MPLS Working Group I. Busi (Ed) Internet Draft Alcatel-Lucent Intended status: Informational Expires: April 2009 B. Niven-Jenkins (Ed) BT October 27, 2008 MPLS-TP OAM Framework and Overview draft-busi-mpls-tp-oam-framework-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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 April 27, 2009. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract Multi-Protocol Label Switching (MPLS) Transport Profile (MPLS-TP) is based on a profile of the MPLS and pseudowire (PW) procedures as Busi et al. Expires April 27, 2009 [Page 1] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 specified in the MPLS Traffic Engineering (MPLS-TE), pseudowire (PW) and multi-segment PW (MS-PW) architectures complemented with additional Operations, Administration and Maintenance (OAM) procedures for fault, performance and protection-switching management for packet transport applications that do not rely on the presence of a control plane. This document provides a framework for supporting the MPLS-TP OAM requirements .[10] in a manner that admits a comprehensive set of OAM procedures. 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 RFC 2119 .[1]. Table of Contents 1. Introduction...................................................3 1.1. Contributing Authors......................................3 1.2. Terminology...............................................3 1.3. Definitions...............................................4 2. Functional Components..........................................4 2.1. Maintenance Entity........................................5 2.2. Maintenance End Points (MEPs).............................6 2.3. Maintenance Intermediate Points (MIPs)....................6 2.4. Server MEPs...............................................6 3. Reference Model................................................7 3.1. MPLS-TP Section Monitoring................................9 3.2. MPLS-TP LSP End-to-End Monitoring........................10 3.3. MPLS-TP LSP Tandem Connection Monitoring.................11 3.4. MPLS-TP PW Monitoring....................................12 3.5. MPLS-TP MS-PW Tandem Connection Monitoring...............12 4. OAM Functions for pro-active monitoring.......................13 4.1. Continuity Check and Connectivity Verification...........13 4.1.1. Applications for proactive CC & CV function.........15 4.2. Remote Defect Indication.................................15 4.2.1. Configuration considerations........................15 4.2.2. Applications for Remote Defect Indication...........16 4.3. Alarm Suppression........................................16 4.4. Lock Indication..........................................17 4.5. Packet Loss Measurement..................................17 4.6. Client Signal Fail.......................................17 5. OAM Functions for on-demand monitoring........................17 5.1. Continuity Check and Connectivity Verification...........17 5.1.1. Configuration considerations........................18 Busi et al. Expires April 27, 2009 [Page 2] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 5.2. Packet Loss Measurement..................................18 5.3. Diagnostic Test..........................................18 5.4. Trace routing............................................18 5.5. Packet Delay Measurement.................................18 6. OAM Protocols Overview........................................18 7. Security Considerations.......................................18 8. IANA Considerations...........................................19 9. Acknowledgments...............................................19 10. References...................................................19 10.1. Normative References....................................19 10.2. Informative References..................................20 Authors' Addresses...............................................20 Contributing Authors' Addresses..................................20 Intellectual Property Statement..................................21 Disclaimer of Validity...........................................22 1. Introduction As noted in the architecture for MPLS-TP .[8] the overall architecture framework for MPLS-TP is based on a profile of the MPLS and PW procedures as specified in the MPLS-TE and (MS-)PW architectures defined in RFC 3031 .[2], RFC 3985 .[5] and .[6] complemented with additional OAM procedures for fault, performance and protection-switching management for packet transport applications that do not rely on the presence of a control plane. In line with .[11], existing MPLS OAM mechanisms will be used wherever possible and new OAM mechanisms will be defined only where existing mechanisms are not sufficient to meet the requirements. The MPLS-TP OAM framework must satisfy the MPLS-TP OAM requirements . [10] in a manner that provides for a comprehensive set of OAM procedures. In this regard, it is similar to existing SONET/SDH and OTH OAM mechanisms (e.g. .[12]). 1.1. Contributing Authors Italo Busi, Ben Niven-Jenkins, Annamaria Fulignoli, Enrique Hernandez-Valencia, Lieven Levrau, Dinesh Mohan, Vincenzo Sestito, Nurit Sprecher, Huub van Helvoort, Martin Vigoureux, Yaacov Weingarten 1.2. Terminology LME LSP Maintenance Entity Busi et al. Expires April 27, 2009 [Page 3] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 ME Maintenance Entity MEP Maintenance End Point MIP Maintenance Intermediate Point PME PW Maintenance Entity SME Section Maintenance Entity TCME Tandem Connection Maintenance Entity TPME Tandem PW Maintenance Entity 1.3. Definitions MPLS Section: to be added in a future revision of this document. OAM flow: to be added in a future revision of this document. Tandem Connection: A tandem connection corresponds to a segment of a path. This may be either a segment of an LSP (i.e. a sub-path), or one or more segment(s) of a PW. 2. Functional Components MPLS-TP OAM operates in the context of Maintenance Entities (MEs). A Maintenance Entity can be viewed as the association of two (or more) Maintenance End Points (MEPs), see below. The MEPS that form an ME should be configured and managed to limit the OAM responsibilities of an OAM flow within a network or sub-network in the specific layer network that is being monitored and managed. Each OAM flow is associated to a unique ME. Each MEP within an ME resides at the boundaries of that ME. An ME may also include a set of zero or more Maintenance Intermediate Points (MIPs), which reside within the Maintenance Entity. A MEP is capable of initiating and terminating OAM messages for fault management and performance monitoring. A MIP is capable of generating OAM messages only in reaction to received OAM packets. This functional model defines the relationships between all OAM entities from a maintenance perspective, to allow each Maintenance Busi et al. Expires April 27, 2009 [Page 4] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 Entity to monitor and manage the layer network under its responsibility and easily localize problems. MEPs and MIPs are configured either via the management plane and/or the control plane, and they are associated with a particular Maintenance Entity. 2.1. Maintenance Entity A Maintenance Entity can be viewed as the association of two (or more) Maintenance End Points (MEPs). The MEPs that form an ME should be configured and managed to limit the OAM responsibilities of an OAM flow within a network or sub-network, or a transport path or segment, in the specific layer network that is being monitored and managed. Any maintenance point in between the two MEPs is a Maintenance Intermediate Points (MIP). A Maintenance Entity may be defined to monitor and manage bi- directional or unidirectional point-to-point connectivity or point- to-multipoint connectivity in an MPLS-TP layer network. MPLS-TP OAM functions are designed to be applied either on an end-to- end basis, e.g., between the LERs of a given LSP or T-PEs of a given PW, or on a per tandem connection basis, e.g., between any LER/LSR of a given LSP or any T-PE/S-PE of a given PW. The end points of a tandem connection are MEPs because the tandem connection is by definition a Maintenance Entity. Therefore, in the context of MPLS-TP LSP or PW Maintenance Entity (defined below) LERs and T-PEs can be MEPs while LSRs and S-PEs can be MIPs. In the case of Tandem Connection Maintenance Entity (defined below), LSRs and S-PEs can be either MEPs or MIPs. The following properties apply to all MPLS-TP MEs: o OAM entities can be nested but not overlapped. o Each OAM flow is associated to a unique Maintenance Entity. o OAM packets are subject to the same forwarding treatment (e.g. fate share) as the data traffic, but they can be distinguished from the data traffic using the GAL and GE-ACH constructs .[9] for LSP and the PW-ACH construct .[6] for (MS-)PW. Busi et al. Expires April 27, 2009 [Page 5] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 2.2. Maintenance End Points (MEPs) Maintenance End Points (MEPs) are the end points of a pre-configured (through the management or control planes) ME. MEPs are responsible for activating and controlling all of the OAM functionality for the ME. A MEP may initiate an OAM packet to be transferred to its corresponding MEP, or to an intermediate MIP that is part of the ME. A MEP terminates all the OAM packets that it receives corresponding to its ME and does not forward them further along the path. All OAM packets coming to a MEP source are tunnelled via label stacking and are not processed within the ME as they belong either to the client network layers or to an higher TCM level. A MEP in a tandem connection is not coincident with the termination of the MPLS-TP transport path (LSP or PW), though it can monitor its connectivity (e.g. count packets). A MEP of an MPLS-TP network transport path is coincident with transport path termination and monitors its connectivity (e.g. count packets). MPLS-TP MEP notifies a fault indication to the MPLS-TP client layer network. 2.3. Maintenance Intermediate Points (MIPs) A Maintenance Intermediate Point (MIP) is a point between the two MEPs in an ME that is capable of reacting to some OAM packets and forwarding all OAM packets while ensuring fate sharing with data plane packets. A MIP belongs to only one ME. A MIP does not initiate OAM packets, but may be addressed by OAM packets initiated by one of the MEPs of the ME. A MIP can generate OAM packets only in reaction to OAM packets that are sent on the ME it belongs to. MIPs are unaware of any OAM flows running between MEPs or between MEPs and other MIPs. MIPs can only receive and process OAM packets addressed to the MIP itself. A MIP takes no action on the MPLS-TP transport path. 2.4. Server MEPs A server MEP is a MEP of an ME that is defined in a layer network below the MPLS-TP layer network being referenced. A server MEP Busi et al. Expires April 27, 2009 [Page 6] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 coincides with either a MIP or a MEP in the client (MPLS-TP) layer network. For example, a server MEP can be either: o A termination point of a physical link (e.g. 802.3), an SDH VC or OTH ODU for the MPLS-TP Section layer network, defined in section .3.1. ; o An MPLS-TP Section MEP for MPLS-TP LSPs, defined in section .3.2. ; o An MPLS-TP LSP MEP for MPLS-TP PWs, defined in section .3.4. ; o An MPLS-TP TCM MEP for higher-level TCMs, defined in sections . 3.3. and .3.5. The server MEP can run appropriate OAM functions for fault detection, and notifies a fault indication to the MPLS-TP layer network. 3. Reference Model The reference model for MPLS-TP OAM framework builds upon the concept of an ME, and its associated MEPs and MIPs, to support the functional requirements specified in .[10]. The following MPLS-TP MEs are specified in this document: o A Section Maintenance Entity (SME), allowing monitoring and management of MPLS-TP Sections (between MPLS LSRs). o A LSP Maintenance Entity (LME), allowing monitoring and management of an end-to-end LSP (between LERs). o A PW Maintenance Entity (PME), allowing monitoring and management of an end-to-end SS/MS-PWs (between T-PEs). o An LSP Tandem Connection Maintenance Entity (TLME), allowing monitoring and management of an LSP Tandem Connection (or LSP Segment) between any LER/LSR along the LSP. o A MS-PW Tandem Connection Maintenance Entity (TPME), allows monitoring and management of a SS/MS-PW Tandem Connection (or PW Segment) between any T-PE/S-PE along the (MS-)PW. The MEs specified in this MPLS-TP framework are intended to be compliant with the architecture framework for MS-PWs .[7] and MPLS LSPs .[2]. Busi et al. Expires April 27, 2009 [Page 7] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 Native |<-------------------- PW15 --------------------->| Native Layer | | Layer Service | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | Service (AC1) V V LSP V V LSP V V LSP V V (AC2) +----+ +-+ +----+ +----+ +-+ +----+ +----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+ | | | |=========| |=========| |=========| | | | | CE1|--------|........PW1........|...PW3...|........PW5........|-------|CE2 | | | | |=========| |=========| |=========| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ |<- Subnetwork 123->| |<- Subnetwork XYZ->| .------------------- PW15 PME -------------------. .----- PW1 TPME ----. .---- PW5 TPME -----. .---------. .---------. PSN13 LME PSNXZ LME .--. .--. .--------. .--. .--. Sec12 SME Sec23 SME Sec3X SME SecXY SME SecYZ SME TPE1: Terminating Provider Edge 1 SPE2: Switching Provider Edge 3 TPEX: Terminating Provider Edge X SPEZ: Switching Provider Edge Z .---. ME . MEP ==== LSP .... PW Figure 1: Reference Model for the MPLS-TP OAM Framework Figure 1 depicts a high-level reference model for the MPLS-TP OAM framework. The figure depicts portions of two MPLS-TP enabled subnetworks, Subnetwork 123 and Subnetwork XYZ. In Subnetwork 123, LSR 1 is adjacent to LSR 2 via the MPLS Section Sec12 and LSR2 is adjacent to LSR3 via the MPLS Section Sec23. Similarly, In Subnetwork XYZ, LSR X is adjacent to LSR Y via the MPLS Section SecXY and LSR Y is adjacent to LSR Z via the MPLS Section SecYZ. In addition, LSR 3 is adjacent to LSR X via the MPLS Section 3X. Figure 1 also shows a bi-directional MS-PW (PW15) between AC1 on LSR 1 (TPE1) and AC2 on LSR Z (TPEZ). The MS-PW consists of 3 bi- directional PW Segments: 1) PW Segment 1 (PW1) between LSR 1 (TPE1) and LSR 3 (SPE3) via the bi-directional PSN13 LSP, 2) PW Segment 3 (PW3) between LSR 3 (SPE3) and LSR X (SPEX), and 3) PW Segment 5 Busi et al. Expires April 27, 2009 [Page 8] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 (PW5) between LSR X (SPEX) and LSR Z (TPEZ) via the bi-directional PSNXZ LSP. The MPLS-TP OAM procedures that apply to an instance of given ME are expected to operate independently from procedures on other instances of the same ME and certainly of other MEs. Yet, this does not preclude that multiple MEs may be affected simultaneously by the same network condition, for example, a fiber cut event. The subsections below define the MEs specified in this MPLS-TP OAM architecture framework document. Unless otherwise stated, all references to subnetworks, LSRs, MPLS Sections, LSP, pseudowires and MEs in this Section are made in relation to those shown in Figure 1. 3.1. MPLS-TP Section Monitoring An MPLS-TP Section ME (SME) is an MPLS-TP maintenance entity intended to monitor the forwarding behaviour of an MPLS Section as defined in .[9]. An SME may be configured on any MPLS section. SME OAM packets fate share with the user data packets sent over the monitored MPLS Section. An SME is intended to be deployed for applications where it is preferable to monitor the link between the topologically adjacent MPLS (and MPLS-TP enabled) LSRs rather than monitoring the individual LSP or PW segments traversing the MPLS Section. A representative application is collecting link-level PM statistics at the node-to- node interfaces (NNI) in MPLS-TP sub-network domains. |<-------------------- PW15 --------------------->| | | | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | V V LSP V V LSP V V LSP V V +----+ +-+ +----+ +----+ +-+ +----+ +----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+ | | AC1 | |=========| |=========| |=========| | AC2 | | | CE1|--------|........PW1........|...PW3...|........PW5........|-------|CE2 | | | | |=========| |=========| |=========| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ .--. .--. .--------. .--. .--. Sec12 SME Sec23 SME Sec3X SME SecXY SME SecYZ SME Figure 2: Example of MPLS-TP Section MEs (SME) Busi et al. Expires April 27, 2009 [Page 9] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 Figure 2 shows 5 Section MEs configured in the path between AC1 and AC2: 1) Sec12 ME associated with the MPLS Section between LSR 1 and LSR 2, 2) Sec23 ME associated with the MPLS Section between LSR 2 and LSR 3, 3) Sec3X ME associated with the MPLS Section between LSR 3 and LSR X, 4) SecXY ME associated with the MPLS Section between LSR X and LSR Y, and 5) SecYZ ME associated with the MPLS Section between LSR Y and LSR Z. 3.2. MPLS-TP LSP End-to-End Monitoring An MPLS-TP LSP ME (LME) is an MPLS-TP maintenance entity intended to monitor the forwarding behaviour of an end-to-end LSP between two (e.g., a point-to-point LSP) or more (e.g., a point-to-multipoint LSP) LERs. An LME may be configured on any MPLS LSP. LME OAM packets fate share with user data packets sent over the monitored MPLS LSP. An LME is intended to be deployed in scenarios where it is desirable to monitor the forwarding behaviour of an entire LSP between a pair of MPLS LERs, rather than, say, monitoring individual PWs. A representative application is collecting PM statistics of PSN LSP that is being used to provide a "tunnelling services" for a number of other LSPs. |<-------------------- PW15 --------------------->| | | | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | V V LSP V V LSP V V LSP V V +----+ +-+ +----+ +----+ +-+ +----+ +----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+ | | AC1 | |=========| |=========| |=========| | AC2 | | | CE1|--------|........PW1........|...PW3...|........PW5........|-------|CE2 | | | | |=========| |=========| |=========| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ .---------. .---------. PSN13 LME PSNXZ LME Figure 3: Examples of MPLS-TP LSP MEs (LME) Figure 3 depicts 2 LMEs configured in the path between AC1 and AC2: 1) the PSN13 LME between LER 1 and LER 3, and 2) the PSNXZ LME between LER X and LER Y. Busi et al. Expires April 27, 2009 [Page 10] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 3.3. MPLS-TP LSP Tandem Connection Monitoring An MPLS-TP LSP Tandem Connection Monitoring ME (TLME) is an MPLS-TP maintenance entity intended to monitor the forwarding behaviour of an LSP Segment between a given pair of LSRs. Multiple TLME MAY BE configured on any LSP Segment. The LSR may or may not be immediately adjacent at the MPLS layer. TLME OAM packets fate share with the user data packets sent over the monitored LSP segment. A TLME can be defined between the following entities: o LER and any LSR of a given LSP. o Any two LSRs of a given LSP. A TLME is intended to be deployed in scenarios where it is preferable to monitor the behaviour of a segment of an LSP rather than the entire LSP itself. A representative application is when there is a need to monitor a segment of an LSP that extends beyond the administrative boundaries of an MPLS-TP enabled administrative domain. |<--------------------- PW15 -------------------->| | | | |<--------------PSN1Z LSP-------------->| | | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | V V S-LSP V V S-LSP V V S-LSP V V +----+ +-+ +----+ +----+ +-+ +----+ +----+ | PE1| | | | PB3| | PBX| | | | PEZ| +----+ | | AC1 | |=======================================| | AC2 | | | CE1|--------|......................PW15.......................|-------|CE2 | | | | |=======================================| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ .--------. .---------. PSN13 TLME PSNXZ TLME PB: Provider Border LSR Figure 4: MPLS-TP LSP Tandem Conection Monitoring ME (TLME) Figure 4 depicts a variation of the reference model in Figure 1 where there is an end-to-end PSN LSP (PSN1Z LSP) between PE1 and PEZ. PSN1Z LSP consists of, at least, three stitched LSP Segments: PSN13, PSN3X and PSNXZ. In this scenario there are two separate TLMEs configured to monitor the forwarding behaviour of the PSN1Z LSP: 1) a TLME Busi et al. Expires April 27, 2009 [Page 11] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 monitoring the PSN13 LSP Segment on Subnetwork 123 (PSN13 TLME), and 2) a TLME monitoring the PSNXZ LSP Segment on Subnetwork XYZ (PSNXZ TLME). 3.4. MPLS-TP PW Monitoring An MPLS-TP PW ME (PME) is an MPLS-TP maintenance entity intended to monitor the end-to-end forwarding behaviour of a SS-PW or MS-PW between a pair of T-PEs. A PME MAY be configured on any SS-PW or MS- PW. PME OAM packets fate share with the user data packets sent over the monitored PW. A PME is intended to be deployed in scenarios where it is desirable to monitor the forwarding behaviour of an entire PW between a pair of MPLS-TP enabled T-PEs rather than monitoring the LSP aggregating multiple PWs between PEs. A representative application is on either SS-PW or MS-PW used to emulate traffic for which an SLA with QoS commitments may apply (e.g., an emulated DS1/E1 or the emulated CBR connection of an ATM VCC/VPC). |<-------------------- PW15 --------------------->| | | | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | V V LSP V V LSP V V LSP V V +----+ +-+ +----+ +----+ +-+ +----+ +----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+ | | AC1 | |=========| |=========| |=========| | AC2 | | | CE1|--------|........PW1........|...PW3...|........PW5........|-------|CE2 | | | | |=========| |=========| |=========| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ .---------------------PW15 PME--------------------. Figure 5: MPLS-TP PW ME (PME) Figure 5 depicts a MS-PW (PW15) consisting of three segments: PW1, PW3 and PW5 and its associated end-to-end PME (PW15 PME). 3.5. MPLS-TP MS-PW Tandem Connection Monitoring An MPLS-TP MS-PW Tandem Connection Monitoring ME (TPME) is an MPLS-TP maintenance entity intended to monitor the forwarding behaviour of one or more MS-PW segments between a given pair of PEs. Multiple TPMEs MAY be configured on any sub-path of a MS-PW. The PEs may or may not be immediately adjacent at the MS-PW layer. TPME OAM packets Busi et al. Expires April 27, 2009 [Page 12] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 fate share with the user data packets sent over the monitored MS-PW Segment. A TPME can be defined between the following entities: o T-PE and any S-PE of a given MS-PW o Any two S-PEs of a given MS-PW. It can span several PW segments. A TPME is intended to be deployed in scenarios where it is preferable to monitor the behaviour of a segment of a MS-PW rather than the entire end-to-end PW itself. A representative application is to collect PM statistics for the MS-PW Segment within a given network domain of an inter-domain PW. |<-------------------- PW15 --------------------->| | | | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | V V LSP V V LSP V V LSP V V +----+ +-+ +----+ +----+ +-+ +----+ +----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+ | | AC1 | |=========| |=========| |=========| | AC2 | | | CE1|--------|........PW1........|...PW3...|........PW5........|-------|CE2 | | | | |=========| |=========| |=========| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ .-----PW1 TPME------. .------PW5 TPME------. Figure 6: MPLS-TP MS-PW Tandem Connection Monitoring (TPME) Figure 6 depicts the same MS-PW (PW15) between AC1 and AC2 as in Figure 5. In this scenario there are two separate TPMEs configured to monitor the forwarding behaviour of PW15: 1) a TPME monitoring the PW1 MS-PW Segment on Subnetwork 123 (PW1 TPME), and 2) a TPME monitoring the PW4 MS-PW Segment on Subnetwork XYZ with (PW5 TPME). 4. OAM Functions for pro-active monitoring 4.1. Continuity Check and Connectivity Verification Proactive Continuity Check (CC) and Connectivity Verification (CV) function is used to detect loss of continuity (LOC), unintended connectivity between two MEs (e.g. mismerging or misconnection) as well as unintended connectivity within the ME with an unexpected MEP. Busi et al. Expires April 27, 2009 [Page 13] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 Proactive CC & CV is based upon the generation of OAM CC/CV packets, carrying a unique ME identifier, at a regular configurable timing rate and the detection of LOC when these packets do not arrive. If the received ME identifier does not match the expected ME identifier, a connectivity defect has occurred. The default CC/CV transmission periods are application dependent (see section .4.1.1. ) For statically provisioned connections, the transmission period and the ME identifier are statically configured at both MEPs. For dynamically established connections, the transmission period and the ME identifier are signaled via the control plane. In a bidirectional point-to-point connection, when a MEP is enabled to generate CC/CV packets with a configured transmission period, it also expects to receive CC/CV packets from its peer MEP with the same transmission period. In a unidirectional connection (point-to-point or point-to-multipoint), only the source MEP is enabled to generate packets with CC/CV information. This MEP does not expect to receive any packets with CC/CV information from its peer MEPs in the ME. MIPs as well as intermediate nodes not supporting MPLS-TP OAM are transparent to the pro-active CC/CV information and forward pro- active CC/CV packets as regular data packets. When CC & CV is enabled, a MEP periodically transmits CC/CV packets with frequency of the configured transmission period. If no CC/CV packets from a peer MEP are received within the interval equal to 3.5 times the transmission period, loss of continuity (LOC) defect with the peer MEP is detected. When a CC/CV packet is received, a MEP is capable to detect a mis-connectivity defect (e.g. mismerge or misconnection) with another ME when either: o It is enabled to received CC/CV packets and the received CC/CV packet carries an incorrect ME identifier o It is not enabled to receive CC/CV packets If CC/CV packets are received with a transmission period different than expected, CC/CV period mis-configuration defect is detected. A receiving MEP notifies the equipment fault management process when it detects the above defect conditions. Busi et al. Expires April 27, 2009 [Page 14] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 4.1.1. Applications for proactive CC & CV function CC & CV is applicable for fault management, performance monitoring, or protection switching applications. o Fault Management: default transmission period is 1s (i.e. transmission rate of 1 packet/second) o Performance Monitoring: default transmission period is 100ms (i.e. transmission rate of 10 packets/second) o Protection Switching: in order to achieve sub-50ms recovery time the default transmission period is 3.33ms (i.e. transmission rate of 300 packets/second) although a transmission period of 10ms can also be used. In some cases, when a slower recovery time is acceptable, it is also possible to relax the transmission period. 4.2. Remote Defect Indication The Remote Defect Indication (RDI) is an indicator that is transmitted by a MEP to communicate to its peer MEPs that a signal fail condition exists. RDI is only used for bidirectional connections and is associated with proactive CC & CV packet generation. A MEP that has identified a signal fail related defect should include the RDI in all OAM CC/CV packets that it generates for the duration of the defect condition existence. A MEP that receives the packets with the RDI information should determine that its peer MEP has encountered a defect condition associated with a signal fail. MIPs should be transparent to the RDI indicator and should forward packets that include the indicator, i.e. the MIP should not perform any actions nor examine the indicator. When the signal condition clears, the MEP should clear the RDI indicator from subsequent transmission of OAM CC/CV packets. Peer MEP, that have set the RDI condition, should clear the condition upon reception of a packet from the source MEP with the RDI indicator cleared. 4.2.1. Configuration considerations In order to support RDI indication, the RDI transmission rate and PHB of the MEP should be configured as part of the CC & CV configuration. Busi et al. Expires April 27, 2009 [Page 15] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 4.2.2. Applications for Remote Defect Indication RDI is applicable for the following applications: o Single-ended fault management - A receiving MEP detects the RDI defect condition, which when correlated with other defect conditions in the receiving MEP may become a fault case. o Contribution to far-end performance monitoring - The indication of the far-end defect condition is used as input to the performance monitoring process. 4.3. Alarm Suppression Alarm Indication Signal function (AIS) is used to suppress alarms following detection of defect conditions at the server (sub) layer. o Packets with AIS information can be issued at a MEP, including a Server MEP, upon detecting defect conditions. A server MEP is responsible for notifying the MPLS-TP layer network MEP upon fault detection in the server layer network to which the server MEP is associated. Only Server MEPs can issue MPLS-TP packets with AIS information. Upon detection of a signal fail condition the Server MEP can immediately start transmitting packets with AIS information periodically. A Server MEP continues to transmit periodic packets with AIS information until the signal fail condition is cleared. Upon receiving a packet with AIS information a MEP detects an AIS defect condition and suppresses loss of continuity alarms associated with all its peer MEPs. A MEP resumes loss of continuity alarm generation upon detecting loss of continuity defect conditions in the absence of AIS condition. Specific configuration information required by a MEP to support AIS transmission is the following: o PHB - identifies the per-hop behaviour of packet with AIS information. A MIP is transparent to packets with AIS information and therefore does not require any information to support AIS functionality. Busi et al. Expires April 27, 2009 [Page 16] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 4.4. Lock Indication To be incorporated in a future revision of this document 4.5. Packet Loss Measurement To be incorporated in a future revision of this document 4.6. Client Signal Fail To be incorporated in a future revision of this document 5. OAM Functions for on-demand monitoring 5.1. Continuity Check and Connectivity Verification In order to preserve network resources, e.g. bandwidth, processing time at switches, it may be preferable to not use continual pro- active CC & CV. In order to perform fault management functions network management may invoke periodic on-demand bursts of CC & CV packets. Use of on-demand CC & CV is dependent on the existence of a bi-directional connection ME. An additional use of on-demand CC & CV would be to detect and locate a problem of connectivity when a problem is suspected or known based on other tools. In this case the functionality will be triggered by the network management in response to a status signal or alarm indication. On-demand CC & CV is based upon generation of OAM CC & CV packets that should uniquely identify the ME that is being checked. The on- demand functionality may be used to check either an entire ME (end- to-end) or between a MEP to a specific MIP. On-demand CC & CV may generate a one-time burst of OAM CC/CV packets, or be used to invoke periodic, non-continuous, bursts of OAM CC/CV packets. The number of packets generated in each burst is configurable at the MEPs, and should take into account normal packet- loss conditions. When invoking a periodic check of the ME, the source MEP should issue a burst of OAM CC/CV packets that uniquely identifies the ME being verified. The number of packets and their transmission rate should be pre-configured and known to both the source MEP and the target MEP or MIP. The source MEP should use the TTL field to indicate the number of hops necessary, when targeting a MIP and use the default value when performing an end-to-end. The target MEP/MIP shall return Busi et al. Expires April 27, 2009 [Page 17] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 a reply OAM CC/CV packet for each packet received. If the expected number of OAM CC/CV reply packets is not received at source MEP, a LOC state is detected. When a connectivity problem is detected (e.g. via a pro-active CC&CV OAM tool), on demand CC&CV tool can be used to check the path. The series should check CC&CV from MEP to peer MEP on the path, and if a fault is discovered, by lack of response, then additional checks may be performed to each of the intermediate MIP to locate the fault. 5.1.1. Configuration considerations For on-demand CC & CV the MEP should support configuration of number of packets to be transmitted/received in each burst of transmissions and the transmission rate should be either pre-configured or negotiated between the different nodes. In addition, when the CC & CV packet is checking connectivity toward a target MIP, the number of hops to reach the target MIP should be configured. The PHB of the CC & CV packets should be configured as well. 5.2. Packet Loss Measurement To be incorporated in a future revision of this document 5.3. Diagnostic Test To be incorporated in a future revision of this document 5.4. Trace routing To be incorporated in a future revision of this document 5.5. Packet Delay Measurement To be incorporated in a future revision of this document 6. OAM Protocols Overview To be incorporated in a future revision of this document 7. Security Considerations To be incorporated in a future revision of this document Busi et al. Expires April 27, 2009 [Page 18] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 8. IANA Considerations To be incorporated in a future revision of this document 9. Acknowledgments The authors would like to thank all members of the teams (the Joint Working Team, the MPLS Interoperability Design Team in IETF and the T-MPLS Ad Hoc Group in ITU-T) involved in the definition and specification of MPLS Transport Profile. 10. References 10.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 [2] Rosen, E., Viswanathan, A., Callon, R., "Multiprotocol Label Switching Architecture", RFC 3031, January 2001 [3] Rosen, E., et al., "MPLS Label Stack Encoding", RFC 3032, January 2001 [4] Agarwal, P., Akyol, B., "Time To Live (TTL) Processing in Multi-Protocol Label Switching (MPLS) Networks", RFC 3443, January 2003 [5] Bryant, S., Pate, P., "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005 [6] Nadeau, T., Pignataro, S., "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, December 2007 [7] Bocci, M., Bryant, S., "An Architecture for Multi-Segment Pseudo Wire Emulation Edge-to-Edge", draft-ietf-pwe3-ms-pw- arch-05 (work in progress), September 2008 [8] Bocci, M., et al., " A Framework for MPLS in Transport Networks", draft-blb-mpls-tp-framework-00 (work in progress), July 2008 [9] Vigoureux, M., Bocci, M., Swallow, G., Ward, D., Aggarwal, R., " MPLS Generic Associated Channel ", draft-bocci-mpls-tp-gach- gal-00, October 2008 Busi et al. Expires April 27, 2009 [Page 19] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 10.2. Informative References [10] Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM in MPLS Transport Networks", draft-vigoureux-mpls-tp-oam- requirements-00, July 2008 [11] Sprecher, N., Nadeau, T., van Helvoort, H., Weingarten, Y., " MPLS-TP OAM Analysis", draft-sprecher-mpls-tp-oam-analysis-02 (work in progress), September 2008 [12] ITU-T Recommendation G.707/Y.1322 (01/07), " Network node interface for the synchronous digital hierarchy (SDH)", 2007 Authors' Addresses Italo Busi (Editor) Alcatel-Lucent Email: italo.busi@alcatel-lucent.it Ben Niven-Jenkins (Editor) BT Email: benjamin.niven-jenkins@bt.com Contributing Authors' Addresses Annamaria Fulignoli Ericsson Email: annamaria.fulignoli@ericsson.com Enrique Hernandez-Valencia Alcatel-Lucent Email: enrique@alcatel-lucent.com Lieven Levrau Alcatel-Lucent Email: llevrau@alcatel-lucent.com Busi et al. Expires April 27, 2009 [Page 20] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 Dinesh Mohan (Editor) Nortel Email: mohand@nortel.com Vincenzo Sestito Alcatel-Lucent Email: vincenzo.sestito@alcatel-lucent.it Nurit Sprecher Nokia Siemens Networks Email: nurit.sprecher@nsn.com Huub van Helvoort Huawei Technologies Email: hhelvoort@huawei.com Martin Vigoureux Alcatel-Lucent Email: martin.vigoureux@alcatel-lucent.fr Yaacov Weingarten Nokia Siemens Networks Email: yaacov.weingarten@nsn.com Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Busi et al. Expires April 27, 2009 [Page 21] Internet-Draft MPLS-TP OAM Framework and Overview October 2008 Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Busi et al. Expires April 27, 2009 [Page 22]