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          Draft             SNMPv1/SNMPv2 Coexistence             Oct 92


                Coexistence between version 1 and version 2 of the
                        Network Management Framework

                             Thu Nov 12 08:51:15 1992                     |


                                 Jeffrey D. Case
                               SNMP Research, Inc.
                        University of Tennessee, Knoxville
                                 case@cs.utk.edu


                                 Keith McCloghrie
                                Hughes LAN Systems
                                   kzm@hls.com


                                 Marshall T. Rose
                           Dover Beach Consulting, Inc.
                              mrose@dbc.mtview.ca.us


                               Steven L. Waldbusser
                            Carnegie Mellon University
                            waldbusser@andrew.cmu.edu






          1.  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 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 a "work in progress".







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          2.  Introduction

          The purpose of this document is to describe coexistence         |
          between version 2 of the Internet-standard Network Management   |
          Framework, termed the SNMP version 2 framework (SNMPv2) [1],    |
          and the original Internet-standard Network Management           |
          Framework (SNMPv1):                                             |

               RFC 1155 [2] which defines the Structure of Management     |
               Information (SMI),                                         |
               the mechanisms used for describing and naming objects for
               the purpose of management.  RFC 1212 [3] defines a more    |
               concise description mechanism,                             |
               which is wholly consistent with the SMI.

               RFC 1213 [4] which defines the TCP/IP Management           |
               Information Base 2 (MIB-II),                               |
               the core set of managed objects for the Internet suite of
               protocols.

               RFC 1157 [5] which defines the Simple Network Management   |
               Protocol (SNMP),                                           |
               the protocol used for network access to managed objects.



























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          3.  Management Information                                      -

          The SNMPv2 approach towards describing collections of managed
          objects is nearly a proper superset of the approach defined in
          the Internet-standard Network Management Framework.  For
          example, both approaches use ASN.1 [6] as the basis for a
          formal descriptive notation.  Indeed, one might note that the
          SNMPv2 approach largely codifies the existing practice for
          defining MIB modules, based on extensive experience with the
          current framework.

          The SNMPv2 documents which deal with information modules are:

               Structure of Management Information for SNMPv2 [7], which
               defines concise notations for describing managed objects,
               compliance statements for MIB modules, and capabilities
               statements for agent implementations; and,

               Textual Conventions for SNMPv2 [8], which defines a
               concise notation for describing textual conventions, and
               also defines some initial conventions.

          The following sections consider the three areas: MIB modules,
          compliance statements, and capabilities statements.

          MIB modules defined using the current framework may continue
          to be used with the SNMPv2 protocol.  However, for the MIB
          modules to conform to the SNMPv2 framework, the following
          changes are required:


          3.1.  Object Definitions

          (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 or EXPORTs statement.

          (3)  Object groups, which were informally defined (using ASN.1
               comments), must be defined using the OBJECT-GROUP macro.

          (4)  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





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               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.

          (5)  For any object with a SYNTAX clause value of Counter, the
               object must have the value of its SYNTAX clause changed
               to Counter32.

          (6)  For any object with a SYNTAX clause value of Gauge, the
               object must have the value of its SYNTAX clause changed
               to Gauge32.

          (7)  For all objects, the ACCESS clause must be replaced by a
               MAX-ACCESS clause.  The value of the MAX-ACCESS clause is
               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, will have a MAX-ACCESS clause of "read-
               create".

          (8)  For any columnar object which is used solely for instance
               identification in a conceptual row, the object must have
               the value of its MAX-ACCESS clause set to "not-
               accessible", unless all columnar objects of the
               conceptual row are used for instance identification, in
               which case, the MAX-ACCESS clause for one of them must be
               something other than "not-accessible".

          (9)  For all objects, if the value of the STATUS clause is
               "mandatory", the value must be replaced with "current".

          (10) For any object not containing a DESCRIPTION clause, the
               object must have a DESCRIPTION clause defined.

          (11) 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.

          (12) For any object containing a DEFVAL clause with an OBJECT
               IDENTIFIER value which is expressed as a collection of
               sub-identifiers, change the value to reference a single
               ASN.1 identifier.







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          Other changes are desirable, but not necessary:

          (1)  Creation and deletion of conceptual rows is inconsistent
               using the current framework.  The SNMPv2 framework
               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 it may be worthwhile to deprecate the objects
               relating to those tables and replacing them with objects
               defined using the new approach.

          (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), one might
               consider defining the bounds for the size of the object.

          (3)  For all textual conventions informally defined in the MIB
               module, one might consider redefining those conventions
               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, one might consider adding a UNITS clause
               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, one might consider
               using an AUGMENTS clause in place of the INDEX clause for
               the object corresponding to the conceptual row which is
               an extension.


          3.2.  Trap Definitions

          If a MIB module is changed to conform to the SNMPv2 framework,
          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.







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          (2)  The ENTERPRISES clause must be removed.

          (3)  The VARIABLES clause must be renamed to the OBJECTS
               clause.

          (4)  The STATUS clause must be added.

          (5)  The value of an invocation of the NOTIFICATION-TYPE macro
               is an OBJECT IDENTIFIER, not an INTEGER, and must be
               changed accordingly.


          3.3.  Compliance Definitions

          For those information modules which are "standard", a
          corresponding invocation of the MODULE-COMPLIANCE macro 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 must be
          removed.  Typically this editing can occur when the
          information module undergoes review.


          3.4.  Capabilities Definitions

          In the current framework, the informational document [9] uses
          the MODULE-CONFORMANCE macro to describe an agent's
          capabilities in comparison with one or more MIB modules.
          Converting such a description for use with the SNMPv2
          framework requires these changes:

          (1)  Use the macro name AGENT-CAPABILITIES instead of MODULE-
               CONFORMANCE.

          (2)  The STATUS clause must be added.

          (3)  For all occurrences of the CREATION-REQUIRES clause, note
               the slight change in semantics, and omit this clause if
               appropriate.











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          4.  Protocol Operations

          The SNMPv2 documents which deal with protocol operations are:

               Protocol Operations for SNMPv2 [10], which defines the
               syntax and semantics of the operations conveyed by the
               protocol; and,

               Transport Mappings for SNMPv2 [11], which defines how the
               protocol operations are carried over different transport
               services.

          The following section considers two areas: the proxy behavior
          between an SNMPv2 entity and an SNMPv1 agent; and, the
          behavior of "bi-lingual" protocol entities acting in a manager
          role.


          4.1.  Proxy Agent Behavior

          To achieve coexistence at the protocol-level, a proxy
          mechanism may be used.  A SNMPv2 entity acting in an agent
          role may be implemented and configured to act in the role of a
          proxy agent.


          4.1.1.  SNMPv2 -> SNMPv1

          When converting requests from a SNMPv2 entity acting in a
          manager role into requests sent to a SNMPv1 entity acting in
          an agent role:

          (1)  If a GetRequest-PDU, GetNextRequest-PDU, or SetRequest-
               PDU is received, then it is passed unaltered by the proxy
               agent.

          (2)  If a GetBulkRequest-PDU is received, the proxy agent sets
               the non-repeaters and max-repetitions fields to zero, and
               sets the tag of the PDU to GetNextRequest-PDU.


          4.1.2.  SNMPv1 -> SNMPv2

          When converting responses received from a SNMPv1 entity acting
          in an agent role into responses sent to a SNMPv2 entity acting





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          in a manager role:

          (1)  If a GetResponse-PDU is received, then it is passed
               unaltered by the proxy agent.  Note that even though a
               SNMPv2 entity will never generate a Response-PDU with a
               error-status field having a value of `noSuchName', or
               `badValue', the proxy agent must not change this field.
               This allows the SNMPv2 entity acting in a manager role to
               interpret the response correctly.

               If a GetResponse-PDU is received with an error-status
               field having a value of `tooBig', the proxy agent will
               remove the contents of the variable-bindings field before
               propagating the response.  Note that even though a SNMPv2
               entity will never generate a `tooBig' in response to a
               GetBulkRequestPDU, the proxy agent must propagate such a
               response.

          (2)  If a Trap-PDU is received, then it is mapped into a
               SNMPv2-Trap-PDU.  This is done by prepending onto the
               variable-bindings field two new bindings: sysUpTime.0
               [4], which takes its value from the timestamp field of
               the Trap-PDU; and, snmpTrapOID.0 [12], which is
               calculated thusly: if the value of generic-trap field is
               `enterpriseSpecific', then the value used is the
               concatenation of the enterprise field from the Trap-PDU
               with two additional sub-identifiers, `0', and the value
               of the specific-trap field; otherwise, the value of the
               corresponding trap defined in [12] is used.  (For
               example, if the value of the generic-trap field is
               `coldStart', then the coldStart trap [12] is used.) Then,
               one new binding is appended onto the variable-bindings
               field: snmpTrapEnterpriseOID.0 [12], which takes its
               value from the enterprise field of the Trap-PDU.  To
               determine the destinations for the SNMPv2-Trap-PDU, the
               proxy agent applies the procedures defined in Section 8.5
               of [7], with the exception that no check is made to see
               if the instances associated with this trap are present in
               the proxy agent's view.











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          4.2.  Bi-lingual Manager Behavior

          To achieve coexistence at the protocol-level, a protocol
          entity acting in a manager role might support both SNMPv1 and
          SNMPv2.  When a management application needs to contact a
          protocol entity acting in an agent role, the entity acting in
          a manager role consults a local database to select the correct
          management protocol to use.

          In order to provide transparency to management applications,
          the entity acting in a manager role must map operations as if
          it were acting as a proxy agent.






































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          5.  Acknowledgements

          The comments of the SNMP Version 2 working group are
          gratefully acknowledged:

               Steve Alexander, Interactive Systems
               Uri Blumenthal, International Business Machines
               Jeffrey D. Case, SNMP Research, Inc.
               Tracy Cox, Bellcore
               James R. (Chuck) Davin, Bellcore
               Mike Davison, FiberCom
               Taso N. Devetzis, Bellcore
               Gary W. Haney, Martin Marietta Energy Systems
               Matt Hecht, SNMP Research, Inc.
               Susan E. Hicks, Martin Marietta Energy Systems
               Satish Joshi, SynOptics
               Mark Kepke, Hewlett-Packard
               Ken Key, SNMP Research, Inc.
               Michael Kornegay, Visisoft
               Deidre C. Kostick, Bellcore
               Cheryl Krupczak, Georgia Tech
               Robert C. Lushbaugh, Martin Marietta Energy Systems
               Keith McCloghrie, Hughes LAN Systems
               Dave Minnich, FiberCom
               Dave Perkins, SynOptics
               Marshall T. Rose, Dover Beach Consulting, Inc.
               Shawn A. Routhier, Epilogue Technology
               Jon Saperia, Digital Equipment Corporation
               Bob Stewart, Xyplex (chair)
               Robert Synder, Cisco Systems
               Maurice Turcotte, Racal Datacom
               Steven L. Waldbusser, Carnegie Mellon University
               Bert Wijnen, International Business Machines
               Peter Wilson, 3Com
               Steven Wong, Digital Equipment Corporation
               Chris Young, Cabletron
               Kiho Yum, 3Com













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          6.  References

          [1]  J.D. Case, K. McCloghrie, M.T. Rose, S.L. Waldbusser,
               Introduction to version 2 of the Internet-standard
               Network Management Framework, Internet-Draft, (October 7,
               1992).

          [2]  M.T. Rose and K. McCloghrie, Structure and Identification
               of Management Information for TCP/IP-based internets.
               Request for Comments 1155, (May, 1990).

          [3]  M.T. Rose and K. McCloghrie, Concise MIB Definitions.
               Request for Comments 1212, (March, 1991).

          [4]  K. McCloghrie and M.T. Rose, Management Information Base
               for Network Management of TCP/IP-based internets: MIB-II.
               Request for Comments 1213, (March, 1991).

          [5]  J.D. Case, M.S. Fedor, M.L. Schoffstall, and J.R. Davin,
               Simple Network Management Protocol.  Request for Comments
               1157, (May, 1990).

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

          [7]  J.D. Case, K. McCloghrie, M.T. Rose, S.L. Waldbusser,
               Structure of Management Information for version 2 of the
               Simple Network Management Protocol, Internet-Draft,
               (October 7, 1992).

          [8]  J.D. Case, K. McCloghrie, M.T. Rose, S.L. Waldbusser,
               Textual Conventions for version 2 of the the Simple
               Network Management Protocol (SNMPv2), Internet-Draft,
               (October 7, 1992).

          [9]  K. McCloghrie, M.T. Rose, A Convention for Describing
               SNMP-based Agents.  Request for Comments 1303, (February,
               1992).

          [10] J.D. Case, K. McCloghrie, M.T. Rose, S.L. Waldbusser,
               Protocol Operations for version 2 of the Simple Network
               Management Protocol (SNMPv2), Internet-Draft, (October 7,





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               1992).

          [11] J.D. Case, K. McCloghrie, M.T. Rose, S.L. Waldbusser,
               Transport Mappings for version 2 of the Simple Network
               Management Protocol (SNMPv2), Internet-Draft, (October 7,
               1992).

          [12] J.D. Case, K. McCloghrie, M.T. Rose, S.L. Waldbusser,
               Management Information Base for version 2 of the Simple
               Network Management Protocol (SNMPv2), Internet-Draft,
               (October 7, 1992).

          [13] J.R. Davin, J.M. Galvin, K. McCloghrie, SNMP
               Administrative Model.  Request for Comments 1351, (July,
               1992).

          [14] J.M. Galvin, K. McCloghrie, J.R. Davin, SNMP Security
               Protocols.  Request for Comments 1352, (July, 1992).

          [15] K. McCloghrie, J.R. Davin, J.M. Galvin, Definitions of
               Managed Objects for Administration of SNMP Parties.
               Request for Comments 1353, (July, 1992).




























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          Table of Contents


          1 Status of this Memo ...................................    1
          2 Introduction ..........................................    2
          3 Management Information ................................    3
          3.1 Object Definitions ..................................    3
          3.2 Trap Definitions ....................................    5
          3.3 Compliance Definitions ..............................    6
          3.4 Capabilities Definitions ............................    6
          4 Protocol Operations ...................................    7
          4.1 Proxy Agent Behavior ................................    7
          4.1.1 SNMPv2 -> SNMPv1 ..................................    7
          4.1.2 SNMPv1 -> SNMPv2 ..................................    7
          4.2 Bi-lingual Manager Behavior .........................    9
          5 Acknowledgements ......................................   10
          6 References ............................................   11

































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