--- 1/draft-ietf-opsawg-oam-overview-00.txt 2010-07-12 18:12:48.000000000 +0200 +++ 2/draft-ietf-opsawg-oam-overview-01.txt 2010-07-12 18:12:48.000000000 +0200 @@ -1,18 +1,18 @@ Operations and Management Area Working Group T. Mizrahi Internet Draft Marvell -Intended status: Informational January 17, 2010 -Expires: July 2010 +Intended status: Informational July 12, 2010 +Expires: January 2011 An Overview of Operations, Administration, and Maintenance (OAM) Mechanisms - draft-ietf-opsawg-oam-overview-00.txt + draft-ietf-opsawg-oam-overview-01.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. @@ -21,151 +21,173 @@ 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 July 17, 2010. + This Internet-Draft will expire on January 12, 2011. Copyright Notice Copyright (c) 2010 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 in effect on the date of - publication of this document (http://trustee.ietf.org/license-info). - Please review these documents carefully, as they describe your rights - and restrictions with respect to this document. + Provisions Relating to IETF Documents + (http://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. Abstract Operations, Administration, and Maintenance (OAM) is a general term that refers to detecting and reporting link failures. 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................................................3 - 2. Conventions used in this document............................5 - 3. Basic Terminology...........................................5 - 3.1. Abbreviations..........................................5 - 3.2. Terminology used in OAM Standards.......................6 - 3.2.1. General Terms......................................6 - 3.2.2. OAM Maintenance Entities...........................7 - 3.2.3. OAM Maintenance Points.............................7 - 3.2.4. OAM Link Failures..................................7 - 3.2.5. Summary of OAM Terms used in the Standards..........7 - 4. OAM Functions...............................................9 - 4.1. ICMP Ping..............................................9 - 4.2. Bidirectional Forwarding Detection (BFD)................9 - 4.2.1. Overview..........................................9 - 4.2.2. BFD Control........................................9 - 4.2.3. BFD Echo.........................................10 - 4.3. LSP Ping..............................................10 - 4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV)...10 - 4.5. ITU-T Y.1711..........................................10 - 4.5.1. Overview.........................................10 - 4.5.2. Connectivity Verification (CV)....................11 - 4.5.3. Fast Failure Detection (FFD)......................11 - 4.5.4. Forward Defect Indication (FDI)...................11 - 4.5.5. Backward Defect Indication (BDI)..................12 - 4.6. ITU-T Y.1731..........................................12 - 4.6.1. Overview.........................................12 - 4.6.2. ETH-CC...........................................12 - 4.6.3. ETH-LB...........................................13 - 4.6.4. ETH-TST..........................................13 - 4.6.5. ETH-LT...........................................13 - 4.6.6. ETH-AIS..........................................13 - 4.6.7. ETH-LCK..........................................14 - 4.6.8. ETH-RDI..........................................14 - 4.6.9. ETH-APS..........................................14 - 4.6.10. ETH-LM..........................................14 - 4.6.11. ETH-DM..........................................15 - 4.7. IEEE 802.1ag..........................................15 - 4.7.1. Overview.........................................15 - 4.7.2. Continuity Check..................................16 - 4.7.3. Loopback.........................................16 - 4.7.4. Linktrace........................................16 - 4.8. IEEE 802.3ah..........................................16 - 4.8.1. Overview.........................................16 - 4.8.2. Remote Failure Indication.........................16 - 4.8.3. Remote Loopback...................................16 - 4.8.4. Link Monitoring...................................16 - 4.9. MPLS-TP OAM...........................................16 - 4.9.1. Overview.........................................16 - 4.9.2. Continuity Checks.................................17 - 4.9.3. Connectivity Verification.........................17 - 4.9.4. Diagnostic Tests..................................17 - 4.9.5. Route Tracing.....................................17 - 4.9.6. Lock Instruct.....................................17 - 4.9.7. Lock Reporting....................................17 - 4.9.8. Alarm Reporting...................................17 - 4.9.9. Remote Defect Indication..........................18 - 4.9.10. Client Failure Indication........................18 - 4.9.11. Packet Loss Measurement..........................18 - 4.9.12. Packet Delay Measurement.........................18 - 4.10. Summary of OAM Functions..............................18 - 4.11. Summary of Unidirectional Connectivity Check Mechanisms19 - 5. Security Considerations.....................................20 - 6. IANA Considerations........................................20 - 7. Acknowledgments............................................20 - 8. References.................................................21 - 8.1. Normative References...................................21 - 8.2. Informative References.................................21 + 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...........................9 + 3.2.3. OAM Maintenance Points............................10 + 3.2.4. OAM Link Failures.................................10 + 3.2.5. Summary of OAM Terms used in the Standards.........10 + 4. OAM Functions..............................................12 + 4.1. ICMP Ping.............................................12 + 4.2. Bidirectional Forwarding Detection (BFD)...............12 + 4.2.1. Overview.........................................12 + 4.2.2. BFD Control.......................................12 + 4.2.3. BFD Echo.........................................13 + 4.3. LSP Ping..............................................13 + 4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV)...13 + 4.5. IP Performance Metrics (IPPM)..........................14 + 4.5.1. Overview.........................................14 + 4.5.2. OWAMP/TWAMP Control...............................14 + 4.5.3. OWAMP/TWAMP Test..................................14 + 4.6. ITU-T Y.1711..........................................14 + 4.6.1. Overview.........................................14 + 4.6.2. Connectivity Verification (CV)....................15 + 4.6.3. Fast Failure Detection (FFD)......................15 + 4.6.4. Forward Defect Indication (FDI)...................15 + 4.6.5. Backward Defect Indication (BDI)..................15 + + 4.7. ITU-T Y.1731..........................................16 + 4.7.1. Overview.........................................16 + 4.7.2. ETH-CC...........................................16 + 4.7.3. ETH-LB...........................................17 + 4.7.4. ETH-TST..........................................17 + 4.7.5. ETH-LT...........................................17 + 4.7.6. ETH-AIS..........................................17 + 4.7.7. ETH-LCK..........................................17 + 4.7.8. ETH-RDI..........................................18 + 4.7.9. ETH-APS..........................................18 + 4.7.10. ETH-LM..........................................18 + 4.7.11. ETH-DM..........................................18 + 4.8. IEEE 802.1ag..........................................19 + 4.8.1. Overview.........................................19 + 4.8.2. Continuity Check..................................19 + 4.8.3. Loopback.........................................19 + 4.8.4. Linktrace........................................20 + 4.9. IEEE 802.3ah..........................................20 + 4.9.1. Overview.........................................20 + 4.9.2. Remote Failure Indication.........................20 + 4.9.3. Remote Loopback...................................20 + 4.9.4. Link Monitoring...................................20 + 4.10. MPLS-TP OAM..........................................20 + 4.10.1. Overview........................................20 + 4.10.2. Continuity Checks................................21 + 4.10.3. Connectivity Verification........................21 + 4.10.4. Diagnostic Tests.................................21 + 4.10.5. Route Tracing....................................22 + 4.10.6. Lock Instruct....................................22 + 4.10.7. Lock Reporting...................................22 + 4.10.8. Alarm Reporting..................................22 + 4.10.9. Remote Defect Indication.........................22 + 4.10.10. Client Failure Indication.......................22 + 4.10.11. Packet Loss Measurement.........................22 + 4.10.12. Packet Delay Measurement........................22 + 4.11. Summary of OAM Functions..............................22 + 4.12. Summary of Unidirectional Connectivity Check Mechanisms24 + 5. Security Considerations.....................................25 + 6. IANA Considerations........................................25 + 7. Acknowledgments............................................25 + 8. References.................................................25 + 8.1. Normative References...................................25 + 8.2. Informative References.................................28 1. Introduction OAM is a general term that refers to detecting and reporting link failures and defects. 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. 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. + and Maintenance, i.e., this document refers to OAM in the context of + monitoring communication links. Other aspects associated with the OAM + acronym, such as management, are not described in 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. These protocols are - listed below. + 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 typically associated with OAM, but - it is presented in this document for the sake of completeness, + 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 a family of standards that are currently being defined by the IETF. BFD is intended to be a generic OAM mechanism that can be used with various encapsulation types, and in various medium types. - o OAM for MPLS-TP is currently being defined in the MPLS workgroup. + o OAM 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. + While performance measurement is not directly related to link + failures, it is often associated with OAM. 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. For example, the emerging MPLS-TP OAM is in many ways based on [ITU-T Y.1731]. 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: @@ -177,20 +199,112 @@ 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, compared with the relevant OAM mechanisms defined by the ITU-T and IEEE. 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 | + +-----------+--------------------------------------+---------------+ + |ICMPv4 Ping| Internet Control Message Protocol | RFC 792 | + | | | | + +-----------+--------------------------------------+---------------+ + |ICMPv6 Ping| Internet Control Message Protocol | RFC 4443 | + | | (ICMPv6) for the Internet Protocol | | + | | 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 | | + +-----------+--------------------------------------+---------------+ + |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 | | | + +-----------+--------------------------------------+---------------+ + |MPLS-TP | Requirements for OAM in MPLS | RFC 5860 | + |OAM +--------------------------------------+---------------+ + | | MPLS Generic Associated Channel | RFC 5586 | + +-----------+--------------------------------------+---------------+ + |IEEE | Connectivity Fault Management |[IEEE 802.1ag] | + |CFM | | | + +-----------+--------------------------------------+---------------+ + |IEEE | Media Access Control Parameters, |[IEEE 802.3ah] | + |802.3 | Physical Layers, and Management | | + |link level | Parameters for Subscriber Access | | + |OAM | Networks | | + +-----------+--------------------------------------+---------------+ + Table 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 @@ -309,21 +424,21 @@ term Fault refers to an inability to perform a required action, e.g., an unsuccessful attempt to deliver a packet. The term Defect refers to an interruption in the normal operation, such as a consecutive period of time where no packets are delivered successfully. The term Failure refers to the termination of the required function. While a Defect typically refers to a limited period of time, a failure refers to a long period of time. 3.2.5. Summary of OAM Terms used in the Standards - Table 1 provides a comparison of the terminology used in different + 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 | | | + --------- + ----------- + --------- + -------------------------- + @@ -332,59 +447,67 @@ |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] | | | | | | + --------- + ----------- + --------- + -------------------------- + |MPLS-TP |-End Point |-LSP |-Fault, Defect, Failure: as | |OAM |-Intermediate|-PW | defined in [ITU-T G.806] | | |Point |-Section | | + --------- + ----------- + --------- + -------------------------- + |IEEE |-MEP | ME |-Failure | |802.1ag |-MIP | |-Fault | | |-MP | |-Defect | + --------- + ----------- + --------- + -------------------------- + |IEEE | DTE | Link |-Failure | |802.3ah | | |-Fault | +-----------+-------------+-----------+----------------------------+ - Table 1 Summary of OAM Terms + Table 2 Summary of OAM Terms 4. OAM Functions 4.1. ICMP Ping ICMP provides a bidirectional connectivity check 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. 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), - currently being defined by the IETF [BFD], defines a generic OAM - mechanism that can be run over various encapsulating protocols, and - in various medium types. The IETF is working on defining variants of - the protocol for IP, for MPLS LSPs, and for PWE3. + 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 unidirectional connectivity check, using BFD control packets. BFD control packets are be sent in one of two modes: o Asynchronous mode: in this mode BFD control packets are sent @@ -415,24 +538,27 @@ Discriminator, respectively. 4.2.3. BFD Echo The echo function is a bidirectional connectivity check. 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 defined an OAM mechanisms for MPLS LSPs in [LSP Ping]. LSP - ping is used to detect data plain failures in MPLS LSPs. The - transmitting LSR sends an echo request to a remote LSR, and in turn - receives an echo reply. LSP ping is used in one of two modes: + 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 + that was defined in this context is LSP Ping [LSP Ping]. LSP ping is + used to detect data plain failures in MPLS LSPs. The transmitting LSR + sends an echo request to a remote LSR, and in turn receives an echo + reply. LSP ping is 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. 4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV) VCCV, as defined in [VCCV], maintains the connectivity status of a @@ -440,31 +566,67 @@ VCCV supports two possible Connectivity Verification (CV) types, i.e., two modes of operation: o ICMP Ping: In this mode the CV is performed using an ICMP ping packet format, as defined in [ICMPv4] or [ICMPv6]. o LSP Ping: In this mode the LSP Ping packet format, as defined in [LSP Ping] is used for CV. -4.5. ITU-T Y.1711 +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. + + OWAMP and TWAMP use two separate protocols: a Control plane protocol, + and a Test plane protocol. + +4.5.2. OWAMP/TWAMP Control + + Each of these standards defines a Control protocol. This protocol is + layered over TCP, and is used to initiate measurement sessions, and + to communicate their results. + +4.5.3. OWAMP/TWAMP Test + + The Test protocol is layered over UDP, and is used to measure delay + and packet loss between the session endpoints. The Test session is + initiated by a Request/Response negotiation, followed by a set of + active test packets that are used for the measurement. + +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 [ITU-T Y.1711]. The standard defines mechanisms for connectivity verification and fast failure detection, as well as mechanism for reporting defects that have been identified in an LSP. -4.5.2. Connectivity Verification (CV) + 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'. + +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 @@ -473,57 +635,57 @@ 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. -4.5.3. Fast Failure Detection (FFD) +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. -4.5.4. Forward Defect Indication (FDI) +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. An FDI packets are sent at a rate of 1 per second. -4.5.5. Backward Defect Indication (BDI) +4.6.5. Backward Defect Indication (BDI) The BDI function is used to inform the LSR at an LSP trail termination source point about a defect condition in the forward direction of an LSP. The LSR at the LSP trail termination sink point transmits the BDI to the upstream LSR through the return path. BDI packets are sent at the same transmission rate as FDI. -4.6. ITU-T Y.1731 +4.7. ITU-T Y.1731 -4.6.1. Overview +4.7.1. Overview The [ITU-T Y.1731] is a protocol for Ethernet OAM. It is presented in this document as a reference point, since the OAM mechanisms that are currently being defined by the IETF for MPLS-TP are in many ways based on this standard. The standard defines various OAM functions, including unidirectional and bidirectional continuity check, and functions for performance monitoring. -4.6.2. ETH-CC +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. 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 @@ -542,85 +704,85 @@ 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. o Unexpected period: Occurs when the transmission period field in the CCM does not match the expected transmission period value. -4.6.3. ETH-LB +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. -4.6.4. ETH-TST +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. -4.6.5. ETH-LT +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. -4.6.6. ETH-AIS +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. -4.6.7. ETH-LCK +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. 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. -4.6.8. ETH-RDI +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. -4.6.9. ETH-APS +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. -4.6.10. ETH-LM +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. @@ -629,21 +791,21 @@ 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. -4.6.11. ETH-DM +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. 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. @@ -655,174 +817,210 @@ 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. -4.7. IEEE 802.1ag +4.8. IEEE 802.1ag -4.7.1. Overview +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. -4.7.2. Continuity Check +4.8.2. Continuity Check See 4.6.2. -4.7.3. Loopback +4.8.3. Loopback See 4.6.3. -4.7.4. Linktrace +4.8.4. Linktrace See 4.6.5. -4.8. IEEE 802.3ah +4.9. IEEE 802.3ah -4.8.1. Overview +4.9.1. Overview The [IEEE 802.3ah] defines an Ethernet link-layer OAM, for single-hop Ethernet links. The OAM functions in this standard are described below. -4.8.2. Remote Failure Indication +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. -4.8.3. Remote Loopback +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. -4.8.4. Link Monitoring +4.9.4. Link Monitoring Link monitoring provides an event notification function, allowing peer devices to communicate defect conditions and diagnostic information. -4.9. MPLS-TP OAM +4.10. MPLS-TP OAM -4.9.1. Overview +4.10.1. Overview - The MPLS-TP is currently working on defining the OAM requirements and - mechanisms for MPLS-TP. The requirements of MPLS-TP OAM are defined - in [MPLS-TP OAM], and are described below. It is noted that these - requirements are in many ways similar to the requirement of Ethernet - OAM, as defined in [ITU-T Y.1731]. + The MPLS working group is currently working on defining the OAM + requirements and mechanisms for MPLS-TP. The requirements of MPLS-TP + OAM are defined in [MPLS-TP OAM], and are described below. -4.9.2. Continuity Checks + MPLS-TP OAM traffic uses a Generic Associated Channel (G-ACh), + defined in [G-ACh]. This standard defines that MPLS-TP OAM traffic + uses: + + o An Associated Channel Header (ACH), also known as a Control Word + in the PWE3 terminology, 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 identifies the packet as an + MPLS-TP OAM packet. A GAL indicates the existence of the ACH + immediately after it. + + The analysis in [OAM Analysis] discusses various OAM mechanism that + were considered in order to satisfy the requirements in [MPLS-TP + OAM]. The MPLS working group currently plans to use a mixture of OAM + mechanisms that are based on various existing standards, and adapt + them to the requirements of [MPLS-TP OAM]. Some of the main building + blocks of this solution are based on: + + o Bidirectional Forwarding Detection ([BFD], [BFD LSP]) for + proactive connectivity verification. + + o LSP Ping as defined in [LSP Ping] for on-demand connectivity + verification. + + o Y.1731 per the [ITU-T Y.1731], mainly for performance measurement. + + The requirements of MPLS-TP OAM are summarized below. + +4.10.2. Continuity Checks The continuity check is a proactive function that allows an End Point to determine whether or not it receives traffic from its peer End Points. -4.9.3. Connectivity Verification +4.10.3. Connectivity Verification The connectivity verification is a function that allows an End Point to verify its connectivity to a peer node. The connectivity check is performed by sending a connectivity verification PDU to the peer node, and receiving a reply within an expected time frame. This function can be performed proactively or on-demand. -4.9.4. Diagnostic Tests +4.10.4. Diagnostic Tests This function allows an End Point to perform an on-demand test, e.g., for bandwidth measurement. -4.9.5. Route Tracing +4.10.5. Route Tracing This on-demand function is used for path discovery and for locating link failures. -4.9.6. Lock Instruct +4.10.6. Lock Instruct The lock instruct function allows an End Point to instruct its peers to enter an administrative status where all traffic is halted except the test traffic and OAM PDUs. -4.9.7. Lock Reporting +4.10.7. Lock Reporting This function allows an Intermediate Point to report to an End Point about a lock condition. -4.9.8. Alarm Reporting +4.10.8. Alarm Reporting This function allows an Intermediate Point to report to an End Point about a defect condition. -4.9.9. Remote Defect Indication +4.10.9. Remote Defect Indication This is a proactive function that allows the sender to indicate that it encountered a defect conditions. -4.9.10. Client Failure Indication +4.10.10. Client Failure Indication This function allows the MPLS-TP network to relay information about a fault condition in a client network, allowing the failure indication to propagate from end to end over the MPLS-TP network. -4.9.11. Packet Loss Measurement +4.10.11. Packet Loss Measurement This function measures the packet loss ratio between two peer End Points. It can be performed proactively or on-demand. -4.9.12. Packet Delay Measurement +4.10.12. Packet Delay Measurement This function measures the frame delay between two peer End Points. Two modes of operation are supported, one-way DM, and two-way DM. -4.10. Summary of OAM Functions +4.11. Summary of OAM Functions - Table 2 summarizes the OAM functions that are supported in each of + Table 3 summarizes the OAM functions that are supported in each of the standards that were analyzed in this section. +-----------+-------+--------+--------+-----------+-------+--------+ | Standard |Unidire|Bidirect|Path |Defect |Perform|Other | | |ctional|ional |Discover|Indications|ance |Function| | |Connect|Connecti|y | |Monitor|s | | |ivity |vity | | |ing | | | |Check |Check | | | | | +-----------+-------+--------+--------+-----------+-------+--------+ |ICMP Ping | | Echo | | | | | + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |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 | | | | + --------- + ----- + ------ + ------ + --------- + ----- + ------ + @@ -834,29 +1032,29 @@ + --------- + ----- + ------ + ------ + --------- + ----- + ------ + |MPLS-TP |CC |CV |Route |-Alarm |-LM |-Diagnos| |OAM | | |Tracing | Reporting |-DM | tic Tes| | | | | |-Client | | s | | | | | | Failure | |-Lock | | | | | | Indication| | | | | | | |-Remote | | | | | | | | Defect | | | | | | | | Indication| | | +-----------+-------+--------+--------+-----------+-------+--------+ - Table 2 Summary of OAM Functions + Table 3 Summary of OAM Functions -4.11. Summary of Unidirectional Connectivity Check Mechanisms +4.12. Summary of Unidirectional Connectivity Check Mechanisms A key element in some of the OAM standards that are analyzed in this document is the unidirectional connectivity check. It is thus interesting to present a more detailed comparison of the connectivity - check mechanisms defined in OAM standards. Table 3 can be viewed as - an extension of Table 2, but is presented separately for convenience. + 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 unidirectional connectivity 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. @@ -881,21 +1079,21 @@ |Y.1731 / | |le perio|MC | |-Unexpected MEG level | |IEEE | |ds: | | |-Mismerge | |802.1ag | |3 1/3 ms| | |-Unexpected MEP | | | |10 ms | | |-Unexpected period | | | |100 ms | | | | | | |1 s | | | | | | |10 s | | | | | | |1 min | | | | | | |10 min | | | | +-----------+-------+--------+---+--------+------------------------+ - Table 3 Summary of OAM Terms + 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 @@ -906,67 +1104,142 @@ 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. + + [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. + + [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 - [MPLS-TP OAM] Vigoureux, M., Ward, D., Betts, M., "Requirements for - OAM in MPLS Transport Networks", draft-ietf-mpls-tp- - oam-requirements, August 2009. - - [BFD] Katz, D., Ward, D., "Bidirectional Forwarding - Detection", draft-ietf-bfd-base, February 2009. - - [P2MP Ping] Farrel, A. , Yasukawa, S., "Detecting Data Plane - Failures in Point-to-Multipoint Multiprotocol Label - Switching (MPLS) - Extensions to LSP Ping", draft- - ietf-mpls-p2mp-lsp-ping, August 2009. + [P2MP Ping] Saxena, S., Farrel, A. , Yasukawa, S., "Detecting Data + Plane Failures in Point-to-Multipoint Multiprotocol + Label Switching (MPLS) - Extensions to LSP Ping", + draft-ietf-mpls-p2mp-lsp-ping, March 2010. - [OAM Soup] Betts, M., Van Helvoort, H., Bonica, R., Romascanu, D., - "The OAM Acronym Soup", draft-ietf-opsawg-mpls-tp-oam- - def, September 2009. + [OAM Soup] Andersson, L., Van Helvoort, H., Bonica, R., Romascanu, + D., Mansfield, S., "The OAM Acronym Soup", draft-ietf- + opsawg-mpls-tp-oam-def, June 2010. [ITU-T G.806] "Characteristics of transport equipment - Description methodology and generic functionality", January 2009. [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", draft-ietf-mpls-tp-rosetta-stone, - June 2009. + May 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, March 2010. + + [OAM Analysis] Sprecher, N., Bellagamba, E., Weingarten, Y., "MPLS-TP + OAM Analysis", draft-ietf-mpls-tp-oam-analysis, July + 2010. Authors' Addresses Tal Mizrahi Marvell Email: talmi@marvell.com