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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