

Network Working Group                                            R. Frye
Request for Comments: 3584                             Vibrant Solutions
BCP: 74                                                          D. Levi
Obsoletes: 2576                                          Nortel Networks
Category: Best Current Practice                              S. Routhier
                                                Wind River Systems, Inc.
                                                               B. Wijnen
                                                     Lucent Technologies
                                                             August 2003


        Coexistence between Version 1, Version 2, and Version 3
         of the Internet-standard Network Management Framework

Status of this Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   The purpose of this document is to describe coexistence between
   version 3 of the Internet-standard Network Management Framework,
   (SNMPv3), version 2 of the Internet-standard Network Management
   Framework (SNMPv2), and the original Internet-standard Network
   Management Framework (SNMPv1).  This document also describes how to
   convert MIB modules from SMIv1 format to SMIv2 format.  This document
   obsoletes RFC 2576.


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Table Of Contents

   1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . .    3
       1.1.  SNMPv1 . . . . . . . . . . . . . . . . . . . . . . . .    4
       1.2.  SNMPv2 . . . . . . . . . . . . . . . . . . . . . . . .    4
       1.3.  SNMPv3 . . . . . . . . . . . . . . . . . . . . . . . .    5
   2.  SMI and Management Information Mappings. . . . . . . . . . .    5
       2.1.  MIB Modules. . . . . . . . . . . . . . . . . . . . . .    6
             2.1.1.  Object Definitions . . . . . . . . . . . . . .    6
             2.1.2.  Trap and Notification Definitions  . . . . . .    8
       2.2.  Compliance Statements. . . . . . . . . . . . . . . . .    9
       2.3.  Capabilities Statements. . . . . . . . . . . . . . . .    9
   3.  Translating Notification Parameters. . . . . . . . . . . . .   10
       3.1.  Translating  SNMPv1  Notification  Parameters  to
             SNMPv2 Notification Parameters . . . . . . . . . . . .   11
       3.2.  Translating  SNMPv2  Notification  Parameters  to
             SNMPv1 Notification Parameters . . . . . . . . . . . .   12
   4.  Approaches to Coexistence in a Multi-lingual Network . . . .   14
       4.1.  SNMPv1 and SNMPv2 Access to MIB Data . . . . . . . . .   14
       4.2.  Multi-lingual implementations. . . . . . . . . . . . .   15
             4.2.1.  Command Generator. . . . . . . . . . . . . . .   15
             4.2.2.  Command Responder. . . . . . . . . . . . . . .   16
                     4.2.2.1.  Handling Counter64 . . . . . . . . .   16
                     4.2.2.2.  Mapping SNMPv2 Exceptions. . . . . .   17
                               4.2.2.2.1. Mapping noSuchObject
                                          and noSuchInstance. . . .   18
                               4.2.2.2.2. Mapping endOfMibView. . .   18
                     4.2.2.3.  Processing An SNMPv1 GetReques . . .   18
                     4.2.2.4.  Processing An SNMPv1 GetNextRequest.   19
                     4.2.2.5.  Processing An SNMPv1 SetRequest. . .   20
             4.2.3.  Notification Originator. . . . . . . . . . . .   21
             4.2.4.  Notification Receiver. . . . . . . . . . . . .   21
       4.3.  Proxy Implementations. . . . . . . . . . . . . . . . .   22
             4.3.1.  Upstream Version Greater Than Downstream
                     Version. . . . . . . . . . . . . . . . . . . .   22
             4.3.2.  Upstream Version Less Than Downstream Version.   23
       4.4.  Error Status Mappings. . . . . . . . . . . . . . . . .   25
   5.  Message Processing Models and Security Models. . . . . . . .   26
       5.1.  Mappings . . . . . . . . . . . . . . . . . . . . . . .   26
       5.2.  The SNMPv1 MP Model and SNMPv1  Community-based
             Security Model . . . . . . . . . . . . . . . . . . . .   26
             5.2.1.  Processing An Incoming Request . . . . . . . .   27
             5.2.2.  Generating An Outgoing Response. . . . . . . .   29
             5.2.3.  Generating An Outgoing Notification. . . . . .   29
             5.2.4.  Proxy Forwarding Of Requests . . . . . . . . .   30
       5.3.  The SNMP Community MIB Module. . . . . . . . . . . . .   30
   6.  Intellectual Property Statement. . . . . . . . . . . . . . .   42
   7.  Acknowledgments. . . . . . . . . . . . . . . . . . . . . . .   43


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   8.  Security Considerations. . . . . . . . . . . . . . . . . . .   43
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . .   44
       9.1.  Normative References . . . . . . . . . . . . . . . . .   44
       9.2.  Informative References . . . . . . . . . . . . . . . .   46
   Appendix A.  Change Log. . . . . . . . . . . . . . . . . . . . .   47
       A.1. Changes From RFC 2576 . . . . . . . . . . . . . . . . .   47
       A.2. Changes Between RFC 1908 and RFC 2576 . . . . . . . . .   49
   Editors' Addresses . . . . . . . . . . . . . . . . . . . . . . .   50
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . .   51

1.  Overview

   The purpose of this document is to describe coexistence between
   version 3 of the Internet-standard Network Management Framework,
   termed the SNMP version 3 framework (SNMPv3), version 2 of the
   Internet-standard Network Management Framework, termed the SNMP
   version 2 framework (SNMPv2), and the original Internet-standard
   Network Management Framework (SNMPv1).

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

   There are four general aspects of coexistence described in this
   document.  Each of these is described in a separate section:

   -  Conversion of MIB documents between SMIv1 and SMIv2 formats is
      documented in section 2.

   -  Mapping of notification parameters is documented in section 3.

   -  Approaches to coexistence between entities which support the
      various versions of SNMP in a multi-lingual network is documented
      in section 4.  This section addresses the processing of protocol
      operations in multi-lingual implementations, as well as behaviour
      of proxy implementations.

   -  The SNMPv1 Message Processing Model and Community-Based Security
      Model, which provides mechanisms for adapting SNMPv1 into the
      View-Based Access Control Model (VACM) [20], is documented in
      section 5 (this section also addresses the SNMPv2c Message
      Processing Model and Community-Based Security Model).


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1.1.  SNMPv1

   SNMPv1 is defined by these documents:

   -  STD 15, RFC 1157 [RFC1157] which defines the Simple Network
      Management Protocol (SNMPv1), the protocol used for network access
      to managed objects.

   -  STD 16, RFC 1155 [RFC1155] which defines the Structure of
      Management Information (SMIv1), the mechanisms used for describing
      and naming objects for the purpose of management.

   -  STD 16, RFC 1212 [RFC1212] which defines a more concise
      description mechanism, which is wholly consistent with the SMIv1.

   -  RFC 1215 [RFC1215] which defines a convention for defining Traps
      for use with the SMIv1.

   Note that throughout this document, the term 'SMIv1' is used.  This
   term generally refers to the information presented in RFC 1155, RFC
   1212, and RFC 1215.

1.2.  SNMPv2

   SNMPv2 is defined by these documents:

   -  STD 58, RFC 2578 which defines Version 2 of the Structure of
      Management Information (SMIv2) [RFC2578].

   -  STD 58, RFC 2579 which defines common MIB "Textual Conventions"
      [RFC2579].

   -  STD 58, RFC 2580 which defines Conformance Statements and
      requirements for defining agent and manager capabilities
      [RFC2580].

   -  STD 62, RFC 3416 which defines the Protocol Operations used in
      processing [RFC3416].

   -  STD 62, RFC 3417 which defines the Transport Mappings used "on the
      wire" [RFC3417].

   -  STD 62, RFC 3418 which defines the basic Management Information
      Base for monitoring and controlling some basic common functions of
      SNMP entities [RFC3418].

   Note that SMIv2 as used throughout this document refers to the first
   three documents listed above (RFCs 2578, 2579, and 2580).


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   The following document augments the definition of SNMPv2:

   -  RFC 1901 [RFC1901] is an Experimental definition for using SNMPv2
      PDUs within a community-based message wrapper.  This is referred
      to throughout this document as SNMPv2c.

1.3.  SNMPv3

   SNMPv3 is defined by these documents:

   -  STD 62, RFC 3411 which defines an Architecture for Describing SNMP
      Management Frameworks [RFC3411].

   -  STD 62, RFC 3412 which defines Message Processing and Dispatching
      [RFC3412].

   -  STD 62, RFC 3413 which defines various SNMP Applications
      [RFC3413].

   -  STD 62, RFC 3414 which defines the User-based Security Model
      (USM), providing for both Authenticated and Private (encrypted)
      SNMP messages [RFC3414].

   -  STD 62, RFC 3415 which defines the View-based Access Control Model
      (VACM), providing the ability to limit access to different MIB
      objects on a per-user basis [RFC3415].

   SNMPv3 also uses the SNMPv2 definitions of RFCs 3416 through 3418 and
   the SMIv2 definitions of 2578 through 2580 described above.  Note
   that text throughout this document that refers to SNMPv2 PDU types
   and protocol operations applies to both SNMPv2c and SNMPv3.

2.  SMI and Management Information Mappings

   The SMIv2 approach towards describing collections of managed objects
   is nearly a proper superset of the approach defined in the SMIv1.
   For example, both approaches use an adapted subset of ASN.1 [ASN1] as
   the basis for a formal descriptive notation.  Indeed, one might note
   that the SMIv2 approach largely codifies the existing practice for
   defining MIB modules, based on extensive experience with the SMIv1.

   The following sections consider the three areas:  MIB modules,
   compliance statements, and capabilities statements.


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2.1.  MIB Modules

   MIB modules defined using the SMIv1 may continue to be used with
   protocol versions which use SNMPv2 PDUs.  However, for SMIv1 MIB
   modules to conform to the SMIv2, the following changes SHALL be made:

2.1.1.  Object Definitions

   In general, conversion of a MIB module does not require the
   deprecation of the objects contained therein.  If the definition of
   an object is truly inadequate for its intended purpose, the object
   SHALL be deprecated or obsoleted, otherwise deprecation is not
   required.

   (1)  The IMPORTS statement MUST reference SNMPv2-SMI, instead of
        RFC1155-SMI and RFC-1212.

   (2)  The MODULE-IDENTITY macro MUST be invoked immediately after any
        IMPORTs statement.

   (3)  For any object with a SYNTAX clause value of Counter, the object
        MUST have the value of its SYNTAX clause changed to Counter32.

   (4)  For any object with a SYNTAX clause value of Gauge, the object
        MUST have the value of its SYNTAX clause changed to Gauge32, or
        Unsigned32 where appropriate.

   (5)  For all objects, the ACCESS clause MUST be replaced by a MAX-
        ACCESS clause.  The value of the MAX-ACCESS clause SHALL be the
        same as that of the ACCESS clause unless some other value makes
        "protocol sense" as the maximal level of access for the object.
        In particular, object types for which instances can be
        explicitly created by a protocol set operation, SHALL have a
        MAX-ACCESS clause of "read-create".  If the value of the ACCESS
        clause is "write-only", then the value of the MAX-ACCESS clause
        MUST be "read-write", and the DESCRIPTION clause SHALL note that
        reading this object will result in implementation-specific
        results.  Note that in SMIv1, the ACCESS clause specifies the
        minimal required access, while in SMIv2, the MAX-ACCESS clause
        specifies the maximum allowed access.  This should be considered
        when converting an ACCESS clause to a MAX-ACCESS clause.

   (6)  For all objects, if the value of the STATUS clause is
        "mandatory" or "optional", the value MUST be replaced with
        "current", "deprecated", or "obsolete" depending on the current
        usage of such objects.


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   (7)  For any object not containing a DESCRIPTION clause, the object
        MUST have a DESCRIPTION clause defined.

   (8)  For any object corresponding to a conceptual row which does not
        have an INDEX clause, the object MUST have either an INDEX
        clause or an AUGMENTS clause defined.

   (9)  If any INDEX clause contains a reference to an object with a
        syntax of NetworkAddress, then a new object MUST be created and
        placed in this INDEX clause immediately preceding the object
        whose syntax is NetworkAddress.  This new object MUST have a
        syntax of INTEGER, it MUST be not-accessible, and its value MUST
        always be 1.  The effect of this, and the preceding bullet, is
        to allow one to convert a MIB module in SMIv1 format to one in
        SMIv2 format, and then use it with the SNMPv1 protocol with no
        impact to existing SNMPv1 agents and managers.

   (10) For any object with a SYNTAX of NetworkAddress, the SYNTAX MUST
        be changed to IpAddress.  Note that the use of NetworkAddress in
        new MIB documents is strongly discouraged (in fact, new MIB
        documents should be written using SMIv2, which does not define
        NetworkAddress).

   (11) For any object containing a DEFVAL clause with an OBJECT
        IDENTIFIER value which is expressed as a collection of sub-
        identifiers, the value MUST be changed to reference a single
        ASN.1 identifier.  This may require defining a series of new
        administrative assignments (OBJECT IDENTIFIERS) in order to
        define the single ASN.1 identifier.

   (12) One or more OBJECT-GROUPS MUST be defined, and related objects
        MUST be collected into appropriate groups.  Note that SMIv2
        requires all OBJECT-TYPEs to be a member of at least one
        OBJECT-GROUP.

   (13) For any non-columnar object that is instanced as if it were
        immediately subordinate to a conceptual row, the value of the
        STATUS clause of that object MUST be changed to "obsolete".

   (14) For any conceptual row object that is not immediately
        subordinate to a conceptual table, the value of the STATUS
        clause of that object (and all subordinate objects) MUST be
        changed to "obsolete".


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   Other changes are desirable, but not necessary:

   (1)  Creation and deletion of conceptual rows is inconsistent using
        the SMIv1.  The SMIv2 corrects this.  As such, if the MIB module
        undergoes review early in its lifetime, and it contains
        conceptual tables which allow creation and deletion of
        conceptual rows, then the objects relating to those tables MAY
        be deprecated and replaced with objects defined using the new
        approach.  The approach based on SMIv2 can be found in section 7
        of RFC 2578 [RFC2578], and the RowStatus and StorageType
        TEXTUAL-CONVENTIONs are described in section 2 of RFC 2579
        [RFC2579].

   (2)  For any object with an integer-valued SYNTAX clause, in which
        the corresponding INTEGER does not have a range restriction
        (i.e., the INTEGER has neither a defined set of named-number
        enumerations nor an assignment of lower- and upper-bounds on its
        value), the object SHOULD have the value of its SYNTAX clause
        changed to Integer32, or have an appropriate range specified.

   (3)  For any object with a string-valued SYNTAX clause, in which the
        corresponding OCTET STRING does not have a size restriction
        (i.e., the OCTET STRING has no assignment of lower- and upper-
        bounds on its length), the bounds for the size of the object
        SHOULD be defined.

   (4)  All textual conventions informally defined in the MIB module
        SHOULD be redefined using the TEXTUAL-CONVENTION macro.  Such a
        change would not necessitate deprecating objects previously
        defined using an informal textual convention.

   (5)  For any object which represents a measurement in some kind of
        units, a UNITS clause SHOULD be added to the definition of that
        object.

   (6)  For any conceptual row which is an extension of another
        conceptual row, i.e., for which subordinate columnar objects
        both exist and are identified via the same semantics as the
        other conceptual row, an AUGMENTS clause SHOULD be used in place
        of the INDEX clause for the object corresponding to the
        conceptual row which is an extension.

2.1.2.  Trap and Notification Definitions

   If a MIB module is changed to conform to the SMIv2, then each
   occurrence of the TRAP-TYPE macro MUST be changed to a corresponding
   invocation of the NOTIFICATION-TYPE macro:


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   (1)  The IMPORTS statement MUST NOT reference RFC-1215 [RFC1215], and
        MUST reference SNMPv2-SMI instead.

   (2)  The ENTERPRISE clause MUST be removed.

   (3)  The VARIABLES clause MUST be renamed to the OBJECTS clause.

   (4)  A STATUS clause MUST be added, with an appropriate value.
        Normally the value should be 'current', although 'deprecated' or
        'obsolete' may be used as needed.

   (5)  The value of an invocation of the NOTIFICATION-TYPE macro is an
        OBJECT IDENTIFIER, not an INTEGER, and MUST be changed
        accordingly.  Specifically, if the value of the ENTERPRISE
        clause is not 'snmp' then the value of the invocation SHALL be
        the value of the ENTERPRISE clause extended with two sub-
        identifiers, the first of which has the value 0, and the second
        has the value of the invocation of the TRAP-TYPE.  If the value
        of the ENTERPRISE clause is 'snmp', then the value of the
        invocation of the NOTIFICATION-TYPE macro SHALL be mapped in the
        same manner as described in section 3.1 in this document.

   (6)  A DESCRIPTION clause MUST be added, if not already present.

   (7)  One or more NOTIFICATION-GROUPs MUST be defined, and related
        notifications MUST be collected into those groups.  Note that
        SMIv2 requires that all NOTIFICATION-TYPEs be a member of at
        least one NOTIFICATION-GROUP.

2.2.  Compliance Statements

   For those information modules which are "standards track", a
   corresponding invocation of the MODULE-COMPLIANCE macro and related
   OBJECT-GROUP and/or NOTIFICATION-GROUP macros MUST be included within
   the information module (or in a companion information module), and
   any commentary text in the information module which relates to
   compliance SHOULD be removed.  Typically this editing can occur when
   the information module undergoes review.

   Note that a MODULE-COMPLIANCE statement is not required for a MIB
   document that is not on the standards track (for example, an
   enterprise MIB), though it may be useful in some circumstances to
   define a MODULE-COMPLIANCE statement for such a MIB document.

2.3.  Capabilities Statements

   RFC 1303 [RFC1303] uses the MODULE-CONFORMANCE macro to describe an
   agent's capabilities with respect to one or more MIB modules.


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   Converting such a description for use with the SMIv2 requires these
   changes:

   (1)  The macro name AGENT-CAPABILITIES MUST be used instead of
        MODULE-CONFORMANCE.

   (2)  The STATUS clause MUST be added, with a value of 'current'.

   (3)  All occurrences of the CREATION-REQUIRES clause MUST either be
        omitted if appropriate, or be changed such that the semantics
        are consistent with RFC 2580 [RFC2580].

   In order to ease coexistence, object groups defined in an SMIv1
   compliant MIB module may be referenced by the INCLUDES clause of an
   invocation of the AGENT-CAPABILITIES macro:  upon encountering a
   reference to an OBJECT IDENTIFIER subtree defined in an SMIv1 MIB
   module, all leaf objects which are subordinate to the subtree and
   have a STATUS clause value of mandatory are deemed to be INCLUDEd.
   (Note that this method is ambiguous when different revisions of an
   SMIv1 MIB have different sets of mandatory objects under the same
   subtree; in such cases, the only solution is to rewrite the MIB using
   the SMIv2 in order to define the object groups unambiguously.)

3.  Translating Notification Parameters

   This section describes how parameters used for generating
   notifications are translated between the format used for SNMPv1
   notification protocol operations and the format used for SNMPv2
   notification protocol operations.  The parameters used to generate a
   notification are called 'notification parameters'.  The format of
   parameters used for SNMPv1 notification protocol operations is
   referred to in this document as 'SNMPv1 notification parameters'.
   The format of parameters used for SNMPv2 notification protocol
   operations is referred to in this document as 'SNMPv2 notification
   parameters'.

   The situations where notification parameters MUST be translated are:

   -  When an entity generates a set of notification parameters in a
      particular format, and the configuration of the entity indicates
      that the notification must be sent using an SNMP message version
      that requires the other format for notification parameters.

   -  When a proxy receives a notification that was sent using an SNMP
      message version that requires one format of notification
      parameters, and must forward the notification using an SNMP
      message version that requires the other format of notification
      parameters.


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   In addition, it MAY be desirable to translate notification parameters
   in a notification receiver application in order to present
   notifications to the end user in a consistent format.

   Note that for the purposes of this section, the set of notification
   parameters is independent of whether the notification is to be sent
   as a trap or an inform.

   SNMPv1 notification parameters consist of:

   -  An enterprise parameter (OBJECT IDENTIFIER).

   -  An agent-addr parameter (NetworkAddress).

   -  A generic-trap parameter (INTEGER).

   -  A specific-trap parameter (INTEGER).

   -  A time-stamp parameter (TimeTicks).

   -  A list of variable-bindings (VarBindList).

   SNMPv2 notification parameters consist of:

   -  A sysUpTime parameter (TimeTicks).  This appears in the first
      variable-binding in an SNMPv2-Trap-PDU or InformRequest-PDU.

   -  An snmpTrapOID parameter (OBJECT IDENTIFIER).  This appears in the
      second variable-binding in an SNMPv2-Trap-PDU or InformRequest-
      PDU, and is equal to the value portion of that variable-binding
      (not the name portion, as both the name and value are OBJECT
      IDENTIFIERs).

   -  A list of variable-bindings (VarBindList).  This refers to all but
      the first two variable-bindings in an SNMPv2-Trap-PDU or
      InformRequest-PDU.

3.1.  Translating SNMPv1 Notification Parameters to SNMPv2 Notification
      Parameters

   The following procedure describes how to translate SNMPv1
   notification parameters into SNMPv2 notification parameters:

   (1)  The SNMPv2 sysUpTime parameter SHALL be taken directly from the
        SNMPv1 time-stamp parameter.


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   (2)  If the SNMPv1 generic-trap parameter is 'enterpriseSpecific(6)',
        the SNMPv2 snmpTrapOID parameter SHALL be the concatenation of
        the SNMPv1 enterprise parameter and two additional sub-
        identifiers, '0', and the SNMPv1 specific-trap parameter.

   (3)  If the SNMPv1 generic-trap parameter is not
        'enterpriseSpecific(6)', the SNMPv2 snmpTrapOID parameter SHALL
        be the corresponding trap as defined in section 2 of RFC 3418
        [RFC3418]:

        generic-trap
        parameter      snmpTrapOID.0
        ============   =============
        0              1.3.6.1.6.3.1.1.5.1 (coldStart)
        1              1.3.6.1.6.3.1.1.5.2 (warmStart)
        2              1.3.6.1.6.3.1.1.5.3 (linkDown)
        3              1.3.6.1.6.3.1.1.5.4 (linkUp)
        4              1.3.6.1.6.3.1.1.5.5 (authenticationFailure)
        5              1.3.6.1.6.3.1.1.5.6 (egpNeighborLoss)

   (4)  The SNMPv2 variable-bindings SHALL be the SNMPv1 variable-
        bindings.  In addition, if the translation is being performed by
        a proxy in order to forward a received trap, three additional
        variable-bindings will be appended, if these three additional
        variable-bindings do not already exist in the SNMPv1 variable-
        bindings.  The name portion of the first additional variable
        binding SHALL contain snmpTrapAddress.0, and the value SHALL
        contain the SNMPv1 agent-addr parameter.  The name portion of
        the second additional variable binding SHALL contain
        snmpTrapCommunity.0, and the value SHALL contain the value of
        the community-string field from the received SNMPv1 message
        which contained the SNMPv1 Trap-PDU.  The name portion of the
        third additional variable binding SHALL contain
        snmpTrapEnterprise.0 [RFC3418], and the value SHALL be the
        SNMPv1 enterprise parameter.

3.2.  Translating SNMPv2 Notification Parameters to SNMPv1 Notification
      Parameters

   The following procedure describes how to translate SNMPv2
   notification parameters into SNMPv1 notification parameters:

   (1)  The SNMPv1 enterprise parameter SHALL be determined as follows:

      -   If the SNMPv2 snmpTrapOID parameter is one of the standard
          traps as defined in RFC 3418 [RFC3418], then the SNMPv1
          enterprise parameter SHALL be set to the value of the
          variable-binding in the SNMPv2 variable-bindings whose name is


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          snmpTrapEnterprise.0 if that variable-binding exists.  If it
          does not exist, the SNMPv1 enterprise parameter SHALL be set
          to the value 'snmpTraps' as defined in RFC 3418 [RFC3418].

      -   If the SNMPv2 snmpTrapOID parameter is not one of the standard
          traps as defined in RFC 3418 [RFC3418], then the SNMPv1
          enterprise parameter SHALL be determined from the SNMPv2
          snmpTrapOID parameter as follows:

          -  If the next-to-last sub-identifier of the snmpTrapOID value
             is zero, then the SNMPv1 enterprise SHALL be the SNMPv2
             snmpTrapOID value with the last 2 sub-identifiers removed,
             otherwise

          -  If the next-to-last sub-identifier of the snmpTrapOID value
             is non-zero, then the SNMPv1 enterprise SHALL be the SNMPv2
             snmpTrapOID value with the last sub-identifier removed.

   (2)  The SNMPv1 agent-addr parameter SHALL be determined based on the
        situation in which the translation occurs.

      -   If the translation occurs within a notification originator
          application, and the notification is to be sent over IP, the
          SNMPv1 agent-addr parameter SHALL be set to the IP address of
          the SNMP entity in which the notification originator resides.
          If the notification is to be sent over some other transport,
          the SNMPv1 agent-addr parameter SHALL be set to 0.0.0.0.

      -   If the translation occurs within a proxy application, the
          proxy must attempt to extract the original source of the
          notification from the variable-bindings.  If the SNMPv2
          variable-bindings contains a variable binding whose name is
          snmpTrapAddress.0, the agent-addr parameter SHALL be set to
          the value of that variable binding.  Otherwise, the SNMPv1
          agent-addr parameter SHALL be set to 0.0.0.0.

   (3)  If the SNMPv2 snmpTrapOID parameter is one of the standard traps
        as defined in RFC 3418 [RFC3418], the SNMPv1 generic-trap
        parameter SHALL be set as follows:

        snmpTrapOID.0 parameter               generic-trap
        ===============================       ============
        1.3.6.1.6.3.1.1.5.1 (coldStart)                  0
        1.3.6.1.6.3.1.1.5.2 (warmStart)                  1
        1.3.6.1.6.3.1.1.5.3 (linkDown)                   2
        1.3.6.1.6.3.1.1.5.4 (linkUp)                     3
        1.3.6.1.6.3.1.1.5.5 (authenticationFailure)      4
        1.3.6.1.6.3.1.1.5.6 (egpNeighborLoss)            5


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        Otherwise, the SNMPv1 generic-trap parameter SHALL be set to 6.

   (4)  If the SNMPv2 snmpTrapOID parameter is one of the standard traps
        as defined in RFC 3418 [RFC3418], the SNMPv1 specific-trap
        parameter SHALL be set to zero.  Otherwise, the SNMPv1
        specific-trap parameter SHALL be set to the last sub-identifier
        of the SNMPv2 snmpTrapOID parameter.

   (5)  The SNMPv1 time-stamp parameter SHALL be taken directly from the
        SNMPv2 sysUpTime parameter.

   (6)  The SNMPv1 variable-bindings SHALL be the SNMPv2 variable-
        bindings (and note that the SNMPv2 variable-bindings do not
        include the variable-bindings containing sysUpTime.0,
        snmpTrapOID.0).  Note, however, that if the SNMPv2 variable-
        bindings contain any objects whose type is Counter64, the
        translation to SNMPv1 notification parameters cannot be
        performed.  In this case, the notification cannot be encoded in
        an SNMPv1 packet (and so the notification cannot be sent using
        SNMPv1, see section 4.2.3 and section 4.3).

4.  Approaches to Coexistence in a Multi-lingual Network

   There are two basic approaches to coexistence in a multi-lingual
   network, multi-lingual implementations and proxy implementations.
   Multi-lingual implementations allow elements in a network to
   communicate with each other using an SNMP version which both elements
   support.  This allows a multi-lingual implementation to communicate
   with any mono-lingual implementation, regardless of the SNMP version
   supported by the mono-lingual implementation.

   Proxy implementations provide a mechanism for translating between
   SNMP versions using a third party network element.  This allows
   network elements which support only a single, but different, SNMP
   version to communicate with each other.  Proxy implementations are
   also useful for securing communications over an insecure link between
   two locally secure networks.

4.1.  SNMPv1 and SNMPv2 Access to MIB Data

   Throughout section 4., this document refers to 'SNMPv1 Access to MIB
   Data' and 'SNMPv2 Access to MIB Data'.  These terms refer to the part
   of an SNMP agent which actually accesses instances of MIB objects,
   and which actually initiates generation of notifications.
   Differences between the two types of access to MIB data are:

   -  Error-status values generated.


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   -  Generation of exception codes.

   -  Use of the Counter64 data type.

   -  The format of parameters provided when a notification is
      generated.

   SNMPv1 access to MIB data may generate SNMPv1 error-status values,
   will never generate exception codes nor use the Counter64 data type,
   and will provide SNMPv1 format parameters for generating
   notifications.  Note also that SNMPv1 access to MIB data will
   actually never generate a readOnly error (a noSuchName error would
   always occur in the situation where one would expect a readOnly
   error).

   SNMPv2 access to MIB data may generate SNMPv2 error-status values,
   may generate exception codes, may use the Counter64 data type, and
   will provide SNMPv2 format parameters for generating notifications.
   Note that SNMPv2 access to MIB data will never generate readOnly,
   noSuchName, or badValue errors.

   Note that a particular multi-lingual implementation may choose to
   implement all access to MIB data as SNMPv2 access to MIB data, and
   perform the translations described herein for SNMPv1-based
   transactions.

   Further, note that there is no mention of 'SNMPv3 access to MIB data'
   in this document, as SNMPv3 uses SNMPv2 PDU types and protocol
   operations.

4.2.  Multi-lingual implementations

   This approach requires an entity to support multiple SNMP message
   versions.  Typically this means supporting SNMPv1, SNMPv2c, and
   SNMPv3 message versions.  The behaviour of various types of SNMP
   applications which support multiple message versions is described in
   the following sections.  This approach allows entities which support
   multiple SNMP message versions to coexist with and communicate with
   entities which support only a single SNMP message version.

4.2.1.  Command Generator

   A command generator must select an appropriate message version when
   sending requests to another entity.  One way to achieve this is to
   consult a local database to select the appropriate message version.

   In addition, a command generator MUST 'downgrade' GetBulk requests to
   GetNext requests when selecting SNMPv1 as the message version for an


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   outgoing request.  This is done by simply changing the operation type
   to GetNext, ignoring any non-repeaters and max-repetitions values,
   and setting error-status and error-index to zero.

4.2.2.  Command Responder

   A command responder must be able to deal with both SNMPv1 and SNMPv2
   access to MIB data.  There are three aspects to dealing with this.  A
   command responder must:

   -  Deal correctly with SNMPv2 access to MIB data that returns a
      Counter64 value while processing an SNMPv1 message,

   -  Deal correctly with SNMPv2 access to MIB data that returns one of
      the three exception values while processing an SNMPv1 message, and

   -  Map SNMPv2 error codes returned from SNMPv2 access to MIB data
      into SNMPv1 error codes when processing an SNMPv1 message.

   Note that SNMPv1 error codes SHOULD NOT be used without any change
   when processing SNMPv2c or SNMPv3 messages, except in the case of
   proxy forwarding.  Also, SNMPv1 access to MIB data SHOULD NOT be used
   when processing SNMPv2c or SNMPv3 messages.  In the case of proxy
   forwarding, for backwards compatibility, SNMPv1 error codes may be
   used without any change in a forwarded SNMPv2c or SNMPv3 message.

   The following sections describe the behaviour of a command responder
   application which supports multiple SNMP message versions, and which
   uses SNMPv2 access to MIB data when processing an SNMPv1 message.

4.2.2.1.  Handling Counter64

   The SMIv2 [RFC2578] defines one new syntax that is incompatible with
   SMIv1.  This syntax is Counter64.  All other syntaxes defined by
   SMIv2 are compatible with SMIv1.

   The impact on multi-lingual command responders is that they MUST NOT
   ever return a variable binding containing a Counter64 value in a
   response to a request that was received using the SNMPv1 message
   version.

   Multi-lingual command responders SHALL take the approach that object
   instances whose type is Counter64 are implicitly excluded from view
   when processing an SNMPv1 message.  So:

   -  On receipt of an SNMPv1 GetRequest-PDU containing a variable
      binding whose name field points to an object instance of type
      Counter64, a GetResponsePDU SHALL be returned, with an error-


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      status of noSuchName and the error-index set to the variable
      binding that caused this error.

   -  On an SNMPv1 GetNextRequest-PDU, any object instance which
      contains a syntax of Counter64 SHALL be skipped, and the next
      accessible object instance that does not have the syntax of
      Counter64 SHALL be retrieved.  If no such object instance exists,
      then an error-status of noSuchName SHALL be returned, and the
      error-index SHALL be set to the variable binding that caused this
      error.

   -  Any SNMPv1 request which contains a variable binding with a
      Counter64 value is ill-formed, so the foregoing rules do not
      apply.  If that error is detected, a response SHALL NOT be
      returned, since it would contain a copy of the ill-formed variable
      binding.  Instead, the offending PDU SHALL be discarded and the
      counter snmpInASNParseErrs SHALL be incremented.

4.2.2.2.  Mapping SNMPv2 Exceptions

   SNMPv2 provides a feature called exceptions, which allow an SNMPv2
   Response PDU to return as much management information as possible,
   even when an error occurs.  However, SNMPv1 does not support
   exceptions, and so an SNMPv1 Response PDU cannot return any
   management information, and can only return an error-status and an
   error-index value.

   When an SNMPv1 request is received, a command responder MUST check
   any variable bindings returned using SNMPv2 access to MIB data for
   exception values, and convert these exception values into SNMPv1
   error codes.

   The type of exception that can be returned when accessing MIB data
   and the action taken depends on the type of SNMP request.

   -  For a GetRequest, a noSuchObject or noSuchInstance exception may
      be returned.

   -  For a GetNextRequest, an endOfMibView exception may be returned.

   -  No exceptions will be returned for a SetRequest, and a
      GetBulkRequest should only be received in an SNMPv2c or SNMPv3
      message, so these request types may be ignored when mapping
      exceptions.

   Note that when a response contains multiple exceptions, it is an
   implementation choice as to which variable binding the error-index
   should reference.


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4.2.2.2.1.  Mapping noSuchObject and noSuchInstance

   A noSuchObject or noSuchInstance exception generated by an SNMPv2
   access to MIB data indicates that the requested object instance can
   not be returned.  The SNMPv1 error code for this condition is
   noSuchName, and so the error-status field of the response PDU SHALL
   be set to noSuchName.  Also, the error-index field SHALL be set to
   the index of the variable binding for which an exception occurred (if
   there is more than one then it is an implementation decision as to
   which is used), and the variable binding list from the original
   request SHALL be returned with the response PDU.

4.2.2.2.2.  Mapping endOfMibView

   When an SNMPv2 access to MIB data returns a variable binding
   containing an endOfMibView exception, it indicates that there are no
   object instances available which lexicographically follow the object
   in the request.  In an SNMPv1 agent, this condition normally results
   in a noSuchName error, and so the error-status field of the response
   PDU SHALL be set to noSuchName.  Also, the error-index field SHALL be
   set to the index of the variable binding for which an exception
   occurred (if there is more than one then it is an implementation
   decision as to which is used), and the variable binding list from the
   original request SHALL be returned with the response PDU.

4.2.2.3.  Processing An SNMPv1 GetRequest

   When processing an SNMPv1 GetRequest, the following procedures MUST
   be followed when using an SNMPv2 access to MIB data.

   When such an access to MIB data returns response data using SNMPv2
   syntax and error-status values, then:

   (1)  If the error-status is anything other than noError,

        -   The error status SHALL be translated to an SNMPv1 error-
            status using the table in section 4.4, "Error Status
            Mappings".

        -   The error-index SHALL be set to the position (in the
            original request) of the variable binding that caused the
            error-status.

        -   The variable binding list of the response PDU SHALL be made
            exactly the same as the variable binding list that was
            received in the original request.


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   (2)  If the error-status is noError, the variable bindings SHALL be
        checked for any SNMPv2 exception (noSuchObject or
        noSuchInstance) or an SNMPv2 syntax that is unknown to SNMPv1
        (Counter64).  If there are any such variable bindings, one of
        those variable bindings SHALL be selected (it is an
        implementation choice as to which is selected), and:

        -   The error-status SHALL be set to noSuchName,

        -   The error-index SHALL be set to the position (in the
            variable binding list of the original request) of the
            selected variable binding, and

        -   The variable binding list of the response PDU SHALL be
            exactly the same as the variable binding list that was
            received in the original request.

   (3)  If there are no such variable bindings, then:

        -   The error-status SHALL be set to noError,

        -   The error-index SHALL be set to zero, and

        -   The variable binding list of the response SHALL be composed
            from the data as it is returned by the access to MIB data.

4.2.2.4.  Processing An SNMPv1 GetNextRequest

   When processing an SNMPv1 GetNextRequest, the following procedures
   MUST be followed when SNMPv2 access to MIB data is used as part of
   processing the request.  There may be repetitive accesses to MIB data
   to try to find the first object which lexicographically follows each
   of the objects in the request.  This is implementation specific.
   These procedures are followed only for data returned when using
   SNMPv2 access to MIB data.  Data returned using SNMPv1 access to MIB
   data may be treated in the normal manner for an SNMPv1 request.

   First, if the access to MIB data returns an error-status of anything
   other than noError:

   (1)  The error status SHALL be translated to an SNMPv1 error-status
        using the table in section 4.4, "Error Status Mappings".

   (2)  The error-index SHALL be set to the position (in the original
        request) of the variable binding that caused the error-status.


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   (3)  The variable binding list of the response PDU SHALL be exactly
        the same as the variable binding list that was received in the
        original request.

   Otherwise, if the access to MIB data returns an error-status of
   noError:

   (1)  Any variable bindings containing an SNMPv2 syntax of Counter64
        SHALL be considered to be not in view, and MIB data SHALL be
        accessed as many times as is required until either a value other
        than Counter64 is returned, or an error or endOfMibView
        exception occurs.

   (2)  If there is any variable binding that contains an SNMPv2
        exception endOfMibView (if there is more than one then it is an
        implementation decision as to which is chosen):

        -   The error-status SHALL be set to noSuchName,

        -   The error-index SHALL be set to the position (in the
            variable binding list of the original request) of the
            variable binding that returned such an SNMPv2 exception, and

        -   The variable binding list of the response PDU SHALL be
            exactly the same as the variable binding list that was
            received in the original request.

   (3)  If there are no such variable bindings, then:

        -   The error-status SHALL be set to noError,

        -   The error-index SHALL be set to zero, and

        -   The variable binding list of the response SHALL be composed
            from the data as it is returned by the access to MIB data.

4.2.2.5.  Processing An SNMPv1 SetRequest

   When processing an SNMPv1 SetRequest, the following procedures MUST
   be followed when using SNMPv2 access to MIB data.

   When such MIB access returns response data using SNMPv2 syntax and
   error-status values, and the error-status is anything other than
   noError, then:

   -  The error status SHALL be translated to an SNMPv1 error-status
      using the table in section 4.4, "Error Status Mappings".


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   -  The error-index SHALL be set to the position (in the original
      request) of the variable binding that caused the error-status.

   -  The variable binding list of the response PDU SHALL be made
      exactly the same as the variable binding list that was received in
      the original request.

4.2.3.  Notification Originator

   A notification originator must be able to translate between SNMPv1
   notification parameters and SNMPv2 notification parameters in order
   to send a notification using a particular SNMP message version.  If a
   notification is generated using SNMPv1 notification parameters, and
   configuration information specifies that notifications be sent using
   SNMPv2c or SNMPv3, the notification parameters must be translated to
   SNMPv2 notification parameters.  Likewise, if a notification is
   generated using SNMPv2 notification parameters, and configuration
   information specifies that notifications be sent using SNMPv1, the
   notification parameters must be translated to SNMPv1 notification
   parameters.  In this case, if the notification cannot be translated
   (due to the presence of a Counter64 type), it will not be sent using
   SNMPv1.

   When a notification originator generates a notification, using
   parameters obtained from the SNMP-TARGET-MIB and SNMP-NOTIFICATION-
   MIB, if the SNMP version used to generate the notification is SNMPv1,
   the PDU type used will always be a TrapPDU, regardless of whether the
   value of snmpNotifyType is trap(1) or inform(2).

   Note also that access control and notification filtering are
   performed in the usual manner for notifications, regardless of the
   SNMP message version to be used when sending a notification.  The
   parameters for performing access control are found in the usual
   manner (i.e., from inspecting the SNMP-TARGET-MIB and SNMP-
   NOTIFICATION-MIB).  In particular, when generating an SNMPv1 Trap, in
   order to perform the access check specified in [RFC3413], section
   3.3, bullet (3), the notification originator may need to generate a
   value for snmpTrapOID.0 as described in section 3.1, bullets (2) and
   (3) of this document.  If the SNMPv1 notification parameters being
   used were previously translated from a set of SNMPv2 notification
   parameters, this value may already be known, in which case it need
   not be generated.

4.2.4.  Notification Receiver

   There are no special requirements of a notification receiver.
   However, an implementation may find it useful to allow a higher level
   application to request whether notifications should be delivered to a


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   higher level application using SNMPv1 notification parameter or
   SNMPv2 notification parameters.  The notification receiver would then
   translate notification parameters when required in order to present a
   notification using the desired set of parameters.

4.3.  Proxy Implementations

   A proxy implementation may be used to enable communication between
   entities which support different SNMP message versions.  This is
   accomplished in a proxy forwarder application by performing
   translations on PDUs.  These translations depend on the PDU type, the
   SNMP version of the packet containing a received PDU, and the SNMP
   version to be used to forward a received PDU.  The following sections
   describe these translations.  In all cases other than those described
   below, the proxy SHALL forward a received PDU without change, subject
   to size constraints as defined in section 5.3 (Community MIB) of this
   document.  Note that in the following sections, the 'Upstream
   Version' refers to the version used between the command generator or
   notification receiver and the proxy, and the 'Downstream Version'
   refers to the version used between the proxy and the command
   responder or notification originator, regardless of the PDU type or
   direction.

4.3.1.  Upstream Version Greater Than Downstream Version

   -  If a GetBulkRequest-PDU is received and must be forwarded using
      the SNMPv1 message version, the proxy forwarder SHALL act as if
      the non-repeaters and max-repetitions fields were both set to 0,
      and SHALL set the tag of the PDU to GetNextRequest-PDU.

   -  If a GetResponse-PDU is received whose error-status field has a
      value of 'tooBig', and the message will be forwarded using the
      SNMPv2c or SNMPv3 message version, and the original request
      received by the proxy was not a GetBulkRequest-PDU, the proxy
      forwarder SHALL remove the contents of the variable-bindings field
      and ensure that the error-index field is set to 0 before
      forwarding the response.

   -  If a GetResponse-PDU is received whose error-status field has a
      value of 'tooBig', and the message will be forwarded using the
      SNMPv2c or SNMPv3 message version, and the original request
      received by the proxy was a GetBulkRequest-PDU, the proxy
      forwarder SHALL re-send the forwarded request (which would have
      been altered to be a GetNextRequest-PDU) with all but the first
      variable-binding removed.  The proxy forwarder SHALL only re-send
      such a request a single time.  If the resulting GetResponse-PDU
      also contains an error-status field with a value of 'tooBig', then
      the proxy forwarder SHALL remove the contents of the variable-


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      bindings field, and change the error-status field to 'noError',
      and ensure that the error-index field is set to 0 before
      forwarding the response.  Note that if the original request only
      contained a single variable-binding, the proxy may skip re-sending
      the request and simply remove the variable-bindings and change the
      error-status to 'noError'.  Further note that, while it might have
      been possible to fit more variable bindings if the proxy only re-
      sent the request multiple times, and stripped only a single
      variable binding from the request at a time, this is deemed too
      expensive.  The approach described here preserves the behaviour of
      a GetBulkRequest as closely as possible, without incurring the
      cost of re-sending the request multiple times.

   -  If a Trap-PDU is received, and will be forwarded using the SNMPv2c
      or SNMPv3 message version, the proxy SHALL apply the translation
      rules described in section 3, and SHALL forward the notification
      as an SNMPv2-Trap-PDU.

      Note that when an SNMPv1 agent generates a message containing a
      Trap-PDU which is subsequently forwarded by one or more proxy
      forwarders using SNMP versions other than SNMPv1, the community
      string and agent-addr fields from the original message generated
      by the SNMPv1 agent will be preserved through the use of the
      snmpTrapAddress and snmpTrapCommunity objects.

4.3.2.  Upstream Version Less Than Downstream Version

   -  If a GetResponse-PDU is received in response to a GetRequest-PDU
      (previously generated by the proxy) which contains variable-
      bindings of type Counter64 or which contain an SNMPv2 exception
      code, and the message would be forwarded using the SNMPv1 message
      version, the proxy MUST generate an alternate response PDU
      consisting of the request-id and variable bindings from the
      original SNMPv1 request, containing a noSuchName error-status
      value, and containing an error-index value indicating the position
      of the variable-binding containing the Counter64 type or exception
      code.

   -  If a GetResponse-PDU is received in response to a GetNextRequest-
      PDU (previously generated by the proxy) which contains variable-
      bindings that contain an SNMPv2 exception code, and the message
      would be forwarded using the SNMPv1 message version, the proxy
      MUST generate an alternate response PDU consisting of the
      request-id and variable bindings from the original SNMPv1 request,
      containing a noSuchName error-status value, and containing an
      error-index value indicating the position of the variable-binding
      containing the exception code.


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   -  If a GetResponse-PDU is received in response to a GetNextRequest-
      PDU (previously generated by the proxy) which contains variable-
      bindings of type Counter64, the proxy MUST re-send the entire
      GetNextRequest-PDU, with the following modifications.  For any
      variable bindings in the received GetResponse which contained
      Counter64 types, the proxy substitutes the object names of these
      variable bindings for the corresponding object names in the
      previously-sent GetNextRequest.  The proxy MUST repeat this
      process until no Counter64 objects are returned.  Note that an
      implementation may attempt to optimize this process of skipping
      Counter64 objects.  One approach to such an optimization would be
      to replace the last sub-identifier of the object names of varbinds
      containing a Counter64 type with 65535 if that sub-identifier is
      less than 65535, or with 4294967295 if that sub-identifier is
      greater than 65535.  This approach should skip multiple instances
      of the same Counter64 object, while maintaining compatibility with
      some broken agent implementations (which only use 16-bit integers
      for sub-identifiers).

      Deployment Hint:  The process of repeated GetNext requests used by
      a proxy when Counter64 types are returned can be expensive.  When
      deploying a proxy, this can be avoided by configuring the target
      agents to which the proxy forwards requests in a manner such that
      any objects of type Counter64 are in fact not-in-view for the
      principal that the proxy is using when communicating with these
      agents.  However, when using such a configuration, one should be
      careful to use a different principal for communicating with the
      target agent when an incoming SNMPv2c or SNMPv3 request is
      received, to ensure that objects of type Counter64 are properly
      returned.

   -  If a GetResponse-PDU is received which contains an SNMPv2 error-
      status value of wrongValue, wrongEncoding, wrongType, wrongLength,
      inconsistentValue, noAccess, notWritable, noCreation,
      inconsistentName, resourceUnavailable, commitFailed, undoFailed,
      or authorizationError, and the message would be forwarded using
      the SNMPv1 message version, the error-status value is modified
      using the mappings in section 4.4.

   -  If an SNMPv2-Trap-PDU is received, and will be forwarded using the
      SNMPv1 message version, the proxy SHALL apply the translation
      rules described in section 3, and SHALL forward the notification
      as a Trap-PDU.  Note that if the translation fails due to the
      existence of a Counter64 data-type in the received SNMPv2-Trap-
      PDU, the trap cannot be forwarded using SNMPv1.


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   -  If an InformRequest-PDU is received, any configuration information
      indicating that it would be forwarded using the SNMPv1 message
      version SHALL be ignored.  An InformRequest-PDU can only be
      forwarded using the SNMPv2c or SNMPv3 message version.  The
      InformRequest-PDU may still be forwarded if there is other
      configuration information indicating that it should be forwarded
      using SNMPv2c or SNMPv3.

4.4.  Error Status Mappings

   The following tables shows the mappings of SNMPv1 error-status values
   into SNMPv2 error-status values, and the mappings of SNMPv2 error-
   status values into SNMPv1 error-status values.

      SNMPv1 error-status    SNMPv2 error-status
      ===================    ===================
      noError                noError
      tooBig                 tooBig
      noSuchName             noSuchName
      badValue               badValue
      genErr                 genErr


      SNMPv2 error-status    SNMPv1 error-status
      ===================    ===================
      noError                noError
      tooBig                 tooBig
      genErr                 genErr
      wrongValue             badValue
      wrongEncoding          badValue
      wrongType              badValue
      wrongLength            badValue
      inconsistentValue      badValue
      noAccess               noSuchName
      notWritable            noSuchName
      noCreation             noSuchName
      inconsistentName       noSuchName
      resourceUnavailable    genErr
      commitFailed           genErr
      undoFailed             genErr
      authorizationError     noSuchName

   Whenever the SNMPv2 error-status value of authorizationError is
   translated to an SNMPv1 error-status value of noSuchName, the value
   of snmpInBadCommunityUses MUST be incremented.


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5.  Message Processing Models and Security Models

   In order to adapt SNMPv1 (and SNMPv2c) into the SNMP architecture,
   the following Message Processing (MP) models are defined in this
   document:

   -  The SNMPv1 Message Processing Model

   -  The SNMPv1 Community-Based Security Model

   -  The SNMPv2c Message Processing Model

   -  The SNMPv2c Community-Based Security Model

   In most respects, the SNMPv1 Message Processing Model and the SNMPv2c
   Message Processing Model are identical, and so these are not
   discussed independently in this document.  Differences between the
   two models are described as required.

   Similarly, the SNMPv1 Community-Based Security Model and the SNMPv2c
   Community-Based Security Model are nearly identical, and so are not
   discussed independently.  Differences between these two models are
   also described as required.

5.1.  Mappings

   The SNMPv1 (and SNMPv2c) Message Processing Model and Security Model
   require mappings between parameters used in SNMPv1 (and SNMPv2c)
   messages, and the version independent parameters used in the SNMP
   architecture [RFC3411].  The parameters which MUST be mapped consist
   of the SNMPv1 (and SNMPv2c) community name, and the SNMP securityName
   and contextEngineID/contextName pair.  A MIB module (the SNMP-
   COMMUNITY-MIB) is provided in this document in order to perform these
   mappings.  This MIB provides mappings in both directions, that is, a
   community name may be mapped to a securityName, contextEngineID, and
   contextName, or the combination of securityName, contextEngineID, and
   contextName may be mapped to a community name.

5.2.  The SNMPv1 MP Model and SNMPv1 Community-based Security Model

   The SNMPv1 Message Processing Model handles processing of SNMPv1
   messages.  The processing of messages is handled generally in the
   same manner as described in RFC 1157 [RFC1157], with differences and
   clarifications as described in the following sections.  The
   SnmpMessageProcessingModel value for SNMPv1 is 0 (the value for
   SNMPv2c is 1).


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5.2.1.  Processing An Incoming Request

   In RFC 1157 [RFC1157], section 4.1, item (3) for an entity which
   receives a message, states that various parameters are passed to the
   "desired authentication scheme".  The desired authentication scheme
   in this case is the SNMPv1 Community-Based Security Model, which will
   be called using the processIncomingMsg ASI.  The parameters passed to
   this ASI are:

   -  The messageProcessingModel, which will be 0 (or 1 for SNMPv2c).

   -  The maxMessageSize, which should be the maximum size of a message
      that the receiving entity can generate (since there is no such
      value in the received message).

   -  The securityParameters, which consist of the community string and
      the message's source and destination transport domains and
      addresses.

   -  The securityModel, which will be 1 (or 2 for SNMPv2c).

   -  The securityLevel, which will be noAuthNoPriv.

   -  The wholeMsg and wholeMsgLength.

   The Community-Based Security Model will attempt to select a row in
   the snmpCommunityTable.  This is done by performing a search through
   the snmpCommunityTable in lexicographic order.  The first entry for
   which the following matching criteria are satisfied will be selected:

   -  The community string is equal to the snmpCommunityName value.

   -  If the snmpCommunityTransportTag is an empty string, it is ignored
      for the purpose of matching.  If the snmpCommunityTransportTag is
      not an empty string, the transportDomain and transportAddress from
      which the message was received must match one of the entries in
      the snmpTargetAddrTable selected by the snmpCommunityTransportTag
      value.  The snmpTargetAddrTMask object is used as described in
      section 5.3 when checking whether the transportDomain and
      transportAddress matches a entry in the snmpTargetAddrTable.

   If no such entry can be found, an authentication failure occurs as
   described in RFC 1157 [RFC1157], and the snmpInBadCommunityNames
   counter is incremented.


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   The parameters returned from the Community-Based Security Model are:

   -  The securityEngineID, which will always be the local value of
      snmpEngineID.0.

   -  The securityName, which will be the value of
      snmpCommunitySecurityName from the selected row in the
      snmpCommunityTable.

   -  The scopedPDU.  Note that this parameter will actually consist of
      three values, the contextSnmpEngineID (which will be the value of
      snmpCommunityContextEngineID from the selected entry in the
      snmpCommunityTable), the contextName (which will be the value of
      snmpCommunityContextName from the selected entry in the
      snmpCommunityTable), and the PDU.  These must be separate values,
      since the first two do not actually appear in the message.

   -  The maxSizeResponseScopedPDU, which will be derived using the
      minimum of the maxMessageSize above, and the value of
      snmpTargetAddrMMS of the selected row in the snmpTargetAddrTable.
      If no such entry was selected, then this value will be derived
      from the maxMessageSize only.

   -  The securityStateReference, which MUST contain the community
      string from the original request.

   The appropriate SNMP application will then be called (depending on
   the value of the contextEngineID and the request type in the PDU)
   using the processPdu ASI.  The parameters passed to this ASI are:

   -  The messageProcessingModel, which will be 0 (or 1 for SNMPv2c).

   -  The securityModel, which will be 1 (or 2 for SNMPv2c).

   -  The securityName, which was returned from the call to
      processIncomingMsg.

   -  The securityLevel, which is noAuthNoPriv.

   -  The contextEngineID, which was returned as part of the ScopedPDU
      from the call to processIncomingMsg.

   -  The contextName, which was returned as part of the ScopedPDU from
      the call to processIncomingMsg.

   -  The pduVersion, which should indicate an SNMPv1 version PDU (if
      the message version was SNMPv2c, this would be an SNMPv2 version
      PDU).


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   -  The PDU, which was returned as part of the ScopedPDU from the call
      to processIncomingMsg.

   -  The maxSizeResponseScopedPDU which was returned from the call to
      processIncomingMsg.

   -  The stateReference which was returned from the call to
      processIncomingMsg.

   The SNMP application should process the request as described
   previously in this document.  Note that access control is applied by
   an SNMPv3 command responder application as usual.  The parameters as
   passed to the processPdu ASI will be used in calls to the
   isAccessAllowed ASI.

5.2.2.  Generating An Outgoing Response

   There is no special processing required for generating an outgoing
   response.  However, the community string used in an outgoing response
   must be the same as the community string from the original request.
   The original community string MUST be present in the
   securityStateReference information of the original request.

5.2.3.  Generating An Outgoing Notification

   In a multi-lingual SNMP entity, the parameters used for generating
   notifications will be obtained by examining the SNMP-TARGET-MIB and
   SNMP-NOTIFICATION-MIB.  These parameters will be passed to the SNMPv1
   Message Processing Model using the sendPdu ASI.  The SNMPv1 Message
   Processing Model will attempt to locate an appropriate community
   string in the snmpCommunityTable based on the parameters passed to
   the sendPdu ASI.  This is done by performing a search through the
   snmpCommunityTable in lexicographic order.  The first entry for which
   the following matching criteria are satisfied will be selected:

   -  The securityName must be equal to the snmpCommunitySecurityName
      value.

   -  The contextEngineID must be equal to the
      snmpCommunityContextEngineID value.

   -  The contextName must be equal to the snmpCommunityContextName
      value.


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   -  If the snmpCommunityTransportTag is an empty string, it is ignored
      for the purpose of matching.  If the snmpCommunityTransportTag is
      not an empty string, the transportDomain and transportAddress must
      match one of the entries in the snmpTargetAddrTable selected by
      the snmpCommunityTransportTag value.

   If no such entry can be found, the notification is not sent.
   Otherwise, the community string used in the outgoing notification
   will be the value of the snmpCommunityName column of the selected
   row.

5.2.4.  Proxy Forwarding Of Requests

   In a proxy forwarding application, when a received request is to be
   forwarded using the SNMPv1 Message Processing Model, the parameters
   used for forwarding will be obtained by examining the SNMP-PROXY-MIB
   and the SNMP-TARGET-MIB.  These parameters will be passed to the
   SNMPv1 Message Processing Model using the sendPdu ASI.  The SNMPv1
   Message Processing Model will attempt to locate an appropriate
   community string in the snmpCommunityTable based on the parameters
   passed to the sendPdu ASI.  This is done by performing a search
   through the snmpCommunityTable in lexicographic order.  The first
   entry for which the following matching criteria are satisfied will be
   selected:

   -  The securityName must be equal to the snmpCommunitySecurityName
      value.

   -  The contextEngineID must be equal to the
      snmpCommunityContextEngineID value.

   -  The contextName must be equal to the snmpCommunityContextName
      value.

   If no such entry can be found, the proxy forwarding application
   should follow the procedure described in RFC 3413 [RFC3413], section
   3.5.1.1, item (2).  This procedure states that the snmpProxyDrops
   counter [RFC3418] is incremented, and that a Response-PDU is
   generated by calling the Dispatcher using the returnResponsePdu
   abstract service interface.

5.3.  The SNMP Community MIB Module

   The SNMP-COMMUNITY-MIB contains objects for mapping between community
   strings and version-independent SNMP message parameters.  In
   addition, this MIB provides a mechanism for performing source address
   validation on incoming requests, and for selecting community strings
   based on target addresses for outgoing notifications.  These two


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   features are accomplished by providing a tag in the
   snmpCommunityTable which selects sets of entries in the
   snmpTargetAddrTable [RFC3413].  In addition, the SNMP-COMMUNITY-MIB
   augments the snmpTargetAddrTable with a transport address mask value
   and a maximum message size value.  These values are used only where
   explicitly stated.  In cases where the snmpTargetAddrTable is used
   without mention of these augmenting values, the augmenting values
   should be ignored.

   The mask value, snmpTargetAddrTMask, allows selected entries in the
   snmpTargetAddrTable to specify multiple addresses (rather than just a
   single address per entry).  This would typically be used to specify a
   subnet in an snmpTargetAddrTable rather than just a single address.
   The mask value is used to select which bits of a transport address
   must match bits of the corresponding instance of
   snmpTargetAddrTAddress, in order for the transport address to match a
   particular entry in the snmpTargetAddrTable.  The value of an
   instance of snmpTargetAddrTMask must always be an OCTET STRING whose
   length is either zero or the same as that of the corresponding
   instance of snmpTargetAddrTAddress.

   Note that the snmpTargetAddrTMask object is only used where
   explicitly stated.  In particular, it is not used when generating
   notifications (i.e., when generating notifications, entries in the
   snmpTargetAddrTable only specify individual addresses).  If use of
   the snmpTargetAddrTMask object is not mentioned in text describing
   matching addresses in the snmpTargetAddrTable, then its value MUST be
   ignored.

   When checking whether a transport address matches an entry in the
   snmpTargetAddrTable, if the value of snmpTargetAddrTMask is a zero-
   length OCTET STRING, the mask value is ignored, and the value of
   snmpTargetAddrTAddress must exactly match a transport address.
   Otherwise, each bit of each octet in the snmpTargetAddrTMask value
   corresponds to the same bit of the same octet in the
   snmpTargetAddrTAddress value.  For bits that are set in the
   snmpTargetAddrTMask value (i.e., bits equal to 1), the corresponding
   bits in the snmpTargetAddrTAddress value must match the bits in a
   transport address.  If all such bits match, the transport address is
   matched by that snmpTargetAddrTable entry.  Otherwise, the transport
   address is not matched.

   The maximum message size value, snmpTargetAddrMMS, is used to
   determine the maximum message size acceptable to another SNMP entity
   when the value cannot be determined from the protocol.


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      SNMP-COMMUNITY-MIB DEFINITIONS ::= BEGIN

      IMPORTS
          IpAddress,
          MODULE-IDENTITY,
          OBJECT-TYPE,
          Integer32,
          snmpModules
              FROM SNMPv2-SMI
          RowStatus,
          StorageType
              FROM SNMPv2-TC
          SnmpAdminString,
          SnmpEngineID
              FROM SNMP-FRAMEWORK-MIB
          SnmpTagValue,
          snmpTargetAddrEntry
              FROM SNMP-TARGET-MIB
          MODULE-COMPLIANCE,
          OBJECT-GROUP
              FROM SNMPv2-CONF;

      snmpCommunityMIB MODULE-IDENTITY
          LAST-UPDATED "200308060000Z"        -- 06 Aug 2003, midnight
    ORGANIZATION "SNMPv3 Working Group"
    CONTACT-INFO "WG-email:   snmpv3@lists.tislabs.com
                  Subscribe:  majordomo@lists.tislabs.com
                              In msg body:  subscribe snmpv3

                  Co-Chair:   Russ Mundy
                              SPARTA, Inc
                  Postal:     7075 Samuel Morse Drive
                              Columbia, MD 21045
                              USA
                  EMail:      mundy@tislabs.com
                  Phone:      +1 410-872-1515

                  Co-Chair:   David Harrington
                              Enterasys Networks
                  Postal:     35 Industrial Way
                              P. O. Box 5005
                              Rochester, New Hampshire 03866-5005
                              USA
                  EMail:      dbh@enterasys.com
                  Phone:      +1 603-337-2614

                  Co-editor:  Rob Frye
                              Vibrant Solutions


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                  Postal:     2711 Prosperity Ave
                              Fairfax, Virginia 22031
                              USA
                  E-mail:     rfrye@vibrant-1.com
                  Phone:      +1-703-270-2000

                  Co-editor:  David B. Levi
                              Nortel Networks
                  Postal:     3505 Kesterwood Drive
                              Knoxville, Tennessee 37918
                  E-mail:     dlevi@nortelnetworks.com
                  Phone:      +1 865 686 0432

                  Co-editor:  Shawn A. Routhier
                              Wind River Systems, Inc.
                  Postal:     500 Wind River Way
                              Alameda, CA 94501
                  E-mail:     sar@epilogue.com
                  Phone:      +1 510 749 2095

                  Co-editor:  Bert Wijnen
                              Lucent Technologies
                  Postal:     Schagen 33
                              3461 GL Linschoten
                              Netherlands
                  Email:      bwijnen@lucent.com
                  Phone:      +31-348-407-775
                 "

        DESCRIPTION
            "This MIB module defines objects to help support
             coexistence between SNMPv1, SNMPv2c, and SNMPv3.

             Copyright (C) The Internet Society (2003) This
             version of this MIB module is part of RFC 3584;
             see the RFC itself for full legal notices."

        REVISION "200308060000Z" -- 06 Aug 2003
        DESCRIPTION
            "Updated the LAST-UPDATED, CONTACT-INFO, and REVISION
             clauses and added a copyright notice to the
             DESCRIPTION clause of the MIB module's
             MODULE-IDENTITY invocation.

             Updated the description of snmpCommunityTransportTag
             to make it consistent with the rest of the document.

             Updated the description of `snmpTargetAddrMMS' to


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             clarify that a value of 0 means that the maximum
             message size is unknown.

             Changed the name of 'snmpCommunityGroup' to
             snmpCommunityTableGroup to avoid a name conflict
             with the SNMPv2-MIB.

             Updated DESCRIPTION of snmpCommunityName.

             Updated DESCRIPTION of snmpTrapCommunity.

             Added snmpCommunityMIBFullCompliance.

             This version published as RFC 3584."

        REVISION "200003060000Z" -- 6 Mar 2000
        DESCRIPTION "This version published as RFC 2576."

    ::= { snmpModules 18 }

-- Administrative assignments ************************************

snmpCommunityMIBObjects
        OBJECT IDENTIFIER ::= { snmpCommunityMIB 1 }

snmpCommunityMIBConformance
        OBJECT IDENTIFIER ::= { snmpCommunityMIB 2 }

--
-- The snmpCommunityTable contains a database of community
-- strings.  This table provides mappings between community
-- strings, and the parameters required for View-based Access
-- Control.
--

snmpCommunityTable OBJECT-TYPE
    SYNTAX       SEQUENCE OF SnmpCommunityEntry
    MAX-ACCESS   not-accessible
    STATUS       current
    DESCRIPTION
        "The table of community strings configured in the SNMP
         engine's Local Configuration Datastore (LCD)."
    ::= { snmpCommunityMIBObjects 1 }

snmpCommunityEntry OBJECT-TYPE
    SYNTAX       SnmpCommunityEntry
    MAX-ACCESS   not-accessible
    STATUS       current


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    DESCRIPTION
        "Information about a particular community string."
    INDEX       { IMPLIED snmpCommunityIndex }
    ::= { snmpCommunityTable 1 }

SnmpCommunityEntry ::= SEQUENCE {
    snmpCommunityIndex               SnmpAdminString,
    snmpCommunityName                OCTET STRING,
    snmpCommunitySecurityName        SnmpAdminString,
    snmpCommunityContextEngineID     SnmpEngineID,
    snmpCommunityContextName         SnmpAdminString,
    snmpCommunityTransportTag        SnmpTagValue,
    snmpCommunityStorageType         StorageType,
    snmpCommunityStatus              RowStatus
}

snmpCommunityIndex OBJECT-TYPE
    SYNTAX      SnmpAdminString (SIZE(1..32))
    MAX-ACCESS  not-accessible
    STATUS      current
    DESCRIPTION
        "The unique index value of a row in this table."
    ::= { snmpCommunityEntry 1 }

snmpCommunityName OBJECT-TYPE
    SYNTAX       OCTET STRING
    MAX-ACCESS   read-create
    STATUS       current
    DESCRIPTION
        "The community string for which a row in this table
         represents a configuration.  There is no SIZE constraint
         specified for this object because RFC 1157 does not
         impose any explicit limitation on the length of community
         strings (their size is constrained indirectly by the
         SNMP message size)."
    ::= { snmpCommunityEntry 2 }

snmpCommunitySecurityName OBJECT-TYPE
    SYNTAX       SnmpAdminString (SIZE(1..32))
    MAX-ACCESS   read-create
    STATUS       current
    DESCRIPTION
        "A human readable string representing the corresponding
         value of snmpCommunityName in a Security Model
         independent format."
    ::= { snmpCommunityEntry 3 }

snmpCommunityContextEngineID OBJECT-TYPE


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    SYNTAX       SnmpEngineID
    MAX-ACCESS   read-create
    STATUS       current
    DESCRIPTION
        "The contextEngineID indicating the location of the
         context in which management information is accessed
         when using the community string specified by the
         corresponding instance of snmpCommunityName.

         The default value is the snmpEngineID of the entity in
         which this object is instantiated."
    ::= { snmpCommunityEntry 4 }

snmpCommunityContextName OBJECT-TYPE
    SYNTAX       SnmpAdminString (SIZE(0..32))
    MAX-ACCESS   read-create
    STATUS       current
    DESCRIPTION
        "The context in which management information is accessed
         when using the community string specified by the
         corresponding instance of snmpCommunityName."
    DEFVAL      { ''H }   -- the empty string
    ::= { snmpCommunityEntry 5 }

snmpCommunityTransportTag OBJECT-TYPE
    SYNTAX       SnmpTagValue
    MAX-ACCESS   read-create
    STATUS       current
    DESCRIPTION
        "This object specifies a set of transport endpoints
         which are used in two ways:
            - to specify the transport endpoints from which an
              SNMP entity will accept management requests, and
            - to specify the transport endpoints to which a
              notification may be sent using the community
              string matching the corresponding instance of
              snmpCommunityName.
         In either case, if the value of this object has
         zero-length, transport endpoints are not checked when
         either authenticating messages containing this community
         string, nor when generating notifications.

         The transports identified by this object are specified
         in the snmpTargetAddrTable.  Entries in that table
         whose snmpTargetAddrTagList contains this tag value
         are identified.

         If a management request containing a community string


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         that matches the corresponding instance of
         snmpCommunityName is received on a transport endpoint
         other than the transport endpoints identified by this
         object the request is deemed unauthentic.

         When a notification is to be sent using an entry in
         this table, if the destination transport endpoint of
         the notification does not match one of the transport
         endpoints selected by this object, the notification
         is not sent."
    DEFVAL      { ''H }   -- the empty string
    ::= { snmpCommunityEntry 6 }

snmpCommunityStorageType OBJECT-TYPE
    SYNTAX       StorageType
    MAX-ACCESS   read-create
    STATUS       current
    DESCRIPTION
        "The storage type for this conceptual row in the
         snmpCommunityTable.  Conceptual rows having the value
         'permanent' need not allow write-access to any
         columnar object in the row."
    ::= { snmpCommunityEntry 7 }

snmpCommunityStatus OBJECT-TYPE
    SYNTAX       RowStatus
    MAX-ACCESS   read-create
    STATUS       current
    DESCRIPTION
        "The status of this conceptual row in the
         snmpCommunityTable.

         An entry in this table is not qualified for activation
         until instances of all corresponding columns have been
         initialized, either through default values, or through
         Set operations.  The snmpCommunityName and
         snmpCommunitySecurityName objects must be explicitly set.

         There is no restriction on setting columns in this table
         when the value of snmpCommunityStatus is active(1)."
    ::= { snmpCommunityEntry 8 }

--
-- The snmpTargetAddrExtTable
--

snmpTargetAddrExtTable OBJECT-TYPE
    SYNTAX       SEQUENCE OF SnmpTargetAddrExtEntry


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    MAX-ACCESS   not-accessible
    STATUS       current
    DESCRIPTION
        "The table of mask and maximum message size (mms) values
         associated with the snmpTargetAddrTable.

         The snmpTargetAddrExtTable augments the
         snmpTargetAddrTable with a transport address mask value
         and a maximum message size value.  The transport address
         mask allows entries in the snmpTargetAddrTable to define
         a set of addresses instead of just a single address.
         The maximum message size value allows the maximum
         message size of another SNMP entity to be configured for
         use in SNMPv1 (and SNMPv2c) transactions, where the
         message format does not specify a maximum message size."
    ::= { snmpCommunityMIBObjects 2 }

snmpTargetAddrExtEntry OBJECT-TYPE
    SYNTAX       SnmpTargetAddrExtEntry
    MAX-ACCESS   not-accessible
    STATUS       current
    DESCRIPTION
        "Information about a particular mask and mms value."
    AUGMENTS       { snmpTargetAddrEntry }
    ::= { snmpTargetAddrExtTable 1 }

SnmpTargetAddrExtEntry ::= SEQUENCE {
    snmpTargetAddrTMask              OCTET STRING,
    snmpTargetAddrMMS                Integer32
}

snmpTargetAddrTMask OBJECT-TYPE
    SYNTAX      OCTET STRING (SIZE (0..255))
    MAX-ACCESS  read-create
    STATUS      current
    DESCRIPTION
        "The mask value associated with an entry in the
         snmpTargetAddrTable.  The value of this object must
         have the same length as the corresponding instance of
         snmpTargetAddrTAddress, or must have length 0.  An
         attempt to set it to any other value will result in
         an inconsistentValue error.

         The value of this object allows an entry in the
         snmpTargetAddrTable to specify multiple addresses.
         The mask value is used to select which bits of
         a transport address must match bits of the corresponding
         instance of snmpTargetAddrTAddress, in order for the


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         transport address to match a particular entry in the
         snmpTargetAddrTable.  Bits which are 1 in the mask
         value indicate bits in the transport address which
         must match bits in the snmpTargetAddrTAddress value.
         Bits which are 0 in the mask indicate bits in the
         transport address which need not match.  If the
         length of the mask is 0, the mask should be treated
         as if all its bits were 1 and its length were equal
         to the length of the corresponding value of
         snmpTargetAddrTable.

         This object may not be modified while the value of the
         corresponding instance of snmpTargetAddrRowStatus is
         active(1).  An attempt to set this object in this case
         will result in an inconsistentValue error."
    DEFVAL { ''H }
    ::= { snmpTargetAddrExtEntry 1 }

snmpTargetAddrMMS OBJECT-TYPE
    SYNTAX      Integer32 (0|484..2147483647)
    MAX-ACCESS  read-create
    STATUS      current
    DESCRIPTION
        "The maximum message size value associated with an entry
         in the snmpTargetAddrTable.  Note that a value of 0 means
         that the maximum message size is unknown."
    DEFVAL { 484 }
    ::= { snmpTargetAddrExtEntry 2 }

--
-- The snmpTrapAddress and snmpTrapCommunity objects are included
-- in notifications that are forwarded by a proxy, which were
-- originally received as SNMPv1 Trap messages.
--

snmpTrapAddress OBJECT-TYPE
    SYNTAX      IpAddress
    MAX-ACCESS  accessible-for-notify
    STATUS      current
    DESCRIPTION
        "The value of the agent-addr field of a Trap PDU which
         is forwarded by a proxy forwarder application using
         an SNMP version other than SNMPv1.  The value of this
         object SHOULD contain the value of the agent-addr field
         from the original Trap PDU as generated by an SNMPv1
         agent."
    ::= { snmpCommunityMIBObjects 3 }


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snmpTrapCommunity OBJECT-TYPE
    SYNTAX      OCTET STRING
    MAX-ACCESS  accessible-for-notify
    STATUS      current
    DESCRIPTION
        "The value of the community string field of an SNMPv1
         message containing a Trap PDU which is forwarded by a
         a proxy forwarder application using an SNMP version
         other than SNMPv1.  The value of this object SHOULD
         contain the value of the community string field from
         the original SNMPv1 message containing a Trap PDU as
         generated by an SNMPv1 agent.  There is no SIZE
         constraint specified for this object because RFC 1157
         does not impose any explicit limitation on the length
         of community strings (their size is constrained
         indirectly by the SNMP message size)."
    ::= { snmpCommunityMIBObjects 4 }

-- Conformance Information **************************************

snmpCommunityMIBCompliances OBJECT IDENTIFIER
                            ::= { snmpCommunityMIBConformance 1 }
snmpCommunityMIBGroups      OBJECT IDENTIFIER
                            ::= { snmpCommunityMIBConformance 2 }

-- Compliance statements

snmpCommunityMIBCompliance MODULE-COMPLIANCE
    STATUS       current
    DESCRIPTION
        "The compliance statement for SNMP engines which
         implement the SNMP-COMMUNITY-MIB."

    MODULE       -- this module
        MANDATORY-GROUPS { snmpCommunityTableGroup }

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

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

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


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

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

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

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

    ::= { snmpCommunityMIBCompliances 1 }

snmpProxyTrapForwardCompliance MODULE-COMPLIANCE
    STATUS       current
    DESCRIPTION
        "The compliance statement for SNMP engines which
         contain a proxy forwarding application which is
         capable of forwarding SNMPv1 traps using SNMPv2c
         or SNMPv3."
    MODULE       -- this module
        MANDATORY-GROUPS { snmpProxyTrapForwardGroup }
    ::= { snmpCommunityMIBCompliances 2 }

snmpCommunityMIBFullCompliance MODULE-COMPLIANCE
    STATUS       current
    DESCRIPTION
        "The compliance statement for SNMP engines which
         implement the SNMP-COMMUNITY-MIB with full read-create
         access."

    MODULE       -- this module
        MANDATORY-GROUPS { snmpCommunityTableGroup }
    ::= { snmpCommunityMIBCompliances 3 }

snmpCommunityTableGroup OBJECT-GROUP
    OBJECTS {
        snmpCommunityName,
        snmpCommunitySecurityName,
        snmpCommunityContextEngineID,
        snmpCommunityContextName,
        snmpCommunityTransportTag,
        snmpCommunityStorageType,


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        snmpCommunityStatus,
        snmpTargetAddrTMask,
        snmpTargetAddrMMS
    }
    STATUS       current
    DESCRIPTION
        "A collection of objects providing for configuration
         of community strings for SNMPv1 (and SNMPv2c) usage."
    ::= { snmpCommunityMIBGroups 1 }

snmpProxyTrapForwardGroup OBJECT-GROUP
    OBJECTS {
        snmpTrapAddress,
        snmpTrapCommunity
    }
    STATUS       current
    DESCRIPTION
        "Objects which are used by proxy forwarding applications
         when translating traps between SNMP versions.  These are
         used to preserve SNMPv1-specific information when
         translating to SNMPv2c or SNMPv3."
    ::= { snmpCommunityMIBGroups 3 }

END

6.  Intellectual Property Statement

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

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


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7.  Acknowledgments

   This document is the result of the efforts of the SNMPv3 Working
   Group.  The design of the SNMP-COMMUNITY-MIB incorporates work done
   by the authors of SNMPv2*:

      Jeff Case (SNMP Research, Inc.)
      David Harrington (Enterasys Networks)
      David Levi (Nortel Networks)
      Brian O'Keefe (Hewlett Packard)
      Jon Saperia (IronBridge Networks, Inc.)
      Steve Waldbusser (International Network Services)

8.  Security Considerations

   Although SNMPv1 and SNMPv2 do not provide any security, allowing
   community names to be mapped into securityName/contextName provides
   the ability to use view-based access control to limit the access of
   unsecured SNMPv1 and SNMPv2 operations.  In fact, it is important for
   network administrators to make use of this capability in order to
   avoid unauthorized access to MIB data that would otherwise be secure.

   When a proxy implementation translates messages between SNMPv1 (or
   SNMPv2c) and SNMPv3, there may be a loss of security.  For example,
   an SNMPv3 message received using authentication and privacy which is
   subsequently forwarded using SNMPv1 will lose the security benefits
   of using authentication and privacy (also known as confidentiality).
   Careful configuration of proxies is required to address such
   situations.  One approach to deal with such situations might be to
   use an encrypted tunnel.

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

   -  The snmpCommunityTable allows creation and deletion of community
      strings, which is potentially a serious security hole.  Access to
      this table should be greatly restricted, preferably by only
      allowing write access using SNMPv3 VACM and USM, with
      authentication and privacy.

   -  The snmpTargetAddrExtTable contains write-able objects which may
      also be considered sensitive, and so access to it should be
      restricted as well.


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   Some of the readable objects in this MIB module (i.e., objects with a
   MAX-ACCESS other than not-accessible) may be considered sensitive or
   vulnerable in some network environments.  It is thus important to
   control even GET and/or NOTIFY access to these objects and possibly
   to even encrypt the values of these objects when sending them over
   the network via SNMP.  These are the tables and objects and their
   sensitivity/vulnerability:

   -  The snmpCommunityTable has the potential to expose community
      strings which provide access to more information than that which
      is available using the usual 'public' community string.  For this
      reason, a security administrator may wish to limit accessibility
      to objects in the snmpCommunityTable, and in particular, to make
      it inaccessible when using the 'public' community string.

   SNMP versions prior to SNMPv3 did not include adequate security.
   Even if the network itself is secure (for example by using IPSec),
   even then, there is no control as to who on the secure network is
   allowed to access and GET/SET (read/change/create/delete) the objects
   in this MIB module.

   It is RECOMMENDED that implementers consider the security features as
   provided by the SNMPv3 framework (see [RFC3410], section 8),
   including full support for the SNMPv3 cryptographic mechanisms (for
   authentication and privacy).

   Further, deployment of SNMP versions prior to SNMPv3 is NOT
   RECOMMENDED.  Instead, it is RECOMMENDED to deploy SNMPv3 and to
   enable cryptographic security.  It is then a customer/operator
   responsibility to ensure that the SNMP entity giving access to an
   instance of this MIB module is properly configured to give access to
   the objects only to those principals (users) that have legitimate
   rights to indeed GET or SET (change/create/delete) them.

9.  References

9.1.  Normative References

   [RFC1155]   Rose, M. and K. McCloghrie, "Structure and Identification
               of Management Information for TCP/IP-based internets",
               STD 16, RFC 1155, May 1990.

   [RFC1157]   Case, J., Fedor, M., Schoffstall, M. and C. Davin,
               "Simple Network Management Protocol (SNMP)", STD 15, RFC
               1157, May 1990.

   [RFC1212]   Rose, M. and K. McCloghrie, Eds., "Concise MIB
               Definitions", STD 16, RFC 1212, March 1991.


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   [RFC1215]   Rose, M., "A Convention for Defining Traps for use with
               the SNMP", RFC 1215, March 1991.

   [RFC1303]   McCloghrie, K. and M. Rose, "A Convention for Describing
               SNMP-based Agents", RFC 1303, February 1992.

   [RFC1901]   Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
               "Introduction to Community-based SNMPv2", RFC 1901,
               January 1996.

   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

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

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

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

   [RFC3411]   Harrington, D., Presuhn, R. and B. Wijnen, "An
               Architecture for Describing Simple Network Management
               Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
               December 2002.

   [RFC3412]   Case, J., Harrington, D., Presuhn, R. and B. Wijnen,
               "Message Processing and Dispatching for the Simple
               Network Management Protocol (SNMP)", STD 62, RFC 3412,
               December 2002.

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

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

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


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   [RFC3416]   Presuhn, R., Ed., "Version 2 of the Protocol Operations
               for the Simple Network Management Protocol (SNMPv2)", STD
               62, RFC 3416, December 2002.

   [RFC3417]   Presuhn, R., Ed., "Transport Mappings for Version 2 of
               the Simple Network Management Protocol (SNMPv2)", STD 62,
               RFC 3417, December 2002.

   [RFC3418]   Presuhn, R., Ed., "Management Information Base (MIB) for
               Version 2 of the Simple Network Management Protocol
               (SNMP)", STD 62, RFC 3418, December 2002.

   [ASN1]      Information processing systems - Open Systems
               Interconnection - Specification of Abstract Syntax
               Notation One (ASN.1), International Organization for
               Standardization.  International Standard 8824, (December,
               1987).

9.2.  Informative References

   [RFC1908]   Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
               "Coexistence between Version 1 and Version 2 of the
               Internet-standard Network Management Framework", RFC
               1908, January 1996.

   [RFC2089]   Levi, D. and B. Wijnen, "Mapping SNMPv2 onto SNMPv1
               within a bilingual SNMP agent", RFC 2089, January 1997.

   [RFC2576]   Frye, R., Levi, D., Routhier, S. and B. Wijnen,
               "Coexistence between Version 1, Version 2, and Version 3
               of the Internet-standard Network Management Framework",
               RFC 2576, March 2000.

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


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Appendix A.  Change Log

A.1.  Changes From RFC 2576

   Section numbers below refer to the old section numbers from RFC 2576.
   Some section numbers have changed since RFC 2576.

   -  Added text to abstract about conversion of MIBs from SMIv1 to
      SMIv2.

   -  Added note at end of section 1.3 that all discussion of SNMPv2 PDU
      types and protocol operations applies to both SNMPv2c and SNMPv3.

   -  Added text at end of section 1.4 to clarify that there is no such
      thing as 'SNMPv3 access to MIB data', as SNMPv3 just uses SNMPv2
      PDU types and protocol operations.

   -  Moved section 1.4 to the beginning of section 4.

   -  Changed "MUST" to "SHOULD" in item (3) of the first list in
      Section 2.1.1 to since unconstrained INTEGER is not actually
      illegal in SMIv2.

   -  Changed "SHOULD" to "MUST" in item (13) of the first list in
      Section 2.1.1 to clarify that collecting related objects into
      groups is required when translating a MIB module from SMIv1 to
      SMIv2.

   -  Re-organized bullets in section 2.1.1 to improve clarity.

   -  Changed "SHOULD" to "MUST" in items (1) and (2) of Section 2.3
      since those updates are indeed required when translating a
      capabilities statement from the language defined by RFC 1303 into
      SMIv2.

   -  In the second bullet of the last part of Section 3 listing the
      SNMPv2 notification parameters, clarified that the snmpTrapOID
      parameter refers to the value portion (not the name portion) of
      the second variable-binding, and changed the wording in the text
      under bullet (1) of Section 3.2 from "the snmpTrapOID" to "the
      snmpTrapOID value" to emphasize this point.

   -  In bullet (6) of Section 3.2 emphasized that the SNMPv2 variable-
      bindings do not include sysUpTime.0 an snmpTrapOID.0.

   -  In Section 4.2 clarified that the 'Upstream Version' refers to the
      version used between the command generator or notification
      receiver and the proxy, and the 'Downstream Version' refers to the


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      version used between the proxy and the command responder or
      notification originator.  RFC 2576 neglected to mention the
      notification receiver and notification originator.

   -  In Section 4.1.2 added text noting that SNMPv1 access to MIB data
      SHOULD NOT be used when processing SNMPv2c or SNMPv3 messages and
      re-worded final paragraph to note that the sub-sections that
      follow are concerned solely with command responders that use
      SNMPv2 access to MIB data while processing an SNMPv1 request.

   -  Re-worded first bullet, section 4.2.1, to make it more readable.

   -  In Section 4.2.1 clarified that the error-index field must be set
      to zero in a translated GetResponse-PDU with an error-status of
      'tooBig' and made explicit the rationale for retrying a
      GetBulkRequest-PDU only once.

   -  Added text to the Deployment Hint in Section 4.2.2 to clarify that
      different principals should be used for SNMPv1 requests and
      SNMPv2/v3c requests if for SNMPv1 requests a principal for which
      Counter64 objects are not-in-view is used.

   -  In Section 5.2.1 clarified that the securityName value and the
      scopedPDU's contextSnmpEngineID and contextName values come from
      the selected entry in the snmpCommunityTable.  Also clarified how
      maxSizeResponseScopedPDU is determined and that
      securityStateReference must contain the community string of the
      original request.

   -  Added Section 5.2.4 on Proxy Forwarding Of Requests.

   -  In Section 5.3 clarified that snmpTargetAddrTMask is to be ignored
      whenever its use is not explicitly called for.

   -  Updated the LAST-UPDATED, CONTACT-INFO, and REVISION clauses and
      added a copyright notice to the DESCRIPTION clause of the MIB
      module's MODULE-IDENTITY invocation.

   -  Added text to DESCRIPTION of snmpCommunityName and
      snmpTrapCommunity to clarify why the object has no size
      restriction.

   -  Updated the description of snmpCommunityTransportTag to make it
      consistent with the rest of the document.

   -  Updated the description of 'snmpTargetAddrMMS' to clarify that a
      value of 0 means that the maximum message size is unknown.


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   -  Changed the name of 'snmpCommunityGroup' to
      'snmpCommunityTableGroup' in order to resolve a name conflict with
      the SNMPv2-MIB.

   -  Added compliance statement to SNMP-COMMUNITY-MIB for full read-
      create compliance.

   -  Divided references into Normative References and Informative
      Reference and updated them to point to current documents.

   -  Inserted current year into all copyright notices.

   -  Corrected various typographical and grammatical errors.

A.2.  Changes Between RFC 1908 and RFC 2576

   -  Editorial changes to comply with current RFC requirements.

   -  Added/updated copyright statements.

   -  Added Intellectual Property section.

   -  Replaced old introduction with complete new introduction/overview.

   -  Added content for the Security Considerations Section.

   -  Updated References to current documents.

   -  Updated text to use current SNMP terminology.

   -  Added coexistence for/with SNMPv3.

   -  Added description for SNMPv1 and SNMPv2c Message Processing Models
      and SNMPv1 and SNMPv2c Community-based Security Models.

   -  Added snmpCommunityMIB so that SNMPv1 and SNMPv2 community strings
      can be mapped into the SNMP Version Independent parameters which
      can then be used for access control using the standard SNMPv3
      View-based Access Control Model and the snmpVacmMIB.

   -  Added two MIB objects such that when an SNMPv1 notification (trap)
      must be converted into an SNMPv2 notification we add those two
      objects in order to preserve information about the address and
      community of the originating SNMPv1 agent.

   -  Included (and extended) from RFC 2089 the SNMPv2 to SNMPv1 mapping
      within a multi-lingual SNMP Engine.


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   -  Use keywords from RFC 2119 to describe requirements for
      compliance.

   -  Changed/added some rules for converting a MIB module from SMIv1 to
      SMIv2.

   -  Extended and improved the description of Proxy Forwarder behaviour
      when multiple SNMP versions are involved.

Editors' Addresses

   Rob Frye
   Vibrant Solutions
   2711 Prosperity Ave
   Fairfax, Virginia 22031
   U.S.A.

   Phone: +1 703 270 2000
   EMail: rfrye@vibrant-1.com

   David B. Levi
   Nortel Networks
   3505 Kesterwood Drive
   Knoxville, TN 37918
   U.S.A.

   Phone: +1 865 686 0432
   EMail: dlevi@nortelnetworks.com

   Shawn A. Routhier
   Wind River Systems, Inc.
   500 Wind River Way
   Alameda, CA 94501
   U.S.A.

   Phone: + 1 510 749 2095
   EMail: sar@epilogue.com

   Bert Wijnen
   Lucent Technologies
   Schagen 33
   3461 GL Linschoten
   Netherlands

   Phone: +31 348 407 775
   EMail: bwijnen@lucent.com


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Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

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

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

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

Acknowledgement

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


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