RFC2856
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.
Contents
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.
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.
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.
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:
- 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.
New Textual Conventions
The following textual conventions are defined to support unsigned 64-bit data types.
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.
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.
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"
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
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
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
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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.
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.
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.
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.
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]
Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
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Acknowledgement
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