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RFC 4221 - Multiprotocol Label Switching (MPLS) Management Overv


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Network Working Group                                          T. Nadeau
Request for Comments: 4221                           Cisco Systems, Inc.
Category: Informational                                    C. Srinivasan
                                                          Bloomberg L.P.
                                                               A. Farrel
                                                      Old Dog Consulting
                                                           November 2005

        Multiprotocol Label Switching (MPLS) Management Overview

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   A range of Management Information Base (MIB) modules has been
   developed to help model and manage the various aspects of
   Multiprotocol Label Switching (MPLS) networks.  These MIB modules are
   defined in separate documents that focus on the specific areas of
   responsibility of the modules that they describe.

   This document describes the management architecture for MPLS and
   indicates the interrelationships between the different MIB modules
   used for MPLS network management.

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................3
   3. The SNMP Management Framework ...................................3
   4. An Introduction to the MPLS Working Group MIB Modules ...........4
      4.1. Structure of the MPLS MIB OID Tree .........................5
      4.2. MPLS-TC-STD-MIB ............................................5
      4.3. MPLS-LSR-STD-MIB ...........................................5
      4.4. MPLS-LDP-STD-MIB ...........................................6
      4.5. MPLS-LDP-GENERIC-STD-MIB ...................................6
      4.6. MPLS-LDP-ATM-STD-MIB .......................................6
      4.7. MPLS-LDP-FRAME-RELAY-STD-MIB ...............................7
      4.8. MPLS-TE-STD-MIB ............................................7
      4.9. MPLS-FTN-STD-MIB ...........................................7

      4.10. TE-LINK-STD-MIB ...........................................7
      4.11. MIB Module Interdependencies ..............................8
      4.12. Dependencies on External MIB Modules ......................9
   5. Tables, Scalars, and Notifications in MPLS-LSR-STD-MIB .........10
      5.1. Tables ....................................................10
      5.2. Scalars ...................................................10
      5.3. Indexing ..................................................11
      5.4. Notifications .............................................12
      5.5. Dependencies between MIB Module Tables ....................12
   6. Tables, Scalars, and Notifications in the LDP MIB ..............13
      6.1. MIB Modules ...............................................13
      6.2. Tables ....................................................14
      6.3. Scalars ...................................................15
      6.4. Notifications .............................................15
      6.5. Dependencies between MIB Module Tables ....................15
   7. Tables, Scalars, and Notifications in MPLS-TE-STD-MIB ..........16
      7.1. Tables ....................................................16
      7.2. Scalars ...................................................17
      7.3. Notifications .............................................18
      7.4. Dependencies between MIB Module Tables ....................18
   8. Tables, Scalars, and Notifications in MPLS-FTN-STD-MIB .........18
      8.1. Tables ....................................................18
      8.2. Scalars ...................................................19
      8.3. Notifications .............................................19
      8.4. Dependencies between MIB Module Tables ....................19
   9. Tables and Objects in TE-LINK-STD-MIB ..........................19
      9.1. Tables ....................................................19
      9.2. Scalars ...................................................20
      9.3. Notifications .............................................20
      9.4. Dependencies between MIB Module Tables ....................20
   10. Table Dependencies between MPLS MIB Modules ...................21
   11. A Note on Interfaces ..........................................21
      11.1. MPLS Tunnels as Interfaces ...............................21
      11.2. Application of the Interfaces Group to TE Links ..........22
      11.3. References to Interface MIB Objects from MPLS MIB
            Modules ..................................................23
   12. Management Options ............................................24
   13. Related IETF MIB Modules ......................................25
      13.1. PWE3 Working Group MIB Modules ...........................26
      13.2. PPVPN Working Group MIB Modules ..........................26
           13.2.1. PPVPN-MPLS-VPN-STD-MIB ............................26
      13.3. CCAMP Working Group MIB Modules ..........................26
   14. Traffic Engineering Working Group TE MIB ......................27
      14.1. Choosing between TE MIB Modules ..........................27
   15. Security Considerations .......................................28
   16. Acknowledgements ..............................................28
   17. Normative References ..........................................29
   18. Informative References ........................................30

1.  Introduction

   This document describes the Management Architecture for Multi-
   Protocol Label Switching (MPLS) [RFC3031].  In particular, it
   describes how the managed objects defined in various MPLS-related
   Management Information Base (MIB) documents model different aspects
   of MPLS.  Furthermore, this document explains the interactions and
   dependencies between each of these MIB modules.

   For additional information, this document also includes a brief note
   on MIB modules produced by the Pseudo Wire Emulation Edge to Edge
   (PWE3), Provider Provisioned Virtual Private Network (PPVPN), Common
   Control and Measurement Plane (CCAMP), and Internet Traffic
   Engineering (TEWG) working groups.

   The document begins with a brief outline of the SNMP framework.  This
   is not intended to be a complete reference on SNMP, but is provided
   to give context to the rest of the document and to indicate reference
   material for readers that need to know more about SNMP.

   This document does not propose any additions to the MPLS MIB
   framework, nor define any standards for the Internet community.  It
   is an informational document.  In all cases, the reader is advised to
   turn to the document that defines the MIB module in question for
   further information.

   Comments should be made directly to the MPLS mailing list at
   mpls@uu.net.

2.  Terminology

   This document uses terminology from the MPLS architecture document
   [RFC3031] and the following MPLS related MIB modules: MPLS TC MIB
   [TCMIB], MPLS LSR MIB [LSRMIB], MPLS TE MIB [TEMIB], MPLS LDP MIB
   [LDPMIB], MPLS FTN MIB [FTNMIB], TE LINK MIB [TELMIB], and PPVPN MPLS
   VPN MIB [VPNMIB].

   Throughout this document hyphenated MIB names (such as MPLS-TE-STD-
   MIB) should be taken to refer to specific MIB modules.  Non-
   hyphenated MIB names (such as MPLS LDP MIB) indicate MIB documents.

3.  The SNMP Management Framework

   For a detailed overview of the documents that describe the current
   Internet-Standard Management Framework, please refer to section 7 of
   RFC 3410 [RFC3410].

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  MIB objects are generally
   accessed through the Simple Network Management Protocol (SNMP).
   Objects in the MIB are defined using the mechanisms defined in the
   Structure of Management Information (SMI).  This document specifies a
   MIB module that is compliant to the SMIv2, which is described in STD
   58, RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC
   2580 [RFC2580].

4.  An Introduction to the MPLS Working Group MIB Modules

   This section addresses the MIB documents produced by the MPLS working
   group, namely MPLS TC MIB, MPLS LSR MIB, MPLS TE MIB, MPLS LDP MIB,
   MPLS FTN MIB, and TE LINK MIB.  The rest of this section briefly
   describes the following:

   -  the MPLS Object Identifier (OID) tree structure and the position
      of different MPLS related MIB modules on this tree;

   -  the purpose of each of the MIB modules within the MIB documents,
      what it can be used for, and how it relates to the other MIB
      modules.

   Note that each MIB document contains one or more compliance
   statements for the modules and objects that it defines.  Therefore,
   the support for the different MIB modules and objects is beyond the
   scope of this document, although some recommendations are included in
   the sections that follow.

4.1.  Structure of the MPLS MIB OID Tree

   The MPLS MIB OID tree has the following structure.

      transmission -- RFC 2578 [RFC2578]
        |
        +- mplsStdMIB -- MPLS-TC-STD-MIB
        |    |
        |    +- mplsTCStdMIB -- MPLS-TC-STD-MIB
        |    |
        |    +- mplsLsrStdMIB -- MPLS-LSR-STD-MIB
        |    |
        |    +- mplsTeStdMIB -- MPLS-TE-STD-MIB
        |    |
        |    +- mplsLdpStdMIB -- MPLS-LDP-STD-MIB
        |    |
        |    +- mplsLdpAtmStdMIB -- MPLS-LDP-ATM-STD-MIB
        |    |
        |    +- mplsLdpFrameRelayStdMIB -- MPLS-LDP-FRAME-RELAY-STD-MIB
        |    |
        |    +- mplsLdpGenericStdMIB -- MPLS-LDP-GENERIC-STD-MIB
        |    |
        |    +- mplsFTNStdMIB -- MPLS-FTN-STD-MIB
        |
        +- teLinkStdMIB -- TE-LINK-STD-MIB

   Note: The OIDs for MIB modules are assigned and managed by IANA.
   They can be found in the referenced MIB documents.

4.2.  MPLS-TC-STD-MIB

   MPLS-TC-STD-MIB defines textual conventions [RFC2579] that may be
   common to MPLS-related MIB modules.  These conventions allow multiple
   MIB modules to use the same syntax and format for a concept that is
   shared between the MIB modules.

   For example, labels are a central part of MPLS and need to be
   presented in many of the MIB modules.  The textual convention for
   representing an MPLS label is defined in MPLS-TC-STD-MIB.

   All of the other MPLS MIB modules import textual conventions from
   this MIB module.

4.3.  MPLS-LSR-STD-MIB

   MPLS-LSR-STD-MIB describes managed objects for modeling an MPLS Label
   Switching Router (LSR).  This puts it at the heart of the management
   architecture for MPLS.

   This MIB module is used to model and manage the basic label switching
   behavior of an MPLS LSR.  It represents the label forwarding
   information base (LFIB) of the LSR and provides a view of the LSPs
   that are being switched by the LSR in question.

   Since basic MPLS label switching is common to all MPLS applications,
   this MIB module is referenced by many of the other MPLS MIB modules.

   In general, MPLS-LSR-STD-MIB provides a model of incoming labels on
   MPLS-enabled interfaces being mapped to outgoing labels on MPLS-
   enabled interfaces via a conceptual object called an MPLS cross-
   connect.  MPLS cross-connect entries and their properties are
   represented in MPLS-LSR-STD-MIB and are typically referenced by other
   MIB modules in order to refer to the underlying MPLS LSP.

   For example, MPLS-TE-STD-MIB models traffic-engineered tunnels.
   These tunnels map to one or more underlying MPLS LSPs.  MPLS-TE-STD-
   MIB refers to the underlying LSPs by pointing to cross-connect
   entries in MPLS-LSR-STD-MIB.

4.4.  MPLS-LDP-STD-MIB

   MPLS-LDP-STD-MIB describes managed objects used to model and manage
   the MPLS Label Distribution Protocol (LDP) [RFC3036].  LDP is one of
   the MPLS protocols used to distribute labels and establish LSPs.

   This MIB module contains objects common to all LDP implementations.
   For an LDP implementation that provides standard MIB support, this
   MIB module provides the core set of objects that are needed, along
   with one or more of the other LDP MIB modules from the following
   sections.

4.5.  MPLS-LDP-GENERIC-STD-MIB

   This MIB module provides objects for managing the LDP Per Platform
   Label Space and is typically implemented along with the MPLS-LDP-
   STD-MIB module.  This MIB Module contains tables for configuring MPLS
   Generic Label Ranges.  Although the LDP Specification does not
   provide a way to configure Label Ranges for Generic Labels, the MIB
   module does provide a way to reserve a range of generic labels
   because the working group thought this was useful.

4.6.  MPLS-LDP-ATM-STD-MIB

   This MIB module is typically supported along with MPLS-LDP-STD-MIB by
   LDP implementations if LDP uses ATM as the Layer 2 medium.  Tables in
   this MIB module allow for configuring LDP to use ATM.

4.7.  MPLS-LDP-FRAME-RELAY-STD-MIB

   This MIB module is typically supported along with MPLS-LDP-STD-MIB by
   LDP implementations if LDP uses Frame Relay as the Layer 2 medium.
   Tables in this MIB module allow for configuration of LDP to use Frame
   Relay.

4.8.  MPLS-TE-STD-MIB

   MPLS-TE-STD-MIB describes managed objects that are used to model and
   manage MPLS Traffic Engineered (TE) Tunnels.

   This MIB module is based on a table that represents TE tunnels that
   either originate from, traverse via, or terminate on the LSR in
   question.  The MIB module provides configuration and statistics
   objects needed for TE tunnels.

4.9.  MPLS-FTN-STD-MIB

   MPLS-FTN-STD-MIB describes managed objects that are used to model and
   manage the MPLS FEC-to-NHLFE (FTN) mappings that take place at an
   ingress Label Edge Router (LER).

   An LER is an LSR placed at the edge of an MPLS domain, and it passes
   traffic into and out of the MPLS domain.  An ingress LER is
   responsible for classifying data and assigning it to a suitable LSP
   or tunnel.

   This classification is done using Forwarding Equivalence Classes
   (FECs) that define the common attributes of data (usually packets)
   that will be treated in the same way.  Once data has been classified,
   it can be handed off to an LSP or tunnel through the Next Hop Label
   Forwarding Entry (NHLFE).

   In the case of an IP-to-MPLS mapping, the FEC objects describe IP
   6-tuples that represent source and destination address ranges, source
   and destination port ranges, the IPv4 Protocol field or IPv6 next-
   header field, and the DiffServ Code Point (DSCP).

4.10.  TE-LINK-STD-MIB

   TE-LINK-STD-MIB describes managed objects that are used to model and
   manage TE links, including bundled links, in an MPLS network.

   The TE link feature is designed to aggregate one or more similar data
   channels or TE links between a pair of LSRs.  A TE link is a sub-
   interface capable of carrying traffic-engineered MPLS traffic.

   A bundled link is a sub-interface that bonds the traffic of a group
   of one or more TE links.

4.11.  MIB Module Interdependencies

   This section provides an overview of the relationship between the
   MPLS MIB modules described above.  More details of these
   relationships are given below after the MIB modules have been
   discussed in more detail.

   The arrows in the following diagram show a 'depends on' relationship.
   A relationship "MIB module A depends on MIB module B" means that MIB
   module A uses an object, object identifier, or textual convention
   defined in MIB module B, or that MIB module A contains a pointer
   (index or RowPointer) to an object in MIB module B.

   +-------> MPLS-TC-STD-MIB
   |            ^
   |            |
   |         MPLS-LSR-STD-MIB <------------------+
   |                                             |
   +<----------------------- MPLS-LDP-STD-MIB -->+
   |                                    ^        |
   |                                    |        |
   +<-- MPLS-LDP-GENERIC-STD-MIB ------>+        |
   |                                    |        |
   +<-- MPLS-LDP-ATM-STD-MIB ---------->+        |
   |                                    |        |
   +<-- MPLS-LDP-FRAME-RELAY-STD-MIB -->+        |
   |                                             |
   +<------- MPLS-TE-STD-MIB ------------------->+
   |            ^                                |
   |            |                                |
   +<------- MPLS-FTN-STD-MIB ------------------>+

   Thus:

   -  All the MPLS MIB modules depend on MPLS-TC-STD-MIB.

   -  MPLS-LDP-STD-MIB, MPLS-TE-STD-MIB, and MPLS-FTN-STD-MIB contain
      references to objects in MPLS-LSR-STD-MIB.

   -  MPLS-LDP-GENERIC-STD-MIB, MPLS-LDP-ATM-STD-MIB, and MPLS-LDP-
      FRAME-RELAY-STD-MIB contain references to objects in MPLS-LDP-
      STD-MIB.

   -  MPLS-FTN-STD-MIB contains references to objects in MPLS-TE-STD-
      MIB.

   Note that there is a textual convention (MplsIndexType) defined in
   MPLS-LSR-STD-MIB that is imported by MPLS-LDP-STD-MIB.

4.12.  Dependencies on External MIB Modules

   With the exception of MPLS-TC-STD-MIB, all the MPLS MIB modules have
   dependencies on the Interfaces MIB [RFC2863].  MPLS-FTN-STD-MIB
   references IP-capable interfaces on which received traffic is to be
   classified using indexes in the Interface Table (ifTable) of IF-MIB
   [RFC2863].  The other MPLS MIB modules reference MPLS-capable
   interfaces in ifTable.

   The Interfaces Group of IF-MIB [RFC2863] defines generic managed
   objects for managing interfaces.  The MPLS MIB modules contain
   media-specific extensions to the Interfaces Group for managing MPLS
   interfaces.

   The MPLS MIB modules assume the interpretation of the Interfaces
   Group to be in accordance with [RFC2863], which states that ifTable
   contains information on the managed resource's interfaces and that
   each sub-layer below the internetwork layer of a network interface is
   considered an interface.  Thus, the MPLS interface is represented as
   an entry in ifTable.

   The interrelation of entries in ifTable is defined by the Interfaces
   Stack Group defined in [RFC2863].

   Additionally, MPLS-LDP-ATM-STD-MIB imports the textual convention
   AtmVpIdentifier from ATM-TC-MIB to represent an ATM virtual path
   identifier, whereas MPLS-LDP-FRAME-RELAY-STD-MIB imports the textual
   convention DLCI from FRAME-RELAY-DTE-MIB to represent a Data Link
   Channel identifier.

   MPLS-LDP-STD-MIB imports the textual conventions IndexInteger and
   IndexIntegerNextFree from [RFC3289], and MPLS-TE-STD-MIB imports
   IndexIntegerNextFree.  IndexInteger provides a standard arbitrary
   index, whereas IndexIntegerNextFree is used by a management agent
   that needs to select an appropriate value for an arbitrary index.

   Finally, all of the MIB modules import standard textual conventions
   such as integers, strings, timestamps, etc., from the MIB modules in
   which they are defined.  This is business as usual for a MIB module
   and is not discussed further in this document.

5.  Tables, Scalars, and Notifications in MPLS-LSR-STD-MIB

5.1.  Tables

   MPLS-LSR-STD-MIB contains the following tables.

   -  The interface configuration table (mplsInterfaceTable) is used for
      enabling MPLS on MPLS-capable interfaces.

   -  The in-segment (mplsInSegmentTable) and out-segment
      (mplsOutSegmentTable) tables are used to configure and monitor LSP
      segments carrying data into and out of the LSR, respectively.

   -  The in-segment mapping table (mplsInSegmentMapTable) provides a
      look-up table that enables the discovery of an in-segment in
      mplsInSegmentTable from the known incoming interface and incoming
      label.

   -  The cross-connect table (mplsXCTable) is used to associate in and
      out segments in order to form a cross-connect (i.e., to represent
      an LSP transiting the LSR).

   -  The label stack table (mplsLabelStackTable) allows the
      specification of multi-label stacks to be imposed on a given LSP
      at this LSR.

   -  The MPLS in-segment (mplsInSegmentPerfTable) and out-segment
      (mplsOutSegmentPerfTable) performance tables contain objects to
      measure the performance of LSPs.

   -  The MPLS interface performance table (mplsInterfacePerfTable) has
      objects to measure MPLS performance on a per-interface basis.

5.2.  Scalars

   Where tables in the MIB module have arbitrary indexes, scalars are
   provided to supply the next available index.  This applies to
   mplsInSegmentTable, mplsOutSegmentTable, mplsXCTable, and
   mplsLabelStackTable, but see the section on indexing, below.

   mplsMaxLabelStackDepth defines the maximum size of a imposed label
   stack supported at this LSR (and not, as the description in MPLS-
   LSR-STD-MIB states, the maximum label stack depth supported by the
   LSR).

   mplsXCNotificationsEnable is used to enable and disable notifications
   from MPLS-LSR-STD-MIB.

5.3.  Indexing

   Note that the indexing used by the tables in MPLS-LSR-STD-MIB is
   unusual.  A specific textual convention, MplsIndexType, is defined in
   the MIB module and is used as the type for indexes to
   mplsInSegmentTable, mplsOutSegmentTable, mplsXCTable, and
   mplsLabelStackTable.  The textual convention is defined as an octet
   string of between one and twenty-four octets, inclusive.

   Although this convention can be used to map simple integers and so
   preserve the normal indexing techniques, it may also be used to
   encode more complex indexing rules that may be useful to
   implementations that subdivide their label spaces according to
   physical or implementation constraints (such as placing the
   responsibility for a subset of labels with a line card).

   Note that it would be unusual, but not impossible, to make
   sophisticated use of these indexes in a write-access MIB since the
   'next' index value would be hard to determine.  Thus, non-simple
   values are likely only to be used in read-only MIBs in which the
   indexes are generated as a result of signaling protocol
   implementations or other configuration means.  The formatting and
   interpretation of non-simple indexes is out of the scope of the MIB
   module definition and is expected to be part of the manageability
   statement for a particular device.  When the formatting is not known
   by an agent, it should treat the index as a plain octet string
   containing an integer of between one and twenty-four octets.

   As described in the previous section, scalars are provided to allow
   agents to discover a suitable value to use as an index when creating
   a new row in one of these tables.  These scalars all use a second
   textual convention, MplsIndexNextType, also defined within MPLS-LSR-
   STD-MIB.  This textual convention allows the 'null string', (that is,
   a string of length one octet with value 0x00).  The null string is
   used to indicate that either write access is not supported or no more
   indexes are currently available.

   Note that the usage of the nextIndex scalars is such that at any time
   a scalar supplies a value that is currently unused as an index to the
   specific table.  In order to avoid lacunae in the indexing of a table
   under normal usage, implementations are recommended to change the
   value in an nextIndex scalar only when the index is used (that is,
   when a row is created) and not when the nextIndex scalar is read.  In
   a 'busy' table, this may result in row creation attempts failing and
   agents having to re-read the scalar before making a second row
   creation attempt.  The desire to avoid this issue is in opposition to
   the desire to avoid lacunae.

5.4.  Notifications

   MPLS-LSR-STD-MIB can issue two notifications (if notifications are
   enabled).

   -  mplsXCUp reports when a cross-connect becomes active.

   -  mplsXCDown reports when a cross-connect becomes
      inactive.

5.5.  Dependencies between MIB Module Tables

   The tables in MPLS-LSR-STD-MIB are related as shown on the diagram
   below.  The arrows indicate a reference from one table to another.

   Note that the various MIB tables contain two instances of pointers to
   external tables that are not currently defined.  Entries in an
   external Traffic Parameters Table (external_Traffic_Table) are
   pointed to using RowPointers from the mplsInSegmentTable
   (mplsInSegmentTrafficParamPtr) and from the mplsOutSegmentTable
   (mplsOutSegmentTrafficParamPtr) to allow representation of the
   traffic parameters for the MPLS segment.  Alternatively, the pointers
   may indicate an entry in the Tunnel Resource Table
   (mplsTunnelResourceTable) in MPLS-TE-STD-MIB.  Similarly, an external
   label table may be used to store label values if, for some reason,
   they are not stored in place within the LSR MIB tables.  This might
   occur if extra per-label space information needs to be stored, and it
   paves the way for GMPLS where labels cannot always be stored in a
   32-bit value.  RowPointers are used from the mplsInSegmentTable
   (mplsInSegmentLabelPtr), the mplsOutSegmentTable
   (mplsOutSegmentTopLabelPtr), and from the mplsLabelStackTable
   (mplsLabelStackLabelPtr).

                      mplsInterfacePerfTable
                                 ^
                                 |
                                 V
                        mplsInterfaceTable
                         ^              ^
   mplsInSegmentMapTable |              | mplsLabelStackTable
             |           |              |           ^     |
             |      +----+              +----+      |     |
             |      |                        |      |     |
             |      | external_Traffic_Table |      |     |
             |      |   ^                ^   |      |     |
             V      |   |                |   |      |     |
            mplsInSegmentTable        mplsOutSegmentTable |
             |  ^   ^                        ^   ^     |  |
             |  |   |                        |   |     |  V
      +------+  |   +----> mplsXCTable  <----+   |     +--+
      |         V                                V        |
      | mplsInSegmentPerfTable    mplsOutSegmentPerfTable |
      |                                                   |
      +--------------> external_Label_Table <-------------+

6. Tables, Scalars, and Notifications in the LDP MIB

6.1.  MIB Modules

   The MIB document for LDP contains four MIB modules.  This structure
   makes it easier for an implementation to select only those modules
   that are relevant to it.  The MIB Modules are MPLS-LDP-STD-MIB,
   MPLS-LDP-GENERIC-STD-MIB, MPLS-LDP-ATM-STD-MIB, and MPLS-LDP-FRAME-
   RELAY-STD-MIB.

   MPLS-LDP-STD-MIB defines objects that are specific to LDP without any
   Layer 2 objects.  MPLS-LDP-GENERIC-STD-MIB defines Layer 2 Per
   Platform Label Space objects for use with MPLS-LDP-STD-MIB and for
   use on Ethernet.  MPLS-LDP-ATM-STD-MIB defines Layer 2 Asynchronous
   Transfer Mode (ATM) objects for use with MPLS-LDP-STD-MIB.  MPLS-
   LDP-FRAME-RELAY-STD-MIB defines Layer 2 FRAME-RELAY objects for use
   with MPLS-LDP-STD-MIB.

   The MPLS-LDP-STD-MIB module provides the core support and is
   typically supported along with at least one of the Layer 2 MIB
   modules.

6.2.  Tables

   The tables in the LDP MIB for configuring the LDP behavior of an LSR
   are as follows.

   -  The LDP Entity Table (mplsLdpEntityTable) provides a way to
      configure the LSR for using LDP.  There must be at least one LDP
      Entity for the LSR to support LDP.  Each entry/row in this table
      represents a single LDP Entity.

   -  Several tables exist to help configure LDP's use of labels.  These
      are spread through the MIB modules described in the previous
      section.  They are: mplsLdpEntityGenLRTable,
      mplsLdpEntityAtmParmsTable and mplsLdpEntityAtmLRTable,
      mplsLdpEntityFrameRelayParmsTable and mplsLdpEntityFrLRTable.
      They are used to configure generic, ATM, and Frame Relay labels as
      their names suggest.

   -  The LDP Peer Table (mplsLdpPeerTable) is a read-only table that
      contains information about LDP Peers known to LDP Entities.

   -  The LDP Hello Adjacencies Table (mplsLdpHelloAdjacencyTable) is a
      table of all adjacencies between all LDP Entities and all LDP
      Peers.

   -  Several tables exist to monitor and control LDP sessions.  The LDP
      Session Table (mplsLdpSessionTable) represents sessions between an
      LDP Entity and a Peer.  mplsLdpAtmSesTable and
      mplsLdpFrameRelaySesTable contain session information specific to
      ATM.

   -  The MPLS LDP Session Peer Address Table (mplsLdpSesPeerAddrTable)
      stores addresses learned after session initialization via Address
      Message advertisement.

   -  The LDP FEC Table (mplsFecTable) represents FEC (Forwarding
      Equivalence Class) information that may be in use on one or more
      LSPs.  The LDP LSP FEC Table (mplsLdpLspFecTable) shows the FECs
      associated with each LSP.

   -  MPLS-LDP-STD-MIB has a mapping table (mplsLdpLspTable) that maps
      the LDP MIB's representation of LDP sessions to the underlying LSR
      MIB's representation of the LSPs created by these sessions, by
      pointing to mplsInSegmentTable, mplsOutSegmentTable, and
      mplsXCTable, respectively.

   -  Statistics may be gathered through the LDP Entity Statistics Table
      (mplsLdpEntityStatsTable) and the LDP Session Statistics Table
      (mplsLdpSesStatsTable).

6.3.  Scalars

   Where tables in the MIB modules have arbitrary indexes, scalars are
   provided to supply the next available index.  This applies to
   mplsLdpEntityTable and mplsFecTable.

   Two scalars exist to configure the LSR.  The LSR ID is set in
   mplsLdpLsrId, and the loop detection capabilities are reported in
   mplsLdpLsrLoopDetectionCapable.

6.4.  Notifications

   MPLS-LDP-STD-MIB defines four notifications that a device can issue.

   -  mplsLdpInitSesThresholdExceeded is reported when the number of
      Session Initialization messages exceeds a configured threshold.

   -  mplsLdpPVLMismatch is issued if the Path Vector Limit for a
      configured Entity and Peer do not match.

   -  mplsLdpSessionUp and mplsLdpSessionDown report the transition of
      Session state.

   No scalar object is provided to enable and disable notifications from
   MPLS-LDP-STD-MIB.  Instead, the implementer is referred to [RFC3413].

6.5.  Dependencies between MIB Module Tables

   The many tables in the four LDP MIB modules are related as shown on
   the diagram below.  The arrows indicate a reference from one table to
   another.  Note that in many cases the reference is through an
   augmentation of the referenced table.

   mplsLdpEntityGenLRTable ------------->+
   mplsLdpEntityAtmParmsTable ---------->+
   mplsLdpEntityAtmLRTable ------------->+
   mplsLdpEntityFrameRelayParmsTable --->+
   mplsLdpEntityFrLRTable -------------->+
   mplsLdpEntityStatsTable ------------->+
                                         |
   mplsLdpHelloAdjacencyTable            |
                |                        |
                |  mplsLdpEntityTable <--+
                |      ^       ^
                V      |       |
            mplsLdpPeerTable <-+- mplsLdpSesPeerAddrTable
                       ^       |
                       |       V
                 mplsLdpSessionTable
                              ^   ^
                              |   |
   mplsLdpSesStatsTable ------+   +-- mplsLdpLspFecTable
   mplsLdpAtmSesTable --------+   |    |       |
   mplsLdpFrameRelaySesTable--+   |    |       V
                                  |    |    mplsFecTable
                                  |    V
                                  +-- mplsLdpLspTable

7.  Tables, Scalars, and Notifications in MPLS-TE-STD-MIB

7.1.  Tables

   MPLS-TE-STD-MIB contains the following tables.

   -  The Tunnel Table (mplsTunnelTable) is used to configure and report
      MPLS tunnels.  Note that reporting of tunnels in this table at
      transit LSRs is optional.

      Entries in mplsTunnelTable are indexed by four objects.  The
      source and destination LSR IDs give context to the entry, and an
      index  (mplsTunnelIndex) identifies the tunnel itself.  However,
      the fourth index (mplsTunnelInstance) may give rise to some
      confusion since its usage is not clearly explained.

      The description says: "Uniquely identifies an instance of a
      tunnel.  It is useful to identify multiple instances of tunnels
      for the purposes of backup and parallel tunnels." In the case of
      backup tunnels, multiple instances of the same tunnel may be
      defined, but only one is active at any time.  Different instances
      may have different properties (such as explicit routes), and one
      instance may be set up to protect against failure of another.

      Parallel tunnels may be used to provide load sharing or
      protection.

      The mplsTunnelInstancePriority object is used to indicate the
      precedence of tunnels with the same LSR IDs and mplsTunnelIndex
      value.  The mplsTunnelPrimaryInstance object gives a quick
      reference back to the preferred instance of the tunnel.

      The mplsTunnelIndex value is typically signaled as the Tunnel ID,
      and the mplsTunnelInstance as the LSP ID, in protocols where both
      fields exist.  In protocols where there is only one identifying
      index (usually known as the LSP ID), only the mplsTunnelIndex is
      signaled.

   -  The Resource Table (mplsTunnelResourceTable) is used to configure
      resources to be requested on this tunnel.  The CRLDP resource
      table (mplsTunnelCRLDPResTable) is used to request additional
      resource details that are specific to tunnels signaled using CR-
      LDP.

   -  The routes requested, computed, and actually used for a tunnel are
      found in the Tunnel Hop Table (mplsTunnelHopTable), Tunnel
      Computed Hop Table (mplsTunnelCHopTable), and Tunnel Actual Hop
      Table (mplsTunnelARHopTable).

   -  Statistics about the performance of tunnels may be gathered
      through the Tunnel Performance Table (mplsTunnelPerfTable).

7.2.  Scalars

   Where tables in the MIB module have arbitrary indexes, scalars are
   provided to supply the next available index.  This applies to
   mplsTunnelTable, mplsTunnelResourceTable, and mplsTunnelHopTable.

   Two scalars exist to configure the support for MPLS tunnels on the
   LSR.  mplsTunnelTEDistProto lists the signaling methods and protocols
   supported.  mplsTunnelMaxHops defines the size of route that may be
   configured on the LSR.

   Two further scalars enhance the statistics on the LSR by counting the
   number of configured (mplsTunnelConfigured) and active
   (mplsTunnelActive) tunnels.

   The scalar mplsTunnelNotificationMaxRate is used to control the rate
   at which notifications are issued from MPLS-TE-STD-MIB.  A rate of
   zero means that notifications must not be issued.  If notifications

   would be generated faster than the configured rate, an implementation
   may choose to discard notifications or to queue them for distribution
   at a quieter time.

7.3.  Notifications

   MPLS-TE-STD-MIB defines four notifications that a device can issue.
   The rate of dispatch of notifications is controlled as described in
   the previous section.

   -  mplsTunnelUp and mplsTunnelDown report the transition of Tunnel
      state.

   -  Rerouting and re-optimization of Tunnels paths are reported by
      mplsTunnelRerouted and mplsTunnelReoptimized.

7.4.  Dependencies between MIB Module Tables

   The tables in MPLS-TE-STD-MIB are related as shown on the diagram
   below.  The arrows indicate a reference from one table to another.

                        mplsTunnelPerfTable
                                ^
                                |
                                V
                         mplsTunnelTable
                             |      |
                             V      |
        mplsTunnelResourceTable     +--> mplsTunnelHopTable
              ^                     |
              |                     +--> mplsTunnelCHopTable
              V                     |
   mplsTunnelCRLDPResTable          +--> mplsTunnelARHopTable

8.  Tables, Scalars, and Notifications in MPLS-FTN-STD-MIB

8.1.  Tables

   MPLS-FTN-STD-MIB contains the following tables.

   -  The FEC-to-NHLFE Table (mplsFTNTable) defines the FEC to NHLFE
      rules to be applied to incoming packets, and the actions to be
      taken on matching packets.

   -  The FEC-to-NHLFE Mapping Table (mplsFTNMapTable) provides the
      capability to activate FTN rules defined in the mplsFTNTable on
      specific interfaces in the system.

   -  Performance statistics for FTN rules are found in the
      mplsFTNPerfTable.

8.2.  Scalars

   This MIB module contains the scalars mplsFTNTableLastChanged and
   mplsFTNMapTableLastChanged to indicate the last time an object
   changed in mplsFTNTable and mplsFTNMapTable, respectively.  Another
   scalar, mplsFTNIndexNext, is used to supply the next valid index for
   creating new conceptual rows in mplsFTNTable.

8.3.  Notifications

   There are no notifications in this MIB module.

8.4.  Dependencies between MIB Module Tables

   The tables in MPLS-FTN-STD-MIB are related as shown on the diagram
   below.  The arrows indicate a reference from one table to another.

                         mplsFTNTable
                              ^
                              |
                       mplsFTNMapTable
                              ^
                              |
                       mplsFTNPerfTable

9.  Tables and Objects in TE-LINK-STD-MIB

9.1.  Tables

   TE-LINK-STD-MIB contains the following tables.

   -  The TE link table (teLinkTable) is used to specify TE links,
      including bundled links, and their generic traffic-engineering
      parameters.

   -  The TE link descriptor table (teLinkDescriptorTable) is used to
      list the TE link descriptors.

   -  The shared risk link group (SRLG) table (teLinkSrlgTable) is used
      to specify the SRLGs associated with TE links.

   -  The TE link bandwidth table (teLinkBandwidthTable) is used to
      report priority-based bandwidth values associated with TE links.

   -  The component link table (componentLinkTable) is used to identify
      the data-bearing component links that are associated with the TE
      links and specify the data-bearing link generic traffic
      engineering parameters.

   -  The component link descriptor table (componentLinkDescriptorTable)
      is used to list the data-bearing component link descriptors.

   -  The component link bandwidth table (componentLinkBandwidthTable)
      is used to report priority-based bandwidth values associated with
      data-bearing component links.

9.2.  Scalars

   There are no scalars in this MIB module.

9.3.  Notifications

   There are no notifications in this MIB module.

9.4.  Dependencies between MIB Module Tables

   The tables in TE-LINK-STD-MIB are related as shown on the diagram
   below.  The arrows indicate a reference from one table to another.

   Note that many of the associations between tables are through a
   common index that is the ifIndex of the related interface.

                   teLinkTable
                            ^
                            |
   teLinkDescriptorTable ---+
                            |
   teLinkSrlgTable ---------+
                            |
   teLinkBandwidthTable ----+

                   componentLinkTable
                                   ^
                                   |
   componentLinkDescriptorTable ---+
                                   |
   componentLinkBandwidthTable ----+

10.  Table Dependencies between MPLS MIB Modules

   Section 4.11 gave an overview of how the MPLS MIB modules are
   related.  Now that the tables in the MIB modules have been
   introduced, it is possible to give a more detailed diagram of these
   relationships.

   MPLS-TC-STD-MIB is left off the diagram because many of the MIB
   module tables use textual conventions from that MIB module.

             mplsLsrXCTable   mplsLsrInSegmentTable
                         ^     ^
                         |     |
                         +---- mplsLdpLspTable
                         |     |
   mplsTunnelTable ------+     V
      ^                  |    mplsLsrOutSegmentTable
      |                  |
   mplsFTNTable ---------+

11.  A Note on Interfaces

   The Interfaces Group of IF-MIB [RFC2863] defines generic managed
   objects for managing interfaces.  The MPLS MIB modules make
   references to interfaces so that it can be clearly determined where
   the procedures managed by the MIB modules should be performed.
   Additionally, the MPLS MIB modules (notably MPLS-TE-STD-MIB and TE-
   LINK-STD-MIB) utilize interface stacking within the Interface Group.

11.1.  MPLS Tunnels as Interfaces

   MPLS-TE-STD-MIB builds on the concept of managing MPLS Tunnels as
   logical interfaces.  [RFC2863] states that the interfaces table
   (ifTable) contains information on the managed resource's interfaces,
   and that each sub-layer below the internetwork layer of a network
   interface is considered an interface.  Thus, an MPLS Tunnel managed
   as an interface is represented as an entry in the ifTable.  The
   interrelation of entries in the ifTable is defined by the Interfaces
   Stack Group defined in [RFC2863].

   When using MPLS Tunnels as interfaces, the interface stack table
   might appear as follows:

   +------------------------------------------------+
   | MPLS tunnel interface ifType = mplsTunnel(150) |
   +------------------------------------------------+
   |        MPLS interface ifType = mpls(166)       |
   +------------------------------------------------+
   |               Underlying layer                 |
   +------------------------------------------------+

   In the diagram above, "Underlying layer" refers to the ifIndex of any
   interface type for which MPLS internetworking has been defined.
   Examples include ATM, Frame Relay, and Ethernet.

   A detailed listing of the mapping between ifTable objects and their
   use for MPLS Tunnels is given in [TEMIB].  A few key objects are
   listed here to provide an overview of the concepts.

   Each MPLS tunnel is represented by an entry in the ifTable.  Each
   tunnel is therefore assigned a unique ifIndex.

   The type of an interface represented by an entry in the ifTable is
   indicated by the ifType object.  The value that is allocated to
   identify an MPLS tunnel is 150.

   The ifOperStatus object reflects the actual operational status of the
   MPLS tunnel and may be mapped from the mplsTunnelOperStatus object.

   It may be considered convenient and good management to set the ifName
   object to reflect the name of the MPLS tunnel as contained in the
   mplsTunnelName object.

11.2.  Application of the Interfaces Group to TE Links

   TE-LINK-STD-MIB also uses interface stacking to manage TE Link
   interfaces as logical interfaces.  The TE Link interface is
   represented as an entry in the ifTable.  The interrelation of entries
   in the ifTable is defined by Interfaces Stack Group defined in
   [RFC2863].  When using TE Link interfaces, the interface stack table
   might appear as follows:

   +-------------------------------------------------------------------+
   | MPLS interface ifType = mpls(166)                                 |
   | ifIndex = 1                                                       |
   +-------------------------------------------------------------------+
   | TE link (bundled link) ifType = teLink(200)                       |
   | ifIndex = 2                                                       |
   +--------------------------------+-+--------------------------------+
   | TE link ifType = teLink(200)   | | TE link ifType = teLink(200)   |
   | ifIndex = 3                    | | ifIndex = 4                    |
   +--------------------------------+ +--------------------------------+
   | Component link                 | | Component link                 |
   | ifType = opticalTransport(196) | | ifType = opticalTransport(196) |
   | ifIndex = 5                    | | ifIndex = 6                    |
   +--------------------------------+ +--------------------------------+

   In the above diagram, "opticalTransport" is an example of an
   underlying physical interface: in this case an optical transport
   interface.  TE link management and bundling can be seen in the levels
   of interface stacking.  Two TE links are defined, each managing an
   optical transport link.  These two TE links are combined into a
   bundle, which is managed as a single TE link interface.  This TE Link
   interface supports MPLS and is presented as an MPLS interface.

   A detailed listing of the mapping between ifTable objects and their
   use for TE Links is given in [TELMIB].  A few key objects are listed
   here to provide an overview of the concepts.

   Each TE Link interface is represented by a separate entry in the
   ifTable, with a unique ifIndex.

   The type of an interface represented by an entry in the ifTable is
   indicated by the ifType object.  The value that is allocated to
   identify a TE Link is 200.

11.3.  References to Interface MIB Objects from MPLS MIB Modules

   MPLS-TE-STD-MIB contains two objects that reference the management of
   an MPLS tunnel as an interface.  mplsTunnelIsIf is a TruthValue that
   indicates whether the tunnel is present in the ifTable.  If the
   tunnel is managed as an interface, the mplsTunnelIfIndex object
   contains the ifIndex that identifies the corresponding entry in the
   ifTable.

   MPLS-LSR-STD-MIB includes a table (mplsInterfaceTable) for
   configuring the support for MPLS on specific interfaces.  A
   conceptual row in this table is created automatically by an LSR for
   every interface that is capable of and configured for support of
   MPLS.  A conceptual row in this table will exist if and only if a

   corresponding entry in ifTable exists with ifType = mpls(166).  The
   fate of the entries in the two tables are closely linked so that if
   the entry in the ifTable is operationally disabled, the entry in
   mplsInterfaceTable is deleted.  During the life of an entry in
   mplsInterfaceTable, a corresponding entry is managed in
   mplsInterfacePerfTable to show performance counters for the MPLS-
   capable interface.

   The ifIndex that identifies MPLS-capable interfaces also plays an
   important indexing role in MPLS-LSR-STD-MIB.  In-segments (that is,
   incoming LSP labels) are represented in mplsInSegmentTable, which is
   indexed by the mplsInSegmentIfIndex and mplsInSegmentLabel objects.
   mplsInSegmentIfIndex is set to the ifIndex of the incoming MPLS-
   capable interface.  mplsInSegmentLabel identifies the incoming MPLS
   label.  Note that the corresponding mplsOutSegmentTable contains an
   mplsOutSegmentIfIndex object to identify the outgoing MPLS-capable
   interface, but that this does not form part of the index of the
   table.

   MPLS-LDP-STD-MIB uses ifIndex extensively to identify the interface
   over which MPLS is active.

   Within MPLS-FTN-STD-MIB, mplsFTNMapTable maps entries in mplsFTNTable
   to interfaces on which mplsFTNTable entries should be activated.
   Interfaces are identified using their ifIndex values.

12.  Management Options

   It is not the intention of this document to provide instructions or
   advice to implementers of Management Stations, Management Agents, or
   managed entities.  It is, however, useful to make some observations
   about how the MIB modules described above might be used to manage
   MPLS systems.

   All MPLS LSPs may appear in MPLS-LSR-STD-MIB.  At transit nodes, they
   are seen as full cross-connects between incoming labels on incoming
   interfaces and outgoing labels on outgoing interfaces.  At ingress or
   egress points, the cross-connections are unbalanced having spoof
   upstream or downstream legs, respectively.

   Split and merge points of LSPs may be represented as more complex
   cross-connects in MPLS-LSR-STD-MIB.  Similarly, bidirectional LSPs
   can be represented by using the same cross-connect index for each of
   the forward and reverse cross-connections.

   The modules in the LDP MIB are intended solely for use with LDP and
   CR-LDP.  LSPs that are signaled through other means may conveniently
   be stored in mplsLdpLspTable for consistency with LSPs set up using

   LDP, but there is little further value to this because the table
   gives only pointers into MPLS-LSR-STD-MIB.  If, however, the LSPs are
   established with associated FECs using some signaling method other
   than LDP (for example, BGP), it may be advantageous to use
   mplsLdpLspTable, mplsFecTable, and mplsLdpLspFecTable to correlate
   the LSPs.

   Note that if CR-LDP is the signaling protocol, there is no
   requirement to use the LSP-related tables in the LDP MIB since the
   LSP will be adequately represented in MPLS-TE-MIB and MPLS-LSR-STD-
   MIB.

   MPLS tunnels may be represented in MPLS-TE-STD-MIB with their cross-
   connects indicated in MPLS-LSR-STD-MIB.  Tunnels are often (although
   not always) set up with a series of constraints that may be
   represented in MPLS-TE-STD-MIB.  Note that a distinguishing feature
   of a tunnel is that it has an ingress and an egress, where LSPs
   established through LDP may be end-to-end or may be hop-by-hop.

   All LSPs (tunnels and non-tunnels) may be established as a result of
   signaling protocols already defined or for future study.  In
   addition, LSPs may be set up manually by issuing configuration
   commands to each of the LSRs on the LSP.  These commands may utilize
   SNMP by performing SET operations to the MIB module tables and
   objects described here.  Alternatively, configuration may be through
   some non-standard interface such as a Command Line or a Graphical
   User Interface.  Such configured LSPs may also be represented in the
   MIB module tables.

   Do not be misled by considerations of the "permanence" of LSPs when
   deciding which tables of which MIB modules to use.  An MPLS tunnel
   may have a very long life expectancy if it is set up by an amnesiac
   user.  Otherwise, it may have a very short lifetime if it is
   automatically provisioned to satisfy on-demand traffic requirements.
   Similarly, an LSP established in response to a routing protocol
   (sometimes known as a hop-by-hop LSP) may be equally stable or
   unstable.

13.  Related IETF MIB Modules

   This section describes the broad interactions between MIB modules
   produced by the PWE3, PPVPN, and CCAMP working groups and the MPLS
   MIB modules.  This information is provided as background and is not
   central to this document.

13.1.  PWE3 Working Group MIB Modules

   The PWE3 working group has produced a document [PWE3FW] that includes
   a description of the framework for MIB modules within PWE3 operation.
   Since the PWE3 architecture includes the use of MPLS as an emulated
   service and as a PSN service, the MPLS MIB modules described above
   may be leveraged.  The PWE3 framework document describes the
   interactions between the MPLS MIB modules and the PWE3 MIB modules.

13.2.  PPVPN Working Group MIB Modules

   At present, the PPVPN working group has not included a discussion of
   how the MPLS MIB modules interact with the MIB modules being produced
   by that working group.  The authors of this document hope to make a
   forthcoming addition to the PPVPN framework document [PPVPNFW]
   detailing these interactions.  At the moment, there are two MIB
   modules, [VPNMIB] and [VPNTCMIB], which are discussed next.

13.2.1.  PPVPN-MPLS-VPN-STD-MIB

   PPVPN-MPLS-VPN-STD-MIB describes managed objects that are used to
   model and manage RFC2547bis MPLS VPNs [RFC2547Bis].  This MIB module
   contains tables that model virtual routing forwarding entries (VRFs),
   as well as the interfaces associated with those VRFs.

13.2.1.1.  Position in the OID Tree

      transmission -- RFC 2578 [RFC2578]
        |
        +- vpnMIB -- PPVPN-MPLS-VPN-STD-MIB

13.2.1.2.  Dependencies

   This MIB module currently has no direct dependencies on any of the
   MPLS MIB modules.  This MIB module models MPLS VPN interfaces as
   entries in the Interfaces MIB's Interfaces Table (ifTable).  This MIB
   module may be modified in the future to import textual conventions
   from MPLS-TC-STD-MIB.

   A specific textual conventions MIB module [VPNTCMIB] defines textual
   conventions that are imported into PPVPN-MPLS-VPN-STD-MIB.

13.3.  CCAMP Working Group MIB Modules

   The CCAMP working group is developing MIB modules in support of GMPLS
   that interact directly with the MPLS MIB modules.  Along with any MIB
   modules produced by the CCAMP working group, a separate CCAMP-

   specific Management Framework document is expected to be issued
   describing the relationship between these MIB modules and the
   existing MPLS (and other) MIB modules.

14.  Traffic Engineering Working Group TE MIB

   The TEWG has produced a traffic engineering MIB (TE-MIB) [TEWGMIB]
   containing objects for monitoring traffic-engineered tunnels at their
   ingress points.

   In many senses TE-MIB contains the same information as MPLS-TE-STD-
   MIB.  Both MIB modules can be used to monitor MPLS tunnels; however,
   TE-MIB is minimalistic and caters best to TE tunnels as tunnels, at
   the expense of not having many advanced features of MPLS-TE-STD-MIB,
   whereas MPLS-TE-STD-MIB can deconstruct tunnels into hop-by-hop
   cross-connects, at the expense of more complexity.

   The TE-MIB module imports textual conventions from the MPLS-TC-STD-
   MIB module and therefore is dependent on that document.

14.1.  Choosing between TE MIB Modules

   TE-MIB is a flexible MIB module designed to manage traffic
   engineering tunnels regardless of the implementation technology.
   This flexibility and a focus on simplicity lead to some compromises.

   - Some MPLS configuration parameters are left out.  For example, the
     resource management in TE-MIB is confined to bandwidth, so missing
     the full IntServ control.

   - Other TE-MIB parameters are present but with only limited options;
     for example, the ability to configure different label distribution
     methods per LSP.

   Extensibility of TE-MIB to related concepts (such as DiffServ and
   Fast Reroute) and integrations with other MIB modules (such as that
   in MPLS-LSR-STD-MIB) are not work items at the time of writing.  The
   MPLS MIB modules are more closely integrated as described in this
   document.

   Write/create access to TE-MIB is only available at the ingress, where
   it can be used to configure an ingress to signal a tunnel with
   constraints.  It cannot be used to configure hop-by-hop cross-
   connects to build a tunnel.

   The purpose of TE-MIB module is to allow a Management Agent to
   configure tunnels, and to inspect and monitor all tunnels (however
   created) at their ingress points.  It does not provide information

   about tunnels at any other point in the network (that is, at transit
   or egress nodes).  This module can be used, for example, to configure
   the constraints of a tunnel, whereupon the ingress would compute the
   tunnel path and signal it.  The MIB module can then be used at the
   ingress to monitor the tunnel's path(s), their status, and the
   tunnel's uptime and counters.  This MIB module is not designed to
   configure hop-by-hop cross-connects to build a tunnel.

15.  Security Considerations

   This document describes the interrelationships amongst the different
   MIB modules relevant to MPLS management and as such does not have any
   security implications in and of itself.

   Each specific MIB document specifies specific MIB objects, and such a
   document must provide a proper security considerations section that
   explains the security aspects of those objects.

   The attention of readers is particularly drawn to the security
   implications of making MIB objects available for create or write
   access through an access protocol such as SNMP.  SNMPv1 by itself is
   an insecure environment.  Even if the network itself is made secure
   (for example, by using IPSec), there is no control over who on the
   secure network is allowed to access and GET (read) the objects in
   this MIB.  It is recommended that the implementers consider the
   security features as provided by the SNMPv3 framework.  Specifically,
   the use of the User-based Security Model STD 62, RFC 3414 [RFC3414],
   and the View-based Access Control Model STD 62, RFC 3415 [RFC3415],
   is recommended.

   It is then a customer/user responsibility to ensure that the SNMP
   entity giving access to an instance of this MIB is properly
   configured to give access to only those objects, and to those
   principals (users) that have legitimate rights to access them.

16.  Acknowledgements

   Many small pieces of text in this document have been borrowed from
   the documents that define the MIB modules described here.  The
   authors would like to express appreciation to all who worked on those
   MIB documents.

   Thanks also to all those who attended the November 2002 MPLS MIB open
   meeting and gave constructive feedback, and in particular to Sharon
   Chisholm for her thoughts on Management Options.

   Thanks to Kireeti Kompella for revising the text on TE-MIB.

   Without the consistent pressure and encouragement from Bert Wijnen,
   this document would not have been written.

17.  Normative References

   [FTNMIB]      Nadeau, T., Srinivasan, C., and A. Viswanathan,
                 "Multiprotocol Label Switching (MPLS) Forwarding
                 Equivalence Class To Next Hop Label Forwarding Entry
                 (FEC-To-NHLFE) Management Information Base (MIB)", RFC
                 3814, June 2004.

   [LDPMIB]      Cucchiara, J., Sjostrand, H., and J. Luciani,
                 "Definitions of Managed Objects for the Multiprotocol
                 Label Switching (MPLS), Label Distribution Protocol
                 (LDP)", RFC 3815, June 2004.

   [LSRMIB]      Srinivasan, C., Viswanathan, A., and T. Nadeau,
                 "Multiprotocol Label Switching (MPLS) Label Switching
                 Router (LSR) Management Information Base (MIB)", RFC
                 3813, June 2004.

   [RFC2863]     McCloghrie, K. and F. Kastenholtz, "The Interfaces
                 Group MIB ", RFC 2863, June 2000.

   [RFC3289]     Baker, F., Chan, K., and A. Smith, "Management
                 Information Base for the Differentiated Services
                 Architecture", RFC 3289, May 2002.

   [TCMIB]       Nadeau, T. and J. Cucchiara, "Definitions of Textual
                 Conventions (TCs) for Multiprotocol Label Switching
                 (MPLS) Management", RFC 3811, June 2004.

   [TELMIB]      Dubuc, M., Dharanikota, S., Nadeau, T., J. Lang,
                 "Traffic Engineering Link Management Information Base",
                 RFC 4220, November 2005.

   [TEMIB]       Srinivasan, C., Viswanathan, A., and T. Nadeau,
                 "Multiprotocol Label Switching (MPLS) Traffic
                 Engineering (TE) Management Information Base (MIB)",
                 RFC 3812, June 2004.

18.  Informative References

   [PPVPNFW]     Callon, R. and M. Suzuki, "A Framework for Layer 3
                 Provider-Provisioned Virtual Private Networks
                 (PPVPNs)", RFC 4110, July 2005.

   [PWE3FW]      Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-
                 to-Edge (PWE3) Architecture", RFC 3985, March 2005.

   [RFC2026]     Bradner, S., "The Internet Standards Process --
                 Revision 3", BCP 9, RFC 2026, October 1996.

   [RFC2547Bis]  Rosen, E., et al., "MPLS/BGP VPNs", Work in Progress,
                 October 2002.

   [RFC2578]     McCloghrie, K., Perkins, D., and J. Schoenwaelder,
                 "Structure of Management Information Version 2
                 (SMIv2)", STD 58, RFC 2578, April 1999.

   [RFC2579]     McCloghrie, K., Perkins, D., and J. Schoenwaelder,
                 "Textual Conventions for SMIv2", STD 58, RFC 2579,
                 April 1999.

   [RFC2580]     McCloghrie, K., Perkins, D., and J. Schoenwaelder,
                 "Conformance Statements for SMIv2", STD 58, RFC 2580,
                 April 1999.

   [RFC3031]     Rosen, E., Viswanathan, A., and R. Callon,
                 "Multiprotocol Label Switching Architecture", RFC 3031,
                 January 2001.

   [RFC3036]     Andersson, L., Doolan, P., Feldman, N., Fredette, A.,
                 and B. Thomas, "LDP Specification", RFC 3036, January
                 2001.

   [RFC3410]     Case, J., Mundy, R., Partain, D. and B. Stewart,
                 "Introduction and Applicability Statements for
                 Internet-Standard Management Framework", RFC 3410,
                 December 2002.

   [RFC3413]     Levi, D., Meyer, P., and B. Stewart, "Simple Network
                 Management Protocol (SNMP) Applications", STD 62, RFC
                 3413, December 2002.

   [RFC3414]     Blumenthal, U. and B. Wijnen, "User-based Security
                 Model (USM) for version 3 of the Simple Network
                 Management Protocol (SNMPv3)", STD 62, RFC 3414,
                 December 2002.

   [RFC3415]     Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based
                 Access Control Model (VACM) for the Simple Network
                 Management Protocol (SNMP)", STD 62, RFC 3415, December
                 2002.

   [TEWGMIB]     Kompella, K., "A Traffic Engineering (TE) MIB", RFC
                 3970, January 2005.

   [VPNMIB]      Nadeau, T., et al., "MPLS/BGP Virtual Private Network
                 Management Information Base Using SMIv2", Work in
                 Progress, November 2002.

   [VPNTCMIB]    Schliesser, B. and T. Nadeau, "Definition of Textual
                 Conventions for Provider Provisioned Virtual Private
                 Network (PPVPN) Management", Work in Progress, November
                 2002.

Authors' Addresses

   Thomas D. Nadeau
   Cisco Systems, Inc.
   1414 Massachusetts Ave.
   Boxborough, MA 01719

   EMail: tnadeau@cisco.com

   Cheenu Srinivasan
   Bloomberg L.P.
   731 Lexington Avenue
   New York, NY 10022

   Phone: (212) 617-3682
   EMail: cheenu@bloomberg.net

   Adrian Farrel
   Old Dog Consulting

   Phone: +44 (0) 1978 860944
   EMail: adrian@olddog.co.uk

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