Protocol Operations for Version 2 of the Simple Network Management Protocol (SNMPv2)
RFC 1905

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Network Working Group                               SNMPv2 Working Group
Request for Comments: 1905                                       J. Case
Obsoletes: 1448                                      SNMP Research, Inc.
Category: Standards Track                                  K. McCloghrie
                                                     Cisco Systems, Inc.
                                                                 M. Rose
                                            Dover Beach Consulting, Inc.
                                                           S. Waldbusser
                                          International Network Services
                                                            January 1996

                          Protocol Operations
                          for Version 2 of the
              Simple Network Management Protocol (SNMPv2)

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.

1.  Introduction

   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.

   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) [1], termed the Structure of
   Management Information (SMI) [2].

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RFC 1905             Protocol Operations for SNMPv2         January 1996

   The management protocol, version 2 of the Simple Network 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).  The form and meaning of the
   "wrapper" is determined by an administrative framework which defines
   both authentication and authorization policies.

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

1.1.  A Note on Terminology

   For the purpose of exposition, the original Internet-standard Network
   Management Framework, as described in RFCs 1155 (STD 16), 1157 (STD
   15), and 1212 (STD 16), is termed the SNMP version 1 framework
   (SNMPv1).  The current framework is termed the SNMP version 2
   framework (SNMPv2).

2.  Overview

2.1.  Roles of Protocol Entities

   A SNMPv2 entity may operate in a manager role or an agent role.

   A SNMPv2 entity acts in an agent role when it performs SNMPv2
   management operations in response to received SNMPv2 protocol
   messages (other than an inform notification) or when it sends trap
   notifications.

   A SNMPv2 entity acts in a manager role when it initiates SNMPv2
   management operations by the generation of SNMPv2 protocol messages
   or when it performs SNMPv2 management operations in response to
   received trap or inform notifications.

   A SNMPv2 entity may support either or both roles, as dictated by its
   implementation and configuration.  Further, a SNMPv2 entity can also
   act in the role of a proxy agent, in which it appears to be acting in
   an agent role, but satisfies management requests by acting in a
   manager role with a remote entity.

2.2.  Management Information

   The term, variable, refers to an instance of a non-aggregate object
   type defined according to the conventions set forth in the SMI [2] or
   the textual conventions based on the SMI [3].  The term, variable
   binding, normally refers to the pairing of the name of a variable and

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RFC 1905             Protocol Operations for SNMPv2         January 1996

   its associated value.  However, if certain kinds of exceptional
   conditions occur during processing of a retrieval request, a variable