GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc7023

Internet Engineering Task Force (IETF) D. Mohan, Ed. Request for Comments: 7023 Nortel Networks Category: Standards Track N. Bitar, Ed. ISSN: 2070-1721 Verizon

                                                       A. Sajassi, Ed.
                                                                 Cisco
                                                             S. Delord
                                                        Alcatel-Lucent
                                                              P. Niger
                                                        France Telecom
                                                                R. Qiu
                                                               Juniper
                                                          October 2013
MPLS and Ethernet Operations, Administration, and Maintenance (OAM)
                            Interworking

Abstract

 This document specifies the mapping of defect states between Ethernet
 Attachment Circuits (ACs) and associated Ethernet pseudowires (PWs)
 connected in accordance with the Pseudowire Emulation Edge-to-Edge
 (PWE3) architecture to realize an end-to-end emulated Ethernet
 service.  It standardizes the behavior of Provider Edges (PEs) with
 respect to Ethernet PW and AC defects.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7023.

Mohan, et al. Standards Track [Page 1] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

Copyright Notice

 Copyright (c) 2013 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Mohan, et al. Standards Track [Page 2] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

Table of Contents

 1. Introduction ....................................................4
    1.1. Specification of Requirements ..............................4
 2. Overview ........................................................4
    2.1. Reference Model and Defect Locations .......................6
    2.2. Abstract Defect States .....................................6
 3. Abbreviations and Terminology ...................................7
    3.1. Abbreviations ..............................................7
    3.2. Terminology ................................................8
 4. PW Status and Defects ...........................................9
    4.1. Use of Native Service (NS) Notification ....................9
    4.2. Use of PW Status Notification for MPLS PSNs ...............10
    4.3. Use of BFD Diagnostic Codes ...............................10
    4.4. PW Defect States Entry and Exit Criteria ..................11
         4.4.1. PW Receive Defect State Entry and Exit .............11
         4.4.2. PW Transmit Defect State Entry and Exit ............11
 5. Ethernet AC Defect States Entry and Exit Criteria ..............12
    5.1. AC Receive Defect State Entry and Exit ....................12
    5.2. AC Transmit Defect State Entry and Exit ...................13
 6. Ethernet AC and PW Defect States Interworking ..................14
    6.1. PW Receive Defect State Entry Procedures ..................14
    6.2. PW Receive Defect State Exit Procedures ...................15
    6.3. PW Transmit Defect State Entry Procedures .................16
    6.4. PW Transmit Defect State Exit Procedures ..................16
    6.5. AC Receive Defect State Entry Procedures ..................16
    6.6. AC Receive Defect State Exit Procedures ...................17
    6.7. AC Transmit Defect State Entry Procedures .................17
    6.8. AC Transmit Defect State Exit Procedures ..................18
 7. Security Considerations ........................................18
 8. Acknowledgments ................................................19
 9. References .....................................................19
    9.1. Normative References ......................................19
    9.2. Informative References ....................................20
 Appendix A. Ethernet Native Service Management ....................21

Mohan, et al. Standards Track [Page 3] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

1. Introduction

 RFC 6310 [RFC6310] specifies the mapping and notification of defect
 states between a pseudowire (PW) and the Attachment Circuit (AC) of
 the end-to-end emulated service.  It standardizes the behavior of
 Provider Edges (PEs) with respect to PW and AC defects for a number
 of technologies (e.g., Asynchronous Transfer Mode (ATM) and Frame
 Relay (FR)) emulated over PWs in MPLS and MPLS/IP Packet Switched
 Networks (PSNs).  However, [RFC6310] does not describe this function
 for the Ethernet PW service owing to its unique characteristics.
 This document specifies the mapping of defect states between ACs and
 associated Ethernet PWs connected in accordance with the PWE3
 architecture [RFC3985] to realize an end-to-end emulated Ethernet
 service.  This document augments the mapping of defect states between
 a PW and associated AC of the end-to-end emulated service in
 [RFC6310].  Similar to [RFC6310], the intent of this document is to
 standardize the behavior of PEs with respect to failures on Ethernet
 ACs and PWs, so that there is no ambiguity about the alarms generated
 and consequent actions undertaken by PEs in response to specific
 failure conditions.

1.1. 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 [RFC2119].

2. Overview

 There are a number of Operations, Administration, and Maintenance
 (OAM) technologies defined for Ethernet, providing various
 functionalities.  This document covers the following Ethernet OAM
 mechanisms and their interworking with PW OAM mechanisms:
  1. Ethernet Link OAM [802.3]
  2. Ethernet Local Management Interface (E-LMI) [MEF16]
  3. Ethernet Continuity Check (CC) [CFM] [Y.1731]
  4. Ethernet Alarm Indication Signaling (AIS) and Remote Defect

Indication (RDI) [Y.1731]

 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 physical port, there may be some application of
 Ethernet Link OAM [802.3].  Further, E-LMI [MEF16] also allows for
 some Ethernet Virtual Circuit (EVC) defect states to be communicated
 across an Ethernet User Network Interface (UNI) where Ethernet UNI
 constitutes a single-hop Ethernet link (i.e., without any bridges

Mohan, et al. Standards Track [Page 4] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

 compliant with IEEE 802.1Q/.1ad in between).  There may be some
 application of E-LMI [MEF16] for failure notification across single-
 hop Ethernet ACs in certain deployments that specifically do not
 support IEEE Connectivity Fault Management [CFM] and/or ITU-T Y.1731
 [Y.1731], simply referred to as CFM and Y.1731, respectively, in this
 document.  Mechanisms based on Y.1731 and CFM are applicable in all
 types of Ethernet ACs.  Ethernet Link OAM and E-LMI 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.  This is referred to as the "single
 emulated OAM loop mode" per [RFC6310].  For Ethernet, as an example,
 CFM continuity check messages (CCMs) between two Maintenance Entity
 Group End Points (MEPs) can be transported transparently as user data
 over the corresponding PW.  At MEP locations, service failure is
 detected when CCMs are not received over an interval that is 3.5
 times the local CCM transmission interval.  This is one of the
 failure conditions detected via continuity check.  MEP peers can
 exist between customer edge (CE) endpoints (MEPs of a given
 Maintenance Entity Group (MEG) reside on the CEs), between PE pairs
 (the MEPs of a given MEG reside on the PEs), or between the CE and PE
 (the MEPs of a given MEG reside on the PE and CE), as long as the MEG
 level nesting rules are maintained.  It should be noted that Ethernet
 allows the definition of up to 8 MEG levels, each comprised of MEPs
 (Down MEPs and Up MEPs) and Maintenance Entity Group Intermediate
 Points (MIPs).  These levels can be nested or touching.  MEPs and
 MIPs generate and process messages in the same MEG level.  Thus, in
 this document, when we refer to messages sent by a MEP or a MIP to a
 peer MEP or MIP, these MEPs and MIPs are in the same MEG level.
 When interworking two networking domains, such as native Ethernet and
 PWs to provide an end-to-end emulated service, there is a 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 enabled, at a PE to detect the failure
 of an 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 the case of Ethernet,
 necessitating the need for fault notification message mapping between
 the PW domain and the NS domain.

Mohan, et al. Standards Track [Page 5] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

 For Multi-Segment PWs (MS-PWs) [RFC5659], Switching PEs (S-PEs) are
 not aware of the NS.  Thus, failure detection and notification at
 S-PEs will be based on PW OAM mechanisms.  Mapping between PW OAM and
 NS OAM will be required at the Terminating PEs (T-PEs) to propagate
 the failure notification to the EVC end points.

2.1. Reference Model and Defect Locations

 Figure 1 was used in [RFC6310]; it is reproduced in this document as
 a reference to highlight defect locations.
               ACs             PSN tunnel               ACs
                      +----+                  +----+
      +----+          | PE1|==================| PE2|          +----+
      |    |---(a)---(b)..(c)......PW1..(d)..(e)..(f)---(g)---|    |
      | 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

2.2. Abstract Defect States

 Abstract defect states are also introduced in [RFC6310].  As shown in
 Figure 2, this document uses the same conventions as [RFC6310].  It
 may be noted, however, that CE devices, shown in Figure 2, do not
 necessarily have to be end customer devices.  These are essentially
 devices in client network segments that are connecting to the Packet
 Switched Network (PSN) for the emulated services.
                                 +-----+
            ----AC receive ----->|     |-----PW transmit---->
        CE1                      | PE1 |                    PE2/CE2
            <---AC transmit------|     |<----PW receive-----
                                 +-----+
   (arrows indicate direction of user traffic impacted by a defect)
    Figure 2: Transmit and Receive Defect States and Notifications

Mohan, et al. Standards Track [Page 6] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

 The procedures outlined in this document define the entry and exit
 criteria for each of the four defect states with respect to Ethernet
 ACs and corresponding PWs; this document also defines the consequent
 actions that PE1 MUST support to properly interwork these defect
 states and corresponding notification messages between the PW domain
 and the native service (NS) domain.  Receive defect state SHOULD have
 precedence over transmit defect state in terms of handling, when both
 transmit and receive defect states are identified simultaneously.
 Following is a summary of the defect states from the viewpoint of PE1
 in Figure 2:
  1. A PW receive defect at PE1 impacts PE1's ability to receive

traffic on the PW. Entry and exit criteria for the PW receive

    defect state are described in Section 4.4.1.
  1. A PW transmit defect at PE1 impacts PE1's ability to send user

traffic toward CE2. PE1 MAY be notified of a PW transmit defect

    via a Reverse Defect Indication from PE2, which could point to
    problems associated with PE2's inability to receive traffic on the
    PW or PE2's inability to transmit traffic on its local AC.  Entry
    and exit criteria for the PW transmit defect state are described
    in Section 4.4.2.
  1. An AC receive defect at PE1 impacts PE1's ability to receive user

traffic from the client domain attached to PE1 via that AC. Entry

    and exit criteria for the AC receive defect state are described in
    Section 5.1.
  1. An AC transmit defect at PE1 impacts PE1's ability to send user

traffic on the local AC. Entry and exit criteria for the AC

    transmit defect state are described in Section 5.2.

Mohan, et al. Standards Track [Page 7] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

3. Abbreviations and Terminology

3.1. Abbreviations

 AC    Attachment Circuit
 AIS   Alarm Indication Signal
 BFD   Bidirectional Forwarding Detection
 CC    Continuity Check
 CCM   Continuity Check Message
 CE    Customer Edge
 CV    Connectivity Verification
 E-LMI Ethernet Local Management Interface
 EVC   Ethernet Virtual Circuit
 LDP   Label Distribution Protocol
 LoS   Loss of Signal
 MA    Maintenance Association
 MD    Maintenance Domain
 ME    Maintenance Entity
 MEG   Maintenance Entity Group
 MEP   MEG End Point
 MIP   MEG Intermediate Point
 MPLS  Multiprotocol Label Switching
 MS-PW Multi-Segment Pseudowire
 NS    Native Service
 OAM   Operations, Administration, and Maintenance
 PE    Provider Edge
 PSN   Packet Switched Network
 PW    Pseudowire
 RDI   Remote Defect Indication when used in the context of CCM
 RDI   Reverse Defect Indication when used to semantically refer to
       defect indication in the reverse direction
 S-PE  Switching Provider Edge
 T-PE  Terminating Provider Edge
 TLV   Type-Length Value
 VCCV  Virtual Circuit Connectivity Verification

3.2. Terminology

 This document uses the following terms with corresponding
 definitions:
  1. MEG Level: identifies a value in the range of 0-7 associated with

an Ethernet OAM frame. MEG level identifies the span of the

    Ethernet OAM frame.
  1. MEG End Point (MEP): is responsible for origination and

termination of OAM frames for a given MEG.

Mohan, et al. Standards Track [Page 8] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

  1. MEG Intermediate Point (MIP): is located between peer MEPs and can

process OAM frames but does not initiate them.

  1. MPLS PSN: a PSN that makes use of MPLS Label-Switched Paths

[RFC3031] as the tunneling technology to forward PW packets.

  1. MPLS/IP PSN: a PSN that makes use of MPLS-in-IP tunneling

[RFC4023] to tunnel MPLS-labeled PW packets over IP tunnels.

 Further, this document also uses the terminology and conventions used
 in [RFC6310].

4. PW Status and Defects

 [RFC6310] introduces a range of defects that impact PW status.  All
 these defect conditions are applicable for Ethernet PWs.
 Similarly, there are different mechanisms described in [RFC6310] to
 detect PW defects, depending on the PSN type (e.g., MPLS PSN or
 MPLS/IP PSN).  Any of these mechanisms can be used when monitoring
 the state of Ethernet PWs.  [RFC6310] also discusses the
 applicability of these failure detection mechanisms.

4.1. Use of Native Service (NS) Notification

 When two PEs terminate an Ethernet PW with associated MEPs, each PE
 can use native service (NS) OAM capabilities for failure
 notifications by transmitting appropriate NS OAM messages over the
 corresponding PW to the remote PE.  Options include:
  1. Sending of AIS frames from the local MEP to the MEP on the remote

PE when the MEP needs to convey PE receive defects and when CCM

    transmission is disabled.
  1. Suspending transmission of CCM frames from the local MEP to the

peer MEP on the remote PE to convey PE receive defects when CCM

    transmission is enabled.
  1. Setting the RDI bit in transmitted CCM frames when loss of CCMs

from the peer MEP is detected or when the PE needs to convey PW

    reverse defects.
 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 state on the peer PE:
  1. Stopping AIS frame transmission from the local MEP to the MEP on

the remote PE to clear PW receive defects.

Mohan, et al. Standards Track [Page 9] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

  1. Resuming transmission of CCM frames from the local MEP to the peer

MEP on the remote PE to clear PW forward defect notification when

    CCM transmission is enabled.
  1. Clearing the RDI bit in transmitted CCM frames to clear PW

transmit defect notification when CCM transmission is enabled.

4.2. Use of PW Status Notification for MPLS PSNs

 RFC 4447 [RFC4447] specifies that for PWs that have been set up using
 the Label Distribution Protocol (LDP), the default mechanism to
 signal status and defects for ACs and PWs is the LDP status
 notification message.  For PWs established over an MPLS or MPLS/IP
 PSN using other mechanisms (e.g., static configuration), in-band
 signaling using VCCV-BFD [RFC5885] SHOULD be used to convey AC and PW
 status and defects.  Alternatively, the mechanisms defined in
 [RFC6478] MAY be used.
 [RFC6310] identifies the following PW defect status code points:
  1. Forward defect: corresponds to a logical OR of Local Attachment

Circuit (ingress) Receive Fault, Local PSN-facing PW (egress)

    Transmit Fault, and Pseudowire Not Forwarding fault.
  1. Reverse defect: corresponds to a logical OR of Local Attachment

Circuit (egress) Transmit Fault and Local PSN-facing PW (ingress)

    Receive Fault.
 There are also scenarios where a PE carries out PW label withdrawal
 instead of PW status notification.  These include administrative
 disablement of the PW or loss of the Target LDP session with the peer
 PE.

4.3. Use of BFD Diagnostic Codes

 When using VCCV, the control channel type and Connectivity
 Verification (CV) type are agreed on between the peer PEs using the
 VCCV parameter field signaled as a sub-TLV of the interface
 parameters TLV when using FEC 129 and the interface parameter sub-TLV
 when using FEC 128 [RFC5085].
 As defined in [RFC6310], when a CV type of 0x04 or 0x10 is used to
 indicate that BFD is used for PW fault detection only, PW defect is
 detected via the BFD session while other defects, such as AC defect
 or PE internal defects preventing it from forwarding traffic, are
 communicated via an LDP status notification message in MPLS and
 MPLS/IP PSNs or other mechanisms in L2TP/IP PSNs.

Mohan, et al. Standards Track [Page 10] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

 Similarly, when a CV type of 0x08 or 0x20 is used to indicate that
 BFD is used for both PW fault detection and AC/PW fault notification,
 all defects are signaled via BFD.

4.4. PW Defect States Entry and Exit Criteria

4.4.1. PW Receive Defect State Entry and Exit

 As described in Section 6.2.1 of [RFC6310], PE1 will enter the PW
 receive defect state if one or more of the following occur:
  1. It receives a Forward Defect Indication (FDI) from PE2 either

indicating a receive defect on the remote AC or indicating that

    PE2 detected or was notified of a downstream PW fault.
  1. It detects loss of connectivity on the PSN tunnel upstream of PE1,

which affects the traffic it receives from PE2.

  1. It detects a loss of PW connectivity through VCCV-BFD, VCCV-Ping,

or NS OAM mechanisms (i.e., CC) when enabled, which affects the

    traffic it receives from PE2.
 Note that if the PW LDP 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 receive
 defect state.
 PE1 will exit the PW receive defect state when the following
 conditions are met.  Note that this may result in a transition to the
 PW operational state or the PW transmit defect state.
  1. All previously detected defects have disappeared.
  2. PE2 cleared the FDI, if applicable.

4.4.2. PW Transmit Defect State Entry and Exit

 PE1 will enter the PW transmit defect state if the following
 conditions occur:
  1. It receives a Reverse Defect Indication (RDI) from PE2 either

indicating a transmit fault on the remote AC or indicating that

    PE2 detected or was notified of an upstream PW fault.
  1. 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 RDI or if it has entered the PW receive defect
 state.

Mohan, et al. Standards Track [Page 11] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

5. Ethernet AC Defect States Entry and Exit Criteria

5.1. AC Receive Defect State Entry and Exit

 PE1 enters the AC receive defect state if any of the following
 conditions is met:
  1. 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 or via a client Signal
    Fail message [Y.1731].
  1. A MEP associated with the local AC receives an Ethernet AIS frame

from CE1.

  1. A MEP associated with the local AC does not receive CCM frames

from the peer MEP in the client domain (e.g., CE1) within an

    interval equal to 3.5 times the CCM transmission period configured
    for the MEP.  This is the case when CCM transmission is enabled.
  1. A CCM has an Interface Status TLV indicating interface down.

Other CCM Interface Status TLVs will not be used to indicate

    failure or recovery from failure.
 It should be noted that when a MEP at a PE or a CE receives a CCM
 with the wrong MEG ID, MEP ID, or MEP level, the receiving PE or CE
 SHOULD treat such an event as an AC receive defect.  In any case, if
 such events persist for 3.5 times the MEP local CCM transmission
 time, loss of continuity will be declared at the receiving end.
 PE1 exits the AC receive defect state if all of the conditions that
 resulted in entering the defect state are cleared.  This includes all
 of the following conditions:
  1. Any physical-layer fault on the Ethernet interface, if detected or

where PE1 was notified previously, is removed (e.g., loss of

    signal (LoS) cleared or Ethernet Link OAM [802.3] critical link
    event notifications with "Dying Gasp" or "Critical Event"
    indications cleared at an upstream node CE1).
  1. A MEP associated with the local AC does not receive any Ethernet

AIS frame within a period indicated by previously received AIS if

    AIS resulted in entering the defect state.

Mohan, et al. Standards Track [Page 12] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

  1. A MEP associated with the local AC and configured with CCM enabled

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 (3.5) of the CCM transmission period configured for the
    MEP.
  1. CCM indicates interface status up.

5.2. AC Transmit Defect State Entry and Exit

 PE1 enters the AC transmit defect state if any of the following
 conditions is met:
  1. It detects or is notified of a physical-layer fault on the

Ethernet interface where the AC is configured (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).
  1. A MEP configured with CCM transmission enabled and associated with

the local AC receives a CCM frame, with its RDI (Remote Defect

    Indication) bit set, from the peer MEP in the client domain (e.g.,
    CE1).
 PE1 exits the AC transmit defect state if all of the conditions that
 resulted in entering the defect state are cleared.  This includes all
 of the following conditions:
  1. Any physical-layer fault on the Ethernet interface, if detected or

where PE1 was notified previously, is removed (e.g., LoS cleared

    or Ethernet Link OAM [802.3] critical link event notifications
    with "Link Fault" indication cleared at an upstream node CE1).
  1. A MEP configured with CCM transmission enabled and associated with

the local AC does not receive a CCM frame with the RDI bit set,

    having received a previous CCM frame with the RDI bit set from the
    peer MEP in the client domain (e.g., CE1).

Mohan, et al. Standards Track [Page 13] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

6. Ethernet AC and PW Defect States Interworking

6.1. PW Receive Defect State Entry Procedures

 When the PW status on PE1 transitions from working to PW receive
 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 receive defect state, the following MUST be
 done:
  1. If PE1 is configured with a Down MEP associated with the local AC

and CCM transmission is not enabled, the MEP associated with the

    AC MUST transmit AIS frames periodically to the peer MEP in the
    client domain (e.g., on CE1) based on the configured AIS
    transmission period.
  1. If PE1 is configured with a Down MEP associated with the local AC,

CCM transmission is enabled, and the MEP associated with the AC is

    configured to support the Interface Status TLV in CCMs, the MEP
    associated with the AC MUST transmit CCM frames with the Interface
    Status TLV as being Down to the peer MEP in the client domain
    (e.g., on CE1).
  1. If PE1 is configured with a Down MEP associated with the local AC,

CCM transmission is enabled, and the MEP associated with the AC is

    configured to not support the Interface Status TLV in CCMs, the
    MEP associated with the AC MUST stop transmitting CCM frames to
    the peer MEP in the client domain (e.g., on CE1).
  1. If PE1 is configured to run E-LMI [MEF16] with CE1 and if E-LMI is

used for failure notification, PE1 MUST transmit an E-LMI

    asynchronous STATUS message with report type Single EVC
    Asynchronous Status indicating that the PW is Not Active.
 Further, when PE1 enters the receive defect state, it MUST assume
 that PE2 has no knowledge of the defect and MUST send a reverse
 defect failure notification to PE2.  For MPLS PSN or MPLS/IP PSN,
 this is either done via a PW status notification message indicating a
 reverse defect or done via a VCCV-BFD diagnostic code of reverse
 defect if a VCCV CV type of 0x08 or 0x20 had been negotiated.  When a
 native service OAM mechanism is supported on PE1, it can also use the
 NS OAM notification as specified in Section 4.1.
 If PW receive defect state 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.

Mohan, et al. Standards Track [Page 14] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

6.2. PW Receive Defect State Exit Procedures

 When the PW status transitions from PW receive 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:
  1. If PE1 is configured with a Down MEP associated with the local AC

and CCM transmission is not enabled, the MEP associated with the

    AC MUST stop transmitting AIS frames towards the peer MEP in the
    client domain (e.g., on CE1).
  1. If PE1 is configured with a Down MEP associated with the local AC,

CCM transmission is enabled, and the MEP associated with the AC is

    configured to support the Interface Status TLV in CCMs, the MEP
    associated with the AC MUST transmit CCM frames with the Interface
    Status TLV as being Up to the peer MEP in the client domain (e.g.,
    on CE1).
  1. If PE1 is configured with a Down MEP associated with the local AC,

CCM transmission is enabled, and the MEP associated with the AC is

    configured to not support the Interface Status TLV in CCMs, the
    MEP associated with the AC MUST resume transmitting CCM frames to
    the peer MEP in the client domain (e.g., on CE1).
  1. If PE1 is configured to run E-LMI [MEF16] with CE1 and E-LMI is

used for fault notification, PE1 MUST transmit an E-LMI

    asynchronous STATUS message with report type Single EVC
    Asynchronous Status indicating that the PW is Active.
 Further, if the PW receive defect was explicitly detected by PE1, it
 MUST now notify PE2 about clearing of receive defect state by
 clearing the reverse defect notification.  For PW over MPLS PSN or
 MPLS/IP PSN, this is either done via a PW status message indicating a
 working state or done via a VCCV-BFD diagnostic code if a VCCV CV
 type of 0x08 or 0x20 had been negotiated.  When a native service OAM
 mechanism is supported on PE, it can also clear the NS OAM
 notification as specified in Section 4.1.
 If PW receive 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.

Mohan, et al. Standards Track [Page 15] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

6.3. PW Transmit Defect State Entry Procedures

 When the PW status transitions from working to PW transmit defect
 state, PE1's ability to transmit user traffic to CE2 is impacted.  As
 a result, PE1 needs to notify CE1 about this problem.
 Upon entry to the PW transmit defect state, the following MUST be
 done:
  1. If PE1 is configured with a Down MEP associated with the local AC

and CCM transmission is enabled, the MEP associated with the AC

    MUST set the RDI bit in transmitted CCM frames or send a status
    TLV with interface down to the peer MEP in the client domain
    (e.g., on CE1).
  1. If PE1 is configured to run E-LMI [MEF16] with CE1 and E-LMI is

used for fault notification, PE1 MUST transmit an E-LMI

    asynchronous STATUS message with report type Single EVC
    Asynchronous Status indicating that the PW is Not Active.
  1. If the PW failure was detected by PE1 without receiving a reverse

defect notification from PE2, PE1 MUST assume PE2 has no knowledge

    of the defect and MUST notify PE2 by sending an FDI.

6.4. PW Transmit Defect State Exit Procedures

 When the PW status transitions from PW transmit 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:
  1. If PE1 is configured with a Down MEP associated with the local AC

and CCM transmission is enabled, the MEP associated with the AC

    MUST clear the RDI bit in the transmitted CCM frames to the peer
    MEP or send a status TLV with interface up to the peer MEP in the
    client domain (e.g., on CE1).
  1. If PE1 is configured to run E-LMI [MEF16] with CE1, PE1 MUST

transmit an E-LMI asynchronous STATUS message with report type

    Single EVC Asynchronous Status indicating that the PW is Active.
  1. PE1 MUST clear the FDI to PE2, if applicable.

6.5. AC Receive Defect State Entry Procedures

 When AC status transitions from working to AC receive 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.

Mohan, et al. Standards Track [Page 16] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

 If the AC receive 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, in PW over MPLS PSN or MPLS/IP
 PSN, a forward defect notification is either done via a PW status
 message indicating a forward defect or done via a VCCV-BFD diagnostic
 code of forward defect if a VCCV CV type of 0x08 or 0x20 had been
 negotiated.
 When a native service OAM mechanism is supported on PE1, it can also
 use the NS OAM notification as specified in Section 4.1.
 In addition to the above actions, PE1 MUST perform the following:
  1. If PE1 is configured with a Down MEP associated with the local AC

and CCM transmission is enabled, the MEP associated with the AC

    MUST set the RDI bit in transmitted CCM frames.

6.6. AC Receive Defect State Exit Procedures

 When AC status transitions from AC receive defect state 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:
  1. When NS OAM is not supported on PE1, in PW over MPLS PSN or

MPLS/IP PSN, the forward defect notification is cleared via a PW

    status message indicating a working state or via a VCCV-BFD
    diagnostic code if a VCCV CV type of 0x08 or 0x20 had been
    negotiated.
  1. When a native service OAM mechanism is supported on PE1, PE1

clears the NS OAM notification as specified in Section 4.1.

  1. If PE1 is configured with a Down MEP associated with the local AC

and CCM transmission is enabled, 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).

6.7. AC Transmit Defect State Entry Procedures

 When AC status transitions from working to AC transmit defect state,
 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 transmit defect is detected by PE1, it MUST notify PE2 in
 the form of a reverse defect notification.

Mohan, et al. Standards Track [Page 17] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

 When NS OAM is not supported on PE1, in PW over MPLS PSN or MPLS/IP
 PSN, a reverse defect notification is either done via a PW status
 message indicating a reverse defect or done via a VCCV-BFD diagnostic
 code of reverse defect if a VCCV CV type of 0x08 or 0x20 had been
 negotiated.
 When a native service OAM mechanism is supported on PE1, it can also
 use the NS OAM notification as specified in Section 4.1.

6.8. AC Transmit Defect State Exit Procedures

 When AC status transitions from AC transmit defect state to working,
 PE1's ability to transmit user traffic to CE1 is restored.  As a
 result, PE1 MUST clear the reverse defect notification to PE2.
 When NS OAM is not supported on PE1, in PW over MPLS PSN or MPLS/IP
 PSN, the reverse defect notification is cleared via a PW status
 message indicating a working state or via a VCCV-BFD diagnostic code
 if a VCCV CV type of 0x08 or 0x20 had been negotiated.
 When a native service OAM mechanism is supported on PE1, PE1 can
 clear NS OAM notification as specified in Section 4.1.

7. Security Considerations

 The OAM interworking mechanisms described in this document do not
 change the security functions inherent in the actual messages.  All
 generic security considerations applicable to PW traffic specified in
 Section 10 of [RFC3985] are applicable to NS OAM messages transferred
 inside the PW.
 The security considerations in Section 10 of [RFC5085] for VCCV apply
 to the OAM messages thus transferred.  Security considerations
 applicable to the PWE3 control protocol as described in Section 8.2
 of [RFC4447] apply to OAM indications transferred using the LDP
 status message.
 Since the mechanisms of this document enable propagation of OAM
 messages and fault conditions between native service networks and
 PSNs, continuity of the end-to-end service depends on a trust
 relationship between the operators of these networks.  Security
 considerations for such scenarios are discussed in Section 7 of
 [RFC5254].

Mohan, et al. Standards Track [Page 18] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

8. Acknowledgments

 The authors are thankful to Samer Salam, Matthew Bocci, Yaakov Stein,
 David Black, Lizhong Jin, Greg Mirsky, Huub van Helvoort, and Adrian
 Farrel for their valuable input and comments.

9. References

9.1. Normative References

 [802.3]    IEEE, "Part 3: Carrier Sense Multiple Access with
            Collision Detection (CSMA/CD) Access Method and Physical
            Layer Specifications (Clause 57 for Operations,
            Administration, and Maintenance)", IEEE Std 802.3-2005,
            December 2005.
 [CFM]      IEEE, "Connectivity Fault Management clause of IEEE
            802.1Q", IEEE 802.1Q, 2013.
 [MEF16]    Metro Ethernet Forum, "Ethernet Local Management Interface
            (E-LMI)", Technical Specification MEF16, January 2006.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC4447]  Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and
            G. Heron, "Pseudowire Setup and Maintenance Using the
            Label Distribution Protocol (LDP)", RFC 4447, April 2006.
 [RFC5085]  Nadeau, T., Ed., and C. Pignataro, Ed., "Pseudowire
            Virtual Circuit Connectivity Verification (VCCV): A
            Control Channel for Pseudowires", RFC 5085, December 2007.
 [RFC5885]  Nadeau, T., Ed., and C. Pignataro, Ed., "Bidirectional
            Forwarding Detection (BFD) for the Pseudowire Virtual
            Circuit Connectivity Verification (VCCV)", RFC 5885, June
            2010.
 [RFC6310]  Aissaoui, M., Busschbach, P., Martini, L., Morrow, M.,
            Nadeau, T., and Y(J). Stein, "Pseudowire (PW) Operations,
            Administration, and Maintenance (OAM) Message Mapping",
            RFC 6310, July 2011.
 [RFC6478]  Martini, L., Swallow, G., Heron, G., and M. Bocci,
            "Pseudowire Status for Static Pseudowires", RFC 6478, May
            2012.

Mohan, et al. Standards Track [Page 19] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

 [Y.1731]   ITU-T, "OAM functions and mechanisms for Ethernet based
            networks", ITU-T Y.1731, July 2011.

9.2. Informative References

 [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
            Label Switching Architecture", RFC 3031, January 2001.
 [RFC3985]  Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire Emulation
            Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005.
 [RFC4023]  Worster, T., Rekhter, Y., and E. Rosen, Ed.,
            "Encapsulating MPLS in IP or Generic Routing Encapsulation
            (GRE)", RFC 4023, March 2005.
 [RFC5254]  Bitar, N., Ed., Bocci, M., Ed., and L. Martini, Ed.,
            "Requirements for Multi-Segment Pseudowire Emulation Edge-
            to-Edge (PWE3)", RFC 5254, October 2008.
 [RFC5659]  Bocci, M. and S. Bryant, "An Architecture for Multi-
            Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
            October 2009.

Mohan, et al. Standards Track [Page 20] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

Appendix A. Ethernet Native Service Management

 This appendix is informative.
 Ethernet OAM mechanisms are broadly classified into two categories:
 Fault Management (FM) and Performance Monitoring (PM).  ITU-T Y.1731
 [Y.1731] provides coverage for both FM and PM while IEEE CFM [CFM]
 provides coverage for a subset of FM functions.
 Ethernet OAM also introduces the concept of a Maintenance Entity
 (ME), which is used to identify the entity that needs to be managed.
 An ME is inherently a point-to-point association.  However, in the
 case of a multipoint association, a Maintenance Entity Group (MEG)
 consisting of different MEs is used.  IEEE 802.1 uses the concept of
 a Maintenance Association (MA), which is used to identify both point-
 to-point and multipoint associations.  Each MEG/MA consists of MEG
 End Points (MEPs) that are responsible for originating OAM frames.
 In between the MEPs, there can also be MEG Intermediate Points (MIPs)
 that do not originate OAM frames but 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 MEG levels (MD levels), where each
 MEP or MIP is associated with a specific MEG level.
 It is important to note that the FM mechanisms common to both IEEE
 CFM [CFM] and ITU-T Y.1731 [Y.1731] are completely compatible.
 The common FM mechanisms include:
 1) Continuity Check Message (CCM)
 2) Loopback Message (LBM) and Loopback Reply (LBR)
 3) Link Trace Message (LTM) and Link Trace Reply (LTR)
 CCMs are used for fault detection, including misconnections and
 misconfigurations.  Typically, CCMs are sent as multicast frames or
 unicast frames and also allow RDI notifications.  LBM and LBR are
 used to perform fault verification, while also allowing for MTU
 verification and CIR/EIR (Committed Information Rate / Excess
 Information Rate) measurements.  LTM and LTR can be used for
 discovering the path traversed between a MEP and another target
 MIP/MEP in the same MEG.  LTM and LTR also allow for fault
 localization.

Mohan, et al. Standards Track [Page 21] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

 In addition, ITU-T Y.1731 [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 [Y.1731] also specifies the following PM
 functions:
 5) Loss Measurement Message (LMM) and Loss Measurement Reply (LMR)
 6) Delay Measurement Message (DMM) and Delay Measurement Reply (DMR)
 7) 1-way Delay Measurement (1DM)
 While LMM and LMR are used to measure Frame Loss Ratio (FLR), DMM and
 DMR are 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.

Mohan, et al. Standards Track [Page 22] RFC 7023 MPLS and Ethernet OAM Interworking October 2013

Authors' Addresses

 Dinesh Mohan (editor)
 Nortel Networks
 EMail: dinmohan@hotmail.com
 Nabil Bitar (editor)
 Verizon
 60 Sylvan Road
 Waltham, MA  02145
 United States
 EMail: nabil.n.bitar@verizon.com
 Ali Sajassi (editor)
 Cisco
 170 West Tasman Drive
 San Jose, CA  95134
 United States
 EMail: sajassi@cisco.com
 Simon Delord
 Alcatel-Lucent
 215 Spring Street
 Melbourne
 Australia
 EMail: simon.delord@gmail.com
 Philippe Niger
 France Telecom
 2 av. Pierre Marzin
 22300 Lannion
 France
 EMail: philippe.niger@orange.com
 Ray Qiu
 Juniper
 1194 North Mathilda Avenue
 Sunnyvale, CA  94089
 United States
 EMail: rqiu@juniper.net

Mohan, et al. Standards Track [Page 23]

/data/webs/external/dokuwiki/data/pages/rfc/rfc7023.txt · Last modified: 2013/10/09 15:56 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki