Network Working Group J. Schoenwaelder
Internet-Draft TU Braunschweig
Expires: December 20, 2001 June 21, 2001
Storage Type MIB
draft-schoenw-storage-type-00
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
The second version of the Structure of Management Information (SMIv2)
introduced the StorageType textual convention in RFC 2579. It is
used to describe the memory realization of rows in conceptual tables.
Several standards-track MIB modules make use of this convention.
Implementation experience shows that different approaches are used to
actually write conceptual rows into non-volatile memory. This memo
addresses this question and provides a MIB module which can be used
to explicitly commit non-volatile rows into non-volatile memory.
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Table of Contents
1. The SNMP Management Framework . . . . . . . . . . . . . . . . 3
2. StorageType Interpretations . . . . . . . . . . . . . . . . . 4
3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 11
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
6. Intellectual Property Notice . . . . . . . . . . . . . . . . . 12
References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 14
A. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 14
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 15
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1. The SNMP Management Framework
The SNMP Management Framework presently consists of five major
components:
o An overall architecture, described in RFC 2571 [2].
o Mechanisms for describing and naming objects and events for the
purpose of management. The first version of this Structure of
Management Information (SMI) is called SMIv1 and described in STD
16, RFC 1155 [3], STD 16, RFC 1212 [4] and RFC 1215 [5]. The
second version, called SMIv2, is described in STD 58, RFC 2578
[6], STD 58, RFC 2579 [7] and STD 58, RFC 2580 [8].
o Message protocols for transferring management information. The
first version of the SNMP message protocol is called SNMPv1 and
described in STD 15, RFC 1157 [9]. A second version of the SNMP
message protocol, which is not an Internet standards track
protocol, is called SNMPv2c and described in RFC 1901 [10] and RFC
1906 [11]. The third version of the message protocol is called
SNMPv3 and described in RFC 1906 [11], RFC 2572 [12] and RFC 2574
[13].
o Protocol operations for accessing management information. The
first set of protocol operations and associated PDU formats is
described in STD 15, RFC 1157 [9]. A second set of protocol
operations and associated PDU formats is described in RFC 1905
[14].
o A set of fundamental applications described in RFC 2573 [15] and
the view-based access control mechanism described in RFC 2575
[16].
A more detailed introduction to the current SNMP Management Framework
can be found in RFC 2570 [17].
Managed objects are accessed via a virtual information store, termed
the Management Information Base or MIB. Objects in the MIB are
defined using the mechanisms defined in the SMI.
This memo specifies a MIB module that is compliant to the SMIv2. A
MIB conforming to the SMIv1 can be produced through the appropriate
translations. The resulting translated MIB must be semantically
equivalent, except where objects or events are omitted because no
translation is possible (use of Counter64). Some machine readable
information in SMIv2 will be converted into textual descriptions in
SMIv1 during the translation process. However, this loss of machine
readable information is not considered to change the semantics of the
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MIB.
2. StorageType Interpretations
The SMIv2 introduced the StorageType textual convention which is used
to describe the memory realization of a conceptual rows. In
particular, the StorageType textual convention can be used to mark
dynamically created rows as volatile or non-volatile. Several MIBs
on the standards-track use this StorageType textual convention for
all conceptual tables that support row creation. The StorageType
textual convention is defined in RFC 2579 [7] as follows:
StorageType ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Describes the memory realization of a conceptual row. A
row which is volatile(2) is lost upon reboot. A row which
is either nonVolatile(3), permanent(4) or readOnly(5), is
backed up by stable storage. A row which is permanent(4)
can be changed but not deleted. A row which is readOnly(5)
cannot be changed nor deleted.
If the value of an object with this syntax is either
permanent(4) or readOnly(5), it cannot be written.
Conversely, if the value is either other(1), volatile(2) or
nonVolatile(3), it cannot be modified to be permanent(4) or
readOnly(5). (All illegal modifications result in a
'wrongValue' error.)
Every usage of this textual convention is required to
specify the columnar objects which a permanent(4) row must
at a minimum allow to be writable."
SYNTAX INTEGER {
other(1), -- eh?
volatile(2), -- e.g., in RAM
nonVolatile(3), -- e.g., in NVRAM
permanent(4), -- e.g., partially in ROM
readOnly(5) -- e.g., completely in ROM
}
Note that the text in the DESCRIPTION clause does not make any
explicit statements when a conceptual row is actually written to non-
volatile storage. One possible interpretation is that rows must be
committed to non-volatile storage on each set operation which
modifies a row. However, many implementations prefer to not write to
non-volatile storage on each set operation. There are two main
reasons for this:
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1. Writing non-volatile storage is on some systems time and/or
resource consuming. Committing rows to non-volatile memory
during the set operation is thus considered too expensive.
2. Some management applications create and configure rows by sending
a sequence of set requests. Committing the row to non-volatile
storage on every single set operation is too costly, especially
on systems that can only commit complex system configurations to
non-volatile memory.
Implementations therefore use different strategies:
1. Some systems update the non-volatile storage on each set
operation.
2. Some systems first return a positive response to the set
operation and they write the modified variables to non-volatile
storage at some later point in time when there are no more
changes.
3. Some systems first return a positive response to the set
operation and they delay the actual write to non-volatile storage
to some external event (e.g. shutdown of the agent, pushing of a
global write button).
4. Some systems first return a positive response to the set
operation and they write the modified variables when a logical
row operation has completed. (For example, an incomplete
conceptual row is not saved in non-volatile storage until it is
complete and activated.)
It seems that delayed writes to non-volatile storage are common
practice. However, since this behavior is right now completely
implementation dependent, there is no simple mechanism a management
application can use to learn how a given device implements the
StorageType textual convention and therefore it is unclear when a row
is actually written to stable storage.
Commonly used command line interfaces of network devices follow a
paradigm where explicit commands trigger the storage of the device
configuration (or logical parts of the device configuration) in non-
volatile storage. Operational experience with these interfaces
suggests that it is (i) valuable to have explicit control when
configuration data is written to non-volatile storage and (ii)
efficient to implement on networking devices.
This document therefore proposes to introduce new MIB objects which
can be used by management applications to control when non-volatile
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conceptual rows are written to stable storage. The MIB supports
multiple "write buttons" to support implementations which use
different mechanisms in different parts of the MIBs to save rows in
non-volatile storage. All "write buttons" are registered in a common
table so that management applications can easily find them. The
table is organized so that sub-agents can register rows in the table
easily. In addition, there is a global "write button" which
basically causes all write buttons in the table to be triggered.
The objects defined in the MIB support slow write transactions where
the time required to commit data to non-volatile storage is much
larger than the time for processing set operations. Status objects
report the progress of writing data to non-volatile storage. A
management application can poll these status objects in order to
detect when the write has completed and whether there were any
errors.
An alternative approach would have been to introduce "write button"
scalars in various MIB modules that use the StorageType textual
convention. However, this leads to serious problems for management
applications to find the right scalars for the right set of MIB
objects. Furthermore, it would be hard to realize a global "write
button" in a master/subagent environment without specific protocol
support.
3. Definitions
SNMP-STORAGE-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, OBJECT-TYPE, snmpModules, Unsigned32
FROM SNMPv2-SMI
DateAndTime, AutonomousType
FROM SNMPv2-TC
MODULE-COMPLIANCE, OBJECT-GROUP
FROM SNMPv2-CONF
SnmpAdminString
FROM SNMP-FRAMEWORK-MIB;
snmpStorageMIB MODULE-IDENTITY
LAST-UPDATED "200106210000Z"
ORGANIZATION "IETF"
CONTACT-INFO
"Juergen Schoenwaelder (Editor)
TU Braunschweig
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Bueltenweg 74/75
38106 Braunschweig, Germany
Phone: +49 531 391-3289
EMail: schoenw@ibr.cs.tu-bs.de
Send comments to <mibs@ops.ietf.org>."
DESCRIPTION
"This MIB modules provides objects that allow management
applications to commit non-volatile conceptual rows to
stable storage."
REVISION "200106210000Z"
DESCRIPTION "The initial revision, published as RFC XXXX."
::= { snmpModules xxx }
snmpStorageObjects OBJECT IDENTIFIER ::= { snmpStorageMIB 1 }
snmpStorageConformance OBJECT IDENTIFIER ::= { snmpStorageMIB 2 }
snmpStorageGlobControl OBJECT-TYPE
SYNTAX INTEGER { nop(1), write(2) }
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"Setting this object to write(2) causes the agent to sync
not yet committed non-volatile MIB data to stable storage.
Setting this object to write(2) while the value of the
snmpStorageGlobStatus object is writing(3) leads to an
inconsitent value error.
Setting this object to nop(1) always succeeds and has no
effect.
Management applications are advised to make use of the
snmpSetSerialNo object defined in the SNMPv2-MIB to
coordinate their use of this object."
::= { snmpStorageObjects 1 }
snmpStorageGlobStatus OBJECT-TYPE
SYNTAX INTEGER {
other(1),
dirty(2), -- can probably not be implemented ?
writing(3), -- perhaps we only need 'idle' and
finished(4), -- 'inProgress'?
error(5)
}
MAX-ACCESS read-only
STATUS current
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DESCRIPTION
"This object reports the current status of the write operation."
::= { snmpStorageObjects 2 }
snmpStorageGlobError OBJECT-TYPE
SYNTAX SnmpAdminString
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"This object contains a descriptive error message if the
last attempt to write global stable storage has failed."
::= { snmpStorageObjects 3 }
snmpStorageGlobErrorTime OBJECT-TYPE
SYNTAX DateAndTime
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The data and time when the snmpStorageGlobError was last
updated. The value '0000000000000000'H is returned if
snmpStorageGlobError has not yet been updated after the
initialization."
::= { snmpStorageObjects 4 }
snmpStorageTable OBJECT-TYPE
SYNTAX SEQUENCE OF SnmpStorageEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
""
::= { snmpStorageObjects 5 }
snmpStorageEntry OBJECT-TYPE
SYNTAX SnmpStorageEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
""
INDEX { snmpStorageIndex }
::= { snmpStorageTable 1 }
SnmpStorageEntry ::= SEQUENCE {
snmpStorageIndex Unsigned32,
snmpStorageDescr SnmpAdminString,
snmpStorageID AutonomousType,
snmpStorageControl INTEGER,
snmpStorageStatus INTEGER,
snmpStorageError SnmpAdminString,
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snmpStorageErrorTime DateAndTime
}
snmpStorageIndex OBJECT-TYPE
SYNTAX Unsigned32 (1..4294967295)
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The index which uniquely identifies a row in the
snmpStorageTable."
::= { snmpStorageEntry 1 }
snmpStorageDescr OBJECT-TYPE
SYNTAX SnmpAdminString
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"A textual description which explains the scope of
MIB data which is controlled by this row."
::= { snmpStorageEntry 2 }
snmpStorageID OBJECT-TYPE
SYNTAX AutonomousType
MAX-ACCESS read-only
STATUS current
DESCRIPTION
""
::= { snmpStorageEntry 3 }
snmpStorageControl OBJECT-TYPE
SYNTAX INTEGER { nop(1), write(2) }
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"Setting this object to write(2) causes the agent to sync
not yet committed non-volatile MIB data to stable storage.
Setting this object to write(2) while the value of the
snmpStorageStatus object is writing(3) leads to an
inconsitent value error.
Setting this object to nop(1) always succeeds and has no
effect.
Management applications are advised to make use of the
snmpSetSerialNo object defined in the SNMPv2-MIB to
coordinate their use of this object."
::= { snmpStorageEntry 4 }
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snmpStorageStatus OBJECT-TYPE
SYNTAX INTEGER {
other(1),
dirty(2),
writing(3),
finished(4),
error(5)
}
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"This object reports the current status of the write operation."
::= { snmpStorageEntry 5 }
snmpStorageError OBJECT-TYPE
SYNTAX SnmpAdminString
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"This object contains a descriptive error message if the
last attempt to write into stable storage has failed."
::= { snmpStorageEntry 6 }
snmpStorageErrorTime OBJECT-TYPE
SYNTAX DateAndTime
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The data and time when the snmpStorageError was last
updated. The value '0000000000000000'H is returned if
snmpStorageError has not yet been updated after the
initialization."
::= { snmpStorageEntry 7 }
snmpStorageCompliances OBJECT IDENTIFIER ::= { snmpStorageConformance 1 }
snmpStorageGroups OBJECT IDENTIFIER ::= { snmpStorageConformance 2 }
snmpStorageCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
""
MODULE -- this module
MANDATORY-GROUPS { snmpStorageGlobalGroup }
GROUP snmpStorageGroup
DESCRIPTION
"Implementation of this group is only mandatory for
systems that support multiple write buttons for
different sets of MIB objects."
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::= { snmpStorageCompliances 1 }
snmpStorageGlobalGroup OBJECT-GROUP
OBJECTS { snmpStorageGlobControl, snmpStorageGlobStatus,
snmpStorageGlobError, snmpStorageGlobErrorTime }
STATUS current
DESCRIPTION
""
::= { snmpStorageGroups 1 }
snmpStorageGroup OBJECT-GROUP
OBJECTS { snmpStorageDescr, snmpStorageID,
snmpStorageControl, snmpStorageStatus,
snmpStorageError, snmpStorageErrorTime }
STATUS current
DESCRIPTION
""
::= { snmpStorageGroups 2 }
END
4. Security Considerations
There are a number of management objects defined in this MIB that
have a MAX-ACCESS clause of read-write and/or read-create. Such
objects may be considered sensitive or vulnerable in some network
environments. The support for SET operations in a non-secure
environment without proper protection can have a negative effect on
network operations.
SNMPv1 by itself is not a secure environment. Even if the network
itself is secure (for example by using IPSec), even then, there is no
control as to who on the secure network is allowed to access and
GET/SET (read/change/create/delete) the objects in this MIB.
It is recommended that the implementers consider the security
features as provided by the SNMPv3 framework. Specifically, the use
of the User-based Security Model RFC 2574 [RFC2574] and the View-
based Access Control Model RFC 2575 [RFC2575] is recommended.
It is then a customer/user responsibility to ensure that the SNMP
entity giving access to an instance of this MIB, is properly
configured to give access to the objects only to those principals
(users) that have legitimate rights to indeed GET or SET
(change/create/delete) them.
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5. Acknowledgments
The author would like to thank David Harrington, Jon Saperia, Steve
Waldbusser for their comments and suggestions.
6. Intellectual Property Notice
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
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claims of rights made available for publication and any assurances of
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obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Harrington, D., Presuhn, R. and B. Wijnen, "An Architecture for
Describing SNMP Management Frameworks", RFC 2571, April 1999.
[3] Rose, M. and K. McCloghrie, "Structure and Identification of
Management Information for TCP/IP-based Internets", STD 16, RFC
1155, May 1990.
[4] Rose, M. and K. McCloghrie, "Concise MIB Definitions", STD 16,
RFC 1212, March 1991.
[5] Rose, M., "A Convention for Defining Traps for use with the
SNMP", RFC 1215, March 1991.
[6] 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.
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[7] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
M. and S. Waldbusser, "Textual Conventions for SMIv2", STD 58,
RFC 2579, April 1999.
[8] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
M. and S. Waldbusser, "Conformance Statements for SMIv2", STD
58, RFC 2580, April 1999.
[9] Case, J., Fedor, M., Schoffstall, M. and J. Davin, "A Simple
Network Management Protocol (SNMP)", STD 15, RFC 1157, May
1990.
[10] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
"Introduction to Community-based SNMPv2", RFC 1901, January
1996.
[11] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
"Transport Mappings for Version 2 of the Simple Network
Management Protocol (SNMPv2)", RFC 1906, January 1996.
[12] Case, J., Harrington, D., Presuhn, R. and B. Wijnen, "Message
Processing and Dispatching for the Simple Network Management
Protocol (SNMP)", RFC 2572, April 1999.
[13] Blumenthal, U. and B. Wijnen, "User-based Security Model (USM)
for version 3 of the Simple Network Management Protocol
(SNMPv3)", RFC 2574, April 1999.
[14] 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.
[15] Levi, D., Meyer, P. and B. Stewart, "SNMP Applications", RFC
2573, April 1999.
[16] Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based Access
Control Model (VACM) for the Simple Network Management Protocol
(SNMP)", RFC 2575, April 1999.
[17] Case, J., Mundy, R., Partain, D. and B. Stewart, "Introduction
to Version 3 of the Internet-standard Network Management
Framework", RFC 2570, April 1999.
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Author's Address
Juergen Schoenwaelder
TU Braunschweig
Bueltenweg 74/75
38106 Braunschweig
Germany
Phone: +49 531 391-3266
EMail: schoenw@ibr.cs.tu-bs.de
Appendix A. Open Issues
o How do we best describe the scope of a write button?
o Should we just provide a TC an simply point to MIB specific
scalars that use this TC?
o Is the error handling mechanism over-designed?
o Do we ever clear the error message like we do it in the DISMAN-
SCRIPT-MIB?
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Full Copyright Statement
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