Subject: snmpconf PM MIB Issue #9

From: Steve Waldbusser <[email-masked]>
Date: Thu, 14 Jun 2001 22:56:54 -0700

The issue states:

=================
* Discussion of permanent storage and configuration update
  implications of the Policy Module on the rest of the system

  Issue: in DiffServ MIB discussions, the use of the StorageType
  TC has been called into question. Specifically, implementors
  said that the granularity used in the DiffServ MIB (storage
  per row) was not realistic in an environment where flash
  was used. We need to look at how we use StorageType to
  determine if it's appropriate for such environments or if
  we need to come up with an alternative approach (perhaps a
  "bigger button" at a higher level of granularity).
=================

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

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

Steve

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Fri, 15 Jun 2001 10:35:41 +0200

>>>>> 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.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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: [email-masked]

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Full Copyright Statement

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
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   or assist in its implementation may be prepared, copied, published
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   The limited permissions granted above are perpetual and will not be
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   This document and the information contained herein is provided on an
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   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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

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---

From: Jon Saperia <[email-masked]>
Date: Fri, 15 Jun 2001 07:59:11 -0400

After thinking about this more, I am not sure we should create a new mechanism 
just for this MIB Module. We could use a technique with regard to the storage 
of polices/tables that I have successfully used in several products that Steve 
mentions below. Specifically we create a couple of scalar objects that allow 
the user to set the granularity of 'saving' to permanent storage. The simplest 
case is a single button for the entire PM MIB module to update all changes. 
Finer granularity is possible. This is about as far as we might go in this MIB 
Module. Future designs should take into account the nvram problem. There are 
others such as the need to commit huge changes all at once.

So my recommendation is that if we feel we must we can put one or two scalar 
update objects into the MIB Module (the script/code storage might be a good 
place). I certainly do not feel strongly about it. The rest is up to the MIB 
designers of DiffServ etc.
/jon

> The issue states:

Thanks,
/jon
--

Jon Saperia		     [email-masked]
			     Phone: 617-744-1079
			     Fax:   617-249-0874
			     http://www.jdscons.com/

---

From: Jon Saperia <[email-masked]>
Date: Fri, 15 Jun 2001 08:07:45 -0400

Juergen,

I like your idea of creating standard write buttons. I believe this would be 
very helpful.

My first reaction though is that you have made this a bit more than it needs 
to be. What I mean is that I do not think we really need a new mib module with 
a table. Your concern about the complexity of many scalars is well taken. My 
concern is that we need to be able to write at many levels of granularity and 
we could approximate with with the table but it would be another 
'registration' task agent implementors would have to deal with. In the end a 
trade of decision.

All that said, we probably want to separate that discussion from the current 
snmpconf discussion. Would this be an appropriate topic for EOS.  I know that 
people on this list are on that one. We should probably move this good 
discussion there or wherever people think appropriate.

/jon

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Fri, 15 Jun 2001 15:20:13 +0200

>>>>> Jon Saperia writes:

Jon> I like your idea of creating standard write buttons. I believe
Jon> this would be very helpful.

Jon> My first reaction though is that you have made this a bit more
Jon> than it needs to be. What I mean is that I do not think we really
Jon> need a new mib module with a table. Your concern about the
Jon> complexity of many scalars is well taken. My concern is that we
Jon> need to be able to write at many levels of granularity and we
Jon> could approximate with with the table but it would be another
Jon> 'registration' task agent implementors would have to deal
Jon> with. In the end a trade of decision.

From a manager's point of view, I would like to know where I can find
all the write buttons for the various MIB modules supported by an
agent (and its third party agent extensions). (This might as well be
handy for policy scripts that try to enforce a certain storage policy.)

Jon> All that said, we probably want to separate that discussion from
Jon> the current snmpconf discussion. Would this be an appropriate
Jon> topic for EOS.  I know that people on this list are on that
Jon> one. We should probably move this good discussion there or
Jon> wherever people think appropriate.

I think EOS if for protocol work. This has nothing to do with the
protocol - it is a MIB infrastructure issue. I think the best place
to discuss this would be <[email-masked]>. Bert, do you agree?

/js

-- 
Juergen Schoenwaelder      Technical University Braunschweig
<[email-masked]>  Dept. Operating Systems & Computer Networks
Phone: +49 531 391 3289    Bueltenweg 74/75, 38106 Braunschweig, Germany
Fax:   +49 531 391 5936    <URL:http://www.ibr.cs.tu-bs.de/~schoenw/>

---

From: Jon Saperia <[email-masked]>
Date: Fri, 15 Jun 2001 09:39:45 -0400

Hi Juergen. I think you are probably right, this may be more of an 
infrastructure issue. So I copied the mibs@ops list. Lets move this discussion 
there.
/jon

Thanks,
/jon
--

---

From: Steve Waldbusser <[email-masked]>
Date: Tue, 19 Jun 2001 09:29:11 -0700

Thanks for this.

I think this is a good approach for a generalized solution. It works
kindof like sync() except that you get more granularity.

One of my questions was whether per-row granularity was important. It
seems the more popular strategy is to have per-row granularity thru
storageType and then the write buttons write only those that are
nonVolatile. Thus we should leave in storageType.

The other question is how we should get the write buttons? We could:
1) Do nothing and wait for the storage-type MIB to clarify the PM MIB in
the same way as it will clarify all other existing use of storageType.
(This doesn't add any dependence on the completion of the storage type
MIB).
2) Add a scalar to the PM MIB that writes all nonVolatile entries

Comments?

Steve

---

From: David Harrington <[email-masked]>
Date: Tue, 19 Jun 2001 14:44:21 -0400

Hi,

Would it be a reasonable compromise to have the StorageTable contain a
VariablePointer to a scalar that is the StorageControl for a specific
mib module?

Then simply define some guidelines about how a StorageControl scalar
pointed to by this table should be defined, possibly by using another
standard TC, such as a TruthValue (StoragePleaseWriteNow).

dbh

-- 
---
David Harrington            Network Management Standards Architect
[email-masked]           Office of the CTO
+1 603 337 2614 - voice     Enterasys Networks
+1 603 332 1524 - fax       Rochester NH, USA

---

From: Wes Hardaker <[email-masked]>
Date: 19 Jun 2001 12:08:13 -0700

Steve> 2) Add a scalar to the PM MIB that writes all nonVolatile entries

Steve> Comments?

I'm not convinced that forcing this upon the implementer is a "good
thing".  It's entirely possible that some implementations will only be
able to write immediately, and others will not be able to write until
some time X later.

I fail to see what the problem is with the existing storage type
mechanisms.  If one box must write everything nonVolatile at once and
another one may not, then it is sort of implementation specific as to
what saving methodology is used.

-- 
Wes Hardaker
NAI Labs
Network Associates

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Wed, 20 Jun 2001 10:51:49 +0200

>>>>> Wes Hardaker writes:

Wes> I'm not convinced that forcing this upon the implementer is a
Wes> "good thing".  It's entirely possible that some implementations
Wes> will only be able to write immediately, and others will not be
Wes> able to write until some time X later.

Which means that management applications can never know whether a
configuration change has been committed to stable storage. From a
management application perspective, this is unworkable. (And all the
CLIs I have seen sofar have a "write config now" button. So why is
that too hard to put into an SNMP agent?)

Wes> I fail to see what the problem is with the existing storage type
Wes> mechanisms.  If one box must write everything nonVolatile at once
Wes> and another one may not, then it is sort of implementation
Wes> specific as to what saving methodology is used.

The problem is that management applications have no clue when a
configuration change is reflected in stable storage and hence they
can't seriously make any assumptions that a row which is "nonVolatile"
is still there after a device reboot/crash. I know one implementation
which writes to stable storage when the agent exits (which won't work
if the agent or the system crashes). I know other implementations
which delay writes to speed up the processing of SNMP set
operations. Again, there is a time window where changes to
"nonVolatile" rows might get lost.

The proposal adds explicit write buttons so when a management
application touches the button, it will be sure that the configuration
in stable storage is updated. This does not reduce your freedom to not
implement such a write button and to continue with the old behaviour
where things are written to stable storage whenever the implementor
things it is a good time to do so.

In fact, the write buttons would be an _additional_ explicit mechanism
to help management applications that want to know when configuration
changes are saved in stable storage.

/js

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Wed, 20 Jun 2001 11:04:12 +0200

>>>>> David Harrington writes:

David> Would it be a reasonable compromise to have the StorageTable
David> contain a VariablePointer to a scalar that is the
David> StorageControl for a specific mib module?

David> Then simply define some guidelines about how a StorageControl
David> scalar pointed to by this table should be defined, possibly by
David> using another standard TC, such as a TruthValue
David> (StoragePleaseWriteNow).

The snmpStorageTable might look too complex to some of you. However,
it does a number of things:

(a) Allows to find write buttons in a single place

(b) Supports asynchronous write operations (the set operations on
    snmpStorageControl return before the write operation is complete
    while the snmpStorageStatus reports the progress - which is a
    good thing to have on systems that save configuration data in
    slow memory)

(c) Error reporting (snmpStorageError, snmpStorageErrorTime)

(d) Identification of the "MIB zone" to be written to stable storage
    by using the snmpStorageID.

Write operation on the write buttons probably should require the use
of snmpSetSerialNo to prevent multiple managers to step on each other
or there should be a specific TestAndIncr object only for this MIB.

You can of course make simpler solutions by giving up some of the
features listed above - and a MIB specific scalar gives up all the
features listed above.

/js

---

From: David Harrington <[email-masked]>
Date: Wed, 20 Jun 2001 09:02:14 -0400

Hi,

I think a status object should indicate when a write has taken place.
This could be done on a row-by-row basis if the buttons are row-by-row,
or table by table if the buttons are by table, etc.
If it is likely that a table may get "dirty" so soon, that th euser may
not be able to see the change, then maybe there should be a timestamp
(based on sysUpTime) object to indicate when teh write occurred. The
write button makes the request; the timestamp indictaes when it is
completed; the status button shows whether the row is again dirty.

I think this is a useful thing. A few months ago on this list a security
hole was identified that, it turns out, was caused by the lack of an
immediate write. It is a good thing to know whether a write to stable
storage has been done or not.

dbh

---

From: Steve Waldbusser <[email-masked]>
Date: Wed, 20 Jun 2001 17:17:04 -0700

I believe Juergen's proposal gives the flexibility that the write can be
done early but it must be complete by the time the button push is
complete in the snmpStorage MIB. In other words, it's like syncing a
file system. Prior to the sync the application knows that things *might*
have been written to disk but there is no guarantee. The sync can't
complete until any unwritten data is written. After the sync the app has
a guarantee that the data is written.

This adapts to multiple strategies, including:
1) Write to nvram immediately on activating the target row (sync is a
no-op)
2) Every N seconds, look for unwritten rows and write them (sync only
writes rows that have been modified since last interval)
3) Delay writes until sync button is pushed

I also agree with Juergen's point that if an agent did #1 for a given
target table, it wouldn't necessarily add an entry to the snmpStorage
table for that target table. This gives such an agent another option.

My main question is, given that there's no way for Juergen's proposal to
be standardized before the PM MIB, how do we proceed now? We could:

Steve

---

From: Jon Saperia <[email-masked]>
Date: Thu, 21 Jun 2001 07:51:37 -0400

> (This doesn't add any dependence on the completion of the storage type

Clarification in another document that does not hold up our work is
great. There are of course other mechanisms in Juegens proposal that
will also help - but down the road. For that reason I like your
suggestions #2.

> 2) Add a scalar to the PM MIB that writes all nonVolatile entries
One thing to be clear on about this is that the only changes we are
talking about are changes within the PM MIB Objects. That is to say we
are simply writing the objects in the scope of the PM MIB, not waiting
for configuration changes that might or might not be activated as a
result of a policy execution. Those objects are defined in other (mostly
private for now) MIB Objects.
/jon

Thanks,
/jon
--

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Thu, 21 Jun 2001 15:31:35 +0200

>>>>> Jon Saperia writes:

Jon> Clarification in another document that does not hold up our work
Jon> is great. There are of course other mechanisms in Juegens
Jon> proposal that will also help - but down the road. For that reason
Jon> I like your suggestions #2.

>> 2) Add a scalar to the PM MIB that writes all nonVolatile entries

Are you saying that there should be StorageType columns or not?

Are you saying a single scalar is all you need and the response on the
set which triggers the write button will be delayed until the data has
actually been committed to stable storage? And how will you report any
errors (or are there by definition no errors when committing data to
stable storage)?

/js

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Thu, 21 Jun 2001 15:42:27 +0200

>>>>> Steve Waldbusser writes:

Steve> I believe Juergen's proposal gives the flexibility that the
Steve> write can be done early but it must be complete by the time the
Steve> button push is complete in the snmpStorage MIB. In other words,
Steve> it's like syncing a file system. Prior to the sync the
Steve> application knows that things *might* have been written to disk
Steve> but there is no guarantee. The sync can't complete until any
Steve> unwritten data is written. After the sync the app has a
Steve> guarantee that the data is written.

Very good summary. Perhaps we should really use the term sync to make
things easier to understand.

Steve> This adapts to multiple strategies, including: 1) Write to
Steve> nvram immediately on activating the target row (sync is a
Steve> no-op) 2) Every N seconds, look for unwritten rows and write
Steve> them (sync only writes rows that have been modified since last
Steve> interval) 3) Delay writes until sync button is pushed

Option 3) is a bit problematic with the current StorageType. Right
now, applications assume that setting the StorageType to nonVolatile
is enough to put the configuration information into stable storage,
even though it is right now implementation specific when this actually
happens. But it should happen at some point in time. So only relying
on the sync button might confuse existing applications that do not
know about sync buttons. So if 3) is an option we want, then we
probably need to have a new StorageType kind of TC.

[...]

Steve> My main question is, given that there's no way for Juergen's
Steve> proposal to be standardized before the PM MIB, how do we
Steve> proceed now? We could:

Steve> 1) Do nothing and wait for the storage-type MIB to clarify the
Steve> PM MIB in the same way as it will clarify all other existing
Steve> use of storageType.  (This doesn't add any dependence on the
Steve> completion of the storage type MIB).

Steve> 2) Add a scalar to the PM MIB that writes all nonVolatile
Steve> entries

If we can get agreement on the storage type MIB approach quickly (and
the problem is IMHO not really that complicated), then option 1) seems
most reasonable in the longer term perspective. Even if this WG
decides to go with the scalar approach, it would be desirable to
define a generic TC which defines all the semantics needed for such
a sync button so that it can be reused.

/js

---

From: Jon Saperia <[email-masked]>
Date: Thu, 21 Jun 2001 09:45:47 -0400

> errors (or are there by definition no errors when committing data to

I think all the following sematincs are needed:

  1. The 'storage type' which is the current equivalent in CLI land of is
this change a permanent change (e.g,. to disk or nvram) or is this a
temporary change. This of course is only on a per row basis so we need a
'larger scale' set of objects in most MIB modules.

  2.  The 'make it so' button. This is make the change active in the
memory system specified above.

  3.  We need to have objects that control the scope of the action,
e.g., which rows, tables, and their relationships as a general rule. For
example in a bandwidth management system, many rows in many tables might
need to go into effect simultaneously. Same is true for routing
protocols. 

The policy module does not need a lot of this because relatively
speaking it is not that complex. It does need some. I wrote this more
for the larger picture. 

The short answer to your question is that I think both a storage type
and 'make it so' buttons are helpful in the pm case.

/jon

Thanks,
/jon
--

---

From: Jon Saperia <[email-masked]>
Date: Thu, 21 Jun 2001 09:47:53 -0400

> probably need to have a new StorageType kind of TC.

Option three is an important sematic. To what applications do you refer?

> a sync button so that it can be reused.
Juergen as long as do nothing to tie the pm module to this other work, I am OK.

Thanks,
/jon
--

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Thu, 21 Jun 2001 16:02:28 +0200

>> now, applications assume that setting the StorageType to
>> nonVolatile is enough to put the configuration information into
>> stable storage, even though it is right now implementation specific
>> when this actually happens. But it should happen at some point in
>> time. So only relying on the sync button might confuse existing
>> applications that do not know about sync buttons. So if 3) is an
>> option we want, then we probably need to have a new StorageType
>> kind of TC.
>> 

Jon> Option three is an important sematic. To what applications do you
Jon> refer?

Lets take a management application which configures SNMPv3 users or
access control. Such an application (which I assume exists) will set
the relevant RowStatus objects to nonVolatile and it will be done.

If now someone implements StorageType objects (e.g. SNMPv3 user and
access control tables) which are never written to stable storage
unless you press a magic new sync button, then the manager I was
talking about will screw up since it can not know that it has to press
a sync button.

So if we continue with the existing StorageType TC (which has some
value since several of our MIBs already use it), then the behaviour
described in option 3) above does not work - at least for the set of
already published MIBs.

(In fact, we probably need a requirement that StorageType descriptions
 must clearly say how managers can identify sync buttons.)

/js

---

From: Jon Saperia <[email-masked]>
Date: Thu, 21 Jun 2001 12:11:43 -0400

>  must clearly say how managers can identify sync buttons.)
Juergen, lets not optimize for the wrong thing. I would rather move
forward with the requried semantic. This is really needed for
configuration and is much more important than protecting any extant
applications.

/jon

Thanks,
/jon
--

---

From: Steve Waldbusser <[email-masked]>
Date: Thu, 21 Jun 2001 13:14:56 -0700

> probably need to have a new StorageType kind of TC.

Good point. 

BTW, I'm not pushing for #3 and I've never heard that anyone needed it,
so it is not a requirement.

Steve

---

From: Jon Saperia <[email-masked]>
Date: Fri, 22 Jun 2001 07:44:45 -0400

> so it is not a requirement.

I am pushing it as a requirement. It is how the operators control their 
network.
That said, I am not pushing it for the PM module, just for the infrastructure 
work that Juergen is doing.

Thanks,
/jon
--

---

From: Matt White <[email-masked]>
Date: Fri, 22 Jun 2001 11:38:07 -0400

One thing to keep in mind here is that configuration for next generation 
devices can become quite large.  It is quite likely that configuration 
cannot be written prior to SNMP timeout.  If I take the UCD tools as my 
model, the SET request will be sent again, thus causing more work.

I'm not saying that you can't have a "write this now" button, just that you 
need to do something a little bit smarter than a single MIB object.

-Matt

---

From: Matt White <[email-masked]>
Date: Fri, 22 Jun 2001 11:44:56 -0400

Agreed.  Regardless of the semantics of the write button, it seems that 
dirty bit is required.

-Matt

---

From: Steve Waldbusser <[email-masked]>
Date: Fri, 22 Jun 2001 09:06:30 -0700

> I am pushing it as a requirement. It is how the operators control their

I really meant as a required semantic for storageType. I don't know that
we can stretch storageType this far and I've never seen anyone ask us to
stretch it that far (never asked either). Mostly I didn't want to make
it seem like *I* was making it a requirement.

I agree that "write config" is how operators control their network, or
rather: that's the tool that router vendors provide for their customers
to control their network.

Steve

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Sat, 23 Jun 2001 17:13:34 +0200

>>>>> Matt White writes:

Matt> One thing to keep in mind here is that configuration for next
Matt> generation devices can become quite large.  It is quite likely
Matt> that configuration cannot be written prior to SNMP timeout.  If
Matt> I take the UCD tools as my model, the SET request will be sent
Matt> again, thus causing more work.

The storage type MIB handles this I think.

Matt> I'm not saying that you can't have a "write this now" button,
Matt> just that you need to do something a little bit smarter than a
Matt> single MIB object.

Which I agree with.

/js

---

From: "David T. Perkins" <[email-masked]>
Date: Sun, 24 Jun 2001 22:05:57 -0700

HI,

On these scalar buttons, I'm assuming that when you guys are really
talking about a collection of objects to implement the button. A
write can take a long time, and it can even fail. So you need at
least the three following objects:

  storWrite - action/status object with values:
         - write(1), when written starts a write (if one is not
                     already in progress
         - writing(2), read-only value that is returned while
                     a write to storage is occurring
         - failed(3), read-only value that is returned when
                     the last write to storage failed
         - success(4), read-only value that is returned when
                     the last write to storage succeeded
  storIsNewer - read-only object that indicates if "runtime"
                     newer than stored values
  storSerial - testAndSet object that is incremented each time
                     a write to storage is attempted
Now, you also need to track whether a bulk download from the net
has occurred to storage, which can make the "runtime" and the
stored configuration different. 

Please, don't over simplify this problem. There are a few unusual
cases that happen all the time in the real world.

PS  I don't see how the "scope of the configuration objects" covered
    by a store button can be efficiently specified. (Don't forget
    about contexts.)

>/jon

Regards,
/david t. perkins