rfc1903.txt

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Network Working Group                               SNMPv2 Working Group
Request for Comments: 1903                                       J. Case
Obsoletes: 1443                                      SNMP Research, Inc.
Category: Standards Track                                  K. McCloghrie
                                                     Cisco Systems, Inc.
                                                                 M. Rose
                                            Dover Beach Consulting, Inc.
                                                           S. Waldbusser
                                          International Network Services
                                                            January 1996


                          Textual Conventions
                          for Version 2 of the
              Simple Network Management Protocol (SNMPv2)

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.

Table of Contents

   1. Introduction ................................................    1
   1.1 A Note on Terminology ......................................    2
   2. Definitions .................................................    3
   3. Mapping of the TEXTUAL-CONVENTION macro .....................   19
   3.1 Mapping of the DISPLAY-HINT clause .........................   19
   3.2 Mapping of the STATUS clause ...............................   21
   3.3 Mapping of the DESCRIPTION clause ..........................   21
   3.4 Mapping of the REFERENCE clause ............................   21
   3.5 Mapping of the SYNTAX clause ...............................   22
   4. Security Considerations .....................................   22
   5. Editor's Address ............................................   22
   6. Acknowledgements ............................................   22
   7. References ..................................................   23

1.  Introduction

   A management system contains:  several (potentially many) nodes, each
   with a processing entity, termed an agent, which has access to
   management instrumentation; at least one management station; and, a
   management protocol, used to convey management information between
   the agents and management stations.  Operations of the protocol are
   carried out under an administrative framework which defines



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   authentication, authorization, access control, and privacy policies.

   Management stations execute management applications which monitor and
   control managed elements.  Managed elements are devices such as
   hosts, routers, terminal servers, etc., which are monitored and
   controlled via access to their management information.

   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 a subset of OSI's
   Abstract Syntax Notation One (ASN.1) [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.

   For all textual conventions defined in an information module, the
   name shall be unique and mnemonic, and shall not exceed 64 characters
   in length.  (However, names longer than 32 characters are not
   recommended.) All names used for the textual conventions defined in
   all "standard" information modules shall be unique.

1.1.  A Note on Terminology

   For the purpose of exposition, the original Internet-standard Network
   Management Framework, as described in RFCs 1155 (STD 16), 1157 (STD
   15), and 1212 (STD 16), is termed the SNMP version 1 framework
   (SNMPv1).  The current framework is termed the SNMP version 2
   framework (SNMPv2).









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2.  Definitions

SNMPv2-TC DEFINITIONS ::= BEGIN

IMPORTS
    ObjectSyntax, TimeTicks
        FROM SNMPv2-SMI;


-- definition of textual conventions

TEXTUAL-CONVENTION MACRO ::=
BEGIN
    TYPE NOTATION ::=
                  DisplayPart
                  "STATUS" Status
                  "DESCRIPTION" Text
                  ReferPart
                  "SYNTAX" Syntax

    VALUE NOTATION ::=
                  value(VALUE Syntax)

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

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

    ReferPart ::=
                  "REFERENCE" Text
                | empty

    -- uses the NVT ASCII character set
    Text ::= """" string """"

    Syntax ::=
                  type(ObjectSyntax)
                | "BITS" "{" Kibbles "}"
    Kibbles ::=
                  Kibble
                | Kibbles "," Kibble
    Kibble ::=
                  identifier "(" nonNegativeNumber ")"




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END


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



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    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))


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



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    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
    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.