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rfc:rfc1573

Network Working Group K. McCloghrie Request for Comments: 1573 Hughes LAN Systems Obsoletes: 1229 F. Kastenholz Category: Standards Track FTP Software

                                                          January 1994
            Evolution of the Interfaces Group of MIB-II

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.

Table of Contents

 1. Introduction .............................................    2
 2. The SNMPv2 Network Management Framework ..................    2
 2.1 Object Definitions ......................................    3
 3 Experience with the Interfaces Group ......................    3
 3.1 Areas of Clarification/Revision .........................    3
 3.1.1 Interface Numbering ...................................    4
 3.1.2 Interface Sub-Layers ..................................    4
 3.1.3 Virtual Circuits ......................................    5
 3.1.4 Bit, Character, and Fixed-Length Interfaces ...........    5
 3.1.5 Counter Size ..........................................    5
 3.1.6 Interface Speed .......................................    6
 3.1.7 Multicast/Broadcast Counters ..........................    6
 3.1.8 Addition of New ifType values .........................    6
 3.1.9 ifSpecific ............................................    6
 3.2 Clarifications/Revisions ................................    7
 3.2.1 Interface Numbering ...................................    7
 3.2.2 Interface Sub-Layers ..................................    8
 3.2.3 Guidance on Defining Sub-layers .......................   11
 3.2.4 Virtual Circuits ......................................   12
 3.2.5 Bit, Character, and Fixed-Length Interfaces ...........   12
 3.2.6 Counter Size ..........................................   14
 3.2.7 Interface Speed .......................................   16
 3.2.8 Multicast/Broadcast Counters ..........................   16
 3.2.9 Trap Enable ...........................................   17
 3.2.10 Addition of New ifType values ........................   17
 3.2.11 InterfaceIndex Textual Convention ....................   17
 3.2.12 IfAdminStatus and IfOperStatus .......................   18
 3.2.13 Traps ................................................   19
 3.2.14 ifSpecific ...........................................   20

McCloghrie & Kastenholz [Page 1] RFC 1573 Interfaces Group Evolution January 1994

 3.3 Media-Specific MIB Applicability ........................   20
 4. Overview .................................................   21
 5. IANAifType Definition ....................................   22
 6. Interfaces Group Definitions .............................   24
 7. Acknowledgements .........................................   53
 8. References ...............................................   53
 9. Security Considerations ..................................   55
 10. Authors' Addresses.......................................   55

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, 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
 proposes clarifications to, and extensions of, the architectural
 issues within the current model used for the 'interfaces' group.
 This memo also includes a MIB module.  As well as including new MIB
 definitions to support the architectural extensions, this MIB module
 also re-specifies the 'interfaces' group of MIB-II in a manner which
 is both compliant to the SNMPv2 SMI and semantically-identical to the
 existing SNMPv1-based definitions.

2. The SNMPv2 Network Management Framework

 The SNMPv2 Network Management Framework consists of four major
 components.  They are:
    o    RFC 1442 which defines the SMI, the mechanisms used for
         describing and naming objects for the purpose of management.
    o    STD 17, RFC 1213 defines MIB-II, the core set of managed
         objects for the Internet suite of protocols.
    o    RFC 1445 which defines the administrative and other
         architectural aspects of the framework.
    o    RFC 1448 which defines the protocol used for network access
         to managed objects.
 The Framework permits new objects to be defined for the purpose of
 experimentation and evaluation.

McCloghrie & Kastenholz [Page 2] RFC 1573 Interfaces Group Evolution January 1994

2.1. Object Definitions

 Managed objects are accessed via a virtual information store, termed
 the Management Information Base or MIB.  Objects in the MIB are
 defined using the subset of Abstract Syntax Notation One (ASN.1)
 defined in the SMI.  In particular, each object object type is named
 by an OBJECT IDENTIFIER, an administratively assigned name.  The
 object type together with an object instance serves to uniquely
 identify a specific instantiation of the object.  For human
 convenience, we often use a textual string, termed the descriptor, to
 refer to the object type.

3. Experience with the Interfaces Group

 One of the strengths of internetwork-layer protocols such as IP [6]
 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 have assumed an evolution or loosening of
 the model.  This memo is a proposal to document and standardize the
 evolution of the model and to fill in the gaps caused by that
 evolution.
 A previous effort to extend the interfaces group resulted in the
 publication of RFC 1229 [7].  As part of defining the evolution of
 the interfaces group, this memo applies that evolution to, and
 thereby incorporates, the RFC 1229 extensions.

3.1. Areas of Clarification/Revision

 There are several areas for which experience indicates that
 clarification, revision, or extension of the model would be helpful.
 The next sections discuss these.

McCloghrie & Kastenholz [Page 3] RFC 1573 Interfaces Group Evolution January 1994

3.1.1. 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."
 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.

3.1.2. 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, there is
 still a lack of 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

McCloghrie & Kastenholz [Page 4] RFC 1573 Interfaces Group Evolution January 1994

 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,
 all of which run over one fractional T1 channel, concurrently with
 other uses of the T1 link.  The current MIB structure does not allow
 for these sorts of relationships to be described.

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.

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.
 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).

3.1.5. Counter Size

 As the speed of network media increase, the minimum time in which a
 32 bit counter will wrap decreases.  For example, on an Ethernet, a
 stream of back-to-back, full-size packets will cause ifInOctets to
 wrap in just over 57 minutes.  For a T3 line, the minimum wrap-time

McCloghrie & Kastenholz [Page 5] RFC 1573 Interfaces Group Evolution January 1994

 is just over 12 minutes.  For FDDI, it will wrap in 5.7 minutes.  For
 a 1-gigabit medium, the counter might wrap in as little as 34
 seconds.  Requiring that interfaces be polled frequently enough not
 to miss a counter wrap will be increasingly problematic.

3.1.6. 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 2.4gbits.
 Thus, ifSpeed will be of diminishing utility over the next several
 years.

3.1.7. Multicast/Broadcast Counters

 The counters in the ifTable for packets addressed to a multicast or
 the broadcast address, are combined as counters of non-unicast
 packets.  In contrast, the ifExtensions MIB [7] defines one set of
 counters for multicast, and a separate set for broadcast packets.
 With the separate counters, the original combined counters become
 redundant.

3.1.8. Addition of New ifType values

 Over time new ifType enumerated values have been needed for new
 interface types.  With the syntax of ifType being defined in a MIB,
 this requires the new MIB to be re-issued in order to define the new
 values.  In the past, re-issuing of the MIB has occurred only after
 several years.

3.1.9. ifSpecific

 The original definition of the OBJECT IDENTIFIER value of ifSpecific
 was not sufficently clear.  As a result, different implementors have
 used it differently, and confusion has resulted.  Some
 implementations have the value of ifSpecific be the OBJECT IDENTIFIER
 that defines the media-specific MIB, i.e., the "foo" of:
        foo OBJECT IDENTIFIER ::= { transmission xxx }
 while others have it be the OBJECT IDENTIFIER of the table or entry
 in the appropriate media-specific MIB (e.g. fooTable or fooEntry),
 while still others have it be the OBJECT IDENTIFIER of the index
 object of the table's row, including instance identifier (e.g.,
 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,

McCloghrie & Kastenholz [Page 6] RFC 1573 Interfaces Group Evolution January 1994

 indexing.

3.2. Clarifications/Revisions

 The following clarifications and/or revisions are proposed.

3.2.1. Interface Numbering

 One solution to the interface numbering problem would be to redefine
 ifNumber to be the largest value of ifIndex, but the utility of such
 an object is questionable, and such a re-definition would require
 ifNumber to be deprecated.  Thus, an improvement would be to
 deprecate ifNumber and not replace it.  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 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.  It could be argued that
 this is a change in the semantics of ifIndex; however, all existing
 implementations conform to this new definition, and in the interests
 of not requiring changes in existing implementations and in the many
 existing media-specific MIBs, it is proposed that this change does
 not require ifIndex to be deprecated.
 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 SNMPv2's
 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 vital constancy requirement 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 a priori assignment of ifIndex values for all
 possible interfaces which might be added dynamically.
 The exact meaning of a "different" interface is hard to define, and
 there will be gray areas.  One important criterion is that a
 management station, not noticing that an interface has gone away and
 another come into existence, should not be confused when it
 calculates the difference between the counter values retrieved on
 successive polls for a particular ifIndex value.  However, any firm
 definition in this document would likely to turn out to be
 inadequate.  Instead, the following guidelines are offered to allow

McCloghrie & Kastenholz [Page 7] RFC 1573 Interfaces Group Evolution January 1994

 implementors to choose what "different" means in their particular
 situation.
 A previously-unused value of ifIndex should be assigned to a
 dynamically added interface if:
    (1)  the assignment of a previously-used ifIndex value to the
         interface could result in a discontinuity in the values of
         ifTable counters for that value of ifIndex; or,
    (2)  an agent has no knowledge of whether the interface is the
         "same" or "different" from a previous interface incarnation.
 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.)
 This proposed change introduces a new problem of its own.
 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 removing the previous restrictions on the
 values allowed for ifIndex, along with the interface sub-layer
 concept (see the following section), mapping from interfaces to
 physical ports becomes increasingly problematic.
 To address this issue, a new object, ifName, is added to the MIB.
 This object contains the device's name for the interface of which the
 relevant entry in the ifTable is a component.  For example, if a
 router has an interface named wan1, which is composed of PPP running
 over an RS-232 port, the ifName objects for the corresponding PPP and
 RS-232 entries in the ifTable will contain the string "wan1".

3.2.2. Interface Sub-Layers

 One possible but not recommended solution to the problem of
 representing multiple sub-layers would be to retain the concept of
 one conceptual row for all the sub-layers of an interface and have

McCloghrie & Kastenholz [Page 8] RFC 1573 Interfaces Group Evolution January 1994

 each media-specific MIB module identify its "superior" and
 "subordinate" sub-layers through OBJECT IDENTIFIER "pointers".  The
 drawbacks of this scheme are: 1) the superior/subordinate pointers
 are contained in the media-specific MIB modules, and thus, a manager
 could not learn the structure of an interface, without inspecting
 multiple pointers in different MIB modules; this is overly complex
 and only possible if the manager has knowledge of all the relevant
 media-specific MIB modules; 2) current MIB modules would all need to
 be retrofitted with these new "pointers"; 3) this scheme does not
 adequately address the problem of upward and downward multiplexing;
 and 4) enumerated values of ifType are needed for each combination of
 sub-layers.
 Another possible but not recommended scheme would be to retain the
 concept of one conceptual row for all the sub-layers of an interface
 and have a new separate MIB table to identify the "superior" and
 "subordinate" sub-layers which contain OBJECT IDENTIFIER "pointers"
 to media-specific MIB module(s) 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 does not support downward
 multiplexing, such as PPP over MLP; since MLP makes two (or more)
 serial lines appear to the layers above as a single physical
 interface, PPP over MLP should appear to the internetwork-layer as a
 single interface.  However, this scheme would result in two (or more)
 conceptual rows in the ifTable and the internetwork-layer would run
 over both of them.  This scheme also requires enumerated values of
 ifType for each combination of sub-layers.
 The solution adopted in 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 5 of this memo) 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.  It also
 allows the IANAIfType to Media-Specific MIB mapping to identify the
 media-specific MIB module for each sub- layer.  The new table
 (ifStackTable) need be referenced only to obtain information about
 layering.  Enumerated values for ifType are required for each sub-
 layer only, not for combinations of them.
 However, this solution 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
 the network layer, as at present).  It also requires that some
 objects (specifically, ifSpeed) need to have appropriate values
 identified for use when a generalized definition does not apply to a

McCloghrie & Kastenholz [Page 9] RFC 1573 Interfaces Group Evolution January 1994

 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.

McCloghrie & Kastenholz [Page 10] RFC 1573 Interfaces Group Evolution January 1994

    (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.

3.2.3. Guidance on Defining Sub-layers

 The designer of a media-specific MIB must decide whether to divide
 the interface into sub-layers, 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).
 Note that the sub-layers of an interface on one device will sometimes
 be different to the sub-layers of the interconnected interface of
 another device.  A simple example of this is a frame-relay DTE
 interface which connects to a frameRelayService interface, where the
 DTE interface has a different ifType value and media-specific MIB to
 the DCE interface.
 Also note that a media-specific MIB may mandate that a particular

McCloghrie & Kastenholz [Page 11] RFC 1573 Interfaces Group Evolution January 1994

 ifTable counter does not apply and that its value must always be 0,
 signifying that the applicable event can not and does not occur for
 that type of interface; for example, ifInMulticastPkts and
 ifOutMulticastPkts on an interface type which has no multicast
 capability.  In other circumstances, an agent must not always return
 0 for any counter just because its implementation is incapable of
 detecting occurrences of the particular event; instead, it must
 return a noSuchName/noSuchObject error/exception when queried for the
 counter, even if this prevents the implementation from complying with
 the relevant MODULE-COMPLIANCE macro.
 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 so doing, 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.

3.2.4. Virtual Circuits

 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.

3.2.5. Bit, Character, and Fixed-Length Interfaces

 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.
 One possible but not recommended solution to this problem would be to
 split the ifTable into two (or more) new MIB tables, one of which

McCloghrie & Kastenholz [Page 12] RFC 1573 Interfaces Group Evolution January 1994

 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 SNMPv2 (in contrast to SNMPv1) refer to
 object groups, where object groups are explicitly defined by listing
 the objects they contain.  Thus, in SNMPv2, 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
 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 ifGeneralGroup.  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.

McCloghrie & Kastenholz [Page 13] RFC 1573 Interfaces Group Evolution January 1994

 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.

3.2.6. Counter Size

 Two approaches to addressing the shrinking minimum counter-wrap time
 problem were evaluated.  Counters could be scaled, for example,
 ifInOctets could be changed to count received octets in, e.g., 1024
 byte blocks.  Alternatively, the size of the counter could be
 increased.
 Scaling the counters was rejected.  While it provides acceptable
 performance at high count rates, at low rates it suffers.  If there
 is little traffic on an interface, there might be a significant
 interval before enough counts occur to cause a counter to be
 incremented.  Traffic would then appear to be very bursty, leading to
 incorrect conclusions of the network's performance.
 The alternative, which this memo adopts, is to provide 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, 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 used.  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
 used and 64-bit octet counters MUST be used.  For interfaces that
 operate at 650,000,000 bits/second or faster, both 64-bit packet
 counters AND 64-bit octet counters MUST be used.
 These speed steps 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 Ethernet) should not
         require them.

McCloghrie & Kastenholz [Page 14] RFC 1573 Interfaces Group Evolution January 1994

    (2)  64-bit counters are a new feature, introduced in SNMPv2.  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):
  1. Ethernet: 57 minutes,
  1. 16 megabit Token Ring: 36 minutes,
  1. A US T3 line (45 megabits): 12 minutes,
  1. FDDI: 5.7 minutes
    (4)  The 32-bit packet counters wraps in about 57 minutes when
         64-byte packets are transmitted back-to-back on a 650,000,000
         bit/second link.
         As an aside, a 1-terabit (1,000 gigabits) 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

McCloghrie & Kastenholz [Page 15] RFC 1573 Interfaces Group Evolution January 1994

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

3.2.7. Interface Speed

 In order to deal with increasing interface speeds, we have added an
 ifHighSpeed object.
 This 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 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.
    (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.

3.2.8. Multicast/Broadcast Counters

 To avoid the redundancy of counting all non-unicast packets as well
 as having individual multicast and broadcast packet counters, we
 deprecate the use of the non-unicast counters, which can be derived

McCloghrie & Kastenholz [Page 16] RFC 1573 Interfaces Group Evolution January 1994

 from the values of the others.
 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.  To
 align the definitions better, the old counters are deprecated and
 replaced by new definitions.  Counters with 64 bits of range are also
 needed, as explained above.

3.2.9. Trap Enable

 In the multi-layer interface model, each sub-layer for which there is
 an entry in the ifTable can generate linkUp/Down 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/Down 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.
 The default setting should limit the number of traps generated to one
 per interface per linkUp/Down event.  Furthermore, it seems that the
 conditions that cause these state changes that are 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.

3.2.10. Addition of New ifType values

 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, which can be re-specified (with additional
 values) without issuing 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.  Thus, this document defines two MIB
 modules: one to define the MIB for the 'interfaces' group, and a
 second to define the first version of the IANAifType textual
 convention.  The latter will be periodically re-issued by the IANA.

3.2.11. 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

McCloghrie & Kastenholz [Page 17] RFC 1573 Interfaces Group Evolution January 1994

 of ifIndex.

3.2.12. IfAdminStatus and IfOperStatus

 A new state has been added to ifOperStatus: dormant.  This state
 indicates that the relevant interface is not actually in a condition
 to pass packets (i.e., 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).
 The down state 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, 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
 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 presumably ifOperStatus will also be down.
 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:

McCloghrie & Kastenholz [Page 18] RFC 1573 Interfaces Group Evolution January 1994

    (1)  Change to the up state if and only if the interface is able
         to send and receive packets.
    (2)  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 transition to the up state.
    (3)  Remain in the down state if an error or other fault condition
         is detected on the interface.
    (4)  Change to the unknown state if, for some reason, the state of
         the interface can not be ascertained.
    (5)  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.

3.2.13. Traps

 The exact definition of when linkUp and linkDown traps are generated,
 has been changed to reflect the changes to ifAdminStatus and
 ifOperStatus.
 LinkUp and linkDown traps are generated just after ifOperStatus
 leaves, or just before it enters, the down state, respectively.  The
 wording of the conditions under which a linkDown trap is generated
 was explicitly chosen to allow a node with only one interface to
 transmit the linkDown trap before that interface goes down.
 Operational experience seems to indicate that manager stations are
 most concerned with an interface being in the down state and the fact
 that this state may indicate a failure.  It seemed most useful to
 instrument either transitions into/out of the up state or the down
 state.
 Instrumenting transitions into or out of the up state has the
 drawback that an on-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 on-demand
 interface, then a transition to dormant will entail generation of a
 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 has the advantages:

McCloghrie & Kastenholz [Page 19] RFC 1573 Interfaces Group Evolution January 1994

    (1)  A transition into the down state will occur when an error is
         detected on an interface.  Error conditions are presumably of
         great interest to network managers.
    (2)  Departing the down 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 generarating traps on transitions
 into or out of the down state is generally consistent with current
 usage and interpretation of these traps by manager stations.
 Therefore, this memo defines that it is the transitions into/out of
 the down state which generate traps.
 Obviously, if a failure condition is present on a node with a single
 interface, the linkDown trap will probably not be succesfully
 transmitted since the interface through which it must be transmitted
 has failed.

3.2.14. ifSpecific

 The current definition of ifSpecific is not explicit enough.  The
 only definition that can both be made explicit and can cover all the
 useful situations (see section 3.1.9) is to have ifSpecific be the
 most general value for the media-specific MIB module (the first
 example given section in 3.1.9).  This effectively makes it redundant
 because it contains no more information than is provided by ifType.
 For this reason, ifSpecific has been deprecated.

3.3. 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 preserve 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.
 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.

McCloghrie & Kastenholz [Page 20] RFC 1573 Interfaces Group Evolution January 1994

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

4. Overview

 This MIB consists of 5 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 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.
 ifTestTable
      This table contains objects that are used to perform tests on
      interfaces.  This table is a generic table.  The designers of
      media-specific MIBs must define exactly how this table
      applies to their specific MIB.

McCloghrie & Kastenholz [Page 21] RFC 1573 Interfaces Group Evolution January 1994

      This table replaces the interface test table defined in
      RFC1229 [7].  The significant change is the replacement of
      the ifExtnsTestCommunity (and ifExtnsTestContext which would
      also have been required for SNMPv2) and ifExtnsTestRequestId
      objects, by the new ifTestId, ifTestStatus, and ifTestOwner
      objects.
 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.

5. IANAifType Definition

 IANAifType-MIB DEFINITIONS ::= BEGIN
 IMPORTS
     MODULE-IDENTITY, OBJECT-TYPE        FROM SNMPv2-SMI
     TEXTUAL-CONVENTION                  FROM SNMPv2-TC;
 ianaifType MODULE-IDENTITY
     LAST-UPDATED "9311082155Z"
     ORGANIZATION "IANA"
     CONTACT-INFO
                "        Internet Assigned Numbers Authority
                 Postal: USC/Information Sciences Institute
                         4676 Admiralty Way, Marina del Rey, CA 90292
                 Tel:    +1  310 822 1511
                 E-Mail: iana@isi.edu"
     DESCRIPTION
             "The MIB module which defines the IANAifType textual
             convention, and thus the enumerated values of the
             ifType object defined in MIB-II's ifTable."
     ::= { mib-2 30 }
 IANAifType ::= TEXTUAL-CONVENTION
     STATUS       current
     DESCRIPTION
             "This data type is used as the syntax of the ifType
             object in the (updated) definition of MIB-II's
             ifTable.

McCloghrie & Kastenholz [Page 22] RFC 1573 Interfaces Group Evolution January 1994

             The definition of this textual convention with the
             addition of newly assigned values is published
             periodically by the IANA, in either the Assigned
             Numbers RFC, or some derivative of it specific to
             Internet Network Management number assignments.  (The
             latest arrangements can be obtained by contacting the
             IANA.)
             Requests for new values should be made to IANA via
             email (iana@isi.edu).
             The relationship between the assignment of ifType
             values and of OIDs to particular media-specific MIBs
             is solely the purview of IANA and is subject to change
             without notice.  Quite often, a media-specific MIB's
             OID-subtree assignment within MIB-II's 'transmission'
             subtree will be the same as its ifType value.
             However, in some circumstances this will not be the
             case, and implementors must not pre-assume any
             specific relationship between ifType values and
             transmission subtree OIDs."
     SYNTAX  INTEGER {
                 other(1),          -- none of the following
                 regular1822(2),
                 hdh1822(3),
                 ddnX25(4),
                 rfc877x25(5),
                 ethernetCsmacd(6),
                 iso88023Csmacd(7),
                 iso88024TokenBus(8),
                 iso88025TokenRing(9),
                 iso88026Man(10),
                 starLan(11),
                 proteon10Mbit(12),
                 proteon80Mbit(13),
                 hyperchannel(14),
                 fddi(15),
                 lapb(16),
                 sdlc(17),
                 ds1(18),           -- DS1/E1 (RFC 1406)
                 e1(19),            -- obsolete
                 basicISDN(20),
                 primaryISDN(21),
                 propPointToPointSerial(22), -- proprietary serial
                 ppp(23),
                 softwareLoopback(24),
                 eon(25),            -- CLNP over IP (RFC 1070)
                 ethernet3Mbit(26),

McCloghrie & Kastenholz [Page 23] RFC 1573 Interfaces Group Evolution January 1994

                 nsip(27),           -- XNS over IP
                 slip(28),           -- generic SLIP
                 ultra(29),          -- ULTRA technologies
                 ds3(30),            -- T-3
                 sip(31),            -- SMDS
                 frameRelay(32),    -- DTE only
                 rs232(33),
                 para(34),           -- parallel-port
                 arcnet(35),         -- arcnet
                 arcnetPlus(36),     -- arcnet plus
                 atm(37),            -- ATM cells
                 miox25(38),
                 sonet(39),          -- SONET or SDH
                 x25ple(40),
                 iso88022llc(41),
                 localTalk(42),
                 smdsDxi(43),
                 frameRelayService(44),  -- Frame relay DCE
                 v35(45),
                 hssi(46),
                 hippi(47),
                 modem(48),          -- Generic modem
                 aal5(49),           -- AAL5 over ATM
                 sonetPath(50),
                 sonetVT(51),
                 smdsIcip(52),       -- SMDS InterCarrier Interface
                 propVirtual(53),    -- proprietary virtual/internal
                 propMultiplexor(54) -- proprietary multiplexing
             }
 END

6. Interfaces Group Definitions

 IF-MIB DEFINITIONS ::= BEGIN
 IMPORTS
     MODULE-IDENTITY, OBJECT-TYPE, Counter32, Gauge32,
     Integer32, TimeTicks,
     NOTIFICATION-TYPE                        FROM SNMPv2-SMI
     TEXTUAL-CONVENTION, DisplayString,
     PhysAddress, TruthValue, RowStatus,
     AutonomousType, TestAndIncr              FROM SNMPv2-TC
     MODULE-COMPLIANCE, OBJECT-GROUP          FROM SNMPv2-CONF
     IANAifType                               FROM IANAifType-MIB
     interfaces                               FROM RFC-1213;

McCloghrie & Kastenholz [Page 24] RFC 1573 Interfaces Group Evolution January 1994

 ifMIB MODULE-IDENTITY
     LAST-UPDATED "9311082155Z"
     ORGANIZATION "IETF Interfaces MIB Working Group"
     CONTACT-INFO
                "        Keith McCloghrie
                 Postal: Hughes LAN Systems
                         1225 Charleston Road, Mountain View, CA 94043
                 Tel:    +1 415 966 7934
                 E-Mail: kzm@hls.com
                         Frank Kastenholz
                 Postal: FTP Software
                         2 High Street, North Andover, MA 01845
                 Tel:    +1 508 685 4000
                 E-Mail: kasten@ftp.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."
     ::= { mib-2 31 }
 ifMIBObjects OBJECT IDENTIFIER ::= { ifMIB 1 }
  1. - OwnerString has the same semantics as used in RFC 1271
 OwnerString ::= TEXTUAL-CONVENTION
     DISPLAY-HINT "255a"
     STATUS       current
     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))

McCloghrie & Kastenholz [Page 25] RFC 1573 Interfaces Group Evolution January 1994

  1. - InterfaceIndex contains the semantics of ifIndex and
  2. - should be used for any objects defined on other mib
  3. - modules that need these semantics.
 InterfaceIndex ::= TEXTUAL-CONVENTION
     DISPLAY-HINT "d"
     STATUS       current
     DESCRIPTION
             "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
 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 }
  1. - the Interfaces table
  1. - The Interfaces table contains information on the entity's
  2. - interfaces. Each sub-layer below the internetwork-layer
  3. - 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

McCloghrie & Kastenholz [Page 26] RFC 1573 Interfaces Group Evolution January 1994

             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
     }
 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

McCloghrie & Kastenholz [Page 27] RFC 1573 Interfaces Group Evolution January 1994

     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
     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 }

McCloghrie & Kastenholz [Page 28] RFC 1573 Interfaces Group Evolution January 1994

 ifPhysAddress OBJECT-TYPE
     SYNTAX      PhysAddress
     MAX-ACCESS  read-only
     STATUS      current
     DESCRIPTION
             "The interface's address at its protocol sub-layer.
             The interface's media-specific MIB must define the bit
             and byte ordering and format of the value contained by
             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 }
 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)
             }
     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

McCloghrie & Kastenholz [Page 29] RFC 1573 Interfaces Group Evolution January 1994

             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
             incomming connection); it should remain in the down(2)
             state if and only if there is a fault that prevents if
             from going to the up(1) state."
     ::= { 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,
             including framing characters."
     ::= { 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."
     ::= { ifEntry 11 }
 ifInNUcastPkts OBJECT-TYPE
     SYNTAX  Counter32
     MAX-ACCESS  read-only
     STATUS      deprecated
     DESCRIPTION
             "The number of packets, delivered by this sub-layer to

McCloghrie & Kastenholz [Page 30] RFC 1573 Interfaces Group Evolution January 1994

             a higher (sub-)layer, which were addressed to a
             multicast or broadcast address at this sub-layer.
             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 their being deliverable to a higher-layer
             protocol.  One possible reason for discarding such a
             packet could be to free up buffer space."
     ::= { 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."
     ::= { 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 which
             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 which does not support
             protocol multiplexing, this counter will always be 0."
     ::= { ifEntry 15 }

McCloghrie & Kastenholz [Page 31] RFC 1573 Interfaces Group Evolution January 1994

 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."
     ::= { 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."
     ::= { 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.
             This object is deprecated in favour of
             ifOutMulticastPkts and ifOutBroadcastPkts."
     ::= { ifEntry 18 }
 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."
     ::= { ifEntry 19 }

McCloghrie & Kastenholz [Page 32] RFC 1573 Interfaces Group Evolution January 1994

 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."
     ::= { 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 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
             1443.  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 }
  1. -
  2. - Extension to the interface table
  3. -
  4. - This table replaces the ifExtnsTable table.
  5. -
 ifXTable        OBJECT-TYPE
     SYNTAX      SEQUENCE OF IfXEntry
     MAX-ACCESS  not-accessible

McCloghrie & Kastenholz [Page 33] RFC 1573 Interfaces Group Evolution January 1994

     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,
         ifHCInBroadcastPkts     Counter64,
         ifHCOutOctets           Counter64,
         ifHCOutUcastPkts        Counter64,
         ifHCOutMulticastPkts    Counter64,
         ifHCOutBroadcastPkts    Counter64,
         ifLinkUpDownTrapEnable  INTEGER,
         ifHighSpeed             Gauge32,
         ifPromiscuousMode       TruthValue,
         ifConnectorPresent      TruthValue
     }
 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

McCloghrie & Kastenholz [Page 34] RFC 1573 Interfaces Group Evolution January 1994

             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.  If there is no local name, or this object is
             otherwise not applicable, then this object contains a
             0-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."
     ::= { 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."
     ::= { 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."
     ::= { ifXEntry 4 }
 ifOutBroadcastPkts OBJECT-TYPE
     SYNTAX      Counter32
     MAX-ACCESS  read-only

McCloghrie & Kastenholz [Page 35] RFC 1573 Interfaces Group Evolution January 1994

     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."
     ::= { ifXEntry 5 }
  1. -
  2. - High Capacity Counter objects. These objects are all
  1. - 64 bit versions of the "basic" ifTable counters. These
  2. - objects all have the same basic semantics as their 32-bit
  3. - counterparts, however, their syntax has been extended
  4. - to 64 bits.
  5. -
 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."
     ::= { 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."
     ::= { ifXEntry 7 }
 ifHCInMulticastPkts 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
             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

McCloghrie & Kastenholz [Page 36] RFC 1573 Interfaces Group Evolution January 1994

             ifInMulticastPkts."
     ::= { 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."
     ::= { 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."
     ::= { ifXEntry 10 }
 ifHCOutUcastPkts 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 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."
     ::= { 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

McCloghrie & Kastenholz [Page 37] RFC 1573 Interfaces Group Evolution January 1994

             of ifOutMulticastPkts."
     ::= { 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."
     ::= { ifXEntry 13 }
 ifLinkUpDownTrapEnable  OBJECT-TYPE
     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

McCloghrie & Kastenholz [Page 38] RFC 1573 Interfaces Group Evolution January 1994

     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
     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 }
  1. - The Interface Stack Group
  2. -
  3. - Implementation of this group is mandatory for all systems
  4. -
 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.  Each
             sub-layer corresponds to a conceptual row in the
             ifTable."
      ::= { ifMIBObjects 2 }
 ifStackEntry  OBJECT-TYPE
      SYNTAX        IfStackEntry

McCloghrie & Kastenholz [Page 39] RFC 1573 Interfaces Group Evolution January 1994

      MAX-ACCESS    not-accessible
      STATUS        current
      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  Integer32,
         ifStackLowerLayer   Integer32,
         ifStackStatus       RowStatus
      }
 ifStackHigherLayer  OBJECT-TYPE
      SYNTAX        Integer32
      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        Integer32
      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

McCloghrie & Kastenholz [Page 40] RFC 1573 Interfaces Group Evolution January 1994

     SYNTAX         RowStatus
     MAX-ACCESS     read-write
     STATUS         current
     DESCRIPTION
             "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 }
  1. -
  2. - The Interface Test Table
  3. -
  4. - This group of objects is optional. However, a media-specific
  5. - MIB may make implementation of this group mandatory.
  6. -
  7. - This table replaces the ifExtnsTestTable
  8. -
 ifTestTable   OBJECT-TYPE
     SYNTAX      SEQUENCE OF IfTestEntry
     MAX-ACCESS  not-accessible
     STATUS      current
     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.

McCloghrie & Kastenholz [Page 41] RFC 1573 Interfaces Group Evolution January 1994

             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,
                       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

McCloghrie & Kastenholz [Page 42] RFC 1573 Interfaces Group Evolution January 1994

            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 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

McCloghrie & Kastenholz [Page 43] RFC 1573 Interfaces Group Evolution January 1994

            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       current
     DESCRIPTION
             "An entry containing objects for invoking tests on an
             interface."
     AUGMENTS  { ifEntry }
     ::= { ifTestTable 1 }
 IfTestEntry ::=
     SEQUENCE {
         ifTestId           TestAndIncr,
         ifTestStatus       INTEGER,
         ifTestType         AutonomousType,
         ifTestResult       INTEGER,
         ifTestCode         OBJECT IDENTIFIER,
         ifTestOwner        OwnerString
     }
 ifTestId         OBJECT-TYPE
     SYNTAX       TestAndIncr
     MAX-ACCESS   read-write
     STATUS       current
     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       current
     DESCRIPTION

McCloghrie & Kastenholz [Page 44] RFC 1573 Interfaces Group Evolution January 1994

             "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       current
     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 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)
                  }

McCloghrie & Kastenholz [Page 45] RFC 1573 Interfaces Group Evolution January 1994

     MAX-ACCESS   read-only
     STATUS       current
     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       current
     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
             1443.  The identifier:
                 testCodeUnknown  OBJECT IDENTIFIER ::= { 0 0 }
             is defined for use if no additional result code is
             available."
     ::= { ifTestEntry 5 }
 ifTestOwner      OBJECT-TYPE
     SYNTAX       OwnerString
     MAX-ACCESS   read-write
     STATUS       current
     DESCRIPTION
             "The entity which currently has the 'ownership'
             required to invoke a test on this interface."
     ::= { ifTestEntry 6 }
  1. - Generic Receive Address Table
  2. -
  3. - This group of objects is mandatory for all types of
  4. - interfaces which can receive packets/frames addressed to
  5. - more than one address.
  6. -
  7. - This table replaces the ifExtnsRcvAddr table. The main

McCloghrie & Kastenholz [Page 46] RFC 1573 Interfaces Group Evolution January 1994

  1. - difference is that this table makes use of the RowStatus
  2. - 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:
  1. 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.
  1. 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."
     ::= { 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  read-create
     STATUS      current
     DESCRIPTION

McCloghrie & Kastenholz [Page 47] RFC 1573 Interfaces Group Evolution January 1994

             "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-write
     STATUS      current
     DESCRIPTION
             "This object is used to create and delete rows in the
             ifRcvAddressTable."
     ::= { ifRcvAddressEntry 2 }
 ifRcvAddressType OBJECT-TYPE
     SYNTAX      INTEGER {
                     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 }
  1. - definition of interface-related traps.
 linkDown NOTIFICATION-TYPE
     OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
     STATUS  current
     DESCRIPTION
             "A linkDown trap signifies that the SNMPv2 entity,
             acting in an agent role, has detected that the
             ifOperStatus object for one of its communication links

McCloghrie & Kastenholz [Page 48] RFC 1573 Interfaces Group Evolution January 1994

             is about to transition into the down state."
     ::= { snmpTraps 3 }
 linkUp NOTIFICATION-TYPE
     OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
     STATUS  current
     DESCRIPTION
             "A linkUp trap signifies that the SNMPv2 entity,
             acting in an agent role, has detected that the
             ifOperStatus object for one of its communication links
             has transitioned out of the down state."
     ::= { snmpTraps 4 }
  1. - conformance information
 ifConformance OBJECT IDENTIFIER ::= { ifMIB 2 }
 ifGroups      OBJECT IDENTIFIER ::= { ifConformance 1 }
 ifCompliances OBJECT IDENTIFIER ::= { ifConformance 2 }
  1. - compliance statements
 ifCompliance MODULE-COMPLIANCE
     STATUS  current
     DESCRIPTION
             "The compliance statement for SNMPv2 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

McCloghrie & Kastenholz [Page 49] RFC 1573 Interfaces Group Evolution January 1994

         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 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

McCloghrie & Kastenholz [Page 50] RFC 1573 Interfaces Group Evolution January 1994

             value testing(3)."
     ::= { ifCompliances 1 }
  1. - units of conformance
 ifGeneralGroup    OBJECT-GROUP
     OBJECTS { ifDescr, ifType, ifSpeed, ifPhysAddress,
               ifAdminStatus, ifOperStatus, ifLastChange,
               ifLinkUpDownTrapEnable, ifConnectorPresent,
               ifHighSpeed, ifName }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information
             applicable to all network interfaces."
     ::= { ifGroups 1 }
  1. - the following five groups are mutually exclusive; at most
  2. - 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, character-oriented or
             fixed-length-transmission network interfaces.  (Non-
             high speed interfaces transmit and receive at speeds
             less than or equal to 20,000,000 bits/second.)"
     ::= { ifGroups 2 }
 ifHCFixedLengthGroup    OBJECT-GROUP
     OBJECTS { ifHCInOctets, ifHCOutOctets,
               ifInOctets, ifOutOctets, ifInUnknownProtos,
               ifInErrors, ifOutErrors }
     STATUS  current
     DESCRIPTION
             "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,

McCloghrie & Kastenholz [Page 51] RFC 1573 Interfaces Group Evolution January 1994

               ifInBroadcastPkts, ifInDiscards,
               ifOutUcastPkts, ifOutMulticastPkts,
               ifOutBroadcastPkts, ifOutDiscards,
               ifPromiscuousMode }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information
             specific to non-high speed, packet-oriented network
             interfaces.  (Non-high speed interfaces transmit and
             receive at speeds less than or equal to 20,000,000
             bits/second.)"
     ::= { 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,
               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 }

McCloghrie & Kastenholz [Page 52] RFC 1573 Interfaces Group Evolution January 1994

 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 }
 ifTestGroup    OBJECT-GROUP
     OBJECTS { ifTestId, ifTestStatus, ifTestType,
               ifTestResult, ifTestCode, ifTestOwner }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing the ability to
             invoke tests on an interface."
     ::= { ifGroups 8 }
 ifStackGroup    OBJECT-GROUP
     OBJECTS { ifStackStatus }
     STATUS  current
     DESCRIPTION
             "A collection of objects providing information on the
             layering of MIB-II interfaces."
     ::= { ifGroups 9 }
 END

7. Acknowledgements

 This memo has been produced by the IETF's Interfaces MIB Working
 Group.
 The initial proposal to the working group was the result of
 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] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Structure
     of Management Information for version 2 of the Simple Network
     Management Protocol (SNMPv2)", RFC 1442, SNMP Research, Inc.,
     Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon
     University, April 1993.
 [2] Galvin, J., and K. McCloghrie, "Administrative Model for version
     2 of the Simple Network Management Protocol (SNMPv2)", RFC 1445,
     Trusted Information Systems, Hughes LAN Systems, April 1993.

McCloghrie & Kastenholz [Page 53] RFC 1573 Interfaces Group Evolution January 1994

 [3] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Protocol
     Operations for version 2 of the Simple Network Management
     Protocol (SNMPv2)", RFC 1448, SNMP Research, Inc., Hughes LAN
     Systems, Dover Beach Consulting, Inc., Carnegie Mellon
     University, April 1993.
 [4] McCloghrie, K., and M. Rose, "Management Information Base for
     Network Management of TCP/IP-based internets - MIB-II", STD 17,
     RFC 1213, Hughes LAN Systems, Performance Systems International,
     March 1991.
 [5] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple
     Network Management Protocol", RFC 1157, SNMP Research,
     Performance Systems International, Performance Systems
     International, MIT Laboratory for Computer Science, May 1990.
 [6] Postel, J., "Internet Protocol", STD 5, RFC 791, USC/Information
     Sciences Institute, September 1981.
 [7] McCloghrie, K., "Extensions to the Generic-Interface MIB", RFC
     1229, Hughes LAN Systems, May 1991.
 [8] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Textual
     Conventions for version 2 of the Simple Network Management
     Protocol (SNMPv2)", RFC 1443, SNMP Research, Inc., Hughes LAN
     Systems, Dover Beach Consulting, Inc., Carnegie Mellon
     University, April 1993.

McCloghrie & Kastenholz [Page 54] RFC 1573 Interfaces Group Evolution January 1994

9. Security Considerations

 Security issues are not discussed in this memo.

10. Authors' Addresses

 Keith McCloghrie
 Hughes LAN Systems
 1225 Charleston Rd,
 Mountain View, Ca 94043
 Phone: 415-966-7934
 EMail: kzm@hls.com
 Frank Kastenholz
 FTP Software
 2 High Street
 North Andover, Mass. USA 01845
 Phone: (508)685-4000
 EMail: kasten@ftp.com

McCloghrie & Kastenholz [Page 55]

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