Network Working Group Mustapha Aissaoui Internet Draft Peter Busschbach Expires: October 2009 Alcatel-Lucent Dave Allan Nortel Monique Morrow Luca Martini Cisco Systems Inc. Thomas Nadeau BT Yaakov Stein RAD Data Communications Editors April 15, 2009 Pseudo Wire (PW) OAM Message Mapping draft-ietf-pwe3-oam-msg-map-10.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 October 15, 2009. Nadeau, et al. Expires October 15, 2009 [Page 1] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 Copyright and License Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract This document specifies the mapping and notification of defect states between a Pseudo Wire and the Attachment Circuits (AC) of the end-to- end emulated service. This document covers the case whereby the ACs and the PWs are of the same type in accordance to the PWE3 architecture [RFC3985] such that a homogenous PW service can be constructed. 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. Table of Contents 1. Acknowledgments................................................4 2. Contributors...................................................4 3. Introduction...................................................5 4. Terminology....................................................5 5. Reference Model and Defect Locations...........................7 6. Abstract Defect States.........................................8 7. OAM Models....................................................10 8. PW Defect States and Defect Notifications.....................12 8.1. PW Defect Notification Mechanisms........................12 8.1.1. LDP Status TLV......................................13 8.1.2. L2TP Circuit Status AVP.............................14 8.1.3. BFD Diagnostic Codes................................16 8.2. PW Defect State Entry/Exit...............................18 8.2.1. PW receive defect state entry/exit criteria.........18 8.2.2. PW transmit defect state entry/exit criteria........19 9. Procedures for ATM PW Service.................................19 Nadeau, et al. Expires October 15, 2009 [Page 2] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 9.1. AC receive defect state entry/exit criteria..............19 9.2. AC transmit defect state entry/exit criteria.............20 9.3. Consequent Actions.......................................21 9.3.1. PW receive defect state entry/exit..................21 9.3.2. PW transmit defect state entry/exit.................22 9.3.3. PW defect state in ATM Port Mode PW Service.........22 9.3.4. AC receive defect state entry/exit..................22 9.3.5. AC transmit defect state entry/exit.................24 10. Procedures for Frame Relay PW Service........................24 10.1. AC receive defect state entry/exit criteria.............24 10.2. AC transmit defect state entry/exit criteria............24 10.3. Consequent Actions......................................25 10.3.1. PW receive defect state entry/exit.................25 10.3.2. PW transmit defect state entry/exit................25 10.3.3. PW defect state in the FR Port Mode PW service.....26 10.3.4. AC receive defect state entry/exit.................26 10.3.5. AC transmit defect state entry/exit................26 11. Procedures for TDM PW Service................................26 11.1. AC receive defect state entry/exit criteria.............27 11.2. AC transmit defect state entry/exit criteria............27 11.3. Consequent Actions......................................28 11.3.1. PW receive defect state entry/exit.................28 11.3.2. PW transmit defect state entry/exit................28 11.3.3. AC receive defect state entry/exit.................28 12. Procedures for CEP PW Service................................29 12.1. Defect states...........................................30 12.1.1. PW receive defect state entry/exit criteria........30 12.1.2. PW transmit defect state entry/exit criteria.......30 12.1.3. AC receive defect state entry/exit criteria........30 12.1.4. AC transmit defect state entry/exit criteria.......30 12.2. Consequent actions......................................31 12.2.1. PW receive defect state entry/exit.................31 12.2.2. PW transmit defect state entry/exit................31 12.2.3. AC receive defect state entry/exit.................31 13. Security Considerations......................................32 14. IANA Considerations..........................................32 15. References...................................................32 15.1. Normative References....................................32 15.2. Informative References..................................33 16. Editor's Addresses...........................................34 Informative Appendix A: Native Service Management................35 - Frame Relay Management.....................................35 - ATM Management.............................................36 Informative Appendix B: PW Defects and Detection tools...........37 - PW Defects.................................................37 - Packet Loss.............................................38 - PW Defect Detection Tools..................................38 Nadeau, et al. Expires October 15, 2009 [Page 3] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 1. Acknowledgments The editors would like to acknowledge the important contributions of Hari Rakotoranto, Eric Rosen, Mark Townsley, Michel Khouderchah, Bertrand Duvivier, Vanson Lim, Chris Metz, Ben Washam, Tiberiu Grigoriu, Neil McGill, and Amir Maleki. 2. Contributors Thomas D. Nadeau, tom.nadeau@bt.com Monique Morrow, mmorrow@cisco.com Peter B. Busschbach, busschbach@alcatel-lucent.com Mustapha Aissaoui, mustapha.aissaoui@alcatel-lucent.com Matthew Bocci, matthew.bocci@alcatel-lucent.co.uk David Watkinson, david.watkinson@alcatel-lucent.com Yuichi Ikejiri, y.ikejiri@ntt.com Kenji Kumaki, kekumaki@kddi.com Satoru Matsushima, satoru@ft.solteria.net David Allan, dallan@nortel.com Himanshu Shah, hshah@ciena.com Simon Delord, sdelord@uecomm.com.au Vasile Radoaca, vasile.radoaca@alcatel-lucent.com Carlos Pignataro, cpignata@cisco.com Luca Martini, lmartini@cisco.com Yaakov (J) Stein, yaakov_s@rad.com Teruyuki Oya, teruyuki.oya@tm.softbank.co.jp Nadeau, et al. Expires October 15, 2009 [Page 4] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 3. Introduction This document specifies the mapping and notification of defect states between a Pseudo Wire and the Attachment Circuits (AC) of the end- to-end emulated service. It covers the case whereby the ACs and the PWs are of the same type in accordance to the PWE3 architecture [RFC3985] such that a homogeneous PW service can be constructed. This document is motivated by the requirements put forth in [RFC4377] and [RFC3916]. Its objective is to standardize the behavior of PEs with respects to failures on PWs and ACs, so that there is no ambiguity about the alarms generated and consequent actions undertaken by PEs in response to specific failure conditions. This document covers PWE over MPLS PSN, PWE over MPLS-IP PSN and PWE over L2TP-IP PSN. The Ethernet PW service is covered in a separate document [ETH-OAM- IWK]. 4. Terminology AIS Alarm Indication Signal AC Attachment circuit BDI Backward Defect Indication CC Continuity Check CE Customer Edge CPCS Common Part Convergence Sub-layer DLC Data Link Connection FDI Forward Defect Indication FRBS Frame Relay Bearer Service IWF Interworking Function LB Loopback NE Network Element NS Native Service Nadeau, et al. Expires October 15, 2009 [Page 5] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 OAM Operations and Maintenance PE Provider Edge PW Pseudowire PSN Packet Switched Network RDI Remote Defect Indication SDU Service Data Unit VCC Virtual Channel Connection VPC Virtual Path Connection The rest of this document will follow the following conventions. The words "defect" and "fault" are used inter-changeably to mean a condition which causes user packets not to be forwarded between the CE endpoints of the PW service. The words "defect notification" and "defect indication" are used inter-changeably to mean an OAM message generated by a PE and sent to other nodes in the network to convey the defect state local to this PE. The PW can ride over three types of Packet Switched Network (PSN). A PSN which makes use of LSPs as the tunneling technology to forward the PW packets will be referred to as an MPLS PSN. A PSN which makes use of MPLS-in-IP tunneling [RFC4023], with an MPLS shim header used as PW demultiplexer, will be referred to as an MPLS-IP PSN. A PSN which makes use of L2TPv3 [RFC3931] as the tunneling technology with the L2TPv3 Session ID as the PW demultiplexer will be referred to as L2TP-IP PSN. If LSP-Ping [RFC4379] is run over a PW as described in [RFC4377], it will be referred to as VCCV-Ping. If BFD is run over a PW as described in [RFC4377], it will be referred to as VCCV-BFD [VCCV-BFD]. In the context of this document a PE forwards packets between an AC and a PW. The other PE that terminates the PW is the peer PE or remote PE and the attachment circuit associated with the far-end PW termination is the remote AC. Nadeau, et al. Expires October 15, 2009 [Page 6] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 Defects are discussed in the context of defect states, and the criteria to enter and exit the defect state. The direction of defects is discussed from the perspective of the observing PE. A receive defect is one that impacts information transfer to the observing PE. It impacts the observing PEs ability to receive information. A transmit defect is one that uniquely impacts information sent or relayed by the observing PE. A receive defect generally also impacts information sent or relayed by the observing PE. Therefore the receive defect state is considered to be a superset of the two defect states. Thus, when a PE enters both receive and transmit defect states related to the same PW service, the receive defect takes precedence over the transmit defect in terms of the consequent actions. A forward defect indication is sent in the same direction as the user traffic impacted by the defect. A reverse defect indication is sent in the opposite direction of the traffic impacted by the defect. 5. Reference Model and Defect Locations Figure 1 illustrates the PWE3 network reference model with an indication of the possible defect locations. This model will be referenced in the remainder of this document for describing the OAM procedures. ACs PSN tunnel ACs +----+ +----+ +----+ | PE1|==================| PE2| +----+ | |---(a)---(b)..(c)......PW1..(d)..(c)..(f)---(e)---| | | CE1| (N1) | | | | (N2) |CE2 | | |----------|............PW2.............|----------| | +----+ | |==================| | +----+ ^ +----+ +----+ ^ | Provider Edge 1 Provider Edge 2 | | | |<-------------- Emulated Service ---------------->| Customer Customer Edge 1 Edge 2 Figure 1: PWE3 Network Defect Locations Nadeau, et al. Expires October 15, 2009 [Page 7] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 In all interworking scenarios described in this document, it is assumed the AC and the PW are of the same type at PE1. The procedures described in this document apply to PE1. PE2 implements the identical functionality for a homogeneous service (although it is not required to as long as the notifications across the PWs are consistent). The following is a brief description of the defect locations: a. Defect in the first native service network (N1). This covers any defect in the N1 which impacts all or a subset of ACs terminating in PE1. The defect is conveyed to PE1 and to the remote native service network (N2) using the native service specific OAM defect indication. b. Defect on a PE1 AC interface. c. Defect on a PE1 PSN interface. d. Defect in the PSN network. This covers any defect in the PSN which impacts all or a subset of PWs terminating in a PE. The defect is conveyed to the PE using a PSN and/or a PW specific OAM defect indication. Note that both data plane defects and control plane defects must be taken into consideration. Even though control messages may follow a different path than the PW data plane traffic, a control plane failure may affect the PW status. e. Defect in the second native service network (N2). This covers any defect in N2 which impacts all or a subset of ACs terminating in PE2 (which is considered a remote AC defect in the context of procedures outlined in this draft). The defect is conveyed to PE2 and to the remote native service network (N1) using the native service OAM defect indication. f. Defect on a PE2 AC interface (which is also considered a remote AC defect in the context of this draft). 6. Abstract Defect States PE1 must track four defect states that reflect the observed states of both directions of the PW service on both the AC and the PW sides. Defects may impact one or both directions of the PW service. The observed state is a combination of defects directly detected by PE1 and defects it has been made aware of via notifications. Nadeau, et al. Expires October 15, 2009 [Page 8] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 +-----+ ----AC receive---->| |-----PW transmit----> CE1 | PE1 | PE2/CE2 <---AC transmit-----| |<----PW receive----- +-----+ (arrows indicate direction of user traffic impacted by a defect) Figure 2: Receive and Transmit Defect States PE1 will directly detect or be notified of AC receive or PW receive defects as they occur upstream of PE1 and impact traffic being sent to PE1. As a result, PE1 enters the AC or PW receive defect state. In Figure 2, PE1 may be notified of a receive defect in the AC by receiving a Forward Defect indication, e.g., ATM AIS, from an ATM switch in network N1. This defect notification indicates that user traffic sent by CE1 may not be received by PE1 due to a defect. PE1 can also directly detect an AC receive defect if it resulted from a failure of the receive side in the local port or link over which the AC is configured. Similarly, PE1 may detect or be notified of a receive defect in the PW by receiving a Forward Defect indication from PE2. If PW status is used for fault notification, this message will indicate a Local PSN- facing PW (egress) Transmit Fault or a Local Attachment Circuit (ingress) Receive Fault at PE2, as described in Section 8.1.1. . This defect notification indicates that user traffic sent by CE2 may not be received by PE1 due to a defect. As a result, PE1 enters the PW receive defect state. Note that a Forward Defect indication is sent in the same direction as the user traffic impacted by the defect. Generally, a PE cannot detect transmit defects directly and will therefore need to be notified of AC transmit or PW transmit defects by other devices. In Figure 2, PE1 may be notified of a transmit defect in the AC by receiving a Reverse Defect indication, e.g., ATM RDI, from CE1. This defect relates to the traffic sent by PE1 to CE1 on the AC. Similarly, PE1 may be notified of a transmit defect in the PW by receiving a Reverse Defect indication from PE2. If PW status is used for fault notification, this message will indicate a Local PSN-facing PW (ingress) Receive Fault or a Local Attachment Circuit (egress) Transmit Fault at PE2, as described in Section 8.1.1. . This defect Nadeau, et al. Expires October 15, 2009 [Page 9] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 impacts the traffic sent by PE1 to CE2. As a result, PE1 enters the PW transmit defect state. Note that a Reverse Defect indication is sent in the reverse direction to the user traffic impacted by the defect. The procedures outlined in this document define the entry and exit criteria for each of the four states with respect to the set of PW services within the document scope and the consequent actions that PE1 must perform. When a PE enters both receive and transmit defect states related to the same PW service, then the receive defect takes precedence over transmit defect in terms of the consequent actions. 7. OAM Models A homogeneous PW service forwards packets between an AC and a PW of the same type. It thus implements both a Native Service OAM mechanism and a PW OAM mechanism. PW OAM defect notification messages are described in Section 8.1. Native Service (NS) OAM messages are described in Appendix A. This document defines two different modes for operating OAM on a PW service which dictate the mapping between the NS OAM the PW OAM defect notification messages. The first one operates a single emulated OAM loop end-to-end between the endpoints of the PW service. This is referred to as "single emulated OAM loop" mode and is illustrated in Figure 3. |<----- AC ----->|<----- PW ----->|<----- AC ----->| | | | | ___ ===============_ |CE|---=NS-OAM=>---(---=NS-OAM=>---)---=NS-OAM=>---|CE| =============== / \ / ---=PW-OAM=>--- Figure 3: Single Emulated OAM Loop mode This mode implements the following behavior. We use the words upstream and downstream to identify PEs in relation to a specific traffic direction. a. An upstream PE node MUST transparently relay NS OAM messages over the PW. Nadeau, et al. Expires October 15, 2009 [Page 10] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 b. An upstream PE node MUST signal local failures affecting the AC using a NS defect notification OAM message sent over the PW. In the case that it is not possible to generate NS OAM messages (e.g. because the defect interferes with NS OAM message generation) the PE MUST signal local failures affecting the AC using a PW defect notification OAM message. c. An upstream PE node MUST signal local failures affecting the PW using a PW defect notification OAM message. d. A downstream PE node MUST insert a NS defect notification OAM message into the AC when it detects or is notified of a defect in the PW or remote AC. This includes receiving a PW defect notification message and translating it into a NS defect notification OAM message over the AC. The latter is required for handling defects signaled by a peer PE with PW OAM messaging. The "single emulated OAM loop" mode is suitable for PW services which have a widely deployed NS OAM mechanism that operates within the AC. This document specifies the use of this mode for ATM PW, TDM PW, and CEP PW services. It is the default mode of operation for all ATM cell-mode PW services and the only mode specified for TDM and CEP PW services. It is optional for AAL5 PDU transport and AAL5 SDU transport modes. The second mode operates three OAM loops which join at the AC/PW boundary of a PE. This is referred to as "coupled OAM loops" mode and is illustrated in Figure 4. |<----- AC ----->|<----- PW ----->|<----- AC ----->| | | | | __ ===============__ |CE|---=NS-OAM=>---(---------------)---=NS-OAM=>---|CE| \ =============== / \ / \ / -------=PW-OAM=>------ Figure 4: Coupled OAM Loops mode This mode implements the following behavior. We use the words upstream and downstream to identify PEs in relation to a specific traffic direction. a. An upstream PE node MUST terminate and translate a received NS defect notification OAM message to a PW defect notification message. Nadeau, et al. Expires October 15, 2009 [Page 11] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 b. An upstream PE node MUST signal local failures affecting the AC using a PW defect notification OAM message to the remote PE. c. An upstream PE node MUST signal local failures affecting the PW using a PW defect notification OAM message. d. A downstream PE node MUST insert a NS defect notification OAM message into the AC when it detects or is notified of a defect in the PW or remote AC. This includes support receiving a PW defect notification message and translating it into a NS defect notification OAM message over the AC. This document specifies the "coupled OAM loops" mode as the default mode for a FR PW service and for ATM AAL5 PDU transport and AAL5 SDU transport services and as optional for ATM VCC cell mode services. It does not specify the use of this mode for TDM PW, CEP PW, and ATM VPC cell mode PW services. In the latter last case, a PE node must pass transparently VC-level (F5) ATM OAM cells over the PW while terminating and translating VP-level (F4) OAM cells. Thus, it cannot operate a pure "coupled OAM loops" mode. 8. PW Defect States and Defect Notifications 8.1. PW Defect Notification Mechanisms For a MPLS PSN and a MPLS-IP PSN, a PE node which establishes a PW using LDP SHALL use LDP status TLV as the mechanism for AC and PW status and defect notification [RFC4447]. Additionally, a PE node MAY use VCCV-BFD Connectivity Verification (CV) types for fault detection only but SHOULD notify the remote PE using LDP Status TLV. These CV types are 0x04 and 0x10 [VCCV-BFD]. A PE node which establishes a PW using other means than LDP, e.g., static configuration, MAY use VCCV-BFD CV types for AC and PW status and defect notification. These CV types are 0x08 and 0x20 [VCCV-BFD]. These CV types SHOULD NOT be used when the PW is established with the LDP control plane. For a L2TP-IP PSN, A PE node SHOULD use the Circuit Status AVP as the mechanism for AC and PW status and defect notification. In its most basic form, the Circuit Status AVP [RFC3931] in a Set-Link-Info (SLI) message can signal active/inactive AC status. The Circuit Status AVP is proposed to be extended to convey status and defects in the AC and the PSN-facing PW in both ingress and egress directions, i.e., four independent status bits without the need to tear down the sessions or control connection [L2TP-Status]. Nadeau, et al. Expires October 15, 2009 [Page 12] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 When a PE does not support the Circuit Status AVP, it MAY use the StopCCN and the CDN message to bring down L2TP sessions in a similar way LDP uses the Label Withdrawal to bring down a PW. A PE node may use the StopCCN to shutdown the L2TP control connection, and implicitly all L2TP sessions associated with that control connection without any explicit session control messages. This is in the case of a failure which impacts all L2TP sessions, i.e., all PWs, managed by the control connection. It may use the CDN message to disconnect a specific L2TP session when a failure affects a specific PW. Additionally, a PE node MAY use VCCV-BFD CV types 0x04 and 0x10 for fault detection only but SHOULD notify the remote PE using the Circuit Status AVP. A PE node which establishes a PW using other means than L2TP control plane MAY use VCCV-BFD CV types 0x08 and 0x20 for AC and PW status and defect notification. These CV types SHOULD NOT be used when the PW is established with the L2TP control plane. 8.1.1. LDP Status TLV [RFC4446] defines the following PW status code points: 0x00000000 - Pseudo Wire forwarding (clear all failures) 0x00000001 - Pseudo Wire Not Forwarding 0x00000002 - Local Attachment Circuit (ingress) Receive Fault 0x00000004 - Local Attachment Circuit (egress) Transmit Fault 0x00000008 - Local PSN-facing PW (ingress) Receive Fault 0x00000010 - Local PSN-facing PW (egress) Transmit Fault [RFC4447] specifies that "Pseudo Wire forwarding" code point is used to clear all faults. It also specifies that "Pseudo Wire Not Forwarding" code is used to convey any other defect that cannot be represented by the other code points. The code points used in the LDP status TLV in a PW status notification message convey the defect view of the originating PE. The originating PE conveys this state in the form of a forward defect or a reverse defect indication. The forward and reverse defect indication definitions used in this document map to the LDP Status TLV codes as follows: Forward defect indication - corresponds to the logical OR of Local Attachment Circuit (ingress) Receive Fault, Nadeau, et al. Expires October 15, 2009 [Page 13] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 Local PSN-facing PW (egress) Transmit Fault, and PW not Forwarding Fault Reverse defect indication - corresponds to the logical OR of Local Attachment Circuit (egress) Transmit Fault and Local PSN-facing PW (ingress) Receive Fault A PE SHALL thus use PW status notification messages to report all failures affecting the PW service including, but not restricted, to the following: - Failures detected through defect detection mechanisms in the MPLS and MPLS-IP PSN - Failures detected through VCCV-Ping or VCCV-BFD CV types 0x04 and 0x10 for fault detection only - Failures within the PE that result in an inability to forward traffic between the AC and the PW - Failures of the AC or in the L2 network affecting the AC as per the rules detailed in Section 7. for the "single emulated OAM loop" mode and "coupled OAM loops" mode. Note that there are two situations which require PW label withdrawal as opposed to a PW status notification by the PE. The first one is when the PW is taken administratively down in accordance to [RFC4447]. The second one is when the Target LDP session established between the two PEs is lost. In the latter case, the PW labels will need to be re-signaled when the Targeted LDP session is re- established. 8.1.2. L2TP Circuit Status AVP [RFC3931] defines the Circuit Status AVP in the Set-Link-Info (SLI) message to exchange initial status and status changes in the circuit to which the pseudowire is bound. [L2TP-Status] defines extensions to the Circuit Status AVP that are analogous to the PW Status TLV defined for LDP. Consequently, for L2TP-IP, the Circuit Status AVP Nadeau, et al. Expires October 15, 2009 [Page 14] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 is used in the same fashion as the PW Status described in the previous section. If the extended Circuit Status bits are not supported, and instead only the "A-bit" (Active) is used as described in [RFC3931], a PE MAY use CDN messages to clear L2TPv3 sessions in the presence of session- level failures detected in the L2TP-IP PSN. A PE MUST set the Active bit in the Circuit Status to clear all faults, and it MUST clear the Active bit in the Circuit Status to convey any defect that cannot be represented explicitly with specific Circuit Status flags from [RFC3931] or [L2TP-Status]. The forward and reverse defect indication definitions used in this document map to the L2TP Circuit Status AVP as follows: Forward defect indication - corresponds to the logical OR of Local Attachment Circuit (ingress) Receive Fault, Local PSN-facing PW (egress) Transmit Fault, and PW not Forwarding Fault Reverse defect indication- corresponds to the logical OR of Local Attachment Circuit (egress) Transmit Fault and Local PSN-facing PW (ingress) Receive Fault The status notification conveys the defect view of the originating LCCE (PE). When the extended Circuit Status definition of [L2TP-Status] is supported, a PE SHALL use the Circuit Status to report all failures affecting the PW service including, but not restricted, to the following: - Failures detected through defect detection mechanisms in the L2TP-IP PSN. - Failures detected through VCCV-Ping or VCCV-BFD CV types 0x04 and 0x10 for fault detection only Nadeau, et al. Expires October 15, 2009 [Page 15] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 - Failures within the PE that result in an inability to forward traffic between the AC and the PW - Failures of the AC or in the L2 network affecting the AC as per the rules detailed in Section 7. for the "single emulated OAM loop" mode and the "coupled OAM loops" mode. When the extended Circuit Status definition of [L2TP-Status] is not supported, a PE SHALL use the A-bit in the Circuit Status AVP in SLI to report: - Failures of the AC or in the L2 network affecting the AC as per the rules detailed in Section 7. for the "single emulated OAM loop" mode and the "coupled OAM loops" mode. When the extended Circuit Status definition of [L2TP-Status] is not supported, a PE MAY use the CDN and StopCCN messages in a similar way to an MPLS PW label withdrawal to report: - Failures detected through defect detection mechanisms in the L2TP-IP PSN (using StopCCN) - Failures detected through VCCV (pseudowire level) (using CDN) - Failures within the PE that result in an inability to forward traffic between ACs and PW (using CDN) For ATM L2TPv3 pseudowires, in addition to the Circuit Status AVP, a PE MAY use the ATM Alarm Status AVP [RFC4454] to indicate the reason for the ATM circuit status and the specific alarm type, if any. This AVP is sent in the SLI message to indicate additional information about the ATM circuit status. L2TP control connections use Hello messages as a keep-alive facility. It is important to note that if a PSN failure is such that the loss of connectivity is detected when it triggers a keep-alive timeouts, the control connection is cleared. L2TP Hello messages are sent in- band with the data plane, with respect to the source and destination addresses, IP protocol number and UDP port (when UDP is used). 8.1.3. BFD Diagnostic Codes [BFD] defines a set of diagnostic codes that partially overlap with failures that can be communicated through LDP Status TLV or L2TP Circuit Status AVP. This section describes the behavior of the PE Nadeau, et al. Expires October 15, 2009 [Page 16] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 nodes with respect to using one or both methods for detecting and propagating defect state. For a MPLS-PSN, the PEs negotiate the use of the VCCV capabilities when the label mapping messages are exchanged to establish the two directions of the PW. An OAM capability TLV is signaled as part of the PW FEC interface parameters TLV. For L2TP-IP PSNs, the PEs negotiate the use of VCCV during the pseudowire session initialization using the VCCV AVP [RFC5085]. The CV Type Indicators field in this TLV defines a bitmask used to indicate the specific OAM capabilities that the PE can make use of over the PW being established. A CV type of 0x04 or 0x10 indicates that BFD is used for PW fault detection only [VCCV-BFD]. These CV types MAY be used any time the PW is established using LDP or L2TP control planes. In this mode, only the following diagnostic (Diag) codes specified in [BFD] will be used, they are: 0 - No diagnostic 1 - Control detection time expired 7 - Administratively Down A PE MUST use code 0 to indicate to its peer PE that is correctly receiving BFD control messages. It MUST use the second code to indicate that to its peer it has stopped receiving BFD control messages. A PE shall use "Administrative down" to bring down the BFD session when the PW is brought down administratively. All other defects, such as AC/PW defects and PE internal failures that prevent it from forwarding traffic, MUST be communicated through LDP Status TLV in the case of MPLS PSN or MPLS-IP PSN, or through the appropriate L2TP codes in the Circuit Status AVP in the case of L2TP- IP PSN. A CV type of 0x08 or 0x20 in the OAM capabilities TLV indicates that BFD is used for both PW fault detection and Fault Notification. In addition to the above diagnostic codes, a PE used the following codes to signal AC defects and other defects impacting forwarding over the PW service: 6 -- Concatenated Path Down 8 -- Reverse Concatenated Path Down Nadeau, et al. Expires October 15, 2009 [Page 17] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 TBD -- PW not forwarding A PE MAY use the "PW not forwarding" code to convey any other defect that cannot be represented by code points 6 and 8. In general, this applies to a defect that does not cause the PW to be torn down. This implies the BFD session must not be brought down when this defect exists. The forward and reverse defect indication definitions used in this document map to the BFD codes as follows: Forward defect indication - corresponds to the logical OR of Concatenated Path Down and PW not forwarding Reverse defect indication- corresponds to Reverse Concatenated Path Down These diagnostic codes are used to signal receive and reverse defect states respectively when the PEs negotiated the use of BFD as the mechanism for AC and PW fault detection and status signaling notification. As stated in Section 8.1. , these CV types SHOULD NOT be used when the PW is established with the LDP or L2TP control plane. 8.2. PW Defect State Entry/Exit 8.2.1. PW receive defect state entry/exit criteria PE1 will enter the PW receive defect state if one or more of the following occurs: - It receives a forward defect indication from PE2, which indicates PE2 detected or was notified of a PW fault downstream of it or that there was a receive defect on remote AC. - It detects loss of connectivity on the PSN tunnel upstream of PE1 which affects the traffic it receives from PE2. - It detects a loss of PW connectivity through VCCV-BFD or VCCV-PING which affects the traffic it receives from PE2. Note that if the PW control session between the PEs fails, the PW is torn down and needs to be re-established. This includes failure of Nadeau, et al. Expires October 15, 2009 [Page 18] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 the T-LDP session, the L2TP session, or the L2TP control connection. However, the consequent actions towards the ACs are the same as if the PW entered the receive defect state. PE1 will exit the PW receive defect state when the following conditions are true. Note that this may result in a transition to the PW operational state or the PW transmit defect state. - All defects it had previously detected have disappeared, and - PE2 cleared the forward defect indication if applicable. 8.2.2. PW transmit defect state entry/exit criteria PE1 will enter the PW transmit defect state if the following conditions are true: - it receives a reverse defect indication from PE2 which indicates that PE2 detected or was notified of a PW fault upstream of it or that there was a transmit fault on the remote AC, and - it is not already in the PW receive defect state. PE1 will exit the transmit defect state if it receives an OAM message from PE2 clearing the reverse defect indication, or it has entered the PW receive defect state. For a PWE3 over a L2TP-IP PSN using the basic Circuit Status AVP [RFC3931], the PW transmit defect state is not valid and a PE can only enter the PW receive defect state. 9. Procedures for ATM PW Service 9.1. AC receive defect state entry/exit criteria When operating in the "coupled OAM loops" mode, PE1 enters the AC receive defect state if any of the following conditions are met: a. It detects or is notified of a physical layer fault on the ATM interface. b. It receives an end-to-end F4 AIS OAM flow on a VP AC, or an end-to-end F5 AIS OAM flow on a VC AC, Nadeau, et al. Expires October 15, 2009 [Page 19] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 indicating that the ATM VPC or VCC is down in the adjacent L2 ATM network. c. It receives a segment F4 AIS OAM flow on a VP AC, or a segment F5 AIS OAM flow on a VC AC, provided that the operator has provisioned segment OAM and the PE is not a segment end-point d. It detects loss of connectivity on the ATM VPC/VCC while terminating segment or end-to-end ATM continuity check (ATM CC) cells with the local ATM network and CE. When operating in the "coupled OAM loops" mode, PE1 exits the AC Receive defect state when all defects it had previously detected have disappeared. When operating in the "single emulated OAM loop" mode, PE1 enters the AC receive defect state if any of the following conditions are met: a. It detects or is notified of a physical layer fault on the ATM interface. b. It detects loss of connectivity on the ATM VPC/VCC while terminating segment ATM continuity check (ATM CC) cells with the local ATM network and CE. When operating in the "single emulated OAM loop" mode, PE1 exits the AC receive defect state when all defects it had previously detected have disappeared. The exact conditions under which a PE enters and exits the AIS state, or declares that connectivity is restored via ATM CC are defined in Section 9.2 of ITU-T Recommendation I.610 [ITU-T I.610]. 9.2. AC transmit defect state entry/exit criteria When operating in the coupled-loop mode, PE1 enters the AC transmit defect state if any of the following conditions are met: a. It terminates an end-to-end F4 RDI OAM flow, in the case of a VPC, or an end-to-end F5 RDI OAM flow, in the case of a VCC, indicating that the ATM VPC or VCC is down in the adjacent L2 ATM. b. It receives a segment F4 RDI OAM flow on a VP AC, or a segment F5 RDI OAM flow on a VC AC, provided that the Nadeau, et al. Expires October 15, 2009 [Page 20] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 operator has provisioned segment OAM and the PE is not a segment end-point PE1 exits the AC transmit defect state if the AC state transitions to working or to the AC receive defect state. The exact conditions for exiting the RDI state are described in Section 9.2 of ITU-T Recommendation I.610 [ITU-T I.610]. Note that the AC transmit defect state is not valid when operating in the "single emulated OAM loop" mode as PE1 transparently forwards the received RDI cells as user cells over the ATM PW to the remote CE. 9.3. Consequent Actions In the reminder of this section, the text refers to AIS, RDI and CC without specifying whether it is an F4 (VP-level) flow or an F5 (VC- level) flow, or whether it is an end-to-end or a segment flow. Precise ATM OAM procedures for each type of flow are specified in Section 9.2 of ITU-T Recommendation I.610 [ITU-T I.610]. 9.3.1. PW receive defect state entry/exit On entry to the PW receive defect state: a. PE1 MUST commence AIS insertion into the corresponding AC. b. PE1 MUST cease generation of CC cells on the corresponding AC, if applicable. c. If the PW failure was detected by PE1 without receiving a forward defect indication from PE2, PE1 MUST assume PE2 has no knowledge of the defect and MUST notify PE2 in the form of a reverse defect indication. On exit from the PW receive defect state: a. PE1 MUST cease AIS insertion into the corresponding AC. b. PE1 MUST resume any CC cell generation on the corresponding AC, if applicable. c. PE1 MUST clear the reverse defect indication to PE2 if applicable. Nadeau, et al. Expires October 15, 2009 [Page 21] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 9.3.2. PW transmit defect state entry/exit On entry to the PW Transmit Defect State: a. PE1 MUST commence RDI insertion into the corresponding AC. b. If the PW failure was detected by PE1 without receiving a reverse defect indication from PE2, PE1 MUST assume PE2 has no knowledge of the defect and MUST notify PE2 in the form of a forward defect indication. On exit from the PW Transmit Defect State: a. PE1 MUST cease RDI insertion into the corresponding AC. b. PE1 MUST clear the forward defect indication to PE2 if applicable. 9.3.3. PW defect state in ATM Port Mode PW Service In case of transparent cell transport PW service, i.e., "port mode", where the PE does not keep track of the status of individual ATM VPCs or VCCs, a PE cannot relay PW defect state over these VCCs and VPCs. If ATM CC is run on the VCCs and VPCs end-to-end (CE1 to CE2), or on a segment originating and terminating in the ATM network and spanning the PSN network, it will timeout and cause the CE or ATM switch to enter the ATM AIS state. 9.3.4. AC receive defect state entry/exit On entry to the AC receive defect state and when operating in the "coupled OAM loops" mode: a. PE1 MUST send a forward defect indication to PE2. b. PE1 MUST commence insertion of ATM RDI cells into the AC towards CE1. When operating in the "single emulated OAM loop" mode, PE1 must be able to support two options, subject to the operator's preference. The default option is the following: On entry to the AC receive defect state: Nadeau, et al. Expires October 15, 2009 [Page 22] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 a. PE1 MUST transparently relay ATM AIS cells, or, in the case of a local AC defect, commence insertion of ATM AIS cells into the corresponding PW towards CE2. b. If the defect interferes with NS OAM message generation, PE1 MUST send a forward defect indication to PE2. c. PE1 MUST cease the generation of CC cells on the corresponding PW, if applicable. In certain operational models, for example in the case that the ATM access network is owned by a different provider than the PW, an operator may want to distinguish between defects detected in the ATM access network and defects detected on the AC directly adjacent to the PE. Therefore, the following option must also be supported: a. PE1 MUST transparently relay ATM AIS cells over the corresponding PW towards CE2. b. Upon detection of a defect on the ATM interface on the PE or in the PE itself, PE1 MUST send a forward defect indication to PE2. c. PE1 MUST cease generation of CC cells on the corresponding PW, if applicable. On exit from the AC receive defect state and when operating in the "coupled OAM loops" mode: a. PE1 MUST clear the forward defect indication to PE2. b. PE1 MUST cease insertion of ATM RDI cells into the AC. On exit from the AC receive defect state and when operating in the "single emulated OAM loop" mode: a. PE1 MUST cease insertion of ATM AIS cells into the corresponding PW. b. PE1 MUST clear the forward defect indication to PE2 if applicable. c. PE1 MUST resume any CC cell generation on the corresponding PW, if applicable. Nadeau, et al. Expires October 15, 2009 [Page 23] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 9.3.5. AC transmit defect state entry/exit On entry to the AC transmit defect state and when operating in the "coupled OAM loops" mode: a. PE1 MUST send a reverse defect indication to PE2. On exit from the AC transmit defect state and when operating in the "coupled OAM loops" mode: a. PE1 MUST clear the reverse defect indication to PE2. 10. Procedures for Frame Relay PW Service 10.1. AC receive defect state entry/exit criteria PE1 enters the AC receive defect state if one or more of the following conditions are true: a. A PVC is not deleted from the Frame Relay network and the Frame Relay network explicitly indicates in a full status report (and optionally by the asynchronous status message) that this Frame Relay PVC is inactive [ITU-T Q.933]. In this case, this status maps across the PE to the corresponding PW only. b. The Link Integrity Verification (LIV) indicates that the link from the PE to the Frame Relay network is down [ITU-T Q.933]. In this case, the link down indication maps across the PE to all corresponding PWs. c. A physical layer alarm is detected on the FR interface. In this case, this status maps across the PE to all corresponding PWs. PE1 exits the AC receive defect state when all defects it had previously detected have disappeared. 10.2. AC transmit defect state entry/exit criteria The AC transmit defect state is not valid for a FR AC. Nadeau, et al. Expires October 15, 2009 [Page 24] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 10.3. Consequent Actions 10.3.1. PW receive defect state entry/exit On entry to the PW receive defect state: a. PE1 MUST set the Active bit = 0 for the corresponding FR AC in a full status report, and optionally in an asynchronous status message, as per Q.933 annex A [ITU-T Q.933]. b. If the PW failure was detected by PE1 without receiving a forward defect indication from PE2, PE1 MUST assume PE2 has no knowledge of the defect and MUST notify PE2 in the form of a reverse defect indication. On exit from the PW receive defect state: a. PE1 MUST set the Active bit = 1 for the corresponding FR AC in a full status report, and optionally in an asynchronous status message, as per Q.933 annex A. PE1 does not apply this procedure on a transition from the PW receive defect state to the PW transmit defect state. b. PE1 MUST clear the reverse defect indication to PE2 if applicable. 10.3.2. PW transmit defect state entry/exit On entry to the PW transmit defect state: a. PE1 MUST set the Active bit = 0 for the corresponding FR AC in a full status report, and optionally in an asynchronous status message, as per Q.933 annex A. b. If the PW failure was detected by PE1 without receiving a reverse defect indication from PE2, PE1 MUST assume PE2 has no knowledge of the defect and MUST notify PE2 in the form of a forward defect indication. On exit from the PW transmit defect state: a. PE1 MUST set the Active bit = 1 for the corresponding FR AC in a full status report, and optionally in an Nadeau, et al. Expires October 15, 2009 [Page 25] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 asynchronous status message, as per Q.933 annex A. PE1 does not apply this procedure on a transition from the PW transmit defect state to the PW receive defect state. b. PE1 MUST clear the forward defect indication to PE2 if applicable. 10.3.3. PW defect state in the FR Port Mode PW service In case of port mode PW service, STATUS ENQUIRY and STATUS messages are transported transparently over the PW. A PW Failure will therefore result in timeouts of the Q.933 link and PVC management protocol at the Frame Relay devices at one or both sites of the emulated interface. 10.3.4. AC receive defect state entry/exit On entry to the AC receive defect state: a. PE1 MUST send a forward defect indication to PE2. On exit from the AC receive defect state: a. PE1 MUST clear the forward defect indication to PE2. 10.3.5. AC transmit defect state entry/exit The AC transmit defect state is not valid for a FR AC. 11. Procedures for TDM PW Service The following procedures apply to SAToP ([RFC4553]), CESoPSN ([RFC5086]) and TDMoIP ([RFC5087]). These technologies generally utilize the single-emulated loop mode (see section 7). Note that TDMoIP distinguishes between trail-extended and trail-terminated scenarios; the former is essentially the single emulated loop model, while the latter differs from the coupled-loop model in that failure notifications are not propagated across the PW. Since TDM is inherently real-time in nature, many OAM indications must be generated or forwarded with essentially no delay. This requirement rules out the use of messaging protocols, such as relying on the PW status message. Thus, for TDM PWs, alternate mechanism are employed. Nadeau, et al. Expires October 15, 2009 [Page 26] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 The fact that TDM PW packets are sent at a known constant rate is used as an OAM mechanism. Thus, a PE enters the PW receive defect state when a preconfigured number of TDM PW packets do not arrive in a timely fashion. It exits this state when packets once again arrive at the proper rate. Native TDM carries OAM indications in overhead fields that travel along with the data. TDM PWs emulate this behavior by sending urgent OAM messages in the PWE control word. The TDM PWE control word contains a set of flags used to indicate PW and AC defect conditions. The L bit is an AC forward defect indication used by the local PE to signal TDM network defects to the remote PE. The M field may be used to modify the meaning of receive defects. The R bit is a PW reverse defect indication used by the local PE to signal PSN failures to the remote PE. Upon reception of packets with the R-bit set, a PE enters the PW transmit defect state. 11.1. AC receive defect state entry/exit criteria PE1 enters the AC receive defect state if any of the following conditions are met: e. It detects a physical layer fault on the TDM interface (Loss of Signal, Loss of Alignment, etc (see G.705)). f. It is notified of a previous physical layer fault by detecting of AIS. The exact conditions under which a PE enters and exits the AIS state are defined in [ITU-T G.775]. Note that Loss of Signal and AIS detection can be performed for both structure-agnostic and structure- aware TDM PW types. Note that structure-agnostic PEs can not detect Loss of Alignment. 11.2. AC transmit defect state entry/exit criteria PE1 enters the AC transmit defect state when it detects RDI according to the criteria in [ITU-T G.775]. Note that structure-agnostic PEs can not detect RDI. Nadeau, et al. Expires October 15, 2009 [Page 27] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 11.3. Consequent Actions 11.3.1. PW receive defect state entry/exit On entry to the PW receive defect state: a. PE1 MUST commence AIS insertion into the corresponding TDM AC. b. PE1 MUST set the R bit in all PW packets sent back to PE2. On exit from the PW receive defect state: c. PE1 MUST cease AIS insertion into the corresponding TDM AC. d. PE1 MUST clear the R bit in all PW packets sent back to PE2. Note that AIS generation can in general be performed by both structure-aware and structure-agnostic PEs. 11.3.2. PW transmit defect state entry/exit On entry to the PW Transmit Defect State: a. A structure-aware PE1 MUST commence RDI insertion into the corresponding AC. On exit from the PW Transmit Defect State: b. A structure-aware PE1 MUST cease RDI insertion into the corresponding AC. Note that structure-agnostic PEs are not capable of injecting RDI into an AC. 11.3.3. AC receive defect state entry/exit On entry to the AC receive defect state and when operating in the "single emulated OAM loop" mode: a. PE1 SHOULD overwrite the TDM data with AIS in the PW packets sent towards PE2. b. PE1 MUST set the L bit in these packets. Nadeau, et al. Expires October 15, 2009 [Page 28] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 c. PE1 MAY omit the payload in order to conserve bandwidth. d. A structure-aware PE1 SHOULD send RDI back towards CE1. e. A structure-aware PE1 that detects a potentially correctable AC defect MAY use the M field to indicate this. On exit from the AC receive defect state and when operating in the "single emulated OAM loop" mode: a. PE1 MUST cease overwriting PW content with AIS and return to forwarding valid TDM data in PW packets sent towards PE2. b. PE1 MUST clear the notification bit in PW packets sent towards PE2. c. A structure-aware PE1 MUST cease sending RDI towards CE1. 12. Procedures for CEP PW Service The following procedures apply to SONET/SDH Circuit Emulation ([RFC4842]). They are based on the single-emulated loop mode (see section 7). Since SONET and SDH are inherently real-time in nature, many OAM indications must be generated or forwarded with essentially no delay. This requirement rules out the use of messaging protocols, such as relying on the PW status message. Thus, for CEP PWs alternate mechanism are employed. The CEP PWE control word contains a set of flags used to indicate PW and AC defect conditions. The L bit is a forward defect indication used by the local PE to signal a defect in the attachment circuit to the remote PE. The R bit is a PW reverse defect indication used by the local PE to signal PSN failures to the remote PE. The combination of N and P bit is used by the local PE to signal loss of pointer to the remote PE. Nadeau, et al. Expires October 15, 2009 [Page 29] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 The fact that CEP PW packets are sent at a known constant rate is used as an OAM mechanism. Thus, a PE enters the PW receive defect state it loses packet synchronization. It exits this state when it regains packet synchronization. See [RFC4842] for further details. 12.1. Defect states 12.1.1. PW receive defect state entry/exit criteria In addition to the conditions specified in section 8.2.1. PE1 will enter the PW receive defect state if one of the following is true: - it receives packets with the L bit set - it receives packets with both the N and P bits set - it loses packet synchronization 12.1.2. PW transmit defect state entry/exit criteria In addition to the conditions specified in section 8.2.2. PE1 will enter the PW transmit defect state if it receives packets with the R bit set. 12.1.3. AC receive defect state entry/exit criteria PE1 enters the AC receive defect state if any of the following conditions are met: a. It detects a physical layer fault on the TDM interface (Loss of Signal, Loss of Alignment, etc (see [appropriate SONET & SDH reference])). b. It is notified of a previous physical layer fault by detecting of AIS. The exact conditions under which a PE enters and exits the AIS state are defined in[ITU-T G.707] and [ITU-T G.806]. 12.1.4. AC transmit defect state entry/exit criteria The AC transmit defect state is not valid for CEP PWs. RDI signals are forwarded transparently. Nadeau, et al. Expires October 15, 2009 [Page 30] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 12.2. Consequent actions 12.2.1. PW receive defect state entry/exit On entry to the PW receive defect state: a. PE1 MUST commence AIS-P/V insertion into the corresponding AC. b. PE1 MUST set the R bit in all PW packets sent back to PE2. On exit from the PW receive defect state: a. PE1 MUST cease AIS-P/V insertion into the corresponding AC. b. PE1 MUST clear the R bit in all PW packets sent back to PE2. See [RFC4842] for further details. 12.2.2. PW transmit defect state entry/exit On entry to the PW Transmit Defect State: a. A structure-aware PE1 MUST commence RDI insertion into the corresponding AC. On exit from the PW Transmit Defect State: a. A structure-aware PE1 MUST cease RDI insertion into the corresponding AC. 12.2.3. AC receive defect state entry/exit On entry to the AC receive defect state: a. PE1 MUST set the L bit in these packets. b. If Dynamic Bandwidth Allocation (DBA) has been enabled, PE1 MAY omit the payload in order to conserve bandwidth. c. If Dynamic Bandwidth Allocation (DBA) is not enabled PE1 SHOULD insert AIS-V/P in the SDH/SONET client layer in the PW packets sent towards PE2. Nadeau, et al. Expires October 15, 2009 [Page 31] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 On exit from the AC receive defect state and when operating in the "single emulated OAM loop" mode: d. PE1 MUST cease overwriting PW content with AIS-P/V and return to forwarding valid data in PW packets sent towards PE2. e. PE1 MUST clear the L bit in PW packets sent towards PE2. See [RFC4842] for further details. 13. Security Considerations The mapping messages described in this document do not change the security functions inherent in the actual messages. 14. IANA Considerations There are none at this time. 15. References 15.1. Normative References [BFD] Katz, D., Ward, D., "Bidirectional Forwarding Detection", Internet Draft , July 2005 [FRF.19] Frame Relay Forum, "Frame Relay Operations, Administration, and Maintenance Implementation Agreement", March 2001 [ICMP] Postel, J. "Internet Control Message Protocol" RFC 792 [ITU-T G.707] Recommendation G.707 "Network Node Interface For The Synchronous Digital Hierarchy", December 2003 [ITU-T G.775] Recommendation G.775 "Loss of Signal (LOS), Alarm Indication Signal(AIS) and Remote Defect Indication (RDI) defect detection and clearance criteria for PDH signals", October 1998 [ITU-T G.806] Recommendation G.806 "Characteristics of transport equipment-Description methodology and generic functionality", February 2004. [ITU-T I.610] Recommendation I.610 "B-ISDN operation and maintenance principles and functions", February 1999 Nadeau, et al. Expires October 15, 2009 [Page 32] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 [ITU-T I.620] Recommendation I.620 "Frame relay operation and maintenance principles and functions", October 1996 [ITU-T Q.933] Recommendation Q.933 "ISDN Digital Subscriber Signalling System No. 1 (DSS1) Signalling specifications for frame mode switched and permanent virtual connection control and status monitoring" February 2003 [RFC3931] Lau, J., et. al. "Layer Two Tunneling Protocol (Version 3", RFC 3931, March 2005 [RFC4023] Worster. T., et al., "Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE)", RFC 4023, March 2005 [RFC4379] Kompella, K., et. al., "Detecting MPLS Data Plane Failures", RFC4379, February 2006 [RFC4447] Martini, L., Rosen, E., Smith, T., "Pseudowire Setup and Maintenance using LDP", RFC4447, April 2006 [RFC4842] Malis, A., et. al., "SONET/SDH Circuit Emulation over Packet (CEP)", RFC 4842, April 2007 [RFC5085] Nadeau, T., et al., "Pseudo Wire Virtual Circuit Connection Verification (VCCV)", RFC 5085, December 2007 [VCCV-BFD] Nadeau, T., Pignataro, C., "Bidirectional Forwarding Detection (BFD) for the Pseudowire Virtual Circuit Connectivity Verification (VCCV)", draft-ietf-pwe3-vccv-bfd-02, June 2008 15.2. Informative References [CONGESTION] Rosen, E., Bryant, S., Davie, B., "PWE3 Congestion Control Framework", draft-ietf-pwe3-congestion-frmwk-01.txt, May 2008 [ETH-OAM-IWK] Mohan, D., et al., "MPLS and Ethernet OAM Interworking", draft-mohan-pwe3-mpls-eth-oam-iwk-01, July 2008 [L2TP-Status] McGill, N. Pignataro, C., "L2TPv3 Extended Circuit Status Values", draft-nmcgill-l2tpext-circuit-status-extensions- 01 (work in progress), June 2008. Nadeau, et al. Expires October 15, 2009 [Page 33] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 [RFC3916] Xiao, X., McPherson, D., Pate, P., "Requirements for Pseudo Wire Emulation Edge to-Edge (PWE3)", RFC 3916, September 2004 [RFC3985] Bryant, S., Pate, P., "PWE3 Architecture", RFC 3985, March 2005 [RFC4377] Nadeau, T. et.al., "OAM Requirements for MPLS Networks", RFC4377, February 2006 [RFC4446] Martini, L., et al., "IANA Allocations for pseudo Wire Edge to Edge Emulation (PWE3)", RFC4446, April 2006 [RFC4454] Singh, S., Townsley, M., and C. Pignataro, "Asynchronous Transfer Mode (ATM) over Layer 2 Tunneling Protocol Version 3 (L2TPv3)", RFC 4454, May 2006 [RFC4553] A.Vainshtein, Y.(J) Stein, "Structure-Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)", RFC 4553, June 2006 [RFC4717] Martini, L., et al., "Encapsulation Methods for Transport of ATM Cells/Frame Over IP and MPLS Networks", RFC4717, December 2006 [RFC5086] A.Vainshtein et al., "Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN)", RFC 5086, December 2007 [RFC5087] Y.(J) Stein et al., "Time Division Multiplexing over IP (TDMoIP)", RFC 5087, December 2007 16. Editor's Addresses Mustapha Aissaoui Alcatel-lucent 600 March Rd Kanata, ON, Canada K2K 2E6 Email: mustapha.aissaoui@alcatel-lucent.com Peter B. Busschbach Alcatel-Lucent 67 Whippany Road Nadeau, et al. Expires October 15, 2009 [Page 34] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 Whippany, NJ, 07981 Email: busschbach@alcatel-lucent.com David Allan Nortel Networks 3500 Carling Ave., Ottawa, Ontario, CANADA Email: dallan@nortel.com Luca Martini Cisco Systems, Inc. 9155 East Nichols Avenue, Suite 400 Englewood, CO, 80112 Email: lmartini@cisco.com Thomas D. Nadeau BT BT Centre 81 Newgate Street London EC1A 7AJ United Kingdom EMail: tom.nadeau@bt.com Monique Morrow Cisco Systems, Inc. Glatt-com CH-8301 Glattzentrum Switzerland EMail: mmorrow@cisco.com Yaakov (Jonathan) Stein RAD Data Communications 24 Raoul Wallenberg St., Bldg C Tel Aviv 69719 ISRAEL EMail: yaakov_s@rad.com Informative Appendix A: Native Service Management - Frame Relay Management The management of Frame Relay Bearer Service (FRBS) connections can be accomplished through two distinct methodologies: Nadeau, et al. Expires October 15, 2009 [Page 35] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 a. Based on ITU-T Q.933 Annex A, Link Integrity Verification procedure, where STATUS and STATUS ENQUIRY signaling messages are sent using DLCI=0 over a given UNI and NNI physical link. [ITU-T Q.933] b. Based on FRBS LMI, and similar to ATM ILMI where LMI is common in private Frame Relay networks. In addition, ITU-T I.620 addresses Frame Relay loopback, but the deployment of this standard is relatively limited [ITU-T I.620]. It is possible to use either, or both, of the above options to manage Frame Relay interfaces. This document will refer exclusively to Q.933 messages. The status of any provisioned Frame Relay PVC may be updated through: a. STATUS messages in response to STATUS ENQUIRY messages, these are mandatory. b. Optional unsolicited STATUS updates independent of STATUS ENQUIRY (typically under the control of management system, these updates can be sent periodically (continuous monitoring) or only upon detection of specific defects based on configuration. In Frame Relay, a DLC is either up or down. There is no distinction between different directions. To achieve commonality with other technologies, down is represented as a receive defect. Frame relay connection management is not implemented over the PW using either of the techniques native to FR, therefore PW mechanisms are used to synchronize the view each PE has of the remote NS/AC. A PE will treat a remote NS/AC failure in the same way it would treat a PW or PSN failure; that is using AC facing FR connection management to notify the CE that FR is down. - ATM Management ATM management and OAM mechanisms are much more evolved than those of Frame Relay. There are five broad management-related categories, including fault management (FT), Performance management (PM), configuration management (CM), Accounting management (AC), and Security management (SM). ITU-T Recommendation I.610 describes the functions for the operation and maintenance of the physical layer Nadeau, et al. Expires October 15, 2009 [Page 36] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 and the ATM layer, that is, management at the bit and cell levels [ITU-T I.610]. Because of its scope, this document will concentrate on ATM fault management functions. Fault management functions include the following: a. Alarm indication signal (AIS) b. Remote Defect indication (RDI). c. Continuity Check (CC). d. Loopback (LB) Some of the basic ATM fault management functions are described as follows: Alarm indication signal (AIS) sends a message in the same direction as that of the signal, to the effect that an error has been detected. Remote defect indication (RDI) sends a message to the transmitting terminal that an error has been detected. RDI is also referred to as the far-end reporting failure. Alarms related to the physical layer are indicated using path AIS/RDI. Virtual path AIS/RDI and virtual channel AIS/RDI are also generated for the ATM layer. OAM cells (F4 and F5 cells) are used to instrument virtual paths and virtual channels respectively with regard to their performance and availability. OAM cells in the F4 and F5 flows are used for monitoring a segment of the network and end-to-end monitoring. OAM cells in F4 flows have the same VPI as that of the connection being monitored. OAM cells in F5 flows have the same VPI and VCI as that of the connection being monitored. The AIS and RDI messages of the F4 and F5 flows are sent to the other network nodes via the VPC or the VCC to which the message refers. The type of error and its location can be indicated in the OAM cells. Continuity check is another fault management function. To check whether a VCC that has been idle for a period of time is still functioning, the network elements can send continuity-check cells along that VCC. Informative Appendix B: PW Defects and Detection tools - PW Defects Possible defects that impact PWs are the following: a. Physical layer defect in the PSN interface b. PSN tunnel failure which results in a loss of connectivity between ingress and egress PE. Nadeau, et al. Expires October 15, 2009 [Page 37] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 c. Control session failures between ingress and egress PE In case of an MPLS PSN and an MPLS-IP PSN there are additional defects: a. PW labeling error, which is due to a defect in the ingress PE, or to an over-writing of the PW label value somewhere along the LSP path. b. LSP tunnel Label swapping errors or LSP tunnel label merging errors in the MPLS network. This could result in the termination of a PW at the wrong egress PE. c. Unintended self-replication; e.g., due to loops or denial- of-service attacks. - Packet Loss Persistent congestion in the PSN or in a PE could impact the proper operation of the emulated service. A PE can detect packet loss resulting from congestion through several methods. If a PE uses the sequence number field in the PWE3 Control Word for a specific Pseudo Wire [RFC3985], it has the ability to detect packet loss. Translation of congestion detection to PW defect states is outside the scope of this specification. Generally, there are congestion alarms which are raised in the node and to the management system when congestion occurs. The decision to declare the PW Down and to select another path is usually at the discretion of the network operator. - PW Defect Detection Tools To detect the defects listed above, Service Providers have a variety of options available. Physical Layer defect detection and notification mechanisms such as SONET/SDH LOS, LOF, and AIS/FERF. PSN Defect Detection Mechanisms: For PWE3 over an L2TP-IP PSN, with L2TP as encapsulation protocol, the defect detection mechanisms described in [RFC3931] apply. This includes for example the keep-alive mechanism performed with Hello messages for detection of loss of connectivity between a pair of LCCEs (i.e., dead PE peer and path detection). Furthermore, the Nadeau, et al. Expires October 15, 2009 [Page 38] Internet-Draft Pseudo Wire (PW) OAM Message Mapping April 2009 tools Ping and Traceroute, based on ICMP Echo Messages apply [RFC792] and can be used to detect defects on the IP PSN. Additionally, ICMP Ping [RFC5085] and BFD [VCCV-BFD] can also be used with VCCV to detect defects at the individual pseudowire level. For PWE3 over an MPLS PSN and an MPLS-IP PSN, several tools can be used. a. LSP-Ping and LSP-Traceroute( [RFC4379]) for LSP tunnel connectivity verification. b. LSP-Ping with Bi-directional Forwarding Detection ([BFD]) for LSP tunnel continuity checking. c. Furthermore, if RSVP-TE is used to setup the PSN Tunnels between ingress and egress PE, the hello protocol can be used to detect loss of connectivity [RFC3209], but only at the control plane. PW specific defect detection mechanisms: [RFC4377] describes how LSP-Ping and BFD can be used over individual PWs for connectivity verification and continuity checking respectively. When used as such, we will refer to them as VCCV-Ping and VCCV-BFD respectively. Furthermore, the detection of a fault could occur at different points in the network and there are several ways the observing PE determines a fault exists: a. egress PE detection of failure (e.g. BFD) b. ingress PE detection of failure (e.g. LSP-PING) c. ingress PE notification of failure (e.g. RSVP Path-err) Nadeau, et al. Expires October 15, 2009 [Page 39]