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Versions: 00 01 02 03 04 RFC 2856

Internet Draft                                             Andy Bierman
                                                     Cisco Systems, Inc.
                                                       Keith McCloghrie
                                                     Cisco Systems, Inc.
                                                          Randy Presuhn
                                                      BMC Software, Inc.
                                                         22 October 1999


         SMI Extensions for Additional High Capacity Data Types


                    <draft-kzm-hcdata-types-01.txt>





Status of this Memo

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

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

Internet-Drafts are draft documents valid for a maximum of six months
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Distribution of this document is unlimited. Please send comments to the
authors.

1.  Copyright Notice

Copyright (C) The Internet Society (1999).  All Rights Reserved.












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2.  Abstract

This memo specifies clarifications to the Structure of Management
Information [SMIv2] for the purpose of providing a broader range of data
types for high capacity numbers.

3.  Table of Contents

1 Copyright Notice ................................................    1
2 Abstract ........................................................    2
3 Table of Contents ...............................................    2
4 The SNMP Management Framework ...................................    2
5 Overview ........................................................    3
5.1 New Data Types Needed .........................................    3
5.2 Short Term and Long Term Objectives ...........................    3
5.3 Backward Compatibility with Counter64 .........................    5
5.4 ASN.1 Vs. Textual Convention Approach .........................    5
5.5 SMI Interpretation Supporting the TC Approach .................    5
6 Definitions .....................................................    7
7 Intellectual Property ...........................................    8
8 References ......................................................    8
9 Security Considerations .........................................   11
10 Authors' Addresses .............................................   12
11 Full Copyright Statement .......................................   13

4.  The SNMP Management Framework

   The SNMP Management Framework presently consists of five major
   components:

    o   An overall architecture, described in RFC 2571 [RFC2571].

    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
        RFC 1155 [RFC1155], RFC 1212 [RFC1212] and RFC 1215 [RFC1215].
        The second version, called SMIv2, is described in RFC 2578
        [RFC2578], RFC 2579 [RFC2579] and RFC 2580 [RFC2580].

    o   Message protocols for transferring management information. The
        first version of the SNMP message protocol is called SNMPv1 and
        described in RFC 1157 [RFC1157]. A second version of the SNMP
        message protocol, which is not an Internet standards track
        protocol, is called SNMPv2c and described in RFC 1901 [RFC1901]
        and RFC 1906 [RFC1906]. The third version of the message





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        protocol is called SNMPv3 and described in RFC 1906 [RFC1906],
        RFC 2572 [RFC2572] and RFC 2574 [RFC2574].

    o   Protocol operations for accessing management information. The
        first set of protocol operations and associated PDU formats is
        described in RFC 1157 [RFC1157]. A second set of protocol
        operations and associated PDU formats is described in RFC 1905
        [RFC1905].

    o   A set of fundamental applications described in RFC 2573
        [RFC2573] and the view-based access control mechanism described
        in RFC 2575 [RFC2575].

   A more detailed introduction to the current SNMP Management Framework
   can be found in RFC 2570 [RFC2570].

   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 document does not define a MIB module.

5.  Overview

There is a need for a standardized way of representing different types
of high capacity numbers in MIB modules, in a manner suitable for use
with existing SNMP engines.  The SMIv2 [RFC2578] currently contains
support for high-speed counters (i.e., Counter64), but does not contain
support for 64 bit gauges or (signed and unsigned) integers.

5.1.  New Data Types Needed

There are standards track MIBs in progress, which require 64 bit gauges
and integers. There are some MIB features such as polling history or
alarm thresholding, that are supported for 32-bit counters, but not
strictly supported for 64-bit counters.  The SMI does not provide the
right base types or textual conventions for 64-bit data types.  The SMI
is also ambiguous regarding the semantics of a MIB object defined with a
textual convention (TC), instead of a base type.

5.2.  Short Term and Long Term Objectives

In order to support Gigabit Ethernet and other high speed interfaces
properly, the following new data types are needed:






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  - Gauge64

  - Unsigned64

  - Integer64

There is an immediate need to provide Gauge64 and Unsigned64 data types,
similar in semantics to the Gauge32 and Unsigned32 data types.

Signed integers can be stored in two MIB objects (sign and absolute
value) as is done with the usrHistoryTable in the RMON-2 MIB [RFC2021],
so there is not an immediate need for an Integer64 data type. A new
ASN.1 tag for 64-bit integers should be added to the SMI as soon as
possible. This document does not suggest a short-term solution for
signed 64-bit integers.

In the short term, textual conventions defining new unsigned 64-bit data
types need to be defined in a document which augments, but does not
invalidate anything contained in the existing SMI documents. Resolutions
to the ambiguities regarding the use of textual conventions also needs
to be resolved in the short-term.

During IETF WG discussions about progressing the SNMPv2 specifications
(RFCs 1902-1908) to a higher level of the standardization status, the
issue of supporting new SMI data types was deferred to the future.  One
school of thought suggests that such future SMI capability should be a
generalized solution for being able to transition to support any new
data type.  However, the definition of a generalized solution will take
time, both to specify and to get implementations of it deployed.  The
updates to the SMIv2 specified in this memo are not intended to
prejudice the argument about whether such a generalized solution is
needed.

Meanwhile, there is an immediate need to add data types for 64 bit
unsigned numbers, and that these additions be done in a way that will be
supportable by any underlying SNMP engine which already implements
Counter64 MIB objects.

The approach in this memo is motivated by the observation that the SMIv2
specification already specifies two base-level data types (Gauge32 and
Unsigned32) which map onto the same underlying ASN.1 tag, and thus are
indistinguishable when contained in an SNMP packet in transmission.  So,
why not have the additional high capacity data types map onto the same
underlying ASN.1 tag as Counter64, so that they are similarly
indistinguishable when contained in an SNMP packet?





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5.3.  Backward Compatibility with Counter64

In order to be backward compatible with existing implementations of
Counter64, the encoding of Gauge64 and Unsigned64 objects needs to be
identical to the encoding of Counter64 objects, i.e., identified by the
[APPLICATION 6] ASN.1 tag.

5.4.  ASN.1 Vs. Textual Convention Approach

Defining new unsigned data types with textual conventions based on the
Counter64 tag, instead of a new (or other existing) ASN.1 tag has some
advantages and some limitations:

  -  The MAX-ACCESS of the TC must be read-only, because the MAX-ACCESS
     of the underlying Counter64 type is read-only, (as established in
     RFC 2578 clause 7.1.10 [RFC2578]).

  -  No sub-range can be specified on the TC-derived types, because sub-
     ranges are not allowed on Counter64 objects.

  -  No DEFVAL clause can be specified for the TC-derived types, because
     DEFVALs are not allowed on read-only objects.

  -  The TC-derived types cannot be used in an INDEX clause.  This is
     not an important feature, and supporting it would have a
     significant impact on MIB compliers.

  -  Enumerated integers cannot be defined with a value larger than
     2147483647.  This is not an important feature, and supporting it
     would have a significant impact on MIB compliers.

  -  The ASN.1 tag should carry only encoding information, not encoding
     and semantic information. Semantic content should be determined
     entirely by the SYNTAX clause in the MIB object definition.

5.5.  SMI Interpretation Supporting the TC Approach

Clause 3.3 of RFC 2579, 'Mapping of the DESCRIPTION clause' states:

          The DESCRIPTION clause, which must be present, contains a
          textual definition of the textual convention, which provides
          all semantic definitions necessary for implementation, and
          should embody any information which would otherwise be
          communicated in any ASN.1 commentary annotations associated
          with the object.





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Note the use of the word "all".

Clause 3.5 of RFC 2579, 'Mapping of the SYNTAX clause' states:

          The SYNTAX clause, which must be present, defines abstract
          data structure corresponding to the textual convention.  The
          data structure must be one of the alternatives defined in the
          ObjectSyntax CHOICE or the BITS construct (see section 7.1 in
          [2]).  Note that this means that the SYNTAX clause of a
          Textual Convention can not refer to a previously defined
          Textual Convention.

          An extended subset of the full capabilities of ASN.1 (1988)
          sub- typing is allowed, as appropriate to the underlying ASN.1
          type.  Any such restriction on size, range or enumerations
          specified in this clause represents the maximal level of
          support which makes "protocol sense".  Restrictions on sub-
          typing are specified in detail in Section 9 and Appendix A of
          [2].

Note that no mention is made of any underlying data type semantics.
Taken together, these two passages indicate that the unsigned 64-bit TCs
are perfectly legal.

There is a passage in RFC 2579 that hints otherwise is a slightly
ambiguous passage in the introduction:

          When designing a MIB module, it is often useful to define new
          types similar to those defined in the SMI.  In comparison to a
          type defined in the SMI, each of these new types has a
          different name, a similar syntax, but a more precise
          semantics.  ...

The ambiguity depends on how one reads "more precise semantics".  One
could read it in the strict sense of a type hierarchy with inheritance
of semantics, or one could read it in the spirit of clause 3.3, which
states that ALL semantics are in the TC's DESCRIPTION clause.

Therefore, the ambiguity is whether the semantics of the base type
have to be inherited by a new TC based on that underlying type.
I.e., whether a TC based on the Counter64 base type must inherit the
'delta-only' characteristics of Counter64, or whether the description of
the TC can override that. The definitions in section 6 assume that a TC
can override it.






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6.  Definitions

The following textual conventions are defined to support unsigned 64-bit
data types.

SMIv2-HCNUM-EXT DEFINITIONS ::= BEGIN

IMPORTS
    TEXTUAL-CONVENTION
        FROM SNMPv2-TC;


Gauge64 ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION
            "The Gauge64 type represents a non-negative integer, which
            may increase or decrease, but shall never exceed a maximum
            value, nor fall below a minimum value.  The maximum value
            can not be greater than 2^64-1 (18446744073709551615
            decimal), and the minimum value can not be smaller than 0.
            The value of a Gauge64 has its maximum value whenever the
            information being modeled is greater than or equal to its
            maximum value, and has its minimum value whenever the
            information being modeled is smaller than or equal to its
            minimum value.  If the information being modeled
            subsequently decreases below (increases above) the maximum
            (minimum) value, the Gauge64 also decreases (increases).
            (Note that despite of the use of the term "latched" in the
            original definition of this type, it does not become "stuck"
            at its maximum or minimum value.)"
    SYNTAX Counter64


Unsigned64 ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION
            The Unsigned64 type represents integer-valued information
            between 0 and 2^64-1 inclusive (0 to 18446744073709551615
            decimal)."
    SYNTAX Counter64


END







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7.  Intellectual Property

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 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 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.

8.  References

[RFC1155]
     Rose, M., and K. McCloghrie, "Structure and Identification of
     Management Information for TCP/IP-based Internets", RFC 1155, STD
     16, Performance Systems International, Hughes LAN Systems, May
     1990.

[RFC1157]
     Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple Network
     Management Protocol", RFC 1157, STD 15, SNMP Research, Performance
     Systems International, Performance Systems International, MIT
     Laboratory for Computer Science, May 1990.

[RFC1212]
     Rose, M., and K. McCloghrie, "Concise MIB Definitions", RFC 1212,
     STD 16, Performance Systems International, Hughes LAN Systems,
     March 1991.

[RFC1215]
     M. Rose, "A Convention for Defining Traps for use with the SNMP",
     RFC 1215, Performance Systems International, March 1991.






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[RFC1901]
     Case, J., McCloghrie, K., Rose, M., and S. Waldbusser,
     "Introduction to Community-based SNMPv2", RFC 1901, SNMP Research,
     Inc., Cisco Systems, Inc., Dover Beach Consulting, Inc.,
     International Network Services, January 1996.

[RFC1905]
     Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Protocol
     Operations for Version 2 of the Simple Network Management Protocol
     (SNMPv2)", RFC 1905, SNMP Research, Inc., Cisco Systems, Inc.,
     Dover Beach Consulting, Inc., International Network Services,
     January 1996.

[RFC1906]
     Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Transport
     Mappings for Version 2 of the Simple Network Management Protocol
     (SNMPv2)", RFC 1906, SNMP Research, Inc., Cisco Systems, Inc.,
     Dover Beach Consulting, Inc., International Network Services,
     January 1996.

[RFC2021]
     S. Waldbusser, "Remote Network Monitoring MIB (RMON-2)", RFC 2021,
     International Network Services, January 1997.

[RFC2026]
     Bradner, S., "The Internet Standards Process -- Revision 3", RFC
     2026, Harvard University, October, 1996.

[RFC2570]
     Case, J., Mundy, R., Partain, D., and B. Stewart, "Introduction to
     Version 3 of the Internet-standard Network Management Framework",
     RFC 2570, SNMP Research, Inc., TIS Labs at Network Associates,
     Inc., Ericsson, Cisco Systems, April 1999.

[RFC2571]
     Harrington, D., Presuhn, R., and B. Wijnen, "An Architecture for
     Describing SNMP Management Frameworks", RFC 2571, Cabletron
     Systems, Inc., BMC Software, Inc., IBM T. J. Watson Research, April
     1999.

[RFC2572]
     Case, J., Harrington D., Presuhn R., and B. Wijnen, "Message
     Processing and Dispatching for the Simple Network Management
     Protocol (SNMP)", RFC 2572, SNMP Research, Inc., Cabletron Systems,
     Inc., BMC Software, Inc., IBM T. J. Watson Research, April 1999.





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[RFC2573]
     Levi, D., Meyer, P., and B. Stewart, "SNMPv3 Applications", RFC
     2573, SNMP Research, Inc., Secure Computing Corporation, Cisco
     Systems, April 1999.

[RFC2574]
     Blumenthal, U., and B. Wijnen, "User-based Security Model (USM) for
     version 3 of the Simple Network Management Protocol (SNMPv3)", RFC
     2574, IBM T. J. Watson Research, April 1999.

[RFC2575]
     Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based Access
     Control Model (VACM) for the Simple Network Management Protocol
     (SNMP)", RFC 2575, IBM T. J. Watson Research, BMC Software, Inc.,
     Cisco Systems, Inc., April 1999.

[RFC2578]
     McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.,
     and S. Waldbusser, "Structure of Management Information Version 2
     (SMIv2)", RFC 2578, STD 58, Cisco Systems, SNMPinfo, TU
     Braunschweig, SNMP Research, First Virtual Holdings, International
     Network Services, April 1999.

[RFC2579]
     McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.,
     and S. Waldbusser, "Textual Conventions for SMIv2", RFC 2579, STD
     58, Cisco Systems, SNMPinfo, TU Braunschweig, SNMP Research, First
     Virtual Holdings, International Network Services, April 1999.

[RFC2580]
     McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.,
     and S. Waldbusser, "Conformance Statements for SMIv2", RFC 2580,
     STD 58, Cisco Systems, SNMPinfo, TU Braunschweig, SNMP Research,
     First Virtual Holdings, International Network Services, April 1999.
















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9.  Security Considerations

There are no security issues raised by this document.















































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10.  Authors' Addresses

     Andy Bierman
     Cisco Systems, Inc.
     170 West Tasman Drive
     San Jose, CA 95134 USA
     Phone: +1 408-527-3711
     Email: abierman@cisco.com

     Keith McCloghrie
     Cisco Systems, Inc.
     170 West Tasman Drive
     San Jose, CA 95134 USA
     Phone: +1 408-526-5260
     Email: kzm@cisco.com

     Randy Presuhn
     BMC Software, Inc.
     1190 Saratoga Avenue
     Suite 130
     San Jose, CA 95129 USA
     Phone: +1 408-556-0720
     EMail: rpresuhn@bmc.com



























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11.  Full Copyright Statement

Copyright (C) The Internet Society (1999).  All Rights Reserved.

This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it or
assist in its implementation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are included
on all such copies and derivative works.  However, this document itself
may not be modified in any way, such as by removing the copyright notice
or references to the Internet Society or other Internet organizations,
except as needed for the purpose of developing Internet standards in
which case the procedures for copyrights defined in the Internet
Standards process must be followed, or as required to translate it into
languages other than English.

The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an "AS
IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR
FITNESS FOR A PARTICULAR PURPOSE."
























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