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Internet Draft           Introduction to SNMPv2             October 1995


                    Introduction to Version 2 of the
             Internet-standard Network Management Framework

                            18 October 1995                               |

                   draft-ietf-snmpv2-intro-ds-06.txt                      |


                            Keith McCloghrie
                                 Editor
                          Cisco Systems, Inc.
                             kzm@cisco.com





Status of this Memo

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

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time.  It is inappropriate to use Internet- Drafts as reference material
or to cite them other than as ``work in progress.''

To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet- Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe),
ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).

















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Internet Draft           Introduction to SNMPv2             October 1995


1.  Introduction

The purpose of this document is to provide an overview of version 2 of
the Internet-standard Network Management Framework, termed the SNMP
version 2 framework (SNMPv2).  The SNMPv2 framework is fully described
in [6,7,8,9,10,11].  This framework is derived from the original
Internet-standard Network Management Framework (SNMPv1), which consists
of these three documents:

     RFC 1155 [1] which defines the Structure of Management Information
     (SMI), the mechanisms used for describing and naming objects for
     the purpose of management.

     RFC 1212 [2] which defines a more concise description mechanism,
     which is wholly consistent with the SMI.

     RFC 1157 [3] 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 [4].






























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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) [5].  It is the purpose of the Structure of
Management Information for SNMPv2 document [6] 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,
     NOTIFICATION-TYPE, is used to concisely convey the syntax and
     semantics of a notification.










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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 [7] 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.  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).

It is the purpose of the Protocol Operations for SNMPv2 document [8] to
define the operations of the protocol with respect to the sending and
receiving of the PDUs.


2.4.  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 [9] 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.








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2.5.  Protocol Instrumentation

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


2.6.  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 [11]
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.


2.7.  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 [3].                         |
This administrative framework associates each message with a "community"  |
as defined in [3].  Use of this administrative framework with SNMP        |
Version 2 is commonly known as "Community-based SNMPv2 (SNMPv2C)."        |

Specifically, Section 3.2.5 of [3] defines the concept of a community,
and Section 4.1 of [3] defines the Elements of Procedure for generating
and receiving messages.  The following updates apply:




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(1)  The types of access defined in Section 3.2.5 of [3] are updated by
     [6].

(2)  The Elements of Procedure defined in Section 4.1 of [3] are updated
     with the additional requirement of incrementing the relevant
     statistics counter as defined in [10].

(3)  The requirement in the Elements of Procedure in Section 4.1 of [3]
     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 [3], 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 [8], error
codes [8], etc.  With this one change, the wrapper becomes:

    COMMUNITY-BASED-SNMPv2 DEFINITIONS ::= BEGIN

    -- top-level message

        Message ::=
                SEQUENCE {
                     version
                        INTEGER {
                            version(1)  -- modified from RFC 1157
                        },

                    community           -- community name
                        OCTET STRING,

                    data                -- PDUs as defined in [8]
                        ANY
                }
        }

    END

Note that with this administrative framework, the
'authorizationError(16)' value defined for the error-status component of
an SNMPv2 PDU [8] is unused.  It may, however, be used with future
administrative frameworks.






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3.  Acknowledgements

This document is the result of significant work by the four major
contributors:

     Jeffrey Case (SNMP Research, case@snmp.com)
     Keith McCloghrie (Cisco Systems, kzm@cisco.com)
     Marshall 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)
     Bob Stewart (Cisco Systems, bstewart@cisco.com), chair
     Kaj Tesink (Bellcore)
     Glenn Waters (Bell-Northern Research)
     Bert Wijnen (IBM)









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4.  References

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

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

[3]  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.

[4]  McCloghrie, K., Editor, "Coexistence between Version 1 and Version
     2 of the Internet-standard Network Management Framework", Internet
     Draft, Cisco Systems, September 1995.

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

[6]  McCloghrie, K., Editor, "Structure of Management Information for
     Version 2 of the Simple Network Management Protocol (SNMPv2)",
     Internet Draft, Cisco Systems, September 1995.

[7]  McCloghrie, K., Editor, "Textual Conventions for Version 2 of the
     Simple Network Management Protocol (SNMPv2)", Internet Draft, Cisco
     Systems, September 1995.

[8]  McCloghrie, K., Editor, "Protocol Operations for Version 2 of the
     Simple Network Management Protocol (SNMPv2)", Internet Draft, Cisco
     Systems, September 1995.

[9]  McCloghrie, K., Editor, "Transport Mappings for Version 2 of the
     Simple Network Management Protocol (SNMPv2)", Internet Draft, Cisco
     Systems, September 1995.

[10] McCloghrie, K., Editor, "Management Information Base for Version 2
     of the Simple Network Management Protocol (SNMPv2)", Internet
     Draft, Cisco Systems, September 1995.

[11] McCloghrie, K., Editor, "Conformance Statements for Version 2 of
     the Simple Network Management Protocol (SNMPv2)", Internet Draft,





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     Cisco Systems, September 1995.

















































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5.  Security Considerations

Security issues are not discussed in this memo.


6.  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



































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Internet Draft           Introduction to SNMPv2             October 1995


Table of Contents


1 Introduction ....................................................    2
2 Components of the SNMPv2 Framework ..............................    3
2.1 Structure of Management Information ...........................    3
2.2 Textual Conventions ...........................................    4
2.3 Protocol Operations ...........................................    4
2.4 Transport Mappings ............................................    4
2.5 Protocol Instrumentation ......................................    5
2.6 Conformance Statements ........................................    5
2.7 Administrative Framework ......................................    5
3 Acknowledgements ................................................    7
4 References ......................................................    8
5 Security Considerations .........................................   10
6 Editor's Address ................................................   10


































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