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rfc:rfc2576

Network Working Group R. Frye Request for Comments: 2576 CoSine Communications Category: Standards Track D. Levi

                                                       Nortel Networks
                                                           S. Routhier
                                               Integrated Systems Inc.
                                                             B. Wijnen
                                                   Lucent Technologies
                                                            March 2000
      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 standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

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

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 obsoletes RFC 1908 [13]
 and RFC2089 [14].

Table Of Contents

 1 Overview .....................................................    2
 1.1 SNMPv1 .....................................................    3
 1.2 SNMPv2 .....................................................    4
 1.3 SNMPv3 .....................................................    4
 1.4 SNMPv1 and SNMPv2 Access to MIB Data .......................    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 ........................    9
 2.2 Compliance Statements ......................................    9
 2.3 Capabilities Statements ....................................   10

Frye, et al. Standards Track [Page 1] RFC 2576 Coexistence between SNMP versions March 2000

 3 Translating Notifications Parameters .........................   10
 3.1 Translating  SNMPv1  Notification  Parameters  to  SNMPv2
      Notification Parameters ...................................   12
 3.2 Translating  SNMPv2  Notification  Parameters  to  SNMPv1
      Notification Parameters ...................................   13
 4 Approaches to Coexistence in a Multi-lingual Network .........   14
 4.1 Multi-lingual implementations ..............................   15
 4.1.1 Command Generator ........................................   15
 4.1.2 Command Responder ........................................   15
 4.1.2.1 Handling Counter64 .....................................   16
 4.1.2.2 Mapping SNMPv2 Exceptions ..............................   16
 4.1.2.2.1 Mapping noSuchObject and noSuchInstance ..............   17
 4.1.2.2.2 Mapping endOfMibView .................................   17
 4.1.2.3 Processing An SNMPv1 GetRequest ........................   18
 4.1.2.4 Processing An SNMPv1 GetNextRequest ....................   19
 4.1.2.5 Processing An SNMPv1 SetRequest ........................   20
 4.1.3 Notification Originator ..................................   20
 4.1.4 Notification Receiver ....................................   21
 4.2 Proxy Implementations ......................................   21
 4.2.1 Upstream Version Greater Than Downstream Version .........   21
 4.2.2 Upstream Version Less Than Downstream Version ............   22
 4.3 Error Status Mappings ......................................   24
 5 Message Processing Models and Security Models ................   25
 5.1 Mappings ...................................................   25
 5.2 The SNMPv1 MP Model and SNMPv1  Community-based  Security
      Model .....................................................   26
 5.2.1 Processing An Incoming Request ...........................   26
 5.2.2 Generating An Outgoing Response ..........................   28
 5.2.3 Generating An Outgoing Notification ......................   28
 5.3 The SNMP Community MIB Module ..............................   29
 6 Intellectual Property ........................................   39
 7 Acknowledgments ..............................................   39
 8 Security Considerations ......................................   40
 9 References ...................................................   40
 10 Editor's Addresses ..........................................   42
 A. Changes From RFC1908 ........................................   43
 Full Copyright Statement .......................................   44

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).

Frye, et al. Standards Track [Page 2] RFC 2576 Coexistence between SNMP versions March 2000

 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 RFC2119 [15].
 There are four general aspects of coexistence described in this
 document.  Each of these is described in a separate section:
  1. Conversion of MIB documents between SMIv1 and SMIv2 formats is

documented in section 2.

  1. Mapping of notification parameters is documented in section 3.
  1. 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.
  1. 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).

1.1. SNMPv1

 SNMPv1 is defined by these documents:
  1. STD 15, RFC 1157 [2] which defines the Simple Network

Management Protocol (SNMPv1), the protocol used for network

       access to managed objects.
  1. STD 16, RFC 1155 [1] which defines the Structure of Management

Information (SMIv1), the mechanisms used for describing and

       naming objects for the purpose of management.
  1. STD 16, RFC 1212 [3] which defines a more concise description

mechanism, which is wholly consistent with the SMIv1.

  1. RFC 1215 [4] 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.

Frye, et al. Standards Track [Page 3] RFC 2576 Coexistence between SNMP versions March 2000

1.2. SNMPv2

 SNMPv2 is defined by these documents:
  1. STD 58, RFC 2578 which defines Version 2 of the Structure of

Management Information (SMIv2) [7].

  1. STD 58, RFC 2579 which defines common MIB "Textual Conventions"

[8].

  1. STD 58, RFC 2580 which defines Conformance Statements and

requirements for defining agent and manager capabilities [9].

  1. RFC 1905 which defines the Protocol Operations used in

processing [10].

  1. RFC 1906 which defines the Transport Mappings used "on the

wire" [11].

  1. RFC 1907 which defines the basic Management Information Base

for monitoring and controlling some basic common functions of

       SNMP entities [12].
 Note that SMIv2 as used throughout this document refers to the first
 three documents listed above (RFCs 2578, 2579, and 2580).
 The following document augments the definition of SNMPv2:
  1. RFC 1901 [6] 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:
  1. RFC 2571 which defines an Architecture for Describing SNMP

Management Frameworks [16].

  1. RFC 2572 which defines Message Processing and Dispatching [17].
  1. RFC 2573 which defines various SNMP Applications [18].
  1. RFC 2574 which defines the User-based Security Model (USM),

providing for both Authenticated and Private (encrypted) SNMP

       messages [19].

Frye, et al. Standards Track [Page 4] RFC 2576 Coexistence between SNMP versions March 2000

  1. RFC 2575 which defines the View-based Access Control Model

(VACM), providing the ability to limit access to different MIB

       objects on a per-user basis [20].
 SNMPv3 also uses the SNMPv2 definitions of RFCs 1905 through 1907 and
 the SMIv2 definitions of 2578 through 2580 described above.

1.4. SNMPv1 and SNMPv2 Access to MIB Data

 In several places, 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:
  1. Error-status values generated.
  1. Generation of exception codes.
  1. Use of the Counter64 data type.
  1. 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.

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 (1988)

Frye, et al. Standards Track [Page 5] RFC 2576 Coexistence between SNMP versions March 2000

 [11] 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.

2.1. MIB Modules

 MIB modules defined using the SMIv1 may continue to be used with
 protocol versions which use SNMPv2 PDUs.  However, for the 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 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 MUST have the value of its SYNTAX clause
      changed to Integer32, or have an appropriate range specified.
 (4)  For any object with a SYNTAX clause value of Counter, the object
      MUST have the value of its SYNTAX clause changed to Counter32.
 (5)  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.
 (6)  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

Frye, et al. Standards Track [Page 6] RFC 2576 Coexistence between SNMP versions March 2000

      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.
 (7)  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.
 (8)  For any object not containing a DESCRIPTION clause, the object
      MUST have a DESCRIPTION clause defined.
 (9)  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.
 (10) 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.  This approach allows 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.
 (11) 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).
 (12) 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.
 (13) One or more OBJECT-GROUPS MUST be defined, and related objects
      SHOULD be collected into appropriate groups.  Note that SMIv2
      requires all OBJECT-TYPEs to be a member of at least one
      OBJECT-GROUP.

Frye, et al. Standards Track [Page 7] RFC 2576 Coexistence between SNMP versions March 2000

 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 RFC2578 [7], and the RowStatus and StorageType TEXTUAL-
      CONVENTIONs are described in section 2 of RFC2579 [8].
 (2)  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.
 (3)  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.
 (4)  For any object which represents a measurement in some kind of
      units, a UNITS clause SHOULD be added to the definition of that
      object.
 (5)  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.
 Finally, to avoid common errors in SMIv1 MIB modules:
 (1)  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".
 (2)  For any conceptual row object that is not contained immediately
      subordinate to a conceptual table, the value of the STATUS
      clause of that object (and all subordinate objects) MUST be
      changed to "obsolete".

Frye, et al. Standards Track [Page 8] RFC 2576 Coexistence between SNMP versions March 2000

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:
 (1)  The IMPORTS statement MUST NOT reference RFC-1215 [4], 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.

Frye, et al. Standards Track [Page 9] RFC 2576 Coexistence between SNMP versions March 2000

 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

 RFC1303 [5] uses the MODULE-CONFORMANCE macro to describe an agent's
 capabilities with respect to one or more MIB modules.  Converting
 such a description for use with the SMIv2 requires these changes:
 (1)  The macro name AGENT-CAPABILITIES SHOULD be used instead of
      MODULE-CONFORMANCE.
 (2)  The STATUS clause SHOULD 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 RFC2580 [9].
 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 Notifications 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
 refered to in this document as 'SNMPv1 notification parameters'.  The
 format of parameters used for SNMPv2 notification protocol operations
 is refered to in this document as 'SNMPv2 notification parameters'.

Frye, et al. Standards Track [Page 10] RFC 2576 Coexistence between SNMP versions March 2000

 The situations where notification parameters MUST be translated are:
  1. 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.
  1. 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.
 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:
  1. An enterprise parameter (OBJECT IDENTIFIER).
  1. An agent-addr parameter (NetworkAddress).
  1. A generic-trap parameter (INTEGER).
  1. A specific-trap parameter (INTEGER).
  1. A time-stamp parameter (TimeTicks).
  1. A list of variable-bindings (VarBindList).
 SNMPv2 notification parameters consist of:
  1. A sysUpTime parameter (TimeTicks). This appears in the first

variable-binding in an SNMPv2-Trap-PDU or InformRequest-PDU.

  1. An snmpTrapOID parameter (OBJECT IDENTIFIER). This appears in

the second variable-binding in an SNMPv2-Trap-PDU or

       InformRequest-PDU.
  1. A list of variable-bindings (VarBindList). This refers to all

but the first two variable-bindings in an SNMPv2-Trap-PDU or

       InformRequest-PDU.

Frye, et al. Standards Track [Page 11] RFC 2576 Coexistence between SNMP versions March 2000

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.
 (2)  If the SNMPv1 generic-trap parameter is 'enterpriseSpecific(6)',
      the SNMPv2 snmpTrapOID parameter SHALL be the concatentation 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 RFC1907
      [12]:
  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 [12], and the value SHALL be the SNMPv1
      enterprise parameter.

Frye, et al. Standards Track [Page 12] RFC 2576 Coexistence between SNMP versions March 2000

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:
  1. If the SNMPv2 snmpTrapOID parameter is one of the standard

traps as defined in RFC1907 [12], then the SNMPv1 enterprise

       parameter SHALL be set to the value of the variable-binding in
       the SNMPv2 variable-bindings whose name is 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 RFC1907 [12].
  1. If the SNMPv2 snmpTrapOID parameter is not one of the standard

traps as defined in RFC1907 [12], then the SNMPv1 enterprise

       parameter SHALL be determined from the SNMPv2 snmpTrapOID
       parameter as follows:
  1. If the next-to-last sub-identifier of the snmpTrapOID is

zero, then the SNMPv1 enterprise SHALL be the SNMPv2

          snmpTrapOID with the last 2 sub-identifiers removed,
          otherwise
  1. If the next-to-last sub-identifier of the snmpTrapOID is

non-zero, then the SNMPv1 enterprise SHALL be the SNMPv2

          snmpTrapOID with the last sub-identifier removed.
 (2)  The SNMPv1 agent-addr parameter SHALL be determined based on the
      situation in which the translation occurs.
  1. 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.
  1. 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.

Frye, et al. Standards Track [Page 13] RFC 2576 Coexistence between SNMP versions March 2000

 (3)  If the SNMPv2 snmpTrapOID parameter is one of the standard traps
      as defined in RFC1907 [12], 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
      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 RFC1907 [12], 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.  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 4.1.3 and section 4.2).

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.

Frye, et al. Standards Track [Page 14] RFC 2576 Coexistence between SNMP versions March 2000

4.1. 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.

4.1.1. 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
 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.

4.1.2. 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:
  1. Deal correctly with SNMPv2 access to MIB data that returns a

Counter64 value while processing an SNMPv1 message,

  1. Deal correctly with SNMPv2 access to MIB data that returns one

of the three exception values while processing an SNMPv1

       message, and
  1. 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.  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 some combination of SNMPv1 and SNMPv2 access to MIB data.

Frye, et al. Standards Track [Page 15] RFC 2576 Coexistence between SNMP versions March 2000

4.1.2.1. Handling Counter64

 The SMIv2 [7] 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:
  1. 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-
       status of noSuchName and the error-index set to the variable
       binding that caused this error.
  1. 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.
  1. 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.

4.1.2.2. 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
 error-index value.

Frye, et al. Standards Track [Page 16] RFC 2576 Coexistence between SNMP versions March 2000

 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.
  1. For a GetRequest, a noSuchObject or noSuchInstance exception

may be returned.

  1. For a GetNextRequest, an endOfMibView exception may be

returned.

  1. 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.

4.1.2.2.1. 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
 (there may be more than one and 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.

4.1.2.2.2. 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 (there may be more than one and 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.

Frye, et al. Standards Track [Page 17] RFC 2576 Coexistence between SNMP versions March 2000

4.1.2.3. 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,
  1. The error status SHALL be translated to an SNMPv1 error-status

using the table in section 4.3, "Error Status Mappings".

  1. The error-index SHALL be set to the position (in the original

request) of the variable binding that caused the error-status.

  1. 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.
 (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:
  1. The error-status SHALL be set to noSuchName,
  1. The error-index SHALL be set to the position (in the variable

binding list of the original request) of the selected variable

       binding, and
  1. 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:
  1. The error-status SHALL be set to noError,
  1. The error-index SHALL be set to zero, and
  1. The variable binding list of the response SHALL be composed

from the data as it is returned by the access to MIB data.

Frye, et al. Standards Track [Page 18] RFC 2576 Coexistence between SNMP versions March 2000

4.1.2.4. Processing An SNMPv1 GetNextRequest

 When processing an SNMPv1 GetNextRequest, the following procedures
 MUST be followed when an SNMPv2 access to MIB data is called 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 4.3, "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.
 (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 occurs.
 (2)  If there is any variable binding that contains an SNMPv2
      exception endOfMibView (there may be more than one, it is an
      implementation decision as to which is chosen):
  1. The error-status SHALL be set to noSuchName,
  1. 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
  1. 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:

Frye, et al. Standards Track [Page 19] RFC 2576 Coexistence between SNMP versions March 2000

  1. The error-status SHALL be set to noError,
  1. The error-index SHALL be set to zero, and
  1. The variable binding list of the response SHALL be composed

from the data as it is returned by the access to MIB data.

4.1.2.5. Processing An SNMPv1 SetRequest

 When processing an SNMPv1 SetRequest, the following procedures MUST
 be followed when calling SNMPv2 MIB access routines.
 When such MIB access routines return response data using SNMPv2
 syntax and error-status values, and the error-status is anything
 other than noError, then:
  1. The error status SHALL be translated to an SNMPv1 error-status

using the table in section 4.3, "Error Status Mappings".

  1. The error-index SHALL be set to the position (in the original

request) of the variable binding that caused the error-status.

  1. 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.

4.1.3. Notification Originator

 A notification originator must be able to translate between SNMPv1
 notifications 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).

Frye, et al. Standards Track [Page 20] RFC 2576 Coexistence between SNMP versions March 2000

 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 [18], 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.

4.1.4. 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
 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.

4.2. 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 and
 the proxy, and the 'Downstream Version' refers to the version used
 between the proxy and the command responder, regardless of the PDU
 type or direction.

4.2.1. Upstream Version Greater Than Downstream Version

  1. If a GetBulkRequest-PDU is received and must be forwarded using

the SNMPv1 message version, the proxy forwarder SHALL set the

    non-repeaters and max-repetitions fields to 0, and SHALL set the
    tag of the PDU to GetNextRequest-PDU.

Frye, et al. Standards Track [Page 21] RFC 2576 Coexistence between SNMP versions March 2000

  1. If a GetResponse-PDU is received whose error-status field has a

value of 'tooBig', 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 before
    forwarding the response.
  1. 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-
    bindings field, and change the error-status field to 'noError'
    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.'
  1. 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 nobjects.

4.2.2. Upstream Version Less Than Downstream Version

  1. 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.

Frye, et al. Standards Track [Page 22] RFC 2576 Coexistence between SNMP versions March 2000

  1. 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.
  1. 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.
  1. 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, the error-status value is modified using
    the mappings in section 4.3.
  1. 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

Frye, et al. Standards Track [Page 23] RFC 2576 Coexistence between SNMP versions March 2000

    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.
  1. 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.

4.3. 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

Frye, et al. Standards Track [Page 24] RFC 2576 Coexistence between SNMP versions March 2000

 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.

5. Message Processing Models and Security Models

 In order to adapt SNMPv1 (and SNMPv2c) into the SNMP architecture,
 the following models are defined in this document:
  1. The SNMPv1 Message Processing Model
  1. The SNMPv1 Community-Based Security Model
 The following models are also described in this document:
  1. The SNMPv2c Message Processing Model
  1. 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 [16].  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.

Frye, et al. Standards Track [Page 25] RFC 2576 Coexistence between SNMP versions March 2000

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 RFC1157 [2], with differences and
 clarifications as described in the following sections.  The
 SnmpMessageProcessingModel value for SNMPv1 is 0 (the value for
 SNMPv2c is 1).

5.2.1. Processing An Incoming Request

 In RFC1157 [2], 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:
  1. The messageProcessingModel, which will be 0 (or 1 for SNMPv2c).
  1. 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).
  1. The securityParameters, which consist of the community string

and the message's source and destination transport domains and

       addresses.
  1. The securityModel, which will be 1 (or 2 for SNMPv2c).
  1. The securityLevel, which will be noAuthNoPriv.
  1. 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:
  1. The community string is equal to the snmpCommunityName value.
  1. 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

Frye, et al. Standards Track [Page 26] RFC 2576 Coexistence between SNMP versions March 2000

       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 RFC1157 [2], and the snmpInBadCommunityNames counter is
 incremented.
 The parameters returned from the Community-Based Security Model are:
  1. The securityEngineID, which will always be the local value of

snmpEngineID.0.

  1. The securityName.
  1. The scopedPDU. Note that this parameter will actually consist

of three values, the contextSnmpEngineID, the contextName, and

       the PDU.  These must be separate values, since the first two do
       not actually appear in the message.
  1. The maxSizeResponseScopedPDU.
  1. The securityStateReference.
 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:
  1. The messageProcessingModel, which will be 0 (or 1 for SNMPv2c).
  1. The securityModel, which will be 1 (or 2 for SNMPv2c).
  1. The securityName, which was returned from the call to

processIncomingMsg.

  1. The securityLevel, which is noAuthNoPriv.
  1. The contextEngineID, which was returned as part of the

ScopedPDU from the call to processIncomingMsg.

  1. The contextName, which was returned as part of the ScopedPDU

from the call to processIncomingMsg.

  1. The pduVersion, which should indicate an SNMPv1 version PDU (if

the message version was SNMPv2c, this would be an SNMPv2

       version PDU).

Frye, et al. Standards Track [Page 27] RFC 2576 Coexistence between SNMP versions March 2000

  1. The PDU, which was returned as part of the ScopedPDU from the

call to processIncomingMsg.

  1. The maxSizeResponseScopedPDU which was returned from the call

to processIncomingMsg.

  1. 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 stateReference
 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:
  1. The securityName must be equal to the snmpCommunitySecurityName

value.

  1. The contextEngineID must be equal to the

snmpCommunityContextEngineID value.

  1. The contextName must be equal to the snmpCommunityContextName

value.

  1. If the snmpCommunityTransportTag is an empty string, it is

ignored for the purpose of matching. If the

       snmpCommunityTransportTag is not an empty string, the

Frye, et al. Standards Track [Page 28] RFC 2576 Coexistence between SNMP versions March 2000

       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.

5.3. 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
 features are accomplished by providing a tag in the
 snmpCommunityTable which selects sets of entries in the
 snmpTargetAddrTable [18].  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).
 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

Frye, et al. Standards Track [Page 29] RFC 2576 Coexistence between SNMP versions March 2000

 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.

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 "200003060000Z"          -- 6 Mar 2000, midnight
  ORGANIZATION "SNMPv3 Working Group"
  CONTACT-INFO "WG-email:   snmpv3@lists.tislabs.com
                Subscribe:  majordomo@lists.tislabs.com
                            In msg body:  subscribe snmpv3
                Chair:      Russ Mundy
                            TIS Labs at Network Associates
                Postal:     3060 Washington Rd
                            Glenwood MD 21738
                            USA
                Email:      mundy@tislabs.com
                Phone:      +1-301-854-6889

Frye, et al. Standards Track [Page 30] RFC 2576 Coexistence between SNMP versions March 2000

                Co-editor:  Rob Frye
                            CoSine Communications
                Postal:     1200 Bridge Parkway
                            Redwood City, CA 94065
                            USA
                E-mail:     rfrye@cosinecom.com
                Phone:      +1 703 725 1130
                Co-editor:  David B. Levi
                            Nortel Networks
                Postal:     3505 Kesterwood Drive
                            Knoxville, TN 37918
                E-mail:     dlevi@nortelnetworks.com
                Phone:      +1 423 686 0432
                Co-editor:  Shawn A. Routhier
                            Integrated Systems Inc.
                Postal:     333 North Ave 4th Floor
                            Wakefield, MA 01880
                E-mail:     sar@epilogue.com
                Phone:      +1 781 245 0804
                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."
      REVISION "200003060000Z" -- 6 Mar 2000
      DESCRIPTION "This version published as RFC 2576."
      REVISION "199905130000Z" -- 13 May 1999
      DESCRIPTION "The Initial Revision"
  ::= { 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

Frye, et al. Standards Track [Page 31] RFC 2576 Coexistence between SNMP versions March 2000

– 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
  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."
  ::= { snmpCommunityEntry 2 }

Frye, et al. Standards Track [Page 32] RFC 2576 Coexistence between SNMP versions March 2000

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

  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
       from which a command responder application will accept
       management requests.  If a management request containing
       this community is received on a transport endpoint other
       than the transport endpoints identified by this object,
       the request is deemed unauthentic.
       The transports identified by this object are specified

Frye, et al. Standards Track [Page 33] RFC 2576 Coexistence between SNMP versions March 2000

       in the snmpTargetAddrTable.  Entries in that table
       whose snmpTargetAddrTagList contains this tag value
       are identified.
       If the value of this object has zero-length, transport
       endpoints are not checked when authenticating messages
       containing this community string."
  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
  MAX-ACCESS   not-accessible
  STATUS       current
  DESCRIPTION
      "The table of mask and mms values associated with the

Frye, et al. Standards Track [Page 34] RFC 2576 Coexistence between SNMP versions March 2000

       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
       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.

Frye, et al. Standards Track [Page 35] RFC 2576 Coexistence between SNMP versions March 2000

       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."
  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 }

snmpTrapCommunity OBJECT-TYPE

  SYNTAX      OCTET STRING
  MAX-ACCESS  accessible-for-notify
  STATUS      current
  DESCRIPTION

Frye, et al. Standards Track [Page 36] RFC 2576 Coexistence between SNMP versions March 2000

      "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."
  ::= { 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 { snmpCommunityGroup }
      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."
      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

Frye, et al. Standards Track [Page 37] RFC 2576 Coexistence between SNMP versions March 2000

      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 }

snmpCommunityGroup OBJECT-GROUP

  OBJECTS {
      snmpCommunityName,
      snmpCommunitySecurityName,
      snmpCommunityContextEngineID,
      snmpCommunityContextName,
      snmpCommunityTransportTag,
      snmpCommunityStorageType,
      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

Frye, et al. Standards Track [Page 38] RFC 2576 Coexistence between SNMP versions March 2000

       translating to SNMPv2c or SNMPv3."
  ::= { snmpCommunityMIBGroups 3 }

END

6. Intellectual Property

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

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

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 (Cabletron Systems Inc.)
    David Levi (SNMP Research, Inc.)
    Brian O'Keefe (Hewlett Packard)
    Jon Saperia (IronBridge Networks, Inc.)
    Steve Waldbusser (International Network Services)

Frye, et al. Standards Track [Page 39] RFC 2576 Coexistence between SNMP versions March 2000

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.
 Further, the SNMP-COMMUNITY-MIB 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
 the SNMP-COMMUNITY-MIB, and in particular, to make it inaccessible
 when using the 'public' community string.
 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.  Careful configuration of
 proxies is required to address such situations.  One approach to deal
 with such situations might be to use an encrypted tunnel.

9. References

 [1]  Rose, M. and K. McCloghrie, "Structure and Identification of
      Management Information for TCP/IP-based internets", STD 16, RFC
      1155, May 1990.
 [2]  Case, J., Fedor, M., Schoffstall, M. and J. Davin, "Simple
      Network Management Protocol", STD 15, RFC 1157, May 1990.
 [3]  McCloghrie, K. and M. Rose, Editors, "Concise MIB Definitions",
      STD 16, RFC 1212, March 1991.
 [4]  Rose, M., "A Convention for Defining Traps for use with the
      SNMP", RFC 1215, March 1991.
 [5]  McCloghrie, K. and M. Rose, "A Convention for Describing SNMP-
      based Agents", RFC 1303, February 1992.
 [6]  Case, J., McCloghrie, K., Rose, M. and S.Waldbusser,
      "Introduction to Community-based SNMPv2", RFC 1901, January
      1996.

Frye, et al. Standards Track [Page 40] RFC 2576 Coexistence between SNMP versions March 2000

 [7]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
      M.  and S. Waldbusser, "Structure of Management Information
      Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
 [8]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
      M.  and S. Waldbusser, "Textual Conventions for SMIv2", STD 58,
      RFC 2579, April 1999.
 [9]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
      M.  and S. Waldbusser, "Conformance Statements for SMIv2", STD
      58, RFC 2580, April 1999.
 [10] Case, J., McCloghrie, K., Rose, M. and S.Waldbusser, "Protocol
      Operations for Version 2 of the Simple Network Management
      Protocol (SNMPv2)", RFC 1905, January 1996.
 [11] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser, "Transport
      Mappings for Version 2 of the Simple Network Management Protocol
      (SNMPv2)", RFC 1906, January 1996.
 [12] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
      "Management Information Base for Version 2 of the Simple Network
      Management Protocol (SNMPv2)", RFC 1907, January 1996.
 [13] 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.
 [14] Levi, D. and B. Wijnen, "Mapping SNMPv2 onto SNMPv1 within a
      bi-lingual SNMP agent", RFC 2089, January 1997.
 [15] Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.
 [16] Harrington, D. and B. Wijnen, "An Architecture for Describing
      SNMP Management Frameworks", RFC 2571, May 1999.
 [17] Case, J., Harrington, D. and B. Wijnen, "Message Processing and
      Dispatching for the Simple Network Management Protocol (SNMP)",
      RFC 2572, May 1999.
 [18] Levi, D., Meyer, P. and B. Stewart, "SNMP Applications", RFC
      2573, May 1999.
 [19] Blumenthal, U. and Wijnen, B., "The User-Based Security Model
      for Version 3 of the Simple Network Management Protocol (SNMP)",
      RFC 2574, May 1999.

Frye, et al. Standards Track [Page 41] RFC 2576 Coexistence between SNMP versions March 2000

 [20] Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based Access
      Control Model for the Simple Network Management Protocol
      (SNMP)", RFC 2575, May 1999.

10. Editor's Addresses

 Rob Frye
 CoSine Communications
 1200 Bridge Parkway
 Redwood City, CA 94065
 U.S.A.
 Phone: +1 703 725 1130
 EMail: rfrye@cosinecom.com
 David B. Levi
 Nortel Networks
 3505 Kesterwood Drive
 Knoxville, TN 37918
 U.S.A.
 Phone: +1 423 686 0432
 EMail: dlevi@nortelnetworks.com
 Shawn A. Routhier
 Integrated Systems Inc.
 333 North Ave 4th Floor
 Wakefield MA 01880
 U.S.A.
 Phone: + 1 781 245 0804
 EMail: sar@epilogue.com
 Bert Wijnen
 Lucent Technologies
 Schagen 33
 3461 GL Linschoten
 Netherlands
 Phone: +31 348 407-775
 EMail: wijnen@lucent.com

Frye, et al. Standards Track [Page 42] RFC 2576 Coexistence between SNMP versions March 2000

A. Changes From RFC1908

  1. Editorial changes to comply with current RFC requirements.
  1. Added/updated copyright statements.
  1. Added Intellectual Property section.
  1. Replaced old introduction with complete new introduction/overview.
  1. Added content for the Security Considerations Section.
  1. Updated References to current documents.
  1. Updated text to use current SNMP terminology.
  1. Added coexistence for/with SNMPv3.
  1. Added description for SNMPv1 and SNMPv2c Message Processing

Models and SNMPv1 and SNMPv2c Community-based Security

    Models.
  1. Added snmpCommunityMIB so that SNMPv1 and SNMPv2 community

strings can be mapped into the SNMP Version Independent

    paramaters which can then be used for access control using the
    standard SNMPv3 View-based Access Control Model and the
    snmpVacmMIB.
  1. 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.
  1. Included (and extended) from RFC2089 the SNMPv2 to SNMPv1

mapping within a multi-lingual SNMP Engine.

  1. Use keywords from RFC 2119 to describe requirements for

compliance.

  1. Changed/added some rules for converting a MIB module from

SMIv1 to SMIv2.

  1. Extended and improved the description of Proxy Forwarder

behaviour when multiple SNMP versions are involved.

Frye, et al. Standards Track [Page 43] RFC 2576 Coexistence between SNMP versions March 2000

Full Copyright Statement

 Copyright (C) The Internet Society (2000).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
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Frye, et al. Standards Track [Page 44]

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