PW. | |
+-----------+------------------------------------------+------------+
|OWAMP and | The One Way Active Measurement Protocol | IPv4/IPv6 |
|TWAMP | (OWAMP) and the Two Way Active Measure- | |
| | ment Protocols (TWAMP) are two protocols | |
| | defined in the IP Performance Metrics | |
| | (IPPM) working group in the IETF. These | |
| | protocols allow various performance | |
| | metrics to be measured, such as packet | |
| | loss, delay and delay variation, | |
| | duplication and reordering. | |
+-----------+------------------------------------------+------------+
|TRILL OAM | The requirements of OAM in TRILL are | TRILL |
| | defined in [TRILL-OAM]. These | |
| | requirements include continuity checking,| |
| | connectivity verification, path tracing | |
| | and performance monitoring. During the | |
| | writing of this document the detailed | |
| | definition of the TRILL OAM tools | |
| | is work in progress. | |
+-----------+------------------------------------------+------------+
Table 3 Summary of OAM-related IETF Mechanisms
4.10. Summary of OAM Functions
Table 4 summarizes the OAM functions that are supported in each of
the categories that were analyzed in this section. The columns of
this tables are the typical OAM functions described in Section 1.3.
+-----------+-------+--------+--------+-------+----------+
| |Continu|Connecti|Path |Perform|Other |
| |ity |vity |Discover|ance |Function |
| |Check |Verifica|y |Monitor|s |
| Category | |tion | |ing | |
+-----------+-------+--------+--------+-------+----------+
|IP Ping |Echo | | | | |
+ --------- + ----- + ------ + ------ + ----- + -------- +
|IP | | |Tracerou| | |
|Traceroute | | |te | | |
+ --------- + ----- + ------ + ------ + ----- + -------- +
|BFD |BFD |BFD | | |RDI usi- |
| |Control|Control | | |ng BFD |
| |/ Echo | | | |Control |
+ --------- + ----- + ------ + ------ + ----- + -------- +
|MPLS OAM | |"Ping" |"Tracero| | |
|(LSP Ping) | |mode |ute" | | |
| | | |mode | | |
+ --------- + ----- + ------ + ------ + ----- + -------- +
|MPLS-TP |CC |CV/pro- |Route |-LM |-Diagnos- |
|OAM | |active |Tracing |-DM | tic Test |
| | |or on- | | |-Lock |
| | |demand | | |-Alarm |
| | | | | |Reporting |
| | | | | |-Client |
| | | | | |Failure |
| | | | | |Indication|
| | | | | |-RDI |
+ --------- + ----- + ------ + ------ + ----- + -------- +
|Pseudowire |BFD |-BFD |LSP-Ping| | |
|OAM | |-ICMP | | | |
| | | Ping | | | |
| | |-LSP- | | | |
| | | Ping | | | |
+ --------- + ----- + ------ + ------ + ----- + -------- +
|OWAMP and | - control | |-Delay | |
|TWAMP | protocol | | measur| |
| | | | ement | |
| | | |-Packet| |
| | | | loss | |
| | | | measur| |
| | | | ement | |
+ --------- + ----- + ------ + ------ + ----- + -------- +
|TRILL OAM |CC |CV |Path |-Delay | |
| | | |tracing | measur| |
| | | | | ement | |
| | | | |-Packet| |
| | | | | loss | |
| | | | | measur| |
| | | | | ement | |
+-----------+-------+--------+--------+-------+----------+
Table 4 Summary of the OAM Functionality in IETF OAM Mechanisms
5. Security Considerations
This memo presents an overview of existing OAM mechanisms, and This memo presents an overview of existing OAM mechanisms, and
proposes no new OAM mechanisms. Therefore, this document introduces proposes no new OAM mechanisms. Therefore, this document introduces
no security considerations. However, the OAM mechanism reviewed in no security considerations. However, the OAM mechanism reviewed in
this document can and do present security issues. The reader is this document can and do present security issues. The reader is
encouraged to review the Security Considerations section of each encouraged to review the Security Considerations section of each
document reference by this memo. document referenced by this memo.
5. IANA Considerations 6. IANA Considerations
There are no new IANA considerations implied by this document. There are no new IANA considerations implied by this document.
6. Acknowledgments 7. Acknowledgments
The authors gratefully acknowledge Sasha Vainshtein, Carlos The authors gratefully acknowledge Sasha Vainshtein, Carlos
Pignataro, David Harrington, Dan Romascanu, Ron Bonica and other Pignataro, David Harrington, Dan Romascanu, Ron Bonica and other
members of the OPSAWG mailing list for their helpful comments. members of the OPSAWG mailing list for their helpful comments.
This document was prepared using 2-Word-v2.0.template.dot. This document was prepared using 2-Word-v2.0.template.dot.
7. References 8. References
7.1. Normative References 8.1. Informative References
[LSP-Ping] Kompella, K., Swallow, G., "Detecting Multi-Protocol [LSP-Ping] Kompella, K., Swallow, G., "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379, Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006. February 2006.
[MPLS-OAM] Nadeau, T., Morrow, M., Swallow, G., Allan, D., [MPLS-OAM] Nadeau, T., Morrow, M., Swallow, G., Allan, D.,
Matsushima, S., "Operations and Management (OAM) Matsushima, S., "Operations and Management (OAM)
Requirements for Multi-Protocol Label Switched (MPLS) Requirements for Multi-Protocol Label Switched (MPLS)
Networks", RFC 4377, February 2006. Networks", RFC 4377, February 2006.
skipping to change at page 28, line 41 skipping to change at page 32, line 5
Associated Channel", RFC 5586, June 2009. Associated Channel", RFC 5586, June 2009.
[VCCV] Nadeau, T., Pignataro, C., "Pseudowire Virtual Circuit [VCCV] Nadeau, T., Pignataro, C., "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel Connectivity Verification (VCCV): A Control Channel
for Pseudowires", RFC 5085, December 2007. for Pseudowires", RFC 5085, December 2007.
[PW-ACH] Bryant, S., Swallow, G., Martini, L., McPherson, D., [PW-ACH] Bryant, S., Swallow, G., Martini, L., McPherson, D.,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word
for Use over an MPLS PSN", RFC 4385, February 2006. for Use over an MPLS PSN", RFC 4385, February 2006.
[ATM-L2] Singh, S., Townsley, M., and C. Pignataro,
"Asynchronous Transfer Mode (ATM) over Layer 2
Tunneling Protocol Version 3 (L2TPv3)", RFC 4454, May
2006.
[L2TP-EC] McGill, N. and C. Pignataro, "Layer 2 Tunneling
Protocol Version 3 (L2TPv3) Extended Circuit Status
Values", RFC 5641, August 2009.
[PW-MAP] Aissaoui, M., Busschbach, P., Martini, L., Morrow, M.,
Nadeau, T., and Y(J). Stein, "Pseudowire (PW)
Operations, Administration, and Maintenance (OAM)
Message Mapping", RFC 6310, July 2011.
[ICMPv4] Postel, J., "Internet Control Message Protocol", STD 5, [ICMPv4] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, September 1981. RFC 792, September 1981.
[ICMPv6] Conta, A., Deering, S., and M. Gupta, "Internet Control [ICMPv6] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006. Version 6 (IPv6) Specification", RFC 4443, March 2006.
[IntHost] Braden, R., "Requirements for Internet Hosts --
Communication Layers", RFC 1122, October 1989.
[NetTerms] Jacobsen, O., Lynch, D., "A Glossary of Networking
Terms", RFC 1208, March 1991.
[MPLS-P2MP] Yasukawa, S., Farrel, A., King, D., Nadeau, T., [MPLS-P2MP] Yasukawa, S., Farrel, A., King, D., Nadeau, T.,
"Operations and Management (OAM) Requirements for "Operations and Management (OAM) Requirements for
Point-to-Multipoint MPLS Networks", RFC 4687, Point-to-Multipoint MPLS Networks", RFC 4687,
September 2006. September 2006.
[ICMP-Ext] Bonica, R., Gan, D., Tappan, D., Pignataro, C., "ICMP [ICMP-Ext] Bonica, R., Gan, D., Tappan, D., Pignataro, C., "ICMP
Extensions for Multiprotocol Label Switching", RFC Extensions for Multiprotocol Label Switching", RFC
4950, August 2007. 4950, August 2007.
[ICMP-MP] Bonica, R., Gan, D., Tappan, D., Pignataro, C., [ICMP-MP] Bonica, R., Gan, D., Tappan, D., Pignataro, C.,
"Extended ICMP to Support Multi-Part Messages", RFC "Extended ICMP to Support Multi-Part Messages", RFC
4884, April 2007. 4884, April 2007.
[ICMP-Int] Atlas, A., Bonica, R., Pignataro, C., Shen, N., Rivers, [ICMP-Int] Atlas, A., Bonica, R., Pignataro, C., Shen, N., Rivers,
JR., "Extending ICMP for Interface and Next-Hop JR., "Extending ICMP for Interface and Next-Hop
Identification", RFC 5837, April 2010. Identification", RFC 5837, April 2010.
[TCPIP-Tools] Kessler, G., Shepard, S., "A Primer On Internet and [TCPIP-Tools] Kessler, G., Shepard, S., "A Primer On Internet and
TCP/IP Tools and Utilities", RFC 2151, June 1997. TCP/IP Tools and Utilities", RFC 2151, June 1997.
[NetTools] Stine, R., "FYI on a Network Management Tool Catalog: [NetTools] Enger, R., Reynolds, J., "FYI on a Network Management
Tools for Monitoring and Debugging TCP/IP Internets Tool Catalog: Tools for Monitoring and Debugging
and Interconnected Devices", RFC 1147, April 1990. TCP/IP Internets and Interconnected Devices", RFC
1470, June 1993.
[IPPM-FW] Paxson, V., Almes, G., Mahdavi, J., and Mathis, M., [IPPM-FW] Paxson, V., Almes, G., Mahdavi, J., and Mathis, M.,
"Framework for IP Performance Metrics", RFC 2330, May "Framework for IP Performance Metrics", RFC 2330, May
1998. 1998.
[IPPM-Con] Mahdavi, J., Paxson, V., "IPPM Metrics for Measuring [IPPM-Con] Mahdavi, J., Paxson, V., "IPPM Metrics for Measuring
Connectivity", RFC 2678, September 1999. Connectivity", RFC 2678, September 1999.
[IPPM-1DM] Almes, G., Kalidindi, S., Zekauskas, M., "A One-way [IPPM-1DM] Almes, G., Kalidindi, S., Zekauskas, M., "A One-way
Delay Metric for IPPM", RFC 2679, September 1999. Delay Metric for IPPM", RFC 2679, September 1999.
[IPPM-1LM] Almes, G., Kalidindi, S., Zekauskas, M., "A One-way [IPPM-1LM] Almes, G., Kalidindi, S., Zekauskas, M., "A One-way
Packet Loss Metric for IPPM", RFC 2680, September Packet Loss Metric for IPPM", RFC 2680, September
1999. 1999.
[IPPM-2DM] Almes, G., Kalidindi, S., Zekauskas, M., "A Round-trip [IPPM-2DM] Almes, G., Kalidindi, S., Zekauskas, M., "A Round-trip
Delay Metric for IPPM", RFC 2681, September 1999. Delay Metric for IPPM", RFC 2681, September 1999.
[PM-CONS] Clark, A. and B. Claise, "Guidelines for Considering
New Performance Metric Development", BCP 170, RFC
6390, October 2011.
[OWAMP] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and [OWAMP] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and
Zekauskas, M., "A One-way Active Measurement Protocol Zekauskas, M., "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006. (OWAMP)", RFC 4656, September 2006.
[TWAMP] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and [TWAMP] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and
Babiarz, J., "A Two-Way Active Measurement Protocol Babiarz, J., "A Two-Way Active Measurement Protocol
(TWAMP)", RFC 5357, October 2008. (TWAMP)", RFC 5357, October 2008.
[Reorder] Morton, A., Ciavattone, L., Ramachandran, G., Shalunov,
S., and J. Perser, "Packet Reordering Metrics", RFC
4737, November 2006.
[Dup] Uijterwaal, H., "A One-Way Packet Duplication Metric",
RFC 5560, May 2009.
[BFD] Katz, D., Ward, D., "Bidirectional Forwarding Detection [BFD] Katz, D., Ward, D., "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010. (BFD)", RFC 5880, June 2010.
[BFD-IP] Katz, D., Ward, D., "Bidirectional Forwarding Detection [BFD-IP] Katz, D., Ward, D., "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June
2010. 2010.
[BFD-Gen] Katz, D., Ward, D., "Generic Application of [BFD-Gen] Katz, D., Ward, D., "Generic Application of
Bidirectional Forwarding Detection (BFD)", RFC 5882, Bidirectional Forwarding Detection (BFD)", RFC 5882,
June 2010. June 2010.
skipping to change at page 31, line 24 skipping to change at page 35, line 20
[PW-Map] M. Aissaoui, P. Busschbach, L. Martini, M. Morrow, T. [PW-Map] M. Aissaoui, P. Busschbach, L. Martini, M. Morrow, T.
Nadeau, "Pseudowire (PW) Operations, Administration, Nadeau, "Pseudowire (PW) Operations, Administration,
and Maintenance (OAM) Message Mapping", RFC 6310, July and Maintenance (OAM) Message Mapping", RFC 6310, July
2011. 2011.
[PW-G-ACh] Li, H., Martini, L., He, J., Huang, F., "Using the [PW-G-ACh] Li, H., Martini, L., He, J., Huang, F., "Using the
Generic Associated Channel Label for Pseudowire in the Generic Associated Channel Label for Pseudowire in the
MPLS Transport Profile (MPLS-TP)", RFC 6423, November MPLS Transport Profile (MPLS-TP)", RFC 6423, November
2011. 2011.
7.2. Informative References
[OAM-Def] Andersson, L., Van Helvoort, H., Bonica, R., Romascanu, [OAM-Def] Andersson, L., Van Helvoort, H., Bonica, R., Romascanu,
D., Mansfield, S., "Guidelines for the use of the OAM D., Mansfield, S., "Guidelines for the use of the OAM
acronym in the IETF ", RFC 6291, June 2011. acronym in the IETF ", RFC 6291, June 2011.
[OAM-Analys] Sprecher, N., Fang, L., "An Overview of the OAM Tool [OAM-Analys] Sprecher, N., Fang, L., "An Overview of the OAM Tool
Set for MPLS based Transport Networks", RFC 6669, Set for MPLS based Transport Networks", RFC 6669,
July 2012. July 2012.
[TP-Term] Van Helvoort, H., Andersson, L., Sprecher, N., "A [TP-Term] Van Helvoort, H., Andersson, L., Sprecher, N., "A
Thesaurus for the Terminology used in Multiprotocol Thesaurus for the Terminology used in Multiprotocol
Label Switching Transport Profile (MPLS-TP) Label Switching Transport Profile (MPLS-TP)
drafts/RFCs and ITU-T's Transport Network drafts/RFCs and ITU-T's Transport Network
Recommendations", work-in-progress, draft-ietf-mpls- Recommendations", work-in-progress, draft-ietf-mpls-
tp-rosetta-stone, July 2012. tp-rosetta-stone, July 2012.
[IEEE802.1ag] IEEE 802.1Q, "IEEE Standard for Local and metropolitan [Cont] Dugal, D., Pignataro, C., Dunn, R., "Protecting the
Router Control Plane", RFC 6192, March 2011.
[Mng] Farrel, A., "Inclusion of Manageability Sections in
Path Computation Element (PCE) Working Group Drafts",
RFC 6123, February 2011.
[TRILL-OAM] Senevirathne, T., Bond, D., Aldrin, S., Li, Y., Watve,
R., "Requirements for Operations, Administration, and
Maintenance (OAM) in Transparent Interconnection of
Lots of Links (TRILL)", RFC 6905, March 2013.
[IEEE802.1Q] IEEE 802.1Q, "IEEE Standard for Local and metropolitan
area networks - Media Access Control (MAC) Bridges and area networks - Media Access Control (MAC) Bridges and
Virtual Bridged Local Area Networks", October 2012. Virtual Bridged Local Area Networks", October 2012.
[ITU-T-Y1731] ITU-T Recommendation G.8013/Y.1731, "OAM Functions and [ITU-T-Y1731] ITU-T Recommendation G.8013/Y.1731, "OAM Functions and
Mechanisms for Ethernet-based Networks", July 2011. Mechanisms for Ethernet-based Networks", July 2011.
[ITU-T-Y1711] ITU-T Recommendation Y.1711, "Operation & Maintenance [ITU-T-Y1711] ITU-T Recommendation Y.1711, "Operation & Maintenance
mechanism for MPLS networks", February 2004. mechanism for MPLS networks", February 2004.
[IEEE802.3ah] IEEE 802.3, "IEEE Standard for Information technology - [IEEE802.3ah] IEEE 802.3, "IEEE Standard for Information technology -
skipping to change at page 32, line 24 skipping to change at page 36, line 30
[ITU-G8113.2] ITU-T Recommendation G.8113.2/Y.1372.2, "Operations, [ITU-G8113.2] ITU-T Recommendation G.8113.2/Y.1372.2, "Operations,
administration and maintenance mechanisms for MPLS-TP administration and maintenance mechanisms for MPLS-TP
networks using the tools defined for MPLS", November networks using the tools defined for MPLS", November
2012. 2012.
[ITU-G8113.1] ITU-T Recommendation G.8113.1/Y.1372.1, "Operations, [ITU-G8113.1] ITU-T Recommendation G.8113.1/Y.1372.1, "Operations,
Administration and Maintenance mechanism for MPLS-TP Administration and Maintenance mechanism for MPLS-TP
in Packet Transport Network (PTN)", November 2012. in Packet Transport Network (PTN)", November 2012.
Appendix A. List of OAM Documents
A.1. List of IETF OAM Documents
Table 5 summarizes the OAM related RFCs published by the IETF.
It is important to note that the table lists various RFCs that are
different by nature. For example, some of these documents define OAM
tools or OAM protocols (or both), while others define protocols that
are not strictly OAM-related, but are used by OAM tools. The table
also includes memos that define the requirements or the framework of
OAM in the context of a specific transport technology, or describe
how to use existing OAM tools in a new transport technology.
The RFCs in the table are categorized in a few sets as defined in
Section 1.3.
+-----------+--------------------------------------+----------+
| Category | Title | RFC |
+-----------+--------------------------------------+----------+
|IP Ping | Requirements for Internet Hosts -- | RFC 1122 |
| | Communication Layers [IntHost] | |
| +--------------------------------------+----------+
| | A Glossary of Networking Terms | RFC 1208 |
| | [NetTerms] | |
| +--------------------------------------+----------+
| | Internet Control Message Protocol | RFC 792 |
| | [ICMPv4] | |
| +--------------------------------------+----------+
| | Internet Control Message Protocol | RFC 4443 |
| | (ICMPv6) for the Internet Protocol | |
| | Version 6 (IPv6) Specification | |
| | [ICMPv6] | |
+-----------+--------------------------------------+----------+
|IP | A Primer On Internet and TCP/IP | RFC 2151 |
|Traceroute | Tools and Utilities [TCPIP-Tools] | |
| +--------------------------------------+----------+
| | FYI on a Network Management Tool | RFC 1470 |
| | Catalog: Tools for Monitoring and | |
| | Debugging TCP/IP Internets and | |
| | Interconnected Devices [NetTools] | |
| +--------------------------------------+----------+
| | Internet Control Message Protocol | RFC 792 |
| | [ICMPv4] | |
| +--------------------------------------+----------+
| | Internet Control Message Protocol | RFC 4443 |
| | (ICMPv6) for the Internet Protocol | |
| | Version 6 (IPv6) Specification | |
| | [ICMPv6] | |
| +--------------------------------------+----------+
| | Extended ICMP to Support Multi-Part | RFC 4884 |
| | Messages [ICMP-MP] | |
| +--------------------------------------+----------+
| | Extending ICMP for Interface and | RFC 5837 |
| | Next-Hop Identification [ICMP-Int] | |
+-----------+--------------------------------------+----------+
|BFD | Bidirectional Forwarding Detection | RFC 5880 |
| | [BFD] | |
| +--------------------------------------+----------+
| | Bidirectional Forwarding Detection | RFC 5881 |
| | (BFD) for IPv4 and IPv6 (Single Hop) | |
| | [BFD-IP] | |
| +--------------------------------------+----------+
| | Generic Application of Bidirectional | RFC 5882 |
| | Forwarding Detection [BFD-Gen] | |
| +--------------------------------------+----------+
| | Bidirectional Forwarding Detection | RFC 5883 |
| | (BFD) for Multihop Paths [BFD-Multi] | |
| +--------------------------------------+----------+
| | Bidirectional Forwarding Detection | RFC 5884 |
| | for MPLS Label Switched Paths (LSPs) | |
| | [BFD-LSP] | |
| +--------------------------------------+----------+
| | Bidirectional Forwarding Detection | RFC 5885 |
| | for the Pseudowire Virtual Circuit | |
| | Connectivity Verification (VCCV) | |
| | [BFD-VCCV] | |
+-----------+--------------------------------------+----------+
|MPLS OAM | Operations and Management (OAM) | RFC 4377 |
| | Requirements for Multi-Protocol Label| |
| | Switched (MPLS) Networks [MPLS-OAM] | |
| +--------------------------------------+----------+
| | A Framework for Multi-Protocol | RFC 4378 |
| | Label Switching (MPLS) Operations | |
| | and Management (OAM) [MPLS-OAM-FW] | |
| +--------------------------------------+----------+
| | Detecting Multi-Protocol Label | RFC 4379 |
| | Switched (MPLS) Data Plane Failures | |
| | [LSP-Ping] | |
| +--------------------------------------+----------+
| | Operations and Management (OAM) | RFC 4687 |
| | Requirements for Point-to-Multipoint | |
| | MPLS Networks [MPLS-P2MP] | |
| +--------------------------------------+----------+
| | ICMP Extensions for Multiprotocol | RFC 4950 |
| | Label Switching [ICMP-Ext] | |
+-----------+--------------------------------------+----------+
|MPLS-TP | Requirements for OAM in MPLS-TP | RFC 5860 |
|OAM | [MPLS-TP-OAM] | |
| +--------------------------------------+----------+
| | MPLS Generic Associated Channel | RFC 5586 |
| | [G-ACh] | |
| +--------------------------------------+----------+
| | MPLS-TP OAM Framework | RFC 6371 |
| | [TP-OAM-FW] | |
| +--------------------------------------+----------+
| | Proactive Connectivity Verification, | RFC 6428 |
| | Continuity Check, and Remote Defect | |
| | Indication for the MPLS Transport | |
| | Profile [TP-CC-CV] | |
| +--------------------------------------+----------+
| | MPLS On-Demand Connectivity | RFC 6426 |
| | Verification and Route Tracing | |
| | [OnDemand-CV] | |
| +--------------------------------------+----------+
| | MPLS Fault Management Operations, | RFC 6427 |
| | Administration, and Maintenance (OAM)| |
| | [TP-Fault] | |
| +--------------------------------------+----------+
| | MPLS Transport Profile Lock Instruct | RFC 6435 |
| | and Loopback Functions [Lock-Loop] | |
| +--------------------------------------+----------+
| | Packet Loss and Delay Measurement for| RFC 6374 |
| | MPLS Networks [MPLS-LM-DM] | |
| +--------------------------------------+----------+
| | A Packet Loss and Delay Measurement | RFC 6375 |
| | Profile for MPLS-Based Transport | |
| | Networks [TP-LM-DM] | |
+-----------+--------------------------------------+----------+
|Pseudowire | Pseudowire Virtual Circuit | RFC 5085 |
|OAM | Connectivity Verification (VCCV): | |
| | A Control Channel for Pseudowires | |
| | [VCCV] | |
| +--------------------------------------+----------+
| | Bidirectional Forwarding Detection | RFC 5885 |
| | for the Pseudowire Virtual Circuit | |
| | Connectivity Verification (VCCV) | |
| | [BFD-VCCV] | |
| +--------------------------------------+----------+
| | Using the Generic Associated Channel | RFC 6423 |
| | Label for Pseudowire in the MPLS | |
| | Transport Profile (MPLS-TP) | |
| | [PW-G-ACh] | |
| +--------------------------------------+----------+
| | Pseudowire (PW) Operations, | RFC 6310 |
| | Administration, and Maintenance (OAM)| |
| | Message Mapping [PW-Map] | |
+-----------+--------------------------------------+----------+
|OWAMP and | A One-way Active Measurement Protocol| RFC 4656 |
|TWAMP | [OWAMP] | |
| +--------------------------------------+----------+
| | A Two-Way Active Measurement Protocol| RFC 5357 |
| | [TWAMP] | |
| +--------------------------------------+----------+
| | Framework for IP Performance Metrics | RFC 2330 |
| | [IPPM-FW] | |
| +--------------------------------------+----------+
| | IPPM Metrics for Measuring | RFC 2678 |
| | Connectivity [IPPM-Con] | |
| +--------------------------------------+----------+
| | A One-way Delay Metric for IPPM | RFC 2679 |
| | [IPPM-1DM] | |
| +--------------------------------------+----------+
| | A One-way Packet Loss Metric for IPPM| RFC 2680 |
| | [IPPM-1LM] | |
| +--------------------------------------+----------+
| | A Round-trip Delay Metric for IPPM | RFC 2681 |
| | [IPPM-2DM] | |
| +--------------------------------------+----------+
| | Packet Reordering Metrics | RFC 4737 |
| | [Reorder] | |
| +--------------------------------------+----------+
| | A One-Way Packet Duplication Metric | RFC 5560 |
| | [Dup] | |
+-----------+--------------------------------------+----------+
|TRILL OAM | Requirements for Operations, | RFC 6905 |
| | Administration, and Maintenance (OAM)| |
| | in Transparent Interconnection of | |
| | Lots of Links (TRILL) | |
+-----------+--------------------------------------+----------+
Table 5 Summary of IETF OAM Related RFCs
A.2. List of Selected Non-IETF OAM Documents
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-Y1711] 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 Layer 2 have been defined by the ITU-T in
[ITU-T-Y1731], and by the IEEE in 802.1ag [IEEE802.1Q] . The IEEE
802.3 standard defines OAM for one-hop Ethernet links
[IEEE802.3ah].
o The ITU-T has defined OAM for MPLS LSPs in [ITU-T-Y1711], and
MPLS-TP OAM in [ITU-G8113.1] and [ITU-G8113.2].
It should be noted that these non-IETF documents deal in many cases
with OAM functions below the IP layer (Layer 2, Layer 2.5) and in
some cases operators use a multi-layered OAM approach, which is a
function of the way their networks are designed.
Table 6 summarizes some of the main OAM standards published by non-
IETF standard organizations. This document focuses on IETF OAM
standards, but these non-IETF standards are referenced in this
document where relevant.
+-----------+--------------------------------------+---------------+
| | Title |Standard/Draft |
+-----------+--------------------------------------+---------------+
|ITU-T | Operation & Maintenance mechanism | ITU-T Y.1711 |
|MPLS OAM | for MPLS networks [ITU-T-Y1711] | |
| +--------------------------------------+---------------+
| | Assignment of the 'OAM Alert Label' | RFC 3429 |
| | for Multiprotocol Label Switching | |
| | Architecture (MPLS) Operation and | |
| | Maintenance (OAM) Functions | |
| | [OAM-Label] | |
| | | |
| | 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 ITU-T Y.1711. | |
+-----------+--------------------------------------+---------------+
|ITU-T | Operations, administration and |ITU-T G.8113.2 |
|MPLS-TP OAM| Maintenance mechanisms for MPLS-TP | |
| | networks using the tools defined for | |
| | MPLS [ITU-G8113.2] | |
| | | |
| | Note: this document describes the | |
| | OAM toolset defined by the IETF for | |
| | MPLS-TP, whereas ITU-T G.8113.1 | |
| | describes the OAM toolset defined | |
| | by the ITU-T. | |
| +--------------------------------------+---------------+
| | Operations, Administration and |ITU-T G.8113.1 |
| | Maintenance mechanism for MPLS-TP in | |
| | Packet Transport Network (PTN) | |
| +--------------------------------------+---------------+
| | Allocation of a Generic Associated | RFC 6671 |
| | Channel Type for ITU-T MPLS Transport| |
| | Profile Operation, Maintenance, and | |
| | Administration (MPLS-TP OAM) | |
| | [ITU-T-CT] | |
| | | |
| | 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 ITU-T G.8113.1. | |
+-----------+--------------------------------------+---------------+
|ITU-T | OAM Functions and Mechanisms for | ITU-T Y.1731 |
|Ethernet | Ethernet-based Networks | |
|OAM | [ITU-T-Y1731] | |
+-----------+--------------------------------------+---------------+
|IEEE | Connectivity Fault Management | IEEE 802.1ag |
|CFM | [IEEE802.1Q] | |
| | | |
| | Note: CFM was originally published | |
| | as IEEE 802.1ag, but is now | |
| | incorporated in the 802.1Q standard.| |
+-----------+--------------------------------------+---------------+
|IEEE | Management of Data Driven and Data | IEEE 802.1ag |
|DDCFM | Dependent Connectivity Faults | |
| | [IEEE802.1Q] | |
| | | |
| | Note: DDCFM was originally published| |
| | as IEEE 802.1Qaw, but is now | |
| | incorporated in the 802.1Q standard.| |
+-----------+--------------------------------------+---------------+
|IEEE | Media Access Control Parameters, | IEEE 802.3ah |
|802.3 | Physical Layers, and Management | |
|link level | Parameters for Subscriber Access | |
|OAM | Networks [IEEE802.3ah] | |
| | | |
| | Note: link level OAM was originally | |
| | defined in IEEE 802.3ah, and is now | |
| | incorporated in the 802.3 standard. | |
+-----------+--------------------------------------+---------------+
Table 6 Non-IETF OAM Standards Mentioned in this Document
Authors' Addresses Authors' Addresses
Tal Mizrahi Tal Mizrahi
Marvell Marvell
6 Hamada St. 6 Hamada St.
Yokneam, 20692 Yokneam, 20692
Israel Israel
Email: talmi@marvell.com Email: talmi@marvell.com
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