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Re: snmpconf PM MIB Issue #9




>>>>> Steve Waldbusser writes:

Steve> I'm happy to replace storage type with another mechanism but
Steve> I'd rather not invent it from scratch given that I've never
Steve> personally had experience with this problem myself. Is there a
Steve> generally-accepted solution to this problem? A single
Steve> write-everything-to-nvram button? Or keep (son of) storage-type
Steve> and add a button that only writes all storage-type=nonvolatile
Steve> rows?

Steve> If this happens to just be a DiffServ issue, I hope someone
Steve> will speak up. The PM MIB is designed to go well beyond
Steve> DiffServ.

One can argue that the StorageType definition is vague as it does not
clearly spell out when new values are written to non-volatile
storage.

I know from talking to various people that implementors use different
strategies to implement StorageType. I started work on an ID which
"clarifies" the behaviour of the StorageType TC and adds some new MIB
objects that give you a central set of "write buttons". I never got
around to post the ID since I wanted to get more feedback first.

Feedback is welcome and if people think this is a good approach, then
I am willing to push this forward.

/js



Network Working Group                                   J. Schoenwaelder
Internet-Draft                                           TU Braunschweig
Expires: October 2, 2001                                   April 3, 2001


                            Storage Type MIB
                     draft-schoenw-storage-type-00

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Drafts.

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   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on October 2, 2001.

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 to non-volatile memory.  This memo
   addresses this question and provides a storage MIB module which can
   be used to control when non-volatile rows are actually written to
   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  . . . . . . . . . . . . . . . . . . .   9
   5. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .   9
   6. Intellectual Property Notice . . . . . . . . . . . . . . . . .   9
      References . . . . . . . . . . . . . . . . . . . . . . . . . .  10
      Author's Address . . . . . . . . . . . . . . . . . . . . . . .  11
      Full Copyright Statement . . . . . . . . . . . . . . . . . . .  12








































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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 how conceptual rows are stored in memory.  Several MIBs
   on the standards-track use this StorageType for 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 interpretation is that rows must be writen to
   non-volatile storage on each set operation on one of the columnar
   objects.  However, many implementations prefer to not write to non-
   volatile storage on each set operation.  There are two main reasons
   for this behavior:

   1.  Writing non-volatile storage is on some systems too time
       consuming to do it during the set operation itself.



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   2.  Writing non-volatile storage on every single set of a non-
       volatile variable is too costly on systems that can only backup
       complex system configurations.

   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, incomplete conceptual
       rows are not saved in non-volatile storage until they are
       complete and activated.)

   It seems that delayed writes to non-volatile storage are common
   practice.  However, since this behaviour is right now completely
   implementation dependent, there is no simple way for a management
   application 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 also follow
   a paradigm where explicit commands trigger the storage of the device
   configuration (or logical parts of the configuration) in stable
   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
   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



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   easily.  In addition, there is a global "write button" which
   basically causes all write buttons in the table to be triggered.

   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

       SnmpAdminString
           FROM SNMP-FRAMEWORK-MIB;

   snmpStorageMIB MODULE-IDENTITY
       LAST-UPDATED "200104020000Z"
       ORGANIZATION "IETF"
       CONTACT-INFO
   	""
       DESCRIPTION
   	""
       REVISION    "200104020000Z"
       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



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   	"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
   		    done(4)		-- 'inProgress'?
   		}
       MAX-ACCESS	read-only
       STATUS	current
       DESCRIPTION
   	"This object ..."
       ::= { 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



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       DESCRIPTION
   	""
       ::= { snmpStorageTable 1 }

   SnmpStorageEntry ::= SEQUENCE {
       snmpStorageIndex		Unsigned32,
       snmpStorageDescr		SnmpAdminString,
       snmpStorageID		AutonomousType,
       snmpStorageControl		INTEGER,
       snmpStorageStatus		INTEGER,
       snmpStorageError		SnmpAdminString,
       snmpStorageErrorTime	DateAndTime
   }

   snmpStorageIndex OBJECT-TYPE
       SYNTAX	Unsigned32
       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
   	""
       ::= { 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
   	""
       ::= { snmpStorageEntry 4 }

   snmpStorageStatus OBJECT-TYPE



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       SYNTAX	INTEGER { other(1), dirty(2), writing(3), done(4) }
       MAX-ACCESS	read-only
       STATUS	current
       DESCRIPTION
   	""
       ::= { snmpStorageEntry 5 }

   snmpStorageError OBJECT-TYPE
       SYNTAX	SnmpAdminString
       MAX-ACCESS	read-only
       STATUS	current
       DESCRIPTION
   	""
       ::= { snmpStorageEntry 6 }

   snmpStorageErrorTime OBJECT-TYPE
       SYNTAX	DateAndTime
       MAX-ACCESS	read-only
       STATUS	current
       DESCRIPTION
           ""
       ::= { snmpStorageEntry 7 }

   -- XXX Spell out conformance definitions. Just say that the
   -- snmpStorageTable is not required on systems that need only
   -- a single "write button".

   END


4. Security Considerations

   ...

5. Acknowledgments

   ...

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
   standards-related documentation can be found in BCP-11.  Copies of



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   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such propritary
   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.

   [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



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         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.


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











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Full Copyright Statement

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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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