





Network Working Group                                      K. McCloghrie
Request for Comments: 2863                                 Cisco Systems
Obsoletes: 2233                                            F. Kastenholz
Category: Standards Track                                 Argon Networks
                                                               June 2000


                        The Interfaces Group MIB

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Table of Contents

   1 Introduction .................................................    2
   2 The SNMP Network Management Framework ........................    2
   3 Experience with the Interfaces Group .........................    3
   3.1 Clarifications/Revisions ...................................    4
   3.1.1 Interface Sub-Layers .....................................    4
   3.1.2 Guidance on Defining Sub-layers ..........................    7
   3.1.3 Virtual Circuits .........................................    8
   3.1.4 Bit, Character, and Fixed-Length Interfaces ..............    8
   3.1.5 Interface Numbering ......................................   10
   3.1.6 Counter Size .............................................   14
   3.1.7 Interface Speed ..........................................   16
   3.1.8 Multicast/Broadcast Counters .............................   17
   3.1.9 Trap Enable ..............................................   17
   3.1.10 Addition of New ifType values ...........................   18
   3.1.11 InterfaceIndex Textual Convention .......................   18
   3.1.12 New states for IfOperStatus .............................   18
   3.1.13 IfAdminStatus and IfOperStatus ..........................   19
   3.1.14 IfOperStatus in an Interface Stack ......................   21
   3.1.15 Traps ...................................................   21
   3.1.16 ifSpecific ..............................................   23
   3.1.17 Creation/Deletion of Interfaces .........................   23
   3.1.18 All Values Must be Known ................................   24
   4 Media-Specific MIB Applicability .............................   24
   5 Overview .....................................................   25
   6 Interfaces Group Definitions .................................   26



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   7 Acknowledgements .............................................   64
   8 References ...................................................   64
   9 Security Considerations ......................................   66
   10 Authors' Addresses ..........................................   67
   11 Changes from RFC 2233 .......................................   67
   12 Notice on Intellectual Property .............................   68
   13 Full Copyright Statement ....................................   69

1.  Introduction

   This memo defines a portion of the Management Information Base (MIB)
   for use with network management protocols in the Internet community.
   In particular, it describes managed objects used for managing Network
   Interfaces.  This memo discusses the 'interfaces' group of MIB-II
   [17], especially the experience gained from the definition of
   numerous media-specific MIB modules for use in conjunction with the '
   interfaces' group for managing various sub-layers beneath the
   internetwork-layer.  It specifies clarifications to, and extensions
   of, the architectural issues within the MIB-II model of the '
   interfaces' group.  This memo obsoletes RFC 2233, the previous
   version of the Interfaces Group MIB.

   The key words "MUST" and "MUST NOT" in this document are to be
   interpreted as described in RFC 2119 [16].

2.  The SNMP Network Management Framework

   The SNMP Management Framework presently consists of five major
   components:

      o  An overall architecture, described in RFC 2571 [1].

      o  Mechanisms for describing and naming objects and events for the
         purpose of management.  The first version of this Structure of
         Management Information (SMI) is called SMIv1 and described in
         STD 16, RFC 1155 [2], STD 16, RFC 1212 [3] and RFC 1215 [4].
         The second version, called SMIv2, is described in STD 58, which
         consists of RFC 2578 [5], RFC 2579 [6] and RFC 2580 [7].

      o  Message protocols for transferring management information.  The
         first version of the SNMP message protocol is called SNMPv1 and
         described in STD 15, RFC 1157 [8].  A second version of the
         SNMP message protocol, which is not an Internet standards track
         protocol, is called SNMPv2c and described in RFC 1901 [9] and
         RFC 1906 [10].  The third version of the message protocol is
         called SNMPv3 and described in RFC 1906 [10], RFC 2572 [11] and
         RFC 2574 [12].




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      o  Protocol operations for accessing management information.  The
         first set of protocol operations and associated PDU formats is
         described in STD 15, RFC 1157 [8].  A second set of protocol
         operations and associated PDU formats is described in RFC 1905
         [13].

      o  A set of fundamental applications described in RFC 2573 [14]
         and the view-based access control mechanism described in RFC
         2575 [15].

   A more detailed introduction to the current SNMP Management Framework
   can be found in RFC 2570 [22].

   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  Objects in the MIB are
   defined using the mechanisms defined in the SMI.

   This memo specifies a MIB module that is compliant to the SMIv2.  A
   MIB conforming to the SMIv1 can be produced through the appropriate
   translations.  The resulting translated MIB must be semantically
   equivalent, except where objects or events are omitted because no
   translation is possible (e.g., use of Counter64).  Some machine
   readable information in SMIv2 will be converted into textual
   descriptions in SMIv1 during the translation process.  However, this
   loss of machine readable information is not considered to change the
   semantics of the MIB.

3.  Experience with the Interfaces Group

   One of the strengths of internetwork-layer protocols such as IP [18]
   is that they are designed to run over any network interface.  In
   achieving this, IP considers any and all protocols it runs over as a
   single "network interface" layer.  A similar view is taken by other
   internetwork-layer protocols.  This concept is represented in MIB-II
   by the 'interfaces' group which defines a generic set of managed
   objects such that any network interface can be managed in an
   interface-independent manner through these managed objects.  The '
   interfaces' group provides the means for additional managed objects
   specific to particular types of network interface (e.g., a specific
   medium such as Ethernet) to be defined as extensions to the '
   interfaces' group for media-specific management.  Since the
   standardization of MIB-II, many such media-specific MIB modules have
   been defined.

   Experience in defining these media-specific MIB modules has shown
   that the model defined by MIB-II is too simplistic and/or static for
   some types of media-specific management.  As a result, some of these
   media-specific MIB modules assume an evolution or loosening of the



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   model.  This memo documents and standardizes that evolution of the
   model and fills in the gaps caused by that evolution.  This memo also
   incorporates the interfaces group extensions documented in RFC 1229
   [19].

3.1.  Clarifications/Revisions

   There are several areas for which experience has indicated that
   clarification, revision, or extension of the model would be helpful.
   The following sections discuss the changes in the interfaces group
   adopted by this memo in each of these areas.

   In some sections, one or more paragraphs contain discussion of
   rejected alternatives to the model adopted in this memo.  Readers not
   familiar with the MIB-II model and not interested in the rationale
   behind the new model may want to skip these paragraphs.

3.1.1.  Interface Sub-Layers

   Experience in defining media-specific management information has
   shown the need to distinguish between the multiple sub-layers beneath
   the internetwork-layer.  In addition, there is a need to manage these
   sub-layers in devices (e.g., MAC-layer bridges) which are unaware of
   which, if any, internetwork protocols run over these sub-layers.  As
   such, a model of having a single conceptual row in the interfaces
   table (MIB-II's ifTable) represent a whole interface underneath the
   internetwork-layer, and having a single associated media-specific MIB
   module (referenced via the ifType object) is too simplistic.  A
   further problem arises with the value of the ifType object which has
   enumerated values for each type of interface.

   Consider, for example, an interface with PPP running over an HDLC
   link which uses a RS232-like connector.  Each of these sub-layers has
   its own media-specific MIB module.  If all of this is represented by
   a single conceptual row in the ifTable, then an enumerated value for
   ifType is needed for that specific combination which maps to the
   specific combination of media-specific MIBs.  Furthermore, such a
   model still lacks a method to describe the relationship of all the
   sub-layers of the MIB stack.

   An associated problem is that of upward and downward multiplexing of
   the sub-layers.  An example of upward multiplexing is MLP (Multi-
   Link-Procedure) which provides load-sharing over several serial lines
   by appearing as a single point-to-point link to the sub-layer(s)
   above.  An example of downward multiplexing would be several
   instances of PPP, each framed within a separate X.25 virtual circuit,





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   all of which run over one fractional T1 channel, concurrently with
   other uses of the T1 link.  The MIB structure must allow these sorts
   of relationships to be described.

   Several solutions for representing multiple sub-layers were rejected.
   One was to retain the concept of one conceptual row for all the sub-
   layers of an interface and have each media-specific MIB module
   identify its "superior" and "subordinate" sub-layers through OBJECT
   IDENTIFIER "pointers".  This scheme would have several drawbacks: the
   superior/subordinate pointers would be contained in the media-
   specific MIB modules; thus, a manager could not learn the structure
   of an interface without inspecting multiple pointers in different MIB
   modules; this would be overly complex and only possible if the
   manager had knowledge of all the relevant media-specific MIB modules;
   MIB modules would all need to be retrofitted with these new
   "pointers"; this scheme would not adequately address the problem of
   upward and downward multiplexing; and finally, enumerated values of
   ifType would be needed for each combination of sub-layers.  Another
   rejected solution also retained the concept of one conceptual row for
   all the sub-layers of an interface but had a new separate MIB table
   to identify the "superior" and "subordinate" sub-layers and to
   contain OBJECT IDENTIFIER "pointers" to the media-specific MIB module
   for each sub-layer.  Effectively, one conceptual row in the ifTable
   would represent each combination of sub-layers between the
   internetwork-layer and the wire.  While this scheme has fewer
   drawbacks, it still would not support downward multiplexing, such as
   PPP over MLP: observe that MLP makes two (or more) serial lines
   appear to the layers above as a single physical interface, and thus
   PPP over MLP should appear to the internetwork-layer as a single
   interface; in contrast, this scheme would result in two (or more)
   conceptual rows in the ifTable, both of which the internetwork-layer
   would run over.  This scheme would also require enumerated values of
   ifType for each combination of sub-layers.

   The solution adopted by this memo is to have an individual conceptual
   row in the ifTable to represent each sub-layer, and have a new
   separate MIB table (the ifStackTable, see section 6 below) to
   identify the "superior" and "subordinate" sub-layers through INTEGER
   "pointers" to the appropriate conceptual rows in the ifTable.  This
   solution supports both upward and downward multiplexing, allows the
   IANAifType to Media-Specific MIB mapping to identify the media-
   specific MIB module for that sub-layer, such that the new table need
   only be referenced to obtain information about layering, and it only
   requires enumerated values of ifType for each sub-layer, not for
   combinations of them.  However, it does require that the descriptions
   of some objects in the ifTable (specifically, ifType, ifPhysAddress,
   ifInUcastPkts, and ifOutUcastPkts) be generalized so as to apply to
   any sub-layer (rather than only to a sub-layer immediately beneath



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   the network layer as previously), plus some (specifically, ifSpeed)
   which need to have appropriate values identified for use when a
   generalized definition does not apply to a particular sub-layer.

   In addition, this adopted solution makes no requirement that a
   device, in which a sub-layer is instrumented by a conceptual row of
   the ifTable, be aware of whether an internetwork protocol runs on top
   of (i.e., at some layer above) that sub-layer.  In fact, the counters
   of packets received on an interface are defined as counting the
   number "delivered to a higher-layer protocol".  This meaning of
   "higher-layer" includes:

   (1)   Delivery to a forwarding module which accepts
         packets/frames/octets and forwards them on at the same protocol
         layer.  For example, for the purposes of this definition, the
         forwarding module of a MAC-layer bridge is considered as a
         "higher-layer" to the MAC-layer of each port on the bridge.

   (2)   Delivery to a higher sub-layer within a interface stack.  For
         example, for the purposes of this definition, if a PPP module
         operated directly over a serial interface, the PPP module would
         be considered the higher sub-layer to the serial interface.

   (3)   Delivery to a higher protocol layer which does not do packet
         forwarding for sub-layers that are "at the top of" the
         interface stack.  For example, for the purposes of this
         definition, the local IP module would be considered the higher
         layer to a SLIP serial interface.

   Similarly, for output, the counters of packets transmitted out an
   interface are defined as counting the number "that higher-level
   protocols requested to be transmitted".  This meaning of "higher-
   layer" includes:

   (1)   A forwarding module, at the same protocol layer, which
         transmits packets/frames/octets that were received on an
         different interface.  For example, for the purposes of this
         definition, the forwarding module of a MAC-layer bridge is
         considered as a "higher-layer" to the MAC-layer of each port on
         the bridge.

   (2)   The next higher sub-layer within an interface stack.  For
         example, for the purposes of this definition, if a PPP module
         operated directly over a serial interface, the PPP module would
         be a "higher layer" to the serial interface.






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   (3)   For sub-layers that are "at the top of" the interface stack, a
         higher element in the network protocol stack.  For example, for
         the purposes of this definition, the local IP module would be
         considered the higher layer to an Ethernet interface.

3.1.2.  Guidance on Defining Sub-layers

   The designer of a media-specific MIB must decide whether to divide
   the interface into sub-layers or not, and if so, how to make the
   divisions.  The following guidance is offered to assist the media-
   specific MIB designer in these decisions.

   In general, the number of entries in the ifTable should be kept to
   the minimum required for network management.  In particular, a group
   of related interfaces should be treated as a single interface with
   one entry in the ifTable providing that:

   (1)   None of the group of interfaces performs multiplexing for any
         other interface in the agent,

   (2)   There is a meaningful and useful way for all of the ifTable's
         information (e.g., the counters, and the status variables), and
         all of the ifTable's capabilities (e.g., write access to
         ifAdminStatus), to apply to the group of interfaces as a whole.

   Under these circumstances, there should be one entry in the ifTable
   for such a group of interfaces, and any internal structure which
   needs to be represented to network management should be captured in a
   MIB module specific to the particular type of interface.

   Note that application of bullet 2 above to the ifTable's ifType
   object requires that there is a meaningful media-specific MIB and a
   meaningful ifType value which apply to the group of interfaces as a
   whole.  For example, it is not appropriate to treat an HDLC sub-layer
   and an RS-232 sub-layer as a single ifTable entry when the media-
   specific MIBs and the ifType values for HDLC and RS-232 are separate
   (rather than combined).

   Subject to the above, it is appropriate to assign an ifIndex value to
   any interface that can occur in an interface stack (in the
   ifStackTable) where the bottom of the stack is a physical interface
   (ifConnectorPresent has the value 'true') and there is a layer-3 or
   other application that "points down" to the top of this stack.  An
   example of an application that points down to the top of the stack is
   the Character MIB [21].






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   Note that the sub-layers of an interface on one device will sometimes
   be different from the sub-layers of the interconnected interface of
   another device; for example, for a frame-relay DTE interface
   connected a frameRelayService interface, the inter-connected DTE and
   DCE interfaces have different ifType values and media-specific MIBs.

   These guidelines are just that, guidelines.  The designer of a
   media-specific MIB is free to lay out the MIB in whatever SMI
   conformant manner is desired.  However, in doing so, the media-
   specific MIB MUST completely specify the sub-layering model used for
   the MIB, and provide the assumptions, reasoning, and rationale used
   to develop that model.

3.1.3.  Virtual Circuits

   Several of the sub-layers for which media-specific MIB modules have
   been defined are connection oriented (e.g., Frame Relay, X.25).
   Experience has shown that each effort to define such a MIB module
   revisits the question of whether separate conceptual rows in the
   ifTable are needed for each virtual circuit.  Most, if not all, of
   these efforts to date have decided to have all virtual circuits
   reference a single conceptual row in the ifTable.

   This memo strongly recommends that connection-oriented sub-layers do
   not have a conceptual row in the ifTable for each virtual circuit.
   This avoids the proliferation of conceptual rows, especially those
   which have considerable redundant information.  (Note, as a
   comparison, that connection-less sub-layers do not have conceptual
   rows for each remote address.)  There may, however, be circumstances
   under which it is appropriate for a virtual circuit of a connection-
   oriented sub-layer to have its own conceptual row in the ifTable; an
   example of this might be PPP over an X.25 virtual circuit.  The MIB
   in section 6 of this memo supports such circumstances.

   If a media-specific MIB wishes to assign an entry in the ifTable to
   each virtual circuit, the MIB designer must present the rationale for
   this decision in the media-specific MIB's specification.

3.1.4.  Bit, Character, and Fixed-Length Interfaces

   RS-232 is an example of a character-oriented sub-layer over which
   (e.g., through use of PPP) IP datagrams can be sent.  Due to the
   packet-based nature of many of the objects in the ifTable, experience
   has shown that it is not appropriate to have a character-oriented
   sub-layer represented by a whole conceptual row in the ifTable.






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   Experience has also shown that it is sometimes desirable to have some
   management information for bit-oriented interfaces, which are
   similarly difficult to represent by a whole conceptual row in the
   ifTable.  For example, to manage the channels of a DS1 circuit, where
   only some of the channels are carrying packet-based data.

   A further complication is that some subnetwork technologies transmit
   data in fixed length transmission units.  One example of such a
   technology is cell relay, and in particular Asynchronous Transfer
   Mode (ATM), which transmits data in fixed-length cells.  Representing
   such a interface as a packet-based interface produces redundant
   objects if the relationship between the number of packets and the
   number of octets in either direction is fixed by the size of the
   transmission unit (e.g., the size of a cell).

   About half the objects in the ifTable are applicable to every type of
   interface: packet-oriented, character-oriented, and bit-oriented.  Of
   the other half, two are applicable to both character-oriented and
   packet-oriented interfaces, and the rest are applicable only to
   packet-oriented interfaces.  Thus, while it is desirable for
   consistency to be able to represent any/all types of interfaces in
   the ifTable, it is not possible to implement the full ifTable for
   bit- and character-oriented sub-layers.

   A rejected solution to this problem would be to split the ifTable
   into two (or more) new MIB tables, one of which would contain objects
   that are relevant only to packet-oriented interfaces (e.g., PPP), and
   another that may be used by all interfaces.  This is highly
   undesirable since it would require changes in every agent
   implementing the ifTable (i.e., just about every existing SNMP
   agent).

   The solution adopted in this memo builds upon the fact that
   compliance statements in SMIv2 (in contrast to SMIv1) refer to object
   groups, where object groups are explicitly defined by listing the
   objects they contain.  Thus, with SMIv2, multiple compliance
   statements can be specified, one for all interfaces and additional
   ones for specific types of interfaces.  The separate compliance
   statements can be based on separate object groups, where the object
   group for all interfaces can contain only those objects from the
   ifTable which are appropriate for every type of interfaces.  Using
   this solution, every sub-layer can have its own conceptual row in the
   ifTable.

   Thus, section 6 of this memo contains definitions of the objects of
   the existing 'interfaces' group of MIB-II, in a manner which is both
   SNMPv2-compliant and semantically-equivalent to the existing MIB-II
   definitions.  With equivalent semantics, and with the BER ("on the



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   wire") encodings unchanged, these definitions retain the same OBJECT
   IDENTIFIER values as assigned by MIB-II.  Thus, in general, no
   rewrite of existing agents which conform to MIB-II and the
   ifExtensions MIB is required.

   In addition, this memo defines several object groups for the purposes
   of defining which objects apply to which types of interface:

   (1)   the ifGeneralInformationGroup.  This group contains those
         objects applicable to all types of network interfaces,
         including bit-oriented interfaces.

   (2)   the ifPacketGroup.  This group contains those objects
         applicable to packet-oriented network interfaces.

   (3)   the ifFixedLengthGroup.  This group contains the objects
         applicable not only to character-oriented interfaces, such as
         RS-232, but also to those subnetwork technologies, such as
         cell-relay/ATM, which transmit data in fixed length
         transmission units.  As well as the octet counters, there are
         also a few other counters (e.g., the error counters) which are
         useful for this type of interface, but are currently defined as
         being packet-oriented.  To accommodate this, the definitions of
         these counters are generalized to apply to character-oriented
         interfaces and fixed-length-transmission interfaces.

   It should be noted that the octet counters in the ifTable aggregate
   octet counts for unicast and non-unicast packets into a single octet
   counter per direction (received/transmitted).  Thus, with the above
   definition of fixed-length-transmission interfaces, where such
   interfaces which support non-unicast packets, separate counts of
   unicast and multicast/broadcast transmissions can only be maintained
   in a media-specific MIB module.

3.1.5.  Interface Numbering

   MIB-II defines an object, ifNumber, whose value represents:

      "The number of network interfaces (regardless of their
      current state) present on this system."

   Each interface is identified by a unique value of the ifIndex object,
   and the description of ifIndex constrains its value as follows:

      "Its value ranges between 1 and the value of ifNumber.  The
      value for each interface must remain constant at least from
      one re-initialization of the entity's network management
      system to the next re-initialization."



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   This constancy requirement on the value of ifIndex for a particular
   interface is vital for efficient management.  However, an increasing
   number of devices allow for the dynamic addition/removal of network
   interfaces.  One example of this is a dynamic ability to configure
   the use of SLIP/PPP over a character-oriented port.  For such dynamic
   additions/removals, the combination of the constancy requirement and
   the restriction that the value of ifIndex is less than ifNumber is
   problematic.

   Redefining ifNumber to be the largest value of ifIndex was rejected
   since it would not help.  Such a re-definition would require ifNumber
   to be deprecated and the utility of the redefined object would be
   questionable.  Alternatively, ifNumber could be deprecated and not
   replaced.  However, the deprecation of ifNumber would require a
   change to that portion of ifIndex's definition which refers to
   ifNumber.  So, since the definition of ifIndex must be changed anyway
   in order to solve the problem, changes to ifNumber do not benefit the
   solution.

   The solution adopted in this memo is just to delete the requirement
   that the value of ifIndex must be less than the value of ifNumber,
   and to retain ifNumber with its current definition.  This is a minor
   change in the semantics of ifIndex; however, all existing agent
   implementations conform to this new definition, and in the interests
   of not requiring changes to existing agent implementations and to the
   many existing media-specific MIBs, this memo assumes that this change
   does not require ifIndex to be deprecated.  Experience indicates that
   this assumption does "break" a few management applications, but this
   is considered preferable to breaking all agent implementations.

   This solution also results in the possibility of "holes" in the
   ifTable, i.e., the ifIndex values of conceptual rows in the ifTable
   are not necessarily contiguous, but SNMP's GetNext (and GetBulk)
   operation easily deals with such holes.  The value of ifNumber still
   represents the number of conceptual rows, which increases/decreases
   as new interfaces are dynamically added/removed.

   The requirement for constancy (between re-initializations) of an
   interface's ifIndex value is met by requiring that after an interface
   is dynamically removed, its ifIndex value is not re-used by a
   *different* dynamically added interface until after the following
   re-initialization of the network management system.  This avoids the
   need for assignment (in advance) of ifIndex values for all possible
   interfaces that might be added dynamically.  The exact meaning of a
   "different" interface is hard to define, and there will be gray
   areas.  Any firm definition in this document would likely turn out to
   be inadequate.  Instead, implementors must choose what it means in
   their particular situation, subject to the following rules:



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   (1)   a previously-unused value of ifIndex must be assigned to a
         dynamically added interface if an agent has no knowledge of
         whether the interface is the "same" or "different" to a
         previously incarnated interface.

   (2)   a management station, not noticing that an interface has gone
         away and another has come into existence, must not be confused
         when calculating the difference between the counter values
         retrieved on successive polls for a particular ifIndex value.

   When the new interface is the same as an old interface, but a
   discontinuity in the value of the interface's counters cannot be
   avoided, the ifTable has (until now) required that a new ifIndex
   value be assigned to the returning interface.  That is, either all
   counter values have had to be retained during the absence of an
   interface in order to use the same ifIndex value on that interface's
   return, or else a new ifIndex value has had to be assigned to the
   returning interface.  Both alternatives have proved to be burdensome
   to some implementations:

   (1)   maintaining the counter values may not be possible (e.g., if
         they are maintained on removable hardware),

   (2)   using a new ifIndex value presents extra work for management
         applications.  While the potential need for such extra work is
         unavoidable on agent re-initializations, it is desirable to
         avoid it between re-initializations.

   To address this, a new object, ifCounterDiscontinuityTime, has been
   defined to record the time of the last discontinuity in an
   interface's counters.  By monitoring the value of this new object, a
   management application can now detect counter discontinuities without
   the ifIndex value of the interface being changed.  Thus, an agent
   which implements this new object should, when a new interface is the
   same as an old interface, retain that interface's ifIndex value and
   update if necessary the interface's value of
   ifCounterDiscontinuityTime.  With this new object, a management
   application must, when calculating differences between counter values
   retrieved on successive polls, discard any calculated difference for
   which the value of ifCounterDiscontinuityTime is different for the
   two polls.  (Note that this test must be performed in addition to the
   normal checking of sysUpTime to detect an agent re-initialization.)
   Since such discards are a waste of network management processing and
   bandwidth, an agent should not update the value of
   ifCounterDiscontinuityTime unless absolutely necessary.

   While defining this new object is a change in the semantics of the
   ifTable counter objects, it is impractical to deprecate and redefine



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   all these counters because of their wide deployment and importance.
   Also, a survey of implementations indicates that many agents and
   management applications do not correctly implement this aspect of the
   current semantics (because of the burdensome issues mentioned above),
   such that the practical implications of such a change is small.
   Thus, this breach of the SMI's rules is considered to be acceptable.

   Note, however, that the addition of ifCounterDiscontinuityTime does
   not change the fact that:

      it is necessary at certain times for the assignment of
      ifIndex values to change on a re-initialization of the agent
      (such as a reboot).

   The possibility of ifIndex value re-assignment must be accommodated
   by a management application whenever the value of sysUpTime is reset
   to zero.

   Note also that some agents support multiple "naming scopes", e.g.,
   for an SNMPv1 agent, multiple values of the SNMPv1 community string.
   For such an agent (e.g., a CNM agent which supports a different
   subset of interfaces for different customers), there is no required
   relationship between the ifIndex values which identify interfaces in
   one naming scope and those which identify interfaces in another
   naming scope.  It is the agent's choice as to whether the same or
   different ifIndex values identify the same or different interfaces in
   different naming scopes.

   Because of the restriction of the value of ifIndex to be less than
   ifNumber, interfaces have been numbered with small integer values.
   This has led to the ability by humans to use the ifIndex values as
   (somewhat) user-friendly names for network interfaces (e.g.,
   "interface number 3").  With the relaxation of the restriction on the
   value of ifIndex, there is now the possibility that ifIndex values
   could be assigned as very large numbers (e.g., memory addresses).
   Such numbers would be much less user-friendly.  Therefore, this memo
   recommends that ifIndex values still be assigned as (relatively)
   small integer values starting at 1, even though the values in use at
   any one time are not necessarily contiguous.  (Note that this makes
   remembering which values have been assigned easy for agents which
   dynamically add new interfaces)

   A new problem is introduced by representing each sub-layer as an
   ifTable entry.  Previously, there usually was a simple, direct,
   mapping of interfaces to the physical ports on systems.  This mapping
   would be based on the ifIndex value.  However, by having an ifTable
   entry for each interface sub-layer, mapping from interfaces to
   physical ports becomes increasingly problematic.



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   To address this issue, a new object, ifName, is added to the MIB.
   This object contains the device's local name (e.g., the name used at
   the device's local console) for the interface of which the relevant
   entry in the ifTable is a component.  For example, consider a router
   having an interface composed of PPP running over an RS-232 port.  If
   the router uses the name "wan1" for the (combined) interface, then
   the ifName objects for the corresponding PPP and RS-232 entries in
   the ifTable would both have the value "wan1".  On the other hand, if
   the router uses the name "wan1.1" for the PPP interface and "wan1.2"
   for the RS-232 port, then the ifName objects for the corresponding
   PPP and RS-232 entries in the ifTable would have the values "wan1.1"
   and "wan1.2", respectively.  As an another example, consider an agent
   which responds to SNMP queries concerning an interface on some other
   (proxied) device:  if such a proxied device associates a particular
   identifier with an interface, then it is appropriate to use this
   identifier as the value of the interface's ifName, since the local
   console in this case is that of the proxied device.

   In contrast, the existing ifDescr object is intended to contain a
   description of an interface, whereas another new object, ifAlias,
   provides a location in which a network management application can
   store a non-volatile interface-naming value of its own choice.  The
   ifAlias object allows a network manager to give one or more
   interfaces their own unique names, irrespective of any interface-
   stack relationship.  Further, the ifAlias name is non-volatile, and
   thus an interface must retain its assigned ifAlias value across
   reboots, even if an agent chooses a new ifIndex value for the
   interface.

3.1.6.  Counter Size

   As the speed of network media increase, the minimum time in which a
   32 bit counter will wrap decreases.  For example, a 10Mbs stream of
   back-to-back, full-size packets causes ifInOctets to wrap in just
   over 57 minutes; at 100Mbs, the minimum wrap time is 5.7 minutes, and
   at 1Gbs, the minimum is 34 seconds.  Requiring that interfaces be
   polled frequently enough not to miss a counter wrap is increasingly
   problematic.

   A rejected solution to this problem was to scale the counters; for
   example, ifInOctets could be changed to count received octets in,
   say, 1024 byte blocks.  While it would provide acceptable
   functionality at high rates of the counted-events, at low rates it
   suffers.  If there is little traffic on an interface, there might be
   a significant interval before enough of the counted-events occur to
   cause the scaled counter to be incremented.  Traffic would then
   appear to be very bursty, leading to incorrect conclusions of the
   network's performance.



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   Instead, this memo adopts expanded, 64 bit, counters.  These counters
   are provided in new "high capacity" groups.  The old, 32-bit,
   counters have not been deprecated.  The 64-bit counters are to be
   used only when the 32-bit counters do not provide enough capacity;
   that is, when the 32 bit counters could wrap too fast.

   For interfaces that operate at 20,000,000 (20 million) bits per
   second or less, 32-bit byte and packet counters MUST be supported.
   For interfaces that operate faster than 20,000,000 bits/second, and
   slower than 650,000,000 bits/second, 32-bit packet counters MUST be
   supported and 64-bit octet counters MUST be supported.  For
   interfaces that operate at 650,000,000 bits/second or faster, 64-bit
   packet counters AND 64-bit octet counters MUST be supported.

   These speed thresholds were chosen as reasonable compromises based on
   the following:

   (1)   The cost of maintaining 64-bit counters is relatively high, so
         minimizing the number of agents which must support them is
         desirable.  Common interfaces (such as 10Mbs Ethernet) should
         not require them.

   (2)   64-bit counters are a new feature, introduced in the SMIv2.  It
         is reasonable to expect that support for them will be spotty
         for the immediate future.  Thus, we wish to limit them to as
         few systems as possible.  This, in effect, means that 64-bit
         counters should be limited to higher speed interfaces.
         Ethernet (10,000,000 bps) and Token Ring (16,000,000 bps) are
         fairly wide-spread so it seems reasonable to not require 64-bit
         counters for these interfaces.

   (3)   The 32-bit octet counters will wrap in the following times, for
         the following interfaces (when transmitting maximum-sized
         packets back-to-back):

         -   10Mbs Ethernet: 57 minutes,

         -   16Mbs Token Ring: 36 minutes,

         -   a US T3 line (45 megabits): 12 minutes,

         -   FDDI: 5.7 minutes

   (4)   The 32-bit packet counters wrap in about 57 minutes when 64-
         byte packets are transmitted back-to-back on a 650,000,000
         bit/second link.





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   As an aside, a 1-terabit/second (1,000 Gbs) link will cause a 64 bit
   octet counter to wrap in just under 5 years.  Conversely, an
   81,000,000 terabit/second link is required to cause a 64-bit counter
   to wrap in 30 minutes.  We believe that, while technology rapidly
   marches forward, this link speed will not be achieved for at least
   several years, leaving sufficient time to evaluate the introduction
   of 96 bit counters.

   When 64-bit counters are in use, the 32-bit counters MUST still be
   available.  They will report the low 32-bits of the associated 64-bit
   count (e.g., ifInOctets will report the least significant 32 bits of
   ifHCInOctets).  This enhances inter-operability with existing
   implementations at a very minimal cost to agents.

   The new "high capacity" groups are:

   (1)   the ifHCFixedLengthGroup for character-oriented/fixed-length
         interfaces, and the ifHCPacketGroup for packet-based
         interfaces; both of these groups include 64 bit counters for
         octets, and

   (2)   the ifVHCPacketGroup for packet-based interfaces; this group
         includes 64 bit counters for octets and packets.

3.1.7.  Interface Speed

   Network speeds are increasing.  The range of ifSpeed is limited to
   reporting a maximum speed of (2**31)-1 bits/second, or approximately
   2.2Gbs.  SONET defines an OC-48 interface, which is defined at
   operating at 48 times 51 Mbs, which is a speed in excess of 2.4Gbs.
   Thus, ifSpeed is insufficient for the future, and this memo defines
   an additional object: ifHighSpeed.

   The ifHighSpeed object reports the speed of the interface in
   1,000,000 (1 million) bits/second units.  Thus, the true speed of the
   interface will be the value reported by this object, plus or minus
   500,000 bits/second.

   Other alternatives considered (but rejected) were:

   (1)   Making the interface speed a 64-bit gauge.  This was rejected
         since the current SMI does not allow such a syntax.

      Furthermore, even if 64-bit gauges were available, their use would
      require additional complexity in agents due to an increased
      requirement for 64-bit operations.





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   (2)   We also considered making "high-32 bit" and "low-32-bit"
         objects which, when combined, would be a 64-bit value.  This
         simply seemed overly complex for what we are trying to do.

      Furthermore, a full 64-bits of precision does not seem necessary.
      The value of ifHighSpeed will be the only report of interface
      speed for interfaces that are faster than 4,294,967,295 bits per
      second.  At this speed, the granularity of ifHighSpeed will be
      1,000,000 bits per second, thus the error will be 1/4294, or about
      0.02%.  This seems reasonable.

   (3)   Adding a "scale" object, which would define the units which
         ifSpeed's value is.

      This would require two additional objects; one for the scaling
      object, and one to replace the current ifSpeed.  This later object
      is required since the semantics of ifSpeed would be significantly
      altered, and manager stations which do not understand the new
      semantics would be confused.

3.1.8.  Multicast/Broadcast Counters

   In MIB-II, the ifTable counters for multicast and broadcast packets
   are combined as counters of non-unicast packets.  In contrast, the
   ifExtensions MIB [19] defined one set of counters for multicast, and
   a separate set for broadcast packets.  With the separate counters,
   the original combined counters become redundant.  To avoid this
   redundancy, the non-unicast counters are deprecated.

   For the output broadcast and multicast counters defined in RFC 1229,
   their definitions varied slightly from the packet counters in the
   ifTable, in that they did not count errors/discarded packets.  Thus,
   this memo defines new objects with better aligned definitions.
   Counters with 64 bits of range are also needed, as explained above.

3.1.9.  Trap Enable

   In the multi-layer interface model, each sub-layer for which there is
   an entry in the ifTable can generate linkUp/linkDown Traps.  Since
   interface state changes would tend to propagate through the interface
   (from top to bottom, or bottom to top), it is likely that several
   traps would be generated for each linkUp/linkDown occurrence.

   It is desirable to provide a mechanism for manager stations to
   control the generation of these traps.  To this end, the
   ifLinkUpDownTrapEnable object has been added.  This object allows
   managers to limit generation of traps to just the sub-layers of
   interest.



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   The default setting should limit the number of traps generated to one
   per interface per linkUp/linkDown event.  Furthermore, it seems that
   the state changes of most interest to network managers occur at the
   lowest level of an interface stack.  Therefore we specify that by
   default, only the lowest sub-layer of the interface generate traps.

3.1.10.  Addition of New ifType values

   Over time, there is the need to add new ifType enumerated values for
   new interface types.  If the syntax of ifType were defined in the MIB
   in section 6, then a new version of this MIB would have to be re-
   issued in order to define new values.  In the past, re-issuing of a
   MIB has occurred only after several years.

   Therefore, the syntax of ifType is changed to be a textual
   convention, such that the enumerated integer values are now defined
   in the textual convention, IANAifType, defined in a different
   document.  This allows additional values to be documented without
   having to re-issue a new version of this document.  The Internet
   Assigned Number Authority (IANA) is responsible for the assignment of
   all Internet numbers, including various SNMP-related numbers, and
   specifically, new ifType values.

3.1.11.  InterfaceIndex Textual Convention

   A new textual convention, InterfaceIndex, has been defined.  This
   textual convention "contains" all of the semantics of the ifIndex
   object.  This allows other MIB modules to easily import the semantics
   of ifIndex.

3.1.12.  New states for IfOperStatus

   Three new states have been added to ifOperStatus: 'dormant',
   'notPresent', and 'lowerLayerDown'.

   The dormant state indicates that the relevant interface is not
   actually in a condition to pass packets (i.e., it is not 'up') but is
   in a "pending" state, waiting for some external event.  For "on-
   demand" interfaces, this new state identifies the situation where the
   interface is waiting for events to place it in the up state.
   Examples of such events might be:

   (1)   having packets to transmit before establishing a connection to
         a remote system;

   (2)   having a remote system establish a connection to the interface
         (e.g. dialing up to a slip-server).




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   The notPresent state is a refinement on the down state which
   indicates that the relevant interface is down specifically because
   some component (typically, a hardware component) is not present in
   the managed system.  Examples of use of the notPresent state are:

   (1)   to allow an interface's conceptual row including its counter
         values to be retained across a "hot swap" of a card/module,
         and/or

   (2)   to allow an interface's conceptual row to be created, and
         thereby enable interfaces to be pre-configured prior to
         installation of the hardware needed to make the interface
         operational.

   Agents are not required to support interfaces in the notPresent
   state.  However, from a conceptual viewpoint, when a row in the
   ifTable is created, it first enters the notPresent state and then
   subsequently transitions into the down state; similarly, when a row
   in the ifTable is deleted, it first enters the notPresent state and
   then subsequently the object instances are deleted.  For an agent
   with no support for notPresent, both of these transitions (from the
   notPresent state to the down state, and from the notPresent state to
   the instances being removed) are immediate, i.e., the transition does
   not last long enough to be recorded by ifOperStatus.  Even for those
   agents which do support interfaces in the notPresent state, the
   length of time and conditions under which an interface stays in the
   notPresent state is implementation-specific.

   The lowerLayerDown state is also a refinement on the down state.
   This new state indicates that this interface runs "on top of" one or
   more other interfaces (see ifStackTable) and that this interface is
   down specifically because one or more of these lower-layer interfaces
   are down.

3.1.13.  IfAdminStatus and IfOperStatus

   The down state of ifOperStatus now has two meanings, depending on the
   value of ifAdminStatus.

   (1)   if ifAdminStatus is not down and ifOperStatus is down then a
         fault condition is presumed to exist on the interface.

   (2)   if ifAdminStatus is down, then ifOperStatus will normally also
         be down (or notPresent) i.e., there is not (necessarily) a
         fault condition on the interface.

   Note that when ifAdminStatus transitions to down, ifOperStatus will
   normally also transition to down.  In this situation, it is possible



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   that ifOperStatus's transition will not occur immediately, but rather
   after a small time lag to complete certain operations before going
   "down"; for example, it might need to finish transmitting a packet.
   If a manager station finds that ifAdminStatus is down and
   ifOperStatus is not down for a particular interface, the manager
   station should wait a short while and check again.  If the condition
   still exists, only then should it raise an error indication.
   Naturally, it should also ensure that ifLastChange has not changed
   during this interval.

   Whenever an interface table entry is created (usually as a result of
   system initialization), the relevant instance of ifAdminStatus is set
   to down, and ifOperStatus will be down or notPresent.

   An interface may be enabled in two ways: either as a result of
   explicit management action (e.g. setting ifAdminStatus to up) or as a
   result of the managed system's initialization process.  When
   ifAdminStatus changes to the up state, the related ifOperStatus
   should do one of the following:

   (1)   Change to the up state if and only if the interface is able to
         send and receive packets.

   (2)   Change to the lowerLayerDown state if and only if the interface
         is prevented from entering the up state because of the state of
         one or more of the interfaces beneath it in the interface
         stack.

   (3)   Change to the dormant state if and only if the interface is
         found to be operable, but the interface is waiting for other,
         external, events to occur before it can transmit or receive
         packets.  Presumably when the expected events occur, the
         interface will then change to the up state.

   (4)   Remain in the down state if an error or other fault condition
         is detected on the interface.

   (5)   Change to the unknown state if, for some reason, the state of
         the interface can not be ascertained.

   (6)   Change to the testing state if some test(s) must be performed
         on the interface. Presumably after completion of the test, the
         interface's state will change to up, dormant, or down, as
         appropriate.

   (7)   Remain in the notPresent state if interface components are
         missing.




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3.1.14.  IfOperStatus in an Interface Stack

   When an interface is a part of an interface-stack, but is not the
   lowest interface in the stack, then:

   (1)   ifOperStatus has the value 'up' if it is able to pass packets
         due to one or more interfaces below it in the stack being 'up',
         irrespective of whether other interfaces below it are 'down', '
         dormant', 'notPresent', 'lowerLayerDown', 'unknown' or '
         testing'.

   (2)   ifOperStatus may have the value 'up' or 'dormant' if one or
         more interfaces below it in the stack are 'dormant', and all
         others below it are either 'down', 'dormant', 'notPresent', '
         lowerLayerDown', 'unknown' or 'testing'.

   (3)   ifOperStatus has the value 'lowerLayerDown' while all
         interfaces below it in the stack are either 'down', '
         notPresent', 'lowerLayerDown', or 'testing'.

3.1.15.  Traps

   The exact definition of when linkUp and linkDown traps are generated
   has been changed to reflect the changes to ifAdminStatus and
   ifOperStatus.  Operational experience indicates that management
   stations are most concerned with an interface being in the down state
   and the fact that this state may indicate a failure.  Thus, it is
   most useful to instrument transitions into/out of either the up state
   or the down state.

   Instrumenting transitions into or out of the up state was rejected
   since it would have the drawback that a demand interface might have
   many transitions between up and dormant, leading to many linkUp traps
   and no linkDown traps.  Furthermore, if a node's only interface is
   the demand interface, then a transition to dormant would entail
   generation of a linkDown trap, necessitating bringing the link to the
   up state (and a linkUp trap)!!

   On the other hand, instrumenting transitions into or out of the down
   state (to/from all other states except notPresent) has the
   advantages:

   (1)   A transition into the down state (from a state other than
         notPresent) will occur when an error is detected on an
         interface.  Error conditions are presumably of great interest
         to network managers.





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   (2)   Departing the down state (to a state other than the notPresent
         state) generally indicates that the interface is going to
         either up or dormant, both of which are considered "healthy"
         states.

   Furthermore, it is believed that generating traps on transitions into
   or out of the down state (except to/from the notPresent state) is
   generally consistent with current usage and interpretation of these
   traps by manager stations.

   Transitions to/from the notPresent state are concerned with the
   insertion and removal of hardware, and are outside the scope of these
   traps.

   Therefore, this memo defines that LinkUp and linkDown traps are
   generated just after ifOperStatus leaves, or just before it enters,
   the down state, respectively; except that LinkUp and linkDown traps
   are never generated on transitions to/from the notPresent state.  For
   the purpose of deciding when these traps occur, the lowerLayerDown
   state and the down state are considered to be equivalent, i.e., there
   is no trap on transition from lowerLayerDown into down, and there is
   a trap on transition from any other state except down (and
   notPresent) into lowerLayerDown.

   Note that this definition allows a node with only one interface to
   transmit a linkDown trap before that interface goes down.  (Of
   course, when the interface is going down because of a failure
   condition, the linkDown trap probably cannot be successfully
   transmitted anyway.)

   Some interfaces perform a link "training" function when trying to
   bring the interface up.  In the event that such an interface were
   defective, then the training function would fail and the interface
   would remain down, and the training function might be repeated at
   appropriate intervals.  If the interface, while performing this
   training function, were considered to the in the testing state, then
   linkUp and linkDown traps would be generated for each start and end
   of the training function.  This is not the intent of the linkUp and
   linkDown traps, and therefore, while performing such a training
   function, the interface's state should be represented as down.

   An exception to the above generation of linkUp/linkDown traps on
   changes in ifOperStatus, occurs when an interface is "flapping",
   i.e., when it is rapidly oscillating between the up and down states.
   If traps were generated for each such oscillation, the network and
   the network management system would be flooded with unnecessary
   traps.  In such a situation, the agent should limit the rate at which
   it generates traps.



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3.1.16.  ifSpecific

   The original definition of the OBJECT IDENTIFIER value of ifSpecific
   was not sufficiently clear.  As a result, different implementors used
   it differently, and confusion resulted.  Some implementations set the
   value of ifSpecific to the OBJECT IDENTIFIER that defines the media-
   specific MIB, i.e., the "foo" of:
                foo OBJECT IDENTIFIER ::= { transmission xxx }

   while others set it to be OBJECT IDENTIFIER of the specific table or
   entry in the appropriate media-specific MIB (i.e., fooTable or
   fooEntry), while still others set it be the OBJECT IDENTIFIER of the
   index object of the table's row, including instance identifier,
   (i.e., fooIfIndex.ifIndex).  A definition based on the latter would
   not be sufficient unless it also allowed for media-specific MIBs
   which include several tables, where each table has its own
   (different) indexing.

   The only definition that can both be made explicit and can cover all
   the useful situations is to have ifSpecific be the most general value
   for the media-specific MIB module (the first example given above).
   This effectively makes it redundant because it contains no more
   information than is provided by ifType.  Thus, ifSpecific has been
   deprecated.

3.1.17.  Creation/Deletion of Interfaces

   While some interfaces, for example, most physical interfaces, cannot
   be created via network management, other interfaces such as logical
   interfaces sometimes can be.  The ifTable contains only generic
   information about an interface.  Almost all 'create-able' interfaces
   have other, media-specific, information through which configuration
   parameters may be supplied prior to creating such an interface.
   Thus, the ifTable does not itself support the creation or deletion of
   an interface (specifically, it has no RowStatus [6] column).  Rather,
   if a particular interface type supports the dynamic creation and/or
   deletion of an interface of that type, then that media-specific MIB
   should include an appropriate RowStatus object (see the ATM LAN-
   Emulation Client MIB [20] for an example of a MIB which does this).
   Typically, when such a RowStatus object is created/deleted, then the
   conceptual row in the ifTable appears/disappears as a by-product, and
   an ifIndex value (chosen by the agent) is stored in an appropriate
   object in the media-specific MIB.








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3.1.18.  All Values Must be Known

   There are a number of situations where an agent does not know the
   value of one or more objects for a particular interface.  In all such
   circumstances, an agent MUST NOT instantiate an object with an
   incorrect value; rather, it MUST respond with the appropriate
   error/exception condition (e.g., noSuchInstance or noSuchName).

   One example is where an agent is unable to count the occurrences
   defined by one (or more) of the ifTable counters.  In this
   circumstance, the agent MUST NOT instantiate the particular counter
   with a value of, say, zero.  To do so would be to provide mis-
   information to a network management application reading the zero
   value, and thereby assuming that there have been no occurrences of
   the event (e.g., no input errors because ifInErrors is always zero).

   Sometimes the lack of knowledge of an object's value is temporary.
   For example, when the MTU of an interface is a configured value and a
   device dynamically learns the configured value through (after)
   exchanging messages over the interface (e.g., ATM LAN-Emulation
   [20]).  In such a case, the value is not known until after the
   ifTable entry has already been created.  In such a case, the ifTable
   entry should be created without an instance of the object whose value
   is unknown; later, when the value becomes known, the missing object
   can then be instantiated (e.g., the instance of ifMtu is only
   instantiated once the interface's MTU becomes known).

   As a result of this "known values" rule, management applications MUST
   be able to cope with the responses to retrieving the object instances
   within a conceptual row of the ifTable revealing that some of the
   row's columnar objects are missing/not available.

4.  Media-Specific MIB Applicability

   The exact use and semantics of many objects in this MIB are open to
   some interpretation.  This is a result of the generic nature of this
   MIB.  It is not always possible to come up with specific,
   unambiguous, text that covers all cases and yet preserves the generic
   nature of the MIB.

   Therefore, it is incumbent upon a media-specific MIB designer to,
   wherever necessary, clarify the use of the objects in this MIB with
   respect to the media-specific MIB.








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   Specific areas of clarification include

   Layering Model
      The media-specific MIB designer MUST completely and unambiguously
      specify the layering model used.  Each individual sub-layer must
      be identified, as must the ifStackTable's portrayal of the
      relationship(s) between the sub-layers.

   Virtual Circuits
      The media-specific MIB designer MUST specify whether virtual
      circuits are assigned entries in the ifTable or not.  If they are,
      compelling rationale must be presented.

   ifRcvAddressTable
      The media-specific MIB designer MUST specify the applicability of
      the ifRcvAddressTable.

   ifType
      For each of the ifType values to which the media-specific MIB
      applies, it must specify the mapping of ifType values to media-
      specific MIB module(s) and instances of MIB objects within those
      modules.

   ifXxxOctets
      The definitions of ifInOctets and ifOutOctets (and similarly,
      ifHCInOctets and ifHCOutOctets) specify that their values include
      framing characters.  The media-specific MIB designer MUST specify
      any special conditions of the media concerning the inclusion of
      framing characters, especially with respect to frames with errors.

   However, wherever this interface MIB is specific in the semantics,
   DESCRIPTION, or applicability of objects, the media-specific MIB
   designer MUST NOT change said semantics, DESCRIPTION, or
   applicability.

5.  Overview

   This MIB consists of 4 tables:

   ifTable
      This table is the ifTable from MIB-II.

   ifXTable
      This table contains objects that have been added to the Interface
      MIB as a result of the Interface Evolution effort, or replacements
      for objects of the original (MIB-II) ifTable that were deprecated





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      because the semantics of said objects have significantly changed.
      This table also contains objects that were previously in the
      ifExtnsTable.

   ifStackTable
      This table contains objects that define the relationships among
      the sub-layers of an interface.

   ifRcvAddressTable
      This table contains objects that are used to define the media-
      level addresses which this interface will receive.  This table is
      a generic table.  The designers of media-specific MIBs must define
      exactly how this table applies to their specific MIB.

6.  Interfaces Group Definitions

IF-MIB DEFINITIONS ::= BEGIN

IMPORTS
    MODULE-IDENTITY, OBJECT-TYPE, Counter32, Gauge32, Counter64,
    Integer32, TimeTicks, mib-2,
    NOTIFICATION-TYPE                        FROM SNMPv2-SMI
    TEXTUAL-CONVENTION, DisplayString,
    PhysAddress, TruthValue, RowStatus,
    TimeStamp, AutonomousType, TestAndIncr   FROM SNMPv2-TC
    MODULE-COMPLIANCE, OBJECT-GROUP,
    NOTIFICATION-GROUP                       FROM SNMPv2-CONF
    snmpTraps                                FROM SNMPv2-MIB
    IANAifType                               FROM IANAifType-MIB;


ifMIB MODULE-IDENTITY
    LAST-UPDATED "200006140000Z"
    ORGANIZATION "IETF Interfaces MIB Working Group"
    CONTACT-INFO
            "   Keith McCloghrie
                Cisco Systems, Inc.
                170 West Tasman Drive
                San Jose, CA  95134-1706
                US

                408-526-5260
                kzm@cisco.com"
    DESCRIPTION
            "The MIB module to describe generic objects for network
            interface sub-layers.  This MIB is an updated version of
            MIB-II's ifTable, and incorporates the extensions defined in
            RFC 1229."



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    REVISION      "200006140000Z"
    DESCRIPTION
            "Clarifications agreed upon by the Interfaces MIB WG, and
            published as RFC 2863."
    REVISION      "199602282155Z"
    DESCRIPTION
            "Revisions made by the Interfaces MIB WG, and published in
            RFC 2233."
    REVISION      "199311082155Z"
    DESCRIPTION
            "Initial revision, published as part of RFC 1573."
    ::= { mib-2 31 }


ifMIBObjects OBJECT IDENTIFIER ::= { ifMIB 1 }

interfaces   OBJECT IDENTIFIER ::= { mib-2 2 }

--
-- Textual Conventions
--


-- OwnerString has the same semantics as used in RFC 1271

OwnerString ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "255a"
    STATUS       deprecated
    DESCRIPTION
            "This data type is used to model an administratively
            assigned name of the owner of a resource.  This information
            is taken from the NVT ASCII character set.  It is suggested
            that this name contain one or more of the following: ASCII
            form of the manager station's transport address, management
            station name (e.g., domain name), network management
            personnel's name, location, or phone number.  In some cases
            the agent itself will be the owner of an entry.  In these
            cases, this string shall be set to a string starting with
            'agent'."
    SYNTAX       OCTET STRING (SIZE(0..255))

-- InterfaceIndex contains the semantics of ifIndex and should be used
-- for any objects defined in other MIB modules that need these semantics.

InterfaceIndex ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "d"
    STATUS       current
    DESCRIPTION



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            "A unique value, greater than zero, for each interface or
            interface sub-layer in the managed system.  It is
            recommended that values are assigned contiguously starting
            from 1.  The value for each interface sub-layer must remain
            constant at least from one re-initialization of the entity's
            network management system to the next re-initialization."
    SYNTAX       Integer32 (1..2147483647)

InterfaceIndexOrZero ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "d"
    STATUS       current
    DESCRIPTION
            "This textual convention is an extension of the
            InterfaceIndex convention.  The latter defines a greater
            than zero value used to identify an interface or interface
            sub-layer in the managed system.  This extension permits the
            additional value of zero.  the value zero is object-specific
            and must therefore be defined as part of the description of
            any object which uses this syntax.  Examples of the usage of
            zero might include situations where interface was unknown,
            or when none or all interfaces need to be referenced."
    SYNTAX       Integer32 (0..2147483647)

ifNumber  OBJECT-TYPE
    SYNTAX      Integer32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The number of network interfaces (regardless of their
            current state) present on this system."
    ::= { interfaces 1 }

ifTableLastChange  OBJECT-TYPE
    SYNTAX      TimeTicks
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The value of sysUpTime at the time of the last creation or
            deletion of an entry in the ifTable.  If the number of
            entries has been unchanged since the last re-initialization
            of the local network management subsystem, then this object
            contains a zero value."
    ::= { ifMIBObjects 5 }


-- the Interfaces table

-- The Interfaces table contains information on the entity's



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-- interfaces.  Each sub-layer below the internetwork-layer
-- of a network interface is considered to be an interface.

ifTable OBJECT-TYPE
    SYNTAX      SEQUENCE OF IfEntry
    MAX-ACCESS  not-accessible
    STATUS      current
    DESCRIPTION
            "A list of interface entries.  The number of entries is
            given by the value of ifNumber."
    ::= { interfaces 2 }

ifEntry OBJECT-TYPE
    SYNTAX      IfEntry
    MAX-ACCESS  not-accessible
    STATUS      current
    DESCRIPTION
            "An entry containing management information applicable to a
            particular interface."
    INDEX   { ifIndex }
    ::= { ifTable 1 }

IfEntry ::=
    SEQUENCE {
        ifIndex                 InterfaceIndex,
        ifDescr                 DisplayString,
        ifType                  IANAifType,
        ifMtu                   Integer32,
        ifSpeed                 Gauge32,
        ifPhysAddress           PhysAddress,
        ifAdminStatus           INTEGER,
        ifOperStatus            INTEGER,
        ifLastChange            TimeTicks,
        ifInOctets              Counter32,
        ifInUcastPkts           Counter32,
        ifInNUcastPkts          Counter32,  -- deprecated
        ifInDiscards            Counter32,
        ifInErrors              Counter32,
        ifInUnknownProtos       Counter32,
        ifOutOctets             Counter32,
        ifOutUcastPkts          Counter32,
        ifOutNUcastPkts         Counter32,  -- deprecated
        ifOutDiscards           Counter32,
        ifOutErrors             Counter32,
        ifOutQLen               Gauge32,    -- deprecated
        ifSpecific              OBJECT IDENTIFIER -- deprecated
    }




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ifIndex OBJECT-TYPE
    SYNTAX      InterfaceIndex
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "A unique value, greater than zero, for each interface.  It
            is recommended that values are assigned contiguously
            starting from 1.  The value for each interface sub-layer
            must remain constant at least from one re-initialization of
            the entity's network management system to the next re-
            initialization."
    ::= { ifEntry 1 }

ifDescr OBJECT-TYPE
    SYNTAX      DisplayString (SIZE (0..255))
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "A textual string containing information about the
            interface.  This string should include the name of the
            manufacturer, the product name and the version of the
            interface hardware/software."
    ::= { ifEntry 2 }

ifType OBJECT-TYPE
    SYNTAX      IANAifType
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The type of interface.  Additional values for ifType are
            assigned by the Internet Assigned Numbers Authority (IANA),
            through updating the syntax of the IANAifType textual
            convention."
    ::= { ifEntry 3 }

ifMtu OBJECT-TYPE
    SYNTAX      Integer32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The size of the largest packet which can be sent/received
            on the interface, specified in octets.  For interfaces that
            are used for transmitting network datagrams, this is the
            size of the largest network datagram that can be sent on the
            interface."
    ::= { ifEntry 4 }

ifSpeed OBJECT-TYPE



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    SYNTAX      Gauge32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "An estimate of the interface's current bandwidth in bits
            per second.  For interfaces which do not vary in bandwidth
            or for those where no accurate estimation can be made, this
            object should contain the nominal bandwidth.  If the
            bandwidth of the interface is greater than the maximum value
            reportable by this object then this object should report its
            maximum value (4,294,967,295) and ifHighSpeed must be used
            to report the interace's speed.  For a sub-layer which has
            no concept of bandwidth, this object should be zero."
    ::= { ifEntry 5 }

ifPhysAddress OBJECT-TYPE
    SYNTAX      PhysAddress
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The interface's address at its protocol sub-layer.  For
            example, for an 802.x interface, this object normally
            contains a MAC address.  The interface's media-specific MIB
            must define the bit and byte ordering and the format of the
            value of this object.  For interfaces which do not have such
            an address (e.g., a serial line), this object should contain
            an octet string of zero length."
    ::= { ifEntry 6 }

ifAdminStatus OBJECT-TYPE
    SYNTAX  INTEGER {
                up(1),       -- ready to pass packets
                down(2),
                testing(3)   -- in some test mode
            }
    MAX-ACCESS  read-write
    STATUS      current
    DESCRIPTION
            "The desired state of the interface.  The testing(3) state
            indicates that no operational packets can be passed.  When a
            managed system initializes, all interfaces start with
            ifAdminStatus in the down(2) state.  As a result of either
            explicit management action or per configuration information
            retained by the managed system, ifAdminStatus is then
            changed to either the up(1) or testing(3) states (or remains
            in the down(2) state)."
    ::= { ifEntry 7 }




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ifOperStatus OBJECT-TYPE
    SYNTAX  INTEGER {
                up(1),        -- ready to pass packets
                down(2),
                testing(3),   -- in some test mode
                unknown(4),   -- status can not be determined
                              -- for some reason.
                dormant(5),
                notPresent(6),    -- some component is missing
                lowerLayerDown(7) -- down due to state of
                                  -- lower-layer interface(s)
            }
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The current operational state of the interface.  The
            testing(3) state indicates that no operational packets can
            be passed.  If ifAdminStatus is down(2) then ifOperStatus
            should be down(2).  If ifAdminStatus is changed to up(1)
            then ifOperStatus should change to up(1) if the interface is
            ready to transmit and receive network traffic; it should
            change to dormant(5) if the interface is waiting for
            external actions (such as a serial line waiting for an
            incoming connection); it should remain in the down(2) state
            if and only if there is a fault that prevents it from going
            to the up(1) state; it should remain in the notPresent(6)
            state if the interface has missing (typically, hardware)
            components."
    ::= { ifEntry 8 }

ifLastChange OBJECT-TYPE
    SYNTAX      TimeTicks
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The value of sysUpTime at the time the interface entered
            its current operational state.  If the current state was
            entered prior to the last re-initialization of the local
            network management subsystem, then this object contains a
            zero value."
    ::= { ifEntry 9 }

ifInOctets OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The total number of octets received on the interface,



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            including framing characters.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifEntry 10 }

ifInUcastPkts OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The number of packets, delivered by this sub-layer to a
            higher (sub-)layer, which were not addressed to a multicast
            or broadcast address at this sub-layer.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifEntry 11 }

ifInNUcastPkts OBJECT-TYPE
    SYNTAX  Counter32
    MAX-ACCESS  read-only
    STATUS      deprecated
    DESCRIPTION
            "The number of packets, delivered by this sub-layer to a
            higher (sub-)layer, which were addressed to a multicast or
            broadcast address at this sub-layer.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime.

            This object is deprecated in favour of ifInMulticastPkts and
            ifInBroadcastPkts."
    ::= { ifEntry 12 }

ifInDiscards OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The number of inbound packets which were chosen to be
            discarded even though no errors had been detected to prevent



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            their being deliverable to a higher-layer protocol.  One
            possible reason for discarding such a packet could be to
            free up buffer space.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifEntry 13 }

ifInErrors OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "For packet-oriented interfaces, the number of inbound
            packets that contained errors preventing them from being
            deliverable to a higher-layer protocol.  For character-
            oriented or fixed-length interfaces, the number of inbound
            transmission units that contained errors preventing them
            from being deliverable to a higher-layer protocol.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifEntry 14 }

ifInUnknownProtos OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "For packet-oriented interfaces, the number of packets
            received via the interface which were discarded because of
            an unknown or unsupported protocol.  For character-oriented
            or fixed-length interfaces that support protocol
            multiplexing the number of transmission units received via
            the interface which were discarded because of an unknown or
            unsupported protocol.  For any interface that does not
            support protocol multiplexing, this counter will always be
            0.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifEntry 15 }



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ifOutOctets OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The total number of octets transmitted out of the
            interface, including framing characters.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifEntry 16 }

ifOutUcastPkts OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The total number of packets that higher-level protocols
            requested be transmitted, and which were not addressed to a
            multicast or broadcast address at this sub-layer, including
            those that were discarded or not sent.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifEntry 17 }

ifOutNUcastPkts OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      deprecated
    DESCRIPTION
            "The total number of packets that higher-level protocols
            requested be transmitted, and which were addressed to a
            multicast or broadcast address at this sub-layer, including
            those that were discarded or not sent.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime.

            This object is deprecated in favour of ifOutMulticastPkts
            and ifOutBroadcastPkts."
    ::= { ifEntry 18 }



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ifOutDiscards OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The number of outbound packets which were chosen to be
            discarded even though no errors had been detected to prevent
            their being transmitted.  One possible reason for discarding
            such a packet could be to free up buffer space.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifEntry 19 }

ifOutErrors OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "For packet-oriented interfaces, the number of outbound
            packets that could not be transmitted because of errors.
            For character-oriented or fixed-length interfaces, the
            number of outbound transmission units that could not be
            transmitted because of errors.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifEntry 20 }

ifOutQLen OBJECT-TYPE
    SYNTAX      Gauge32
    MAX-ACCESS  read-only
    STATUS      deprecated
    DESCRIPTION
            "The length of the output packet queue (in packets)."
    ::= { ifEntry 21 }

ifSpecific OBJECT-TYPE
    SYNTAX      OBJECT IDENTIFIER
    MAX-ACCESS  read-only
    STATUS      deprecated
    DESCRIPTION
            "A reference to MIB definitions specific to the particular
            media being used to realize the interface.  It is



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            recommended that this value point to an instance of a MIB
            object in the media-specific MIB, i.e., that this object
            have the semantics associated with the InstancePointer
            textual convention defined in RFC 2579.  In fact, it is
            recommended that the media-specific MIB specify what value
            ifSpecific should/can take for values of ifType.  If no MIB
            definitions specific to the particular media are available,
            the value should be set to the OBJECT IDENTIFIER { 0 0 }."
    ::= { ifEntry 22 }



--
--   Extension to the interface table
--
-- This table replaces the ifExtnsTable table.
--

ifXTable        OBJECT-TYPE
    SYNTAX      SEQUENCE OF IfXEntry
    MAX-ACCESS  not-accessible
    STATUS      current
    DESCRIPTION
            "A list of interface entries.  The number of entries is
            given by the value of ifNumber.  This table contains
            additional objects for the interface table."
    ::= { ifMIBObjects 1 }

ifXEntry        OBJECT-TYPE
    SYNTAX      IfXEntry
    MAX-ACCESS  not-accessible
    STATUS      current
    DESCRIPTION
            "An entry containing additional management information
            applicable to a particular interface."
    AUGMENTS    { ifEntry }
    ::= { ifXTable 1 }

IfXEntry ::=
    SEQUENCE {
        ifName                  DisplayString,
        ifInMulticastPkts       Counter32,
        ifInBroadcastPkts       Counter32,
        ifOutMulticastPkts      Counter32,
        ifOutBroadcastPkts      Counter32,
        ifHCInOctets            Counter64,
        ifHCInUcastPkts         Counter64,
        ifHCInMulticastPkts     Counter64,



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        ifHCInBroadcastPkts     Counter64,
        ifHCOutOctets           Counter64,
        ifHCOutUcastPkts        Counter64,
        ifHCOutMulticastPkts    Counter64,
        ifHCOutBroadcastPkts    Counter64,
        ifLinkUpDownTrapEnable  INTEGER,
        ifHighSpeed             Gauge32,
        ifPromiscuousMode       TruthValue,
        ifConnectorPresent      TruthValue,
        ifAlias                 DisplayString,
        ifCounterDiscontinuityTime TimeStamp
    }


ifName OBJECT-TYPE
    SYNTAX      DisplayString
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The textual name of the interface.  The value of this
            object should be the name of the interface as assigned by
            the local device and should be suitable for use in commands
            entered at the device's `console'.  This might be a text
            name, such as `le0' or a simple port number, such as `1',
            depending on the interface naming syntax of the device.  If
            several entries in the ifTable together represent a single
            interface as named by the device, then each will have the
            same value of ifName.  Note that for an agent which responds
            to SNMP queries concerning an interface on some other
            (proxied) device, then the value of ifName for such an
            interface is the proxied device's local name for it.

            If there is no local name, or this object is otherwise not
            applicable, then this object contains a zero-length string."
    ::= { ifXEntry 1 }

ifInMulticastPkts OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The number of packets, delivered by this sub-layer to a
            higher (sub-)layer, which were addressed to a multicast
            address at this sub-layer.  For a MAC layer protocol, this
            includes both Group and Functional addresses.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other



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            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 2 }

ifInBroadcastPkts OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The number of packets, delivered by this sub-layer to a
            higher (sub-)layer, which were addressed to a broadcast
            address at this sub-layer.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 3 }

ifOutMulticastPkts OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The total number of packets that higher-level protocols
            requested be transmitted, and which were addressed to a
            multicast address at this sub-layer, including those that
            were discarded or not sent.  For a MAC layer protocol, this
            includes both Group and Functional addresses.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 4 }

ifOutBroadcastPkts OBJECT-TYPE
    SYNTAX      Counter32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The total number of packets that higher-level protocols
            requested be transmitted, and which were addressed to a
            broadcast address at this sub-layer, including those that
            were discarded or not sent.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other



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            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 5 }

--
-- High Capacity Counter objects.  These objects are all
-- 64 bit versions of the "basic" ifTable counters.  These
-- objects all have the same basic semantics as their 32-bit
-- counterparts, however, their syntax has been extended
-- to 64 bits.
--

ifHCInOctets OBJECT-TYPE
    SYNTAX      Counter64
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The total number of octets received on the interface,
            including framing characters.  This object is a 64-bit
            version of ifInOctets.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 6 }

ifHCInUcastPkts OBJECT-TYPE
    SYNTAX      Counter64
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The number of packets, delivered by this sub-layer to a
            higher (sub-)layer, which were not addressed to a multicast
            or broadcast address at this sub-layer.  This object is a
            64-bit version of ifInUcastPkts.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 7 }

ifHCInMulticastPkts OBJECT-TYPE
    SYNTAX      Counter64
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION



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            "The number of packets, delivered by this sub-layer to a
            higher (sub-)layer, which were addressed to a multicast
            address at this sub-layer.  For a MAC layer protocol, this
            includes both Group and Functional addresses.  This object
            is a 64-bit version of ifInMulticastPkts.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 8 }

ifHCInBroadcastPkts OBJECT-TYPE
    SYNTAX      Counter64
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The number of packets, delivered by this sub-layer to a
            higher (sub-)layer, which were addressed to a broadcast
            address at this sub-layer.  This object is a 64-bit version
            of ifInBroadcastPkts.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 9 }

ifHCOutOctets OBJECT-TYPE
    SYNTAX      Counter64
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The total number of octets transmitted out of the
            interface, including framing characters.  This object is a
            64-bit version of ifOutOctets.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 10 }

ifHCOutUcastPkts OBJECT-TYPE
    SYNTAX      Counter64
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION



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            "The total number of packets that higher-level protocols
            requested be transmitted, and which were not addressed to a
            multicast or broadcast address at this sub-layer, including
            those that were discarded or not sent.  This object is a
            64-bit version of ifOutUcastPkts.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 11 }

ifHCOutMulticastPkts OBJECT-TYPE
    SYNTAX      Counter64
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The total number of packets that higher-level protocols
            requested be transmitted, and which were addressed to a
            multicast address at this sub-layer, including those that
            were discarded or not sent.  For a MAC layer protocol, this
            includes both Group and Functional addresses.  This object
            is a 64-bit version of ifOutMulticastPkts.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 12 }

ifHCOutBroadcastPkts OBJECT-TYPE
    SYNTAX      Counter64
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The total number of packets that higher-level protocols
            requested be transmitted, and which were addressed to a
            broadcast address at this sub-layer, including those that
            were discarded or not sent.  This object is a 64-bit version
            of ifOutBroadcastPkts.

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 13 }

ifLinkUpDownTrapEnable  OBJECT-TYPE



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    SYNTAX      INTEGER { enabled(1), disabled(2) }
    MAX-ACCESS  read-write
    STATUS      current
    DESCRIPTION
            "Indicates whether linkUp/linkDown traps should be generated
            for this interface.

            By default, this object should have the value enabled(1) for
            interfaces which do not operate on 'top' of any other
            interface (as defined in the ifStackTable), and disabled(2)
            otherwise."
    ::= { ifXEntry 14 }

ifHighSpeed OBJECT-TYPE
    SYNTAX      Gauge32
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "An estimate of the interface's current bandwidth in units
            of 1,000,000 bits per second.  If this object reports a
            value of `n' then the speed of the interface is somewhere in
            the range of `n-500,000' to `n+499,999'.  For interfaces
            which do not vary in bandwidth or for those where no
            accurate estimation can be made, this object should contain
            the nominal bandwidth.  For a sub-layer which has no concept
            of bandwidth, this object should be zero."
    ::= { ifXEntry 15 }

ifPromiscuousMode  OBJECT-TYPE
    SYNTAX      TruthValue
    MAX-ACCESS  read-write
    STATUS      current
    DESCRIPTION
            "This object has a value of false(2) if this interface only
            accepts packets/frames that are addressed to this station.
            This object has a value of true(1) when the station accepts
            all packets/frames transmitted on the media.  The value
            true(1) is only legal on certain types of media.  If legal,
            setting this object to a value of true(1) may require the
            interface to be reset before becoming effective.

            The value of ifPromiscuousMode does not affect the reception
            of broadcast and multicast packets/frames by the interface."
    ::= { ifXEntry 16 }

ifConnectorPresent   OBJECT-TYPE
    SYNTAX      TruthValue
    MAX-ACCESS  read-only



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    STATUS      current
    DESCRIPTION
            "This object has the value 'true(1)' if the interface
            sublayer has a physical connector and the value 'false(2)'
            otherwise."
    ::= { ifXEntry 17 }

ifAlias   OBJECT-TYPE
    SYNTAX      DisplayString (SIZE(0..64))
    MAX-ACCESS  read-write
    STATUS      current
    DESCRIPTION
            "This object is an 'alias' name for the interface as
            specified by a network manager, and provides a non-volatile
            'handle' for the interface.

            On the first instantiation of an interface, the value of
            ifAlias associated with that interface is the zero-length
            string.  As and when a value is written into an instance of
            ifAlias through a network management set operation, then the
            agent must retain the supplied value in the ifAlias instance
            associated with the same interface for as long as that
            interface remains instantiated, including across all re-
            initializations/reboots of the network management system,
            including those which result in a change of the interface's
            ifIndex value.

            An example of the value which a network manager might store
            in this object for a WAN interface is the (Telco's) circuit
            number/identifier of the interface.

            Some agents may support write-access only for interfaces
            having particular values of ifType.  An agent which supports
            write access to this object is required to keep the value in
            non-volatile storage, but it may limit the length of new
            values depending on how much storage is already occupied by
            the current values for other interfaces."
    ::= { ifXEntry 18 }

ifCounterDiscontinuityTime OBJECT-TYPE
    SYNTAX      TimeStamp
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The value of sysUpTime on the most recent occasion at which
            any one or more of this interface's counters suffered a
            discontinuity.  The relevant counters are the specific
            instances associated with this interface of any Counter32 or



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            Counter64 object contained in the ifTable or ifXTable.  If
            no such discontinuities have occurred since the last re-
            initialization of the local management subsystem, then this
            object contains a zero value."
    ::= { ifXEntry 19 }

--           The Interface Stack Group
--
-- Implementation of this group is optional, but strongly recommended
-- for all systems
--

ifStackTable  OBJECT-TYPE
     SYNTAX        SEQUENCE OF IfStackEntry
     MAX-ACCESS    not-accessible
     STATUS        current
     DESCRIPTION
            "The table containing information on the relationships
            between the multiple sub-layers of network interfaces.  In
            particular, it contains information on which sub-layers run
            'on top of' which other sub-layers, where each sub-layer
            corresponds to a conceptual row in the ifTable.  For
            example, when the sub-layer with ifIndex value x runs over
            the sub-layer with ifIndex value y, then this table
            contains:

              ifStackStatus.x.y=active

            For each ifIndex value, I, which identifies an active
            interface, there are always at least two instantiated rows
            in this table associated with I.  For one of these rows, I
            is the value of ifStackHigherLayer; for the other, I is the
            value of ifStackLowerLayer.  (If I is not involved in
            multiplexing, then these are the only two rows associated
            with I.)

            For example, two rows exist even for an interface which has
            no others stacked on top or below it:

              ifStackStatus.0.x=active
              ifStackStatus.x.0=active "
     ::= { ifMIBObjects 2 }


ifStackEntry  OBJECT-TYPE
     SYNTAX        IfStackEntry
     MAX-ACCESS    not-accessible
     STATUS        current



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     DESCRIPTION
            "Information on a particular relationship between two sub-
            layers, specifying that one sub-layer runs on 'top' of the
            other sub-layer.  Each sub-layer corresponds to a conceptual
            row in the ifTable."
     INDEX { ifStackHigherLayer, ifStackLowerLayer }
     ::= { ifStackTable 1 }


IfStackEntry ::=
    SEQUENCE {
        ifStackHigherLayer  InterfaceIndexOrZero,
        ifStackLowerLayer   InterfaceIndexOrZero,
        ifStackStatus       RowStatus
     }


ifStackHigherLayer  OBJECT-TYPE
     SYNTAX        InterfaceIndexOrZero
     MAX-ACCESS    not-accessible
     STATUS        current
     DESCRIPTION
            "The value of ifIndex corresponding to the higher sub-layer
            of the relationship, i.e., the sub-layer which runs on 'top'
            of the sub-layer identified by the corresponding instance of
            ifStackLowerLayer.  If there is no higher sub-layer (below
            the internetwork layer), then this object has the value 0."
     ::= { ifStackEntry 1 }


ifStackLowerLayer  OBJECT-TYPE
     SYNTAX        InterfaceIndexOrZero
     MAX-ACCESS    not-accessible
     STATUS        current
     DESCRIPTION
            "The value of ifIndex corresponding to the lower sub-layer
            of the relationship, i.e., the sub-layer which runs 'below'
            the sub-layer identified by the corresponding instance of
            ifStackHigherLayer.  If there is no lower sub-layer, then
            this object has the value 0."
     ::= { ifStackEntry 2 }


ifStackStatus  OBJECT-TYPE
    SYNTAX         RowStatus
    MAX-ACCESS     read-create
    STATUS         current
    DESCRIPTION



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            "The status of the relationship between two sub-layers.

            Changing the value of this object from 'active' to
            'notInService' or 'destroy' will likely have consequences up
            and down the interface stack.  Thus, write access to this
            object is likely to be inappropriate for some types of
            interfaces, and many implementations will choose not to
            support write-access for any type of interface."
    ::= { ifStackEntry 3 }

ifStackLastChange OBJECT-TYPE
    SYNTAX         TimeTicks
    MAX-ACCESS     read-only
    STATUS         current
    DESCRIPTION
            "The value of sysUpTime at the time of the last change of
            the (whole) interface stack.  A change of the interface
            stack is defined to be any creation, deletion, or change in
            value of any instance of ifStackStatus.  If the interface
            stack has been unchanged since the last re-initialization of
            the local network management subsystem, then this object
            contains a zero value."
    ::= { ifMIBObjects 6 }


--   Generic Receive Address Table
--
-- This group of objects is mandatory for all types of
-- interfaces which can receive packets/frames addressed to
-- more than one address.
--
-- This table replaces the ifExtnsRcvAddr table.  The main
-- difference is that this table makes use of the RowStatus
-- textual convention, while ifExtnsRcvAddr did not.

ifRcvAddressTable  OBJECT-TYPE
    SYNTAX      SEQUENCE OF IfRcvAddressEntry
    MAX-ACCESS  not-accessible
    STATUS      current
    DESCRIPTION
            "This table contains an entry for each address (broadcast,
            multicast, or uni-cast) for which the system will receive
            packets/frames on a particular interface, except as follows:

            - for an interface operating in promiscuous mode, entries
            are only required for those addresses for which the system
            would receive frames were it not operating in promiscuous
            mode.



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            - for 802.5 functional addresses, only one entry is
            required, for the address which has the functional address
            bit ANDed with the bit mask of all functional addresses for
            which the interface will accept frames.

            A system is normally able to use any unicast address which
            corresponds to an entry in this table as a source address."
    ::= { ifMIBObjects 4 }

ifRcvAddressEntry  OBJECT-TYPE
    SYNTAX      IfRcvAddressEntry
    MAX-ACCESS  not-accessible
    STATUS      current
    DESCRIPTION
            "A list of objects identifying an address for which the
            system will accept packets/frames on the particular
            interface identified by the index value ifIndex."
    INDEX  { ifIndex, ifRcvAddressAddress }
    ::= { ifRcvAddressTable 1 }

IfRcvAddressEntry ::=
    SEQUENCE {
        ifRcvAddressAddress   PhysAddress,
        ifRcvAddressStatus    RowStatus,
        ifRcvAddressType      INTEGER
    }

ifRcvAddressAddress OBJECT-TYPE
    SYNTAX      PhysAddress
    MAX-ACCESS  not-accessible
    STATUS      current
    DESCRIPTION
            "An address for which the system will accept packets/frames
            on this entry's interface."
    ::= { ifRcvAddressEntry 1 }

ifRcvAddressStatus OBJECT-TYPE
    SYNTAX      RowStatus
    MAX-ACCESS  read-create
    STATUS      current
    DESCRIPTION
            "This object is used to create and delete rows in the
            ifRcvAddressTable."

    ::= { ifRcvAddressEntry 2 }

ifRcvAddressType OBJECT-TYPE
    SYNTAX      INTEGER {



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                    other(1),
                    volatile(2),
                    nonVolatile(3)
                }

    MAX-ACCESS  read-create
    STATUS      current
    DESCRIPTION
            "This object has the value nonVolatile(3) for those entries
            in the table which are valid and will not be deleted by the
            next restart of the managed system.  Entries having the
            value volatile(2) are valid and exist, but have not been
            saved, so that will not exist after the next restart of the
            managed system.  Entries having the value other(1) are valid
            and exist but are not classified as to whether they will
            continue to exist after the next restart."

    DEFVAL  { volatile }
    ::= { ifRcvAddressEntry 3 }

-- definition of interface-related traps.

linkDown NOTIFICATION-TYPE
    OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
    STATUS  current
    DESCRIPTION
            "A linkDown trap signifies that the SNMP entity, acting in
            an agent role, has detected that the ifOperStatus object for
            one of its communication links is about to enter the down
            state from some other state (but not from the notPresent
            state).  This other state is indicated by the included value
            of ifOperStatus."
    ::= { snmpTraps 3 }

linkUp NOTIFICATION-TYPE
    OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
    STATUS  current
    DESCRIPTION
            "A linkUp trap signifies that the SNMP entity, acting in an
            agent role, has detected that the ifOperStatus object for
            one of its communication links left the down state and
            transitioned into some other state (but not into the
            notPresent state).  This other state is indicated by the
            included value of ifOperStatus."
    ::= { snmpTraps 4 }

-- conformance information




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ifConformance OBJECT IDENTIFIER ::= { ifMIB 2 }

ifGroups      OBJECT IDENTIFIER ::= { ifConformance 1 }
ifCompliances OBJECT IDENTIFIER ::= { ifConformance 2 }


-- compliance statements

ifCompliance3 MODULE-COMPLIANCE
    STATUS  current
    DESCRIPTION
            "The compliance statement for SNMP entities which have
            network interfaces."

    MODULE  -- this module
        MANDATORY-GROUPS { ifGeneralInformationGroup,
                           linkUpDownNotificationsGroup }

-- The groups:
--        ifFixedLengthGroup
--        ifHCFixedLengthGroup
--        ifPacketGroup
--        ifHCPacketGroup
--        ifVHCPacketGroup
-- are mutually exclusive; at most one of these groups is implemented
-- for a particular interface.  When any of these groups is implemented
-- for a particular interface, then ifCounterDiscontinuityGroup must
-- also be implemented for that interface.


        GROUP       ifFixedLengthGroup
        DESCRIPTION
            "This group is mandatory for those network interfaces which
            are character-oriented or transmit data in fixed-length
            transmission units, and for which the value of the
            corresponding instance of ifSpeed is less than or equal to
            20,000,000 bits/second."

        GROUP       ifHCFixedLengthGroup
        DESCRIPTION
            "This group is mandatory for those network interfaces which
            are character-oriented or transmit data in fixed-length
            transmission units, and for which the value of the
            corresponding instance of ifSpeed is greater than 20,000,000
            bits/second."

        GROUP       ifPacketGroup
        DESCRIPTION



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            "This group is mandatory for those network interfaces which
            are packet-oriented, and for which the value of the
            corresponding instance of ifSpeed is less than or equal to
            20,000,000 bits/second."

        GROUP       ifHCPacketGroup
        DESCRIPTION
            "This group is mandatory only for those network interfaces
            which are packet-oriented and for which the value of the
            corresponding instance of ifSpeed is greater than 20,000,000
            bits/second but less than or equal to 650,000,000
            bits/second."

        GROUP       ifVHCPacketGroup
        DESCRIPTION
            "This group is mandatory only for those network interfaces
            which are packet-oriented and for which the value of the
            corresponding instance of ifSpeed is greater than
            650,000,000 bits/second."


        GROUP       ifCounterDiscontinuityGroup
        DESCRIPTION
            "This group is mandatory for those network interfaces that
            are required to maintain counters (i.e., those for which one
            of the ifFixedLengthGroup, ifHCFixedLengthGroup,
            ifPacketGroup, ifHCPacketGroup, or ifVHCPacketGroup is
            mandatory)."


        GROUP       ifRcvAddressGroup
        DESCRIPTION
            "The applicability of this group MUST be defined by the
            media-specific MIBs.  Media-specific MIBs must define the
            exact meaning, use, and semantics of the addresses in this
            group."

        OBJECT      ifLinkUpDownTrapEnable
        MIN-ACCESS  read-only
        DESCRIPTION
            "Write access is not required."

        OBJECT      ifPromiscuousMode
        MIN-ACCESS  read-only
        DESCRIPTION
            "Write access is not required."

        OBJECT       ifAdminStatus



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        SYNTAX       INTEGER { up(1), down(2) }
        MIN-ACCESS   read-only
        DESCRIPTION
            "Write access is not required, nor is support for the value
            testing(3)."

        OBJECT       ifAlias
        MIN-ACCESS   read-only
        DESCRIPTION
            "Write access is not required."

    ::= { ifCompliances 3 }

-- units of conformance

ifGeneralInformationGroup    OBJECT-GROUP
    OBJECTS { ifIndex, ifDescr, ifType, ifSpeed, ifPhysAddress,
              ifAdminStatus, ifOperStatus, ifLastChange,
              ifLinkUpDownTrapEnable, ifConnectorPresent,
              ifHighSpeed, ifName, ifNumber, ifAlias,
              ifTableLastChange }
    STATUS  current
    DESCRIPTION
            "A collection of objects providing information applicable to
            all network interfaces."
    ::= { ifGroups 10 }

-- the following five groups are mutually exclusive; at most
-- one of these groups is implemented for any interface

ifFixedLengthGroup    OBJECT-GROUP
    OBJECTS { ifInOctets, ifOutOctets, ifInUnknownProtos,
              ifInErrors, ifOutErrors }
    STATUS  current
    DESCRIPTION
            "A collection of objects providing information specific to
            non-high speed (non-high speed interfaces transmit and
            receive at speeds less than or equal to 20,000,000
            bits/second) character-oriented or fixed-length-transmission
            network interfaces."
    ::= { ifGroups 2 }

ifHCFixedLengthGroup    OBJECT-GROUP
    OBJECTS { ifHCInOctets, ifHCOutOctets,
              ifInOctets, ifOutOctets, ifInUnknownProtos,
              ifInErrors, ifOutErrors }
    STATUS  current
    DESCRIPTION



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            "A collection of objects providing information specific to
            high speed (greater than 20,000,000 bits/second) character-
            oriented or fixed-length-transmission network interfaces."
    ::= { ifGroups 3 }

ifPacketGroup    OBJECT-GROUP
    OBJECTS { ifInOctets, ifOutOctets, ifInUnknownProtos,
              ifInErrors, ifOutErrors,
              ifMtu, ifInUcastPkts, ifInMulticastPkts,
              ifInBroadcastPkts, ifInDiscards,
              ifOutUcastPkts, ifOutMulticastPkts,
              ifOutBroadcastPkts, ifOutDiscards,
              ifPromiscuousMode }
    STATUS  current
    DESCRIPTION
            "A collection of objects providing information specific to
            non-high speed (non-high speed interfaces transmit and
            receive at speeds less than or equal to 20,000,000
            bits/second) packet-oriented network interfaces."
    ::= { ifGroups 4 }

ifHCPacketGroup    OBJECT-GROUP
    OBJECTS { ifHCInOctets, ifHCOutOctets,
              ifInOctets, ifOutOctets, ifInUnknownProtos,
              ifInErrors, ifOutErrors,
              ifMtu, ifInUcastPkts, ifInMulticastPkts,
              ifInBroadcastPkts, ifInDiscards,
              ifOutUcastPkts, ifOutMulticastPkts,
              ifOutBroadcastPkts, ifOutDiscards,
              ifPromiscuousMode }
    STATUS  current
    DESCRIPTION
            "A collection of objects providing information specific to
            high speed (greater than 20,000,000 bits/second but less
            than or equal to 650,000,000 bits/second) packet-oriented
            network interfaces."
    ::= { ifGroups 5 }

ifVHCPacketGroup    OBJECT-GROUP
    OBJECTS { ifHCInUcastPkts, ifHCInMulticastPkts,
              ifHCInBroadcastPkts, ifHCOutUcastPkts,
              ifHCOutMulticastPkts, ifHCOutBroadcastPkts,
              ifHCInOctets, ifHCOutOctets,
              ifInOctets, ifOutOctets, ifInUnknownProtos,
              ifInErrors, ifOutErrors,
              ifMtu, ifInUcastPkts, ifInMulticastPkts,
              ifInBroadcastPkts, ifInDiscards,
              ifOutUcastPkts, ifOutMulticastPkts,



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              ifOutBroadcastPkts, ifOutDiscards,
              ifPromiscuousMode }
    STATUS  current
    DESCRIPTION
            "A collection of objects providing information specific to
            higher speed (greater than 650,000,000 bits/second) packet-
            oriented network interfaces."
    ::= { ifGroups 6 }

ifRcvAddressGroup    OBJECT-GROUP
    OBJECTS { ifRcvAddressStatus, ifRcvAddressType }
    STATUS  current
    DESCRIPTION
            "A collection of objects providing information on the
            multiple addresses which an interface receives."
    ::= { ifGroups 7 }

ifStackGroup2    OBJECT-GROUP
    OBJECTS { ifStackStatus, ifStackLastChange }
    STATUS  current
    DESCRIPTION
            "A collection of objects providing information on the
            layering of MIB-II interfaces."
    ::= { ifGroups 11 }

ifCounterDiscontinuityGroup  OBJECT-GROUP
    OBJECTS { ifCounterDiscontinuityTime }
    STATUS  current
    DESCRIPTION
            "A collection of objects providing information specific to
            interface counter discontinuities."
    ::= { ifGroups 13 }

linkUpDownNotificationsGroup  NOTIFICATION-GROUP
    NOTIFICATIONS { linkUp, linkDown }
    STATUS  current
    DESCRIPTION
            "The notifications which indicate specific changes in the
            value of ifOperStatus."
    ::= { ifGroups 14 }

-- Deprecated Definitions - Objects


--
--    The Interface Test Table
--
-- This group of objects is optional.  However, a media-specific



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-- MIB may make implementation of this group mandatory.
--
-- This table replaces the ifExtnsTestTable
--

ifTestTable   OBJECT-TYPE
    SYNTAX      SEQUENCE OF IfTestEntry
    MAX-ACCESS  not-accessible
    STATUS      deprecated
    DESCRIPTION
            "This table contains one entry per interface.  It defines
            objects which allow a network manager to instruct an agent
            to test an interface for various faults.  Tests for an
            interface are defined in the media-specific MIB for that
            interface.  After invoking a test, the object ifTestResult
            can be read to determine the outcome.  If an agent can not
            perform the test, ifTestResult is set to so indicate.  The
            object ifTestCode can be used to provide further test-
            specific or interface-specific (or even enterprise-specific)
            information concerning the outcome of the test.  Only one
            test can be in progress on each interface at any one time.
            If one test is in progress when another test is invoked, the
            second test is rejected.  Some agents may reject a test when
            a prior test is active on another interface.

            Before starting a test, a manager-station must first obtain
            'ownership' of the entry in the ifTestTable for the
            interface to be tested.  This is accomplished with the
            ifTestId and ifTestStatus objects as follows:

          try_again:
              get (ifTestId, ifTestStatus)
              while (ifTestStatus != notInUse)
                  /*
                   * Loop while a test is running or some other
                   * manager is configuring a test.
                   */
                  short delay
                  get (ifTestId, ifTestStatus)
              }

              /*
               * Is not being used right now -- let's compete
               * to see who gets it.
               */
              lock_value = ifTestId

              if ( set(ifTestId = lock_value, ifTestStatus = inUse,



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                       ifTestOwner = 'my-IP-address') == FAILURE)
                  /*
                   * Another manager got the ifTestEntry -- go
                   * try again
                   */
                  goto try_again;

              /*
               * I have the lock
               */
              set up any test parameters.

              /*
               * This starts the test
               */
              set(ifTestType = test_to_run);

              wait for test completion by polling ifTestResult

              when test completes, agent sets ifTestResult
                   agent also sets ifTestStatus = 'notInUse'

              retrieve any additional test results, and ifTestId

              if (ifTestId == lock_value+1) results are valid

            A manager station first retrieves the value of the
            appropriate ifTestId and ifTestStatus objects, periodically
            repeating the retrieval if necessary, until the value of
            ifTestStatus is 'notInUse'.  The manager station then tries
            to set the same ifTestId object to the value it just
            retrieved, the same ifTestStatus object to 'inUse', and the
            corresponding ifTestOwner object to a value indicating
            itself.  If the set operation succeeds then the manager has
            obtained ownership of the ifTestEntry, and the value of the
            ifTestId object is incremented by the agent (per the
            semantics of TestAndIncr).  Failure of the set operation
            indicates that some other manager has obtained ownership of
            the ifTestEntry.

            Once ownership is obtained, any test parameters can be
            setup, and then the test is initiated by setting ifTestType.
            On completion of the test, the agent sets ifTestStatus to
            'notInUse'.  Once this occurs, the manager can retrieve the
            results.  In the (rare) event that the invocation of tests
            by two network managers were to overlap, then there would be
            a possibility that the first test's results might be
            overwritten by the second test's results prior to the first



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            results being read.  This unlikely circumstance can be
            detected by a network manager retrieving ifTestId at the
            same time as retrieving the test results, and ensuring that
            the results are for the desired request.

            If ifTestType is not set within an abnormally long period of
            time after ownership is obtained, the agent should time-out
            the manager, and reset the value of the ifTestStatus object
            back to 'notInUse'.  It is suggested that this time-out
            period be 5 minutes.

            In general, a management station must not retransmit a
            request to invoke a test for which it does not receive a
            response; instead, it properly inspects an agent's MIB to
            determine if the invocation was successful.  Only if the
            invocation was unsuccessful, is the invocation request
            retransmitted.

            Some tests may require the interface to be taken off-line in
            order to execute them, or may even require the agent to
            reboot after completion of the test.  In these
            circumstances, communication with the management station
            invoking the test may be lost until after completion of the
            test.  An agent is not required to support such tests.
            However, if such tests are supported, then the agent should
            make every effort to transmit a response to the request
            which invoked the test prior to losing communication.  When
            the agent is restored to normal service, the results of the
            test are properly made available in the appropriate objects.
            Note that this requires that the ifIndex value assigned to
            an interface must be unchanged even if the test causes a
            reboot.  An agent must reject any test for which it cannot,
            perhaps due to resource constraints, make available at least
            the minimum amount of information after that test
            completes."
    ::= { ifMIBObjects 3 }

ifTestEntry OBJECT-TYPE
    SYNTAX       IfTestEntry
    MAX-ACCESS   not-accessible
    STATUS       deprecated
    DESCRIPTION
            "An entry containing objects for invoking tests on an
            interface."
    AUGMENTS  { ifEntry }
    ::= { ifTestTable 1 }

IfTestEntry ::=



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    SEQUENCE {
        ifTestId           TestAndIncr,
        ifTestStatus       INTEGER,
        ifTestType         AutonomousType,
        ifTestResult       INTEGER,
        ifTestCode         OBJECT IDENTIFIER,
        ifTestOwner        OwnerString
    }

ifTestId         OBJECT-TYPE
    SYNTAX       TestAndIncr
    MAX-ACCESS   read-write
    STATUS       deprecated
    DESCRIPTION
            "This object identifies the current invocation of the
            interface's test."
    ::= { ifTestEntry 1 }

ifTestStatus     OBJECT-TYPE
    SYNTAX       INTEGER { notInUse(1), inUse(2) }
    MAX-ACCESS   read-write
    STATUS       deprecated
    DESCRIPTION
            "This object indicates whether or not some manager currently
            has the necessary 'ownership' required to invoke a test on
            this interface.  A write to this object is only successful
            when it changes its value from 'notInUse(1)' to 'inUse(2)'.
            After completion of a test, the agent resets the value back
            to 'notInUse(1)'."
    ::= { ifTestEntry 2 }

ifTestType       OBJECT-TYPE
    SYNTAX       AutonomousType
    MAX-ACCESS   read-write
    STATUS       deprecated
    DESCRIPTION
            "A control variable used to start and stop operator-
            initiated interface tests.  Most OBJECT IDENTIFIER values
            assigned to tests are defined elsewhere, in association with
            specific types of interface.  However, this document assigns
            a value for a full-duplex loopback test, and defines the
            special meanings of the subject identifier:

                noTest  OBJECT IDENTIFIER ::= { 0 0 }

            When the value noTest is written to this object, no action
            is taken unless a test is in progress, in which case the
            test is aborted.  Writing any other value to this object is



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            only valid when no test is currently in progress, in which
            case the indicated test is initiated.

            When read, this object always returns the most recent value
            that ifTestType was set to.  If it has not been set since
            the last initialization of the network management subsystem
            on the agent, a value of noTest is returned."
    ::= { ifTestEntry 3 }

ifTestResult  OBJECT-TYPE
    SYNTAX       INTEGER {
                     none(1),          -- no test yet requested
                     success(2),
                     inProgress(3),
                     notSupported(4),
                     unAbleToRun(5),   -- due to state of system
                     aborted(6),
                     failed(7)
                 }
    MAX-ACCESS   read-only
    STATUS       deprecated
    DESCRIPTION
            "This object contains the result of the most recently
            requested test, or the value none(1) if no tests have been
            requested since the last reset.  Note that this facility
            provides no provision for saving the results of one test
            when starting another, as could be required if used by
            multiple managers concurrently."
    ::= { ifTestEntry 4 }

ifTestCode  OBJECT-TYPE
    SYNTAX       OBJECT IDENTIFIER
    MAX-ACCESS   read-only
    STATUS       deprecated
    DESCRIPTION
            "This object contains a code which contains more specific
            information on the test result, for example an error-code
            after a failed test.  Error codes and other values this
            object may take are specific to the type of interface and/or
            test.  The value may have the semantics of either the
            AutonomousType or InstancePointer textual conventions as
            defined in RFC 2579.  The identifier:

                testCodeUnknown  OBJECT IDENTIFIER ::= { 0 0 }

            is defined for use if no additional result code is
            available."
    ::= { ifTestEntry 5 }



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ifTestOwner      OBJECT-TYPE
    SYNTAX       OwnerString
    MAX-ACCESS   read-write
    STATUS       deprecated
    DESCRIPTION
            "The entity which currently has the 'ownership' required to
            invoke a test on this interface."
    ::= { ifTestEntry 6 }

-- Deprecated Definitions - Groups


ifGeneralGroup    OBJECT-GROUP
    OBJECTS { ifDescr, ifType, ifSpeed, ifPhysAddress,
              ifAdminStatus, ifOperStatus, ifLastChange,
              ifLinkUpDownTrapEnable, ifConnectorPresent,
              ifHighSpeed, ifName }
    STATUS  deprecated
    DESCRIPTION
            "A collection of objects deprecated in favour of
            ifGeneralInformationGroup."
    ::= { ifGroups 1 }


ifTestGroup    OBJECT-GROUP
    OBJECTS { ifTestId, ifTestStatus, ifTestType,
              ifTestResult, ifTestCode, ifTestOwner }
    STATUS  deprecated
    DESCRIPTION
            "A collection of objects providing the ability to invoke
            tests on an interface."
    ::= { ifGroups 8 }


ifStackGroup    OBJECT-GROUP
    OBJECTS { ifStackStatus }
    STATUS  deprecated
    DESCRIPTION
            "The previous collection of objects providing information on
            the layering of MIB-II interfaces."
    ::= { ifGroups 9 }


ifOldObjectsGroup    OBJECT-GROUP
    OBJECTS { ifInNUcastPkts, ifOutNUcastPkts,
              ifOutQLen, ifSpecific }
    STATUS  deprecated
    DESCRIPTION



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            "The collection of objects deprecated from the original MIB-
            II interfaces group."
    ::= { ifGroups 12 }

-- Deprecated Definitions - Compliance

ifCompliance MODULE-COMPLIANCE
    STATUS  deprecated
    DESCRIPTION
            "A compliance statement defined in a previous version of
            this MIB module, for SNMP entities which have network
            interfaces."

    MODULE  -- this module
        MANDATORY-GROUPS { ifGeneralGroup, ifStackGroup }

        GROUP       ifFixedLengthGroup
        DESCRIPTION
            "This group is mandatory for all network interfaces which
            are character-oriented or transmit data in fixed-length
            transmission units."

        GROUP       ifHCFixedLengthGroup
        DESCRIPTION
            "This group is mandatory only for those network interfaces
            which are character-oriented or transmit data in fixed-
            length transmission units, and for which the value of the
            corresponding instance of ifSpeed is greater than 20,000,000
            bits/second."

        GROUP       ifPacketGroup
        DESCRIPTION
            "This group is mandatory for all network interfaces which
            are packet-oriented."

        GROUP       ifHCPacketGroup
        DESCRIPTION
            "This group is mandatory only for those network interfaces
            which are packet-oriented and for which the value of the
            corresponding instance of ifSpeed is greater than
            650,000,000 bits/second."

        GROUP       ifTestGroup
        DESCRIPTION
            "This group is optional.  Media-specific MIBs which require
            interface tests are strongly encouraged to use this group
            for invoking tests and reporting results.  A medium specific
            MIB which has mandatory tests may make implementation of



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            this group mandatory."

        GROUP       ifRcvAddressGroup
        DESCRIPTION
            "The applicability of this group MUST be defined by the
            media-specific MIBs.  Media-specific MIBs must define the
            exact meaning, use, and semantics of the addresses in this
            group."

        OBJECT      ifLinkUpDownTrapEnable
        MIN-ACCESS  read-only
        DESCRIPTION
            "Write access is not required."

        OBJECT      ifPromiscuousMode
        MIN-ACCESS  read-only
        DESCRIPTION
            "Write access is not required."

        OBJECT      ifStackStatus
        SYNTAX      INTEGER { active(1) } -- subset of RowStatus
        MIN-ACCESS  read-only
        DESCRIPTION
            "Write access is not required, and only one of the six
            enumerated values for the RowStatus textual convention need
            be supported, specifically: active(1)."

        OBJECT       ifAdminStatus
        SYNTAX       INTEGER { up(1), down(2) }
        MIN-ACCESS   read-only
        DESCRIPTION
            "Write access is not required, nor is support for the value
            testing(3)."
    ::= { ifCompliances 1 }

ifCompliance2 MODULE-COMPLIANCE
    STATUS      deprecated
    DESCRIPTION
            "A compliance statement defined in a previous version of
            this MIB module, for SNMP entities which have network
            interfaces."

    MODULE  -- this module
        MANDATORY-GROUPS { ifGeneralInformationGroup, ifStackGroup2,
                           ifCounterDiscontinuityGroup }

        GROUP       ifFixedLengthGroup
        DESCRIPTION



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            "This group is mandatory for all network interfaces which
            are character-oriented or transmit data in fixed-length
            transmission units."

        GROUP       ifHCFixedLengthGroup
        DESCRIPTION
            "This group is mandatory only for those network interfaces
            which are character-oriented or transmit data in fixed-
            length transmission units, and for which the value of the
            corresponding instance of ifSpeed is greater than 20,000,000
            bits/second."

        GROUP       ifPacketGroup
        DESCRIPTION
            "This group is mandatory for all network interfaces which
            are packet-oriented."

        GROUP       ifHCPacketGroup
        DESCRIPTION
            "This group is mandatory only for those network interfaces
            which are packet-oriented and for which the value of the
            corresponding instance of ifSpeed is greater than
            650,000,000 bits/second."

        GROUP       ifRcvAddressGroup
        DESCRIPTION
            "The applicability of this group MUST be defined by the
            media-specific MIBs.  Media-specific MIBs must define the
            exact meaning, use, and semantics of the addresses in this
            group."

        OBJECT      ifLinkUpDownTrapEnable
        MIN-ACCESS  read-only
        DESCRIPTION
            "Write access is not required."

        OBJECT      ifPromiscuousMode
        MIN-ACCESS  read-only
        DESCRIPTION
            "Write access is not required."

        OBJECT      ifStackStatus
        SYNTAX      INTEGER { active(1) } -- subset of RowStatus
        MIN-ACCESS  read-only
        DESCRIPTION
            "Write access is not required, and only one of the six
            enumerated values for the RowStatus textual convention need
            be supported, specifically: active(1)."



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        OBJECT       ifAdminStatus
        SYNTAX       INTEGER { up(1), down(2) }
        MIN-ACCESS   read-only
        DESCRIPTION
            "Write access is not required, nor is support for the value
            testing(3)."

        OBJECT       ifAlias
        MIN-ACCESS   read-only
        DESCRIPTION
            "Write access is not required."

    ::= { ifCompliances 2 }

END

7.  Acknowledgements

   This memo has been produced by the IETF's Interfaces MIB working-
   group.

   The original proposal evolved from conversations and discussions with
   many people, including at least the following: Fred Baker, Ted
   Brunner, Chuck Davin, Jeremy Greene, Marshall Rose, Kaj Tesink, and
   Dean Throop.

8.  References

   [1]  Harrington, D., Presuhn, R. and B. Wijnen, "An Architecture for
        Describing SNMP Management Frameworks", RFC 2571, April 1999.

   [2]  Rose, M. and K. McCloghrie, "Structure and Identification of
        Management Information for TCP/IP-based Internets", STD 16, RFC
        1155, May 1990.

   [3]  Rose, M. and K. McCloghrie, "Concise MIB Definitions", STD 16,
        RFC 1212, March 1991.

   [4]  Rose, M., "A Convention for Defining Traps for use with the
        SNMP", RFC 1215, March 1991.

   [5]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
        M.  and S. Waldbusser, "Structure of Management Information
        Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.

   [6]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
        M. and S. Waldbusser, "Textual Conventions for SMIv2", STD 58,
        RFC 2579, April 1999.



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   [7]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
        M.  and S. Waldbusser, "Conformance Statements for SMIv2", STD
        58, RFC 2580, April 1999.

   [8]  Case, J., Fedor, M., Schoffstall, M. and J. Davin, "Simple
        Network Management Protocol", STD 15, RFC 1157, May 1990.

   [9]  Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
        "Introduction to Community-based SNMPv2", RFC 1901, January
        1996.

   [10] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser, "Transport
        Mappings for Version 2 of the Simple Network Management Protocol
        (SNMPv2)", RFC 1906, January 1996.

   [11] Case, J., Harrington D., Presuhn R. and B. Wijnen, "Message
        Processing and Dispatching for the Simple Network Management
        Protocol (SNMP)", RFC 2572, January 1998.

   [12] Blumenthal, U. and B. Wijnen, "User-based Security Model (USM)
        for version 3 of the Simple Network Management Protocol
        (SNMPv3)", RFC 2574, January 1998.

   [13] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser, "Protocol
        Operations for Version 2 of the Simple Network Management
        Protocol (SNMPv2)", RFC 1905, January 1996.

   [14] Levi, D., Meyer, P. and B. Stewart, "SMPv3 Applications", RFC
        2573, January 1998.

   [15] Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based Access
        Control Model (VACM) for the Simple Network Management Protocol
        (SNMP)", RFC 2575, January 1998.

   [16] Bradner, S., "Key words for use in RFCs to Indicate Requirements
        Levels", BCP 14, RFC 2119, March 1997.

   [17] McCloghrie, K. and M. Rose, "Management Information Base for
        Network Management of TCP/IP-based internets - MIB-II", STD 17.
        RFC 1213, March 1991.

   [18] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981.

   [19] McCloghrie, K., "Extensions to the Generic-Interface MIB", RFC
        1229, May 1991.






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   [20] ATM Forum Technical Committee, "LAN Emulation Client Management:
        Version 1.0 Specification", af-lane-0044.000, ATM Forum,
        September 1995.

   [21] Stewart, B., "Definitions of Managed Objects for Character
        Stream Devices using SMIv2", RFC 1658, July 1994.

   [22] Case, J., Mundy, R., Partain, D. and B. Stewart, "Introduction
        to Version 3 of the Internet-standard Network Management
        Framework", RFC 2570, April 1999.

   [23] McCloghrie, K. and F. Kastenholz, "Evolution of the Interfaces
        Group of MIB-II", RFC 1573, January 1994.

   [24] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB
        using SMIv2", RFC 2233, November 1997.

9.  Security Considerations

   There are a number of management objects defined in this MIB that
   have a MAX-ACCESS clause of read-write and/or read-create.  Such
   objects may be considered sensitive or vulnerable in some network
   environments.  The support for SET operations in a non-secure
   environment without proper protection can have a negative effect on
   network operations.

   In particular, write-able objects allow an administrator to control
   the interfaces and to perform tests on the interfaces, and
   unauthorized access to these could cause a denial of service, or in
   combination with other (e.g., physical) security breaches, could
   cause unauthorized connectivity to a device.

   SNMPv1 by itself is not a secure environment.  Even if the network
   itself is secure (for example by using IPSec), even then, there is no
   control as to who on the secure network is allowed to access and
   GET/SET (read/change/create/delete) 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 RFC 2574 [12] and the View- based
   Access Control Model RFC 2575 [15] 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 the objects only to those principals
   (users) that have legitimate rights to indeed GET or SET
   (change/create/delete) them.




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10.  Authors' Addresses

   Keith McCloghrie
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA  95134-1706

   Phone: 408-526-5260
   EMail: kzm@cisco.com"


   Frank Kastenholz
   Argon Networks
   25 Porter Rd
   Littleton Ma 01460

   Phone: (508)685-4000
   EMail: kasten@argon.com

11.  Changes from RFC 2233

   Added linkUpDownNotificationsGroup.

   Changed the status of the definition of OwnerString in this MIB to be
   deprecated, because it is only used by ifTestOwner, which is now
   deprecated, and because other MIBs should import OwnerString from RFC
   1757 or its successors.

   Added ifCompliance3 as a replacement for ifCompliance2 to omit the
   ifStackGroup2 group, and add linkUpDownNotificationsGroup.  Also,
   corrected the omission of ifVHCPacketGroup, and typos in the
   DESCRIPTIONs of ifHCPacketGroup and ifFixedLengthGroup.  Obsoleted
   ifCompliance2.

   Modified syntax of ifStackHigherLayer and ifStackLowerLayer to be
   InterfaceIndexOrZero.

   Added requirement that media-specific MIB designers specify any
   special conditions concerning the counting of framing characters in
   ifInOctets and ifOutOctets.

   Corrected a typo in the DESCRIPTION of the linkUp notification.

   Modified the introductory SNMP Network Management Framework
   boilerplate text.






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12.  Notice on Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.






























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13.  Full Copyright Statement

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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