Network Working Group J. Schoenwaelder
Internet-Draft TU Braunschweig
Expires April 2000 22. October 1999
Operation-Types for SMIv2
<draft-irtf-nmrg-smi-ops-00.txt>
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Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Abstract
This document defines an extension for the SMIv2 which allows to
define operations. Operations can among other things be used to
define install/remove operations on conceptual MIB tables. This can
result in simpler and more efficient implementations of configuration
management systems.
Warning
This document has not been written in order to specify a solution.
Instead, this document has been written to stimulate (controversial)
discussions within the NMRG (and elsewhere).
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Table of Contents
1 Introduction ................................................. 3
2 Definitions .................................................. 4
3 Mapping of the OPERATION-TYPE macro .......................... 5
3.1 Mapping of the ARGUMENTS clause ............................ 6
3.2 Mapping of the ERRORS clause ............................... 6
3.3 Mapping of the RESULTS clause .............................. 6
3.4 Mapping of the CREATES clause .............................. 6
3.5 Mapping of the DELETES clause .............................. 7
3.6 Mapping of the STATUS clause ............................... 7
3.7 Mapping of the DESCRIPTION clause .......................... 7
3.8 Mapping of the REFERENCE clause ............................ 7
3.9 Mapping of the OPERATION-TYPE value ........................ 8
3.10 Usage Examples ............................................ 9
4 Revising Operation Type Definitions .......................... 10
5 Open Issues .................................................. 11
6 Security Considerations ...................................... 12
7 Authors' Address ............................................. 12
8 References ................................................... 12
9 Full Copyright Statement ..................................... 13
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1. Introduction
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 an adapted subset of
OSI's Abstract Syntax Notation One, ASN.1 (1988) [ASN1], termed the
Structure of Management Information (SMI) [RFC2578].
When designing a MIB module, it is often useful to define operations
on collections of related objects. Operations go beyond what is
available with normal read and write access to individual objects:
- Operations have a defined name which makes it easier to communicate
complex operations on MIB objects.
- Operations have well defined input and output parameters with
ordering constraints which reduces variability and simplifies
implementations.
- Operations can raise operation specific errors during their
invocation.
- Operations define whether they create or delete rows in conceptual
tables.
- The defined signatures of operations allow to implement tools that
generate APIs and stub procedures for command responder as well as
command generator applications.
Operations can be defined on arbitrary collections of objects.
However, it is expected that operations will normally be defined only
on closely related objects (e.g. objects contained in a single
conceptual row) since this simplifies implementation in extensible
agent environments.
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2. Definitions
SNMPv2-OPS DEFINITIONS ::= BEGIN
IMPORTS ObjectName FROM SNMPv2-SMI;
OPERATION-TYPE MACRO ::=
BEGIN
TYPE NOTATION ::=
ArgumentsPart
ErrorsPart
ResultsPart
CreatesPart
DeletesPart
"STATUS" Status
"DESCRIPTION" Text
ReferPart
VALUE NOTATION ::=
value(VALUE ObjectName)
ArgumentsPart ::=
"ARGUMENTS" "{" Parameters "}"
| empty
ErrorsPart ::=
"ERRORS" "{" NamedNumbers "}" -- INTEGER enumerations
| empty
ResultsPart ::=
"RESULTS" "{" Parameters "}"
| empty
CreatesPart ::=
"CREATES" "{" Rows "}"
| empty
DeletesPart ::=
"DELETES" "{" Rows "}"
| empty
Parameters ::=
Parameter
| Parameters "," Parameter
Parameter ::=
identifier Syntax
Syntax ::=
type
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| "BITS" "{" NamedBits "}"
NamedBits ::=
NamedBit
| NamedBits "," NamedBit
NamedBit ::=
identifier "(" number ")" -- number is nonnegative
NamedNumbers ::=
NamedNumber
| NamedNumbers "," NamedNumber
NamedNumber ::=
identifier "(" number ")"
Rows ::=
Row
| Rows "," Row
Row ::=
value(ObjectName)
Status ::=
"current"
| "deprecated"
| "obsolete"
ReferPart ::=
"REFERENCE" Text
| empty
-- a character string as defined in [RFC2578]
Text ::= value(IA5String)
END
END
3. Mapping of the OPERATION-TYPE macro
The OPERATION-TYPE macro is used to define an operation. An operation
has a defined signature which consists of the operation name, the
types and names of the arguments, the types and names of the results
and the operation specific errors that can occur while invoking the
operation. Operations can create or delete rows in conceptual tables.
The optional CREATES and DELETES clauses of the OPERATION-TYPE macro
identify the tables in which rows are created or deleted. It should
be noted that the expansion of the OPERATION-TYPE macro is something
which conceptually happens during implementation and not during run-
time.
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3.1. Mapping of the ARGUMENTS clause
The ARGUMENTS clause, which need not be present, defines an ordered
sequence of the types and names that form the arguments of the
operation. The operation's DESCRIPTION clause must specify the
information/meaning conveyed by each argument listed in the ARGUMENTS
clause.
The name of an argument must consist of one or more letters or
digits, and its initial character must be a lower-case letter.
Argument names must be unique across all arguments and results
defined in a single invocation of an OPERATION-TYPE macro.
3.2. Mapping of the ERRORS clause
The ERRORS clause, which need not be present, defines the operation
specific errors that can occur while invoking the operation. Errors
are represented as integer-valued named-number enumerations. Note
that although it is recommended that error values start at 1 and be
numbered contiguously, any valid value for an INTEGER in the range (1
to 2147483647 decimal) is allowed for an error value and, further,
error values need not be contiguously assigned. The no error case
does not need to be enumerated.
A label for a named-number enumeration within the ERRORS clause must
consist of one or more letters or digits, up to a maximum of 64
characters, and the initial character must be a lower-case letter.
(However, labels longer than 32 characters are not recommended.)
Note that hyphens are not allowed.
3.3. Mapping of the RESULTS clause
The RESULTS clause, which need not be present, defines an ordered
sequence of the types and names that form the results of the
operation. The operation's DESCRIPTION clause must specify the
information/meaning conveyed by each result listed in the RESULTS
clause.
The name of a result parameter must consist of one or more letters or
digits, and its initial character must be a lower-case letter. Result
names must be unique across all arguments and results defined in a
single invocation of an OPERATION-TYPE macro.
3.4. Mapping of the CREATES clause
The CREATES clause, which need not be present, defines the conceptual
table rows that will be created by invoking the operation. Rows are
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identified by the descriptor which refers to a conceptual row, i.e.
has a syntax which resolves to a SEQUENCE containing columnar
objects. The operation's DESCRIPTION clause must specify how an
implementation determines the instance identifier(s) of the row(s)
created by the operation.
3.5. Mapping of the DELETES clause
The DELETES clause, which need not be present, defines the conceptual
table rows that will be deleted by invoking the operation. Rows are
identified by the descriptor which refers to a conceptual row, i.e.
has a syntax which resolves to a SEQUENCE containing columnar
objects. The operation's DESCRIPTION clause must specify how an
implementation determines the instance identifier(s) of the row(s)
deleted by the operation.
3.6. Mapping of the STATUS clause
The STATUS clause, which must be present, indicates whether this
definition is current or historic.
The value "current" means that the definition is current and valid.
The value "obsolete" means the definition is obsolete and should not
be implemented and/or can be removed if previously implemented.
While the value "deprecated" also indicates an obsolete definition,
it permits new/continued implementation in order to foster
interoperability with older/existing implementations.
3.7. Mapping of the DESCRIPTION clause
The DESCRIPTION clause, which must be present, contains a textual
definition of the operation type which provides all semantic
definitions necessary for implementation and use, and should embody
any information which would otherwise be communicated in any ASN.1
commentary annotations associated with the object.
3.8. Mapping of the REFERENCE clause
The REFERENCE clause, which need not be present, contains a textual
cross-reference to some other document, either another information
module or some other document which provides additional information
relevant to this definition.
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3.9. Mapping of the OPERATION-TYPE value
The value of an invocation of the OPERATION-TYPE macro is the name of
the operation type, which is an OBJECT IDENTIFIER, an
administratively assigned name.
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3.10. Usage Examples
The first example shows an operation which creates or allocates a new
entry in the vacmSecurityToGroupTable [RFC2575].
vacmCreateSTGEntry OPERATION-TYPE
ARGUMENTS {
securityModel SnmpSecurityModel (1..2147483647),
securityName SnmpAdminString (SIZE(1..32)),
groupName SnmpAdminString (SIZE(1..32)),
storageType StorageType {
volatile(2),
nonVolatile(3)
}
}
ERRORS { rowAlreadyExists(1) }
CREATES { vacmSecurityToGroupEntry }
DESCRIPTION
"This operation installs and activates a new entry in
the vacmSecurityToGroupTable. The new entry is identified
by the securityModel and securityName parameters.
Implementations that do not support the creation of
new rows but which have permanent rows that are
currently notInService are expected to allocate
and activate one of these notInService rows. The
value of the storageType parameter is ignored in
this case.
The rowAlreadyExists(1) error is returned if the row
identified by securityModel and securityName already
exists."
::= { vacmOperations 1 }
The second example shows the definition of an operation that can be
used to remove a row from the vacmSecurityToGroupTable.
vacmRemoveSTGEntry OPERATION-TYPE
ARGUMENTS {
securityModel SnmpSecurityModel (1..2147483647),
securityName SnmpAdminString (SIZE(1..32))
}
ERRORS { rowDoesNotExist(1), readOnlyStorageType(2) }
DELETES { vacmSecurityToGroupEntry }
DESCRIPTION
"This operation removes an entry identified by the
securityModel and securityName parameters from the
vacmSecurityToGroupTable.
Entries which can not be removed (e.g. the value
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of vacmSecurityToGroupStorageType is permanent)
will be disabled by changing the RowStatus column
vacmSecurityToGroupStatus to notInService.
The rowDoesNotExist(1) error is returned if the row
identified by the securityModel and securityName parameters
does not exist. The readOnlyStorageType(2) error is returned
if the row cannot be removed or disabled since it is stored
in ROM."
::= { vacmOperations 2 }
The third example shows the definition of an operation which deletes
zero or more entries from the vacmSecurityToGroupTable. The argument
of the operation contains a pattern which is matched against all
vacmGroupName instances.
vacmRemoveSTGEntryByGroupName OPERATION-TYPE
ARGUMENTS {
pattern SnmpAdminString (SIZE(1..32))
}
RESULTS { numberRemoved Unsigned32 }
DELETES { vacmSecurityToGroupEntry }
DESCRIPTION
"This operation removes all entries from the
vacmSecurityToGroupTable where the vacmGroupName
matches the pattern parameter. The comparison is an
exact match where each byte must match exactly (no
wildcarding).
Entries that can not be removed (e.g. the value
of vacmSecurityToGroupStorageType is permanent)
will be disabled by changing the RowStatus column
vacmSecurityToGroupStatus to notInService.
Entries that can not be disabled (e.g. the value
of vacmSecurityToGroupStorageType is readOnly)
will be ignored.
The operation returns the number of entries that
were actually removed from or disabled in the
vacmSecurityToGroupTable."
::= { vacmOperations 3 }
4. Revising Operation Type Definitions
An operation definition may be revised in any of the following ways:
(1) The ERRORS clause may have new enumerations added.
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(2) A STATUS clause value of "current" may be revised as
"deprecated" or "obsolete". Similarly, a STATUS clause value of
"deprecated" may be revised as "obsolete". When making such a
change, the DESCRIPTION clause should be updated to explain the
rationale.
(3) A REFERENCE clause may be added or updated.
(4) Clarifications and additional information may be included in the
DESCRIPTION clause.
(5) Entirely new operations may be defined, named with previously
unassigned OBJECT IDENTIFIER values.
Otherwise, if the semantics of any previously defined operation are
changed (i.e., if a non-editorial change is made to any clause other
than those specifically allowed above), then the OBJECT IDENTIFIER
value associated with that operation must also be changed.
Note that changing the descriptor associated with an existing
operation is considered a semantic change, as these strings may be
used in fielded implementations and APIs derived from the operation
type definition.
5. Open Issues
1. The current version supports three different ways to define a
parameter. There are valid reasons for all three alternatives.
First, there is a need to have input parameters for operations
that do not exactly match an existing object. It would be a
burdon to require that all parameters be defined as objects
since many would end up with a write-only access (which does not
exist) anyway.
Second, there is a need to refer to types that are implicitely
defined as part of an object definition. A good example is
ifAdminStatus, which is an implicitly defined enumeration
without a proper name.
Third, it is necessary to assign names to parameters in order to
solve problems when a single type of implicit type shows up in a
arguments or result clause more than once.
2. It is currently not allowed to return vectors as a result. There
are several issues to consider in this case. The most important
reason to allow vectors is that you can have an operation which
itself returns a sequence of operations to recreate the current
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state. But the details how this would work are not yet fully
worked out.
6. Security Considerations
This document defines the means to define operations on collections
of MIB objects. The definition of operations has no direct security
impact on the Internet.
7. Authors' Address
Juergen Schoenwaelder
TU Braunschweig
Bueltenweg 74/75
38106 Braunschweig
Germany
Phone: +49 531 391-3283
EMail: schoenw@ibr.cs.tu-bs.de
8. References
[ASN1] Information processing systems - Open Systems
Interconnection - Specification of Abstract Syntax
Notation One (ASN.1), International Organization for
Standardization. International Standard 8824, December,
1987
[RFC2575] Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based
Access Control Model (VACM) for the Simple Network
Management Protocol (SNMP)", RFC 2575, April 1999
[RFC2578] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
Rose, M., and S. Waldbusser, "Structure of Management
Information Version 2 (SMIv2)", STD 58, RFC 2578, April
1999
[RFC2579] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
Rose, M., and S. Waldbusser, "Textual Conventions for
SMIv2", STD 58, RFC 2579, April 1999
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9. Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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