Internet Draft Expression MIB 26 March 1997
Expression MIB
26 March 1997
draft-ietf-disman-express-mib-01.txt
Bob Stewart
Cisco Systems, Inc.
bstewart@cisco.com
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 draft documents valid for a maximum of six months
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ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).
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1. Abstract
This memo defines an experimental portion of the Management Information
Base (MIB) for use with network management protocols in the Internet
community. In particular, it describes managed objects used for
managing expressions of MIB objects.
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2. The SNMP Network Management Framework
They are: The SNMP Network Management Framework presently consists of
three major components. They are:
the SMI, described in RFC 1902 [1] - the mechanisms used for
describing and naming objects for the purpose of management.
the MIB-II, STD 17, RFC 1213 [2] - the core set of managed objects for
the Internet suite of protocols.
the protocol, RFC 1157 [3] and/or RFC 1905 [4], - the protocol for
accessing managed objects.
The Framework permits new objects to be defined for the purpose of
experimentation and evaluation.
2.1. Object Definitions
Managed objects are accessed via a virtual information store, termed the
Management Information Base or MIB. Objects in the MIB are defined
using the subset of Abstract Syntax Notation One (ASN.1) defined in the
SMI. In particular, each object type is named by an OBJECT IDENTIFIER,
an administratively assigned name. The object type together with an
object instance serves to uniquely identify a specific instantiation of
the object. For human convenience, we often use a textual string,
termed the descriptor, to refer to the object type.
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3. Overview
The MIB was designed around the basic premise that an evaluated
expression should result in a MIB object that appears no different from
any other and is thus usable anywhere any other MIB object can be used,
whether by a management application directly or via another MIB.
Note that the operation of this MIB depends on the ability to use OID
fragments, that is, a part of an OID that may be missing the usual
prefix starting with iso. It is the opinion of the author that such a
use is legitimate even if it violates some pure definition of ASN.1,
since SNMP's use of ASN.1 is colloquial, not standard. The more
important test is whether implementations can readily handle such OID
fragments, and I believe they should be able to.
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4. Definitions
EXPRESSION-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, OBJECT-TYPE,
experimental, Integer32, Unsigned32 FROM SNMPv2-SMI
TEXTUAL-CONVENTION, RowStatus,
AutonomousType, DisplayString, FROM SNMPv2-TC
MODULE-COMPLIANCE, OBJECT-GROUP FROM SNMPv2-CONF
expressionMIB MODULE-IDENTITY
LAST-UPDATED "9703141700Z"
ORGANIZATION "IETF Distributed Management Working Group"
CONTACT-INFO "Bob Stewart
Cisco Systems, Inc.
170 West Tasman Drive,
San Jose CA 95134-1706.
Phone: +1 408 526 4527
Email: bstewart@cisco.com"
DESCRIPTION
"The MIB module for defining expressions of MIB objects
for network management purposes."
::= { experimental xx }
ExpressionName ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"An identification for an expression. An ExpressionName
corresponds one-to-one to an ExpressionIndex.
This is the reliable identification of an expression,
subject to change only by administrative request."
SYNTAX DisplayString (SIZE (1..64))
ExpressionIndex ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"An integer shorthand identification for an expression.
An ExpressionIndex corresponds one-to-one to an
ExpressionName.
A system may change the value of an ExpressionIndex
when it is reinitialized but must correct all references
to that ExpressionIndex."
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SYNTAX Unsigned32 (1..4294967295)
ExpressionIndexOrZero ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Either an ExpressionIndex or zero. The meaning of zero
depends on the DESCRIPTION of the object."
SYNTAX Unsigned32 (0..4294967295)
expressionMIBObjects OBJECT IDENTIFIER ::= { expressionMIB 1 }
expCreate OBJECT IDENTIFIER ::= { expressionMIBObjects 1 }
expDefine OBJECT IDENTIFIER ::= { expressionMIBObjects 2 }
expValue OBJECT IDENTIFIER ::= { expressionMIBObjects 3 }
--
-- Creation Table
--
expCreateLastChange OBJECT-TYPE
SYNTAX TimeStamp
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The value of sysUpTime the last time an expression was
created or deleted or had its name changed using
expExpressionName."
::= { expCreate 1 }
expCreateTable OBJECT-TYPE
SYNTAX SEQUENCE OF ExpCreateEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A table of expression names, for creating and deleting
expressions."
::= { expCreate 2 }
expCreateEntry OBJECT-TYPE
SYNTAX ExpCreateEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"Information about a single expression. New expressions
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can be created using expCreateStatus.
To create an expression create the named entry in this
table and activate it with RowStatus. Then use
expExpressionIndex to populate expExpressionTable
expObjectTable.
Deleting an entry deletes all related entries in
expExpressionTable and expObjectTable."
INDEX { IMPLIED expExpressionName }
::= { expCreateTable 1 }
ExpCreateEntry ::= SEQUENCE {
expCreateName ExpressionName,
expExpressionIndex ExpressionIndex,
expCreateStatus RowStatus
}
expCreateName OBJECT-TYPE
SYNTAX ExpressionName
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The name of the expression. Choosing names with useful
lexical ordering supports using GetNext or GetBulk to
retrieve a useful subset of the table."
::= { expCreateEntry 1 }
expExpressionIndex OBJECT-TYPE
SYNTAX ExpressionIndex
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The numeric identification of the expression."
::= { expCreateEntry 2 }
expCreateStatus OBJECT-TYPE
SYNTAX RowStatus
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The control that allows creation/deletion of entries.
Activate the entry then use expExpressionIndex to
define the expression in expExpressionTable."
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::= { expCreateEntry 3 }
--
-- Expression Definition Table
--
expExpressionTable OBJECT-TYPE
SYNTAX SEQUENCE OF ExpExpressionEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A table of expression definitions."
::= { expDefine 1 }
expExpressionEntry OBJECT-TYPE
SYNTAX ExpExpressionEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"Information about a single expression. An entry appears in
this table when an expCreateEntry is activated. Deleting the
matching expCreateEntry deletes this entry and its
associated expObjectTable entries."
INDEX { expExpressionIndex }
::= { expExpressionTable 1 }
ExpExpressionEntry ::= SEQUENCE {
expExpressionName ExpressionName,
expExpression DisplayString,
expExpressionComment DisplayString,
expExpressionPrefix OBJECT IDENIFIER
}
expExpressionName OBJECT-TYPE
SYNTAX ExpressionName
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"The unique name of the expression, the same as
expCreateName.
Use this object to change the expression's name without
changing its expExpressionIndex."
::= { expExpressionEntry 1 }
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expExpression OBJECT-TYPE
SYNTAX DisplayString (SIZE (1..1024))
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"The expression to be evaluated. Except for the variable
names the expression is in ANSI C syntax. ANSI C operators
and functions are allowed only if explicitly listed here.
Variables are expressed as a dollar sign ('$') and an
integer that corresponds to an expObjectIndex. An
example of a valid expression is:
($1-$5)*100
The only operators and functions allowed are:
( )
+ - * /
& | ^ << >> ~
! && || == != > >= < <=
Integer-typed object are treated as 32- or 64-bit, signed
or unsigned integers, as appropriate. The results of
mixing them are as for ANSI C.
OCTET STRINGS and OBJECT IDENTIFIERs are treated as arrays of
unsigned 8-bit integers and unsigned 32-bit integers,
respectively.
A short list of array handling functions for comparing and
masking are to be defined.
Conditional expressions result in a 32-bit, unsigned integer
of value 0 for false or 1 for true. When an arbitrary value
is used in a boolean expression 0 is false and non-zero is
true."
DEFVAL { ''H }
::= { expExpressionEntry 2 }
expExpressionComment OBJECT-TYPE
SYNTAX DisplayString
MAX-ACCESS read-write
STATUS current
DESCRIPTION
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"A comment to explain the use or meaning of the
expression."
DEFVAL { ''H }
::= { expExpressionEntry 3 }
expExpressionPrefix OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"An object prefix to assist an application in determining
the instance indexing to use in expValueTable, relieving the
application of the need to scan the expObjectTable to
determine such a prefix.
See expObjectTable for information on wildcarded objects.
If the expValueInstance portion of the value OID may
be treated as a scalar (that is, normally, 0) the value of
expExpressionPrefix is 0.0.
Otherwise expExpressionPrefix is the value of any wildcarded
instance of expObjectID for the expression. This is
sufficient as the remainder, that is, the instance fragment
relevant to instancing the values must be the same for all
wildcarded objects in the expression."
::= { expExpressionEntry 4 }
--
-- Object Table
--
expObjectTable OBJECT-TYPE
SYNTAX SEQUENCE OF ExpObjectEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A table of object definitions for each expExpression.
Wildcarding instance IDs:
It is legal to omit all or part of the instance portion for
some or all of the objects in an expression. (See the
DESCRIPTION of expObjectID for details. However, note that
if more than one object in the same expression is wildcarded
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in this way, they all must be objects where that portion of
the instance is the same. In other words, all objects may be
in the same SEQUENCE or in different SEQUENCEs but with the
same semantic index value (e.g., the value of ifIndex)
for the wildcarded portion."
::= { expDefine 2 }
expObjectEntry OBJECT-TYPE
SYNTAX ExpObjectEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"Information about a object. An application creates entries
in this table while creating an expression."
-- SPARSE-AUGMENTS { expExpressionEntry }
INDEX { expExpressionIndex, expObjectIndex }
::= { expObjectTable 1 }
ExpObjectEntry ::= SEQUENCE {
expObjectIndex Unsigned32,
expObjectID OBJECT IDENTIFIER,
expObjectSampleType INTEGER,
expObjectDeltaInterval Integer32,
expObjectDeltaDiscontinuityID OBJECT IDENTIFIER,
expObjectConditional OBJECT IDENTIFIER,
expObjectStatus RowStatus
}
expObjectIndex OBJECT-TYPE
SYNTAX Unsigned32 (1..4294967295)
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A unique, numeric identification for an object. Prefixed
with a dollar sign ('$') this is used to reference the
object in the corresponding expExpression."
::= { expObjectEntry 1 }
expObjectID OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The OBJECT IDENTIFIER (OID) of this object. Note that this
can be the OID of a leaf object in a MIB (e.g., ifInOctets.1
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or sysUpTime.0). The OID may be fully qualified, meaning it
includes an instance identifier part, or it may not be fully
qualified, meaning it may lack all or part of the instance
identifier. If the expObjectID is not fully qualified, then
the value of the expression will be multiple values, as if
done for a GetNext sweep of the object."
::= { expObjectEntry 2 }
expObjectSampleType OBJECT-TYPE
SYNTAX INTEGER {
absoluteValue(1),
deltaValue(2)
}
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The method of sampling the selected variable."
DEFVAL { absoluteValue }
::= { expObjectEntry 3 }
expObjectDeltaInterval OBJECT-TYPE
SYNTAX Integer32 (0..86400)
UNITS "seconds"
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"Sampling interval for objects with expObjectSampleType
'deltaValue'.
This object is not instantiated if not applicable.
A value of 0 indicates no automated sampling. In this case
the delta is the difference from the last time the expression
was evaluated. Note that this is subject to unpredictable
delta times in the face of retries or multiple managers.
A value greater than zero is the number of seconds between
automated samples.
Until the delta interval has expired once the delta for the
object is effectively not instantiated and evaluating
the expression has results as if the object itself were not
instantiated.
Note that delta values potentially consume large amounts of
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system CPU and memory. Delta state and processing must
continue constantly even if the expression is not being used.
For wildcarded objects this can be substantial overhead."
DEFVAL { 0 }
::= { expObjectEntry 4 }
expObjectDeltaDiscontinuityID OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The OBJECT IDENTIFIER (OID) of a TimeTicks object that
indicates a discontinuity in the value at expObjectID.
This object is not instantiated if not applicable.
The OID may be for a leaf object (e.g. sysUpTime.0) or may
be wildcarded to match expObjectID.
DEFVAL { 0 0 }
::= { expObjectEntry 5 }
expObjectConditional OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The OBJECT IDENTIFIER (OID) of an object that overrides
whether the instance of expObjectID is to be considered
usable. If the value of the object at expObjectConditional
is 0, the object at expObjectID is treated as if it is not
instantiated, otherwise it is treated as usual.
The OID may be for a leaf object (e.g. sysUpTime.0) or may
be wildcarded to match expObjectID.
DEFVAL { 0 0 }
::= { expObjectEntry 5 }
expObjectStatus OBJECT-TYPE
SYNTAX RowStatus
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The control that allows creation/deletion of entries."
::= { expObjectEntry 7 }
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--
-- Expression Value Table
--
expValueTable OBJECT-TYPE
SYNTAX SEQUENCE OF ExpValueEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A table of values from evaluated expressions."
::= { expValue 1 }
expValueEntry OBJECT-TYPE
SYNTAX ExpValueEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A single value from an evaluated expression. For a given
instance, only one "Val" object in the conceptual row will
be instantiated, that is, the one with the appropriate type
for the value. Reading a value from the table causes the
evaluation of the expression for that value.
If in the attempt to evaluate the expression one or more
of the necessary objects is not available, the corresponding
entry in this table is effectively not instantiated."
INDEX { expExpressionIndex,
expValueInstance }
::= { expValueTable 1 }
ExpValueEntry ::= SEQUENCE {
expValueInstance OBJECT IDENTIFIER,
expValueType INTEGER,
expValueUnsigned32Val Unsigned32,
expValueInteger32Val Integer32,
expValueOctetStringVal OCTET STRING,
expValueOidVal OBJECT IDENTIFIER,
expValueCounter64Val Counter64
}
expValueInstance OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER,
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
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"The final instance portion of a value's OID according to
the wildcarding in instances of expObjectID for the
expression.
If there is no wildcarding, the value is 0.0.
If there is wildcarding, the value is 0.0 followed by
a value that the wildcard can take, thus defining one value
instance for each real, possible value of the wildcard.
So, for example, if the wildcard worked out to be an ifIndex,
there is an expValueInstance for each applicable ifIndex."
::= { expValueEntry 1 }
expValueType OBJECT-TYPE
SYNTAX INTEGER { counter32(1), unsignedOrGauge32(2),
timeTicks(3), integer32(4), ipAddress(5),
octetString(6), objectId(7), counter64(8) }
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The type of the value. One and only one of the value
objects that follow will be valid based on this type."
::= { expValueEntry 2 }
expValueUnsigned32Val OBJECT-TYPE
SYNTAX Unsigned32 -- (0..4294967295)
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The value when expValueType is one of 'counter32',
'unsignedOrGauge32', or 'timeTicks'."
::= { expValueEntry 3 }
expValueInteger32Val OBJECT-TYPE
SYNTAX Integer32 -- (-2147483648..2147483647)
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The value when expValueType is 'integer32'."
::= { expValueEntry 4 }
expValueOctetStringVal OBJECT-TYPE
SYNTAX OCTET STRING (SIZE (0..65536))
MAX-ACCESS read-only
STATUS current
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DESCRIPTION
"The value when expValueType is 'ipAddress' or
'octetString'."
::= { expValueEntry 5 }
expValueOidVal OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The value when expValueType is 'objectId'."
::= { expValueEntry 6 }
expValueCounter64Val OBJECT-TYPE
SYNTAX Counter64 -- (0..18446744073709551615)
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The value when expValueType is 'counter64'."
::= { expValueEntry 7 }
-- The compliance statements have yet to be written. The intent is
-- that all objects are required. A proper subset
-- of the MIB may disallow instance wildcards, deltaValues, or
-- expObjectConditionals.
END
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5. Acknowledgements
This MIB contains considerable contributions from the RMON MIB, the
Distributed Management Design Team (Andy Bierman, Maria Greene, Bob
Stewart, and Steve Waldbusser), and colleagues at Cisco.
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6. References
[1] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
S. Waldbusser, "Structure of Management Information for version 2
of the Simple Network Management Protocol (SNMPv2)", RFC 1902,
January 1996.
[2] McCloghrie, K., and M. Rose, Editors, "Management Information Base
for Network Management of TCP/IP-based internets: MIB-II", STD 17,
RFC 1213, March 1991.
[3] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple Network
Management Protocol", RFC 1157, May 1990.
[4] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and
S. Waldbusser, "Protocol Operations for version 2 of the Simple
Network Management Protocol (SNMPv2)", RFC 1905, January 1996.
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7. Security Considerations
Security issues are not discussed in this memo.
8. Author's Address
Bob Stewart
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
Phone: 408-526-4527
Email: bstewart@cisco.com
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Table of Contents
1 Abstract ........................................................ 2
2 The SNMP Network Management Framework ........................... 3
2.1 Object Definitions ............................................ 3
3 Overview ........................................................ 4
4 Definitions ..................................................... 5
5 Acknowledgements ................................................ 17
6 References ...................................................... 18
7 Security Considerations ......................................... 19
8 Author's Address ................................................ 19
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