rfc2856.txt

RFC 的详细文档！

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






Bierman, et al.             Standards Track                     [Page 1]

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.







Bierman, et al.             Standards Track                     [Page 2]

RFC 2856                High Capacity Data Types               June 2000


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:





Bierman, et al.             Standards Track                     [Page 3]

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"



Bierman, et al.             Standards Track                     [Page 4]

RFC 2856                High Capacity Data Types               June 2000


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

                    Andy Bierman
                    Cisco Systems Inc.
                    170 West Tasman Drive
                    San Jose, CA 95134 USA
                    [phone]
                    [e-mail]

                    Keith McCloghrie
                    Cisco Systems Inc.
                    170 West Tasman Drive
                    San Jose, CA 95134 USA
                    [phone]
                    [e-mail]

                    Randy Presuhn
                    BMC Software, Inc.
                    Office 1-3141
                    2141 North First Street
                    San Jose,  California 95131 USA
                    [phone]
                    [e-mail]"
     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



Bierman, et al.             Standards Track                     [Page 5]