Framework for Point-to-Multipoint MPLS-TP OAM
Author(s): Takafumi Hamano, Yoshinori Koike, Masatoshi Namiki
The MPLS transport profile (MPLS-TP) is being standardized to enable carrier-grade packet transport....
MPLS Working Group Y.Koike, Ed. Internet Draft T.Hamano M.Namiki NTT Intended status: Informational Expires: August 24, 2013 February 25, 2013 Framework for Point-to-Multipoint MPLS-TP OAM draft-hmk-mpls-tp-p2mp-oam-framework-02.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on August 24, 2013. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of Koike, et al. Expires August 24, 2013 [Page 1] Internet-Draft MPLS-TP p2mp OAM framework February 2013 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Abstract The MPLS transport profile (MPLS-TP) is being standardized to enable carrier-grade packet transport. This document discusses and specifies the P2MP framework primarily related to OAM and related management in MPLS-TP networks. This document mainly refers to RFC5654 and RFC6371. The main focus is on the details that are not covered or not clarified in relevant RFCs such as RFC5654, RFC5860, RFC5921, RFC5951, RFC6371, and draft-mpls- tp-p2mp-framework. Note: This I-D was made and updated including the discussions in ITU- T SG15, which were described in Liaison Statements such as (https://datatracker.ietf.org/liaison/1235/) 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. Table of Contents 1. Introduction ................................................ 3 2. Conventions used in this document............................ 4 2.1. Terminology ............................................ 4 2.2. Definitions ............................................ 4 3. P2MP OAM .................................................... 5 3.1. OAM functions for proactive monitoring .................. 8 3.1.1. Continuity Check and Connectivity Verification..... 11 3.1.2. Remote Defect Indication .......................... 11 3.1.3. Alarm Reporting ................................... 12 Koike, et al. Expires May 8, 2013 [Page 2] Internet-Draft MPLS-TP p2mp OAM framework February 2013 3.1.4. Lock Reporting .................................... 12 3.1.5. Packet Loss Measurement ........................... 12 3.1.6. Packet Delay Measurement .......................... 12 3.1.7. Client Failure Indication ......................... 12 3.2. OAM functions for on-demand monitoring ................. 12 3.2.1. Connectivity verification ......................... 12 3.2.2. Packet loss measurement ........................... 13 3.2.3. Diagnostic tests .................................. 13 3.2.4. Route Tracing ..................................... 13 3.2.5. Packet delay measurement .......................... 13 3.3. OAM functions for administration control ............... 13 3.3.1. Lock Instruct ..................................... 13 4. Security Considerations ..................................... 13 5. IANA Considerations ........................................ 13 6. References ................................................. 14 6.1. Normative References ................................... 14 6.2. Informative References ................................. 14 7. Acknowledgments ............................................ 14 1. Introduction The demand for P2MP traffic is expected to quickly increase due to the increase in new services such as IP-TV,compressed & uncompressed video distribution, and smart TV. In light of the global trend in improving energy efficiency as well as general network cost reduction, a point-to-multipoint (P2MP) transport function in MPLS-TP could be one of the solutions for providing these services from the perspective of efficient use of network resources. RFC5654 defines the following requirements that are specific to P2MP. - Traffic-engineered point-to-multipoint (P2MP) transport paths.(item 6). - Unidirectional point-to-multipoint(P2MP) transport paths (item 8) - Being capable of using P2MP server (sub)layer capabilities when supporting P2MP MPLS-TP transport paths(item 40) - The MPLS-TP control plane MUST support establishing all the connectivity patterns defined for the MPLS-TP data plane (i.e. unidirectional P2MP) including the configuration of protection functions and any associated maintenance functions.(item 50) - Unidirectional 1+1 protection for P2MP connectivity (item 65 C) - Unidirectional 1:n protection for P2MP connectivity(item 67 B) - MPLS-TP recovery in a ring MUST protect unidirectional P2MP transport paths.(item 95) Koike, et al. Expires May 8, 2013 [Page 3] Internet-Draft MPLS-TP p2mp OAM framework February 2013 RFC5860  defines MPLS-TP OAM requirements including those for unidirectional P2MP transport paths. With a unidirectional P2MP transport path, two cases are assumed as per Section 3.3 of RFC6371. One is when no return path exists or not used and the other is when an "out-of-band" return path exists and used. In I-D, only a summary of various items specific to MPLS-TP P2MP framework. For example, according to the editor's note, this section will contain a summary of P2MP OAM, as described in RFC6371 , which defines the overall OAM architecture for MPLS-TP. Therefore, this draft intends to specify details of a P2MP framework that complements P2MP requirements and the framework of existing RFCs, particularly in terms of OAM, management, and recovery. Note: MPLS-TP functions that are applicable specifically to P2MP transport paths are outside the scope of RFC5921. 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 . 2.1. Terminology EMS Element management system LSP Label Switched Path NE Network Element NMS Network Management System 2.2. Definitions None Koike, et al. Expires May 8, 2013 [Page 4] Internet-Draft MPLS-TP p2mp OAM framework February 2013 3. P2MP OAM and management 3.1. General aspects of architecture 3.1.1. Return path The support of P2MP OAM on the data path should be independent of the availability of a return path or the mechanism that supports the return path. Basically, only unidirectional P2MP is supported in MPLS-TP. This means that an "in-band" return path is out of the scope of MPLS-TP requirements. In this section, two cases, with out-band return path and without return path, are considered basic and the requirements that should be met when return paths exist should be independently specified in other document, if needed. P2MP considerations are described in Section 3.7 of RFC6371. The RFC has already described some requirements with out-band return path(s). On the other hand, even if there is no return path, most OAM requirements in RFC5860 can be met by supporting the management interface through which EMS/NMS can retrieve the received OAM packets. The "return path" may be considered to be directed to the entity that originally requested the measurements because this may not be the head end of the P2MP connection. Therefore, the following return path should be distinctly differentiated. RP-N: A return path to the EMS/NMS through the management interface (RP-N) (this case is referred to as that in which no return path exists) RP-HE: A return path to a head end (root) of a P2MP path using any kind of out-of-band path (this case is referred to as that in which an out-of-band return path exists) The interpretation of return path usually corresponds to RP-HE. These two kinds of return paths may be applied at the same time, depending on the situations. 3.1.2. M-leaves management scenario in P2MP path Generally, a function to monitor only the subset leaves of a P2MP transport path is required to appropriately monitor the status of P2MP transport paths. The supplemental requirements are as follows. 1) M-leaves management, which enables NMS to perform OAM functions at a set of leaves on a P2MP transport path, must be supported. Koike, et al. Expires May 8, 2013 [Page 5] Internet-Draft MPLS-TP p2mp OAM framework February 2013 2) M-leaves must be selectable by the operator or administrator using NMS. 3) M-leaves management should be independently enabled/disabled in each OAM function. 4) In M-leave monitoring, one scenario should be selected to avoid future interoperability problems between related entities (NE, EMS, and NMS). There are four scenarios considered in MPLS-TP networks that consist of NEs, EMS, and NMS. In scenario 1, OAM protocol extension is necessary. OAM packets sent from the source MEP must include a subset of leaf-MEPs. A sink MEP determines if it should be notified of the management process within an NE based on the leaf-IDs included in the OAM packet. However, this is not supported in RFC6371. In scenario 2, OAM packets that are supported in RFC6371 and are targeted at all leaves can be utilized. As a result, no extension is necessary in the P2MP OAM protocol. On the other hand, a subset of M- leave/sink MEPs must be configured at an EMS from an NMS. In addition, a pre-configuration of a subset of M-leave/sink MEPs is needed at related NEs from the EMS. Only the notification-enabled M- leaves/nodes notify the EMS of its monitoring results. In scenario 3, OAM packets that are supported in RFC6371 and are targeted at all leaves can also be utilized. There is no P2MP OAM protocol extension. On the other hand, NMS configuration on M- leaves/sink MEPs is needed. In addition, a subset of M-leave/sink MEPs must be configured at the EMS from the NMS. However, no pre- configuration of a subset of M-leaves/NEs is needed. In scenario 4, OAM packets that are supported in RFC6371 and are targeted at all leaves can also be utilized. There is no P2MP OAM protocol extension. Only NMS configuration on M-leaves/sink MEPs is needed. A configuration of a subset of M-leave/sink MEPs at the EMS from the NMS is not necessary. No pre-configuration of a subset of M- leaves/NEs is needed. Considering some negative impacts such as the efficient use of a data communication network (DCN), insufficient manageability of network element (NE), traffic congestion at EMS/NMS, and heavy load for OAM packet processes at EMS/NMS, scenario 2 is required in MPLS-TP p2mp network. Koike, et al. Expires May 8, 2013 [Page 6] Internet-Draft MPLS-TP p2mp OAM framework February 2013 3.1.3. Refinement of existing requirements on P2MP transport path MPLS-TP RFCs are sufficiently mature in terms of the requirements and framework of MPLS-TP P2P. On the other hand, in terms of MPLS-TP P2MP, some parts of MPLS-TP RFCs and Recommendations could be refined and clarified. (R1) CV requirement of RFC5860 CV is ambiguously defined in RFC5860 "MPLS-TP OAM requirement". According to this definition of RFC5860, it seems to be source-MEP oriented and not correct in P2MP. Current text: The MPLS-TP OAM toolset MUST provide a function to enable an End Point to determine whether or not it is connected to specific End Point(s) by means of the expected PW, LSP, or Section. In unidirectional P2MP, the source MEP cannot determine whether or not it is connected to specific End Point(s). Therefore, in P2MP, the definition of connectivity verification should be corrected in P2MP framework draft and OAM Recommendation as follows. Proposed text: The MPLS-TP OAM toolset MUST provide a function to enable a sink End Point to determine whether or not it is connected to a specific source End Point by means of the expected PW or LSP. (R2) CC Requirement of RFC6371 According to RFC6371, it is assumed that CC means that CC OAM packet does not include either a source MEP or destination MEP. Only unidirectional P2MP is supported in MPLS-TP, so the continuity of the CC OAM packets are received by sink MEPs, and a sink MEP should notify the equipment fault management process of the detected defect. However, the following current text doesn't correctly describe the unidirectional feature that is specific to P2MP transport path. Therefore, the requirement should be modified. Current text in RFC: Proactive Continuity Check functions, as required in Section 2.2.2 of RFC5860 , are used to detect a loss of continuity (LOC) defect between two MEPs in an MEG. Proactive Connectivity Verification functions, as required in Section 2.2.3 of RFC5860 , 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. Proposed text: Proactive Continuity Check functions, as required in Section 2.2.2 of RFC5860, are used to detect a loss of continuity Koike, et al. Expires May 8, 2013 [Page 7] Internet-Draft MPLS-TP p2mp OAM framework February 2013 (LOC) defect from the source MEP to sink MEP(s). Proactive Connectivity Verification functions, as required in Section 2.2.3 of RFC5860, are used to detect an unexpected connectivity defect from the source MEP to sink MEP(s) (e.g., mismerging or misconnection), as well as unexpected connectivity within MEG with an unexpected source MEP. (R3) Optional requirements on CC-V OAM packets In a P2MP transport path, it is highly desirable that in order to save OAM bandwidth consumption, CV, when used, be linked with CC into CC-V OAM packets. 3.1.4. Addition and removal of branch tree in P2MP transport path When additional branches, in other words, additional destination NEs (leaves) need to be added to an existing transport path after a connection service is provided via the P2MP path, an operator must be capable of adding a new branch tree to the P2MP transport path flexibly from any point on the path without service interruption. The reason is that merging and crossover of the P2MP LSP branch tree must be rejected because it is not efficient in terms of network resources. As a result, the following requirement must be supported in the MPLS- TP P2MP transport path. 3.2. General aspects of P2MP OAM P2MP transport paths are unidirectional; therefore, there is generally no in-band return path as in the MPLS-TP transport path per se. However, there are basically two approaches for handling OAM requirements in P2MP MPLS-TP. The first one is used to report the results of the monitoring/measurement of OAM packets from the OAM target node to the EMS/NMS when the NMS usually instantiates OAM functions and requires the results of OAM monitoring functions. This approach is called RP-N. The second approach is the return path to a root (source MEP) of a P2MP path using different methods such as a unidirectional p2p transport paths, and other technology-layers, such as IP, Ethernet, and OTN, when an NE within which a root MEP resides instantiates OAM functions or receive results of OAM monitoring functions. This approach is called as RP-HE. The following requirements are supported in terms of network elements when considering RP-N. 1. OAM functions of a MEG of a P2MP transport path should be configurable using the EMS/NMS. Koike, et al. Expires May 8, 2013 [Page 8] Internet-Draft MPLS-TP p2mp OAM framework February 2013 2. Source nodes at which the source MEP reside and OAM packets are generated should receive OAM related information such as enabling/disabling OAM functions and setting/changing OAM attributes from the EMS/NMS on a P2MP transport path. 3. Sink nodes at which targeting MIPs or MEPs reside and OAM packets are parsed should report OAM related information such as OAM monitoring results and consequent OAM actions to the EMS/NMS. 4. Each OAM function of a P2MP transport path should be able to be independently configured using the EMS/NMS based on the classification of OAM functional requirements in RFC5860. 5. An on-demand OAM function must be able to perform an OAM function for only a specific target MIP or MEP as well as all MEPs in a P2MP transport path, as specified in Section 3.7 of RFC6371. 6. To manage M leaves(i.e., subset of all leaves) in an on-demand OAM function from the EMS/NMS, a unified mechanism must be provided. Note: Currently, sending an OAM packet that is targeted at a subset of M leaves by using an aggregating mechanism such as an OAM packet including several MIP or MEP identifiers is out of the scope of RFC6371 as described in Section 3.7 of that document. 7. Mismatches of configuration information between a root MEP and any leaf-MEP, at which proactive or on-demand monitoring is enabled, should be detected as a configuration mismatch alarm and be reported to the EMS/NMS by parsing received OAM packets, particularly when a static setting is applied. Generally when each OAM function is enabled, as described in Section 5.1 of RFC6371, the source MEP function should be enabled prior to the corresponding sink MEPs' function. Regarding configuration considerations, the following are additional requirements for unidirectional P2MP transport path, particularly when RP-HE does not exist. 8. The configuration of each OAM function between the source MEP and sink MEP(s) in an MEG of a transport path should be able to be synchronized using the NMS, when a new P2MP transport path is set. 9. OAM functions of a newly added/deleted branch transport path from any point of an existing transport path must be able to be configured and enabled/disabled on a newly integrated/combined P2MP transport path without affecting client traffic to existing Koike, et al. Expires May 8, 2013 [Page 9] Internet-Draft MPLS-TP p2mp OAM framework February 2013 end points of the P2MP transport path other than the added/removed branch transport path. 10.The configuration of newly added/removed specific sink MEP(s)to the existing source MEP in the MEG in proactive monitoring should be able to be synchronized with that of the source MEP by using the NMS. 11.The EMS/NMS should provide a tool for manually configuring consistent values of each piece of configuration information to a root MEP and all the related leaf MEPs in a MEG of a P2MP transport path for both pro-active and on-demand OAM functions. 12.Mismatches of configuration information between a leaf MEP and any other leaf MEP(s) or a root MEP and leaf MEP(s), at which proactive monitoring will be enabled, should be able to be detected through the configuration management process of the EMS/NMS as a configuration mismatch alarm or notification without receiving OAM packets from a source MEP(before OAM functions are enabled). Note: This requirement is not necessary if the EMS/NMS provides a tool to manually configure a consistent value of each piece of configuration information to a root MEP. 13.The enabling or disabling of proactive OAM functions and configuration mismatch alarms of the OAM functions must be independently configurable at each leaf-MEP as well as on all the leaf MEPs on a P2MP transport path, considering maintenances or a case in which one or more leaf MEPs is newly added or removed later. 14.Mismatches of configuration information between a leaf MEP and any other leaf MEP(s) or a root MEP and leaf MEP(s), at which on- demand OAM monitoring is enabled, must be detected as a configuration management process before conducting OAM functions. 3.3. OAM functions for proactive monitoring The proactive OAM functions are used to detect a fault/defect or to automatically reports a change in the status of a transport path. Koike, et al. Expires May 8, 2013 [Page 10] Internet-Draft MPLS-TP p2mp OAM framework February 2013 3.3.1. Continuity Check and Connectivity Verification(CC-V) The continuity Check function enables one or more leaf MEPs on a unidirectional P2MP transport path to monitor the continuity of OAM packets from root MEP and detect one or more loss of continuity(LOC) defects between the root MEP and leaf MEPs. The connectivity verification function enables one or more leaf MEPs on a P2MP transport path to monitor the connectivity of OAM packets from a specific root MEP and detect an unexpected connectivity defect between two MEGs(two P2MP transport paths) As described in Sections 2.2.2 and 2.2.3 of RFC5860, CC-V MUST be supported even when RP-HE does not exist. As described in RFC6371, CC-V OAM packets are used for a P2MP transport path. Defect detection mechanisms in P2MP transport paths are the same as those of the P2MP transport path specified in section 5.1.1 of RFC6371 . That is, loss of continuity(LoC) defect, mis- connectivity defect, period mis-configuration defect and unexpected encapsulation defect. Entry and exit criteria are also the same as those of the P2MP transport paths in RFC6371 . However, in a P2MP transport path, all the leaf MEPs that detect a defect must be indentified and differentiated from a normal leaf MEP(s), which does not detect a defect. Configuration is specified in Section 5.1.3 of RFC6371. The following configuration information must be configured: MEG-ID, MEP- ID, list of the other MEPs in the MEG that are different between the root MEP and leaf MEP, PHB for E-LSP and transmission rate. Consequent actions of a unidirectional P2MP transport path are also covered in Section 5.1.2 of RFC6371 . Operators should be able to enable/disable each consequent action. All MEPs inside a MEG need to be configured and retain the information when a proactive OAM function is enabled, as described in Section 5.1.3 of RFC6371. If there is no RP-HE, it is premised that the EMS/NMS exists. Therefore, the above parameters are statically configured. 3.3.2. Remote Defect Indication This OAM function is not available on a P2MP transport path when return paths do not exist. This OAM function can be implemented only Koike, et al. Expires May 8, 2013 [Page 11] Internet-Draft MPLS-TP p2mp OAM framework February 2013 in RP-HE. However, the return path is out of the scope of MPLS-TP requirements. 3.3.3. Alarm Reporting FFS 3.3.4. Lock Reporting For further study(FFS) 3.3.5. Packet Loss Measurement FFS 3.3.6. Packet Delay Measurement FFS 3.3.7. Client Failure Indication FFS 3.4. OAM functions for on-demand monitoring 3.4.1. Connectivity verification The connectivity verification function enables one or more leaf MEPs on a P2MP transport path to monitor the connectivity of OAM packets from a specific root MEP and detect an unexpected connectivity defect between two MEGs (two P2MP transport paths) 1. Connectivity verification functions MUST be supported when return paths in a unidirectional P2MP transport path do not exist. As described in RFC6371 , CC-V OAM packets are used for a P2MP transport path. Defect detection mechanisms in P2MP transport paths are the same as those of the P2MP transport path specified in section 5.1 of RFC6371. That is, loss of continuity defect, mis-connectivity defect, period mis-configuration defect and unexpected encapsulation defect. Entry and exit criteria are also the same as those of the P2MP transport path in RFC6371 . Moreover, consequent actions of a unidirectional P2MP transport path are also covered in Section 5.1.2 of the RFC  Koike, et al. Expires May 8, 2013 [Page 12] Internet-Draft MPLS-TP p2mp OAM framework February 2013 Regarding configuration consideration, the following additional requirements on a unidirectional P2MP transport path when a return path does not exist. 3.4.2. Packet loss measurement FFS 3.4.3. Diagnostic tests Diagnostic test functions MUST be supported when a return path in a unidirectional P2MP transport path doesn't exist. Other requirements are ffs. 3.4.4. Route Tracing Route tracing function MUST be supported when a return path in a unidirectional P2MP transport path doesn't exist. Other requirements are ffs. 3.4.5. Packet delay measurement FFS 3.5. OAM functions for administration control 3.5.1. Lock Instruct FFS. 4. Security Considerations This document does not raise any particular security considerations. 5. IANA Considerations There are no IANA actions required by this draft. Koike, et al. Expires May 8, 2013 [Page 13] Internet-Draft MPLS-TP p2mp OAM framework February 2013 6. References 6.1. Normative References  Niven-Jenkins, B., et all, "Requirements of an MPLS Transport Profile", RFC5654, September 2009  Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM in MPLS Transport Networks", RFC5860, May 2010  Busi, I., Dave, A. , "Operations, Administration and Maintenance Framework for MPLS-based Transport Networks ", RFC6371, September 2011  Frost, Dan.,et all, "A Framework for Point-to-Multipoint MPLS in Transport Networks", draft-mpls-tp-p2mp-framework-00, January 2013 6.2. Informative References None 7. Acknowledgments The author would like to thank all members (including MPLS-TP steering committee, the Joint Working Team, the MPLS-TP 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. Authors' Addresses Takafumi Hamano NTT firstname.lastname@example.org Masatoshi Namiki NTT email@example.com Yoshinori Koike NTT Email: firstname.lastname@example.org Koike, et al. Expires May 8, 2013 [Page 14]