Network Working Group M. Rose, Editor
Request for Comments: 1215 Performance Systems International
March 1991
This memo suggests a straight-forward approach towards defining traps used with the SNMP. Readers should note that the use of traps in the Internet-standard network management framework is controversial. As such, this memo is being put forward for information purposes. Network management practitioners who employ traps are encouraged to make use of this document. Practitioners who do not employ traps can safely ignore this document.
This memo provides information for the Internet community. It does not specify any standard. Distribution of this memo is unlimited.
1. Historical Perspective
2. Defining Traps
2.1 Mapping of the TRAP-TYPE macro
2.1.1 Mapping of the ENTERPRISE clause
2.1.2 Mapping of the VARIABLES clause
2.1.3 Mapping of the DESCRIPTION clause
2.1.4 Mapping of the REFERENCE clause
2.1.5 Mapping of the TRAP-TYPE value
2.2 Usage Examples
2.2.1 Enterprise-specific Trap
2.2.2 Generic-Traps for use with the SNMP
3. Acknowledgements
4. References
5. Security Considerations
6. Author's Address
As reported in RFC 1052, IAB Recommendations for the Development of Internet Network Management Standards [1], a two-prong strategy for network management of TCP/IP-based internets was undertaken. In the short-term, the Simple Network Management Protocol (SNMP), defined in RFC 1067, was to be used to manage nodes in the Internet community. In the long-term, the use of the OSI network management framework was be examined. Two documents were produced to define the management
information: RFC 1065, which defined the Structure of Management Information (SMI), and RFC 1066, which defined the Management Information Base (MIB). Both of these documents were designed so as to be compatible with both the SNMP and the OSI network management framework.
This strategy was quite successful in the short-term: Internet-based network management technology was fielded, by both the research and commercial communities, within a few months. As a result of this, portions of the Internet community became network manageable in a timely fashion.
As reported in RFC 1109, Report of the Second Ad Hoc Network Management Review Group [2], the requirements of the SNMP and the OSI network management frameworks were more different than anticipated. As such, the requirement for compatibility between the SMI/MIB and both frameworks was suspended. This action permitted the operational network management framework, based on the SNMP, to respond to new operational needs in the Internet community by producing MIB-II.
In May of 1990, the core documents were elevated to "Standard
Protocols" with "Recommended" status. As such, the Internet-standard
network management framework consists of: Structure and
Identification of Management Information for TCP/IP-based internets,
RFC 1155 [3], which describes how managed objects contained in the
MIB are defined; Management Information Base for Network Management
of TCP/IP-based internets, which describes the managed objects
contained in the MIB, RFC 1156 [4]; and, the Simple Network
Management Protocol, RFC 1157 [5], which defines the protocol used to
manage these objects.
Due to its initial requirement to be protocol-independent, the Internet-standard SMI does not provide a means for defining traps. Instead, the SNMP defines a few standardized traps and provides a means for management enterprises to transmit enterprise-specific traps.
However, with the introduction of experimental MIBs, some of which have a need to define experiment-specific traps, a convenient means of defining traps is desirable. The TRAP-TYPE macro is suggested for this purpose:
IMPORTS
ObjectName
FROM RFC1155-SMI;
TRAP-TYPE MACRO ::=
BEGIN
TYPE NOTATION ::= "ENTERPRISE" value
(enterprise OBJECT IDENTIFIER)
VarPart
DescrPart
ReferPart
VALUE NOTATION ::= value (VALUE INTEGER)
VarPart ::=
"VARIABLES" "{" VarTypes "}"
| empty
VarTypes ::=
VarType | VarTypes "," VarType
VarType ::=
value (vartype ObjectName)
DescrPart ::=
"DESCRIPTION" value (description DisplayString)
| empty
ReferPart ::=
"REFERENCE" value (reference DisplayString)
| empty
END
It must be emphasized however, that the use of traps is STRONGLY discouraged in the Internet-standard Network Management Framework. The TRAP-TYPE macro is intended to allow concise definitions of existing traps, not to spur the definition of new traps.
It should be noted that the expansion of the TRAP-TYPE macro is something which conceptually happens during implementation and not during run-time.
The ENTERPRISE clause, which must be present, defines the management enterprise under whose registration authority this trap is defined (for a discussion on delegation of registration authority, see the SMI [3]). This value is placed inside the enterprise field of the SNMP Trap-PDU.
By convention, if the value of the ENTERPRISE clause is
snmp OBJECT IDENTIFIER ::= { mib-2 11 }
as defined in MIB-II [7], then instead of using this value, the value of sysObjectID is placed in the enterprise field of the SNMP Trap- PDU. This provides a simple means of using the TRAP-TYPE macro to represent the existing standard SNMP traps; it is not intended to provide a means to define additional standard SNMP traps.
The VARIABLES clause, which need not be present, defines the ordered sequence of MIB objects which are contained within every instance of the trap type. Each variable is placed, in order, inside the variable-bindings field of the SNMP Trap-PDU. Note that at the option of the agent, additional variables may follow in the variable-bindings field.
However, if the value of the ENTERPRISE clause is
snmp OBJECT IDENTIFIER ::= { mib-2 11 }
as defined in MIB-II [7], then the introduction of additional variables must not result in the serialized SNMP Message being larger than 484 octets.
The DESCRIPTION clause, which need not be present, contains a textual definition of the trap type. Note that in order to conform to the ASN.1 syntax, the entire value of this clause must be enclosed in double quotation marks, although the value may be multi-line.
Further, note that if the MIB module does not contain a textual description of the trap elsewhere then the DESCRIPTION clause must be present.
The REFERENCE clause, which need not be present, contains a textual cross-reference to a trap, event, or alarm, defined in some other MIB module. This is useful when de-osifying a MIB produced by some other organization.
The value of an invocation of the TRAP-TYPE macro is the (integer) number which is uniquely assigned to the trap by the registration authority indicated by the ENTERPRISE clause. This value is placed
inside the specific-trap field of the SNMP Trap-PDU, and the generic-trap field is set to "enterpriseSpecific(6)".
By convention, if the value of the ENTERPRISE clause is
snmp OBJECT IDENTIFIER ::= { mib-2 11 }
as defined in MIB-II [7], then the value of an invocation of the TRAP-TYPE macro is placed inside the generic-trap field of the SNMP Trap-PDU, and the specific-trap field is set to 0. This provides a simple means of using the TRAP-TYPE macro to represent the existing standard SNMP traps; it is not intended to provide a means to define additional standard SNMP traps.
Consider a simple example of an enterprise-specific trap that is sent when a communication link failure is encountered:
myEnterprise OBJECT IDENTIFIER ::= { enterprises 9999 }
myLinkDown TRAP-TYPE
ENTERPRISE myEnterprise
VARIABLES { ifIndex }
DESCRIPTION
"A myLinkDown trap signifies that the sending
SNMP application entity recognizes a failure
in one of the communications links represented
in the agent's configuration."
::= 2
Consider how the standard SNMP traps might be defined:
coldStart TRAP-TYPE
ENTERPRISE snmp
DESCRIPTION
"A coldStart trap signifies that the sending
protocol entity is reinitializing itself such
that the agent's configuration or the rotocol
entity implementation may be altered."
::= 0
warmStart TRAP-TYPE
ENTERPRISE snmp
DESCRIPTION
"A warmStart trap signifies that the sending
protocol entity is reinitializing itself such
that neither the agent configuration nor the
protocol entity implementation is altered."
::= 1
linkDown TRAP-TYPE
ENTERPRISE snmp
VARIABLES { ifIndex }
DESCRIPTION
"A linkDown trap signifies that the sending
protocol entity recognizes a failure in one of
the communication links represented in the
agent's configuration."
::= 2
linkUp TRAP-TYPE
ENTERPRISE snmp
VARIABLES { ifIndex }
DESCRIPTION
"A linkUp trap signifies that the sending
protocol entity recognizes that one of the
communication links represented in the agent's
configuration has come up."
::= 3
authenticationFailure TRAP-TYPE
ENTERPRISE snmp
DESCRIPTION
"An authenticationFailure trap signifies that
the sending protocol entity is the addressee
of a protocol message that is not properly
authenticated. While implementations of the
SNMP must be capable of generating this trap,
they must also be capable of suppressing the
emission of such traps via an implementation-
specific mechanism."
::= 4
egpNeighborLoss TRAP-TYPE
ENTERPRISE snmp
VARIABLES { egpNeighAddr }
DESCRIPTION
"An egpNeighborLoss trap signifies that an EGP
neighbor for whom the sending protocol entity
was an EGP peer has been marked down and the
peer relationship no longer obtains."
::= 5
This document was produced by the SNMP Working Group:
Anne Ambler, Spider
Karl Auerbach, Sun
Fred Baker, ACC
Ken Brinkerhoff
Ron Broersma, NOSC
Jack Brown, US Army
Theodore Brunner, Bellcore
Jeffrey Buffum, HP
John Burress, Wellfleet
Jeffrey D. Case, University of Tennessee at Knoxville
Chris Chiptasso, Spartacus
Paul Ciarfella, DEC
Bob Collet
John Cook, Chipcom
Tracy Cox, Bellcore
James R. Davin, MIT-LCS
Eric Decker, cisco
Kurt Dobbins, Cabletron
Nadya El-Afandi, Network Systems
Gary Ellis, HP
Fred Engle
Mike Erlinger
Mark S. Fedor, PSI
Richard Fox, Synoptics
Karen Frisa, CMU
Chris Gunner, DEC
Fred Harris, University of Tennessee at Knoxville
Ken Hibbard, Xylogics
Ole Jacobsen, Interop
Ken Jones
Satish Joshi, Synoptics
Frank Kastenholz, Racal-Interlan
Shimshon Kaufman, Spartacus
Ken Key, University of Tennessee at Knoxville
Jim Kinder, Fibercom
Alex Koifman, BBN
Christopher Kolb, PSI
Cheryl Krupczak, NCR
Paul Langille, DEC
Peter Lin, Vitalink
John Lunny, TWG
Carl Malamud
Randy Mayhew, University of Tennessee at Knoxville
Keith McCloghrie, Hughes LAN Systems
Donna McMaster, David Systems
Lynn Monsanto, Sun
Dave Perkins, 3COM
Jim Reinstedler, Ungerman Bass
Anil Rijsinghani, DEC
Kathy Rinehart, Arnold AFB
Kary Robertson
Marshall T. Rose, PSI (chair)
[1] Cerf, V., "IAB Recommendations for the Development of Internet Network Management Standards", RFC 1052, NRI, April 1988.
[2] Cerf, V., "Report of the Second Ad Hoc Network Management Review Group", RFC 1109, NRI, August 1989.
[3] Rose M., and K. McCloghrie, "Structure and Identification of Management Information for TCP/IP-based internets", RFC 1155, Performance Systems International, Hughes LAN Systems, May 1990.
[4] McCloghrie K., and M. Rose, "Management Information Base for Network Management of TCP/IP-based internets", RFC 1156, Hughes LAN Systems, Performance Systems International, May 1990.
[5] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple Network Management Protocol", RFC 1157, SNMP Research, Performance Systems International, Performance Systems International, MIT Laboratory for Computer Science, 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] Rose M., Editor, "Management Information Base for Network Management of TCP/IP-based internets: MIB-II", RFC 1213, Performance Systems International, March 1991.
Security issues are not discussed in this memo.
Marshall T. Rose
Performance Systems International
5201 Great America Parkway
Suite 3106
Santa Clara, CA 95054
Phone: +1 408 562 6222
EMail: mrose@psi.com