rfc2576.txt

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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



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   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).





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   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:

      -  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).

1.1.  SNMPv1

   SNMPv1 is defined by these documents:

      -  STD 15, RFC 1157 [2] which defines the Simple Network
         Management Protocol (SNMPv1), the protocol used for network
         access to managed objects.

      -  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.

      -  STD 16, RFC 1212 [3] which defines a more concise description
         mechanism, which is wholly consistent with the SMIv1.

      -  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.





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1.2.  SNMPv2

   SNMPv2 is defined by these documents:

      -  STD 58, RFC 2578 which defines Version 2 of the Structure of
         Management Information (SMIv2) [7].

      -  STD 58, RFC 2579 which defines common MIB "Textual Conventions"
         [8].

      -  STD 58, RFC 2580 which defines Conformance Statements and
         requirements for defining agent and manager capabilities [9].

      -  RFC 1905 which defines the Protocol Operations used in
         processing [10].

      -  RFC 1906 which defines the Transport Mappings used "on the
         wire" [11].

      -  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:

      -  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:

      -  RFC 2571 which defines an Architecture for Describing SNMP
         Management Frameworks [16].

      -  RFC 2572 which defines Message Processing and Dispatching [17].

      -  RFC 2573 which defines various SNMP Applications [18].

      -  RFC 2574 which defines the User-based Security Model (USM),
         providing for both Authenticated and Private (encrypted) SNMP
         messages [19].





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      -  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:

      -  Error-status values generated.

      -  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.

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)



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   [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