PWE3 Working Group Thomas D. Nadeau, Ed.
Internet Draft BT
Expires: January 2009 Monique Morrow, Ed.
Luca Martini, Ed.
Dinesh Mohan, Ed. Carlos Pignataro, Ed.
Nortel Cisco
July 2008
Pseudo Wire (PW) OAM Message Mapping
draft-ietf-pwe3-oam-msg-map-07.txt
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Abstract
This document specifies the mapping 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 such that
a homogenous PW service can be constructed.
Nadeau, et al. Standards Track [Page 1]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 Table of Contents 1 Specification of Requirements ........................ 4 2 Acknowledgments ...................................... 4 3 Contributing Authors ................................. 4 4 Introduction ......................................... 4 5 Terminology .......................................... 5 6 Reference Model and Defect Locations ................. 6 7 Abstract Defect States ............................... 8 8 PW Status and Defects ................................ 9 8.1 PW Defects ........................................... 9 8.1.1 Packet Loss .......................................... 10 8.2 Defect Detection and Notification .................... 10 8.2.1 Defect Detection Tools ............................... 10 8.2.2 Defect ............................................... 11 8.3 Overview of fault notifications ...................... 12 8.3.1 Use of Native Service notifications .................. 13 8.3.2 Use of Ethernet Native Service notifications ......... 14 8.3.3 The Use of PW Status for MPLS and MPLS-IP PSNs ....... 15 8.3.4 The Use of the L2TP Circuit Status AVP ............... 16 8.3.5 The Use of BFD Diagnostic Codes ...................... 18 9 PW Defect State Entry/Exit ........................... 19 9.1 PW Forward Defect Entry/Exit ......................... 19 9.2 PW reverse defect state entry/exit ................... 20 9.2.1 PW reverse defects with PE state synchronization ..... 20 10 AC Defect States ..................................... 20 10.1 Ethernet AC .......................................... 20 10.1.1 AC ................................................... 20 10.1.2 AC Reverse Defect State Entry or Exit ................ 21 10.2 FR ACs ............................................... 22 10.3 ATM ACs .............................................. 22 10.3.1 AC Forward Defect State Entry/Exit ................... 22 10.3.2 AC Reverse Defect State Entry/Exit ................... 23 11 PW Forward Defect Entry/Exit procedures .............. 23 11.1 Procedures in FR Port Mode ........................... 23 11.2 Procedures in ATM Port Mode .......................... 23 11.3 PW Forward Defect Entry Procedures ................... 24 11.3.1 Ethernet AC Procedures ............................... 24 11.3.2 FR AC procedures ..................................... 25 11.3.3 ATM AC procedures .................................... 25 11.3.4 Additional procedures for a FR PW, and an ATM PW ..... 25 11.4 PW Forward Defect Exit Procedures .................... 26 11.4.1 Ethernet AC Procedures ............................... 26 11.4.2 FR AC procedures ..................................... 27 11.4.3 ATM AC procedures .................................... 27 11.4.4 Additional procedures for a FR PW, and a ATM PW ..... 27 Nadeau, et al. Standards Track [Page 2]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 11.5 PW Reverse Defect Entry Procedures ................... 28 11.5.1 Ethernet AC Procedures ............................... 28 11.5.2 FR AC procedures ..................................... 28 11.5.3 ATM AC procedures .................................... 28 11.6 PW Reverse Defect Exit Procedures .................... 29 11.6.1 Ethernet AC Procedures ............................... 29 11.6.2 FR AC procedures ..................................... 29 11.6.3 ATM AC procedures .................................... 29 12 AC Defect Entry/Exit Procedures ...................... 29 12.1 AC Forward Defect Entry .............................. 29 12.1.1 Procedures for an Ethernet PW ........................ 30 12.1.2 Procedures for a FR/ATM PW in the out-of-band method . 30 12.1.3 Procedures for a ATM PW in the inband PW Method ...... 31 12.1.4 Additional procedures for ATM ACs .................... 31 12.2 AC Reverse defect entry .............................. 31 12.2.1 Ethernet AC Procedures ............................... 31 12.2.2 Procedures for a FR/ATM PW in the out-of-band method . 31 12.2.3 Procedures for a ATM PW in the inband PW Method ...... 32 12.3 AC Forward Defect Exit ............................... 32 12.3.1 Ethernet AC Procedures ............................... 32 12.3.2 Procedures for a FR/ATM PW in the out-of-band method . 32 12.3.3 Procedures for a ATM PW in the inband PW Method ...... 33 12.3.4 Additional procedures for ATM ACs .................... 33 12.4 AC Reverse Defect Exit ............................... 33 12.4.1 Ethernet AC Procedures ............................... 33 12.4.2 Procedures for a FR/ATM PW in the out-of-band method . 34 12.4.3 Procedures for a ATM PW in the inband PW method ...... 34 13 SONET Encapsulation (CEP) ............................ 34 14 TDM Encapsulation .................................... 34 Ap A Native Service Management ............................ 36 Ap A.1 Frame Relay Management ............................... 36 Ap A.2 ATM Management ....................................... 36 Ap A.3 Ethernet Management .................................. 37 15 Security Considerations .............................. 39 16 IANA Considerations .................................. 39 17 References ........................................... 39 17.1 Normative References ................................. 39 17.2 Informative References ............................... 40 18 Editors' Addresses ................................... 41 19 Intellectual Property Statement ...................... 42 20 Full Copyright Statement ............................. 42 21 Acknowledgment ....................................... 43 Nadeau, et al. Standards Track [Page 3]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 1. Specification of Requirements 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. 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. 3. Contributing Authors The following persons contributed to this document: Peter B. Busschbach (busschbach@alcatel-lucent.com), Mustapha Aissaoui (mustapha.aissaoui@alcatel-lucent.com), Matthew Bocci (matthew.bocci@alcatel.co.uk),David Watkinson (david.watkinson@alcatel-lucent.com), Yuichi Ikejiri (y.ikejiri@ntt.com), Kenji Kumaki(kekumaki@kddi.com), Satoru Matsushima (satoru.matsushima@tm.softbank.co.jp),David Allan (dallan@nortelnetworks.com), Simon Delord (sdelord@uecomm.com.au), Vasile Radoaca (vasile.radoaca@alcatel-lucent.com) 4. Introduction This document specifies the mapping 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 homogeneous PW service can be constructed. This document is motivated by the requirements put forth in [RFC4377] and [RFC3916]. Ideally only PW and AC defects need be propagated into the Native Service (NS), and NS OAM mechanisms are transported transparently over the PW. Some homogeneous scenarios use PW specific OAM mechanisms to synchronize defect state between PEs due to discontinuities in native service OAM between the AC and the PW (e.g. FR LMI). The objective of this document 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 Nadeau, et al. Standards Track [Page 4]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 undertaken by PEs in response to specific failure conditions. This document covers PWE over MPLS PSN, PWE over IP PSN and PWE over L2TP PSN. 5. Terminology AIS Alarm Indication Signal AC Attachment circuit BDI Backward Defect Indication CC Continuity Check CE Customer Edge CPCS Common Part Convergence Sublayer DLC Data Link Connection FDI Forward Defect Indication FRBS Frame Relay Bearer Service IWF Interworking Function LB Loopback MD Level Maintenance Domain (MD) Level which identifies a value in the range of 0-7 associated with Ethernet OAM frame. MD Level identifies the span of the Ethernet OAM frame. MEP Maintenance End Point is responsible for origination and termination of OAM frames for a given MEG MEG Maintenance Entity Group MIP Maintenance Intermediate Point is located between peer MEPs and can process OAM frames but does not initiate or terminate them NE Network Element NS Native Service 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 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 Nadeau, et al. Standards Track [Page 5]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 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 and the attachment circuit associated with the far end PW termination is the remote AC. 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 and what the PE may explicitly know about information transfer capabilities of the PW service. A forward defect is one that impacts information transfer to the observing PE. It impacts the observing PEs ability to receive information. A forward defect MAY also imply impact on information sent or relayed by the observer (and as it cannot receive is therefore unknowable) and so the forward defect state is considered to be a superset of the two defect states. A reverse defect is one that uniquely impacts information sent or relayed by observer. 6. 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. Nadeau, et al. Standards Track [Page 6]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 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 In all interworking scenarios described in this document, it is assumed that at PE1 the AC and the PW are of the same type. The procedures described in this document exclusively apply to PE1. PE2 for a homogeneous service implements the identical functionality (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: -i. Defect in the first L2 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 L2 network (N2) using the native service specific OAM defect indication. -ii. Defect on a PE1 AC interface. -iii. Defect on a PE PSN interface. -iv. Defect in the PSN network. This covers any defect in the PSN which impacts all or a subset of the PSN tunnels and 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 control plane, i.e., signaling and routing, messages do not necessarily follow the path of the user plane messages. Defect in the control plane are detected and conveyed separately through control plane mechanisms. However, in some cases, they have an impact on the status of the PW as explained in the next section. -v. Defect in the second L2 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 L2 network (N1) using the native service OAM defect indication. Nadeau, et al. Standards Track [Page 7]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 -vi. Defect on a PE2 AC interface (which is also considered a remote AC defect in the context of this draft). 7. Abstract Defect States PE1 is obliged to track four abstract defect states that reflect the observed state of both directions of the PW service on both the AC and the PW sides. Faults may impact only one or both directions of the PW. The observed state is a combination of faults directly detected by PE1, or faults it has been made aware of via notifications. +-----+ ----AC forward---->| |-----PW reverse----> CE1 | PE1 | PE2/CE2 <---AC reverse-----| |<----PW forward----- +-----+ (arrows indicate direction of user traffic impacted by a defect) Figure 2: Forward and Reverse Defect States and Notifications PE1 will directly detect or be notified of AC forward and PW forward defects as they occur upstream of PE1 and impact traffic being sent to PE1. In Figure 2, PE1 may be notified of a forward defect in the AC by receiving a Forward Defect indication, e.g., ATM AIS, from CE1. This defect impacts the ability of PE1 to receive user traffic from CE1 on the AC. PE1 can also directly detect this 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 forward defect in the PW by receiving a Forward Defect indication from PE2. This notification can either be a Local PSN- facing PW (egress) Transmit Fault or a Local Attachment Circuit (ingress) Receive Fault. This defect impacts the ability of PE1 to receive user traffic from CE2. Note that the AC or PW Forward Defect notification is sent in the same direction as the user traffic impacted by the defect. PE1 will only be notified of AC reverse and PW reverse defects as they universally will be detected by other devices and only impact traffic that has already been relayed by PE1. In Figure 2, PE1 may be notified of a reverse defect in the AC by receiving a Reverse Defect indication, e.g., ATM RDI, from CE1. This defect impacts the ability of PE1 to send user traffic to CE1 on the AC. Similarly, PE1 may be notified of a reverse defect in the PW by receiving a Reverse Defect indication from PE2. This notification can either be a Local PSN- facing PW (ingress) Receive Fault or a Local Attachment Circuit Nadeau, et al. Standards Track [Page 8]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 (egress) Transmit Fault. This defect impacts the ability of PE1 to send user traffic to CE2. Note that the AC or PW Reverse Defect notification 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 potential ACs and PWs within the document scope and the consequent actions that PE1 must perform to properly interwork those notifications. The abstract defect states used by PE1 are common to all potential interworking combinations of PWs and ACs. When a PE has multiple sources of notifications from a peer (e.g. PSN control plane, LDP control plane, BFD), it is obliged to track all sources, but with respect to consequent actions the forward state ALWAYS has precedence over the reverse state. 8. PW Status and Defects This section describes possible PW defects, ways to detect them and consequent actions. 8.1. PW Defects Possible defects that impact PWs are the following: - Physical layer defect in the PSN interface - PSN tunnel failure which results in a loss of connectivity between ingress and egress PE. - Control session failures between ingress and egress PE In case of an MPLS PSN and an MPLS-IP PSN there are additional defects: - 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. - 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. Nadeau, et al. Standards Track [Page 9]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 - Unintended self-replication; e.g., due to loops or denial-of- service attacks. 8.1.1. 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 ato 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. 8.2. Defect Detection and Notification 8.2.1. 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 keepalive mechanism performed with Hello messages for detection of loss of connectiviry between a pair of LCCEs (i.e., dead PE peer and path detection). Furthermore, the 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. Nadeau, et al. Standards Track [Page 10]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 - LSP-Ping and LSP-Traceroute( [RFC4379]) for LSP tunnel connectivity verification. - LSP-Ping with Bi-directional Forwarding Detection ([BFD]) for LSP tunnel continuity checking. - 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: -i. egress PE detection of failure (e.g. BFD) -ii. ingress PE detection of failure (e.g. LSP-PING) -iii. ingress PE notification of failure (e.g. RSVP Path-err) 8.2.2. Defect The discussion below is intended to give some perspective how tools mentioned in the previous section can be used to detect failures. Observations: - Tools like LSP-Ping and BFD can be run periodically or on demand. If used for defect detection, as opposed to diagnostic usage, they must be run periodically. Control protocol failure indications, e.g. detected through L2TP Keepalive (Hello) messages or the RSVP-TE Hello messages, can be used to detect many network failures. However, control protocol failures do not necessarily coincide with data plane failures. Therefore, a defect detection mechanism in the data plane is required to protect against all potential data plane failures. Furthermore, fault diagnosis mechanisms for data plane failures are required to further analyze detected failures. - For PWE3 over an MPLS PSN and an MPLS-IP PSN, it is effective to run a defect detection mechanism over a PSN Tunnel frequently and run one over every individual PW within that PSN Tunnel less frequently. However in case the PSN traffic is distributed over Nadeau, et al. Standards Track [Page 11]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 Equal Cost Multi Paths (ECMP), it may be difficult to guarantee that PSN OAM messages follow the same path as a specific PW. A Service Provider might therefore decide to focus on defect detection over PWs. - In MPLS networks, execution of LSP Ping would detect MPLS label errors, since it requests the receiving node to match the label with the original FEC that was used in the LSP set up. BFD can also be used since it relies on discriminators. A label error would result in a mismatch between the expected discriminator and the actual discriminator in the BFD control messages. - For PWE3 over an MPLS PSN and an MPLS-IP PSN, PEs could detect PSN label errors through the execution of LSP-Ping. However, use of VCCV is preferred as it is a more accurate detection tool for pseudowires. Furthermore, it can be run using a BFD mode, i.e., VCCV-BFD, which allows it to be used as a light-weight detection mechanism for PWs. If, due to a label error in the PSN, a PW would be terminated on the wrong egress PE, PEs would detect this through the execution of VCCV. LSP ping and/or LSP trace could then be used to diagnose the detected failure. Based on these observations, it is clear that a service provider has the disposal of a variety of tools. There are many factors that influence which combination of tools best meets its needs. 8.3. Overview of fault notifications For a MPLS PSN and a IP PSN using MPLS-in-IP [RFC4023], a PW that are established and maintained using LDP SHOULD use LDP status signaling messages as the default mechanism for AC, PW status and defect notification [RFC4447]. If a combination of VCCV+BFD [RFC4377] status then LDP status MUST not be used, as outlined in [VCCV-BFD] section 3. For PWs established using other means such as static configuration, in-band signaling using VCCV-BFD [RFC5085] SHOULD be used to convey AC and PW status. For a IP PSN using L2TPv3, i.e., a L2TP-IP PSN, StopCCN is used to shutdown the control connection (and implicitly all sessions associated with that control connection without any explicit session control messages) and CDN messages are used to disconnect a specific pseudowire session. In its most basic form, the Circuit Status AVP [RFC3931] in a Set-Link-Info (SLI) message can signal active/inactive AC status. As described in [L2TP-Status], a Circuit Status AVP in an SLI message can also be used to convey status and defects in the AC and the PSN- facing PW in both ingress and egress directions (i.e., four Nadeau, et al. Standards Track [Page 12]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 independent status bits), as well as providing "standby" indication, without the need to tear down the sessions or control connection. Additionally, BFD [VCCV-BFD] can be used to signal status for L2TP-IP PWs, but the L2TPv3 status conveyed through the Circuit Status AVP MUST take precedence over the VCCV-BFD status (see Section 5.3.4 and Section 3.3 of [VCCV-BFD]). 8.3.1. Use of Native Service notifications In the context of this document, ATM and unstructured SONET/TDM PWs are the only examples of a PW that has native service notification capability. Frame relay does have the FR OAM specification [FRF.19], but this is not commonly deployed. All other PWs use PW specific notification mechanisms. ATM PWs may optionally also use PW specific notification mechanisms. In normal, i.e., defect-free, operation, all the types of ATM OAM cells described in Section 12.2 are either terminated at the PE, for OAM segments terminating in the AC endpoint, or transparently carried over the PSN tunnel [RFC4717] [RFC4454]. This is referred to as in- band ATM OAM over PW and is the default method. An optional out-of band method based on relaying the ATM defect state over a PW specific defect indication mechanism is provided for PEs which cannot generate and/or transmit ATM OAM cells over the ATM PW. This is referred to as Out-of-band ATM OAM over PW. Ethernet Link OAM [802.3] allows some Link defect states to be detected and communicated across an Ethernet Link. When an Ethernet AC is an Ethernet PHY, there may be some application of Ethernet Link OAM [802.3]. Further, E-LMI [MEF.16] also allows for some EVC defect states to be communicated across an Ethernet UNI where Ethernet UNI constitutes a single hop Ethernet Link (i.e. without any 802.1Q/.1ad compliant bridges in between). There may be some application of E-LMI [MEF.16] for failure notification across single hop Ethernet AC in certain deployments that specifically do not support [802.1ag] and/or [Y.1731]. [Y.1731] and [802.1ag] based mechanisms are applicable in all types of Ethernet ACs. Ethernet Link OAM [802.3] and E-LMI [MEF.16] are optional and their applicability is called out, where applicable. Native Service (NS) OAM may be transported transparently over the corresponding PW as user data. For Ethernet, as an example, 802.1ag continuity check messages (CCMs) between two Maintenance End Points (MEPs) can be transported transparently as user data over the corresponding PW. At MEP locations, service failure is detected when Nadeau, et al. Standards Track [Page 13]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 a number of consecutive CCMs are missed. MEP locations can be the PE, the CE or both with different Maintenance Domain Levels. However, when interworking two networking domains, such as native Ethernet and PWs to provide an end-to-end emulated service, there is need to identify the failure domain and location even when a PE supports both the NS OAM mechanisms and the PW OAM mechanisms. In addition, scalability constraints may not allow running proactive monitoring, such as CCMs with transmission on, at a PE to detect the failure of an Ethernet Virtual circuit (EVC) across the PW domain. Thus, network driven alarms generated upon failure detection in the NS or PW domain and their mappings to the other domain are needed. There are also cases where a PE may not be able to process NS OAM messages received on the PW even when such messages are defined, as in Ethernet case, necessitating the need for fault notification message mapping between the PW domain and the Client domain. 8.3.2. Use of Ethernet Native Service notifications There is no NS fault notification capability currently specified for Ethernet PWs. However, with the completion of Ethernet OAM work, this capability should be added. This includes the ability to create a MEP associated with the Ethernet PW on the PE. The native service notification options include: - AIS Frames sent by the local MEP to the MEP on the remote PE when the MEP needs to convey PE forward defects, and when CCM transmission is configured not to be turned ON. - Suspension of CCM frames transmission from the MEP to the peer MEP on the other PE to convey PE forward defects, when CCM transmission is configured to be turned ON. - RDI in transmitted CCM frames, when loss of CCMs from the peer MEP is detected or PE needs to convey PW reverse defects. These NS OAM notifications are inserted into the corresponding PW. Similarly, when the defect conditions are cleared, a PE can take one of the following actions, depending on the mechanism that was used for failure notification, to clear the defect sate on the peer PE: - Stop AIS Frame transmission from the local MEP to the MEP on the remote PE to clear PW forward defects; - Resuming CCM frames transmission from the MEP to the peer MEP to clear PW forward defects notification, when CCM transmission is configured to be turned ON. Nadeau, et al. Standards Track [Page 14]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 - Clearing RDI indication in transmitted CCM frames, to clear PW reverse defects notification. 8.3.3. The Use of PW Status for MPLS and MPLS-IP PSNs [RFC4446] defines the following valid PW status code points. [RFC4447] specifies that Pseudo Wire forwarding is used to clear all faults and that Pseudo Wire Not Forwarding is used to convey any other defects that cannot be represented by the other code points. The remaining code points map to the forward defect and reverse defect defined in this document as follows: Forward defect - corresponds to the logical OR of Local Attachment Circuit (ingress) Receive Fault and Local PSN-facing PW (egress) Transmit Fault Reverse defect - corresponds to the logical OR of Local Attachment Circuit (egress) Transmit Fault and Local PSN-facing PW (ingress) Receive Fault PW status is used to convey the defect view of the PW local to the originating PE. This is the local PW state. This state is conveyed in the form of a forward defect or a reverse defect. Thus PW status (when available) shall be used to report the following failures: - Failures detected through defect detection mechanisms in the MPLS and MPLS-IP PSN - Failures detected through VCCV-Ping - Failures within the PE that result in an inability to forward traffic between ACs and PW - State of the AC when the PE does not have native service OAM capability or emulation of native service OAM capability is prohibitive. This state is conveyed in the form of a forward defect or a reverse defect. Note that there are a couple of 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 Nadeau, et al. Standards Track [Page 15]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 re-established. 8.3.4. The Use of the 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 AVP defined for LDP. Consequently, for L2TP-IP, the Circuit Status AVP 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], CDN messages can be used to clear L2TPv3 sessions in the presence of session-level failures detected in the L2TP-IP PSN. L2TPv3 pseudowires also support the use of BFD over VCCV to convey status information. If used, AC and PW status and defect notification using the Circuit Status AVP take precedence over VCCV-BFD status (see Section 3.3 of [VCCV-BFD]). For L2TP-IP PWs that do not use L2TPv3 signaling or are set up statically, VCCV-BFD should be used to convey AC and PW status. The Active bit set in the Circuit Status is used to clear all faults, and the Active bit clear in the Circuit Status is used to convey any defect that cannot be represented explicitly with specific Circuit Status flags from [RFC3931] or [L2TP-Status]. The forward and reverse defect definitions are mapped from [L2TP-Status] as follows: Forward defect - corresponds to the logical OR of Local Attachment Circuit (ingress) Receive Fault and Local PSN-facing PW (egress) Transmit Fault Reverse defect - corresponds to the logical OR of Local Attachment Circuit (egress) Transmit Fault and Local PSN-facing PW (ingress) Receive Fault The status notification represents the local view of the originating LCCE (PE). The Circuit Status is used to report the following failures when using the extended definition of [L2TP-Status]: Nadeau, et al. Standards Track [Page 16]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 - Failures detected through defect detection mechanisms in the L2TP-IP PSN. - Failures detected though VCCV (pseudowire level) - Failures within the PE that result in an inability to forward traffic between ACs and PW - State of the AC when the PE does not have native service OAM capability or emulation of native service OAM capability is prohibitive. This state is conveyed in the form of a forward defect or a reverse defect. When the extended Circuit Status definition of [L2TP-Status] is not used, the A-bit in the Circuit Status AVP in SLI is used to report: - Failures of the ACs When the extended Circuit Status definition of [L2TP-Status] is not used, the CDN and StopCCN messages are used 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, the ATM Alarm Status AVP [RFC4454] is used 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 keepalive facility. It is important to note that if a PSN failure is such that the loss of conectivity is detected when it triggers a keepalive timeouts, the control connection is cleared. L2TP Hello messages are sent in-band with the dataplane, with respect to the source and destination addresses, IP protocol number and UDP port (when UDP is used). Nadeau, et al. Standards Track [Page 17]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 8.3.5. The Use of BFD Diagnostic Codes [BFD] defines a set of diagnostic codes that partially overlap with failures that can be communicated through PW Status messages or L2TP Circuit Status AVP. This section describes the behavior of the PE 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. See [RFC5085] and [VCCV-BFD]. 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, see Section 3.3 of [VCCV-BFD]. In this mode, only two of the diagnostic (Diag) codes specified in [BFD] will be used, they are: 0 - No diagnostic: 1 - Control detection time expired 7 - Administratively Down The first code indicates that the peer PE is correctly receiving BFD control messages. The second code indicates that the peer 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 defects and PE internal failures that prevent it from forwarding traffic - must be communicated through PW Status messages, in the case of MPLS PSN or MPLS-IP PSN, or the appropriate L2TP codes in the Circuit Status AVP in the case of L2TP-IP PSN, as defined in 5.3.2 and 5.3.3. A CV type of 0x08 or 0x20 in the OAM capabilities TLV indicates that BFD is used for both PW fault detection and AC/PW Fault Notification. In this case, all defects - including AC defects and PE internal failures - are signaled through BFD, using the following diagnistic (Diag) codes specified in [BFD]: 6 -- Concatenated Path Down 8 -- Reverse Concatenated Path Down BFD diagnostic codes 6 and 8 are used to signal AC forward and Nadeau, et al. Standards Track [Page 18]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 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. 9. PW Defect State Entry/Exit 9.1. PW Forward Defect Entry/Exit A PE will enter the PW forward defect state if one of the following occurs: - It detects loss of connectivity on the PSN tunnel over which the PW is riding. This includes label swapping errors and label merging errors. - It receives a message from PE2 indicating PW forward defect or PW not forwarding, which indicates PE2 detected or was notified of a PW fault downstream of it or that there was a remote AC fault. - It detects a loss of PW connectivity, including label errors, through VCCV-BFD or VCCV-PING in no reply mode. Note that if the PW control session between the PEs fails, the PW is torn down and needs to be re-established. However, the consequent actions towards the ACs are the same as if the PW entered the forward defect state. PE1 will exit the forward defect state if the PW status received from PE2 has the forward defect indication cleared, and it has established that PW/PSN connectivity is working in the forward direction. Note that this may result in a transition to the PW operational or PW reverse defect states. For a PWE3 over a L2TP-IP PSN, a PE will exit the PW forward defect state when the following conditions are true: - All defects it had previously detected have disappeared, and - A L2TPv3 session is successfully established to carry the PW packets. Nadeau, et al. Standards Track [Page 19]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 9.2. PW reverse defect state entry/exit A PE will enter the PW reverse defect state if it receives a message from PE2 indicating PW reverse defect which indicates PE2 detected or was notified of a PW/PSN fault upstream of it or that there was a remote AC fault and it is not already in the PW forward defect state. PE1 will exit the reverse defect state if the PW status received from PE2 contains the reverse defect indication cleared, or it has entered the PW forward defect state. For a PWE3 over a L2TP-IP PSN, the PW reverse defect state is not valid and a PE can only enter the PW forward defect state. 9.2.1. PW reverse defects with PE state synchronization Some PW mechanisms will result in PW defects being detected by or notified to PE1 when PE1 is upstream of the fault but the notification did not originate with PE2. The resultant actions are identical to that of entering the PW reverse defect state with the addition that PE1 needs to synchronize state with PE2 and the PW state communicated from PE1 to PE2 needs to indicate state accordingly. When the PSN uses RSVP-TE or proactively uses LSP-PING as a PW fault detection mechanism, PE1 must enter to the PW reverse defect state. The exit criteria being when, the RSVP fault state or the LSP-PING fault state exit criteria has been met, indicating no PW reverse defects. 10. AC Defect States 10.1. Ethernet AC 10.1.1. AC PE1 enters the AC forward defect state if any of the following conditions are met: - It detects or is notified of a physical layer fault on the Ethernet interface. Ethernet link failure can be detected based on loss of signal (LoS) or via Ethernet Link OAM [802.3] critical link event notifications generated at an upstream node CE1 with "Dying Gasp" or "Critical Event" indication. Nadeau, et al. Standards Track [Page 20]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 - A MEP associated with the local AC receives an Ethernet AIS frame. - A MEP associated with the local AC does not receive CCM frames from the peer MEP in the client domain (e.g. CE1) within a configurable interval equal to a multiple (e.g. 3.5) of the CCM transmission period configured for the MEP. This is the case when CCM transmission is configured to be turned ON. PE1 exits the AC forward defect state if all of the conditions that resulted in entering the defect state are cleared. This includes all of the following conditions: - Any physical layer fault on the Ethernet interface, if detected or notified previously, is removed (e.g. via loss of signal (LoS), or Ethernet Link OAM [802.3] critical link event notifications with "Dying Gasp" or "Critical Event" indication cleared at an upstream node CE1). - A MEP associated with the local AC does not receive any Ethernet AIS frame within a period indicated by previously received AIS, if AIS was resulted in entering the defect state. - A MEP associated with the local AC and configured with CCM transmission on receives a configured number (e.g. 3 or more) of consecutive CCM frames from the peer MEP on CE1 within an interval equal to a multiple (e.g. 3.5) of the CCM transmission period configured for the MEP. 10.1.2. AC Reverse Defect State Entry or Exit PE1 enters the AC reverse defect state if any of the following condition is met: - It detects or is notified of a physical layer fault on the Ethernet interface (e.g. via loss of signal (LoS) or Ethernet Link OAM [802.3] critical link event notifications generated at an upstream node CE1 with "Link Fault" indication). - A MEP configured with CCM transmission turned ON and associated with the local AC receives a CCM frame, with its RDI bit set, from peer MEP in the client domain (e.g. CE1). PE1 exits the AC reverse defect state if all of the conditions that resulted in entering the defect state are cleared. This includes all of the following conditions: - Any physical layer fault on the Ethernet interface, if detected or notified previously, is removed (e.g. via Ethernet Link OAM [802.3] critical link event notifications with "Link Fault" indication cleared at an upstream node CE1). Nadeau, et al. Standards Track [Page 21]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 - A MEP configured with CCM transmission turned ON and associated with the local AC does not receive a CCM frame with RDI bit set, having received a previous CCM frame with RDI bit set from the peer MEP in the client domain (e.g. CE1). 10.2. FR ACs PE1 enters the AC Forward Defect state if any of the following conditions are met: -i. 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. In this case, this status maps across the PE to the corresponding PW only. -ii. The LIV indicates that the link from the PE to the Frame Relay network is down. In this case, the link down indication maps across the PE to all corresponding PWs. -iii. A physical layer alarm is detected on the FR interface. In this case, this status maps across the PE to all corresponding PWs. A PE exits the AC Forward Defect state when all defects it had previously detected have disappeared. The AC reverse defect state is not valid for FR ACs. 10.3. ATM ACs 10.3.1. AC Forward Defect State Entry/Exit PE1 enters the AC forward defect state if any of the following conditions are met: -i. It detects or is notified of a physical layer fault on the ATM interface and/or it terminates an F4 AIS flow or has loss of F4 CC for a VP carrying VCCs. -ii. It terminates an F4 AIS OAM flow, in the case of a VPC, or an F5 AIS OAM flow, in the case of a VCC, indicating that the ATM VPC or VCC is down in the adjacent L2 ATM network (e.g., N1 for PE1). This is applicable to the case of the out-of-band ATM OAM over PW method only. -iii. It detects loss of connectivity on the NS ATM VPC/VCC while terminating ATM continuity checking (ATM CC) with the local ATM network and CE. A PE exits the AC Forward Defect state when all defects it had previously detected have disappeared. The exact conditions under Nadeau, et al. Standards Track [Page 22]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 which a PE exits the AIS state, or declares that connectivity is restored via ATM CC are defined in I.610 [I.610]. 10.3.2. AC Reverse Defect State Entry/Exit A PE enters the AC reverse defect state if any of the following conditions are met: -i. It terminates an F4 RDI OAM flow, in the case of a VPC, or an F5 RDI OAM flow, in the case of a VCC, indicating that the ATM VPC or VCC is down in the adjacent L2 ATM network (e.g., N1 for PE1). This is applicable to the case of the out-of-band ATM OAM over PW method only. A PE exits the AC Reverse Defect state if the AC state transitions to working or to the AC forward defect state. The criteria for exiting the RDI state are described in I.610. 11. PW Forward Defect Entry/Exit procedures 11.1. Procedures in FR Port Mode In case of pure port mode, 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. 11.2. Procedures in ATM Port Mode In case of transparent cell transport, 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. Nadeau, et al. Standards Track [Page 23]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 11.3. PW Forward Defect Entry Procedures 11.3.1. Ethernet AC Procedures When the PW status on PE1 transitions from working to PW forward defect state; PE1's ability to receive user traffic from CE2 is impacted. As a result, PE1 needs to notify CE1 about this problem. Upon entry to the PW Forward Defect State, the following must be done: -i. If PE1 is configured with a MEP associated with the local AC and CCM transmission is not configured to be turned ON, the MEP associated with the AC must transmit AIS frames periodically to the MEP in the client domain (e.g. on CE1) based on configured AIS transmission period. -ii. If PE1 is configured with a MEP associated with the local AC and CCM transmission is configured to be turned ON, and the MEP associated with the AC is configured to support Interface Status TLV in CCM messages, the MEP associated with the AC must transmit CCM frames with Interface Status TLV as being down to the peer MEP in the client domain (e.g. on CE1). -iii. If PE1 is configured with a MEP associated with the local AC and CCM transmission is configured to be turned ON, and the MEP associated with the AC is configured to not support Interface Status TLV in CCM messages, the MEP associated with the AC must stop transmitting CCM frames to the peer MEP in the client domain (e.g. on CE1). -iv. If PE1 is configured to run E-LMI [MEF.16] with CE1 and if E-LMI is used for failure notification, PE1 must transmit E-LMI asynchronous STATUS message with report type Single EVC Asynchronous Status indicating that PW is Not Active. Further, when PE1 enters the forward defect state, it must assume that PE2 has no knowledge of the defect and must send reverse defect failure notification to PE2. For MPLS PSN or MPLS-IP PSN, this is done via either a PW Status notification message indicating a reverse defect; or via VCCV-BFD diagnostic code of reverse defect if VCCV CV type of 0x08 or 0x20 (fault detection and status signaling modes) had been negotiated. When Native Service OAM mechanism is supported on PE, it can also use the NS OAM notification. If PW forward defect is entered as a result of a forward defect notification from PE2 or via loss of control adjacency, no additional action is needed since PE2 is expected to be aware of the defect. Note: The location of the MEP associated with the local AC within a PE can be a down MEP on the port associated with the AC or an Up MEP Nadeau, et al. Standards Track [Page 24]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 associated with an emulated LAN interface within the PE, as defined in L2VPN framework for a VPLS PE. Though for the purposes of VPWS service, VPLS PE architecture is not mandatory, the VPLS PE architecture serves as a generic case where the PE can support both VPWS and VPLS services. 11.3.2. FR AC procedures These procedures are applicable only if the transition from the working state to the PW Forward defect state. A transition from PW reverse defect state to the forward defect state does not require any additional notification procedures to the FR AC as it has already been told the peer is down. -i. PE1 MUST generate a full status report with the Active bit = 0 (and optionally in the asynchronous status message), as per Q.933 annex A, into N1 for the corresponding FR ACs. 11.3.3. ATM AC procedures The following text refers to AIS, RDI and CC without specifying whether it 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 are specified elsewhere (e.g. I.610) and such references complement the descriptions below. Note that it is a network operator option to support segment OAM and to identify and provision PEs as segment end points. On entry to the PW Forward Defect State: -i. PE1 MUST commence AIS insertion into the corresponding AC. -ii. PE1 MUST terminate any CC generation on the corresponding AC. 11.3.4. Additional procedures for a FR PW, and an ATM PW If the PW failure was explicitly detected by PE1, it MUST assume PE2 has no knowledge of the defect and MUST notify PE2 in the form of a reverse defect notification: For PW over MPLS PSN or MPLS-IP PSN: -i. A PW Status message indicating a reverse defect, or -ii. A VCCV-BFD diagnostic code if the optional use of VCCV-BFD notification has been negotiated For PW over L2TP-IP PSN Nadeau, et al. Standards Track [Page 25]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 -i. An L2TP Set-Link Info (SLI) message with a Circuit Status AVP indicating "active" Or, -ii. A VCCV-BFD diagnostic code if the optional use of VCCV-BFD notification has been negotiated Otherwise the entry to the defect state was the result of a notification from PE2 (indicating that PE2 already had knowledge of the fault) or loss of the control adjacency (similarly visible to PE2). 11.4. PW Forward Defect Exit Procedures 11.4.1. Ethernet AC Procedures When the PW status transitions from PW forward defect state to working, PE1's ability to receive user traffic from CE2 is restored. As a result, PE1 needs to cease defect notification to CE1 by performing the following: -i. If PE1 is configured with a a MEP associated with the local AC and CCM transmission is not configured to be turned ON, the MEP associated with the AC must stop transmitting AIS frames towards the peer MEP in the client domain (e.g. on CE1). -ii. If PE1 is configured with a MEP associated with the local AC and CCM transmission is configured to be turned ON, and the MEP associated with the AC is configured to support Interface Status TLV in CCM messages, the MEP associated with the AC must transmit CCM frames with Interface Status TLV as being Up to the peer MEP in the client domain (e.g. on CE1). -iii. If PE1 is configured with a MEP associated with the local AC and CCM transmission is configured to be turned ON, and the MEP associated with the AC is configured to not support Interface Status TLV in CCM messages, the MEP associated with the AC must resume transmitting CCM frames to the peer MEP in the client domain (e.g. on CE1). -iv. If PE1 is configured to run E-LMI [MEF.16] with CE1 and E- LMI is used for fault notification, PE1 must transmit E-LMI asynchronous STATUS message with report type Single EVC Asynchronous Status indicating that PW is Active. Further, if the PW forward defect was explicitly detected by PE1, it must now notify PE2 about clearing of forward defect state by clearing reverse defect notification. For PWs over MPLS PSN or MPLS- IP PSN, this is either done via PW Status message indicating working; or via VCCV-BFD diagnostic code if VCCV CV type of 0x08 or 0x20 (fault detection and status signaling modes) had been negotiated. Nadeau, et al. Standards Track [Page 26]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 When Native Service OAM mechanism is supported on PE, it can also clear the NS OAM notification. If PW forward defect was established via notification from PE2 or via loss of control adjacency, no additional action is needed, since PE2 is expected to be aware of the defect clearing. 11.4.2. FR AC procedures On transition from the PW forward defect state to the reverse defect state PE1 takes no action w.r.t. the AC. On exit from the PW Forward defect state: -i. PE1 MUST generate a full status report with the Active bit = 1 (and optionally in the asynchronous status message), as per Q.933 annex A, into N1 for the corresponding FR ACs. 11.4.3. ATM AC procedures On exit from the PW Forward Defect State: -i. PE1 MUST cease AIS insertion into the corresponding AC. -ii. PE1 MUST resume any CC generation on the corresponding AC. 11.4.4. Additional procedures for a FR PW, and a ATM PW If the PW failure was explicitly detected by PE1, it MUST notify PE2 in the form of clearing the reverse defect notification: For PW over MPLS PSN or MPLS-IP PSN: -i. A PW Status message with the reverse defect indication clear, and the remaining indicators showing either working or a transition to the forward defect state. Or, -ii. A VCCV-BFD diagnostic code with the same attribute as (i) if the optional use of VCCV-BFD notification has been negotiated For PW over L2TP-IP PSN: -i. An L2TP Set-Link Info (SLI) message with a Circuit Status AVP indicating "active" Or, -ii. A VCCV-BFD diagnostic code with the same attributes as (i) if the optional use of VCCV-BFD notification has been negotiated Nadeau, et al. Standards Track [Page 27]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 11.5. PW Reverse Defect Entry Procedures 11.5.1. Ethernet AC Procedures When the PW status transitions from working to PW reverse defect state, PE1's ability to transmit user traffic to CE2 is impacted. As a result, PE needs to notify CE1 about this problem which has been detected by PE1. Upon entry to the PW Reverse Defect State, the following must be done: -i. If PE1 is configured with a MEP associated with the local AC and CCM transmission is configured to be turned ON, the MEP associated with the AC must set the RDI bit in transmitted CCM frames sent to the peer MEP in the client domain (e.g. on CE1). -ii. If PE1 is configured to run E-LMI [MEF.16] with CE1 and E- LMI is used for fault notification, PE1 must transmit E-LMI asynchronous STATUS message with report type Single EVC Asynchronous Status indicating that PW is Not Active. 11.5.2. FR AC procedures On transition from the PW forward defect state to the reverse defect state PE1 takes no action w.r.t. the AC. On entry to the PW reverse defect state -i. PE1 MUST generate a full status report with the Active bit = 0 (and optionally in the asynchronous status message), as per Q.933 annex A, into N1 for the corresponding FR ACs. 11.5.3. ATM AC procedures On entry to the PW Reverse Defect State: -i. PE1 MUST commence RDI insertion into the corresponding AC. This applies to the case of an ATM PW in the out-of- band ATM OAM over PW method only. Nadeau, et al. Standards Track [Page 28]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 11.6. PW Reverse Defect Exit Procedures 11.6.1. Ethernet AC Procedures When the PW status transitions from PW reverse defect state to working, PE1's ability to transmit user traffic to CE2 is restored. As a result, PE1 needs to cease defect notifications to CE1 and perform the following -i. If PE1 is configured with a MEP associated with the local AC and CCM transmission is configured to be turned ON, the MEP associated with the AC must clear the RDI bit in the transmitted CCM frames to the peer MEP (e.g. on CE1). -ii. If PE1 is configured to run E-LMI [MEF.16] with CE1, PE1 must transmit E-LMI asynchronous STATUS message with report type Single EVC Asynchronous Status indicating that PW is Active. 11.6.2. FR AC procedures On transition from the PW reverse defect state to the PW forward defect state PE1 takes no action with respect to the AC. On exit from the PW Reverse defect state: -i. PE1 MUST generate a full status report with the Active bit = 1 (and optionally in the asynchronous status message), as per Q.933 annex A, into N1 for the corresponding FR ACs. 11.6.3. ATM AC procedures On exit from the PW Reverse Defect State: -i. PE1 MUST cease RDI insertion into the corresponding AC. This applies to the case of an ATM PW in the out-of-band ATM OAM over PW method only. 12. AC Defect Entry/Exit Procedures 12.1. AC Forward Defect Entry On entry to the forward defect state, PE1 may need to perform procedures on both the PW and the AC. Nadeau, et al. Standards Track [Page 29]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 12.1.1. Procedures for an Ethernet PW When AC status transitions from working to AC Forward defect state, PE1's ability to receive user traffic from CE1 is impacted. As a result, PE1 needs to notify PE2 and CE1 about this problem. If the AC Forward defect is detected by PE1, it must notify PE2 in the form of a forward defect notification. When NS OAM is not supported on PE1, and for PW over MPLS PSN or MPLS-IP PSN, forward defect notification is done via either PW Status message indicating a forward defect or via VCCV-BFD diagnostic code of forward defect if VCCV CV type of 0x08 or 0x20 (fault detection and status signaling modes) had been negotiated. When Native Service OAM mechanism is supported on PE1, it can also use the NS OAM notification. In addition to above actions, PE1 must perform the following: -i. If PE1 is configured with a MEP associated with the local AC and CCM transmission is configured to be turned ON, the MEP associated with AC must set the RDI bit in transmitted CCM frames. 12.1.2. Procedures for a FR/ATM PW in the out-of-band method On entry to the AC forward defect state, PE1 notifies PE2 of a forward defect: For PW over MPLS PSN or MPLS-IP PSN: -i. A PW Status message indicating forward defect, or -ii. A VCCV-BFD diagnostic code of forward defect if the optional use of VCCV-BFD notification has been negotiated. For PW over L2TP-IP PSN: -i. An L2TP Set-Link Info (SLI) message with a Circuit Status AVP indicating "inactive", along with a more specific extended status [L2TP-Status], or -ii. A VCCV-BFD diagnostic code of forward defect if the optional use of VCCV-BFD notification has been negotiated. Nadeau, et al. Standards Track [Page 30]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 12.1.3. Procedures for a ATM PW in the inband PW Method On entry to the AC forward defect state, PE1 MUST: -i. Commence insertion of ATM AIS cells into the corresponding PW. -ii. If PE1 is originating F4 or F5 I.610 CC cells, PE1 will suspend CC generation for the duration of the defect state. 12.1.4. Additional procedures for ATM ACs On entry to the AC forward defect state PE1 will commence RDI insertion into the AC as per I.610. This procedure is applicable to the out-of-band ATM OAM over PW method only. 12.2. AC Reverse defect entry 12.2.1. Ethernet AC Procedures When AC status transitions from working to AC Reverse defect, PE1's ability to transmit user traffic to CE1 is impacted. As a result, PE1 needs to notify PE2 about this problem. If the AC Reverse defect is detected by PE1, it must notify PE2 in the form of a reverse defect notification. When NS OAM is not supported on PE, in PW over MPLS PSN or MPLS-IP PSN, reverse defect notification is either done via PW Status message indicating a reverse defect; or via VCCV-BFD diagnostic code of reverse defect if VCCV CV type of 0x08 or 0x20 (fault detection and status signaling modes) had been negotiated. When Native Service OAM mechanism is supported on PE, it can also use the NS OAM notification as specified in Section 3.1. 12.2.2. Procedures for a FR/ATM PW in the out-of-band method On entry to the AC reverse defect state, PE1 notifies PE2 of a reverse defect: For PW over MPLS PSN or MPLS-IP PSN: -i. A PW Status message indicating reverse defect,or -ii. A VCCV-BFD diagnostic code of reverse defect if the optional use of VCCV-BFD notification has been negotiated. For PW over L2TP-IP PSN: Nadeau, et al. Standards Track [Page 31]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 -i. An L2TP Set-Link Info (SLI) message with a Circuit Status AVP indicating "inactive", along with a more specific extended status [L2TP-Status], or -ii. A VCCV-BFD diagnostic code of reverse defect if the optional use of VCCV-BFD notification has been negotiated. 12.2.3. Procedures for a ATM PW in the inband PW Method There are no procedures in this case as the AC reverse defect state is not valid for PE1 operating in this method. 12.3. AC Forward Defect Exit 12.3.1. Ethernet AC Procedures When AC status transitions from AC Forward defect to working, PE1's ability to receive user traffic from CE1 is restored. As a result, PE1 needs to cease defect notifications to PE2 and CE1 and perform the following: -i. When NS OAM is not supported on PE1 and for PW over MPLS PSN or MPLS-IP PSN, forward defect notification is cleared via PW Status message indicating a working state; or via VCCV- BFD diagnostic code if VCCV CV type of 0x08 or 0x20 (fault detection and status signaling modes) had been negotiated. -ii. When Native Service OAM mechanism is supported on PE1, PE1 clears the NS OAM notification as specified in Section 3.1. -iii. If PE1 is configured with a MEP associated with the local AC and CCM transmission is configured to be turned ON, the MEP associated with the AC must clear the RDI bit in transmitted CCM frames to the peer MEP in the client domain (e.g. on CE1). 12.3.2. Procedures for a FR/ATM PW in the out-of-band method On exit from the AC forward defect state PE1 notifies PE2 that the forward defect state has cleared (note that this may be a direct state transition to either the working state or the reverse defect state): For PW over MPLS PSN or MPLS-IP PSN: -i. A PW Status message with forward defect clear and the remaining indicators showing either working or reverse defect state, or Nadeau, et al. Standards Track [Page 32]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 -ii. A VCCV-BFD diagnostic code with the same attributes as (i) if the optional use of VCCV-BFD notification has been negotiated. For PW over L2TP-IP PSN: -i. An L2TP Set-Link Info (SLI) message with a Circuit Status AVP indicating "active", or -ii. A VCCV-BFD diagnostic code with the same attributes as (i) if the optional use of VCCV-BFD notification has been negotiated. 12.3.3. Procedures for a ATM PW in the inband PW Method On exit from the AC forward defect state, PE1 MUST: -i. Cease insertion of ATM AIS cells into the corresponding PW. -ii. If PE1 is originating F4 or F5 I.610 CC cells, PE1 will resume CC generation for the duration of the defect state. 12.3.4. Additional procedures for ATM ACs On exit from the AC forward defect state PE1 will cease RDI insertion into the AC as per I.610. This procedure is applicable to the out- of-band ATM OAM over PW method only. 12.4. AC Reverse Defect Exit 12.4.1. Ethernet AC Procedures When AC status transitions from AC Reverse defect to working, PE1's ability to transmit user traffic to CE1 is restored. As a result, PE1 needs to clear notification to PE2. If the AC Reverse defect is cleared, PE1 must clear reverse defect notification to PE2. When NS OAM is not supported on PE1 and for PW over MPLS PSN or MPLS-IP PSN, reverse defect notification is cleared via either a PW Status message indicating a working state or via VCCV-BFD diagnostic code of if VCCV CV type of 0x08 or 0x20 (fault detection and status signaling modes) had been negotiated. When Native Service OAM mechanism is supported on PE1, PE1 can clear NS OAM notification. Nadeau, et al. Standards Track [Page 33]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 12.4.2. Procedures for a FR/ATM PW in the out-of-band method On exit from the AC reverse defect state, PE1 notifies PE2 that the reverse defect state has cleared (note that this may be a direct state transition to either the working state or the forward defect state): For PW over MPLS PSN or MPLS-IP PSN: -i. A PW Status message with the reverse defect indicator cleared and the remaining indicators showing either working or a transition to the forward defect state, or -ii. A VCCV-BFD diagnostic code with the same information as if the optional use of VCCV-BFD notification has been negotiated. For PW over L2TP-IP PSN: -i. An L2TP Set-Link Info (SLI) message with a Circuit Status AVP indicating "active", or -ii. A VCCV-BFD diagnostic code with the same information as -iii. if the optional use of VCCV-BFD notification has been negotiated. 12.4.3. Procedures for a ATM PW in the inband PW method There are no procedures in this case as the AC reverse defect state is not valid for PE1 operating in this method. 13. SONET Encapsulation (CEP) Loss of Connectivity and other SONET/SDH protocol failures on the PW are translated to alarms on the ACs and vice versa. In essence, all defect management procedures are handled entirely in the emulated protocol. There is no need for an interaction between PW defect management and SONET layer defect management. 14. TDM Encapsulation From an OAM perspective, the PSN carrying a TDM PW provides the same function as that of SONET/SDH or ATM network carrying the same low- rate TDM stream. Hence the interworking of defect OAM is similar. For structure-agnostic TDM PWs, the TDM stream is to be carried transparently across the PSN, and this requires TDM OAM indications to be transparently transferred along with the TDM data. For Nadeau, et al. Standards Track [Page 34]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 structure-aware TDM PWs the TDM structure alignment is terminated at ingress to the PSN and regenerated at egress, and hence OAM indications may need to be signaled by special means. In both cases generation of the appropriate emulated OAM indication may be required when the PSN is at fault. Since TDM is a real-time signal, defect indications and performance measurements may be classified into two classes, urgent and deferrable. Urgent messages are those whose contents may not be significantly delayed with respect to the TDM data that they potentially impact, while deferrable messages may arrive at the far end delayed with respect to simultaneously generated TDM data. For example, a forward indication signifying that the TDM data is invalid (e.g. TDM loss of signal, or MPLS loss of packets) is only of use when received before the TDM data is to be played out towards the far end TDM system. It is hence classified as an urgent message, and we can not delegate its signaling to a separate maintenance or management flow. On the other hand, the forward loss of multi-frame synchronization, and most reverse indications do not need to be acted upon before a particular TDM frame is played out. From the above discussion it is evident that the complete solution to OAM for TDM PWs needs to have at least two, and perhaps three components. The required functionality is transparent transfer of native TDM OAM and urgent transfer of indications (by flags) along with the impacted packets. Optionally there may be mapping between TDM and PSN OAM flows. TDM AIS generated in the TDM network due to a fault in that network is generally carried unaltered, although the TDM encapsulations allow for its suppression for bandwidth conservation purposes. Similarly, when the TDM loss of signal is detected at the PE, it will generally emulate TDM AIS. SAToP and the two structure-aware TDM encapsulations have converged on a common set of defect indication flags in the PW control word. When the PE detects or is informed of lack of validity of the TDM signal, it raises the local ("L") defect flag, uniquely identifying the defect as originating in the TDM network. The remote PE must ensure that TDM AIS is delivered to the remote TDM network. When the defect lies in the MPLS network, the remote PE fails to receive packets. The remote PE generates TDM AIS towards its TDM network, and in addition raises the remote defect ("R") flag in its PSN-bound packets, uniquely identifying the defect as originating in the PSN. Finally, defects in the remote TDM network that cause RDI generation in that network, may optionally be indicated by proper setting of the field of valid packets in the opposite direction. Nadeau, et al. Standards Track [Page 35]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 Ap A Native Service Management Ap A.1 Frame Relay Management The management of Frame Relay Bearer Service (FRBS) connections can be accomplished through two distinct methodologies: -i. 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] -ii. 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: - STATUS messages in response to STATUS ENQUIRY messages, these are mandatory. - 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 forward 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. Ap A.2 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 and Nadeau, et al. Standards Track [Page 36]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 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: 1) Alarm indication signal (AIS) 2) Remote Defect indication (RDI). 3) Continuity Check (CC). 4) 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. Ap A.3 Ethernet Management Ethernet OAM mechanisms are broadly classified into two categories: Fault Management (FM) and Performance Monitoring (PM). ITU-T Y.1731 provides coverage for both FM and PM while IEEE 802.1ag provides coverage for a sub-set of FM functions. Ethernet OAM also introduces the concept of Maintenance Entity (ME) which is used to identify the entity that needs to be managed. A ME is inherently a point-to-point association. However, in case of a multipoint association, Maintenance Entity Group (MEG) consisting of different MEs is used. IEEE 802.1 uses the concept of Maintenance Association (MA) which is used to identify both point-to-point and multipoint associations. Each MA consists of Maintenance End Points Nadeau, et al. Standards Track [Page 37]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 (MEPs) which are responsible for originating OAM frames. In between the MEPs, there can also be Maintenance Intermediate Points (MIPs) which do not originate OAM frames however do respond to OAM frames from MEPs. Ethernet OAM allows for hierarchical maintenance entities to allow for simultaneous end-to-end and segment monitoring. This is achieved by having a provision of up to 8 Maintenance Domain Levels (MD It is important to note that the common set of FM mechanisms between IEEE 802.1ag and ITU-T Y.1731 are completely compatible. The common FM mechanisms include: 1) Continuity Check Messages (CCM) 2) Loopback Message (LBM) and Loopback Reply (LBR) 3) Linktrace Message (LTM) and Linktrace Reply (LTR) CCM messages are used for fault detection including misconnections and mis-configurations. Typically CCM messages are sent as multicast frames or Unicast frames and also allow RDI notifications. LBM/LBR are used to perform fault verification, while also allow for MTU verification and CIR/EIR measurements. LTM/LTR can be used for discovering the path traversed between a MEP and another target MIP/MEP in the same MA. LTM/LTR also allow for fault localization. In addition, ITU-T Y.1731 also specifies the following FM functions: 4) Alarm Indication Signal (AIS) AIS allows for fault notification to downstream and upstream nodes. Further, ITU-T Y.1731 also specifies the following PM functions: 5) Loss Measurement Message (LMM) and Reply (LMR) 6) Delay Measurement Message (DMR) and Reply (DMR) 7) 1-way Delay Message (1DM) While LMM/LMR is used to measure Frame Loss Ratio (FLR), DMM/DMR is used to measure single-ended (aka two-way) Frame Delay (FD) and Frame Delay Variation (FDV, also known as Jitter). 1DM can be used for dual-ended (aka one-way) FD and FDV measurements. Nadeau, et al. Standards Track [Page 38]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 15. Security Considerations The mapping messages described in this document do not change the security functions inherent in the actual messages. 16. IANA Considerations None at this time. 17. References 17.1. Normative References [BFD] Katz, D., Ward, D., "Bidirectional Forwarding Detection", draft-ietf-bfd-base-08 (work in progress), March 2008 [FRF.19] Frame Relay Forum, Frame Relay Operations, Administration, and Maintenance Implementation Agreement, March 2001. [RFC792] Postel, J. "Internet Control Message Protocol", RFC792 [ITU-T I.610] Recommendation I.610 "B-ISDN operation and maintenance principles and functions", February 1999 [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 [RFC4379] Kompella, K., Pan, P., Sheth, N., Cooper, D., Swallow, G., Wadhwa, S., Bonica, R., " Detecting MPLS Data Plane Failures", RFC4379, February 2006. [RFC4023] Worster. T., et al., Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE), RFC 4023, March 2005. [RFC5085] Nadeau, T., et al."Pseudo Wire Virtual Circuit Connection Verification (VCCV)", RFC 5085 December 2007. Nadeau, et al. Standards Track [Page 39]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 [Y.1731] "OAM Functions and mechanisms for Ethernet based networks", ITU-T Y.1731, May 2006 [802.1ag] "Connectivity Fault Management", IEEE 802.1ag/D8.1, Jul 2007 [RFC4454] Singh, S., Townsley, M., and C. Pignataro, "Asynchronous Transfer Mode (ATM) over Layer 2 Tunneling Protocol Version 3 (L2TPv3)", RFC 4454, May 2006. [VCCV-BFD] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding Detection (BFD) for the Pseudowire Virtual Circuit Connectivity Verification (VCCV)", draft-ietf-pwe3-vccv-bfd-02 (work in progress), June 2008. [MEF.16] "Ethernet Local Management Interface", MEF.16, January 2006 17.2. Informative References [RFC3985] Bryant, S., "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005. [RFC4377] Nadeau, T. et.al., "OAM Requirements for MPLS Networks", RFC4377, February 2006. [RFC4447] Martini, L., Rosen, E., Smith, T., "Pseudowire Setup and Maintenance using LDP", RFC4447, April 2006. [RFC4446] Martini, L., et al., "IANA Allocations for pseudo Wire Edge to Edge Emulation (PWE3)", RFC4446, April 2006. [RFC4717] Martini, L., et al., "Encapsulation Methods for Transport of ATM Cells/Frame Over IP and MPLS Networks", RFC4717, December 2006 [RFC3916] Xiao, X., McPherson, D., Pate, P., "Requirements for Pseudo Wire Emulation Edge to-Edge (PWE3)", RFC 3916, September 2004 [RFC3209] Awduche, D., et.al. "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001 [L2TP-Status] McGill, N. and C. Pignataro, "L2TPv3 Extended Circuit Status Values", draft-nmcgill-l2tpext-circuit-status-extensions-01 (work in progress), June 2008. Nadeau, et al. Standards Track [Page 40]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 18. Editors' Addresses 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 Luca Martini Cisco Systems, Inc. 9155 East Nichols Avenue, Suite 400 Englewood, CO, 80112 USA EMail: lmartini@cisco.com Carlos Pignataro Cisco Systems, Inc. 7200-12 Kit Creek Road PO Box 14987 Research Triangle Park, NC 27709 USA Email: cpignata@cisco.com Dinesh Mohan Nortel 3500 Carling Ave Ottawa, ON K2H8E9 Canada EMail: mohand@nortel.com Nadeau, et al. Standards Track [Page 41]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 19. Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. 20. Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Nadeau, et al. Standards Track [Page 42]
Internet Draft draft-ietf-pwe3-oam-msg-map-07.txt July 2008 21. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Nadeau, et al. Standards Track [Page 43]
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This is an older version of an Internet-Draft that was ultimately published as RFC 6310.
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