Operations and Management Area Working Group T. Mizrahi Internet Draft Marvell Intended status: Informational N. Sprecher Expires: September 2011 Nokia Siemens Networks E. Bellagamba Ericsson Y. Weingarten Nokia Siemens Networks March 29, 2011 An Overview of Operations, Administration, and Maintenance (OAM) Mechanisms draft-ietf-opsawg-oam-overview-04.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on September 29, 2011. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect Mizrahi, et al. Expires September 29, 2011 [Page 1] Internet-Draft Overview of OAM Mechanisms March 2011 to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Abstract Operations, Administration, and Maintenance (OAM) is a general term that refers to a toolset that can be used for fault detection and localization, and for performance measurement. OAM mechanisms have been defined for various layers in the protocol stack, and are used with a variety of protocols. This document presents an overview of the OAM mechanisms that have been defined and are currently being defined by the IETF, as well as a comparison to other OAM mechanisms that have been defined by the IEEE and ITU-T. Table of Contents 1. Introduction................................................4 2. Conventions used in this document............................8 3. Basic Terminology...........................................8 3.1. Abbreviations..........................................8 3.2. Terminology used in OAM Standards.......................9 3.2.1. General Terms......................................9 3.2.2. OAM Maintenance Entities and Communication Links...10 3.2.3. OAM Maintenance Points............................10 3.2.4. Connectivity Verification and Continuity Checks....11 3.2.5. Link Failures.....................................11 3.2.6. Summary of OAM Terms used in the Standards.........12 4. OAM Functions..............................................13 4.1. ICMP Ping.............................................13 4.2. Bidirectional Forwarding Detection (BFD)...............14 4.2.1. Overview.........................................14 4.2.2. BFD Control.......................................14 4.2.3. BFD Echo.........................................15 4.3. LSP Ping..............................................15 4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV)...16 4.5. IP Performance Metrics (IPPM)..........................16 4.5.1. Overview.........................................16 4.5.2. Control and Test Protocols........................17 4.5.3. OWAMP............................................17 4.5.4. TWAMP............................................18 4.6. ITU-T Y.1711..........................................18 4.6.1. Overview.........................................18 Mizrahi, et al. Expires September 29, 2011 [Page 2] Internet-Draft Overview of OAM Mechanisms March 2011 4.6.2. Connectivity Verification (CV)....................19 4.6.3. Fast Failure Detection (FFD)......................19 4.6.4. Forward Defect Indication (FDI)...................19 4.6.5. Backward Defect Indication (BDI)..................20 4.7. ITU-T Y.1731..........................................20 4.7.1. Overview.........................................20 4.7.2. ETH-CC...........................................20 4.7.3. ETH-LB...........................................21 4.7.4. ETH-TST..........................................21 4.7.5. ETH-LT...........................................21 4.7.6. ETH-AIS..........................................21 4.7.7. ETH-LCK..........................................21 4.7.8. ETH-RDI..........................................22 4.7.9. ETH-APS..........................................22 4.7.10. ETH-LM..........................................22 4.7.11. ETH-DM..........................................22 4.8. IEEE 802.1ag..........................................23 4.8.1. Overview.........................................23 4.8.2. Continuity Check..................................23 4.8.3. Loopback.........................................23 4.8.4. Linktrace........................................24 4.9. IEEE 802.3ah..........................................24 4.9.1. Overview.........................................24 4.9.2. Remote Failure Indication.........................24 4.9.3. Remote Loopback...................................24 4.9.4. Link Monitoring...................................24 4.10. MPLS-TP OAM..........................................24 4.10.1. Overview........................................24 4.10.2. Generic Associated Channel.......................25 4.10.3. MPLS-TP OAM Toolset..............................25 4.10.3.1. Continuity Check and Connectivity Verification26 4.10.3.2. Diagnostic Tests............................26 4.10.3.3. Route Tracing...............................26 4.10.3.4. Lock Instruct...............................27 4.10.3.5. Lock Reporting..............................27 4.10.3.6. Alarm Reporting.............................27 4.10.3.7. Remote Defect Indication....................27 4.10.3.8. Client Failure Indication...................27 4.10.3.9. Packet Loss Measurement.....................27 4.10.3.10. Packet Delay Measurement...................28 4.11. Summary of OAM Functions..............................28 4.12. Summary of Continuity Check Mechanisms................30 5. Security Considerations.....................................31 6. IANA Considerations........................................31 7. Acknowledgments............................................31 8. References.................................................31 8.1. Normative References...................................31 Mizrahi, et al. Expires September 29, 2011 [Page 3] Internet-Draft Overview of OAM Mechanisms March 2011 8.2. Informative References.................................33 1. Introduction OAM is a general term that refers to a toolset that can be used for detecting, isolating and reporting connection failures or measurement of connection performance parameters. The term OAM has been used over the years in several different contexts, as discussed in [OAM Soup]. In the context of this document OAM refers to Operations, Administration, and Maintenance, i.e., this document refers to OAM in the context of monitoring communication entities, e.g., nodes, paths, physical links, or logical links. Other aspects associated with the OAM acronym, such as management, are outside the scope of this document. OAM was originally used in the world of telephony, and has been adopted in packet based networks. OAM mechanisms are used in various layers in the protocol stack, and are applied to a variety of different protocols. The IETF has defined OAM for several protocols, and is currently working on defining several new OAM protocols. A summary of these protocols, old and new, is listed below: o MPLS LSP Ping, as defined in [LSP Ping] is an OAM mechanism for point to point MPLS LSPs. The IETF is currently working on an extension to the LSP Ping for point to multipoint MPLS - [P2MP Ping]. o Virtual Circuit Connectivity Check (VCCV) for Pseudowires, as defined in [VCCV]. o ICMP Echo request, also known as Ping, as defined in [ICMPv4], and [ICMPv6]. ICMP Ping is a very simple and basic mechanism in failure diagnosis, and is not traditionally associated with OAM, but it is presented in this document for the sake of completeness, since both LSP Ping and VCCV are to some extent based on ICMP Ping. o Bidirectional Forwarding Detection (BFD) is defined in [BFD] as a framework for a lightweight generic OAM mechanism. The intention is to define a base mechanism that can be used with various encapsulation types, network environments, and in various medium types. Mizrahi, et al. Expires September 29, 2011 [Page 4] Internet-Draft Overview of OAM Mechanisms March 2011 o The OAM requirements for MPLS Transport Profile (MPLS-TP) are defined in [MPLS-TP OAM], and the toolset is described in [MPLS-TP OAM FW]. The OAM toolset for MPLS-TP is currently being defined in the MPLS working group. o IP Performance Metrics (IPPM) is a working group in the IETF that defined common metrics for performance measurement, as well as a protocol for measuring delay and packet loss in IP networks. Alternative protocols for performance measurement are defined, for example, in MPLS-TP OAM [MPLS-TP OAM], and in Ethernet OAM [ITU-T Y.1731]. In addition to the OAM mechanisms defined by the IETF, the IEEE and ITU-T have also defined various OAM mechanisms. These various mechanisms defined by the three standard organizations are often tightly coupled, and have had a mutual effect on each other. The ITU- T and IETF have both defined OAM mechanisms for MPLS LSPs, [ITU-T Y.1711] and [LSP Ping]. The following OAM standards by the IEEE and ITU-T are to some extent linked to IETF OAM mechanisms listed above, and are also discussed in this document: o OAM mechanisms for Ethernet based networks have been defined by both the ITU-T in [ITU-T Y.1731], and by the IEEE in [IEEE 802.1ag]. The IEEE 802.3 standard defines OAM for one-hop Ethernet links [IEEE 802.3ah]. o The ITU-T has defined OAM for MPLS LSPs in [ITU-T Y.1711]. This document summarizes the OAM mechanisms defined in the standards above. The focus is on OAM mechanisms defined by the IETF. These mechanisms will be compared with the relevant OAM mechanisms defined by the ITU-T and IEEE, where applicable. We first present a comparison of the terminology used in various OAM standards, and then summarize the OAM functions that each OAM standard provides. Table 1 summarizes the OAM standards discussed in this document. +-----------+--------------------------------------+---------------+ | | Title |Standard/Draft | +-----------+--------------------------------------+---------------+ |ICMPv4 Ping| Internet Control Message Protocol | RFC 792 | | | | | +-----------+--------------------------------------+---------------+ |ICMPv6 Ping| Internet Control Message Protocol | RFC 4443 | | | (ICMPv6) for the Internet Protocol | | Mizrahi, et al. Expires September 29, 2011 [Page 5] Internet-Draft Overview of OAM Mechanisms March 2011 | | Version 6 (IPv6) Specification | | +-----------+--------------------------------------+---------------+ |BFD | Bidirectional Forwarding Detection | RFC 5880 | | +--------------------------------------+---------------+ | | Bidirectional Forwarding Detection | RFC 5881 | | | (BFD) for IPv4 and IPv6 (Single Hop) | | | +--------------------------------------+---------------+ | | Generic Application of Bidirectional | RFC 5882 | | | Forwarding Detection | | | +--------------------------------------+---------------+ | | Bidirectional Forwarding Detection | RFC 5883 | | | (BFD) for Multihop Paths | | | +--------------------------------------+---------------+ | | Bidirectional Forwarding Detection | RFC 5884 | | | for MPLS Label Switched Paths (LSPs) | | | +--------------------------------------+---------------+ | | Bidirectional Forwarding Detection | RFC 5885 | | | for the Pseudowire Virtual Circuit | | | | Connectivity Verification (VCCV) | | +-----------+--------------------------------------+---------------+ |IETF MPLS | Operations and Management (OAM) | RFC 4377 | |OAM | Requirements for Multi-Protocol Label| | |(LSP Ping) | Switched (MPLS) Networks | | | +--------------------------------------+---------------+ | | A Framework for Multi-Protocol | RFC 4378 | | | Label Switching (MPLS) Operations | | | | and Management (OAM) | | | +--------------------------------------+---------------+ | | Detecting Multi-Protocol Label | RFC 4379 | | | Switched (MPLS) Data Plane Failures | | | +--------------------------------------+---------------+ | | Operations and Management (OAM) | RFC 4687 | | | Requirements for Point-to-Multipoint | | | | MPLS Networks | | +-----------+--------------------------------------+---------------+ |MPLS-TP | Requirements for OAM in MPLS-TP | RFC 5860 | |OAM +--------------------------------------+---------------+ | | MPLS Generic Associated Channel | RFC 5586 | | +--------------------------------------+---------------+ | | MPLS-TP OAM Framework |[MPLS-TP OAM FW| | | |] - work in | Mizrahi, et al. Expires September 29, 2011 [Page 6] Internet-Draft Overview of OAM Mechanisms March 2011 | | |progress | | +--------------------------------------+---------------+ | | MPLS-TP OAM Analysis |[OAM Analysis] | | | | - work in | | | |progress | +-----------+--------------------------------------+---------------+ |PW VCCV | Pseudowire Virtual Circuit | RFC 5085 | | | Connectivity Verification (VCCV): | | | | A Control Channel for Pseudowires | | +-----------+--------------------------------------+---------------+ |IPPM | Framework for IP Performance Metrics | RFC 2330 | | +--------------------------------------+---------------+ | | IPPM Metrics for Measuring | RFC 2678 | | | Connectivity | | | +--------------------------------------+---------------+ | | A One-way Delay Metric for IPPM | RFC 2679 | | +--------------------------------------+---------------+ | | A One-way Packet Loss Metric for IPPM| RFC 2680 | | +--------------------------------------+---------------+ | | A Round-trip Delay Metric for IPPM | RFC 2681 | | +--------------------------------------+---------------+ | | A One-way Active Measurement Protocol| RFC 4656 | | | (OWAMP) | | | +--------------------------------------+---------------+ | | A Two-Way Active Measurement Protocol| RFC 5357 | | | (TWAMP) | | +-----------+--------------------------------------+---------------+ |ITU-T | Operation & Maintenance mechanism |[ITU-T Y.1711] | |MPLS OAM | for MPLS networks | | | +--------------------------------------+---------------+ | | Assignment of the 'OAM Alert Label' | RFC 3429 | | | for Multiprotocol Label Switching | | | | Architecture (MPLS) Operation and | | | | Maintenance (OAM) Functions | | +-----------+--------------------------------------+---------------+ |ITU-T | OAM Functions and Mechanisms for |[ITU-T Y.1731] | |Ethernet | Ethernet-based Networks | | |OAM | | | +-----------+--------------------------------------+---------------+ |IEEE | Connectivity Fault Management |[IEEE 802.1ag] | |CFM | | | Mizrahi, et al. Expires September 29, 2011 [Page 7] Internet-Draft Overview of OAM Mechanisms March 2011 +-----------+--------------------------------------+---------------+ |IEEE | Media Access Control Parameters, |[IEEE 802.3ah] | |802.3 | Physical Layers, and Management | | |link level | Parameters for Subscriber Access | | |OAM | Networks | | +-----------+--------------------------------------+---------------+ Table 1 Summary of OAM Standards 2. Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [KEYWORDS]. 3. Basic Terminology 3.1. Abbreviations AIS Alarm Indication Signal APS Automatic Protection Switching BDI Backward Defect Indication BFD Bidirectional Forwarding Detection CC Continuity Check CCM Continuity Check Message CV Connectivity Verification DM Delay Measurement DTE Data Terminal Equipment FDI Forward Defect Indication FFD Fast Failure Detection ICMP Internet Control Message Protocol L2TP Layer Two Tunneling Protocol LCCE L2TP Control Connection Endpoint Mizrahi, et al. Expires September 29, 2011 [Page 8] Internet-Draft Overview of OAM Mechanisms March 2011 LM Loss Measurement LSP Label Switching Path LSR Label Switching Router MA Maintenance Association ME Maintenance Entity MEG Maintenance Entity Group MEP Maintenance End Point MHF MIP Half Function MIP Maintenance Intermediate Point MP Maintenance Point MPLS Multiprotocol Label Switching MPLS-TP MPLS Transport Profile OAM Operations, Administration, and Maintenance PE Provider Edge PW Pseudowire PWE3 Pseudowire Emulation Edge-to-Edge RDI Remote Defect Indication TTL Time To Live TTSI Trail Termination Source Identifier VCCV Virtual Circuit Connectivity Verification 3.2. Terminology used in OAM Standards 3.2.1. General Terms A wide variety of terms is used in various OAM standards. Each of the OAM standards listed in the reference section includes a section that defines the relevant terms. A thesaurus of terminology for MPLS-TP Mizrahi, et al. Expires September 29, 2011 [Page 9] Internet-Draft Overview of OAM Mechanisms March 2011 terms is presented in [MPLS-TP Term], and provides a good summary of some of the OAM related terminology. This section presents a comparison of the terms used in various OAM standards, without fully quoting the definition of each term. For a formal definition of each term, refer to the references at the end of this document. The comparison focuses on three basic terms, and is summarized in section 3 ..2.6. 3.2.2. OAM Maintenance Entities and Communication Links A Maintenance Entity (ME) is a point-to-point relationship between two Maintenance Points (MP). The connectivity between these Maintenance Points is managed and monitored by the OAM protocol. A pair of MPs engaged in an ME are connected by a communication Link. The term "Link" in this context is a generic term that may refer to 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 Link is used throughout this document to refer to the connection between the MPs that is monitored by an OAM protocol. The term Maintenance Entity (ME) is defined in ITU-T standards (e.g. [ITU-T Y.1731]). Various terms are used to refer to an ME. For example, in MPLS LSP Ping ([LSP Ping]) terminology, an ME is simply referred to as an LSP. 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. MPLS-TP has defined the terms ME and Maintenance Entity Group (MEG) in [MPLS-TP OAM FW], similar to the terms defined by ITU-T. 3.2.3. OAM Maintenance Points A Maintenance Point (MP) is a functional entity that is defined at a node in the network, and either initiates or reacts to OAM messages. A Maintenance End Point (MEP) is one of the end points of an ME, and can initiate OAM messages and respond to them. A Maintenance Intermediate Point (MIP) is an intermediate point between two MEPs, that does not initiate OAM frames, but is able to respond to OAM frames that are destined to it, and to forward others. The terms MEP and MIP are defined in ITU-T standards (e.g. [ITU-T Y.1731]). The term Maintenance Point is a general term for MEPs and MIPs, and is used in [IEEE 802.1ag]. Mizrahi, et al. Expires September 29, 2011 [Page 10] Internet-Draft Overview of OAM Mechanisms March 2011 The 802.1ag defines a finer distinction between Up MPs and Down MPs. An MP is a bridge interface, that is monitored by an OAM protocol either in the direction facing the network, or in the direction facing the bridge. A Down MP is an MP that receives OAM packets from, and transmits them to the direction of the network. An Up MP receives OAM packets from, and transmits them to the direction of the bridging entity. MPLS-TP has defined the terms MEP and MIP and their functional characteristics in [MPLS-TP OAM FW], similar to the terms defined by ITU-T. 3.2.4. Connectivity Verification and Continuity Checks Two distinct classes of failure management functions are used in OAM protocols, connectivity verification and continuity checks. The distinction between these terms is defined in [MPLS-TP OAM], and is used similarly in this document. Continuity checks are used to verify the liveness of a link, and are typically sent proactively, though they can be invoked on-demand as well. A connectivity verification function allows an MP to check whether it is connected to a peer MP or not. A connectivity verification (CV) protocol typically uses a CV message, followed by a CV reply that is sent back to the originator. A CV function can be applied proactively or on-demand. Connectivity verification and continuity checks are considered complementary mechanisms, and are often used in conjunction with each other. 3.2.5. Link Failures The terms Failure, Fault, and Defect are intermittently used in the standards, referring to a malfunction that can be detected by a connectivity or a continuity check. In some standards, such as [IEEE 802.1ag], there is no distinction between these terms, while in other standards each of these terms refers to a different type of malfunction. The ITU-T distinguishes between these terms in [ITU-T G.806]. The term Fault refers to an inability to perform a required action, e.g., an unsuccessful attempt to deliver a packet. The term Defect refers to an interruption in the normal operation, such as a consecutive period of time where no packets are delivered successfully. The term Mizrahi, et al. Expires September 29, 2011 [Page 11] Internet-Draft Overview of OAM Mechanisms March 2011 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. 3.2.6. Summary of OAM Terms used in the Standards Table 2 provides a comparison of the terminology used in different OAM standards. +-----------+-------------+-----------+----------------------------+ | |Maintenance |Maintenance|Link Failure Terminology | | |Point |Entity | | | |Terminology |Terminology| | +-----------+-------------+-----------+----------------------------+ |ICMPv4 Ping|-Host | | | | |-Gateway | | | + --------- + ----------- + --------- + -------------------------- + |ICMPv6 Ping| Node | | | + --------- + ----------- + --------- + -------------------------- + |BFD | System | Session |-Failure | | | | |-Session is declared down | + --------- + ----------- + --------- + -------------------------- + |LSP Ping | LSR | LSP |-Failure | | | | |-Fault = typically a local | | | | | isolated failure | + --------- + ----------- + --------- + -------------------------- + |PW VCCV |-PE | PW |-Failure | | |-LCCE | |-Fault | + --------- + ----------- + --------- + -------------------------- + |IPPM |-Host |-Path | Connectivity is indicated | | |-End system |-Measuremen| by a Boolean value. Thus, | | | | t session | a failure is referred to as| | | | | a path with a measurement | | | | | value "false". | + --------- + ----------- + --------- + -------------------------- + |ITU-T | LSR | LSP |-Fault, Defect, Failure: as | |Y.1711 | | | defined in [ITU-T G.806] | + --------- + ----------- + --------- + -------------------------- + |ITU-T |-MEP | ME |-Fault, Defect, Failure: as | |Y.1731 |-MIP | | defined in [ITU-T G.806] | | | | | | + --------- + ----------- + --------- + -------------------------- + Mizrahi, et al. Expires September 29, 2011 [Page 12] Internet-Draft Overview of OAM Mechanisms March 2011 |MPLS-TP |-End Point, |-LSP |-Fault, Defect, Failure: as | |OAM | MEP |-PW | defined in [ITU-T G.806] | | |-Intermediate|-Section | | | | Point, MIP | | | + --------- + ----------- + --------- + -------------------------- + |IEEE |-MP (Down,Up)| ME |-Failure | |802.1ag | -MEP | |-Fault | | | -MIP | |-Defect | | | -MHF | | | + --------- + ----------- + --------- + -------------------------- + |IEEE | DTE | Link |-Failure | |802.3ah | | |-Fault | +-----------+-------------+-----------+----------------------------+ Table 2 Summary of OAM Terms 4. OAM Functions 4.1. ICMP Ping ICMP provides a connectivity verification function for the Internet Protocol. The originator transmits an 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. ICMP is also used in Traceroute for path discovery. Traceroute allows a host to detect the path to a destination host, as follows: o The originator host repeatedly transmits an ICMP message to the destination host. At first, the value of the Time To Live (TTL) field in the ICMP message is 1, and is then repeatedly incremented by 1. o In turn, each router on the traversing path returns an ICMP message to the originator with an ICMP Time Exceeded error message. o Finally, the destination router replies with an ICMP Echo Reply. Mizrahi, et al. Expires September 29, 2011 [Page 13] Internet-Draft Overview of OAM Mechanisms March 2011 4.2. Bidirectional Forwarding Detection (BFD) 4.2.1. Overview While multiple OAM mechanisms have been defined for various protocols in the protocol stack, Bidirectional Forwarding Detection [BFD], defined by the IETF BFD working group, is a generic OAM mechanism that can be deployed over various encapsulating protocols, and in various medium types. The IETF has defined variants of the protocol for IP ([BFD IP], [BFD Multi]), for MPLS LSPs [BFD LSP], and for PWE3 [BFD VCCV]. BFD for MPLS-TP is currently evolving in the MPLS working group (e.g. [MPLS-TP Ping BFD]). BFD includes two main OAM functions, using two types of BFD packets: BFD Control packets, and BFD Echo packets. 4.2.2. BFD Control BFD supports a bidirectional continuity check, using BFD control packets, that are exchanged within a BFD session. BFD sessions operate in one of two modes: o Asynchronous mode: in this mode BFD control packets are sent periodically. When the receiver detects that no BFD control packet have been received during a predetermined period of time, a failure is detected. o Demand mode: in this mode, BFD control packets are sent on-demand. Upon need, a system initiates a series of BFD control packets to verify the link. BFD control packets are sent independently in each direction of the link. Each of the end-points of the monitored path maintains its own session identification, called a Discriminator, both of which are included in the BFD Control Packets that are exchanged between the end-points. At the time of session establishment, the Discriminators are exchanged between the two-end points. In addition, the transmission (and reception) rate is negotiated between the two end- points, based on information included in the control packets. These transmission rates may be renegotiated during the session. During normal operation of the session, i.e. no failures are detected, the BFD session is in the Up state. If no BFD Control packets are received during a fixed period of time, called the Detection Time, the session is declared to be Down. The detection time is a function of the negotiated transmission time, and a parameter called Detect Mult. Detect Mult determines the number of Mizrahi, et al. Expires September 29, 2011 [Page 14] Internet-Draft Overview of OAM Mechanisms March 2011 missing BFD Control packets that cause the session to be declared as Down. This parameter is included in the BFD Control packet. 4.2.3. BFD Echo The echo function is used for connectivity verification. 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. 4.3. LSP Ping The IETF MPLS working group has defined OAM for MPLS LSPs. The requirements and framework of this effort was defined in [MPLS OAM FW] and [MPLS OAM], respectively. The corresponding OAM mechanism defined, in this context, is LSP Ping [LSP Ping]. LSP Ping is based on ICMP Ping and just like its predecessor may be used in one of two modes: o "Ping" mode: In this mode LSP ping is used for end-to-end connectivity verification between two LSRs. o "Traceroute" mode: This mode is used for hop-by-hop fault localization. LSP Ping extends the basic ICMP Ping operation (of data-plane connectivity and continuity check) with functionality to verify data-plane vs. control-plane consistency for a Forwarding Equivalence Class (FEC) and also Maximum Transmission Unit (MTU) problems. The traceroute functionality may be used to isolate and localize the MPLS faults, using the Time-to-live (TTL) indicator to incrementally identify the sub-path of the LSP that is successfully traversed before the faulty link or node. It should be noted that LSP Ping does support unique identification of the LSP within an addressing domain. The identification is checked using the full FEC identification. LSP Ping is easily extensible to include additional information needed to support new functionality, by use of Type-Length-Value (TLV) constructs. The usage of TLVs is typically not easy to perform in hardware, and is thus typically handled by the control plane. LSP Ping supports both asynchronous, as well as, on-demand activation. In addition, extensions for LSP Ping are being defined for point-to-multipoint LSPs in [P2MP LSP Ping] and for MPLS Tunnels in [MPLS LSP Ping]. Mizrahi, et al. Expires September 29, 2011 [Page 15] Internet-Draft Overview of OAM Mechanisms March 2011 4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV) VCCV, as defined in [VCCV], provides end-to-end fault detection and diagnostics for PWs (regardless of the underlying tunneling technology). The VCCV switching function provides a control channel associated with each PW (based on the PW Associated Channel Header (ACH) which is defined in [PW ACH]), and allows sending OAM packets in-band with PW data (using CC Type 1: In-band VCCV). VCCV currently supports the following OAM mechanisms: ICMP Ping, LSP Ping, and BFD. ICMP and LSP Ping are IP encapsulated before being sent over the PW ACH. BFD for VCCV supports two modes of encapsulation - either IP/UDP encapsulated (with IP/UDP header) or PW-ACH encapsulated (with no IP/UDP header) and provides support to signal the AC status. The use of the VCCV control channel provides the context, based on the MPLS-PW label, required to bind and bootstrap the BFD session to a particular pseudo wire (FEC), eliminating the need to exchange Discriminator values. VCCV consists of two components: (1) signaled component to communicate VCCV capabilities as part of VC label, and (2) switching component to cause the PW payload to be treated as a control packet. VCCV is not directly dependent upon the presence of a control plane. The VCCV capability negotiation may be performed as part of the PW signaling when LDP is used. In case of manual configuration of the PW, it is the responsibility of the operator to set consistent options at both ends. 4.5. IP Performance Metrics (IPPM) 4.5.1. Overview The IPPM working group [IPPM FW] in the IETF defines common criteria and metrics for measuring performance of IP traffic. Some of the key RFCs published by this working group have defined metrics for measuring connectivity [rfc2678], delay [RFC2679, RFC 2681], and packet loss [RFC2681]. The IPPM working group has defined not only metrics for performance measurement, but also protocols that define how the measurement is carried out. The One-way Active Measurement Protocol [OWAMP] and the Two-Way Active Measurement Protocol [TWAMP] define a method and protocol for measuring delay and packet loss in IP networks. Mizrahi, et al. Expires September 29, 2011 [Page 16] Internet-Draft Overview of OAM Mechanisms March 2011 OWAMP [OWAMP] enables measurement of one-way characteristics of IP networks, such as one-way packet loss and one-way delay. For its proper operation OWAMP requires accurate time of day setting at its end points. TWAMP [TWAMP] is a similar protocol that enables measurement of two- way (round trip) characteristics. TWAMP does not require accurate time of day, and, furthermore, allows the use of a simple session reflector, making it an attractive alternative to OWAMP. OWAMP and TWAMP use two separate protocols: a Control plane protocol, and a Test plane protocol. 4.5.2. Control and Test Protocols OWAMP and TWAMP control protocols run over TCP, while the test protocols run over UDP. The purpose of the control protocols is to initiate, start, and stop test sessions, and for OWAMP to fetch results. The test protocols introduce test packets (which contain sequence numbers and timestamps) along the IP path under test according to a schedule, and record statistics of packet arrival. Multiple sessions may be simultaneously defined, each with a session identifier, and defining the number of packets to be sent, the amount of padding to be added (and thus the packet size), the start time, and the send schedule (which can be either a constant time between test packets or exponentially distributed pseudo-random). Statistics recorded conform to the relevant IPPM RFCs. OWAMP and TWAMP test traffic is designed with security in mind. Test packets are hard to detect because they are simply UDP streams between negotiated port numbers, with potentially nothing static in the packets. OWAMP and TWAMP also include optional authentication and encryption for both control and test packets. 4.5.3. OWAMP OWAMP defines the following logical roles: Session-Sender, Session- Receiver, Server, Control-Client, and Fetch-Client. The Session- Sender originates test traffic that is received by the Session- Receiver. The Server configures and manages the session, as well as returning the results. The Control-Client initiates requests for test sessions, triggers their start, and may trigger their termination. The Fetch-Client requests the results of a completed session. Multiple roles may be combined in a single host - for example, one host may play the roles of Control-Client, Fetch-Client, and Session-Sender, and a second playing the roles of Server and Session-Receiver. Mizrahi, et al. Expires September 29, 2011 [Page 17] Internet-Draft Overview of OAM Mechanisms March 2011 In a typical OWAMP session the Control-Client establishes a TCP connection to port 861 of the Server, which responds with a server greeting message indicating supported security/integrity modes. The Control-Client responds with the chosen communications mode and the Server accepts the modes. The Control-Client then requests and fully describes a test session to which the Server responds with its acceptance and supporting information. More than one test session may be requested with additional messages. The Control-Client then starts a test session and the Server acknowledges. The Session- Sender then sends test packets with pseudorandom padding to the Session-Receiver until the session is complete or until the Control- client stops the session. Once finished, the Fetch-Client sends a fetch request to the server, which responds with an acknowledgement and immediately thereafter the result data. 4.5.4. TWAMP TWAMP defines the following logical roles: session-sender, session- reflector, server, and control-client. These are similar to the OWAMP roles, except that the Session-Reflector does not collect any packet information, and there is no need for a Fetch-Client. In a typical TWAMP session the Control-Client establishes a TCP connection to port 862 of the Server, and mode is negotiated as in OWAMP. The Control-Client then requests sessions and starts them. The Session-Sender sends test packets with pseudorandom padding to the Session-Reflector which returns them with insertion of timestamps. 4.6. ITU-T Y.1711 4.6.1. Overview As mentioned above (4.3.), the IETF defined LSP Ping as an OAM mechanism for MPLS. The ITU-T has also defined an OAM protocol for MPLS, defined in recommendation [ITU-T Y.1711]. This recommendation defines mechanisms for connectivity verification and fast failure detection, as well as mechanism for reporting defects that have been identified in an LSP. MPLS OAM packets per Y.1711 are detected by a reserved MPLS label value. The reserved value is 14, and is defined in [OAM Label] as the 'OAM Alert Label'. Mizrahi, et al. Expires September 29, 2011 [Page 18] Internet-Draft Overview of OAM Mechanisms March 2011 4.6.2. Connectivity Verification (CV) The CV function is used to detect connectivity defects in an LSP. CV frames are sent proactively at a rate of 1 per second. Each frame contains the Trail-Termination Source Identifier (TTSI), indicating the identity of the transmitting LSR. The CV function can detect any of the following defect conditions. o Loss of Connectivity Verification (LOCV): A loss of connectivity is detected when no CV OAM packets are received in a period of 3 consecutive transmission periods. It should be noted that the LOCV defect is in fact loss of continuity when using the terminology defined in 3 ..2.4. o TTSI Mismatch: A TTSI mismatch is detected when a CV frame with an unexpected TTSI is received. o TTSI Mismerge: A TTSI mismerge is detected when the CV frames received in a given LSP contain some frame with an expected TTSI, and some frames with an unexpected TTSI. o Excess: An excess is detected when at least 5 CV frames are received during a period of 3 consecutive transmission periods. 4.6.3. Fast Failure Detection (FFD) The FFD function is a proactive function, used for fast detection of connectivity defects. While CV is typically sufficient for path failure detection and reporting, protection switching mechanisms typically require faster detection. FFD is very similar to CV in terms of the packet format, and the possible defect conditions, but FFD allows a configurable transmission frequency. The default transmission rate of FFD frames is 20 per second, i.e., every 50 ms, allowing fast detection for protection switching applications. 4.6.4. Forward Defect Indication (FDI) The FDI function is used by an LSR to report a defect to affected client layers, allowing them to suppress alarms about this defect. In MPLS-TP OAM this function is referred to as Client Failure Indication. FDI packets are sent at a rate of 1 per second. Mizrahi, et al. Expires September 29, 2011 [Page 19] Internet-Draft Overview of OAM Mechanisms March 2011 4.6.5. Backward Defect Indication (BDI) The BDI function is used by an LSR to inform a peer LSR about a defect condition on an LSP for which they are the end points of. In MPLS-TP OAM this function is referred to as Remote Defect Indication. BDI packets are sent at the same transmission rate as FDI. 4.7. ITU-T Y.1731 4.7.1. Overview The [ITU-T Y.1731] defines a protocol for Ethernet OAM. It is presented in this document as a reference point. Y.1731 defines various OAM functions, including continuity and connectivity verification, and functions for performance monitoring. 4.7.2. ETH-CC The Ethernet Continuity Check function is a proactive function that allows a MEP to detect loss of continuity with any of the other MEPs in the MEG. This function also allows detection of other defect conditions, such as unintended connectivity between two MEGs (also known as a mismerge). The ETH-CC function is used for one of three possible applications: fault management, performance monitoring (see 4.6.10.), and protection switching. Continuity Check Messages (CCM) are transmitted periodically at a constant rate. There are 7 possible transmission periods, from 3.33 ms to 10 min. When the ETH-CC function detects a defect, it reports one of the following defect conditions: o Loss of continuity (LOC): Occurs when at least when no CCM messages have been received from a peer MEP during a period of 3.5 times the configured transmission period. o Unexpected MEG level: The MEG level is a 3-bit number that defines the level of hierarchy of the MEG. This defect condition occurs when a CCM is received from a peer MEP with a MEG level that is lower than the expected MEG level. o Mismerge: Occurs when a CCM is received from a peer MEP with an unexpected MEG ID. o Unexpected MEP: Occurs when a CCM is received from a peer MEP with an unexpected transmitting MEP ID. Mizrahi, et al. Expires September 29, 2011 [Page 20] Internet-Draft Overview of OAM Mechanisms March 2011 o Unexpected period: Occurs when the transmission period field in the CCM does not match the expected transmission period value. 4.7.3. ETH-LB The Ethernet loopback function verifies connectivity with a peer MEP or MIP. The loopback function is performed on-demand, by sending a loopback message (LBM) to the peer MEP or MIP. The peer node then responds with a loopback reply (LBR). More precisely, it is used for one of two purposes: o Bidirectional connectivity test. o Bidirectional in-service / out-of-service test. The in-service mode refers to a test that is run under traffic, while the out-of- service test requires other traffic to be halted. 4.7.4. ETH-TST The test function is very similar to the loopback function, but is unidirectional, i.e., the ETH-TST PDUs are terminated by the receiver rather than being looped back to the sender. 4.7.5. ETH-LT The Ethernet linktrace is an on-demand function that is used for path discovery to a given target, or for locating a failure in a broken path. 4.7.6. ETH-AIS The Alarm Indication Signal indicates that a MEG should suppress alarms about a defect condition at a lower MEG level, i.e., since a defect has occurred in a lower hierarchy in the network, it should not be reported by the current node. A MEP that detects a failure periodically sends AIS messages to higher hierarchies. AIS messages are sent periodically at a recommended rate of 1 packet per second, until the defect condition is resolved. 4.7.7. ETH-LCK The lock function is used for administrative locking. A MEP can initiate administrative locking, resulting in interruption of data, e.g., for out-of-service ETH-LB or ETH-TST. Mizrahi, et al. Expires September 29, 2011 [Page 21] Internet-Draft Overview of OAM Mechanisms March 2011 A MEP that initiates an administrative locking notifies its peer MEPs to halt all relevant traffic until administrative/diagnostic condition is removed. ETH-LCK frames are used to report to higher MEG levels about the lock. The LCK frame, much like an AIS frame, indicates to the receiving MEP that it should suppress alarms about the locked link. 4.7.8. ETH-RDI The Remote Defect Indication allows the sender to indicate that it encountered a defect conditions. The receiving MEPs are then aware that there is a defect condition in the MEG. 4.7.9. ETH-APS The Y.1731 standard defines the frame format for Automatic Protection Switching frames. The protection switching operations are defined in other ITU-T standards. 4.7.10. ETH-LM The loss measurement function allows a MEP to measure the packet loss rate from/to a given MEP in the MEG. Each MEP maintains counters of transmitted and received in-profile packets to/from each of its peer MEPs. These counters are incorporated in the ETH-LM frames, allowing the MEPs to compute the packet loss rate. The ETH-LM function measures the far-end loss, referring to traffic FROM the MEP to its peer, as well as the near-end loss, referring to traffic from the peer MEP TO the local MEP. ETH-LM is performed in one of two possible modes: o Single-ended LM: in this mode loss measurement is performed on- demand. The initiator sends an LM message (LMM) to its peer MEP, and the peer responds with an LM reply (LMR). o Dual-ended LM: in this mode loss measurement is performed proactively. The continuity check message (CCM) is used for proactive LM. The LM counters are piggy-backed into the CCM, and allow proactive loss measurement. 4.7.11. ETH-DM The delay measurement function is an on-demand function that allows a MEP to measure the frame delay and frame delay variation to a peer MEP. Mizrahi, et al. Expires September 29, 2011 [Page 22] Internet-Draft Overview of OAM Mechanisms March 2011 ETH-DM can be performed in one of two modes of operation: o One-way DM: in this mode, a MEP transmits a 1DM frame containing the time of its transmission, TxTimeStampf. The receiving MEP receives the 1DM frame and records the time of reception, RxTimef. The receiving MEP can then compute the one-way delay by: RxTimef - TxTimeStampf. o Two-way DM: in this mode, a MEP transmits a delay measurement message (DMM) containing its transmission time, TxTimeStampf. The peer MEP receives the DMM and responds with a delay measurement reply (DMR). Upon receiving the DMR, the initiating MEP records the time of its reception, RxTimef, and computes the round trip delay by: RxTimef - TxTimeStampf. Each MEP maintains a time-of-day clock that is used for timestamping delay measurement frames. It should be noted that in one-way DM it is implicitly assumed that the clocks of the two peer MEPs are synchronized by a time synchronization protocol. 4.8. IEEE 802.1ag 4.8.1. Overview While the [ITU-T Y.1731] was defined in the ITU-T, the IEEE defined the [IEEE 802.1ag] as a standard for connectivity fault management in Ethernet based networks. While the two standards are to some extent overlapping, they can also be viewed as two complementary parts of a single Ethernet OAM picture. The two standards use a common packet format. There are a few differences between the two standards in terms of terminology: the term MEG level, used in Y.1731, as referred to as Maintenance Domain level in 802.1ag; the Y.1731 standard uses the term MEG, while the 802.1ag equivalent is Maintenance Association (MA). While Y.1731 defines multiple OAM functions (see section 4.6), the 802.1ag standard focuses on three main OAM functions: continuity check, loopback, and linktrace, and defines them with great detail. 4.8.2. Continuity Check See 4.6.2. 4.8.3. Loopback See 4.6.3. Mizrahi, et al. Expires September 29, 2011 [Page 23] Internet-Draft Overview of OAM Mechanisms March 2011 4.8.4. Linktrace See 4.6.5. 4.9. IEEE 802.3ah 4.9.1. Overview The [IEEE 802.3ah] defines Ethernet for the Last Mile (EFM). With respect to OAM, this standard was designed as an Ethernet link-layer OAM, for single-hop Ethernet links, allowing to monitor remote networking devices that are not managed by a centralized management system. The OAM functions in this standard are described below. 4.9.2. Remote Failure Indication This function allows a node to notify a peer about a defect in the receive path. Some physical interfaces allow unidirectional traffic, where even if one direction of the link fails, the reverse direction can still be used to convey the remote failure indication. 4.9.3. Remote Loopback The remote loopback function provides a diagnostic mode that is used to verify the link connectivity, and to measure the packet loss rate. When a bridge interface is configured to loopback mode, all incoming traffic through the interface is looped and sent back to the originator. 4.9.4. Link Monitoring Link monitoring provides an event notification function, allowing peer devices to communicate defect conditions and diagnostic information. 4.10. MPLS-TP OAM 4.10.1. Overview The MPLS working group is currently working on defining the OAM toolset that fulfill the requirements for MPLS-TP OAM. The full set of requirements for MPLS-TP OAM are defined in [MPLS-TP OAM], and include both general requirements for the behavior of the OAM mechanisms and a set of operations that should be supported by the OAM toolset. The set of mechanisms required are further elaborated in [MPLS-TP OAM FW], that describes the general architecture of the Mizrahi, et al. Expires September 29, 2011 [Page 24] Internet-Draft Overview of OAM Mechanisms March 2011 OAM system as well as giving overviews of the functionality of the OAM toolset. Some of the basic requirements for the OAM toolset for MPLS-TP are: o MPLS-TP OAM must be able to support both an IP based and non-IP based environment. If the network is IP based, i.e. IP routing and forwarding are available, then the MPLS-TP OAM toolset should rely on the IP routing and forwarding capabilities. On the other hand, in environments where IP functionality is not available, the OAM tools must still be able to operate without dependence on IP forwarding and routing. o OAM packets and the user traffic are required to be congruent (i.e. OAM packets are transmitted in-band) and there is a need to differentiate OAM packets from user-plane ones. Inherent in this requirement is the principle that MPLS-TP OAM be independent of any existing control-plane, although it should not preclude use of the control-plane functionality. 4.10.2. Generic Associated Channel In order to address the requirement for in-band transmission of MPLS- TP OAM traffic, MPLS-TP uses a Generic Associated Channel (G-ACh), defined in [G-ACh] for LSP-based OAM traffic. This mechanism is based on the same concepts as the PWE3 ACH and VCCV mechanisms. However, to address the needs of LSPs as differentiated from PW, the following concepts were defined for [G-ACh]: o An Associated Channel Header (ACH), that uses a format similar to the PW Control Word, is a 4-byte header that is added to OAM packets. o A Generic Associated Label (GAL). The GAL is a reserved MPLS label value. The reserved value is 13, and indicates the existence of the ACH immediately after it. 4.10.3. MPLS-TP OAM Toolset To address the functionality that is required of the OAM toolset, the MPLS WG conducted an analysis of the existing IETF and ITU-T OAM mechanisms and their ability to fulfill the required functionality. The conclusions of this analysis are documented in [OAM Analysis]. The MPLS working group currently plans to use a mixture of OAM mechanisms that are based on various existing standards, and adapt them to the requirements of [MPLS-TP OAM]. Some of the main building blocks of this solution are based on: Mizrahi, et al. Expires September 29, 2011 [Page 25] Internet-Draft Overview of OAM Mechanisms March 2011 o Bidirectional Forwarding Detection ([BFD], [BFD LSP]) for proactive continuity check and connectivity verification. o LSP Ping as defined in [LSP Ping] for on-demand connectivity verification. o New protocol packets, using G-ACH, to address different functionality. o Performance measurement protocols that are based on the functionality that is described in [ITU-T Y.1731]. The following sub-sections describe the OAM tools that will be defined for MPLS-TP as described in [MPLS-TP OAM FW]. 4.10.3.1. Continuity Check and Connectivity Verification Continuity Check and Connectivity Verification (CC-V) are OAM operations generally used in tandem, and compliment each other. These functions are generally run proactively, but may also be used on- demand, either due to bandwidth considerations or for diagnoses of a specific condition. Proactively [MPLS-TP OAM] 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.[MPLS-TP OAM FW] highlights the need for the CC-V messages to include unique identification of the MEG that is being monitored and the MEP that originated the message. The function, both proactively and in on-demand mode, need to be transmitted at regular rates pre-configured by the operator. 4.10.3.2. Diagnostic Tests Diagnostic testing is a protocol that allows a network to send special test data on a transport path. For example, this could be used as part of bandwidth utilization measurement. 4.10.3.3. Route Tracing [MPLS-TP OAM] defines that there is a need for functionality that would allow a path end-point to identify the intermediate and end- points of the path. This function would be used in on-demand mode. Normally, this path will be used for bidirectional PW, LSP, and sections, however, unidirectional paths may be supported only if a return path exists. Mizrahi, et al. Expires September 29, 2011 [Page 26] Internet-Draft Overview of OAM Mechanisms March 2011 4.10.3.4. Lock Instruct The Lock Instruct function is used to notify a transport path end- point of an administrative need to disable the transport path. This functionality will generally be used in conjunction with some intrusive OAM function, e.g. Performance measurement, Diagnostic testing, to minimize the side-effect on user data traffic. 4.10.3.5. Lock Reporting Lock Reporting is a function used by an end-point of a path to report to its far-end end-point that a lock condition has been affected on the path. 4.10.3.6. Alarm Reporting Alarm Reporting is a function used by an intermediate point of a path, that becomes aware of a fault on the path, to report to the end-points of the path. [MPLS-TP OAM FW] states that this may occur as a result of a defect condition discovered at a server sub-layer. This generates an Alarm Indication Signal (AIS) that continues until the fault is cleared. The consequent action of this function is detailed in [MPLS-TP OAM FW]. 4.10.3.7. Remote Defect Indication Remote Defect Indication (RDI) is used proactively by a path end- point to report to its peer end-point that a defect is detected on a bidirectional connection between them. [MPLS-TP OAM] points out that this function may be applied to a unidirectional LSP only if there a return path exists. [MPLS-TP OAM FW] points out that this function is associated with the proactive CC-V function. 4.10.3.8. Client Failure Indication Client Failure Indication (CFI) is defined in [MPLS-TP OAM] to allow the propagation information from one edge of the network to the other. The information concerns a defect to a client, in the case that the client does not support alarm notification. 4.10.3.9. Packet Loss Measurement Packet Loss Measurement is a function used to verify the quality of the service. This function indicates the ratio of packets that are not delivered out of all packets that are transmitted by the path source. Mizrahi, et al. Expires September 29, 2011 [Page 27] Internet-Draft Overview of OAM Mechanisms March 2011 There are two possible ways of determining this measurement: o Using OAM packets, it is possible to compute the statistics based on a series of OAM packets. This, however, has the disadvantage of being artificial, and may not be representative since part of the packet loss may be dependent upon packet sizes. o Sending delimiting messages for the start and end of a measurement period during which the source and sink of the path count the packets transmitted and received. After the end delimiter, the ratio would be calculated by the path OAM entity. 4.10.3.10. Packet Delay Measurement Packet Delay Measurement is a function that is used to measure one- way or two-way delay of a packet transmission between a pair of the end-points of a path (PW, LSP, or Section). Where: o One-way packet delay is the time elapsed from the start of transmission of the first bit of the packet by a source node until the reception of the last bit of that packet by the destination node. o Two-way packet delay is the time elapsed from the start of transmission of the first bit of the packet by a source node until the reception of the last bit of the loop-backed packet by the same source node, when the loopback is performed at the packet's destination node. Similarly to the packet loss measurement this could be performed in either of the two ways outlined above. 4.11. Summary of OAM Functions Table 3 summarizes the OAM functions that are supported in each of the standards that were analyzed in this section. +-----------+-------+--------+--------+-----------+-------+--------+ | Standard |Continu|Connecti|Path |Defect |Perform|Other | | |ity |vity |Discover|Indications|ance |Function| | |Check |Verifica|y | |Monitor|s | | | |tion | | |ing | | +-----------+-------+--------+--------+-----------+-------+--------+ |ICMP Ping | |Echo |Tracerou| | | | | | | |te | | | | Mizrahi, et al. Expires September 29, 2011 [Page 28] Internet-Draft Overview of OAM Mechanisms March 2011 + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |BFD |BFD |BFD | | | | | | |Control|Echo | | | | | + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |LSP Ping | |"Ping" |"Tracero| | | | | | |mode |ute" | | | | | | | |mode | | | | + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |PW VCCV | |VCCV | | | | | + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |IPPM | | | | |-Delay | | | | | | | | measur| | | | | | | | ement | | | | | | | |-Packet| | | | | | | | loss | | | | | | | | measur| | | | | | | | ement | | + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |ITU-T |-CV | | | | | | |Y.1711 |-FFD | | | | | | + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |ITU-T |ETH-CC |ETH-LB |ETH-LT |-ETH-RDI |-ETH-LM|-ETH-LCK| |Y.1731 | | | |-ETH-AIS |-ETH-DM|-ETH-APS| | | | | | | |-ETH-TST| + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |IEEE |CC |Loopback|Linktrac| | | | |802.1ag | | |e | | | | + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |IEEE | |Remote | |-Remote | | | |802.3ah | |Loopback| | Failure | | | | | | | | Indication| | | | | | | |-Link | | | | | | | | Monitoring| | | + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |MPLS-TP |CC |CV |Route |-Alarm |-LM |-Diagnos| |OAM | | |Tracing | Reporting |-DM | tic Tes| | | | | |-Client | | s | | | | | | Failure | |-Lock | | | | | | Indication| | | | | | | |-Remote | | | | | | | | Defect | | | Mizrahi, et al. Expires September 29, 2011 [Page 29] Internet-Draft Overview of OAM Mechanisms March 2011 | | | | | Indication| | | +-----------+-------+--------+--------+-----------+-------+--------+ Table 3 Summary of OAM Functions 4.12. Summary of Continuity Check Mechanisms A key element in some of the OAM standards that are analyzed in this document is the continuity check. It is thus interesting to present a more detailed comparison of the connectivity check mechanisms defined in OAM standards. Table 4 can be viewed as an extension of Table 3, but is presented separately for convenience. The table compares the OAM standards that support a continuity check. MPLS-TP is not included in the comparison, as the continuity check mechanism in MPLS-TP has not yet been defined. The "Tx Interval" column in the table specifies the period between two consequent message transmissions, while the "Source Identifier" column specifies the name of the field in the OAM packet that is used as the identifier of the transmitter. The "Error Codes" column specifies the possible error codes when the unidirectional connectivity check detects a failure. +-----------+-------+--------+---+--------+------------------------+ | |Mechani|Tx |UC/|Source | Error | | |sm |Interval|MC |Identifi| Codes | | | | | |er | | +-----------+-------+--------+---+--------+------------------------+ |BFD |BFD |Negotiat|UC |My Discr| Control Detection Time | | |Control|ed durin| |iminator| Expired | | | |g sessio| | | | | | |n | | | | + --------- + ----- + ------ + - + ------ + ---------------------- + |ITU-T |CV |CV: 1s |UC |TTSI |-Loss of CV (LOCV) | |Y.1711 |FFD |FFD: par| | |-TTSI Mismatch | | | |ameter, | | |-TTSI Mismerge | | | |default:| | |-Excess | | | |50 ms | | | | + --------- + ----- + ------ + - + ------ + ---------------------- + |ITU-T |CC |7 possib|UC/|MEP ID |-Loss of Continuity(LOC)| |Y.1731 / | |le perio|MC | |-Unexpected MEG level | |IEEE | |ds: | | |-Mismerge | |802.1ag | |3 1/3 ms| | |-Unexpected MEP | | | |10 ms | | |-Unexpected period | Mizrahi, et al. Expires September 29, 2011 [Page 30] Internet-Draft Overview of OAM Mechanisms March 2011 | | |100 ms | | | | | | |1 s | | | | | | |10 s | | | | | | |1 min | | | | | | |10 min | | | | +-----------+-------+--------+---+--------+------------------------+ Table 4 Summary of OAM Terms 5. Security Considerations There are no security implications imposed by this document. 6. IANA Considerations There are no new IANA considerations implied by this document. 7. Acknowledgments This document was prepared using 2-Word-v2.0.template.dot. 8. References 8.1. Normative References [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [LSP Ping] Kompella, K., Swallow, G., "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC 4379, February 2006. [MPLS OAM] Nadeau, T., Morrow, M., Swallow, G., Allan, D., and Matsushima, S., "Operations and Management (OAM) Requirements for Multi-Protocol Label Switched (MPLS) Networks", RFC 4377, February 2006. [MPLS OAM FW] Allan, D., Nadeau, T., "A Framework for Multi-Protocol Label Switching (MPLS) Operations and Management (OAM)", RFC 4378, February 2006. [MPLS OAM P2MP] Yasukawa, S., Farrel, A., King, D., and Nadeau, T., "Operations and Management (OAM) Requirements for Point-to-Multipoint MPLS Networks", RFC 4687, September 2006. Mizrahi, et al. Expires September 29, 2011 [Page 31] Internet-Draft Overview of OAM Mechanisms March 2011 [OAM Label] Ohta, H., "Assignment of the 'OAM Alert Label' for Multiprotocol Label Switching Architecture (MPLS) Operation and Maintenance (OAM) Functions", RFC 3429, November 2002. [MPLS-TP OAM] Vigoureux, M., Ward, D., Betts, M., "Requirements for OAM in MPLS Transport Networks", RFC 5860, May 2010. [G-ACh] Bocci, M., Vigoureux, M., Bryant, S., "MPLS Generic Associated Channel", RFC 5586, June 2009. [VCCV] Nadeau, T., Pignataro, C., "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, December 2007. [ICMPv4] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, September 1981. [ICMPv6] Conta, A., Deering, S., and M. Gupta, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", RFC 4443, March 2006. [IPPM FW] Paxson, V., Almes, G., Mahdavi, J., and Mathis, M., "Framework for IP Performance Metrics", RFC 2330, May 1998. [IPPM Con] Mahdavi, J., Paxson, V., "IPPM Metrics for Measuring Connectivity", RFC 2678, September 1999. [IPPM 1DM] Almes, G., Kalidindi, S., Zekauskas, M., "A One-way Delay Metric for IPPM", RFC 2679, September 1999. [IPPM 1LM] Almes, G., Kalidindi, S., Zekauskas, M., "A One-way Packet Loss Metric for IPPM", RFC 2680, September 1999. [IPPM 2DM] Almes, G., Kalidindi, S., Zekauskas, M., "A Round-trip Delay Metric for IPPM", RFC 2681, September 1999. [OWAMP] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and Zekauskas, M., "A One-way Active Measurement Protocol (OWAMP)", RFC 4656, September 2006. [TWAMP] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and Babiarz, J., "A Two-Way Active Measurement Protocol (TWAMP)", RFC 5357, October 2008. Mizrahi, et al. Expires September 29, 2011 [Page 32] Internet-Draft Overview of OAM Mechanisms March 2011 [BFD] Katz, D., Ward, D., "Bidirectional Forwarding Detection (BFD)", RFC 5880, June 2010. [BFD IP] Katz, D., Ward, D., "Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June 2010. [BFD Gen] Katz, D., Ward, D., "Generic Application of Bidirectional Forwarding Detection (BFD)", RFC 5882, June 2010. [BFD Multi] Katz, D., Ward, D., "Bidirectional Forwarding Detection (BFD) for Multihop Paths", RFC 5883, June 2010. [BFD LSP] Aggarwal, R., Kompella, K., Nadeau, T., and Swallow, G., "Bidirectional Forwarding Detection (BFD) for MPLS Label Switched Paths (LSPs)", RFC 5884, June 2010. [BFD VCCV] Nadeau, T., Pignataro, C., "Bidirectional Forwarding Detection (BFD) for the Pseudowire Virtual Circuit Connectivity Verification (VCCV)", RFC 5885, June 2010. [IEEE 802.1ag]"Connectivity Fault Management", December 2007. [ITU-T Y.1731]"OAM Functions and Mechanisms for Ethernet-based Networks", February 2008. [ITU-T Y.1711]"Operation & Maintenance mechanism for MPLS networks", February 2004. [IEEE 802.3ah]"Media Access Control Parameters, Physical Layers, and Management Parameters for Subscriber Access Networks", clause 57, September 2004. 8.2. Informative References [OAM Soup] Andersson, L., Van Helvoort, H., Bonica, R., Romascanu, D., Mansfield, S., " Guidelines for the use of the OAM acronym in the IETF ", work-in-progress, draft-ietf- opsawg-mpls-tp-oam-def, September, 2010. [OAM Analysis] Sprecher, N., Bellagamba, E., Weingarten, Y., "OAM functions in MPLS based transport network", work-in- progress, draft-ietf-mpls-tp-oam-analysis, January, 2011. Mizrahi, et al. Expires September 29, 2011 [Page 33] Internet-Draft Overview of OAM Mechanisms March 2011 [MPLS-TP OAM FW] Busi, I., Niven-Jenkins, B., Allan, D., " Operations, Administration and Maintenance Framework for MPLS-based Transport Networks ", work-in-progress, draft-ietf-mpls-tp-oam-framework, February, 2011. [MPLS-TP Term]Van Helvoort, H., Andersson, L., Sprecher, N., "A Thesaurus for the Terminology used in Multiprotocol Label Switching Transport Profile (MPLS-TP) drafts/RFCs and ITU-T's Transport Network Recommendations", work-in-progress, draft-ietf-mpls- tp-rosetta-stone, November, 2010. [MPLS-TP Ping BFD] Bahadur, N., Aggarwal, R., Ward, D., Nadeau, T., Sprecher, N., Weingarten, Y., "LSP-Ping and BFD encapsulation over ACH", draft-ietf-mpls-tp-lsp-ping- bfd-procedures, work-in-progress, August, 2010. [P2MP Ping] Saxena, S., Farrel, A. , Yasukawa, S., "Detecting Data Plane Failures in Point-to-Multipoint Multiprotocol Label Switching (MPLS) - Extensions to LSP Ping", work-in-progress, draft-ietf-mpls-p2mp-lsp-ping, March, 2011. [ITU-T G.806] "Characteristics of transport equipment - Description methodology and generic functionality", January 2009. Authors' Addresses Tal Mizrahi Marvell 6 Hamada St. Yokneam, 20692 Israel Email: talmi@marvell.com Nurit Sprecher Nokia Siemens Networks 3 Hanagar St. Neve Ne'eman B Hod Hasharon, 45241 Israel Email: nurit.sprecher@nsn.com Mizrahi, et al. Expires September 29, 2011 [Page 34] Internet-Draft Overview of OAM Mechanisms March 2011 Elisa Bellagamba Ericsson 6 Farogatan St. Stockholm, 164 40 Sweden Phone: +46 761440785 Email: elisa.bellagamba@ericsson.com Yaacov Weingarten Nokia Siemens Networks 3 Hanagar St. Neve Ne'eman B Hod Hasharon, 45241 Israel Phone: +972-9-775 1827 Email: yaacov.weingarten@nsn.com Mizrahi, et al. Expires September 29, 2011 [Page 35]