Network Working Group A. Bierman

Network Working Group A. Bierman
Request for Comments: 2856 K. McCloghrie
Category: Standards Track Cisco Systems, Inc.
R. Presuhn
BMC Software, Inc.
June 2000

Textual Conventions for Additional High Capacity Data Types

Status of this Memo

This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2000). All Rights Reserved.

Abstract

This memo specifies new textual conventions for additional high
capacity data types, intended for SNMP implementations which already
support the Counter64 data type. The definitions contained in this
document represent a short term solution which may be deprecated in
the future.

Table of Contents

1 The SNMP Management Framework ................................. 2
2 Overview ...................................................... 3
2.1 Short Term and Long Term Objectives ......................... 3
2.2 Limitations of the Textual Convention Approach .............. 3
3 New Textual Conventions ....................................... 4
3.1 CounterBasedGauge64 ......................................... 4
3.2 ZeroBasedCounter64 .......................................... 4
4 Definitions ................................................... 4
5 Intellectual Property ......................................... 7
6 References .................................................... 7
7 Security Considerations ....................................... 9
8 Authors' Addresses ............................................ 9
9 Full Copyright Statement ...................................... 10

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RFC 2856 High Capacity Data Types June 2000

1. 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 STD
16, RFC 1155 [RFC1155], STD 16, RFC 1212 [RFC1212] and RFC 1215
[RFC1215]. The second version, called SMIv2, is described in STD
58, RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58,
RFC 2580 [RFC2580].

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 [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
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 STD 15, 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 memo specifies a MIB module that is compliant to the SMIv2. The
textual conventions defined in this MIB module cannot be translated
to SMIv1 since the Counter64 type does not exist in SMIv1.

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2. Overview

The Structure of Management Information [RFC2578] does not explicitly
address the question of how to represent integer objects other than
counters that would require up to 64 bits to provide the necessary
range and precision. There are MIBs in progress targeted for the
standards track, which need such data types. This memo specifies a
short term solution, using textual conventions, to meet these needs.

2.1. Short Term and Long Term Objectives

There is an immediate need to provide a Gauge64 data type, similar in
semantics to the Gauge32 data type, in order to support common data
representations such as:

- a snapshot of a Counter64 at a given moment, e.g., history ring
buffer

- the difference between two Counter64 values

There is also an immediate need for a 64-bit zero-based counter type,
similar in semantics to the ZeroBasedCounter32 TC defined in the
RMON-2 MIB [RFC2021].

Both of these textual conventions should use a base type of Gauge64
or Unsigned64, but such a base type is not available. Until such a
base type is defined and deployed, these temporary textual
conventions (which use a base type of Counter64) will be used in MIBs
which require unsigned 64-bit data types.

In order to be backward compatible with existing implementations of
Counter64, the ASN.1 encoding of unsigned 64-bit data types must be
identical to the encoding of Counter64 objects, i.e., identified by
the [APPLICATION 6] ASN.1 tag.

Note that the textual conventions defined in this document represent
a limited and short-term solution to the problem. These textual
conventions may be deprecated as a long term solution is defined and
deployed to replace them. A MIB object which uses either of these
textual conventions may also eventually have to be deprecated.

2.2. Limitations of the Textual Convention Approach

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

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RFC 2856 High Capacity Data Types June 2000

- The MAX-ACCESS of the TC must be read-only, because the MAX-ACCESS
of the underlying Counter64 type is read-only.

- 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 Counter64 objects.

- The TC-derived types cannot be used in an INDEX clause, because
there is no INDEX clause mapping defined for objects of type
Counter64.

3. New Textual Conventions

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

3.1. CounterBasedGauge64

This textual convention defines a 64-bit gauge, but defined with
Counter64 syntax, since no Gauge64 or Unsigned64 base type is
available in SMIv2.

This TC is used for storing the difference between two Counter64
values, or simply storing a snapshot of a Counter64 value at a given
moment in time.

3.2. ZeroBasedCounter64

This textual convention defines a 64-bit counter with an initial
value of zero, instead of an arbitrary initial value.

This TC is used for counter objects in tables which are instantiated
by management application action.

4. Definitions

HCNUM-TC DEFINITIONS ::= BEGIN

IMPORTS
MODULE-IDENTITY, mib-2, Counter64
FROM SNMPv2-SMI
TEXTUAL-CONVENTION
FROM SNMPv2-TC;

hcnumTC MODULE-IDENTITY
LAST-UPDATED "200006080000Z"

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RFC 2856 High Capacity Data Types June 2000

ORGANIZATION "IETF OPS Area"
CONTACT-INFO
" E-mail: [email protected]
Subscribe: [email protected]
with msg body: subscribe mibs

Andy Bierman
Cisco Systems Inc.
170 West Tasman Drive
San Jose, CA 95134 USA
+1 408-527-3711
[email protected]

Keith McCloghrie
Cisco Systems Inc.
170 West Tasman Drive
San Jose, CA 95134 USA
+1 408-526-5260
[email protected]

Randy Presuhn
BMC Software, Inc.
Office 1-3141
2141 North First Street
San Jose, California 95131 USA
+1 408 546-1006
[email protected]"
DESCRIPTION
"A MIB module containing textual conventions
for high capacity data types. This module
addresses an immediate need for data types not directly
supported in the SMIv2. This short-term solution
is meant to be deprecated as a long-term solution
is deployed."
REVISION "200006080000Z"
DESCRIPTION
"Initial Version of the High Capacity Numbers
MIB module, published as RFC 2856."
::= { mib-2 78 }

CounterBasedGauge64 ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"The CounterBasedGauge64 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

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RFC 2856 High Capacity Data Types June 2000

not be smaller than 0. The value of a CounterBasedGauge64
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
CounterBasedGauge64 also decreases (increases).

Note that this TC is not strictly supported in SMIv2,
because the 'always increasing' and 'counter wrap' semantics
associated with the Counter64 base type are not preserved.
It is possible that management applications which rely
solely upon the (Counter64) ASN.1 tag to determine object
semantics will mistakenly operate upon objects of this type
as they would for Counter64 objects.

This textual convention represents a limited and short-term
solution, and may be deprecated as a long term solution is
defined and deployed to replace it."
SYNTAX Counter64

ZeroBasedCounter64 ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"This TC describes an object which counts events with the
following semantics: objects of this type will be set to
zero(0) on creation and will thereafter count appropriate
events, wrapping back to zero(0) when the value 2^64 is
reached.

Provided that an application discovers the new object within
the minimum time to wrap it can use the initial value as a
delta since it last polled the table of which this object is
part. It is important for a management station to be aware
of this minimum time and the actual time between polls, and
to discard data if the actual time is too long or there is
no defined minimum time.

Typically this TC is used in tables where the INDEX space is
constantly changing and/or the TimeFilter mechanism is in
use.

Note that this textual convention does not retain all the
semantics of the Counter64 base type. Specifically, a
Counter64 has an arbitrary initial value, but objects
defined with this TC are required to start at the value

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RFC 2856 High Capacity Data Types June 2000

zero. This behavior is not likely to have any adverse
effects on management applications which are expecting
Counter64 semantics.

This textual convention represents a limited and short-term
solution, and may be deprecated as a long term solution is
defined and deployed to replace it."
SYNTAX Counter64

END

5. 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.

6. References

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

[RFC1157] Case, J., Fedor, M., Schoffstall, M. and J. Davin,
"Simple Network Management Protocol", STD 15, RFC 1157,
May 1990.

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

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

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RFC 2856 High Capacity Data Types June 2000

[RFC1901] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
"Introduction to Community-based SNMPv2", RFC 1901,
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, 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, January 1996.

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

[RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, 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, April 1999.

[RFC2571] Harrington, D., Presuhn, R. and B. Wijnen, "An
Architecture for Describing SNMP Management Frameworks",
RFC 2571, 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, April
1999.

[RFC2573] Levi, D., Meyer, P. and B. Stewart, "SNMPv3
Applications", RFC 2573, 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, 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, April 1999.

[RFC2578] 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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RFC 2856 High Capacity Data Types June 2000

[RFC2579] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
Rose, M. and S. Waldbusser, "Textual Conventions for
SMIv2", STD 58, RFC 2579, April 1999.

[RFC2580] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
Rose, M. and S. Waldbusser, "Conformance Statements for
SMIv2", STD 58, RFC 2580, April 1999.

7. Security Considerations

This module does not define any management objects. Instead, it
defines a set of textual conventions which may be used by other MIB
modules to define management objects.

Meaningful security considerations can only be written in the modules
that define management objects.

8. Authors' Addresses

Andy Bierman
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134 USA

Phone: +1 408-527-3711
EMail: [email protected]

Keith McCloghrie
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134 USA

Phone: +1 408-526-5260
EMail: [email protected]

Randy Presuhn
BMC Software, Inc.
Office 1-3141
2141 North First Street
San Jose, California 95131 USA

Phone: +1 408 546-1006
EMail: [email protected]

Bierman, et al. Standards Track [Page 9]

RFC 2856 High Capacity Data Types June 2000

9. Full Copyright Statement

Copyright (C) The Internet Society (2000). 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.

Acknowledgement

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

Bierman, et al. Standards Track [Page 10]