rfc2579.txt

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Network Working Group                 Editors of this version:
Request for Comments: 2579                                 K. McCloghrie
STD: 58                                                    Cisco Systems
Obsoletes: 1903                                               D. Perkins
Category: Standards Track                                       SNMPinfo
                                                        J. Schoenwaelder
                                                         TU Braunschweig
                                      Authors of previous version:
                                                                 J. Case
                                                           SNMP Research
                                                           K. McCloghrie
                                                           Cisco Systems
                                                                 M. Rose
                                                  First Virtual Holdings
                                                           S. Waldbusser
                                          International Network Services
                                                              April 1999


                     Textual Conventions for SMIv2


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 (1999).  All Rights Reserved.


Table of Contents

   1 Introduction ..................................................2
   1.1 A Note on Terminology .......................................2
   2 Definitions ...................................................2
   3 Mapping of the TEXTUAL-CONVENTION macro ......................20
   3.1 Mapping of the DISPLAY-HINT clause .........................21
   3.2 Mapping of the STATUS clause ...............................22
   3.3 Mapping of the DESCRIPTION clause ..........................23
   3.4 Mapping of the REFERENCE clause ............................23
   3.5 Mapping of the SYNTAX clause ...............................23
   4 Sub-typing of Textual Conventions ............................23
   5 Revising a Textual Convention Definition .....................23


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   6 Security Considerations ......................................24
   7 Editors' Addresses ...........................................25
   8 References ...................................................25
   9 Full Copyright Statement .....................................26

1.  Introduction

   Management information is viewed as a collection of managed objects,
   residing in a virtual information store, termed the Management
   Information Base (MIB).  Collections of related objects are defined
   in MIB modules.  These modules are written using an adapted subset of
   OSI's Abstract Syntax Notation One, ASN.1 (1988) [1], termed the
   Structure of Management Information (SMI) [2].

   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.  These newly defined types are
   termed textual conventions, and are used for the convenience of
   humans reading the MIB module.  It is the purpose of this document to
   define the initial set of textual conventions available to all MIB
   modules.

   Objects defined using a textual convention are always encoded by
   means of the rules that define their primitive type.  However,
   textual conventions often have special semantics associated with
   them.  As such, an ASN.1 macro, TEXTUAL-CONVENTION, is used to
   concisely convey the syntax and semantics of a textual convention.

1.1.  A Note on Terminology

   For the purpose of exposition, the original Structure of Management
   Information, as described in RFCs 1155 (STD 16), 1212 (STD 16), and
   RFC 1215, is termed the SMI version 1 (SMIv1).  The current version
   of the Structure of Management Information is termed SMI version 2
   (SMIv2).

2.  Definitions

SNMPv2-TC DEFINITIONS ::= BEGIN

IMPORTS
    TimeTicks         FROM SNMPv2-SMI;


-- definition of textual conventions

TEXTUAL-CONVENTION MACRO ::=


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RFC 2579             Textual Conventions for SMIv2            April 1999


BEGIN
    TYPE NOTATION ::=
                  DisplayPart
                  "STATUS" Status
                  "DESCRIPTION" Text
                  ReferPart
                  "SYNTAX" Syntax

    VALUE NOTATION ::=
                   value(VALUE Syntax)      -- adapted ASN.1

    DisplayPart ::=
                  "DISPLAY-HINT" Text
                | empty

    Status ::=
                  "current"
                | "deprecated"
                | "obsolete"

    ReferPart ::=
                  "REFERENCE" Text
                | empty

    -- a character string as defined in [2]
    Text ::= value(IA5String)

    Syntax ::=   -- Must be one of the following:
                       -- a base type (or its refinement), or
                       -- a BITS pseudo-type
                  type
                | "BITS" "{" NamedBits "}"

    NamedBits ::= NamedBit
                | NamedBits "," NamedBit

    NamedBit ::=  identifier "(" number ")" -- number is nonnegative

END




DisplayString ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "255a"
    STATUS       current
    DESCRIPTION
            "Represents textual information taken from the NVT ASCII


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            character set, as defined in pages 4, 10-11 of RFC 854.

            To summarize RFC 854, the NVT ASCII repertoire specifies:

              - the use of character codes 0-127 (decimal)

              - the graphics characters (32-126) are interpreted as
                US ASCII

              - NUL, LF, CR, BEL, BS, HT, VT and FF have the special
                meanings specified in RFC 854

              - the other 25 codes have no standard interpretation

              - the sequence 'CR LF' means newline

              - the sequence 'CR NUL' means carriage-return

              - an 'LF' not preceded by a 'CR' means moving to the
                same column on the next line.

              - the sequence 'CR x' for any x other than LF or NUL is
                illegal.  (Note that this also means that a string may
                end with either 'CR LF' or 'CR NUL', but not with CR.)

            Any object defined using this syntax may not exceed 255
            characters in length."
    SYNTAX       OCTET STRING (SIZE (0..255))

PhysAddress ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "1x:"
    STATUS       current
    DESCRIPTION
            "Represents media- or physical-level addresses."
    SYNTAX       OCTET STRING


MacAddress ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "1x:"
    STATUS       current
    DESCRIPTION
            "Represents an 802 MAC address represented in the
            `canonical' order defined by IEEE 802.1a, i.e., as if it
            were transmitted least significant bit first, even though
            802.5 (in contrast to other 802.x protocols) requires MAC
            addresses to be transmitted most significant bit first."
    SYNTAX       OCTET STRING (SIZE (6))



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TruthValue ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION
            "Represents a boolean value."
    SYNTAX       INTEGER { true(1), false(2) }

TestAndIncr ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION
            "Represents integer-valued information used for atomic
            operations.  When the management protocol is used to specify
            that an object instance having this syntax is to be
            modified, the new value supplied via the management protocol
            must precisely match the value presently held by the
            instance.  If not, the management protocol set operation
            fails with an error of `inconsistentValue'.  Otherwise, if
            the current value is the maximum value of 2^31-1 (2147483647
            decimal), then the value held by the instance is wrapped to
            zero; otherwise, the value held by the instance is
            incremented by one.  (Note that regardless of whether the
            management protocol set operation succeeds, the variable-
            binding in the request and response PDUs are identical.)

            The value of the ACCESS clause for objects having this
            syntax is either `read-write' or `read-create'.  When an
            instance of a columnar object having this syntax is created,
            any value may be supplied via the management protocol.

            When the network management portion of the system is re-
            initialized, the value of every object instance having this
            syntax must either be incremented from its value prior to
            the re-initialization, or (if the value prior to the re-
            initialization is unknown) be set to a pseudo-randomly
            generated value."
    SYNTAX       INTEGER (0..2147483647)

AutonomousType ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION
            "Represents an independently extensible type identification
            value.  It may, for example, indicate a particular sub-tree
            with further MIB definitions, or define a particular type of
            protocol or hardware."
    SYNTAX       OBJECT IDENTIFIER


InstancePointer ::= TEXTUAL-CONVENTION
    STATUS       obsolete


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    DESCRIPTION
            "A pointer to either a specific instance of a MIB object or
            a conceptual row of a MIB table in the managed device.  In
            the latter case, by convention, it is the name of the
            particular instance of the first accessible columnar object
            in the conceptual row.

            The two uses of this textual convention are replaced by
            VariablePointer and RowPointer, respectively."
    SYNTAX       OBJECT IDENTIFIER


VariablePointer ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION
            "A pointer to a specific object instance.  For example,
            sysContact.0 or ifInOctets.3."
    SYNTAX       OBJECT IDENTIFIER


RowPointer ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION
            "Represents a pointer to a conceptual row.  The value is the
            name of the instance of the first accessible columnar object
            in the conceptual row.

            For example, ifIndex.3 would point to the 3rd row in the
            ifTable (note that if ifIndex were not-accessible, then
            ifDescr.3 would be used instead)."
    SYNTAX       OBJECT IDENTIFIER

RowStatus ::= TEXTUAL-CONVENTION
    STATUS       current
    DESCRIPTION
            "The RowStatus textual convention is used to manage the
            creation and deletion of conceptual rows, and is used as the
            value of the SYNTAX clause for the status column of a
            conceptual row (as described in Section 7.7.1 of [2].)











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            The status column has six defined values:

                 - `active', which indicates that the conceptual row is
                 available for use by the managed device;

                 - `notInService', which indicates that the conceptual
                 row exists in the agent, but is unavailable for use by
                 the managed device (see NOTE below); 'notInService' has
                 no implication regarding the internal consistency of
                 the row, availability of resources, or consistency with
                 the current state of the managed device;

                 - `notReady', which indicates that the conceptual row
                 exists in the agent, but is missing information
                 necessary in order to be available for use by the
                 managed device (i.e., one or more required columns in
                 the conceptual row have not been instanciated);

                 - `createAndGo', which is supplied by a management
                 station wishing to create a new instance of a
                 conceptual row and to have its status automatically set
                 to active, making it available for use by the managed
                 device;