Movatterモバイル変換

Internet Engineering Task Force (IETF)                   G. Swallow, Ed.Request for Comments: 6427                           Cisco Systems, Inc.Category: Standards Track                              A. Fulignoli, Ed.ISSN: 2070-1721                                                 Ericsson                                                       M. Vigoureux, Ed.                                                          Alcatel-Lucent                                                              S. Boutros                                                     Cisco Systems, Inc.                                                                 D. Ward                                                  Juniper Networks, Inc.                                                           November 2011MPLS Fault Management Operations, Administration, and Maintenance (OAM)Abstract   This document specifies Operations, Administration, and Maintenance   (OAM) messages to indicate service disruptive conditions for MPLS-   based transport network Label Switched Paths.  The notification   mechanism employs a generic method for a service disruptive condition   to be communicated to a Maintenance Entity Group End Point.  This   document defines an MPLS OAM channel, along with messages to   communicate various types of service disruptive conditions.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 inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6427.Swallow, et al.              Standards Track                    [Page 1]

RFC 6427                MPLS Fault Management OAM          November 2011Copyright Notice   Copyright (c) 2011 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.Table of Contents1. Introduction ....................................................31.1. Terminology ................................................41.2. Requirements Language ......................................52. MPLS Fault Management Messages ..................................52.1. MPLS Alarm Indication Signal ...............................52.1.1. MPLS Link Down Indication ...........................62.2. MPLS Lock Report ...........................................62.3. Propagation of MPLS Fault Messages .........................73. MPLS Fault Management Channel ...................................74. MPLS Fault Management Message Format ............................84.1. Fault Management Message TLVs ..............................94.1.1. Interface Identifier TLV ...........................104.1.2. Global Identifier ..................................105. Sending and Receiving Fault Management Messages ................105.1. Sending a Fault Management Message ........................105.2. Clearing a Fault Management Indication ....................115.3. Receiving a Fault Management Indication ...................116. Minimum Implementation Requirements ............................127. Security Considerations ........................................128. IANA Considerations ............................................138.1. Pseudowire Associated Channel Type ........................138.2. MPLS Fault OAM Message Type Registry ......................138.3. MPLS Fault OAM Flag Registry ..............................148.4. MPLS Fault OAM TLV Registry ...............................149. References .....................................................159.1. Normative References ......................................159.2. Informative References ....................................1510. Contributing Authors ..........................................16Swallow, et al.              Standards Track                    [Page 2]

RFC 6427                MPLS Fault Management OAM          November 20111.  Introduction   Proper operation of a transport network depends on the ability to   quickly identify faults and focus attention on the root cause of the   disruption.  This document defines MPLS Fault Management Operations,   Administration, and Maintenance (OAM) messages.  When a fault occurs   in a server (sub-)layer, Fault Management OAM messages are sent to   clients of that server so that alarms, which otherwise would be   generated by the subsequent disruption of the clients, may be   suppressed.  This prevents a storm of alarms and allows operations to   focus on the actual faulty elements of the network.   In traditional transport networks, circuits such as T1 lines are   typically provisioned on multiple switches.  When an event that   causes disruption occurs on any link or node along the path of such a   transport circuit, OAM indications are generated.  When received,   these indications may be used to suppress alarms and/or activate a   backup circuit.  The MPLS-based transport network provides mechanisms   equivalent to traditional transport circuits.  Therefore, a Fault   Management (FM) capability must be defined for MPLS.  This document   defines FM capabilities to meet the MPLS-TP requirements as described   inRFC 5654 [1], and the MPLS-TP Operations, Administration, and   Maintenance requirements as described inRFC 5860 [2].  These   mechanisms are intended to be applicable to other aspects of MPLS as   well.  However, applicability to other types of LSPs is beyond the   scope of this document.   Two broad classes of service disruptive conditions are identified.   1.  Fault: The inability of a function to perform a required action.       This does not include an inability due to preventive maintenance,       lack of external resources, or planned actions.   2.  Lock: an administrative status in which it is expected that only       test traffic, if any, and OAM (dedicated to the LSP) can be sent       on an LSP.   Within this document, a further term is defined: server-failure.  A   server-failure occurs when a fault condition or conditions have   persisted long enough to consider the required service function of   the server (sub-)layer to have terminated.  In the case of a   protected server, this would mean that the working facilities and any   protection facilities have all suffered faults of the required   duration.   This document specifies an MPLS OAM channel called an "MPLS-OAM Fault   Management (FM)" channel.  A single message format and a set of   procedures are defined to communicate service disruptive conditionsSwallow, et al.              Standards Track                    [Page 3]

RFC 6427                MPLS Fault Management OAM          November 2011   from the location where they occur to the end points of LSPs that are   affected by those conditions.  Multiple message types and flags are   used to indicate and qualify the particular condition.   Corresponding to the two classes of service disruptive conditions   listed above, two messages are defined to communicate the type of   condition.  These are known as:      Alarm Indication Signal (AIS)      Lock Report (LKR)1.1.  Terminology   ACH: Associated Channel Header   ACh: Associated Channel   CC: Continuity Check   FM: Fault Management   GAL: Generic Associated Channel Label   LOC: Loss of Continuity   LSP: Label Switched Path   MEP: Maintenance Entity Group End Point   MPLS: Multiprotocol Label Switching   MPLS-TP: MPLS Transport Profile   MS-PW: Multi-Segment Pseudowire   OAM: Operations, Administration, and Maintenance   PHP: Penultimate Hop Pop   PW: Pseudowire   TLV: Type, Length, ValueSwallow, et al.              Standards Track                    [Page 4]

RFC 6427                MPLS Fault Management OAM          November 20111.2.  Requirements Language   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 inRFC 2119 [3].2.  MPLS Fault Management Messages   This document defines two messages to indicate service disruptive   conditions, Alarm Indication Signal and Lock Report.  The semantics   of the individual messages are described in subsections below.  Fault   OAM messages are applicable to LSPs used in the MPLS Transport   Profile.  Such LSPs are bound to specific server layers based upon   static configuration or signaling in a client/server relationship.   Fault Management messages are carried in-band of the client LSP or   MS-PW by using the Associated Channel Header (ACH).  For LSPs other   than PWs, the ACH is identified by the Generic Associated Channel   Label (GAL) as defined inRFC 5586 [4].  To facilitate recognition   and delivery of Fault Management messages, the Fault Management   Channel is identified by a unique Associated Channel (ACh) code   point.   Fault OAM messages are generated by intermediate nodes where a client   LSP is switched.  When a server (sub-)layer, e.g., a link or   bidirectional LSP, used by the client LSP fails, the intermediate   node sends Fault Management messages downstream towards the end point   of the LSP.  The messages are sent to the client MEPs by inserting   them into the affected client LSPs in the direction downstream of the   fault location.  These messages are sent periodically until the   condition is cleared.2.1.  MPLS Alarm Indication Signal   The MPLS Alarm Indication Signal (AIS) message is generated in   response to detecting faults in the server (sub-)layer.  The AIS   message SHOULD be sent as soon as the condition is detected, but MAY   be delayed owing to processing in an implementation, and MAY be   suppressed if protection is achieved very rapidly.  For example, an   AIS message may be sent during a protection switching event and would   cease being sent (or cease being forwarded by the protection switch   selector) if the protection switch was successful in restoring the   link.  However, an implementation may instead wait to see if the   protection switch is successful prior to sending any AIS messages.Swallow, et al.              Standards Track                    [Page 5]

RFC 6427                MPLS Fault Management OAM          November 2011   The primary purpose of the AIS message is to suppress alarms in the   layer network above the level at which the fault occurs.  When the   Link Down Indication is set, the AIS message can be used to trigger   recovery mechanisms.2.1.1.  MPLS Link Down Indication   The Link Down Indication (LDI) is communicated by setting the L-Flag   to 1.  A node sets the L-Flag in the AIS message in response to   detecting a failure in the server layer.  A node MUST NOT set the   L-Flag until the fault has been determined to be a server-failure.  A   node MUST set the L-Flag if the fault has been determined to be a   server-failure.  For example, during a server layer protection   switching event, a node MUST NOT set the L-Flag.  However, if the   protection switch was unsuccessful in restoring the link within the   expected repair time, the node MUST set the L-Flag.   The setting of the L-Flag can be predetermined based on the   protection state.  For example, if a server layer is protected and   both the working and protection paths are available, the node should   send AIS with the L-Flag clear upon detecting a fault condition.  If   the server layer is unprotected, or the server layer is protected but   only the active path is available, the node should send AIS with the   L-Flag set upon detecting a loss of continuity (LOC) condition.  Note   again that the L-Flag is not set until a server-failure has been   declared.  Thus, if there is any hold-off timer associated with the   LOC, then the L-Flag is not set until that timer has expired.   The receipt of an AIS message with the L-Flag set MAY be treated as   the equivalent of LOC at the client layer.  The choice of treatment   is related to the rate at which the Continuity Check (CC) function is   running.  In a normal transport environment, CC is run at a high rate   in order to detect a failure within tens of milliseconds.  In such an   environment, the L-Flag MAY be ignored and the AIS message is used   solely for alarm suppression.   In more general MPLS environments, the CC function may be running at   a much slower rate.  In this environment, the Link Down Indication   enables faster switch-over upon a failure occurring along the client   LSP.2.2.  MPLS Lock Report   The MPLS Lock Report (LKR) message is generated when a server   (sub-)layer entity has been administratively locked.  Its purpose is   to communicate the locked condition to the client-layer entities.   When a server layer is administratively locked, it is not available   to carry client traffic.  The purpose of the LKR message is toSwallow, et al.              Standards Track                    [Page 6]

RFC 6427                MPLS Fault Management OAM          November 2011   suppress alarms in the layer network above the level at which the   administrative lock occurs and to allow the clients to differentiate   the lock condition from a fault condition.  While the primary purpose   of the LKR message is to suppress alarms, similar to AIS with the LDI   (L-Flag set), the receipt of an LKR message can be treated as the   equivalent of loss of continuity at the client layer.2.3.  Propagation of MPLS Fault Messages   MPLS-TP allows for a hierarchy of LSPs.  When the client MEP of an   LSP (that is also acting as a server layer) receives FM indications,   the following rules apply.  If the CC function is disabled for the   server LSP, a node SHOULD generate AIS messages toward any clients   when either the AIS or LKR indication is raised.  Note that the   L-Flag is not automatically propagated.  The rules ofSection 2.1.1   apply.  In particular, the L-Flag is not set until a server-failure   has been declared.3.  MPLS Fault Management Channel   The MPLS Fault Management channel is identified by the ACH as defined   inRFC 5586 [4] with the Associated Channel Type set to the MPLS   Fault Management (FM) code point = 0x0058.  The FM Channel does not   use ACh TLVs and MUST NOT include the ACh TLV header.  The ACH with   the FM ACh code point is shown below.       0                   1                   2                   3       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |0 0 0 1|Version|   Reserved    |       0x0058 FM Channel       |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                                                               ~      ~                  MPLS Fault Management Message                ~      ~                                                               |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+       Figure 1: ACH Indication of the MPLS Fault Management Channel   The first three fields are defined inRFC 5586 [4].   The Fault Management Channel is 0x0058.Swallow, et al.              Standards Track                    [Page 7]

RFC 6427                MPLS Fault Management OAM          November 20114.  MPLS Fault Management Message Format   The format of the Fault Management message is shown below.       0                   1                   2                   3       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      | Vers  | Resvd |   Msg Type    |     Flags     | Refresh Timer |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      | Total TLV Len |                                               ~      +-+-+-+-+-+-+-+-+              TLVs                             ~      ~                                                               |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                  Figure 2: MPLS Fault OAM Message Format   Version      The Version Number is currently 1.   Reserved      This field MUST be set to zero on transmission and ignored on      receipt.   Message Type      The Message Type indicates the type of condition as listed in the      table below.      Msg Type           Description      --------           -----------------------------         0               Reserved         1               Alarm Indication Signal (AIS)         2               Lock Report (LKR)   Flags      Two flags are defined.  The reserved flags in this field MUST be      set to zero on transmission and ignored on receipt.            +-+-+-+-+-+-+-+-+            | Reserved  |L|R|            +-+-+-+-+-+-+-+-+             Figure 3: FlagsSwallow, et al.              Standards Track                    [Page 8]

RFC 6427                MPLS Fault Management OAM          November 2011      L-Flag         Link Down Indication.  The L-Flag only has significance in the         AIS message.  For the LKR message, the L-Flag MUST be set to         zero and ignored on receipt.  SeeSection 2.1.1 for details on         setting this bit.      R-Flag         The R-Flag is clear to indicate the presence of an FM condition         and is set to one to indicate the removal of a previously sent         FM condition.   Refresh Timer      The maximum time between successive FM messages specified in      seconds.  The range is 1 to 20.  The value 0 is not permitted.   Total TLV Length      The total length in bytes of all included TLVs.4.1.  Fault Management Message TLVs   TLVs are used in Fault Management messages to carry information that   may not pertain to all messages as well as to allow for   extensibility.  The TLVs currently defined are the IF_ID and the   Global_ID.   TLVs have the following format:       0                   1                   2                   3       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |     Type      |    Length     |                               |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               .      |                                                               .      .                             Value                             .      .                                                               |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                        Figure 4: Fault TLV Format   Type      Encodes how the Value field is to be interpreted.Swallow, et al.              Standards Track                    [Page 9]

RFC 6427                MPLS Fault Management OAM          November 2011   Length      Specifies the length of the Value field in octets.   Value      Octet string of Length octets that encodes information to be      interpreted as specified by the Type field.4.1.1.  Interface Identifier TLV   The Interface Identifier (IF_ID) TLV carries the IF_ID as defined inRFC 6370 [5].  The Type is 1.  The length is 0x8.       0                   1                   2                   3       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                    MPLS-TP Node Identifier                    |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                    MPLS-TP Interface Number                   |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                 Figure 5: Interface Identifier TLV Format4.1.2.  Global Identifier   The Global Identifier (Global_ID) TLV carries the Global_ID as   defined inRFC 6370 [5].  The Type is 2.  The length is 0x4.       0                   1                   2                   3       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                   MPLS-TP Global Identifier                   |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                  Figure 6: Global Identifier TLV Format5.  Sending and Receiving Fault Management Messages5.1.  Sending a Fault Management Message   Service disruptive conditions are indicated by sending FM messages.   The message type is set to the value corresponding to the condition.   The Refresh Timer is set to the maximum time between successive FM   messages.  This value MUST NOT be changed on successive FM messages   reporting the same incident.  If the optional clearing procedures are   not used, then the default value is one second.  Otherwise, the   default value is 20 seconds.Swallow, et al.              Standards Track                   [Page 10]

RFC 6427                MPLS Fault Management OAM          November 2011   A Global_ID MAY be included.  If the R-Flag clearing procedures are   to be used, the IF_ID TLV MUST be included.  Otherwise, the IF_ID TLV   MAY be included.   The message is then sent.  Assuming the condition persists, the   message MUST be retransmitted two more times at an interval of one   second.  Further retransmissions are made according to the value of   the Refresh Timer.  Retransmissions continue until the condition is   cleared.5.2.  Clearing a Fault Management Indication   When a fault is cleared, a node MUST cease sending the associated FM   messages.  Ceasing to send FM messages will clear the indication   after 3.5 times the Refresh Timer.  To clear an indication more   quickly, the following procedure is used.  The R-Flag of the FM   message is set to one.  Other fields of the FM message SHOULD NOT be   modified.  The message is sent immediately and then retransmitted two   more times at an interval of one second.  Note, however, if another   fault occurs, the node MUST cease these retransmissions and generate   new FM messages for the new fault.5.3.  Receiving a Fault Management Indication   When an FM message is received, a MEP examines it to ensure that it   is well formed.  If the message type is reserved or unknown, the   message is ignored.  If the version number is unknown, the message is   ignored.   If the R-Flag is set to zero, the MEP checks to see if a condition   matching the message type exists.  If it does not, the condition   specific to the message type is entered.  An Expiration timer is set   to 3.5 times the Refresh Timer.  If the message type matches an   existing condition, the message is considered a refresh and the   Expiration timer is reset.  In both cases, if an IF_ID TLV is   present, it is recorded.   If the R-Flag is set to one, the MEP checks to see if a condition   matching the message type and IF_ID exists.  If it does, that   condition is cleared.  Otherwise, the message is ignored.   If the Expiration timer expires, the condition is cleared.Swallow, et al.              Standards Track                   [Page 11]

RFC 6427                MPLS Fault Management OAM          November 20116.  Minimum Implementation Requirements   At a minimum, an implementation MUST support the following:   1.  Sending AIS and LKR messages at a rate of one per second.   2.  Support of setting the L-Flag to indicate a server-failure.   3.  Receiving AIS and LKR messages with any allowed Refresh Timer       value.   The following items are OPTIONAL to implement.   1.  Sending AIS and LKR messages with values of the Refresh Timer       other than one second.   2.  Support of receiving the L-Flag.   3.  Support of setting the R-Flag to a value other than zero.   4.  Support of receiving the R-Flag.   5.  All TLVs.7.  Security Considerations   MPLS-TP is a subset of MPLS and so builds upon many of the aspects of   the security model of MPLS.  MPLS networks make the assumption that   it is very hard to inject traffic into a network, and equally hard to   cause traffic to be directed outside the network.  The control-plane   protocols utilize hop-by-hop security and assume a "chain-of-trust"   model such that end-to-end control-plane security is not used.  For   more information on the generic aspects of MPLS security, seeRFC5920 [8].   This document describes a protocol carried in the G-ACh (RFC 5586   [4]) and so is dependent on the security of the G-ACh itself.  The   G-ACh is a generalization of the Associated Channel defined inRFC4385 [6].  Thus, this document relies heavily on the security   mechanisms provided for the Associated Channel as described in those   two documents.   A specific concern for the G-ACh is that is can be used to provide a   covert channel.  This problem is wider than the scope of this   document and does not need to be addressed here, but it should be   noted that the channel provides end-to-end connectivity and SHOULDSwallow, et al.              Standards Track                   [Page 12]

RFC 6427                MPLS Fault Management OAM          November 2011   NOT be policed by transit nodes.  Thus, there is no simple way of   preventing any traffic being carried in the G-ACh between consenting   nodes.   A good discussion of the data-plane security of an Associated Channel   may be found inRFC 5085 [9].  That document also describes some   mitigation techniques.   It should be noted that the G-ACh is essentially connection-oriented,   so injection or modification of control messages specified in this   document requires the subversion of a transit node.  Such subversion   is generally considered hard to protect against in MPLS networks, and   impossible to protect against at the protocol level.  Management-   level techniques are more appropriate.   Spurious fault OAM messages form a vector for a denial-of-service   attack.  However, since these messages are carried in a control   channel, except for one case discussed below, one would have to gain   access to a node providing the service in order to effect such an   attack.  Since transport networks are usually operated as a walled   garden, such threats are less likely.   If external MPLS traffic is mapped to an LSP via a PHP forwarding   operation, it is possible to insert a GAL followed by a fault OAM   message.  In such a situation, an operator SHOULD protect against   this attack by filtering any fault OAM messages with the GAL at the   top of the label stack.8.  IANA Considerations8.1.  Pseudowire Associated Channel Type   Fault OAM requires a unique Associated Channel Type that has been   assigned by IANA from the Pseudowire Associated Channel Types   registry.   Registry:   Value        Description              TLV Follows  Reference   -----------  -----------------------  -----------  ---------   0x0058       Fault OAM                No           (This Document)8.2.  MPLS Fault OAM Message Type Registry   This section details the "MPLS Fault OAM Message Type Registry", a   new sub-registry of the "Multiprotocol Label Switching (MPLS)   Operations, Administration, and Management (OAM) Parameters"   registry.  The Type space is divided into assignment ranges; theSwallow, et al.              Standards Track                   [Page 13]

RFC 6427                MPLS Fault Management OAM          November 2011   following terms are used in describing the procedures by which IANA   allocates values (as defined inRFC 5226 [7]): "Standards Action" and   "Experimental Use".   MPLS Fault OAM Message Types take values in the range 0-255.   Assignments in the range 0-251 are via Standards Action; values in   the range 252-255 are for Experimental Use and MUST NOT be allocated.   Message Types defined in this document are:      Msg Type           Description      --------           -----------------------------         0               Reserved (not available for allocation)         1               Alarm Indication Signal (AIS)         2               Lock Report (LKR)8.3.  MPLS Fault OAM Flag Registry   This section details the "MPLS Fault OAM Flag Registry", a new sub-   registry of the "Multiprotocol Label Switching (MPLS) Operations,   Administration, and Management (OAM) Parameters" registry.  The Flag   space ranges from 0-7.  All flags are allocated by "Standards Action"   (as defined inRFC 5226 [7]).   Flags defined in this document are:      Bit        Hex Value         Description      ---        ---------         -----------      0-5                          Unassigned       6            0x2            L-Flag       7            0x1            R-Flag8.4.  MPLS Fault OAM TLV Registry   This sections details the "MPLS Fault OAM TLV Registry", a new sub-   registry of the "Multiprotocol Label Switching (MPLS) Operations,   Administration, and Management (OAM) Parameters" registry.  The Type   space is divided into assignment ranges; the following terms are used   in describing the procedures by which IANA allocates values (as   defined inRFC 5226 [7]): "Standards Action", "Specification   Required", and "Experimental Use".   MPLS Fault OAM TLVs take values in the range 0-255.  Assignments in   the range 0-191 are via Standards Action; assignments in the range   192-247 are made via "Specification Required"; values in the range   248-255 are for Experimental Use and MUST NOT be allocated.Swallow, et al.              Standards Track                   [Page 14]

RFC 6427                MPLS Fault Management OAM          November 2011   TLVs defined in this document are:      Value    TLV Name      -----    -------          0    Reserved (not available for allocation)          1    Interface Identifier TLV          2    Global Identifier9.  References9.1.  Normative References   [1] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,       Sprecher, N., and S. Ueno, "Requirements of an MPLS Transport       Profile",RFC 5654, September 2009.   [2] Vigoureux, M., Ed., Ward, D., Ed., and M. Betts, Ed.,       "Requirements for Operations, Administration, and Maintenance       (OAM) in MPLS Transport Networks",RFC 5860, May 2010.   [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement       Levels",BCP 14,RFC 2119, March 1997.   [4] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., "MPLS       Generic Associated Channel",RFC 5586, June 2009.   [5] Bocci, M., Swallow, G., and E. Gray, "MPLS Transport Profile       (MPLS-TP) Identifiers",RFC 6370, September 2011.   [6] Bryant, S., Swallow, G., Martini, L., and D. McPherson,       "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use       over an MPLS PSN",RFC 4385, February 2006.   [7] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA       Considerations Section in RFCs",BCP 26,RFC 5226, May 2008.9.2.  Informative References   [8] Fang, L., Ed., "Security Framework for MPLS and GMPLS Networks",RFC 5920, July 2010.   [9] Nadeau, T., Ed., and C. Pignataro, Ed., "Pseudowire Virtual       Circuit Connectivity Verification (VCCV): A Control Channel for       Pseudowires",RFC 5085, December 2007.Swallow, et al.              Standards Track                   [Page 15]

RFC 6427                MPLS Fault Management OAM          November 201110.  Contributing Authors   Stewart Bryant   Cisco Systems, Inc.   250, Longwater   Green Park, Reading  RG2 6GB   UK   EMail: stbryant@cisco.com   Siva Sivabalan   Cisco Systems, Inc.   2000 Innovation Drive   Kanata, Ontario  K2K 3E8   Canada   EMail: msiva@cisco.comSwallow, et al.              Standards Track                   [Page 16]

RFC 6427                MPLS Fault Management OAM          November 2011Authors' Addresses   George Swallow (editor)   Cisco Systems, Inc.   300 Beaver Brook Road   Boxborough, Massachusetts  01719   United States   EMail: swallow@cisco.com   Annamaria Fulignoli (editor)   Ericsson   Via Moruzzi   Pisa  56100   Italy   EMail: annamaria.fulignoli@ericsson.com   Martin Vigoureux (editor)   Alcatel-Lucent   Route de Villejust   Nozay  91620   France   EMail: martin.vigoureux@alcatel-lucent.com   Sami Boutros   Cisco Systems, Inc.   3750 Cisco Way   San Jose, California  95134   USA   EMail: sboutros@cisco.com   David Ward   Juniper Networks, Inc.   EMail: dward@juniper.netSwallow, et al.              Standards Track                   [Page 17]