Internet Draft Instance Reservation MIB September 16, 1996
Definitions of Managed Objects for Instance Reservation
September 16, 1996
<draft-ietf-resmib-instresmib-00.txt>
David Battle
SNMP Research, Inc.
battle@snmp.com
Ulrich Haebel
Siemens Nixdorf Informationssysteme AG
Ulrich.Haebel@mch.sni.de
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 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 ``work
in progress.''
To learn the current status of any Internet-Draft, please check
the ``1id-abstracts.txt'' listing contained in the Internet-
Drafts Shadow Directories on ds.internic.net (US East Coast),
nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or
munnari.oz.au (Pacific Rim).
SNMP Research hereby covenants that it will not assert any claims
in this draft, any continuations, divisions, or continuations-in-
part of the foregoing against any party that makes, uses, sells,
imports, or offers for sale, an implementation of an IETF
standards-track MIB module that includes SNMP Research's
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contributed instance reservation technology, or any derivative of
that contribution, provided that the MIB module is employed to
implement the Internet-standard network management framework.
Such grant of rights is limited in that it does not include a
right to incorporate such SNMP Research instance reservation
technology into proprietary MIB modules.
This grant of rights will permanently terminate with respect to
any party (and to any subsidiary of a party) that asserts a patent
it owns or controls, either directly or indirectly, against SNMP
Research or any of its subsidiaries for implementation of, or
operation of any system utilizing, instance reservation
technology. The termination of rights will occur as of the date
the patent is asserted against SNMP Research.
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 a basic set
of managed objects for instance reservation in other MIB tables.
This memo does not specify a standard for the Internet community.
2. The SNMPv2 Network Management Framework
The SNMPv2 Network Management Framework consists of four major
components. They are:
o STD 17, RFC 1213 [1] defines MIB-II, the core set of managed
objects for the Internet suite of protocols.
o RFC 1902 Structure of Management Information for Version 2 of
the Simple Network Management Protocol (SNMPv2)
o RFC 1903 Textual Conventions for Version 2 of the Simple
Network Management Protocol (SNMPv2)
o RFC 1904 Conformance Statements for Version 2 of the Simple
Network Management Protocol (SNMPv2)
o RFC 1905 Protocol Operations for Version 2 of the Simple
Network Management Protocol (SNMPv2)
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o RFC 1906 Transport Mappings for Version 2 of the Simple
Network Management Protocol (SNMPv2)
o RFC 1907 Management Information Base for Version 2 of the
Simple Network Management Protocol (SNMPv2)
o RFC 1908 Coexistence between Version 1 and Version 2 of the
Internet-standard Network Management Framework
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[2]. 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
object descriptor, to refer to the object type.
3. Overview
Traditionally SNMP agents have been "monolithic" in nature,
meaning that a single linked module was used to represent the
entire MIB for a particular entity. In recent years several
"extensible agent" technologies have come to exist which split the
MIB among several distinct linked modules, typically called
subagents. The existance of these subagent modules has created
the need for a mechanism by when different subagents may
coordinate instances in mib tables in such a way that each
subagent can perform its function without collisions occuring when
more than one subagent tries to present the same instance of a
particualar managed object.
This draft is concerned primarily with providing a simple
mechanism by which subagents can "reserve" instances in certain
tables for their own use and find out about reservations made by
other subagents. This approach was taken to insure ease and speed
of implementation, while allowing room for future growth.
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4. The Structure of the MIB
The instance reservation mib consists of three tables
(instanceTable, allocInstTable, and maxInstTable). The tables are
used together to allow subagents to reserve particular instances
(rows) in other SNMP tables. All of the objects in the mib are
read only or not accessible. Subagents reserve instances by
asking questions of the form "which instance should I use" or "may
I reserve this instance" (that is, via GET requests) rather than
making statements such as "I want to reserve this instance" (using
SET requests). These get requests do the actual work of making
the reservation. Making reservations using this method has the
following advantages:
- Reservations may be done in a single exchange, since the
return value from the get may be used to return reservation
information. Since sets return no new information other
than success or failure, a set and a subsequent get
would be required to reserve an instance, then return
instance information.
- Problems with locking and simultaneous access associated
with sets in multithreaded agents are avoided.
The table instanceTable reflects the state of the instance
reservation table. It is used to request reservation of a specific
row of a given table or get information about what rows are
reserved. instanceTable is indexed by two Object Identifiers, the
OID of the table in which an instance is to be reserved, and the
OID which is formed by concatenating the indices for the row being
reserved. instanceUsed and instanceNotUsed are the only two
accessible objects. A getexact or getnext on the instanceUsed
object return an indication of whether a particular instance is in
use or has been used in the past (instances which have never been
used do not show up in the table at all). A getexact on an
instanceUsed object which is not currently in use will reserve
that instance, and return either a onceUsed or neverUsed
indication. Future queries about that instance will return the
"reserved" state. Thus, if a subagent knows which instance it
wants, it does a getexact on the instanceTable supplying the OIDs
of the table and the desired instance. If the return value
indicates that the instance is not in use, the subagent may
immediately start using it. A getnext will query whether an
instance is in use without reserving that instance. The
instanceNotUsed object (indexed by the same OIDs as instanceUsed)
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is used to free a row reservation using a getexact operation in
the same fashion (as instanceUsed). Getnext operations on
instanceNotUsed return the same information as getnext operations
on instanceUsed.
The second table (allocInstTable) is used when a subagent does not
know which instance in a given table it wants to allocate.
allocInstTable is indexed by algorithm, OID of the table from
which an instance is to be allocated, and instance type to
allocate. A getexact operation on allocInstInstance causes an
instance allocation and reservation to occur The algorithm
specified, either firstNeverUsed or firstNotCurrentlyUsed,
specifies to the entity implementing the mib which type of
instance to reserve. The instance type is formed by building an
oid with the first field specifying the number of indices, and
each subsequent field spcifying the enumerated type of the indices
for the row to be allocated. Getnext operations on this table
will always show it empty.
The third table (maxInstTable) is used by subagents which want to
use instanceTable (the first table in this mib) to directly
request an instance, but which first need to inquire about the
largest instance already in use. This table is indexed by
algorithm and the OID for the table for which an instance is
requested. Algorithm is specified as largestEverUsed or
largestCurrentlyUsed. Getexact or getnext operations on
maxInstInstance return the lexicographically largest instance
currently (or ever) used in the indicated table. Unlike the
previous two tables, getexact and getnext operations have no side
effects.
5. Definitions
INSTANCEREP-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, OBJECT-TYPE, NOTIFICATION-TYPE,
ObjectName, Integer32, Counter32
FROM SNMPv2-SMI;
instanceRep MODULE-IDENTITY
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LAST-UPDATED "9605071655Z"
ORGANIZATION "SNMP Research, Inc."
CONTACT-INFO "David Battle
Postal: SNMP Research, Inc.
3001 Kimberlin Heights Road
Knoxville, TN 37920
Tel: +1 423 573 1434
E-Mail: battle@snmp.com"
DESCRIPTION "This module describes a mib for reserving instances in
various mib tables for use by extensible agent systems."
::= { enterprises 99 12 17 }
-- The instance Group
instance OBJECT IDENTIFIER ::= { instanceRep 1 }
-- used as a prefix for OIDs describing a particular instance
instanceInstanceBase OBJECT IDENTIFIER ::= { instanceRep 2 }
-- used as a prefix for OIDs describing instance types
instanceTypeBase OBJECT IDENTIFIER ::= { instanceRep 3 }
instanceTable OBJECT-TYPE
SYNTAX SEQUENCE OF InstanceEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "A table of reserved instances containing presently and
historically reserved instances. Different contexts may be
used by different subagents in allocating instances so that,
for example, only a subagent which allocates an instance may
release it."
::= { instance 1 }
instanceEntry OBJECT-TYPE
SYNTAX InstanceEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "An entry describing a particular reserved (or previously
reserved) instance containing objects which describe the
instance's current state."
INDEX { instanceObject, IMPLIED instanceInstance }
::= { instanceTable 1 }
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InstanceEntry ::= SEQUENCE {
instanceObject OBJECT IDENTIFIER,
instanceInstance OBJECT IDENTIFIER,
instanceUsed INTEGER,
instanceNotUsed INTEGER
}
instanceObject OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The oid of the table to be associated with the allocated
instance. This should be the oid of the SEQUENCE, not
the oid of any particular object."
::= { instanceEntry 1 }
instanceInstance OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The instance to be allocated or released encoded as a oid.
The instance is prefixed with the instanceInstanceBase oid
to ensure that it is a legal oid."
::= { instanceEntry 2 }
instanceUsed OBJECT-TYPE
SYNTAX INTEGER
{
neverUsed(1),
onceUsed(2),
reserved(3)
}
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The state of the allocated instance as indicated by the
state table below. A get-exact operation on this
object causes the indicated state transitions. The state
returned is indicated as a separate column in the state
table."
::= { instanceEntry 3 }
--
-- Operation: Get-Exact on instanceUsed Get-Exact on instanceNotUsed
--
-- Current State State Returned State Entered State Returned State Entered
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-- neverUsed neverUsed reserved NULL neverUsed
-- onceUsed onceUsed reserved onceUsed onceUsed
-- reserved reserved reserved onceUsed onceUsed
--
-- The idea is that subagents will use a get-exact on a particular instance of
-- instanceUsed to allocate a row and a get-exact on a particular instance of
-- instanceNotUsed in order to free the row. The State Returned column
-- indicates what should be returned for get-exact. For get-next the
-- current state should be returned and should not be changed. The subagent
-- can tell whether the instance we succesfully allocated by looking at
-- the state returned from the get-exact; neverUsed or onceUsed means success.
-- reserved means failure (ie it was already reserved).
--
-- NULL is used above to indicate that in this situation the agent should
-- behave as though the instance does not exist.
--
-- Note also that the instance reservation mib may be implemented in such
-- a way that only get-exacts in a certain "context" will change the
-- state variables instanceUsed and instanceNotUsed. instanceUsed and
-- instanceNotUsed are shadow objects which always match each other in
-- their internal value.
--
instanceNotUsed OBJECT-TYPE
SYNTAX INTEGER
{
neverUsed(1),
onceUsed(2),
reserved(3)
}
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The state of the allocated instance as indicated by the
state table above. A get-exact operation on this
object causes the indicated state transitions. The state
returned is indicated as a separate column in the state
table."
::= { instanceEntry 4 }
allocInstTable OBJECT-TYPE
SYNTAX SEQUENCE OF AllocInstEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "An ephemeral list used for allocation of instances. Entries
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persist only long enough to return a value, then disappear.
Different contexts may be used by different subagents in
allocating instances so that, for example, only a subagent
which allocates an instance may release it."
::= { instance 2 }
allocInstEntry OBJECT-TYPE
SYNTAX AllocInstEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "An entry used for allocating instances containing objects
need for the description of the variety of instance to be
allocated."
INDEX { allocInstAlgorithm, allocInstObject, IMPLIED allocInstType }
::= { allocInstTable 1 }
AllocInstEntry ::= SEQUENCE {
allocInstAlgorithm INTEGER,
allocInstObject OBJECT IDENTIFIER,
allocInstType OBJECT IDENTIFIER,
allocInstInstance OBJECT IDENTIFIER
}
allocInstAlgorithm OBJECT-TYPE
SYNTAX INTEGER {
firstNeverUsed(1),
firstNotCurrentlyUsed(2)
}
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The algorithm to be used in allocating the instance."
::= { allocInstEntry 1 }
allocInstObject OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The oid of the table to be associated with the allocated
instance. This should be the oid of the SEQUENCE, not
the oid of any particular object."
::= { allocInstEntry 2 }
allocInstType OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS not-accessible
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STATUS current
DESCRIPTION "The type of instance to be allocated. The initial portion
of this oid consists of instanceTypeBase. The subsequent
sub-identifiers have the following meaning:
Sub-Id Value Meaning
1 n total number of indices in the instance
2 type the type of the first index as indicated below
x type the type of the (x-1)th index as indicated below
n+1 type the type of the last index as indicated below
Value Type of Index
1 INTEGER
2 ..."
::= { allocInstEntry 3 }
allocInstInstance OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS read-only
STATUS current
DESCRIPTION "A get-exact request on this object returns an instance
encoded as an oid which was allocated according to the
algorithm specified in the allocInstAlgorithm index. The
allocated instance will be of the type indicated by the
allocInstType index and will be associated with the table
indicated by allocInstObject. When an instance is allocated
using this table it causes a cooresponding entry to appear
in the instanceTable."
::= { allocInstEntry 4 }
maxInstTable OBJECT-TYPE
SYNTAX SEQUENCE OF AllocInstEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "A table of the maximum instances currently reserved."
::= { instance 3 }
maxInstEntry OBJECT-TYPE
SYNTAX MaxInstEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "An entry describing the maximum instance for a particular
table."
INDEX { maxInstAlgorithm, maxInstObject }
::= { maxInstTable 1 }
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MaxInstEntry ::= SEQUENCE {
maxInstAlgorithm INTEGER,
maxInstObject OBJECT IDENTIFIER,
maxInstInstance OBJECT IDENTIFIER
}
maxInstAlgorithm OBJECT-TYPE
SYNTAX INTEGER {
largestEverUsed(1),
largestCurrentlyUsed(2)
}
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The algorithm to be used in computing the maximum instance."
::= { maxInstEntry 1 }
maxInstObject OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION "The oid of the table for which the maximum instance should
be computed. This should be the oid of the SEQUENCE, not
the oid of any particular object."
::= { maxInstEntry 2 }
maxInstInstance OBJECT-TYPE
SYNTAX OBJECT IDENTIFIER
MAX-ACCESS read-only
STATUS current
DESCRIPTION "The largest instance reserved in the indicated table
computed according to the indicated algorithm. Items
in the onceUsed state are not considered for the
largestCurrentlyUsed algorithm, while they are considered
for the largestEverUsed algorithm. The value of this object
will be identical to the value of of the appropriate
instance of the instanceInstance object."
::= { maxInstEntry 4 }
END
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6. References
[1] McCloghrie, K., and M. Rose, Editors, "Management Information
Base for Network Management of TCP/IP-based internets: MIB-
II", STD 17, RFC 1213, Hughes LAN Systems, Performance
Systems International, March 1991.
[2] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S.,
"Structure of Management Information for Version 2 of the
Simple Network Mana" gement Protocol (SNMPv2)" , RFC 1902,
SNMP Research, Inc., Cisco Systems, Dover Beach Consulting,
Inc., Carnegie Mello n University, January 1996.
7. Security Considerations
Security issues are not discussed in this memo.
8. Authors' Addresses
David Battle
SNMP Research, Inc.
3001 Kimberlin Heights Rd.
Knoxville, TN 37920-9716
US
Phone: +1 423 573 1434
Email: battle@snmp.com
Ulrich Haebel
Siemens Nixdorf Informationssysteme AG
Otto-Hahn-Ring 6
81739 Muenchen
Germany
Phone: +49 89 636 42141
Email: Ulrich.Haebel@mch.sni.de
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Table of Contents
1 Abstract .................................................. 2
2 The SNMPv2 Network Management Framework ................... 2
2.1 Object Definitions ...................................... 3
3 Overview .................................................. 3
4 The Structure of the MIB .................................. 4
5 Definitions ............................................... 5
6 References ................................................ 12
7 Security Considerations ................................... 12
8 Authors' Addresses ........................................ 12
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