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rfc:rfc1901

Network Working Group SNMPv2 Working Group Request for Comments: 1901 J. Case Category: Experimental SNMP Research, Inc.

                                                         K. McCloghrie
                                                   Cisco Systems, Inc.
                                                               M. Rose
                                          Dover Beach Consulting, Inc.
                                                         S. Waldbusser
                                        International Network Services
                                                          January 1996
               Introduction to Community-based SNMPv2

Status of this Memo

 This document specifies an Experimental protocol for the Internet
 community.  This memo does not specify an Internet standard of any
 kind.  Discussion and suggestions for improvement are requested.
 Distribution of this memo is unlimited.

Table of Contents

 1. Introduction ................................................    1
 2. Components of the SNMPv2 Framework ..........................    2
 2.1 Structure of Management Information ........................    2
 2.2 Textual Conventions ........................................    3
 2.3 Conformance Statements .....................................    3
 2.4 Protocol Operations ........................................    3
 2.5 Transport Mappings .........................................    4
 2.6 Protocol Instrumentation ...................................    4
 3. The Community-based Administrative Framework ................    4
 4. Security Considerations .....................................    5
 5. Editor's Address ............................................    6
 6. Acknowledgements ............................................    6
 7. References ..................................................    7

1. Introduction

 The purpose of this document is to define the Community-based
 Administrative Framework for the SNMP version 2 framework (SNMPv2).
 The SNMPv2 framework is fully described in [1-6].  This framework is
 derived from the original Internet-standard Network Management
 Framework (SNMPv1), which consists of these three documents:
    STD 16, RFC 1155 [7] which defines the Structure of Management
    Information (SMI), the mechanisms used for describing and naming
    objects for the purpose of management.

SNMPv2 Working Group Experimental [Page 1] RFC 1901 Introduction to Community-based SNMPv2 January 1996

    STD 16, RFC 1212 [8] which defines a more concise description
    mechanism, which is wholly consistent with the SMI.
    STD 15, RFC 1157 [9] which defines the Simple Network Management
    Protocol (SNMP), the protocol used for network access to managed
    objects.
 For information on coexistence between SNMPv1 and SNMPv2, consult
 [10].

2. Components of the SNMPv2 Framework

 A management system contains:  several (potentially many) nodes, each
 with a processing entity, termed an agent, which has access to
 management instrumentation; at least one management station; and, a
 management protocol, used to convey management information between
 the agents and management stations.  Operations of the protocol are
 carried out under an administrative framework which defines
 authentication, authorization, access control, and privacy policies.
 Management stations execute management applications which monitor and
 control managed elements.  Managed elements are devices such as
 hosts, routers, terminal servers, etc., which are monitored and
 controlled via access to their management information.

2.1. Structure of Management Information

 Management information is viewed as a collection of managed objects,
 residing in a virtual information store, termed the Management
 Information Base (MIB).  Collections of related objects are defined
 in MIB modules.  These modules are written using a subset of OSI's
 Abstract Syntax Notation One (ASN.1) [11].  It is the purpose of the
 Structure of Management Information for SNMPv2 document [1] to define
 that subset.
 The SMI is divided into three parts:  module definitions, object
 definitions, and, trap definitions.
 (1)  Module definitions are used when describing information modules.
      An ASN.1 macro, MODULE-IDENTITY, is used to concisely convey the
      semantics of an information module.
 (2)  Object definitions are used when describing managed objects.  An
      ASN.1 macro, OBJECT-TYPE, is used to concisely convey the syntax
      and semantics of a managed object.
 (3)  Notification definitions are used when describing unsolicited
      transmissions of management information.  An ASN.1 macro,

SNMPv2 Working Group Experimental [Page 2] RFC 1901 Introduction to Community-based SNMPv2 January 1996

      NOTIFICATION-TYPE, is used to concisely convey the syntax and
      semantics of a notification.

2.2. Textual Conventions

 When designing a MIB module, it is often useful to define new types
 similar to those defined in the SMI.  In comparison to a type defined
 in the SMI, each of these new types has a different name, a similar
 syntax, but a more precise semantics.  These newly defined types are
 termed textual conventions, and are used for the convenience of
 humans reading the MIB module.  It is the purpose of the Textual
 Conventions for SNMPv2 document [2] to define the initial set of
 textual conventions available to all MIB modules.
 Objects defined using a textual convention are always encoded by
 means of the rules that define their primitive type.  However,
 textual conventions often have special semantics associated with
 them.  As such, an ASN.1 macro, TEXTUAL-CONVENTION, is used to
 concisely convey the syntax and semantics of a textual convention.

2.3. Conformance Statements

 It may be useful to define the acceptable lower-bounds of
 implementation, along with the actual level of implementation
 achieved.  It is the purpose of the Conformance Statements for SNMPv2
 document [3] to define the notation used for these purposes.  There
 are two kinds of notations:
 (1)  Compliance statements are used when describing requirements for
      agents with respect to object definitions.  An ASN.1 macro,
      MODULE-COMPLIANCE, is used to concisely convey such requirements.
 (2)  Capability statements are used when describing capabilities of
      agents with respect to object definitions.  An ASN.1 macro, AGENT-
      CAPABILITIES, is used to concisely convey such capabilities.
 Finally, collections of related objects are grouped together to form
 a unit of conformance.  An ASN.1 macro, OBJECT-GROUP, is used to
 concisely convey the syntax and semantics of a group.

2.4. Protocol Operations

 The management protocol provides for the exchange of messages which
 convey management information between the agents and the management
 stations.  The form of these messages is a message "wrapper" which
 encapsulates a Protocol Data Unit (PDU).

SNMPv2 Working Group Experimental [Page 3] RFC 1901 Introduction to Community-based SNMPv2 January 1996

 It is the purpose of the Protocol Operations for SNMPv2 document [4]
 to define the operations of the protocol with respect to the sending
 and receiving of the PDUs.

2.5. Transport Mappings

 The management protocol, version 2 of the Simple Network Management
 Protocol, may be used over a variety of protocol suites.  It is the
 purpose of the Transport Mappings for SNMPv2 document [5] to define
 how the SNMPv2 maps onto an initial set of transport domains.  Other
 mappings may be defined in the future.
 Although several mappings are defined, the mapping onto UDP is the
 preferred mapping.  As such, to provide for the greatest level of
 interoperability, systems which choose to deploy other mappings
 should also provide for proxy service to the UDP mapping.

2.6. Protocol Instrumentation

 It is the purpose of the Management Information Base for SNMPv2
 document [6] to define managed objects which describe the behavior of
 a SNMPv2 entity.

3. The Community-based Administrative Framework

 It is the purpose of an administrative framework to define an
 infrastructure through which effective management can be realized in
 a variety of configurations and environments.  Specified as a part
 of, or as extensions of, an administrative framework are security
 mechanisms used to achieve an administratively-defined level of
 security for protocol interactions.
 The administrative framework for SNMPv2 identified in this document
 is the same framework as was defined for SNMPv1 [9].  This
 administrative framework associates each message with a "community"
 as defined in [9].  Use of this administrative framework with SNMP
 Version 2 is commonly known as "Community-based SNMPv2 (SNMPv2C)."
 Specifically, Section 3.2.5 of [9] defines the concept of a
 community, and Section 4.1 of [9] defines the Elements of Procedure
 for generating and receiving messages.  The following updates apply:
 (1)  The types of access defined in Section 3.2.5 of [9] are updated
      by [1].
 (2)  The Elements of Procedure defined in Section 4.1 of [9] are
      updated with the additional requirement of incrementing the
      relevant statistics counter as defined in [6].

SNMPv2 Working Group Experimental [Page 4] RFC 1901 Introduction to Community-based SNMPv2 January 1996

 (3)  The requirement in the Elements of Procedure in Section 4.1 of
      [9] that the "the source transport address that a response
      message is sent from shall be identical to the destination
      transport address that the original request message was sent to"
      is deleted, i.e., the source transport address of a response
      message can be any transport address belonging to the agent.
 The form of a message is also taken from [9], with the exception that
 a new version number is used in the message "wrapper".  Use of a new
 version number is necessary because of SNMPv2's new PDU types [4],
 error codes [4], etc.  With this one change, the wrapper becomes:
  COMMUNITY-BASED-SNMPv2 DEFINITIONS ::= BEGIN
  1. - top-level message
      Message ::=
              SEQUENCE {
                   version
                      INTEGER {
                          version(1)  -- modified from RFC 1157
                      },
                  community           -- community name
                      OCTET STRING,
                  data                -- PDUs as defined in [4]
                      ANY
              }
      }
  END
 Note that with this administrative framework, the
 'authorizationError(16)' value defined for the error-status component
 of an SNMPv2 PDU [4] is unused.  It may, however, be used with future
 administrative frameworks.

4. Security Considerations

 Security issues are not discussed in this memo.

SNMPv2 Working Group Experimental [Page 5] RFC 1901 Introduction to Community-based SNMPv2 January 1996

5. Editor's Address

 Keith McCloghrie
 Cisco Systems, Inc.
 170 West Tasman Drive
 San Jose, CA  95134-1706
 US
 Phone: +1 408 526 5260
 EMail: kzm@cisco.com

6. Acknowledgements

 This document is the result of significant work by the four major
 contributors:
 Jeffrey D. Case (SNMP Research, case@snmp.com)
 Keith McCloghrie (Cisco Systems, kzm@cisco.com)
 Marshall T. Rose (Dover Beach Consulting, mrose@dbc.mtview.ca.us)
 Steven Waldbusser (International Network Services, stevew@uni.ins.com)
 In addition, the contributions of the SNMPv2 Working Group are
 acknowledged.  In particular, a special thanks is extended for the
 contributions of:
   Alexander I. Alten (Novell)
   Dave Arneson (Cabletron)
   Uri Blumenthal (IBM)
   Doug Book (Chipcom)
   Kim Curran (Bell-Northern Research)
   Jim Galvin (Trusted Information Systems)
   Maria Greene (Ascom Timeplex)
   Iain Hanson (Digital)
   Dave Harrington (Cabletron)
   Nguyen Hien (IBM)
   Jeff Johnson (Cisco Systems)
   Michael Kornegay (Object Quest)
   Deirdre Kostick (AT&T Bell Labs)
   David Levi (SNMP Research)
   Daniel Mahoney (Cabletron)
   Bob Natale (ACE*COMM)
   Brian O'Keefe (Hewlett Packard)
   Andrew Pearson (SNMP Research)
   Dave Perkins (Peer Networks)
   Randy Presuhn (Peer Networks)
   Aleksey Romanov (Quality Quorum)
   Shawn Routhier (Epilogue)
   Jon Saperia (BGS Systems)

SNMPv2 Working Group Experimental [Page 6] RFC 1901 Introduction to Community-based SNMPv2 January 1996

   Bob Stewart (Cisco Systems, bstewart@cisco.com), chair
   Kaj Tesink (Bellcore)
   Glenn Waters (Bell-Northern Research)
   Bert Wijnen (IBM)

7. References

[1] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and

   S. Waldbusser, "Structure of Management Information for Version 2
   of the Simple Network Management Protocol (SNMPv2)", RFC 1902,
   January 1996.

[2] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and

   S. Waldbusser, "Textual Conventions for Version 2 of the Simple
   Network Management Protocol (SNMPv2)", RFC 1903, January 1996.

[3] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and

   S. Waldbusser, "Conformance Statements for Version 2 of the Simple
   Network Management Protocol (SNMPv2)", RFC 1904, January 1996.

[4] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and

   S. Waldbusser, "Protocol Operations for Version 2 of the Simple
   Network Management Protocol (SNMPv2)", RFC 1905, January 1996.

[5] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and

   S. Waldbusser, "Transport Mappings for Version 2 of the Simple
   Network Management Protocol (SNMPv2)", RFC 1906, January 1996.

[6] SNMPv2 Working Group, 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.

[7] Rose, M., and K. McCloghrie, "Structure and Identification of

   Management Information for TCP/IP-based internets", STD 16, RFC
   1155, May 1990.

[8] Rose, M., and K. McCloghrie, "Concise MIB Definitions", STD 16,

   RFC 1212, March 1991.

[9] Case, J., Fedor, M., Schoffstall, M., Davin, J., "Simple Network

   Management Protocol", STD 15, RFC 1157, SNMP Research, Performance
   Systems International, MIT Laboratory for Computer Science, May
   1990.

SNMPv2 Working Group Experimental [Page 7] RFC 1901 Introduction to Community-based SNMPv2 January 1996

[10] SNMPv2 Working Group, 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.

[11] Information processing systems - Open Systems Interconnection -

   Specification of Abstract Syntax Notation One (ASN.1),
   International Organization for Standardization.  International
   Standard 8824, (December, 1987).

SNMPv2 Working Group Experimental [Page 8]

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