MPLS Working Group I. Busi (Ed) Internet Draft Alcatel-Lucent Intended status: Informational B. Niven-Jenkins (Ed) BT D. Allan (Ed) Ericsson Expires: June 2010 December 10, 2009 MPLS-TP OAM Framework draft-ietf-mpls-tp-oam-framework-04.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress". 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Expires June 10, 2010 [Page 1] Internet-Draft MPLS-TP OAM Framework December 2009 Abstract Multi-Protocol Label Switching (MPLS) Transport Profile (MPLS-TP) is based on a profile of the MPLS and pseudowire (PW) procedures as 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 describes a framework to support a comprehensive set of OAM procedures that fulfills the MPLS-TP OAM requirements [12]. This document is a product of a joint Internet Engineering Task Force (IETF) / International Telecommunications Union Telecommunications Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architectures to support the capabilities and functionalities of a packet transport network. Busi et al. Expires June 10, 2010 [Page 2] Internet-Draft MPLS-TP OAM Framework December 2009 Table of Contents 1. Introduction..................................................5 1.1. Contributing Authors.....................................5 1.2. Editors Issues...........................................6 2. Conventions used in this document.............................9 2.1. Terminology..............................................9 2.2. Definitions.............................................10 3. Functional Components........................................12 3.1. Maintenance Entity and Maintenance Entity Group.........13 3.2. MEG End Points (MEPs)...................................16 3.3. MEG Intermediate Points (MIPs)..........................19 3.4. Server MEPs.............................................20 3.5. Path Segment Tunnels and Tandem Connection Monitoring...21 4. Reference Model..............................................21 4.1. MPLS-TP Section Monitoring..............................23 4.2. MPLS-TP LSP End-to-End Monitoring.......................24 4.3. MPLS-TP LSP Path Segment Tunnel Monitoring..............25 4.4. MPLS-TP PW Monitoring...................................27 4.5. MPLS-TP MS-PW Path Segment Tunnel Monitoring............27 5. OAM Functions for proactive monitoring.......................28 5.1. Continuity Check and Connectivity Verification..........29 5.1.1. Defects identified by CC-V.........................30 5.1.2. Consequent action..................................31 5.1.3. Configuration considerations.......................32 5.1.4. Applications for proactive CC-V....................33 5.2. Remote Defect Indication................................34 5.2.1. Configuration considerations.......................34 5.2.2. Applications for Remote Defect Indication..........35 5.3. Alarm Reporting.........................................35 5.4. Lock Reporting..........................................36 5.5. Packet Loss Monitoring..................................36 5.5.1. Configuration considerations.......................37 5.5.2. Applications for Packet Loss Monitoring............37 5.6. Client Signal Failure Indication........................38 5.6.1. Configuration considerations.......................38 5.6.2. Applications for Client Signal Failure Indication..38 5.7. Delay Measurement.......................................39 5.7.1. Configuration considerations.......................39 5.7.2. Applications for Delay Measurement.................40 6. OAM Functions for on-demand monitoring.......................40 6.1. Connectivity Verification...............................40 6.1.1. Configuration considerations.......................41 6.2. Packet Loss Monitoring..................................42 6.2.1. Configuration considerations.......................42 6.2.2. Applications for On-demand Packet Loss Monitoring..42 6.3. Diagnostic..............................................42 Busi et al. Expires June 10, 2010 [Page 3] Internet-Draft MPLS-TP OAM Framework December 2009 6.4. Route Tracing...........................................43 6.5. Delay Measurement.......................................44 6.5.1. Configuration considerations.......................44 6.5.2. Applications for Delay Measurement.................45 6.6. Lock Instruct...........................................45 7. Security Considerations......................................45 8. IANA Considerations..........................................45 9. Acknowledgments..............................................46 10. References..................................................47 10.1. Normative References...................................47 10.2. Informative References.................................47 Busi et al. Expires June 10, 2010 [Page 4] Internet-Draft MPLS-TP OAM Framework December 2009 Editors' Note: This Informational Internet-Draft is aimed at achieving IETF Consensus before publication as an RFC and will be subject to an IETF Last Call. [RFC Editor, please remove this note before publication as an RFC and insert the correct Streams Boilerplate to indicate that the published RFC has IETF Consensus.] 1. Introduction As noted in [8], MPLS-TP defines a profile of the MPLS-TE and (MS-)PW architectures defined in RFC 3031 [2], RFC 3985 [5] and [7] which is complemented with additional OAM mechanisms and procedures for alarm, fault, performance and protection-switching management for packet transport applications. In line with [13], existing MPLS OAM mechanisms will be used wherever possible and extensions or new OAM mechanisms will be defined only where existing mechanisms are not sufficient to meet the requirements. The MPLS-TP OAM framework defined in this document provides a comprehensive set of OAM procedures that satisfy the MPLS-TP OAM requirements [12]. In this regard, it defines similar OAM functionality as for existing SONET/SDH and OTN OAM mechanisms (e.g. [16]). The MPLS-TP OAM framework is applicable to both LSPs and (MS-)PWs and supports co-routed and bidirectional p2p transport paths as well as unidirectional p2p and p2mp transport paths. This document is a product of a joint Internet Engineering Task Force (IETF) / International Telecommunications Union Telecommunications Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architectures to support the capabilities and functionalities of a packet transport network. 1.1. Contributing Authors Dave Allan, 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, Rolf Winter Busi et al. Expires June 10, 2010 [Page 5] Internet-Draft MPLS-TP OAM Framework December 2009 1.2. Editors Issues Editor's Note: This section is to be removed prior to submission to the RFC editor. 1) ME architecture needs further discussion/clarification Agreement (call 24 November): o Co-routed bidirectional p2p transport entity: one bidirectional ME o Associated bidirectional p2p transport entity: two unidirectional MEs o Unidirectional p2p transport entity: one unidirectional ME o Unidirectional p2mp (with N leaves) transport entity: N unidirectional ME Clarify that in a p2mp transport entity all the traffic (including OAM packets) is sent (multicast) from the root to all the leaves. As a consequence: o To send an OAM packet to all leaves, it is required to send a single OAM packet that will be delivered by the forwarding plane to all the leaves and processed by all the leaves. o To send an OAM packet to a single leaf, it is required to send a single OAM packet that will be delivered by the forwarding plane to all the leaves and processed only by the target leaf and ignored by the other leaves. o In order to send an OAM packet to M leaves (i.e., a subset of all the leaves), the current working assumption is to send M different (multicast) OAM packets targeted to each individual leaf in the group of M leaves. Better mechanisms are under investigation and might be added in future versions of this draft. 2) Use of terms LTCME and PTCME, should these be genericised for PSTs. Agreement (call 24 November): the editors of the framework document will make sure that the framework document is aligned with the Busi et al. Expires June 10, 2010 [Page 6] Internet-Draft MPLS-TP OAM Framework December 2009 decision to use the term PST. This document will be aligned with this decision. 3) CV refers to using an ME ID for misbranching detection. This does not align with p2mp LSPs where a CV would then be required to carry all the MEs in the MEG. Agreement (call 24 November): we are going to use the term MEG ID in the document. ME ID has been used in older versions of the document and its use is legacy. For pro-active CC-V (both p2p and p2mp), the globally unique MEP ID information needs to be carried: section on pro-active CC-V needs to be updated accordingly. 4) Discussions of PW monitoring and PW tandem connection monitoring seem to be rendered out of scope by the layering decision at Hiroshima. Discussion points (call 24 November) - No agreement reached on this issue PW OAM architecture: based on the architecture defined in this document using MEP and MIPs PW TCM concept: just a specific application of the architecture of the TP-LSP (1:1 mapped with the monitored PW) carrying a PW segment in the MS-PW architecture. Generic clarifications (to be added) [terminology based on RFC 5654]: o before a TCM is setup, we can have a concatenated LSP segment. After the TCM (that is a TP-LSP) is setup, we have a single LSP segment between the TCM end-points; o before a TCM is setup, we can have a concatenated PW segment. After the TCM (that is a TP-LSP) is setup, we have a single PW segment between the TCM end-points. Problems with PW TCM are the implications of removing S-PEs from the PW path. Need further discussion. It is not obvious to Dave that removing an LSR from a path can be done hitlessly either ... by slipping a PST under it ... Action (Italo): check which requirements cannot be met if PW TCM between non-adjacent PEs cannot be supported and whether this is a showstopper issue or not. Busi et al. Expires June 10, 2010 [Page 7] Internet-Draft MPLS-TP OAM Framework December 2009 Action (Italo): describe the PW TCM as an LSP and circulate the description to the mailing list for review. If needed, another call will be setup to finalize the discussion. Action (Matthew, Italo): Develop a couple of diagrams showing how the mechanism works for LSPs and PWs. 5) Concerns have been raised against the idea of having MIPs capable to generate spontaneous messages. AIS/Lock Indication packets are generated by the adaptation functions. This point needs clarifying. Agreement (9 December): AIS/Lock Indication are generate by a MIP node (to be define as a node hosting a MIP) w/o saying that they are generated by a MIP. The general framework will describe the mechanism for intermediate nodes to insert packets and each specific framework document (e.g., OAM framework) will describe the usage of this capability on a case- by-case basis. When you provision bw between two end-points you must allow enough bw for any additional traffic, including traffic from MEPs and MIPs. OAM framework will describe that a MIP node may insert OAM packets into a LSP and this will be described on a function-by-function basis. It will also describe the functions that require a MIP to generate OAM packets (e.g., on-demand CV). 6) Presence or absence of MIPs is a bizarre point. At least one MIP in every node is addressed by TTL, and gaps in the enablement of MIPs would produce spurious test results. A convention of "MIPs exist at any node on a transport path that has a return path to a source MEP" would make sense vs. discussing manual enable/disable/configuration of MIPs. Note - the annotated text ("If the set of MIPs is actually sparse (i.e. not every hop is a MIP), then it has to be intermediate nodes to do some operations") needs further clarification. Agreement (9 December): All the intermediate nodes host MIP(s). Local policy allows them to be enabled per function and per LSP. The local policy is controlled by the management system, which may delegate it to the control plane. Busi et al. Expires June 10, 2010 [Page 8] Internet-Draft MPLS-TP OAM Framework December 2009 7) Discussions in Hiroshima and subsequent calls have suggested use of alternative return paths "if available", not all of which will be GAL/GACH encapsulated? This point needs clarifying. Agreement (9 December): When the return path is not an MPLS-TP path, the reply message does not need to be GAL/ACH encapsulated. The request message needs to carry sufficient information to allow the target MIP/MEP to reply when a non MPLS-TP return path is used. 8) Data plane loopback Action (17 November): check on the mailing list (both ITU-T and IETF to get inputs from both types of operators). 9) Review the draft to check that all the known implications related to the support of p2mp transport paths have been described. This check will be done in the next version after the current open points/comments have been resolved. 10)Given layering discussion in Hiroshima, it is not very clear whether MPLS TP is a sub layer network within the MPLS layer network or a layer network by its own. This issue should be resolved in the context of the MPLS TP Framework draft but has impacts on this draft as well. 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 RFC-2119 [1]. 2.1. Terminology AC Attachment Circuit DBN Domain Border Node FDI Forward Defect Indication LER Label Edge Router LME LSP Maintenance Entity Busi et al. Expires June 10, 2010 [Page 9] Internet-Draft MPLS-TP OAM Framework December 2009 LSP Label Switched Path LSR Label Switch Router LPSTME LSP packet segment tunnel ME ME Maintenance Entity MEG Maintenance Entity Group MEP Maintenance Entity Group End Point MIP Maintenance Entity Group Intermediate Point PHB Per-hop Behavior PME PW Maintenance Entity PPSTME PW path segment tunnel ME PST Path Segment Tunnel PSN Packet Switched Network PW Pseudowire SLA Service Level Agreement SME Section Maintenance Entity 2.2. Definitions Note - the definitions in this section are intended to be in line with ITU-T recommendation Y.1731 in order to have a common, unambiguous terminology. They do not however intend to imply a certain implementation but rather serve as a framework to describe the necessary OAM functions for MPLS-TP. Domain Border Node (DBN): An LSP intermediate MPLS-TP node (LSR) that is at the boundary of an MPLS-TP OAM domain. Such a node may be present on the edge of two domains or may be connected by a link to an MPLS-TP node in another OAM domain. Maintenance Entity (ME): Some portion of a transport path that requires management bounded by two points, and the relationship between those points to which maintenance and monitoring operations apply (details in section 3.1). Busi et al. Expires June 10, 2010 [Page 10] Internet-Draft MPLS-TP OAM Framework December 2009 Maintenance Entity Group (MEG): The set of one or more maintenance entities that maintain and monitor a transport path in an OAM domain. MEP: A MEG end point (MEP) is capable of initiating (MEP Source) and terminating (MEP Sink) OAM messages for fault management and performance monitoring. MEPs reside at the boundaries of an ME (details in section 3.2). MEP Source: A MEP acts as MEP source for an OAM message when it originates and inserts the message into the transport path for its associated MEG. MEP Sink: A MEP acts as a MEP sink for an OAM message when it terminates and processes the messages received from its associated MEG. MIP: A MEG intermediate point (MIP) terminates and processes OAM messages and may generate OAM messages in reaction to received OAM messages. It never generates unsolicited OAM messages itself. A MIP resides within an MEG between MEPs (details in section 3.2). OAM domain: A domain, as defined in [11], whose entities are grouped for the purpose of keeping the OAM confined within that domain. Note - within the rest of this document the term "domain" is used to indicate an "OAM domain" OAM flow: Is the set of all OAM messages originating with a specific MEP that instrument one direction of a MEG. OAM information element: An atomic piece of information exchanged between MEPs in MEG used by an OAM application. OAM Message: One or more OAM information elements that when exchanged between MEPs or between MEPs and MIPs performs some OAM functionality (e.g. connectivity verification) OAM Packet: A packet that carries one or more OAM messages (i.e. OAM information elements). Path: See Transport Path Signal Fail: A condition declared by a MEP when the data forwarding capability associated with a transport path has failed, e.g. loss of continuity. Busi et al. Expires June 10, 2010 [Page 11] Internet-Draft MPLS-TP OAM Framework December 2009 Tandem Connection: A tandem connection is an arbitrary part of a transport path that can be monitored (via OAM) independent of the end-to-end monitoring (OAM). The tandem connection may also include the forwarding engine(s) of the node(s) at the boundaries of the tandem connection. This document uses the terms defined in RFC 5654 [11]. This document uses the term 'Per-hop Behavior' as defined in [14]. 3. Functional Components MPLS-TP defines a profile of the MPLS and PW architectures ([2], [5] and [7]) that is designed to transport service traffic where the characteristics of information transfer between the transport path endpoints can be demonstrated to comply with certain performance and quality guarantees. In order to verify and maintain these performance and quality guarantees, there is a need to not only apply OAM functionality on a transport path granularity (e.g. LSP or MS-PW), but also on arbitrary parts of transport paths, defined as Tandem Connections, between any two arbitrary points along a path. In order to describe the required OAM functionality, this document introduces a set of high-level functional components. [Note - discussion in Munich -tues concluded that TCM not possible with PWs - can monitor a single PW segment - but attempting to monitor more than one segment converts the PW into an LSP and therefore the intervening SPEs are unable to see the PW as a PW due to the differences in how OAM flows are disambiguated.] [editors: if true this IMO is a huge problem as the one place I would really want TCM is a multi-domain MS-PW, else I have to control plane peer at two layers, pending resolution of discussion item 4 in section 1.2] When a control plane is not present, the management plane configures these functional components. Otherwise they can be configured either by the management plane or by the control plane. These functional components should be instantiated when the path is created by either the management plane or by the control plane (if present). Some components may be instantiated after the path is initially created (e.g. PST). [Dave: are we discussing the same issue for LSP PSTs as for PWs, an S-PE cannot easily be removed, certainly not hitlessly, how is an LSP different?] Busi et al. Expires June 10, 2010 [Page 12] Internet-Draft MPLS-TP OAM Framework December 2009 3.1. Maintenance Entity and Maintenance Entity Group MPLS-TP OAM operates in the context of Maintenance Entities (MEs) that are a relationship between two points of a point to point transport path or a root and a leaf of a point to multipoint transport path to which maintenance and monitoring operations apply. These two points are called Maintenance Entity Group (MEG) End Points (MEPs). In between these two points zero or more intermediate points, called Maintenance Entity Group Intermediate Points (MIPs), MAY exist and can be shared by more than one ME in a MEG. The MEPs that form an MEG are configured and managed to limit the scope of an OAM flow within the MEG that the MEPs belong to (i.e. within the domain of the transport path or segment, in the specific sub-layer of the MPLS layer network, that is being monitored and managed). A misbranching fault may cause OAM packets to be delivered to a MEP that is not in the MEG of origin. The abstract reference model for an ME with MEPs and MIPs is described in Figure 1 below: +-+ +-+ +-+ +-+ |A|----|B|----|C|----|D| +-+ +-+ +-+ +-+ Figure 1 ME Abstract Reference Model The instantiation of this abstract model to different MPLS-TP entities is described in section 4. In this model, nodes A, B, C and D can be LER/LSR for an LSP or the {S|T}-PEs for a MS-PW. MEPs reside in nodes A and D while MIPs reside in nodes B and C. The links connecting adjacent nodes can be physical links, or sub-layer LSPs/PSTs. This functional model defines the relationships between all OAM entities from a maintenance perspective, to allow each Maintenance Entity to monitor and manage the layer network under its responsibility and to localize problems efficiently. [Editor's note - MEG are sub-layers. Need to check the document for consistency with this agreement] An MPLS-TP maintenance entity group can cover either the whole end- to-end path or a path segment tunnel supporting some portion of the transport path. A Maintenance Entity Group may be defined to monitor the transport path for fault and/or performance management. Busi et al. Expires June 10, 2010 [Page 13] Internet-Draft MPLS-TP OAM Framework December 2009 In case of associated bi-directional paths, two independent Maintenance Entities are defined to independently monitor each direction. This has implications for transactions that terminate at or query a MIP as a return path from MIP to source MEP does not exist in a unidirectional ME. The following properties apply to all MPLS-TP MEGs: o They can be nested but not overlapped, e.g. an MEG may cover a segment or a concatenated segment of another MEG, and may also include the forwarding engine(s) of the node(s) at the edge(s) of the segment or concatenated segment, but all its MEPs and MIPs are no longer part of the encompassing MEG. It is possible that MEPs of nested MEGs reside on a single node. o Each OAM flow is associated with a single Maintenance Entity Group. o OAM packets that instrument a particular direction of an LSP are subject to the same forwarding treatment (i.e. fate share) as the data traffic and in some cases may be required to have common queuing discipline E2E with the class of traffic monitored. OAM packets can be distinguished from the data traffic using the GAL and ACH constructs [9] for LSP and Section or the ACH construct [6]and [9] for (MS-)PW. [Editor's note: A key point in the definition of an ME is the end- points are defined by location of the logical function MEP Later in the framework we will discuss the precision with which we can identify the location of a MEP/MIP i.e, ingress i/f, egress i/f or node. We need to distinguish between the point of interception of an OAM msg and the point where the action takes place. Action: look at the text in the framework document regarding the location of the functional components (MEPs and MIPs).] [Editors' note: Somewhere we need to distinguish between the OAM control function and the OAM measurement function. i.e. we set up a loop back (a control function, in which case the OAM message may be intercepted and actioned anywhere convenient), and the measurement function (i.e. looping the packet to determine that it reached a particular part of the network) which needs to be actioned at a precisely know and stipulated point in the network/equipment. Busi et al. Expires June 10, 2010 [Page 14] Internet-Draft MPLS-TP OAM Framework December 2009 Action (Dave) - add some text on the subject.] Note that not all functionality / processing of an OAM pkt needs to take place at the point of measurement. [editors: this comment is not clear. For discussion during revision call] [Editors' note - Address this comment while addressing the control and measurement issue above. We considered that an OAM function can be decomposed into the following components - Instruction or command - Execution - Addressing (node, interface etc) is ttl/LSP enough - do we need sub-addressing to cause execution on a specific component in the node - i.e. egress interface - Response via OAM - Reporting to mgt interface] [Editor's note: the MPLS-TP framework will describe how it is possible to inject OAM packets on intermediate nodes. We need to describe how this capability is used within the OAM framework and to reference to the MPLS-TP framework for the description of this capability] Another OAM construct is referred to as Maintenance Entity Group, which is a collection of one or more MEs that belongs to the same transport path and that are maintained and monitored as a group. A use case for an MEG with more than one ME is point-to-multipoint OAM. The reference model for the p2mp MEG is represented in Figure 2. Busi et al. Expires June 10, 2010 [Page 15] Internet-Draft MPLS-TP OAM Framework December 2009 +-+ /--|D| / +-+ +-+ /--|C| +-+ +-+/ +-+\ +-+ |A|----|B| \--|E| +-+ +-+\ +-+ +-+ \--|F| +-+ Figure 2 Reference Model for p2mp MEG In case of p2mp transport paths, the OAM operations are independent for each ME (A-D, A-E and A-F): o Fault conditions - some faults may impact more than one ME depending from where the failure is located o Packet loss - packet dropping may impact more than one ME depending from where the packets are lost o Packet delay - depending on different paths Each leaf (i.e. D, E and F) terminates OAM flows to monitor the ME from itself and the root while the root (i.e. A) generates OAM messages common to all the MEs of the p2mp MEG. Nodes B and C MAY implement a MIP in the corresponding MEG. 3.2. MEG End Points (MEPs) MEG End Points (MEPs) are the source and sink points of an MEG. In the context of an MPLS-TP LSP, only LERs can implement MEPs while in the context of a path segment tunnel (PST) both LERs and LSRs can implement MEPs that contribute to the overall monitoring infrastructure for the transport path. Regarding MPLS-TP PW, only T- PEs can implement MEPs while for PSTs supporting a PW both T-PEs and S-PEs can implement MEPs. In the context of MPLS-TP Section, any MPLS-TP NE can implement a MEP. [Munich: See note about PW Tandem monitoring earlier, and whether a PW can be a tandem connection - for further discussion (discussion point 4 in section 1.2)] MEPs are responsible for activating and controlling all of the OAM functionality for the MEG. A MEP is capable of originating and Busi et al. Expires June 10, 2010 [Page 16] Internet-Draft MPLS-TP OAM Framework December 2009 terminating OAM messages for fault management and performance monitoring. These OAM messages are encapsulated into an OAM packet using the G-ACh as defined in RFC 5586 [9]: in this case the G-ACh message is an OAM message and the channel type indicates an OAM message. A MEP terminates all the OAM packets it receives from the MEG it belongs to. The MEG the OAM packet belongs to is inferred from the MPLS or PW label.[Editors: given the discussion about alternative return paths, is a GAL/GaCH always present ...?. For discussion on the IETF review calls] Once an MEG is configured, the operator can configure which OAM functions to use on the MEG but the MEPs are always enabled. A node at the edge of an MEG always supports a MEP. MEPs terminate all OAM packets received from the associated transport path or path segment tunnel [Editors: the PST definition in the framework should be augmented to clarity that the clients of a PST should always be LSPs or PWs]. As the MEP corresponds to the termination of the forwarding path for an MEG at the given sub-level, OAM packets never "leaks" outside of a MEG in a fault free implementation. A MEP of an MPLS-TP transport path (Section, LSP or PW) coincides with transport path termination and monitors it for failures or performance degradation (e.g. based on packet counts) in an end-to- end scope. Note that both MEP source and MEP sink coincide with transport paths' source and sink terminations. The MEPs of a path segment tunnel are not necessarily coincident with the termination of the MPLS-TP transport path (LSP or PW) and monitor some portion of the transport path for failures or performance degradation (e.g. based on packet counts) only within the boundary of the MEG for the path segment tunnel. An MPLS-TP MEP sink passes a fault indication to its client (sub-)layer network as a consequent action of fault detection. It may occur that the MEPs of a path segment tunnel are set on both sides of the forwarding engine such that the MEG is entirely internal to the node. Note that a MEP can only exist at the beginning and end of a sub-layer i.e. an LSP or PW. If we need to monitor some portion of that LSP or PW [editor: mention of PW in this context needs to be revised after agreement on discussion point 4 in section 1.2], a new sub-layer in the form of a path segment tunnel MUST be created which permits MEPs and an associated MEG to be created. Busi et al. Expires June 10, 2010 [Page 17] Internet-Draft MPLS-TP OAM Framework December 2009 [Editor: We need to describe the migration process for adding a path segment tunnel.] [Editor's note: Update the draft to capture the agreements below after the discussion points 5, 6 and 7 in section 1.2 are resolved (to maintain consistency): We have the case of a MIP sending msg to a MEP. To do this it uses the LSP label - i.e. the top label of the stack at that point. [editors: move and clarify in section 3.3 - for further discuss. If the set of MIPs is actually sparse (i.e. not every hop is a MIP), then it has to be intermediate nodes to do some operations.] Agreement (10 November): An intermediate node can send an OAM packet. Clarify that we need to provide enough bandwidth on the transport paths to support OAM traffic (throughout the framework document). From IETF point of view no distinction between MIPs and adaptation functions. Lou question about how triggered response OAM packets are sent by MIPs/MEPs. Agreement (call 9 December): o bidirectional co-routed: use the reverse path (thus checking both the forward and backward directions of the transport path). Co-routed bidirectional transport paths can have a minimum bandwidth return path. o unidirectional p2p and p2mp: no ability to support triggered response OAM message Non MPLS-TP LSP/PW return path MAY be requested by the OAM message triggering the reply and the target MIP/MEP MAY attempt to reply using the requested return path. In this case, only the forward direction of the MPLS-TP transport path is checked and the connectivity to the source MEP via the requested return path is not guaranteed. Agreement (call 17 November) to use as a working assumption the same MEP/MIP model in MS-PW OAM architecture. In order to validate this working assumption we need to understand how to describe the PW Status information: this information is propagated on a hop-by-hop Busi et al. Expires June 10, 2010 [Page 18] Internet-Draft MPLS-TP OAM Framework December 2009 basis between adjacent PEs using LDP (dynamic PW segments) or ACH Status PW (static PW segments).] 3.3. MEG Intermediate Points (MIPs) A MEG Intermediate Point (MIP) is a point between the MEPs of an MEG. A MIP is capable of reacting to some OAM packets and forwarding all the other OAM packets while ensuring fate sharing with data plane packets. However, a MIP does not initiate [unsolicited OAM - editors: this text was removed in the commented .rtf document from Munich but not tracked as a revision, validate this change after MIP/MEP discussion (discussion point 5 in section 1.2)] packets, but may be addressed by OAM packets initiated by one of the MEPs of the MEG. A MIP can generate OAM packets only in response to OAM packets that are sent on the MEG it belongs to. An intermediate node within a point-to-point MEG can either: o not support MPLS-TP OAM (i.e. no MIPs per node) o support per-node MIP (i.e. a single MIP per node) o support per-interface MIP (i.e. two MIPs per node on both sides of the forwarding engine) [Editor's note - Need to describe MIPs for p2mp MEGs] [Editor's note - Add a Figure to describe how the two options can be support] A node at the edge of an MEG can also support a MEP and a per-interface MIP at the two sides of the forwarding engine. When sending an OAM packet to a MIP, the source MEP should set the TTL field to indicate the number of hops necessary to reach the node where the MIP resides. It is always assumed that the "pipe"/"short pipe" model of TTL handling is used by the MPLS transport profile. The source MEP should also include Target MIP information in the OAM packets sent to a MIP to allow proper identification of the MIP within the node. The MEG the OAM packet is associated with is inferred from the MPLS label. Once an MEG is configured, the operator can enable/disable the MIPs on the nodes within the MEG. [Editors': review this paragraph after discussion point 6 in section 1.2 is resolved] Busi et al. Expires June 10, 2010 [Page 19] Internet-Draft MPLS-TP OAM Framework December 2009 3.4. Server MEPs A server MEP is a MEP of an MEG that is either: o defined in a layer network that is "below", which is to say encapsulates and transports the MPLS-TP layer network being referenced, or o defined in a sub-layer of the MPLS-TP layer network that is "below" which is to say encapsulates and transports the sub-layer being referenced. A server MEP can coincide with a MIP or a MEP in the client (MPLS-TP) layer network. [Editors' note: review the text above pending discussion of whether MPLS-TP is a sub-layer network within the MPLS layer network or a layer network by its own (discussion point 10 in section 1.2)] A server MEP also interacts with the client/server adaptation function between the client (MPLS-TP) (sub-)layer network and the server (sub-)layer network. The adaptation function maintains state on the mapping of MPLS-TP transport paths that are setup over that server layer's transport path. For example, a server MEP can be either: o A termination point of a physical link (e.g. 802.3), an SDH VC or OTN ODU, for the MPLS-TP Section layer network, defined in section 4.1; o An MPLS-TP Section MEP for MPLS-TP LSPs, defined in section 4.2; o An MPLS-TP LSP MEP for MPLS-TP PWs, defined in section 4.4; o An MPLS-TP PST MEP for higher-level PSTs, defined in section 4.3; o An MPLS-TP PW Tandem Connection MEP for higher-level PTCMEs, defined in section 4.5. [Editor: update this bullet after the discussion on PW TCM (discussion point 4 in section 1.2)] The server MEP can run appropriate OAM functions for fault detection within the server (sub-)layer network, and provides a fault indication to its client MPLS-TP layer network. Server MEP OAM functions are outside the scope of this document. Busi et al. Expires June 10, 2010 [Page 20] Internet-Draft MPLS-TP OAM Framework December 2009 3.5. Path Segment Tunnels and Tandem Connection Monitoring Path segment tunnels (PSTs) are instantiated to provide monitoring of a portion of a set of co-routed transport paths. Path segment tunnels can also be employed to meet the requirement to provide tandem connection monitoring (TCM). TCM for a given portion of a transport path is implemented by first creating a path segment tunnel that that has a 1:1 association with portion of the transport path that is to be uniquely monitored. This means there is direct correlation between all FM and PM information gathered for the PST AND the monitored portion of the E2E path. The PST is monitored using normal LSP monitoring. There are a number of implications to this approach: 1) The PST would use the uniform model of EXP code point copying between sub-layers for diffserv such that the E2E markings and PHB treatment for the transport path was preserved by the PST. 2) The PST would use the pipe model for TTL handling such that MIP addressing for the E2E entity would be not be impacted by the presence of the PST. 3) PM statistics need to be adjusted for the encapsulation overhead of the additional PST sub-layer. 4. Reference Model The reference model for the MPLS-TP framework builds upon the concept of an MEG, and its associated MEPs and MIPs, to support the functional requirements specified in [12]. The following MPLS-TP MEGs are specified in this document: o A Section Maintenance Entity Group (SME), allowing monitoring and management of MPLS-TP Sections (between MPLS LSRs). o A LSP Maintenance Entity Group (LME), allowing monitoring and management of an end-to-end LSP (between LERs). o A PW Maintenance Entity Group (PME), allowing monitoring and management of an end-to-end SS/MS-PWs (between T-PEs). o A PST Maintenance Entity Group (PSTME), allowing monitoring and management of a path segment tunnel (between any LERs/LSRs along an LSP). Busi et al. Expires June 10, 2010 [Page 21] Internet-Draft MPLS-TP OAM Framework December 2009 o A MS-PW Tandem Connection Maintenance Entity (PTCME), allowing monitoring and management of a PW Tandem Connection (between any T-PEs/S-PEs along the (MS-)PW) [Editors': update this bullet after resolution of PW TCM discussion (discussion point 4 in section 1.2] The MEGs specified in this MPLS-TP framework are compliant with the architecture framework for MPLS-TP MS-PWs [7] and LSPs [2]. Hierarchical LSPs are also supported in the form of path segment tunnels. In this case, each LSP Tunnel in the hierarchy is a different sub-layer network that can be monitored, independently from higher and lower level LSP tunnels in the hierarchy, on an end-to-end basis (from LER to LER) by a PSTME. It is possible to monitor a portion of a hierarchical LSP by instantiating a hierarchical PSTME between any LERs/LSRs along the hierarchical LSP. Native |<------------------- MS-PW1Z ------------------->| 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|---|........PW13.......|...PW3X..|........PWXZ.......|---|CE2 | | | | |=========| |=========| |=========| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ . . . . | | | | |<---- Domain 1 --->| |<---- Domain Z --->| ^------------------- PW1Z PME -------------------^ ^---- PW13 PPSTME---^ ^---- PWXZ PPSTME---^ ^---------^ ^---------^ PSN13 LME PSNXZ LME ^---^ ^---^ ^---------^ ^---^ ^---^ Sec12 Sec23 Sec3X SecXY SecYZ SME SME SME SME 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 3 Reference Model for the MPLS-TP OAM Framework Busi et al. Expires June 10, 2010 [Page 22] Internet-Draft MPLS-TP OAM Framework December 2009 Figure 3 depicts a high-level reference model for the MPLS-TP OAM framework. The figure depicts portions of two MPLS-TP enabled network domains, Domain 1 and Domain Z. In Domain 1, LSR1 is adjacent to LSR2 via the MPLS Section Sec12 and LSR2 is adjacent to LSR3 via the MPLS Section Sec23. Similarly, in Domain Z, LSRX is adjacent to LSRY via the MPLS Section SecXY and LSRY is adjacent to LSRZ via the MPLS Section SecYZ. In addition, LSR3 is adjacent to LSRX via the MPLS Section 3X. Figure 3 also shows a bi-directional MS-PW (PW1Z) between AC1 on TPE1 and AC2 on TPEZ. The MS-PW consists of three bi-directional PW Segments: 1) PW13 segment between T-PE1 and S-PE3 via the bi- directional PSN13 LSP, 2) PW3X segment between S-PE3 and S-PEX, via the bi-directional PSN3X LSP, and 3) PWXZ segment between S-PEX and T-PEZ via the bi-directional PSNXZ LSP. The MPLS-TP OAM procedures that apply to an MEG of a given transport path are expected to operate independently from procedures on other MEGs of the same transport path and certainly MEGs of other transport paths. Yet, this does not preclude that multiple MEGs may be affected simultaneously by the same network condition, for example, a fiber cut event. Note that there are no constrains imposed by this OAM framework on the number, or type (p2p, p2mp, LSP or PW), of MEGs that may be instantiated on a particular node. In particular, when looking at Figure 3, it should be possible to configure one or more MEPs on the same node if that node is the endpoint of one or more MEGs. Figure 3 does not describe a PW3X PPSTME because typically PSTs are used to monitor an OAM domain (like PW13 and PWXZ PPSTMEs) rather than the segment between two OAM domains. However the OAM framework does not pose any constraints on the way PSTs are instantiated as long as they are not overlapping. The subsections below define the MEGs specified in this MPLS-TP OAM architecture framework document. Unless otherwise stated, all references to domains, LSRs, MPLS Sections, LSPs, pseudowires and MEGs in this section are made in relation to those shown in Figure 3. 4.1. MPLS-TP Section Monitoring An MPLS-TP Section ME (SME) is an MPLS-TP maintenance entity intended to an MPLS Section as defined in [11]. An SME may be configured on any MPLS section. SME OAM packets must fate share with the user data packets sent over the monitored MPLS Section. Busi et al. Expires June 10, 2010 [Page 23] Internet-Draft MPLS-TP OAM Framework December 2009 An SME is intended to be deployed for applications where it is preferable to monitor the link between topologically adjacent (next hop in this layer network) MPLS (and MPLS-TP enabled) LSRs rather than monitoring the individual LSP or PW segments traversing the MPLS Section and the server layer technology does not provide adequate OAM capabilities. |<------------------- MS-PW1Z ------------------->| | | | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | V V LSP V V LSP V V LSP V V +----+ +-+ +----+ +----+ +-+ +----+ +----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+ | |AC1| |=========| |=========| |=========| |AC2| | | CE1|---|........PW13.......|...PW3X..|.......PWXZ........|---|CE2 | | | | |=========| |=========| |=========| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ ^--^ ^--^ ^---------^ ^---^ ^---^ Sec12 Sec23 Sec3X SecXY SecYZ SME SME SME SME SME Figure 4 Reference Example of MPLS-TP Section MEs (SME) Figure 4 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. 4.2. MPLS-TP LSP End-to-End Monitoring An MPLS-TP LSP ME (LME) is an MPLS-TP maintenance entity intended to monitor an end-to-end LSP between two LERs. An LME may be configured on any MPLS LSP. LME OAM packets must fate share with user data packets sent over the monitored MPLS-TP LSP. Busi et al. Expires June 10, 2010 [Page 24] Internet-Draft MPLS-TP OAM Framework December 2009 An LME is intended to be deployed in scenarios where it is desirable to monitor an entire LSP between its LERs, rather than, say, monitoring individual PWs. |<------------------- MS-PW1Z ------------------->| | | | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | V V LSP V V LSP V V LSP V V +----+ +-+ +----+ +----+ +-+ +----+ +----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+ | |AC1| |=========| |=========| |=========| |AC2| | | CE1|---|........PW13.......|...PW3X..|........PWXZ.......|---|CE2 | | | | |=========| |=========| |=========| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ ^---------^ ^---------^ PSN13 LME PSNXZ LME Figure 5 Examples of MPLS-TP LSP MEs (LME) Figure 5 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. Note that the presence of a PSN3X LME in such a configuration is optional, hence, not precluded by this framework. For instance, the SPs may prefer to monitor the MPLS-TP Section between the two LSRs rather than the individual LSPs. 4.3. MPLS-TP LSP Path Segment Tunnel Monitoring An MPLS-TP LSP Path Segment Tunnel ME (LPSTME) is an MPLS-TP maintenance entity intended to monitor an arbitrary part of an LSP between a given pair of LSRs independently from the end-to-end monitoring (LME). An LPSTMEE can monitor an LSP segment or concatenated segment and it may also include the forwarding engine(s) of the node(s) at the edge(s) of the segment or concatenated segment. Multiple LPSTMEs MAY be configured on any LSP. The LSRs that terminate the LPSTME may or may not be immediately adjacent at the MPLS-TP layer. LPSTME OAM packets must fate share with the user data packets sent over the monitored LSP segment. A LPSTME can be defined between the following entities: o LER and any LSR of a given LSP. o Any two LSRs of a given LSP. Busi et al. Expires June 10, 2010 [Page 25] Internet-Draft MPLS-TP OAM Framework December 2009 An LPSTME is intended to be deployed in scenarios where it is preferable to monitor the behaviour of a part of an LSP or set of LSPs rather than the entire LSP itself, for example when there is a need to monitor a part of an LSP that extends beyond the administrative boundaries of an MPLS-TP enabled administrative domain. |<--------------------- PW1Z -------------------->| | | | |<--------------PSN1Z LSP-------------->| | | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | V V S-LSP V V S-LSP V V S-LSP V V +----+ +-+ +----+ +----+ +-+ +----+ +----+ | PE1| | | |DBN3| |DBNX| | | | PEZ| +----+ | |AC1| |=======================================| |AC2| | | CE1|---|......................PW1Z.......................|---|CE2 | | | | |=======================================| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ . . . . | | | | |<---- Domain 1 --->| |<---- Domain Z --->| ^---------^ ^---------^ PSN13 LPSTME PSNXZ LPSTME ^---------------------------------------^ PSN1Z LME DBN: Domain Border Node Figure 6 MPLS-TP LSP Path Segment Tunnel ME (LPSTME) Figure 6 depicts a variation of the reference model in Figure 3 where there is an end-to-end PSN LSP (PSN1Z LSP) between PE1 and PEZ. PSN1Z LSP consists of, at least, three LSP Concatenated Segments: PSN13, PSN3X and PSNXZ. In this scenario there are two separate LTCMEs configured to monitor the PSN1Z LSP: 1) a LPSTME monitoring the PSN13 LSP Concatenated Segment on Domain 1 (PSN13 LPSTME), and 2) a LPSTME monitoring the PSNXZ LSP Concatenated Segment on Domain Z (PSNXZ LPSTME). It is worth noticing that LPSTMEs can coexist with the LME monitoring the end-to-end LSP and that LPSTME MEPs and LME MEPs can be coincident in the same node (e.g. PE1 node supports both the PSN1Z LME MEP and the PSN13 LPSTME MEP). Busi et al. Expires June 10, 2010 [Page 26] Internet-Draft MPLS-TP OAM Framework December 2009 4.4. MPLS-TP PW Monitoring An MPLS-TP PW ME (PME) is an MPLS-TP maintenance entity intended to monitor 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 must 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 an entire PW between a pair of MPLS-TP enabled T-PEs rather than monitoring the LSP aggregating multiple PWs between PEs. |<------------------- MS-PW1Z ------------------->| | | | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | V V LSP V V LSP V V LSP V V +----+ +-+ +----+ +----+ +-+ +----+ +----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+ | |AC1| |=========| |=========| |=========| |AC2| | | CE1|---|........PW13.......|...PW3X..|........PWXZ.......|---|CE2 | | | | |=========| |=========| |=========| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ ^---------------------PW1Z PME--------------------^ Figure 7 MPLS-TP PW ME (PME) Figure 7 depicts a MS-PW (MS-PW1Z) consisting of three segments: PW13, PW3X and PWXZ and its associated end-to-end PME (PW1Z PME). 4.5. MPLS-TP MS-PW Path Segment Tunnel Monitoring [Editors' note: revise this section after the discussion on PW TCM is closed (discussion item 4 in section 1.2)] An MPLS-TP MS-PW Path Segment Tunnel Monitoring ME (PPSTME) is an MPLS-TP maintenance entity intended to monitor an arbitrary part of an MS-PW between a given pair of PEs independently from the end-to- end monitoring (PME). A PPSTME can monitor a PW segment or concatenated segment and it may also include the forwarding engine(s) of the node(s) at the edge(s) of the segment or concatenated segment. Multiple PPSTMEs MAY be configured on any MS-PW. The PEs may or may not be immediately adjacent at the MS-PW layer. PPSTME OAM packets fate share with the user data packets sent over the monitored PW Segment. Busi et al. Expires June 10, 2010 [Page 27] Internet-Draft MPLS-TP OAM Framework December 2009 A PPSTME 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 PPSTME is intended to be deployed in scenarios where it is preferable to monitor the behaviour of a part of a MS-PW rather than the entire end-to-end PW itself, for example to monitor an MS-PW Segment within a given network domain of an inter-domain MS-PW. |<------------------- MS-PW1Z ------------------->| | | | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | V V LSP V V LSP V V LSP V V +----+ +-+ +----+ +----+ +-+ +----+ +----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+ | |AC1| |=========| |=========| |=========| |AC2| | | CE1|---|........PW13.......|...PW3X..|........PWXZ.......|---|CE2 | | | | |=========| |=========| |=========| | | | +----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ +-+ +----+ +----+ +-+ +----+ ^---- PW1 PPSTME----^ ^---- PW5 PPSTME----^ ^---------------------PW1Z PME--------------------^ Figure 8 MPLS-TP MS-PW Path Segment Tunnel Monitoring (PPSTME) Figure 8 depicts the same MS-PW (MS-PW1Z) between AC1 and AC2 as in Figure 7. In this scenario there are two separate PPSTMEs configured to monitor MS-PW1Z: 1) a PPSTME monitoring the PW13 MS-PW Segment on Domain 1 (PW13 PPSTME), and 2) a PTCME monitoring the PWXZ MS-PW Segment on Domain Z with (PWXZ PPSTME). It is worth noticing that PPSTMEs can coexist with the PME monitoring the end-to-end MS-PW and that PPSTME MEPs and PME MEPs can be coincident in the same node (e.g. TPE1 node supports both the PW1Z PME MEP and the PW13 PPSTME MEP). 5. OAM Functions for proactive monitoring [Editors' note: at the beginning of each section, reference the section in the OAM Requirements document and explicitly list additional detailed requirements wrt the OAM Requirements document] Busi et al. Expires June 10, 2010 [Page 28] Internet-Draft MPLS-TP OAM Framework December 2009 In this document, proactive monitoring refers to OAM operations that are either configured to be carried out periodically and continuously or preconfigured to act on certain events such as alarm signals. 5.1. Continuity Check and Connectivity Verification Proactive Continuity Check functions are used to detect a loss of continuity defect (LOC) between two MEPs in an MEG. Proactive Connectivity Verification functions are used to detect an unexpected connectivity defect between two MEGs (e.g. mismerging or misconnection), as well as unexpected connectivity within the MEG with an unexpected MEP. Both functions are based on the (proactive) generation of OAM packets by the source MEP that are processed by the sink MEP. As a consequence these two functions are grouped together into Continuity Check and Connectivity Verification (CC-V) OAM packets. In order to perform pro-active Connectivity Verification function, each CC-V OAM packet MUST also include a globally unique Source MEP identifier. When used to perform only pro-active Continuity Check function, the CC-V OAM packet MAY not include any globally unique Source MEP identifier identifier. Different formats of MEP identifiers are defined in [10] to address different environments. When MPLS-TP is deployed in transport network environments where IP addressing is not used in the forwarding plane, the ICC-based format for MEP identification is used. When MPLS-TP is deployed in IP-based environment, the IP-based MEP identification is used. As a consequence, it is not possible to detect misconnections between two MEGs monitored only for Continuity while it is possible to detect any misconnection between two MEGs monitored for Continuity and Connectivity or between an MEG monitored for Continuity and Connectivity and one MEG monitored only for Continuity. [Editor's note - Rephrase the previous paragraph: describe the four cases.] CC-V OAM packets MUST be transmitted at a regular, operator's configurable, rate. The default CC-V transmission periods are application dependent (see section 5.1.4). Proactive CC-V OAM packets are transmitted with the "minimum loss probability PHB" within a single network operator. This PHB is configurable on network operator's basis. PHBs can be translated at Busi et al. Expires June 10, 2010 [Page 29] Internet-Draft MPLS-TP OAM Framework December 2009 the network borders by the same function that translates it for user data traffic. [Editor's note - Describe the relation between the previous paragraph and the fate sharing requirement. Need to clarify also in the requirement document that for proactive CC-V the fate sharing is related to the forwarding behavior and not to the QoS behavior] In a bidirectional point-to-point transport path, when a MEP is enabled to generate pro-active CC-V OAM packets with a configured transmission rate, it also expects to receive pro-active CC-V OAM packets from its peer MEP at the same transmission rate as a common SLA applies to all components of the transport path. In a unidirectional transport path (either point-to-point or point-to- multipoint), only the source MEP is enabled to generate CC-V OAM packets and only the sink MEP is configured to expect these packets at the configured rate. MIPs, as well as intermediate nodes not supporting MPLS-TP OAM, are transparent to the pro-active CC-V information and forward these pro- active CC-V OAM packets as regular data packets. It is desirable to not generate spurious alarms during initialization or tear down; hence the following procedures are recommended. At initialization, the MEP source function (generating pro-active CC-V packets) should be enabled prior to the corresponding MEP sink function (detecting continuity and connectivity defects). When disabling the CC-V proactive functionality, the MEP sink function should be disabled prior to the corresponding MEP source function. 5.1.1. Defects identified by CC-V Pro-active CC-V functions allow a sink MEP to detect the defect conditions described in the following sub-sections. For all of the described defect cases, the sink MEP SHOULD notify the equipment fault management process of the detected defect. 5.1.1.1. Loss Of Continuity defect When proactive CC-V is enabled, a sink MEP detects a loss of continuity (LOC) defect when it fails to receive pro-active CC-V OAM packets from the peer MEP. o Entry criteria: if no pro-active CC-V OAM packets from the peer MEP (i.e. with the correct globally unique Source MEP identifier) are received within the interval equal to 3.5 times the receiving MEP's configured CC-V reception period. Busi et al. Expires June 10, 2010 [Page 30] Internet-Draft MPLS-TP OAM Framework December 2009 o Exit criteria: a pro-active CC-V OAM packet from the peer MEP (i.e. with the correct globally unique Source MEP identifier) is received. 5.1.1.2. Mis-connectivity defect When a pro-active CC-V OAM packet is received, a sink MEP identifies a mis-connectivity defect (e.g. mismerge, misconnection or unintended looping) with its peer source MEP when the received packet carries an incorrect globally unique Source MEP identifier. o Entry criteria: the sink MEP receives a pro-active CC-V OAM packet with an incorrect globally unique Source MEP identifier. o Exit criteria: the sink MEP does not receive any pro-active CC-V OAM packet with an incorrect globally unique Source MEP identifier for an interval equal at least to 3.5 times the longest transmission period of the pro-active CC-V OAM packets received with an incorrect globally unique Source MEP identifier since this defect has been raised. This requires the OAM message to self identify the CC-V periodicity as not all MEPs can be expected to have knowledge of all MEGs. 5.1.1.3. Period Misconfiguration defect If pro-active CC-V OAM packets are received with a correct globally unique Source MEP identifier but with a transmission period different than the locally configured reception period, then a CV period mis- configuration defect is detected. o Entry criteria: a MEP receives a CC-V pro-active packet with correct globally unique Source MEP identifier but with a Period field value different than its own CC-V configured transmission period. o Exit criteria: the sink MEP does not receive any pro-active CC-V OAM packet with a correct globally unique Source MEP identifier and an incorrect transmission period for an interval equal at least to 3.5 times the longest transmission period of the pro- active CC-V OAM packets received with a correct globally unique Source MEP identifier and an incorrect transmission period since this defect has been raised. 5.1.2. Consequent action [editors: IMO this would be better folded into the specific defect types, If agreed I will edit accordingly] Busi et al. Expires June 10, 2010 [Page 31] Internet-Draft MPLS-TP OAM Framework December 2009 A sink MEP that detects one of the defect conditions defined in section 5.1.1 MUST perform the following consequent actions. Some of these consequent actions SHOULD be enabled/disabled by the operator depending upon the application used (see section 5.1.4). If a MEP detects an unexpected globally unique Source MEP Identifier, it MUST block all the traffic (including also the user data packets) that it receives from the misconnected transport path. If a MEP detects LOC defect that is not caused by a period mis-configuration, it SHOULD block all the traffic (including also the user data packets) that it receives from the transport path, if this consequent action has been enabled by the operator. It is worth noticing that the OAM requirements document [12] recommends that CC-V proactive monitoring is enabled on every MEG in order to reliably detect connectivity defects. However, CC-V proactive monitoring MAY be disabled by an operator on an MEG. In the event of a misconnection between a transport path that is pro- actively monitored for CC-V and a transport path which is not, the MEP of the former transport path will detect a LOC defect representing a connectivity problem (e.g. a misconnection with a transport path where CC-V proactive monitoring is not enabled) instead of a continuity problem, with a consequent wrong traffic delivering. For these reasons, the traffic block consequent action is applied even when a LOC condition occurs. This block consequent action MAY be disabled through configuration. This deactivation of the block action may be used for activating or deactivating the monitoring when it is not possible to synchronize the function activation of the two peer MEPs. If a MEP detects a LOC defect (section 5.1.1.1), a mis-connectivity defect (section 5.1.1.2) or a period misconfiguration defect (section 5.1.1.3), it MUST declare a signal fail condition at the transport path level. [Editor's note - Transport equipment also performs defect correlation (as defined in G.806) in order to properly report failures to the transport NMS]. The current working assumption, to be further investigated, is that defect correlations are outside the scope of this document and to be defined in ITU-T documents.] 5.1.3. Configuration considerations At all MEPs inside a MEG, the following configuration information needs to be configured when a proactive CC-V function is enabled: Busi et al. Expires June 10, 2010 [Page 32] Internet-Draft MPLS-TP OAM Framework December 2009 o MEG ID; the MEG identifier to which the MEP belongs; o MEP-ID; the MEP's own identity inside the MEG; o list of peer MEPs inside the MEG. For a point-to-point MEG the list would consist of the single peer MEP ID from which the OAM packets are expected. In case of the root MEP of a p2mp MEG, the list is composed by all the leaf MEP IDs inside the MEG. In case of the leaf MEP of a p2mp MEG, the list is composed by the root MEP ID (i.e. each leaf MUST know the root MEP ID from which it expect to receive the CC-V OAM packets). o transmission rate; the default CC-V transmission periods are application dependent (see section 5.1.4) Note that the reception period is the same as the configured transmission rate. o PHB; it identifies the per-hop behaviour of CC-V packet. Proactive CC-V packets are transmitted with the "minimum loss probability PHB" previously configured within a single network operator. This PHB is configurable on network operator's basis. PHBs can be translated at the network borders. For statically provisioned transport paths the above information are statically configured; for dynamically established transport paths the configuration information are signaled via the control plane. 5.1.4. Applications for proactive CC-V CC-V 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). Performance monitoring is only relevant when the transport path is defect free. CC-V contributes to the accuracy of PM statistics by permitting the defect free periods to be properly distinguished. o Protection Switching: default transmission period is 3.33ms (i.e. transmission rate of 300 packets/second), in order to achieve sub- 50ms the CC-V defect entry criteria should resolve in less than 10msec, and complete a protection switch within a subsequent period of 50 msec. Busi et al. Expires June 10, 2010 [Page 33] Internet-Draft MPLS-TP OAM Framework December 2009 It SHOULD be possible for the operator to configure these transmission rates for all applications, to satisfy his internal requirements. In addition, the operator should be able to define the consequent action to be performed for each of these applications. 5.2. 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-V activation. The RDI indicator is piggy-backed onto the CC-V packet. When a MEP detects a signal fail condition (e.g. in case of a continuity or connectivity defect), it should begin transmitting an RDI indicator to its peer MEP. The RDI information will be included in all pro-active CC-V packets that it generates for the duration of the signal fail condition's existence. [Editor's note - Add some forward compatibility information to cover the case where future OAM mechanisms that contributes to the signal fail detection (and RDI generation) are defined.] 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 as well as intermediate nodes not supporting MPLS-TP OAM are transparent to the RDI indicator and forward these proactive CC-V packets that include the RDI indicator as regular data packets, i.e. the MIP should not perform any actions nor examine the indicator. When the signal fail defect condition clears, the MEP should clear the RDI indicator from subsequent transmission of pro-active CC-V packets. A MEP should clear the RDI defect upon reception of a pro- active CC-V packet from the source MEP with the RDI indicator cleared. 5.2.1. Configuration considerations In order to support RDI indication, this may be a unique OAM message or an OAM information element embedded in a CV message. In this case the RDI transmission rate and PHB of the OAM packets carrying RDI should be the same as that configured for CC-V. Busi et al. Expires June 10, 2010 [Page 34] Internet-Draft MPLS-TP OAM Framework December 2009 5.2.2. Applications for Remote Defect Indication RDI is applicable for the following applications: o Single-ended fault management - A MEP that receives an RDI indication from its peer MEP, can report a far-end defect condition (i.e. the peer MEP has detected a signal fail condition in the traffic direction from the MEP that receives the RDI indication to the peer MEP that has sent the RDI information). o Contribution to far-end performance monitoring - The indication of the far-end defect condition is used as a contribution to the bidirectional performance monitoring process. 5.3. Alarm Reporting The Alarm Reporting function relies upon an Alarm Indication Signal (AIS) message used to suppress alarms following detection of defect conditions at the server (sub-)layer. o A server MEP that detects a signal fail conditions in the server (sub-)layer, will notify the MPLS-TP client (sub-)layer adaptation function, which can generate packets with AIS information in a direction opposite to its peers MEPs to allow the suppression of secondary alarms at the MEP in the client (sub-)layer. A server MEP is responsible for notifying the MPLS-TP layer network adaptation function upon fault detection in the server layer network to which the server MEP is associated. Only the client layer adaptation function at an intermediate node will issue MPLS-TP packets with AIS information. Upon receiving notification of a signal fail condition the adaptation function SHOULD immediately start transmitting periodic packets with AIS information. These periodic packets, with AIS information, continue to be transmitted until the signal fail condition is cleared. Upon receiving a packet with AIS information an MPLS-TP MEP enters an AIS defect condition and suppresses loss of continuity alarms associated with its peer MEP. A MEP resumes loss of continuity alarm generation upon detecting loss of continuity defect conditions in the absence of AIS condition. For example, let's consider a fiber cut between LSR 1 and LSR 2 in the reference network of Figure 3. Assuming that all the MEGs described in Figure 3 have pro-active CC-V enabled, a LOC defect is detected by the MEPs of Sec12 SME, PSN13 LME, PW1 PTCME and PW1Z PME, Busi et al. Expires June 10, 2010 [Page 35] Internet-Draft MPLS-TP OAM Framework December 2009 however in transport network only the alarm associate to the fiber cut needs to be reported to NMS while all these secondary alarms should be suppressed (i.e. not reported to the NMS or reported as secondary alarms). If the fiber cut is detected by the MEP in the physical layer (in LSR2), LSR2 can generate the proper alarm in the physical layer and suppress the secondary alarm associated with the LOC defect detected on Sec12 SME. As both MEPs reside within the same node, this process does not involve any external protocol exchange. Otherwise, if the physical layer has not enough OAM capabilities to detect the fiber cut, the MEP of Sec12 SME in LSR2 will report a LOC alarm. In both cases, the MEP of Sec12 SME in LSR 2 notifies the adaptation function for PSN13 LME that then generates AIS packets on the PSN13 LME in order to allow its MEP in LSR3 to suppress the LOC alarm. LSR3 can also suppress the secondary alarm on PW13 PPSTME because the MEP of PW13 PPSTME resides within the same node as the MEP of PSN13 LME. The MEP of PW13 PPSTME in LSR3 also notifies the adaptation function for PW1Z PME that then generates AIS packets on PW1Z PME in order to allow its MEP in LSRZ to suppress the LOC alarm. The generation of AIS packets for each MEG in the client (sub-)layer is configurable (i.e. the operator can enable/disable the AIS generation). AIS packets are transmitted with the "minimum loss probability PHB" within a single network operator. This PHB is configurable on network operator's basis. A MIP is transparent to packets with AIS information and therefore does not require any information to support AIS functionality. 5.4. Lock Reporting To be incorporated in a future revision of this document 5.5. Packet Loss Monitoring Packet Loss Monitoring (LM) is one of the capabilities supported by the MPLS-TP Performance Monitoring (PM) function in order to facilitate reporting of QoS information for a transport path. LM is used to exchange counter values for the number of ingress and egress packets transmitted and received by the transport path monitored by a pair of MEPs. Busi et al. Expires June 10, 2010 [Page 36] Internet-Draft MPLS-TP OAM Framework December 2009 Proactive LM is performed by periodically sending LM OAM packets from a MEP to a peer MEP and by receiving LM OAM packets from the peer MEP (if a bidirectional transport path) during the life time of the transport path. Each MEP performs measurements of its transmitted and received packets. These measurements are then transactionally correlated with the peer MEP in the ME to derive the impact of packet loss on a number of performance metrics for the ME in the MEG. The LM transactions are issued such that the OAM packets will experience the same queuing discipline as the measured traffic while transiting between the MEPs in the ME. For a MEP, near-end packet loss refers to packet loss associated with incoming data packets (from the far-end MEP) while far-end packet loss refers to packet loss associated with egress data packets (towards the far-end MEP). 5.5.1. Configuration considerations In order to support proactive LM, the transmission rate and PHB associated with the LM OAM packets originating from a MEP need be configured as part of the LM provisioning procedures. LM OAM packets should be transmitted with the PHB that yields the lowest packet loss performance among the PHB Scheduling Classes or Ordered Aggregates (see RFC 3260 [15]) in the monitored transport path for the relevant network domain(s). 5.5.2. Applications for Packet Loss Monitoring LM is relevant for the following applications: o Single or double-end performance monitoring: determination of the packet loss performance of a transport path for Service Level Agreement (SLA) verification purposes. o Single or double-end performance monitoring: determination of the packet loss performance of a PHB Scheduling Class or Ordered Aggregate within a transport path. o Contribution to service unable time. Both near-end and far-end packet loss measurements contribute to performance metrics such as near-end severely errored seconds (Near-End SES) and far-end severely errored seconds (Far-End SES) respectively, which together contribute to unavailable time, in a manner similar to Recommendation G.826 [19] and Recommendation G.7710 [20]. Busi et al. Expires June 10, 2010 [Page 37] Internet-Draft MPLS-TP OAM Framework December 2009 5.6. Client Signal Failure Indication The Client Signal Failure Indication (CSF) function is used to help process client defects and propagate a client signal defect condition from the process associated with the local attachment circuit where the defect was detected (typically the source adaptation function for the local client interface) to the process associated with the far- end attachment circuit (typically the source adaptation function for the far-end client interface) for the same transmission path in case the client of the transmission path does not support a native defect/alarm indication mechanism, e.g. FDI/AIS. [Editor's note - The need to support this function on the LSP layer (and not only at the PW layer) needs to be further investigated. Pending discussion on MPLS-TP clients in the main framework document.] A source MEP starts transmitting a CSF indication to its peer MEP when it receives a local client signal defect notification via its local CSF function. Mechanisms to detect local client signal fail defects are technology specific. A sink MEP that has received a CSF indication report this condition to its associated client process via its local CSF function. Consequent actions toward the client attachment circuit are technology specific. Either there needs to be a 1:1 correspondence between the client and the MEG, or when multiple clients are multiplexed over a transport path, the CSF message requires additional information to permit the client instance to be identified. 5.6.1. Configuration considerations In order to support CSF indication, the CSF transmission rate and PHB of the CSF OAM message/information element should be configured as part of the CSF configuration. 5.6.2. Applications for Client Signal Failure Indication CSF is applicable for the following applications: o Single-ended fault management - A MEP that receives a CSF indication from its peer MEP, can report a far-end client defect condition (i.e. the peer MEP has been informed of local client signal fail condition in the traffic direction from the client to the peer MEP that transmitted the CSF). Busi et al. Expires June 10, 2010 [Page 38] Internet-Draft MPLS-TP OAM Framework December 2009 o Contribution to far-end performance monitoring - The indication of the far-end defect condition may be used to account on network operator contribution to the bidirectional performance monitoring process. CSF supports the application described in Appendix VIII of ITU-T G.806 [18]. 5.7. Delay Measurement Delay Measurement (DM) is one of the capabilities supported by the MPLS-TP PM function in order to facilitate reporting of QoS information for a transport path. Specifically, pro-active DM is used to measure the long-term packet delay and packet delay variation in the transport path monitored by a pair of MEPs. Proactive DM is performed by sending periodic DM OAM packets from a MEP to a peer MEP and by receiving DM OAM packets from the peer MEP (if a bidirectional transport path) during a configurable time interval. Pro-active DM can be operated in two ways: o One-way: a MEP sends DM OAM packet to its peer MEP containing all the required information to facilitate one-way packet delay and/or one-way packet delay variation measurements at the peer MEP. Note that this requires synchronized precision time at either MEP by means outside the scope of this framework. o Two-way: a MEP sends DM OAM packet with a DM request to its peer MEP, which replies with a DM OAM packet as a DM response. The request/response DM OAM packets containing all the required information to facilitate two-way packet delay and/or two-way packet delay variation measurements from the viewpoint of the source MEP. 5.7.1. Configuration considerations In order to support pro-active DM, the transmission rate and PHB associated with the DM OAM packets originating from a MEP need be configured as part of the DM provisioning procedures. DM OAM packets should be transmitted with the PHB that yields the lowest packet loss performance among the PHB Scheduling Classes or Ordered Aggregates (see RFC 3260 [15]) in the monitored transport path for the relevant network domain(s). Busi et al. Expires June 10, 2010 [Page 39] Internet-Draft MPLS-TP OAM Framework December 2009 5.7.2. Applications for Delay Measurement DM is relevant for the following applications: o Single or double-end performance monitoring: determination of the delay performance of a transport path for SLA verification purposes. o Single or double-end performance monitoring: determination of the delay performance of a PHB Scheduling Class or Ordered Aggregate within a transport path 6. OAM Functions for on-demand monitoring [Editors' note: at the beginning of each section, reference the section in the OAM Requirements document and explicitly list additional detailed requirements wrt the OAM Requirements document] In contrast to proactive monitoring, on-demand monitoring is initiated manually and for a limited amount of time, usually for operations such as e.g. diagnostics to investigate into a defect condition. 6.1. Connectivity Verification In order to preserve network resources, e.g. bandwidth, processing time at switches, it may be preferable to not use proactive CC-V. In order to perform fault management functions, network management may invoke periodic on-demand bursts of on-demand CV packets. Use of on-demand CV is dependent on the existence of a bi-directional MEG, because it requires the presence of a return path in the data plane.[Editors': needs to be revised on the basis of the return path discussion (discussion item 7 in section 1.2] [Editor's note - Clarify in the sentence above and within the paragraph that on-demand CV requires a return path to send back the reply to on-demand CV packets] An additional use of on-demand 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 CV is based upon generation of on-demand CV packets that should uniquely identify the MEG that is being checked. The on- Busi et al. Expires June 10, 2010 [Page 40] Internet-Draft MPLS-TP OAM Framework December 2009 demand functionality may be used to check either an entire MEG (end- to-end) or between a MEP to a specific MIP. This functionality may not be available for associated bidirectional paths as the MIP may not have a return path to the source MEP for the on-demand CV transaction. On-demand CV may generate a one-time burst of on-demand CV packets, or be used to invoke periodic, non-continuous, bursts of on-demand 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 MEG, the source MEP should issue a burst of on-demand CV packets that uniquely identifies the MEG 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 check [IB => This is quite generic for addressing packets to MIPs and MEPs so it is better to move this text in section 2]. The target MEP/MIP shall return a reply on-demand CV packet for each packet received. If the expected number of on-demand CV reply packets is not received at source MEP, the LOC defect state is entered. [Editor's note - We need to add some text for the usage of on-demand CV with different packet sizes, e.g. to discover MTU problems.] 6.1.1. Configuration considerations For on-demand CV the MEP should support the configuration of the number of packets to be transmitted/received in each burst of transmissions and their packet size. The transmission rate should be configured between the different nodes. In addition, when the CV packet is used to check connectivity toward a target MIP, the number of hops to reach the target MIP should be configured. The PHB of the on-demand CV packets should be configured as well. [Editor's note - We need to be better define the reason for such configuration] Busi et al. Expires June 10, 2010 [Page 41] Internet-Draft MPLS-TP OAM Framework December 2009 6.2. Packet Loss Monitoring On-demand Packet Loss (LM) is one of the capabilities supported by the MPLS-TP Performance Monitoring function in order to facilitate diagnostic of QoS performance for a transport path. As proactive LM, on-demand LM is used to exchange counter values for the number of ingress and egress packets transmitted and received by the transport path monitored by a pair of MEPs. On-demand LM is performed by periodically sending LM OAM packets from a MEP to a peer MEP and by receiving LM OAM packets from the peer MEP (if a bidirectional transport path) during a pre-defined monitoring period. Each MEP performs measurements of its transmitted and received packets. These measurements are then correlated evaluate the packet loss performance metrics of the transport path. 6.2.1. Configuration considerations In order to support on-demand LM, the beginning and duration of the LM procedures, the transmission rate and PHB associated with the LM OAM packets originating from a MEP must be configured as part of the on-demand LM provisioning procedures. LM OAM packets should be transmitted with the PHB that yields the lowest packet loss performance among the PHB Scheduling Classes or Ordered Aggregates (see RFC 3260 [15]) in the monitored transport path for the relevant network domain(s). 6.2.2. Applications for On-demand Packet Loss Monitoring On-demand LM is relevant for the following applications: o Single-end performance monitoring: diagnostic of the packet loss performance of a transport path for SLA trouble shooting purposes. o Single-end performance monitoring: diagnostic of the packet loss performance of a PHB Scheduling Class or Ordering Aggregate within a transport path for QoS trouble shooting purposes. 6.3. Diagnostic To be incorporated in a future revision of this document [Editors' note: describe an OAM tool for throughput estimation (out- of-service): works in one-way and two-way modes] [Editors' note: Need further investigation about the need to support a data-plane loopback. If needed, which layer does have to support Busi et al. Expires June 10, 2010 [Page 42] Internet-Draft MPLS-TP OAM Framework December 2009 this function (i.e. the MPLS-TP layer or its server layer?) It is also needed to understand whether it is needed to specify where this data-plane loopback takes place within the equipment] [Munich: Need to describe the two types of loopback - LBM/LBR and traffic loopback enhanced with variable sized packets in the on demand cases. One objective of diags is fault location, we need to make clear how we apply the tools to fault location. At the top of each section we need to describe the detailed requirements and then in the rest of the section describe how it is met.] 6.4. Route Tracing [Editors' note: The framework needs to say what you need to trace and not how you do it (remove the description of the solution).] [Editors' note: Need to investigate if we need both tracing options: describe why and a sketch of the two options and their properties. Possible reasons for both options: o TTL incremental tells whether the CP is correct or not o the second one (path discovery) is ... Action: check on the mailing list the need to support both modes of operations.] After e.g. provisioning an MPLS-TP LSP or for trouble shooting purposes, it is often necessary to trace a route covered by an ME from a source MEP to the sink MEP including all the MIPs in-between. The route tracing function is providing this functionality. Based on the fate sharing requirement of OAM flows, i.e. OAM packets receive the same forwarding treatment as data packet, route tracing is a basic means to perform CV and, to a much lesser degree, CC. For this function to work properly, a return path must be present. Route tracing might be implemented in different ways and this document does not preclude any of them. Route trace could be implemented e.g. by an MPLS traceroute-like function [RFC4379]. However, route tracing should always return the full list of MIPs and the peer MEP in it answer(s). In case a defect exist, the route trace function needs to be able to detect it and stop automatically Busi et al. Expires June 10, 2010 [Page 43] Internet-Draft MPLS-TP OAM Framework December 2009 returning the incomplete list of OAM entities that it was able to trace. The configuration of the route trace function must at least support the setting of the trace depth (number of hops)_and the number of trace attempts before it gives up. Default setting need to be configurable by the operator, too. 6.5. Delay Measurement Delay Measurement (DM) is one of the capabilities supported by the MPLS-TP PM function in order to facilitate reporting of QoS information for a transport path. Specifically, on-demand DM is used to measure packet delay and packet delay variation in the transport path monitored by a pair of MEPs during a pre-defined monitoring period. On-Demand DM is performed by sending periodic DM OAM packets from a MEP to a peer MEP and by receiving DM OAM packets from the peer MEP (if a bidirectional transport path) during a configurable time interval. On-demand DM can be operated in two ways: o One-way: a MEP sends DM OAM packet to its peer MEP containing all the required information to facilitate one-way packet delay and/or one-way packet delay variation measurements at the peer MEP. o Two-way: a MEP sends DM OAM packet with a DM request to its peer MEP, which replies with an DM OAM packet as a DM response. The request/response DM OAM packets containing all the required information to facilitate two-way packet delay and/or two-way packet delay variation measurements from the viewpoint of the source MEP. 6.5.1. Configuration considerations In order to support on-demand DM, the beginning and duration of the DM procedures, the transmission rate and PHB associated with the DM OAM packets originating from a MEP need be configured as part of the LM provisioning procedures. DM OAM packets should be transmitted with the PHB that yields the lowest packet delay performance among the PHB Scheduling Classes or Ordering Aggregates (see RFC 3260 [15]) in the monitored transport path for the relevant network domain(s). Busi et al. Expires June 10, 2010 [Page 44] Internet-Draft MPLS-TP OAM Framework December 2009 In order to verify different performances between long and short packets (e.g., due to the processing time), it SHOULD be possible for the operator to configure of the on-demand OAM DM packet. 6.5.2. Applications for Delay Measurement DM is relevant for the following applications: o Single or double-end performance monitoring: determination of the packet delay and/or delay variation performance of a transport path for SLA verification purposes. o Single or double-end performance monitoring: determination of the packet delay and/or delay variation a PHB Scheduling Class or Ordering Aggregate within a transport path o Contribution to service unable time. Packet delay measurements may contribute to performance metrics such as near-end severely errored seconds (Near-End SES) and far-end severely errored seconds (Far-End SES), which together contribute to unavailable time. 6.6. Lock Instruct To be incorporated in a future revision of this document 7. Security Considerations A number of security considerations are important in the context of OAM applications. OAM traffic can reveal sensitive information such as passwords, performance data and details about e.g. the network topology. The nature of OAM data therefore suggests to have some form of authentication, authorization and encryption in place. This will prevent unauthorized access to vital equipment and it will prevent third parties from learning about sensitive information about the transport network. Mechanisms that the framework does not specify might be subject to additional security considerations. 8. IANA Considerations No new IANA considerations. Busi et al. Expires June 10, 2010 [Page 45] Internet-Draft MPLS-TP OAM Framework December 2009 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. This document was prepared using 2-Word-v2.0.template.dot. Busi et al. Expires June 10, 2010 [Page 46] Internet-Draft MPLS-TP OAM Framework December 2009 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-ietf-mpls-tp-framework-06 (work in progress), October 2009 [9] Vigoureux, M., Bocci, M., Swallow, G., Ward, D., Aggarwal, R., "MPLS Generic Associated Channel", RFC 5586, June 2009 [10] Swallow, G., Bocci, M., "MPLS-TP Identifiers", draft-ietf-mpls- tp-identifiers-00 (work in progress), November 2009 10.2. Informative References [11] Niven-Jenkins, B., Brungard, D., Betts, M., sprecher, N., Ueno, S., "MPLS-TP Requirements", RFC 5654, September 2009 [12] Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM in MPLS Transport Networks", draft-ietf-mpls-tp-oam-requirements- 03 (work in progress), August 2009 Busi et al. Expires June 10, 2010 [Page 47] Internet-Draft MPLS-TP OAM Framework December 2009 [13] Sprecher, N., Nadeau, T., van Helvoort, H., Weingarten, Y., "MPLS-TP OAM Analysis", draft-ietf-mpls-tp-oam-analysis-00 (work in progress), November 2009 [14] Nichols, K., Blake, S., Baker, F., Black, D., "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, December 1998 [15] Grossman, D., "New terminology and clarifications for Diffserv", RFC 3260, April 2002. [16] ITU-T Recommendation G.707/Y.1322 (01/07), "Network node interface for the synchronous digital hierarchy (SDH)", January 2007 [17] ITU-T Recommendation G.805 (03/00), "Generic functional architecture of transport networks", March 2000 [18] ITU-T Recommendation G.806 (01/09), "Characteristics of transport equipment - Description methodology and generic functionality ", January 2009 [19] ITU-T Recommendation G.826 (12/02), "End-to-end error performance parameters and objectives for international, constant bit-rate digital paths and connections", December 2002 [20] ITU-T Recommendation G.7710 (07/07), "Common equipment management function requirements", July 2007 [21] ITU-T Recommendation Y.2611 (06/12), " High-level architecture of future packet-based networks", 2006 Authors' Addresses Dave Allan (Editor) Ericsson Email: david.i.allan@ericsson.com Italo Busi (Editor) Alcatel-Lucent Email: Italo.Busi@alcatel-lucent.com Busi et al. Expires June 10, 2010 [Page 48] Internet-Draft MPLS-TP OAM Framework December 2009 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.Hernandez@alcatel-lucent.com Lieven Levrau Alcatel-Lucent Email: Lieven.Levrau@alcatel-lucent.com Dinesh Mohan Nortel Email: mohand@nortel.com Vincenzo Sestito Alcatel-Lucent Email: Vincenzo.Sestito@alcatel-lucent.com Nurit Sprecher Nokia Siemens Networks Email: nurit.sprecher@nsn.com Busi et al. Expires June 10, 2010 [Page 49] Internet-Draft MPLS-TP OAM Framework December 2009 Huub van Helvoort Huawei Technologies Email: hhelvoort@huawei.com Martin Vigoureux Alcatel-Lucent Email: Martin.Vigoureux@alcatel-lucent.com Yaacov Weingarten Nokia Siemens Networks Email: yaacov.weingarten@nsn.com Rolf Winter NEC Email: Rolf.Winter@nw.neclab.eu Busi et al. Expires June 10, 2010 [Page 50]