Subject: New version of Interfaces MIB

From: Keith McCloghrie <[email-masked]>
Date: Fri, 17 Jul 1998 12:41:46 -0700 (PDT)

I have submitted the updated version of RFC 2233 as an Internet Draft.
My thanks to Gary Hanson for reviewing the edits, at which time he
suggested that a version with change-bars is the easiest way to review
the changes.  So, whereas the new Internet Draft does not have
change-bars, I'm including below a version with change-bars to show
the differences from (my source to) RFC 2233.  Note that the reduced
line-length near the change-bars is an artifact of the program which
produces them.

Keith.
--------------

Network Working Group                                   Keith McCloghrie|
Internet Draft                                             Cisco Systems|
Obsoletes: 1573, 2233                                   Frank Kastenholz|
                                                          Argon Networks|
                                                            16 July 1998|

                    The Interfaces Group MIB                        |

                   draft-ietf-ifmib-mib-07.txt                      |

Status of this Memo

This document is an Internet-Draft.  Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its
areas, and its working groups.  Note that other groups may also
distribute working documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
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To learn the current status of any Internet-Draft, please check
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Copyright Notice                                                    +

Copyright (C) The Internet Society (1998).  All Rights Reserved.    +



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1.  Introduction

This memo defines a portion of the Management Information Base
(MIB) for use with network management protocols in the Internet
community.  In particular, it describes managed objects used for
managing Network Interfaces.

This memo discusses the 'interfaces' group of MIB-II [17],          |
especially the experience gained from the definition of numerous
media-specific MIB modules for use in conjunction with the
'interfaces' group for managing various sub-layers beneath the
internetwork-layer.  It specifies clarifications to, and
extensions of, the architectural issues within the MIB-II model of  |
the 'interfaces' group.  This memo obsoletes RFC 2233, the          |
previous version of the Interfaces Group MIB.                       |

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

2.  The SNMP Network Management Framework

The SNMP Management Framework presently consists of five major      |
components:                                                         |

o    An overall architecture, described in RFC 2271 [1].            |

o    Mechanisms for describing and naming objects and events for    |
     the purpose of management.  The first version of this          |
     Structure of Management Information (SMI) is called SMIv1 and  |
     described in RFC 1155 [2], RFC 1212 [3] and RFC 1215 [4].      |
     The second version, called SMIv2, is described in RFC 1902     |
     [5], RFC 1903 [6] and RFC 1904 [7].                            |

o    Message protocols for transferring management information.     |
     The first version of the SNMP message protocol is called       |
     SNMPv1 and described in RFC 1157 [8].  A second version of     |
     the SNMP message protocol, which is not an Internet standards  |
     track protocol, is called SNMPv2c and described in RFC 1901    |
     [9] and RFC 1906 [10].  The third version of the message       |
     protocol is called SNMPv3 and described in RFC 1906 [10], RFC  |
     2272 [11] and RFC 2274 [12].                                   |

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

o    A set of fundamental applications described in RFC 2273 [14]   |
     and the view-based access control mechanism described in RFC   |
     2275 [15].                                                     |

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

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

3.  Experience with the Interfaces Group

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

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Experience in defining these media-specific MIB modules has shown
that the model defined by MIB-II is too simplistic and/or static
for some types of media-specific management.  As a result, some of
these media-specific MIB modules assume an evolution or loosening
of the model.  This memo documents and standardizes that evolution
of the model and fills in the gaps caused by that evolution.  This
memo also incorporates the interfaces group extensions documented
in RFC 1229 [19].                                                   |

3.1.  Clarifications/Revisions

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

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

3.1.1.  Interface Sub-Layers

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

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

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An associated problem is that of upward and downward multiplexing
of the sub-layers.  An example of upward multiplexing is MLP
(Multi-Link-Procedure) which provides load-sharing over several
serial lines by appearing as a single point-to-point link to the
sub-layer(s) above.  An example of downward multiplexing would be
several instances of PPP, each framed within a separate X.25
virtual circuit, all of which run over one fractional T1 channel,
concurrently with other uses of the T1 link.  The MIB structure
must allow these sorts of relationships to be described.

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

The solution adopted by this memo is to have an individual
conceptual row in the ifTable to represent each sub-layer, and
have a new separate MIB table (the ifStackTable, see section 6
below) to identify the "superior" and "subordinate" sub-layers

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through INTEGER "pointers" to the appropriate conceptual rows in
the ifTable.  This solution supports both upward and downward
multiplexing, allows the IANAifType to Media-Specific MIB mapping
to identify the media-specific MIB module for that sub-layer, such
that the new table need only be referenced to obtain information
about layering, and it only requires enumerated values of ifType
for each sub-layer, not for combinations of them.  However, it
does require that the descriptions of some objects in the ifTable
(specifically, ifType, ifPhysAddress, ifInUcastPkts, and
ifOutUcastPkts) be generalized so as to apply to any sub-layer
(rather than only to a sub-layer immediately beneath the network
layer as previously), plus some (specifically, ifSpeed) which need
to have appropriate values identified for use when a generalized
definition does not apply to a particular sub-layer.

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

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

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

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

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

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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.

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

3.1.2.  Guidance on Defining Sub-layers

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

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

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

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

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

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interface.

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

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

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

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

3.1.3.  Virtual Circuits

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

This memo strongly recommends that connection-oriented sub-layers
do not have a conceptual row in the ifTable for each virtual
circuit.  This avoids the proliferation of conceptual rows,

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

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

3.1.4.  Bit, Character, and Fixed-Length Interfaces

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

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

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

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

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full ifTable for bit- and character-oriented sub-layers.

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

The solution adopted in this memo builds upon the fact that
compliance statements in 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 ifGeneralInformationGroup.  This group contains those
     objects applicable to all types of network interfaces,
     including bit-oriented interfaces.

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

(3)  the ifFixedLengthGroup.  This group contains the objects
     applicable not only to character-oriented interfaces, such as
     RS-232, but also to those subnetwork technologies, such as

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     cell-relay/ATM, which transmit data in fixed length
     transmission units.  As well as the octet counters, there are
     also a few other counters (e.g., the error counters) which
     are useful for this type of interface, but are currently
     defined as being packet-oriented.  To accommodate this, the
     definitions of these counters are generalized to apply to
     character-oriented interfaces and fixed-length-transmission
     interfaces.

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

3.1.5.  Interface Numbering

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

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

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

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

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

Redefining ifNumber to be the largest value of ifIndex was
rejected since it would not help.  Such a re-definition would
require ifNumber to be deprecated and the utility of the redefined

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object would be questionable.  Alternatively, ifNumber could be
deprecated and not replaced.  However, the deprecation of ifNumber
would require a change to that portion of ifIndex's definition
which refers to ifNumber.  So, since the definition of ifIndex
must be changed anyway in order to solve the problem, changes to
ifNumber do not benefit the solution.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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becomes increasingly problematic.

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

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

3.1.6.  Counter Size

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

A rejected solution to this problem was to scale the counters; for
example, ifInOctets could be changed to count received octets in, say,
1024 byte blocks.  While it would provide acceptable functionality at
high rates of the counted-events, at low rates it suffers.  If there is
little traffic on an interface, there might be a significant interval

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before enough of the counted-events occur to cause the scaled counter to
be incremented.  Traffic would then appear to be very bursty, leading to
incorrect conclusions of the network's performance.

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

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

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

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

(2)  64-bit counters are a new feature, introduced in 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):

     -   10Mbs Ethernet: 57 minutes,

     -   16Mbs Token Ring: 36 minutes,

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

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     -   FDDI: 5.7 minutes

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

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

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

The new "high capacity" groups are:

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

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

3.1.7.  Interface Speed

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

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

Other alternatives considered (but rejected) were:

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(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.

3.1.8.  Multicast/Broadcast Counters

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

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

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3.1.9.  Trap Enable

In the multi-layer interface model, each sub-layer for which there is an
entry in the ifTable can generate linkUp/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
state changes of most interest to network managers occur at the lowest
level of an interface stack.  Therefore we specify that by default, only
the lowest sub-layer of the interface generate traps.

3.1.10.  Addition of New ifType values

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

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

3.1.11.  InterfaceIndex Textual Convention

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

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3.1.12.  New states for IfOperStatus

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

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

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

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

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

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

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

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

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

3.1.13.  IfAdminStatus and IfOperStatus

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

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

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

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

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

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

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

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

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

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

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

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

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

3.1.14.  IfOperStatus in an Interface Stack

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

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

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

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

3.1.15.  Traps

The exact definition of when linkUp and linkDown traps are generated has
been changed to reflect the changes to ifAdminStatus and ifOperStatus.

Operational experience indicates that management stations are most
concerned with an interface being in the down state and the fact that

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this state may indicate a failure.  Thus, it is most useful to
instrument transitions into/out of either the up state or the down
state.

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

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

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

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

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

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

Therefore, this memo defines that LinkUp and linkDown traps are
generated on just after ifOperStatus leaves, or just before it enters,
the down state, respectively; except that LinkUp and linkDown traps
never generated on transitions to/from the notPresent state.

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

Some interfaces perform a link "training" function when trying to bring
the interface up.  In the event that such an interface were defective,

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then the training function would fail and the interface would remain
down, and the training function might be repeated at appropriate
intervals.  If the interface, while performing this training function,
were considered to the in the testing state, then linkUp and linkDown
traps would be generated for each start and end of the training
function.  This is not the intent of the linkUp and linkDown traps, and
therefore, while performing such a training function, the interface's
state should be represented as down.

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

3.1.16.  ifSpecific

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

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

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

3.1.17.  Creation/Deletion of Interfaces

While some interfaces, for example, most physical interfaces, cannot be
created via network management, other interfaces such as logical
interfaces sometimes can be.  The ifTable contains only generic
information about an interface.  Almost all 'create-able' interfaces

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have other, media-specific, information through which configuration
parameters may be supplied prior to creating such an interface.  Thus,
the ifTable does not itself support the creation or deletion of an        |
interface (specifically, it has no RowStatus [6] column).                 |
Rather, if a particular interface type supports the dynamic creation
and/or deletion of an interface of that type, then that media-specific
MIB should include an appropriate RowStatus object (see the ATM LAN-      |
Emulation Client MIB [20] for an example of a MIB                         |
which does this).  Typically, when such a RowStatus object is
created/deleted, then the conceptual row in the ifTable
appears/disappears as a by-product, and an ifIndex value (chosen by the
agent) is stored in an appropriate object in the media-specific MIB.

3.1.18.  All Values Must be Known

There are a number of situations where an agent does not know the value
of one or more objects for a particular interface.  In all such
circumstances, an agent MUST NOT instantiate an object with an incorrect
value; rather, it MUST respond with the appropriate error/exception
condition (e.g., noSuchInstance for SNMPv2).

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

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

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

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4.  Media-Specific MIB Applicability

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

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

Specific areas of clarification include

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

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

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

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

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

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

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5.  Overview

This MIB consists of 4 tables:

ifTable
     This table is the ifTable from MIB-II.

ifXTable
     This table contains objects that have been added to the Interface
     MIB as a result of the Interface Evolution effort, or replacements
     for objects of the original (MIB-II) ifTable that were deprecated
     because the semantics of said objects have significantly changed.
     This table also contains objects that were previously in the
     ifExtnsTable.

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

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

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6.  Interfaces Group Definitions

IF-MIB DEFINITIONS ::= BEGIN

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

ifMIB MODULE-IDENTITY
    LAST-UPDATED "9807161800Z"                                            |
    ORGANIZATION "IETF Interfaces MIB Working Group"
    CONTACT-INFO
            "   Keith McCloghrie
                Cisco Systems, Inc.
                170 West Tasman Drive
                San Jose, CA  95134-1706
                US

                408-526-5260
                [email-masked]"
    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."
    REVISION      "9807161800Z"                                           +
    DESCRIPTION                                                           +
            "Clarifications agreed upon by the Interfaces MIB WG."        +
    REVISION      "9602282155Z"
    DESCRIPTION
            "Revisions made by the Interfaces MIB WG."
    REVISION      "9311082155Z"
    DESCRIPTION
            "Initial revision, published as part of RFC 1573."
    ::= { mib-2 31 }

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ifMIBObjects OBJECT IDENTIFIER ::= { ifMIB 1 }

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

--                                                                        |
-- Textual Conventions                                                    |
--                                                                        |

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

OwnerString ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "255a"
    STATUS       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))

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

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

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

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

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

-- the Interfaces table

-- The Interfaces table contains information on the entity's
-- interfaces.  Each sub-layer below the internetwork-layer
-- of a network interface is considered to be an interface.

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

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

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    ::= { 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

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    STATUS      current
    DESCRIPTION
            "A textual string containing information about the
            interface.  This string should include the name of the
            manufacturer, the product name and the version of the
            interface hardware/software."
    ::= { ifEntry 2 }

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

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

ifSpeed OBJECT-TYPE
    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."

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    ::= { ifEntry 5 }

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

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

ifOperStatus OBJECT-TYPE
    SYNTAX  INTEGER {
                up(1),        -- ready to pass packets
                down(2),
                testing(3),   -- in some test mode
                unknown(4),   -- status can not be determined
                              -- for some reason.
                dormant(5),
                notPresent(6),    -- some component is missing
                lowerLayerDown(7) -- down due to state of

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                                  -- lower-layer interface(s)
            }
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The current operational state of the interface.  The
            testing(3) state indicates that no operational packets can
            be passed.  If ifAdminStatus is down(2) then ifOperStatus
            should be down(2).  If ifAdminStatus is changed to up(1)
            then ifOperStatus should change to up(1) if the interface is
            ready to transmit and receive network traffic; it should
            change to dormant(5) if the interface is waiting for
            external actions (such as a serial line waiting for an
            incoming connection); it should remain in the down(2) state
            if and only if there is a fault that prevents it from going
            to the up(1) state; it should remain in the notPresent(6)
            state if the interface has missing (typically, hardware)
            components."
    ::= { ifEntry 8 }

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

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

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

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

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

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

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

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

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

            Discontinuities in the value of this counter can occur at

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

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

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

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

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

ifOutOctets OBJECT-TYPE

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

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

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

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

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

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

            This object is deprecated in favour of ifOutMulticastPkts

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            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.

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

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

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

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

ifSpecific OBJECT-TYPE

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    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 1903.  In fact, it is
            recommended that the media-specific MIB specify what value
            ifSpecific should/can take for values of ifType.  If no MIB
            definitions specific to the particular media are available,
            the value should be set to the OBJECT IDENTIFIER { 0 0 }."
    ::= { ifEntry 22 }

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

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

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

IfXEntry ::=

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    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,
        ifAlias                 DisplayString,
        ifCounterDiscontinuityTime TimeStamp
    }

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

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

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

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 2 }

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

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

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

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

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            ifCounterDiscontinuityTime."
    ::= { ifXEntry 4 }

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

            Discontinuities in the value of this counter can occur at
            re-initialization of the management system, and at other
            times as indicated by the value of
            ifCounterDiscontinuityTime."
    ::= { ifXEntry 5 }

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

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

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

ifHCInUcastPkts OBJECT-TYPE
    SYNTAX      Counter64
    MAX-ACCESS  read-only

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

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

ifHCInMulticastPkts OBJECT-TYPE
    SYNTAX      Counter64
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The number of packets, delivered by this sub-layer to a
            higher (sub-)layer, which were addressed to a multicast
            address at this sub-layer.  For a MAC layer protocol, this
            includes both Group and Functional addresses.  This object
            is a 64-bit version of ifInMulticastPkts.

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

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

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

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

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

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

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

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

            Discontinuities in the value of this counter can occur at

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

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

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

ifLinkUpDownTrapEnable  OBJECT-TYPE
    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

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            which do not vary in bandwidth or for those where no
            accurate estimation can be made, this object should contain
            the nominal bandwidth.  For a sub-layer which has no concept
            of bandwidth, this object should be zero."
    ::= { ifXEntry 15 }

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

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

ifConnectorPresent   OBJECT-TYPE
    SYNTAX      TruthValue
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "This object has the value 'true(1)' if the interface
            sublayer has a physical connector and the value 'false(2)'
            otherwise."
    ::= { ifXEntry 17 }

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

            On the first instantiation of an interface, the value of
            ifAlias associated with that interface is the zero-length
            string.  As and when a value is written into an instance of

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            ifAlias through a network management set operation, then the
            agent must retain the supplied value in the ifAlias instance
            associated with the same interface for as long as that
            interface remains instantiated, including across all re-
            initializations/reboots of the network management system,
            including those which result in a change of the interface's
            ifIndex value.

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

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

ifCounterDiscontinuityTime OBJECT-TYPE
    SYNTAX      TimeStamp
    MAX-ACCESS  read-only
    STATUS      current
    DESCRIPTION
            "The value of sysUpTime on the most recent occasion at which
            any one or more of this interface's counters suffered a
            discontinuity.  The relevant counters are the specific
            instances associated with this interface of any Counter32 or
            Counter64 object contained in the ifTable or ifXTable.  If
            no such discontinuities have occurred since the last re-
            initialization of the local management subsystem, then this
            object contains a zero value."
    ::= { ifXEntry 19 }

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

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

              ifStackStatus.x.y=active

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

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

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

ifStackEntry  OBJECT-TYPE
     SYNTAX        IfStackEntry
     MAX-ACCESS    not-accessible
     STATUS        current
     DESCRIPTION
            "Information on a particular relationship between two sub-
            layers, specifying that one sub-layer runs on 'top' of the

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            other sub-layer.  Each sub-layer corresponds to a conceptual
            row in the ifTable."
     INDEX { ifStackHigherLayer, ifStackLowerLayer }
     ::= { ifStackTable 1 }

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

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

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

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

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

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

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

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

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

            - for an interface operating in promiscuous mode, entries

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

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

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

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

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

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

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

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            "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 }

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-- 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 is about to enter the down
            state from some other state (but not from the notPresent
            state).  This other state is indicated by the included value
            of ifOperStatus."
    ::= { snmpTraps 3 }

linkUp NOTIFICATION-TYPE
        OBJECTS { ifIndex, ifAdminStatus, ifOperStatus }
        STATUS  current
        DESCRIPTION
            "A linkUp trap signifies that the SNMPv2 entity,              |
            acting in an agent role, has detected that the ifOperStatus
            object for one of its communication links left the down
            state and transitioned into some other state (but not into
            the notPresent state).  This other state is indicated by the
            included value of ifOperStatus."
    ::= { snmpTraps 4 }

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-- conformance information

ifConformance OBJECT IDENTIFIER ::= { ifMIB 2 }

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

-- compliance statements

ifCompliance3 MODULE-COMPLIANCE                                           |
    STATUS  current
    DESCRIPTION
            "The compliance statement for SNMPv2 entities which have
            network interfaces."

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

-- The groups:                                                            +
--        ifFixedLengthGroup                                              +
--        ifHCFixedLengthGroup                                            +
--        ifPacketGroup                                                   +
--        ifHCPacketGroup                                                 +
--        ifVHCPacketGroup                                                +
-- are mutually exclusive; at most one of these groups is implemented     +
-- for a particular interface                                             +

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

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

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

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

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

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

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

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

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

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

    ::= { ifCompliances 3 }                                               |

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-- units of conformance

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

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

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

ifHCFixedLengthGroup    OBJECT-GROUP
    OBJECTS { ifHCInOctets, ifHCOutOctets,
              ifInOctets, ifOutOctets, ifInUnknownProtos,
              ifInErrors, ifOutErrors }
    STATUS  current
    DESCRIPTION
            "A collection of objects providing information specific to
            high speed (greater than 20,000,000 bits/second) character-
            oriented or fixed-length-transmission network interfaces."
    ::= { ifGroups 3 }

ifPacketGroup    OBJECT-GROUP
    OBJECTS { ifInOctets, ifOutOctets, ifInUnknownProtos,
              ifInErrors, ifOutErrors,
              ifMtu, ifInUcastPkts, ifInMulticastPkts,
              ifInBroadcastPkts, ifInDiscards,

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              ifOutUcastPkts, ifOutMulticastPkts,
              ifOutBroadcastPkts, ifOutDiscards,
              ifPromiscuousMode }
    STATUS  current
    DESCRIPTION
            "A collection of objects providing information specific to
            non-high speed (non-high speed interfaces transmit and
            receive at speeds less than or equal to 20,000,000
            bits/second) packet-oriented network interfaces."
    ::= { ifGroups 4 }

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

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

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    ::= { ifGroups 6 }

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

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

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

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-- Deprecated Definitions - Objects

--
--    The Interface Test Table
--
-- This group of objects is optional.  However, a media-specific
-- MIB may make implementation of this group mandatory.
--
-- This table replaces the ifExtnsTestTable
--

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

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

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

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                 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

           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

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           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 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

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           constraints, make available at least the minimum amount of
           information after that test completes."
    ::= { ifMIBObjects 3 }

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

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

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

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

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

                noTest  OBJECT IDENTIFIER ::= { 0 0 }

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

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

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

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    ::= { ifTestEntry 4 }

ifTestCode  OBJECT-TYPE
    SYNTAX       OBJECT IDENTIFIER
    MAX-ACCESS   read-only
    STATUS       deprecated
    DESCRIPTION
            "This object contains a code which contains more specific
            information on the test result, for example an error-code
            after a failed test.  Error codes and other values this
            object may take are specific to the type of interface and/or
            test.  The value may have the semantics of either the
            AutonomousType or InstancePointer textual conventions as
            defined in RFC 1903.  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       deprecated
    DESCRIPTION
            "The entity which currently has the 'ownership' required to
            invoke a test on this interface."
    ::= { ifTestEntry 6 }

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-- Deprecated Definitions - Groups

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

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

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

ifOldObjectsGroup    OBJECT-GROUP
    OBJECTS { ifInNUcastPkts, ifOutNUcastPkts,
              ifOutQLen, ifSpecific }
    STATUS  deprecated
    DESCRIPTION
            "The collection of objects deprecated from the original
            MIB-II interfaces group."
    ::= { ifGroups 12 }

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-- Deprecated Definitions - Compliance

ifCompliance MODULE-COMPLIANCE
    STATUS  deprecated
    DESCRIPTION
            "The previous 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
        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."

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

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

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

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

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

ifCompliance2 MODULE-COMPLIANCE                                           +
    STATUS  obsolete                                                      +
    DESCRIPTION                                                           +
            "The compliance statement for SNMPv2 entities which have      +
            network interfaces."                                          +

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

        GROUP       ifFixedLengthGroup                                    +
        DESCRIPTION                                                       +

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

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

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

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

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

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

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

        OBJECT      ifStackStatus                                         +
        SYNTAX      INTEGER { active(1) } -- subset of RowStatus          +
        MIN-ACCESS  read-only                                             +
        DESCRIPTION                                                       +

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            "Write access is not required, and only one of the six        +
            enumerated values for the RowStatus textual convention need   +
            be supported, specifically: active(1)."                       +

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

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

    ::= { ifCompliances 2 }                                               +

END

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7.  Acknowledgements

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

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

8.  References                                                            -

[1]  Harrington, D., Presuhn, R., and B. Wijnen, "An Architecture for     |
     Describing SNMP Management Frameworks", RFC 2271, Cabletron          |
     Systems, Inc., BMC Software, Inc., IBM T. J. Watson Research,        |
     January 1998                                                         |

[2]  Rose, M., and K. McCloghrie, "Structure and Identification of        |
     Management Information for TCP/IP-based Internets", RFC 1155,        |
     Performance Systems International, Hughes LAN Systems, May 1990      |

[3]  Rose, M., and K. McCloghrie, "Concise MIB Definitions", RFC 1212,    |
     Performance Systems International, Hughes LAN Systems, March 1991    |

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

[5]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S.     +
     Waldbusser, "Structure of Management Information for Version 2 of    +
     the Simple Network Management Protocol (SNMPv2)", RFC 1902, SNMP     +
     Research,Inc., Cisco Systems, Inc., Dover Beach Consulting, Inc.,    +
     International Network Services, January 1996.                        +

[6]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S.     +
     Waldbusser, "Textual Conventions for Version 2 of the Simple         +
     Network Management Protocol (SNMPv2)", RFC 1903, SNMP Research,      +
     Inc., Cisco Systems, Inc., Dover Beach Consulting, Inc.,             +
     International Network Services, January 1996.                        +

[7]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S.     +
     Waldbusser, "Conformance Statements for Version 2 of the Simple      +
     Network Management Protocol (SNMPv2)", RFC 1904, SNMP Research,      +
     Inc., Cisco Systems, Inc., Dover Beach Consulting, Inc.,             +
     International Network Services, January 1996.                        +

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[8]  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.                                      +

[9]  SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S.     +
     Waldbusser, "Introduction to Community-based SNMPv2", RFC 1901,      +
     SNMP Research, Inc., Cisco Systems, Inc., Dover Beach Consulting,    +
     Inc., International Network Services, January 1996.                  +

[10] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S.     +
     Waldbusser, "Transport Mappings for Version 2 of the Simple Network  +
     Management Protocol (SNMPv2)", RFC 1906, SNMP Research, Inc., Cisco  +
     Systems, Inc., Dover Beach Consulting, Inc., International Network   +
     Services, January 1996.                                              +

[11] Case, J., Harrington D., Presuhn R., and B. Wijnen, "Message         +
     Processing and Dispatching for the Simple Network Management         +
     Protocol (SNMP)", RFC 2272, SNMP Research, Inc., Cabletron Systems,  +
     Inc., BMC Software, Inc., IBM T. J. Watson Research, January 1998.   +

[12] Blumenthal, U., and B. Wijnen, "User-based Security Model (USM) for  +
     version 3 of the Simple Network Management Protocol (SNMPv3)", RFC   +
     2274, IBM T. J. Watson Research, January 1998.                       +

[13] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S.     +
     Waldbusser, "Protocol Operations for Version 2 of the Simple         +
     Network Management Protocol (SNMPv2)", RFC 1905, SNMP Research,      +
     Inc., Cisco Systems, Inc., Dover Beach Consulting, Inc.,             +
     International Network Services, January 1996.                        +

[14] Levi, D., Meyer, P., and B. Stewart, MPv3 Applications", RFC 2273,   +
     SNMP Research, Inc., Secure Computing Corporation, Cisco Systems,    +
     January 1998.                                                        +

[15] Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based Access       +
     Control Model (VACM) for the Simple Network Management Protocol      +
     (SNMP)", RFC 2275, IBM T. J. Watson Research, BMC Software, Inc.,    +
     Cisco Systems, Inc., January 1998.                                   +

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

[17]                                                                      +
     McCloghrie, K., and M. Rose, "Management Information Base for

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     Network Management of TCP/IP-based internets - MIB-II", RFC 1213,    |
     Hughes LAN Systems, Performance Systems International,               |
     March 1991.

[18] J. Postel, "Internet Protocol", RFC 791, Information Sciences
     Institute, USC, September 1981.

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

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

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

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9.  Security Considerations

This MIB contains both readable objects whose values provide the number
and status of a device's network interfaces, and write-able objects
which allow an administrator to control the interfaces and to perform
tests on the interfaces.  Unauthorized access to the readable objects is
relatively innocuous.  Unauthorized access to the write-able objects
could cause a denial of service, or in combination with other (e.g.,
physical) security breaches, could cause unauthorized connectivity to a
device.

10.  Authors' Addresses

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

     Phone: 408-526-5260
     Email: [email-masked]"

     Frank Kastenholz
     Argon Networks                                                       |
     25 Porter Rd                                                         |
     Littleton Ma 01460                                                   |

     Phone: (508)685-4000
     Email: [email-masked]                                              |

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11.  Changes from RFC 2233

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

     Modified syntax of ifStackHigherLayer and ifStackLowerLayer to be    +
     InterfaceIndexOrZero.                                                +

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

     Corrected a typo in the DESCRIPTION of the linkUp notification.      +

     Added Copyright notices.                                             +

     Modified the introductory SNMP Network Management Framework          +
     boilerplate text.                                                    +

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12.  Full Copyright Statement                                             +

Copyright (C) The Internet Society (1998).  All Rights Reserved.          +

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

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

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

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Table of Contents

1 Introduction ....................................................    2
2 The SNMP Network Management Framework ...........................    2
3 Experience with the Interfaces Group ............................    3
3.1 Clarifications/Revisions ......................................    4
3.1.1 Interface Sub-Layers ........................................    4
3.1.2 Guidance on Defining Sub-layers .............................    7
3.1.3 Virtual Circuits ............................................    8
3.1.4 Bit, Character, and Fixed-Length Interfaces .................    9
3.1.5 Interface Numbering .........................................   11
3.1.6 Counter Size ................................................   15
3.1.7 Interface Speed .............................................   17
3.1.8 Multicast/Broadcast Counters ................................   18
3.1.9 Trap Enable .................................................   19
3.1.10 Addition of New ifType values ..............................   19
3.1.11 InterfaceIndex Textual Convention ..........................   19
3.1.12 New states for IfOperStatus ................................   20
3.1.13 IfAdminStatus and IfOperStatus .............................   21
3.1.14 IfOperStatus in an Interface Stack .........................   22
3.1.15 Traps ......................................................   22
3.1.16 ifSpecific .................................................   24
3.1.17 Creation/Deletion of Interfaces ............................   24
3.1.18 All Values Must be Known ...................................   25
4 Media-Specific MIB Applicability ................................   26
5 Overview ........................................................   27
6 Interfaces Group Definitions ....................................   28
7 Acknowledgements ................................................   72
8 References ......................................................   72
9 Security Considerations .........................................   75
10 Authors' Addresses .............................................   75
11 Changes from RFC 2233 ..........................................   76
12 Full Copyright Statement .......................................   77

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