Network Working Group J. Case Request for Comments: 1452 SNMP Research, Inc. K. McCloghrie Hughes LAN Systems M. Rose Dover Beach Consulting, Inc. S. Waldbusser Carnegie Mellon University April 1993 Coexistence between version 1 and version 2 of the Internet-standard Network Management Framework Status of this Memo This RFC specifes an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. Table of Contents 1 Introduction .......................................... 2 2 Management Information ................................ 3 2.1 Object Definitions .................................. 3 2.2 Trap Definitions .................................... 6 2.3 Compliance Statements ............................... 7 2.4 Capabilities Statements ............................. 7 3 Protocol Operations ................................... 8 3.1 Proxy Agent Behavior ................................ 8 3.1.1 SNMPv2 -> SNMPv1 .................................. 8 3.1.2 SNMPv1 -> SNMPv2 .................................. 8 3.2 Bi-lingual Manager Behavior ......................... 10 4 Acknowledgements ...................................... 11 5 References ............................................ 15 6 Security Considerations ............................... 17 7 Authors' Addresses .................................... 17
1. 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) , and the original Internet-standard Network Management Framework (SNMPv1), which consists of these three documents: RFC 1155  which defines the Structure of Management Information (SMI), the mechanisms used for describing and naming objects for the purpose of management. RFC 1212  which defines a more concise description mechanism, which is wholly consistent with the SMI. RFC 1157  which defines the Simple Network Management Protocol (SNMP), the protocol used for network access to managed objects.
2. 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  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 , which defines concise notations for describing information modules, managed objects and notifications; Textual Conventions for SNMPv2 , which defines a concise notation for describing textual conventions, and also defines some initial conventions; and, Conformance Statements for SNMPv2 , which defines concise notation for describing compliance and capabilities statements. 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: 2.1. Object Definitions In general, conversion of a MIB module does not require the deprecation of the objects contained therein. Only if the semantics of an object truly changes should deprecation be performed. (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) For any descriptor which contains the hyphen character, the hyphen character is removed. (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 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 an enumerated INTEGER, the hyphen character is removed from any named-number labels which contain the hyphen character. (6) For any object with a SYNTAX clause value of Counter, the object must have the value of its SYNTAX clause changed to Counter32. (7) For any object with a SYNTAX clause value of Gauge, the object must have the value of its SYNTAX clause changed to Gauge32. (8) 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". If the value of the ACCESS clause is "write- only", then the value of the MAX-ACCESS clause is "read- write", and the DESCRIPTION clause notes that reading this object will result implementation-specific results. (9) 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".
(10) For all objects, if the value of the STATUS clause is "mandatory", the value must be replaced with "current". (11) For all objects, if the value of the STATUS clause is "optional", the value must be replaced with "obsolete". (12) For any object not containing a DESCRIPTION clause, the object must have a DESCRIPTION clause defined. (13) 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. (14) For any object with an INDEX clause that references an object with a syntax of NetworkAddress, the value of the STATUS clause of the both objects is changed to "obsolete". (15) 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. 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. Finally, when encountering common errors in SNMPv1 MIB modules: (1) For any object with a SYNTAX clause value of an enumerated INTEGER, if a named-number enumeration is present with a value of zero, the value of the STATUS clause of that object is changed to "obsolete". (2) For any non-columnar object that is instanced as if it were immediately subordinate to a conceptual row, the value of the STATUS clause of that object is changed to "obsolete". (3) For any conceptual row object that is not contained immediately subordinate to a conceptual table, the value of the STATUS clause of that object (and all subordinate objects) is changed to "obsolete". 2.2. 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. (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. 2.3. Compliance Statements 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. 2.4. Capabilities Statements In the current framework, the informational document  uses the MODULE-CONFORMANCE macro to describe an agent's capabilities with respect to 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.
3. Protocol Operations The SNMPv2 documents which deal with protocol operations are: Protocol Operations for SNMPv2 , which defines the syntax and semantics of the operations conveyed by the protocol; and, Transport Mappings for SNMPv2 , which defines how the protocol operations are carried over different transport services. The following section considers two areas: the proxy behavior between a SNMPv2 entity and a SNMPv1 agent; and, the behavior of "bi-lingual" protocol entities acting in a manager role. 3.1. 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. 3.1.1. 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. 3.1.2. SNMPv1 -> SNMPv2 When converting responses received from a SNMPv1 entity acting in an agent role into responses sent to a SNMPv2 entity acting 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', `badValue', or `readOnly', 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 , which takes its value from the timestamp field of the Trap-PDU; and, snmpTrapOID.0 , 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  is used. (For example, if the value of the generic-trap field is `coldStart', then the coldStart trap  is used.) Then, one new binding is appended onto the variable-bindings field: snmpTrapEnterpriseOID.0 , 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 4.2.6 of , 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.
3.2. 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.
4. Acknowledgements The comments of the SNMP version 2 working group are gratefully acknowledged: Beth Adams, Network Management Forum Steve Alexander, INTERACTIVE Systems Corporation David Arneson, Cabletron Systems Toshiya Asaba Fred Baker, ACC Jim Barnes, Xylogics, Inc. Brian Bataille Andy Bierman, SynOptics Communications, Inc. Uri Blumenthal, IBM Corporation Fred Bohle, Interlink Jack Brown Theodore Brunner, Bellcore Stephen F. Bush, GE Information Services Jeffrey D. Case, University of Tennessee, Knoxville John Chang, IBM Corporation Szusin Chen, Sun Microsystems Robert Ching Chris Chiotasso, Ungermann-Bass Bobby A. Clay, NASA/Boeing John Cooke, Chipcom Tracy Cox, Bellcore Juan Cruz, Datability, Inc. David Cullerot, Cabletron Systems Cathy Cunningham, Microcom James R. (Chuck) Davin, Bellcore Michael Davis, Clearpoint Mike Davison, FiberCom Cynthia DellaTorre, MITRE Taso N. Devetzis, Bellcore Manual Diaz, DAVID Systems, Inc. Jon Dreyer, Sun Microsystems David Engel, Optical Data Systems Mike Erlinger, Lexcel Roger Fajman, NIH Daniel Fauvarque, Sun Microsystems Karen Frisa, CMU Shari Galitzer, MITRE Shawn Gallagher, Digital Equipment Corporation Richard Graveman, Bellcore Maria Greene, Xyplex, Inc.
Michel Guittet, Apple Robert Gutierrez, NASA Bill Hagerty, Cabletron Systems Gary W. Haney, Martin Marietta Energy Systems Patrick Hanil, Nokia Telecommunications Matt Hecht, SNMP Research, Inc. Edward A. Heiner, Jr., Synernetics Inc. Susan E. Hicks, Martin Marietta Energy Systems Geral Holzhauer, Apple John Hopprich, DAVID Systems, Inc. Jeff Hughes, Hewlett-Packard Robin Iddon, Axon Networks, Inc. David Itusak Kevin M. Jackson, Concord Communications, Inc. Ole J. Jacobsen, Interop Company Ronald Jacoby, Silicon Graphics, Inc. Satish Joshi, SynOptics Communications, Inc. Frank Kastenholz, FTP Software Mark Kepke, Hewlett-Packard Ken Key, SNMP Research, Inc. Zbiginew Kielczewski, Eicon Jongyeoi Kim Andrew Knutsen, The Santa Cruz Operation Michael L. Kornegay, VisiSoft Deirdre C. Kostik, Bellcore Cheryl Krupczak, Georgia Tech Mark S. Lewis, Telebit David Lin David Lindemulder, AT&T/NCR Ben Lisowski, Sprint David Liu, Bell-Northern Research John Lunny, The Wollongong Group Robert C. Lushbaugh Martin, Marietta Energy Systems Michael Luufer, BBN Carl Madison, Star-Tek, Inc. Keith McCloghrie, Hughes LAN Systems Evan McGinnis, 3Com Corporation Bill McKenzie, IBM Corporation Donna McMaster, SynOptics Communications, Inc. John Medicke, IBM Corporation Doug Miller, Telebit Dave Minnich, FiberCom Mohammad Mirhakkak, MITRE Rohit Mital, Protools George Mouradian, AT&T Bell Labs
Patrick Mullaney, Cabletron Systems Dan Myers, 3Com Corporation Rina Nathaniel, Rad Network Devices Ltd. Hien V. Nguyen, Sprint Mo Nikain Tom Nisbet William B. Norton, MERIT Steve Onishi, Wellfleet Communications, Inc. David T. Perkins, SynOptics Communications, Inc. Carl Powell, BBN Ilan Raab, SynOptics Communications, Inc. Richard Ramons, AT&T Venkat D. Rangan, Metric Network Systems, Inc. Louise Reingold, Sprint Sam Roberts, Farallon Computing, Inc. Kary Robertson, Concord Communications, Inc. Dan Romascanu, Lannet Data Communications Ltd. Marshall T. Rose, Dover Beach Consulting, Inc. Shawn A. Routhier, Epilogue Technology Corporation Chris Rozman Asaf Rubissa, Fibronics Jon Saperia, Digital Equipment Corporation Michael Sapich Mike Scanlon, Interlan Sam Schaen, MITRE John Seligson, Ultra Network Technologies Paul A. Serice, Corporation for Open Systems Chris Shaw, Banyan Systems Timon Sloane Robert Snyder, Cisco Systems Joo Young Song Roy Spitier, Sprint Einar Stefferud, Network Management Associates John Stephens, Cayman Systems, Inc. Robert L. Stewart, Xyplex, Inc. (chair) Kaj Tesink, Bellcore Dean Throop, Data General Ahmet Tuncay, France Telecom-CNET Maurice Turcotte, Racal Datacom Warren Vik, INTERACTIVE Systems Corporation Yannis Viniotis Steven L. Waldbusser, Carnegie Mellon Universitty Timothy M. Walden, ACC Alice Wang, Sun Microsystems James Watt, Newbridge
Luanne Waul, Timeplex Donald E. Westlake III, Digital Equipment Corporation Gerry White Bert Wijnen, IBM Corporation Peter Wilson, 3Com Corporation Steven Wong, Digital Equipment Corporation Randy Worzella, IBM Corporation Daniel Woycke, MITRE Honda Wu Jeff Yarnell, Protools Chris Young, Cabletron Kiho Yum, 3Com Corporation
5. References  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Introduction to version 2 of the Internet-standard Network Management Framework", RFC 1441, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993.  Rose, M., and McCloghrie, K., "Structure and Identification of Management Information for TCP/IP-based internets", STD 16, RFC 1155, May 1990.  Rose, M., and McCloghrie, K., "Concise MIB Definitions", STD 16, RFC 1212, March 1991.  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.  Information processing systems - Open Systems Interconnection - Specification of Abstract Syntax Notation One (ASN.1), International Organization for Standardization. International Standard 8824, (December, 1987).  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Structure of Management Information for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1442, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993.  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Textual Conventions for version 2 of the the Simple Network Management Protocol (SNMPv2)", RFC 1443, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993.  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Conformance Statements for version 2 of the the Simple Network Management Protocol (SNMPv2)", RFC 1444, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993.
 McCloghrie, K., and Rose, M., "A Convention for Describing SNMP-based Agents", RFC 1303, Hughes LAN Systems, Dover Beach Consulting, Inc., February 1992.  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Protocol Operations for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1448, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993.  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Transport Mappings for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1449, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993.  McCloghrie, K., and Rose, M., "Management Information Base for Network Management of TCP/IP-based internets: MIB-II", STD 17, RFC 1213, March 1991.  Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Management Information Base for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1450, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993.
6. Security Considerations Security issues are not discussed in this memo. 7. Authors' Addresses Jeffrey D. Case SNMP Research, Inc. 3001 Kimberlin Heights Rd. Knoxville, TN 37920-9716 US Phone: +1 615 573 1434 Email: firstname.lastname@example.org Keith McCloghrie Hughes LAN Systems 1225 Charleston Road Mountain View, CA 94043 US Phone: +1 415 966 7934 Email: email@example.com Marshall T. Rose Dover Beach Consulting, Inc. 420 Whisman Court Mountain View, CA 94043-2186 US Phone: +1 415 968 1052 Email: firstname.lastname@example.org Steven Waldbusser Carnegie Mellon University 4910 Forbes Ave Pittsburgh, PA 15213 US Phone: +1 412 268 6628 Email: email@example.com