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rfc:rfc6643

Internet Engineering Task Force (IETF) J. Schoenwaelder Request for Comments: 6643 Jacobs University Category: Standards Track July 2012 ISSN: 2070-1721

Translation of Structure of Management Information Version 2 (SMIv2)
                    MIB Modules to YANG Modules

Abstract

 YANG is a data modeling language used to model configuration and
 state data manipulated by the Network Configuration Protocol
 (NETCONF), NETCONF remote procedure calls, and NETCONF notifications.
 The Structure of Management Information (SMIv2) defines fundamental
 data types, an object model, and the rules for writing and revising
 MIB modules for use with the Simple Network Management Protocol
 (SNMP).  This document defines a translation of SMIv2 MIB modules
 into YANG modules, enabling read-only (config false) access to data
 objects defined in SMIv2 MIB modules via NETCONF.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6643.

Schoenwaelder Standards Track [Page 1] RFC 6643 Translation of SMIv2 to YANG July 2012

Copyright Notice

 Copyright (c) 2012 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.
 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008.  The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow
 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

Schoenwaelder Standards Track [Page 2] RFC 6643 Translation of SMIv2 to YANG July 2012

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
 2.  Mapping of Well-Known Types  . . . . . . . . . . . . . . . . .  4
 3.  Translation of SMIv2 Modules and SMIv2 IMPORT Clauses  . . . .  5
   3.1.  Example: IMPORTS of IF-MIB . . . . . . . . . . . . . . . .  6
 4.  Translation of the MODULE-IDENTITY Macro . . . . . . . . . . .  7
   4.1.  MODULE-IDENTITY Translation Rules  . . . . . . . . . . . .  7
   4.2.  Example: MODULE-IDENTITY of IF-MIB . . . . . . . . . . . .  8
 5.  Translation of the TEXTUAL-CONVENTION Macro  . . . . . . . . .  9
   5.1.  TEXTUAL-CONVENTION Translation Rules . . . . . . . . . . .  9
   5.2.  Example: OwnerString and InterfaceIndex of IF-MIB  . . . . 10
   5.3.  Example: IfDirection of the DIFFSERV-MIB . . . . . . . . . 11
 6.  Translation of OBJECT IDENTIFIER Assignments . . . . . . . . . 11
 7.  Translation of the OBJECT-TYPE Macro . . . . . . . . . . . . . 11
   7.1.  Scalar and Columnar Object Translation Rules . . . . . . . 11
   7.2.  Example: ifNumber and ifIndex of the IF-MIB  . . . . . . . 13
   7.3.  Non-Augmenting Conceptual Table Translation Rules  . . . . 13
   7.4.  Example: ifTable of the IF-MIB . . . . . . . . . . . . . . 15
   7.5.  Example: ifRcvAddressTable of the IF-MIB . . . . . . . . . 16
   7.6.  Example: alHostTable of the RMON2-MIB  . . . . . . . . . . 17
   7.7.  Augmenting Conceptual Tables Translation Rules . . . . . . 18
   7.8.  Example: ifXTable of the IF-MIB  . . . . . . . . . . . . . 20
 8.  Translation of the OBJECT-IDENTITY Macro . . . . . . . . . . . 21
   8.1.  OBJECT-IDENTITY Translation Rules  . . . . . . . . . . . . 21
   8.2.  Example: diffServTBParamSimpleTokenBucket of the
         DIFFSERV-MIB . . . . . . . . . . . . . . . . . . . . . . . 21
 9.  Translation of the NOTIFICATION-TYPE Macro . . . . . . . . . . 22
   9.1.  NOTIFICATION-TYPE Translation Rules  . . . . . . . . . . . 22
   9.2.  Example: linkDown NOTIFICATION-TYPE of IF-MIB  . . . . . . 23
 10. YANG Language Extension Definition . . . . . . . . . . . . . . 24
 11. Implementing Configuration Data Nodes  . . . . . . . . . . . . 27
   11.1. Example: addressMapControlTable of RMON2-MIB . . . . . . . 28
 12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 30
 13. Security Considerations  . . . . . . . . . . . . . . . . . . . 30
 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31
 15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31
   15.1. Normative References . . . . . . . . . . . . . . . . . . . 31
   15.2. Informative References . . . . . . . . . . . . . . . . . . 31
 Appendix A.  Mapping of Well-Known Types (Normative) . . . . . . . 33
 Appendix B.  Module Prefix Generation (Informative)  . . . . . . . 35

Schoenwaelder Standards Track [Page 3] RFC 6643 Translation of SMIv2 to YANG July 2012

1. Introduction

 This document describes a translation of SMIv2 [RFC2578], [RFC2579],
 [RFC2580] MIB modules into YANG [RFC6020] modules, enabling read-only
 (config false, as defined in Section 7.19.1 of RFC 6020) access to
 SMIv2 objects defined in SMIv2 MIB modules via NETCONF [RFC6241].
 For a discussion why SMIv2 read-write or read-create objects are
 translated to read-only (config false) YANG objects, see Section 11.
 YANG modules generated from SMIv2 modules should not be modified.
 Any necessary changes should be made by modifying the original SMIv2
 modules (with proper updates of the SMIv2 LAST-UPDATED and REVISION
 clauses) and then running the translation defined in this memo again.
 Note that this does not affect the usage of YANG augments and or YANG
 deviations: YANG modules generated from SMIv2 modules can be
 augmented like any other YANG module, and YANG deviations can be used
 to document how an implementation deviates from the generated YANG
 module.
 SMIv1 modules can be converted to YANG by first following the rules
 in [RFC3584] to convert the SMIv1 module to SMIv2 and then following
 the rules in this document to convert the obtained SMIv2 module to
 YANG.
 The SMIv2-to-YANG mapping is illustrated by examples showing the
 translation of parts of the IF-MIB [RFC2863], the DIFFSERV-MIB
 [RFC3289], and the RMON2-MIB [RFC4502] SMIv2 modules.
 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
 "OPTIONAL" in this document are to be interpreted as described in BCP
 14 [RFC2119].

2. Mapping of Well-Known Types

 The SMIv2 base types and some well-known derived textual conventions
 are mapped to YANG types according to Appendix A.  The mapping of the
 OCTET STRING depends on the context.  If an OCTET STRING type has an
 associated DISPLAY-HINT, then the corresponding YANG base type is the
 string type.  An implementation MUST format an OCTET STRING value
 according to the DISPLAY-HINT, as described in RFC 2579.  If an
 OCTECT STRING type does not have an associated DISPLAY-HINT, the
 binary type is used.  Similarly, the mapping of the INTEGER type
 depends on its usage as an enumeration or a 32-bit integral type.
 Implementations should provide implementation-specific options to
 handle situations where DISPLAY- HINTs are added during a revision of
 a module and backwards compatibility must be preserved, i.e., an
 added DISPLAY-HINT needs to be ignored.

Schoenwaelder Standards Track [Page 4] RFC 6643 Translation of SMIv2 to YANG July 2012

 The mappings shown in Appendix A may require to import the ietf-yang-
 types, ietf-inet-types, or ietf-yang-smiv2 YANG modules since some
 SMIv2 types and textual conventions map to YANG types defined in the
 ietf-yang-types and ietf-inet-types YANG modules defined in [RFC6021]
 and the ietf-yang-smiv2 YANG module defined in this document.
 Implementations MUST add any additional imports required by the type
 mapping.

3. Translation of SMIv2 Modules and SMIv2 IMPORT Clauses

 SMIv2 modules are mapped to corresponding YANG modules.  The
 generated YANG module name MUST be the same as the SMIv2 module name.
 The YANG namespace MUST be constructed out of the IANA-registered
 prefix urn:ietf:params:xml:ns:yang:smiv2: (see Section 12) followed
 by the SMIv2 module name.  Since SMIv2 module names can be assumed to
 be unique (see Section 3 in [RFC2578]), the resulting YANG namespace
 is unique.
 The YANG prefix MAY be derived from the SMIv2 module name using the
 module prefix generation algorithm described in Appendix B.  The YANG
 prefix is supposed to be short, and it must be unique within the set
 of all prefixes used by a YANG module.  The algorithm described in
 Appendix B generates such prefixes.
 SMIv2 IMPORT clauses are translated to YANG import statements.  One
 major difference between the SMIv2 import mechanism and the YANG
 import mechanism is that SMIv2 IMPORT clauses import specific symbols
 from an SMIv2 module, while the YANG import statement imports all
 symbols of the referenced YANG module.
 In order to produce correct and complete YANG import statements, the
 following rules MUST be used:
 o  Process each item in each SMIv2 IMPORT clause as follows:
    1.  If an import statement for this SMIv2 module has already been
        generated, then ignore this item.
    2.  Otherwise, if the SMIv2 module name is SNMPv2-SMI or SNMPv2-
        CONF, then ignore this item.  Note that these two modules can
        be completely ignored since all definitions in these modules
        are translated by translation rules.
    3.  Otherwise, if this item is a textual convention matching one
        of the textual conventions in the SMIv2 types column of
        Appendix A (e.g., MacAddress, PhysAddress, or TimeStamp) then
        ignore this item.

Schoenwaelder Standards Track [Page 5] RFC 6643 Translation of SMIv2 to YANG July 2012

    4.  Otherwise, if the item is used in a SYNTAX clause of an
        OBJECT-TYPE whose MAX-ACCESS is not accessible-for-notify,
        then generate an import statement as described below.
    5.  Otherwise, if the item is used in an OBJECTS clause of a
        NOTIFICATION-TYPE, then generate an import statement as
        described below.
    6.  Otherwise, if the item is used in an INDEX or AUGMENTS clause,
        then generate an import statement as described below.
    7.  Otherwise, ignore this item.  Some examples of this case are
        OBJECT IDENTIFIER assignments and objects that are only
        referenced in MODULE-COMPLIANCE, OBJECT-GROUP, or
        NOTIFICATION-GROUP clauses.
 o  Generate any additional import statements as required by the type
    translations according to the type mapping table Appendix A.  This
    requires the translator to consider all the types used in the
    SMIv2 module in order to produce the imports.
 o  Generate an import statement for the YANG module ietf-yang-smiv2
    with the prefix smiv2.
 The generated import statements use the untranslated SMIv2 module
 names or the names of well-known YANG modules as their argument.  The
 import statement must contain a prefix statement.  The prefixes MAY
 be generated by applying the module prefix generation algorithm
 described in Appendix B.

3.1. Example: IMPORTS of IF-MIB

 The translation of the IF-MIB [RFC2863] leads to the YANG module and
 namespace/prefix statement and the import statements shown below.
 The prefix is the translation of the SMIv2 module name IF-MIB to
 lowercase (consisting of two tokens and thus no further
 abbreviation).
   module IF-MIB {
     namespace "urn:ietf:params:xml:ns:yang:smiv2:IF-MIB";
     prefix "if-mib";
     import IANAifType-MIB      { prefix "ianaiftype-mib"; }
     import SNMPv2-TC           { prefix "snmpv2-tc"; }
     import ietf-yang-types     { prefix "yang"; }
     import ietf-yang-smiv2     { prefix "smiv2"; }
   }

Schoenwaelder Standards Track [Page 6] RFC 6643 Translation of SMIv2 to YANG July 2012

4. Translation of the MODULE-IDENTITY Macro

 SMIv2 requires an invocation of the MODULE-IDENTITY macro to provide
 contact and revision history for a MIB module.  The clauses of the
 SMIv2 MODULE-IDENTITY macro MUST be translated into YANG statements
 as detailed below.

4.1. MODULE-IDENTITY Translation Rules

 o  The SMIv2 ORGANIZATION clause is mapped to the YANG organization
    statement.
 o  The SMIv2 CONTACT-INFO clause is mapped to the YANG contact
    statement.
 o  The SMIv2 DESCRIPTION clause is mapped to the YANG description
    statement.
 o  Each SMIv2 REVISION clause is mapped to a YANG revision statement.
    The revision is identified by the date argument of the SMIv2
    REVISION clause.  DESCRIPTION sub-clauses of REVISION clauses are
    mapped to corresponding description statement nested in revision
    clauses.
 o  The SMIv2 LAST-UPDATED clause is ignored if the associated date
    matches a REVISION clause.  Otherwise, an additional revision
    statement is generated.
 o  A top-level YANG container is generated.  The container's name is
    the SMIv2 module name, and the container MUST be config false.
    The generation of the top-level container MAY be skipped if the
    SMIv2 module does not define any objects that go into the top-
    level container (e.g., an SMIv2 module only defining textual
    conventions).
 o  The object identifier value of the invocation of the SMIv2 MODULE-
    IDENTITY is translated into an smiv2:oid statement contained in an
    smiv2:alias statement representing the MODULE-IDENTITY macro
    invocation.  Refer to the YANG extension defined in Section 10.
 While all proper SMIv2 modules must have exactly one MODULE-IDENTITY
 macro invocation, there are a few notable exceptions.  The modules
 defining the SMIv2 language (i.e., the SNMPv2-SMI, SNMPv2-TC, and
 SNMPv2-CONF modules) do not invoke the MODULE-IDENTITY macro.
 Furthermore, SMIv2 modules generated from SMIv1 modules may miss an
 invocation of the MODULE-IDENTITY macro as well.  In such cases, it
 is preferable to not generate organization, contact, description, or
 revision statements.

Schoenwaelder Standards Track [Page 7] RFC 6643 Translation of SMIv2 to YANG July 2012

4.2. Example: MODULE-IDENTITY of IF-MIB

 The translation of the MODULE-IDENTITY of the IF-MIB [RFC2863] leads
 to the following YANG statements:
   organization
    "IETF Interfaces MIB Working Group";
   contact
    "Keith McCloghrie
     Cisco Systems, Inc.
     170 West Tasman Drive
     San Jose, CA  95134-1706
     US
     408-526-5260
     kzm@cisco.com";
   description
    "The MIB module to describe generic objects for network
     interface sub-layers.  This MIB is an updated version of
     MIB-II's ifTable, and incorporates the extensions defined in
     RFC 1229.";
   revision "2000-06-14" {
     description
      "Clarifications agreed upon by the Interfaces MIB WG, and
       published as RFC 2863.";
   }
   revision "1996-02-28" {
     description
      "Revisions made by the Interfaces MIB WG, and published in
       RFC 2233.";
   }
   revision "1993-11-08" {
     description
      "Initial revision, published as part of RFC 1573.";
   }
   container IF-MIB {
     config false;
   }

Schoenwaelder Standards Track [Page 8] RFC 6643 Translation of SMIv2 to YANG July 2012

5. Translation of the TEXTUAL-CONVENTION Macro

 The SMIv2 uses invocations of the TEXTUAL-CONVENTION macro to define
 new types derived from the SMIv2 base types.  Invocations of the
 TEXTUAL-CONVENTION macro MUST be translated into YANG typedef
 statements as detailed below.

5.1. TEXTUAL-CONVENTION Translation Rules

 The name of the TEXTUAL-CONVENTION macro invocation is used as the
 name of the generated typedef statement.  The clauses of the SMIv2
 TEXTUAL-CONVENTION macro are mapped to YANG statements embedded in
 the typedef statement as follows:
 o  The SMIv2 DISPLAY-HINT clause is used to determine the type
    mapping of types derived form the OCTET STRING type as explained
    in Section 2.  Furthermore, the DISPLAY-HINT value MAY be used to
    generate a regular expression for the YANG pattern statement
    within the type statement.
 o  The SMIv2 DISPLAY-HINT is translated into an smiv2:display-hint
    statement.  Refer to the YANG extension defined in Section 10.
 o  The SMIv2 STATUS clause is mapped to the YANG status statement.
    The generation of the YANG status statement is skipped if the
    value of the STATUS clause is current.
 o  The SMIv2 DESCRIPTION clause is mapped to the YANG description
    statement.
 o  The SMIv2 REFERENCE clause is mapped to the YANG reference
    statement.
 o  The SMIv2 SYNTAX clause is mapped to the YANG type statement.
    SMIv2 range restrictions are mapped to YANG range statements,
    while SMIv2 length restrictions are mapped to YANG length
    statements.  SMIv2 INTEGER enumerations are mapped to YANG enum/
    value statements.  SMIv2 BITS are mapped to YANG bit/position
    statements.  For OCTET STRING types that are mapped to a YANG
    string base type (see Section 2), the length specified in the YANG
    length statement must be consistent with the stringified
    representation of values.  If an implementation is unable to
    derive a proper length restrictions, then the YANG length
    statement MUST be omitted.

Schoenwaelder Standards Track [Page 9] RFC 6643 Translation of SMIv2 to YANG July 2012

 This translation assumes that labels of named numbers and named bits
 do not change when an SMIv2 module is revised.  This is consistent
 with the clarification of the SMIv2 module revision rules in Section
 4.9 of [RFC4181].

5.2. Example: OwnerString and InterfaceIndex of IF-MIB

 The translations of the OwnerString and InterfaceIndex textual
 conventions of the IF-MIB [RFC2863] are shown below.
   typedef OwnerString {
     type string {
       length "0..255";
       pattern '\p{IsBasicLatin}{0,255}';
     }
     status deprecated;
     description
      "This data type is used to model an administratively
       assigned name of the owner of a resource.  This information
       is taken from the NVT ASCII character set.  It is suggested
       that this name contain one or more of the following: ASCII
       form of the manager station's transport address, management
       station name (e.g., domain name), network management
       personnel's name, location, or phone number.  In some cases
       the agent itself will be the owner of an entry.  In these
       cases, this string shall be set to a string starting with
       'agent'.";
     smiv2:display-hint "255a";
   }
   typedef InterfaceIndex {
     type int32 {
       range "1..2147483647";
     }
     description
      "A unique value, greater than zero, for each interface or
       interface sub-layer in the managed system.  It is
       recommended that values are assigned contiguously starting
       from 1.  The value for each interface sub-layer must remain
       constant at least from one re-initialization of the entity's
       network management system to the next re-initialization.";
     smiv2:display-hint "d";
   }

Schoenwaelder Standards Track [Page 10] RFC 6643 Translation of SMIv2 to YANG July 2012

5.3. Example: IfDirection of the DIFFSERV-MIB

 The translation of the IfDirection textual convention of the
 DIFFSERV-MIB [RFC3289] is shown below.
   typedef IfDirection {
     type enumeration {
       enum inbound  { value 1; }
       enum outbound { value 2; }
     }
     description
      "IfDirection specifies a direction of data travel on an
       interface. 'inbound' traffic is operated on during reception
       from the interface, while 'outbound' traffic is operated on
       prior to transmission on the interface.";
   }

6. Translation of OBJECT IDENTIFIER Assignments

 The SMIv2 uses OBJECT IDENTIFIER assignments to introduce names for
 intermediate nodes in the OBJECT IDENTIFIER tree.  OBJECT IDENTIFIER
 assignments are translated into smiv2:alias statements.  Refer to the
 YANG extension defined in Section 10.

7. Translation of the OBJECT-TYPE Macro

 The SMIv2 uses the OBJECT-TYPE macro to define objects and the
 structure of conceptual tables.  Objects exist either as scalars
 (exactly one instance within an SNMP context) or columnar objects
 within conceptual tables (zero or multiple instances within an SNMP
 context).  A number of auxiliary objects define the index (key) of a
 conceptual table.  Furthermore, conceptual tables can be augmented by
 other conceptual tables.  All these differences must be taken into
 account when translating SMIv2 OBJECT-TYPE macro invocations to YANG.
 Invocations of the OBJECT-TYPE macro MUST be translated into YANG
 statements as detailed below.

7.1. Scalar and Columnar Object Translation Rules

 SMIv2 OBJECT-TYPE macro invocations defining scalars or columnar
 objects with a MAX-ACCESS of "not-accessible", "read-only",
 "read-write", and "read-create" are translated to YANG leaf
 statements.  Additionally, columnar objects with a MAX-ACCESS of
 "accessible-for-notify" are translated to YANG leaf statements if
 that columnar object is part of the INDEX clause of the table
 containing that columnar object.  The name of the leaf is the name
 associated with the SMIv2 OBJECT-TYPE macro invocation.  SMIv2
 OBJECT-TYPE macro invocations with a MAX-ACCESS of

Schoenwaelder Standards Track [Page 11] RFC 6643 Translation of SMIv2 to YANG July 2012

 "accessible-for-notify" are not translated to YANG data tree leafs
 but instead are translated into YANG notification leafs.
 Leaf statements for scalar objects are created in a container
 representing the scalar's parent node in the OID tree.  This
 container is named after the scalar's parent node in the OID tree and
 placed in the top-level container representing the SMIv2 module; see
 Section 4.1.  In the rare case that the scalar's parent node has
 multiple names, the automatic translation MUST fail with an error,
 and the name clash needs to be investigated and fixed manually.  In
 case a previous revision of the SMIv2 module did not have an
 ambiguity, then the name used by the previous revision MUST be used.
 The leaf statements representing columnar objects are created in the
 list representing a conceptual row; see Section 7.3.
 o  The SMIv2 SYNTAX clause is mapped to the YANG type statement.
    SMIv2 range restrictions are mapped to YANG range statements,
    while SMIv2 length restrictions are mapped to YANG length
    statements.  SMIv2 INTEGER enumerations are mapped to YANG enum/
    value statements.  SMIv2 BITS are mapped to YANG bit/position
    statements.  For OCTET STRING types that are mapped to a YANG
    string base type (see Section 2), the length specified in the YANG
    length statement must be consistent with the stringified
    representation of values.  If an implementation is unable to
    derive proper length restrictions, then the YANG length statement
    MUST be omitted.
 o  The SMIv2 UNITS clause is mapped to the YANG units statement.
 o  The SMIv2 MAX-ACCESS is translated into an smiv2:max-access
    statement.  Refer to the YANG extension defined in Section 10.
 o  The SMIv2 STATUS clause is mapped to the YANG status statement.
    The generation of the YANG status statement is skipped if the
    value of the STATUS clause is current.
 o  The SMIv2 DESCRIPTION clause is mapped to the YANG description
    statement.
 o  The SMIv2 REFERENCE clause is mapped to the YANG reference
    statement.
 o  The SMIv2 DEFVAL clause is mapped to an smiv2:defval statement.
    Refer to the YANG extension defined in Section 10.
 o  The value of the SMIv2 OBJECT-TYPE macro invocation is translated
    into an smiv2:oid statement.  Refer to the YANG extension defined
    in Section 10.

Schoenwaelder Standards Track [Page 12] RFC 6643 Translation of SMIv2 to YANG July 2012

 This translation assumes that labels of named numbers and named bits
 do not change when an SMIv2 module is revised.  This is consistent
 with the clarification of the SMIv2 module revision rules in Section
 4.9 of [RFC4181].

7.2. Example: ifNumber and ifIndex of the IF-MIB

 The translations of the ifNumber scalar object and the ifIndex
 columnar object of the IF-MIB [RFC2863] are shown below.  Since
 ifNumber is a scalar object in the interfaces branch of the IF-MIB,
 the YANG leaf ifNumber will be placed in a YANG container called
 interfaces, which is registered in the top-level container IF-MIB.
   leaf ifNumber {
     type int32;
     description
      "The number of network interfaces (regardless of their
       current state) present on this system.";
     smiv2:max-access "read-only";
     smiv2:oid "1.3.6.1.2.1.2.1";
   }
   leaf ifIndex {
     type if-mib:InterfaceIndex;
     description
      "A unique value, greater than zero, for each interface.  It
       is recommended that values are assigned contiguously
       starting from 1.  The value for each interface sub-layer
       must remain constant at least from one re-initialization of
       the entity's network management system to the next re-
       initialization.";
     smiv2:max-access "read-only";
     smiv2:oid "1.3.6.1.2.1.2.2.1.1";
   }

7.3. Non-Augmenting Conceptual Table Translation Rules

 An OBJECT-TYPE macro invocation defining a non-augmenting conceptual
 table is translated to a YANG container statement using the name of
 the OBJECT-TYPE macro invocation.  This container is created in the
 top-level container representing the SMIv2 module.  The clauses of
 the macro are translated as follows:
 o  The SMIv2 SYNTAX clause is ignored
 o  The SMIv2 UNITS clause is ignored.
 o  The SMIv2 MAX-ACCESS clause is ignored.

Schoenwaelder Standards Track [Page 13] RFC 6643 Translation of SMIv2 to YANG July 2012

 o  The SMIv2 STATUS clause is mapped to the YANG status statement.
    The generation of the YANG status statement is skipped if the
    value of the STATUS clause is current.
 o  The SMIv2 DESCRIPTION clause is mapped to the YANG description
    statement.
 o  The SMIv2 REFERENCE clause is mapped to the YANG reference
    statement.
 o  The value of the SMIv2 OBJECT-TYPE macro invocation is translated
    into an smiv2:oid statement.  Refer to the YANG extension defined
    in Section 10.
 An OBJECT-TYPE macro invocation defining a conceptual row is
 translated to a YANG list statement.  It is contained in the YANG
 container representing the conceptual table.  The generated list uses
 the name of the row OBJECT-TYPE macro invocation.  The clauses of the
 OBJECT-TYPE macro are translated as follows:
 o  The SMIv2 SYNTAX clause is ignored.
 o  The SMIv2 UNITS clause is ignored.
 o  The SMIv2 MAX-ACCESS clause is ignored.
 o  The SMIv2 STATUS clause is mapped to the YANG status statement.
    The generation of the YANG status statement is skipped if the
    value of the STATUS clause is current.
 o  The SMIv2 DESCRIPTION clause is mapped to the YANG description
    statement.
 o  The SMIv2 REFERENCE clause is mapped to the YANG reference
    statement.
 o  The SMIv2 INDEX clause is mapped to the YANG key clause listing
    the columnar objects forming the key of the YANG list.  If the
    same object appears more than once in the INDEX clause, append
    '_<n>' to the duplicate object name(s) where '<n>' counts the
    occurrences of the object in the INDEX clause, starting from 2.
    Additional leaf statements must be created to define the leafs
    introduced.
 o  If the SMIv2 INDEX clause contains the IMPLIED keyword, then an
    smiv2:implied statement is generated to record the name of the
    object preceded by the IMPLIED keyword.  Refer to the YANG
    extension defined in Section 10.

Schoenwaelder Standards Track [Page 14] RFC 6643 Translation of SMIv2 to YANG July 2012

 o  The value of the SMIv2 OBJECT-TYPE macro invocation is translated
    into an smiv2:oid statement.  Refer to the YANG extension defined
    in Section 10.
 Within the list statement, YANG leaf statements are created for
 columnar objects as described in Section 7.1.  For objects listed in
 the SMIv2 INDEX clause that are not part of the conceptual table
 itself, YANG leaf statements of type leafref pointing to the
 referenced definition are created.

7.4. Example: ifTable of the IF-MIB

 The translation of the definition of the ifTable of the IF-MIB
 [RFC2863] is shown below.
   container ifTable {
     description
      "A list of interface entries.  The number of entries is
       given by the value of ifNumber.";
     smiv2:oid "1.3.6.1.2.1.2.2";
     list ifEntry {
       key "ifIndex";
       description
        "An entry containing management information applicable to a
         particular interface.";
       smiv2:oid "1.3.6.1.2.1.2.2.1";
       leaf ifIndex {
         type if-mib:InterfaceIndex;
         description
          "A unique value, greater than zero, for each interface.  It
           is recommended that values are assigned contiguously
           starting from 1.  The value for each interface sub-layer
           must remain constant at least from one re-initialization of
           the entity's network management system to the next re-
           initialization.";
         smiv2:max-access "read-only";
         smiv2:oid "1.3.6.1.2.1.2.2.1.1";
       }
       // ...
     }
   }

Schoenwaelder Standards Track [Page 15] RFC 6643 Translation of SMIv2 to YANG July 2012

7.5. Example: ifRcvAddressTable of the IF-MIB

 The translation of the definition of the ifRcvAddressTable of the
 IF-MIB [RFC2863] is shown below.
   container ifRcvAddressTable {
     description
      "This table contains an entry for each address (broadcast,
       multicast, or uni-cast) for which the system will receive
       packets/frames on a particular interface, except as follows:
  1. for an interface operating in promiscuous mode, entries are

only required for those addresses for which the system would

         receive frames were it not operating in promiscuous mode.
  1. for 802.5 functional addresses, only one entry is required,

for the address which has the functional address bit ANDed

         with the bit mask of all functional addresses for which the
         interface will accept frames.
       A system is normally able to use any unicast address which
       corresponds to an entry in this table as a source address.";
     smiv2:oid "1.3.6.1.2.1.31.1.4";
     list ifRcvAddressEntry {
       key "ifIndex ifRcvAddressAddress";
       description
        "A list of objects identifying an address for which the
         system will accept packets/frames on the particular
         interface identified by the index value ifIndex.";
       smiv2:oid "1.3.6.1.2.1.31.1.4.1";
       leaf ifIndex {
         type leafref {
           path "/if-mib:IF-MIB/if-mib:ifTable" +
                "/if-mib:ifEntry/if-mib:ifIndex";
         }
       }
       leaf ifRcvAddressAddress {
         type yang:phys-address;
         description
          "An address for which the system will accept packets/frames
           on this entry's interface.";
         smiv2:max-access "not-accessible";
         smiv2:oid "1.3.6.1.2.1.31.1.4.1.1";
       }

Schoenwaelder Standards Track [Page 16] RFC 6643 Translation of SMIv2 to YANG July 2012

       // ...
     }
   }

7.6. Example: alHostTable of the RMON2-MIB

 The translation of the definition of the alHostTable of the RMON2-MIB
 [RFC4502] is shown below.
 container alHostTable {
   description
    "A collection of statistics for a particular protocol from a
     particular network address that has been discovered on an
     interface of this device.
     The probe will populate this table for all protocols in the
     protocol directory table whose value of
     protocolDirHostConfig is equal to supportedOn(3), and
     will delete any entries whose protocolDirEntry is deleted or
     has a protocolDirHostConfig value of supportedOff(2).
     The probe will add to this table all addresses
     seen as the source or destination address in all packets with
     no MAC errors and will increment octet and packet counts in
     the table for all packets with no MAC errors.  Further,
     entries will only be added to this table if their address
     exists in the nlHostTable and will be deleted from this table
     if their address is deleted from the nlHostTable.";
   smiv2:oid "1.3.6.1.2.1.16.16.1";
   list alHostEntry {
     key "hlHostControlIndex alHostTimeMark protocolDirLocalIndex "
       + "nlHostAddress protocolDirLocalIndex_2";
     description
      "A conceptual row in the alHostTable.
       The hlHostControlIndex value in the index identifies the
       hlHostControlEntry on whose behalf this entry was created.
       The first protocolDirLocalIndex value in the index identifies
       the network-layer protocol of the address.
       The nlHostAddress value in the index identifies the network-
       layer address of this entry.
       The second protocolDirLocalIndex value in the index identifies
       the protocol that is counted by this entry.
       An example of the indexing in this entry is
       alHostOutPkts.1.783495.18.4.128.2.6.6.34.

Schoenwaelder Standards Track [Page 17] RFC 6643 Translation of SMIv2 to YANG July 2012

       Note that some combinations of index values may result in an
       index that exceeds 128 sub-identifiers in length, which exceeds
       the maximum for the SNMP protocol.  Implementations should take
       care to avoid such combinations.";
     smiv2:oid "1.3.6.1.2.1.16.16.1.1";
     // ...
     leaf protocolDirLocalIndex {
       type leafref {
         path "/rmon2-mib:RMON2-MIB/"
            + "rmon2-mib:protocolDirTable/"
            + "rmon2-mib:protocolDirEntry/"
            + "rmon2-mib:protocolDirLocalIndex";
       }
     }
     // ...
     leaf protocolDirLocalIndex_2 {
       type leafref {
         path "/rmon2-mib:RMON2-MIB/"
            + "rmon2-mib:protocolDirTable/"
            + "rmon2-mib:protocolDirEntry/"
            + "rmon2-mib:protocolDirLocalIndex";
       }
     }
     // ...
   }
 }

7.7. Augmenting Conceptual Tables Translation Rules

 An OBJECT-TYPE macro invocation defining an augmenting conceptual
 table is translated to a YANG smiv2:alias statement.  Refer to the
 YANG extension defined in Section 10.  The clauses of the macro are
 translated as follows:
 o  The SMIv2 SYNTAX clause is ignored.
 o  The SMIv2 UNITS clause is ignored.
 o  The SMIv2 MAX-ACCESS clause is ignored.
 o  The SMIv2 STATUS clause is mapped to the YANG status statement.
    The generation of the YANG status statement is skipped if the
    value of the STATUS clause is current.

Schoenwaelder Standards Track [Page 18] RFC 6643 Translation of SMIv2 to YANG July 2012

 o  The SMIv2 DESCRIPTION clause is mapped to the YANG description
    statement.
 o  The SMIv2 REFERENCE clause is mapped to the YANG reference
    statement.
 o  The value of the SMIv2 OBJECT-TYPE macro invocation is translated
    into an smiv2:oid statement.  Refer to the YANG extension defined
    in Section 10.
 An OBJECT-TYPE macro invocation defining a conceptual row
 augmentation is translated to a YANG smiv2:alias statement and a YANG
 augment statement using the path to the augmented table as its
 argument.  The clauses of the OBJECT-TYPE macro are translated as
 follows:
 o  The SMIv2 SYNTAX clause is ignored.
 o  The SMIv2 UNITS clause is ignored.
 o  The SMIv2 MAX-ACCESS clause is ignored.
 o  The SMIv2 STATUS clause is mapped to the YANG status statement.
    The generation of the YANG status statement is skipped if the
    value of the STATUS clause is current.
 o  The SMIv2 DESCRIPTION clause is mapped to the YANG description
    statement.
 o  The SMIv2 REFERENCE clause is mapped to the YANG reference
    statement.
 o  The value of the SMIv2 OBJECT-TYPE macro invocation is translated
    into an smiv2:oid statement.  Refer to the YANG extension defined
    in Section 10.
 Within the augment statement, YANG leaf statements are created as
 described in Section 7.1.

Schoenwaelder Standards Track [Page 19] RFC 6643 Translation of SMIv2 to YANG July 2012

7.8. Example: ifXTable of the IF-MIB

 The translation of the definition of the ifXTable of the IF-MIB
 [RFC2863] is shown below.
   smiv2:alias "ifXTable" {
     description
      "A list of interface entries.  The number of entries is
       given by the value of ifNumber.  This table contains
       additional objects for the interface table.";
     smiv2:oid "1.3.6.1.2.1.31.1.1";
   }
   smiv2:alias "ifXEntry" {
     description
      "An entry containing additional management information
       applicable to a particular interface.";
     smiv2:oid "1.3.6.1.2.1.31.1.1.1";
   }
   augment "/if-mib:IF-MIB/if-mib:ifTable/if-mib:ifEntry" {
     description
      "An entry containing additional management information
       applicable to a particular interface.";
     smiv2:oid "1.3.6.1.2.1.31.1.1.1";
     leaf ifName {
       type snmpv2-tc:DisplayString;
       description
        "The textual name of the interface.  The value of this
         object should be the name of the interface as assigned by
         the local device and should be suitable for use in commands
         entered at the device's `console'.  This might be a text
         name, such as `le0' or a simple port number, such as `1',
         depending on the interface naming syntax of the device.  If
         several entries in the ifTable together represent a single
         interface as named by the device, then each will have the
         same value of ifName.  Note that for an agent which responds
         to SNMP queries concerning an interface on some other
         (proxied) device, then the value of ifName for such an
         interface is the proxied device's local name for it.
         If there is no local name, or this object is otherwise not
         applicable, then this object contains a zero-length string.";
       smiv2:max-access "read-only";
       smiv2:oid "1.3.6.1.2.1.31.1.1.1.1";
     }

Schoenwaelder Standards Track [Page 20] RFC 6643 Translation of SMIv2 to YANG July 2012

     // ...
   }

8. Translation of the OBJECT-IDENTITY Macro

 The SMIv2 uses invocations of the OBJECT-IDENTITY macro to define
 information about an OBJECT IDENTIFIER assignment.  Invocations of
 the OBJECT-IDENTITY macro MUST be translated into YANG identity
 statements as detailed below.

8.1. OBJECT-IDENTITY Translation Rules

 The name of the OBJECT-IDENTITY macro invocation is used as the name
 of the generated identity statement.  The generated identity
 statement uses the smiv2:object-identity defined in Section 10 as its
 base.  The clauses of the SMIv2 OBJECT-IDENTITY macro are mapped to
 YANG statements as follows:
 o  The SMIv2 STATUS clause is mapped to the YANG status statement.
    The generation of the YANG status statement is skipped if the
    value of the STATUS clause is current.
 o  The SMIv2 DESCRIPTION clause is mapped to the YANG description
    statement.
 o  The SMIv2 REFERENCE clause is mapped to the YANG reference
    statement.
 o  The value of the SMIv2 OBJECT-IDENTITY macro invocation is
    translated into an smiv2:oid statement.  Refer to the YANG
    extension defined in Section 10.

8.2. Example: diffServTBParamSimpleTokenBucket of the DIFFSERV-MIB

 The translation of the diffServTBParamSimpleTokenBucket of the
 DIFFSERV-MIB [RFC3289] is shown below.  (Please note that the
 description should refer to RFC 3290, Section 5.1.3.)
   identity diffServTBParamSimpleTokenBucket {
     base "smiv2:object-identity";
     description
      "Two Parameter Token Bucket Meter as described in the Informal
       Differentiated Services Model section 5.2.3.";
     smiv2:oid "1.3.6.1.2.1.97.3.1.1";
   }

Schoenwaelder Standards Track [Page 21] RFC 6643 Translation of SMIv2 to YANG July 2012

9. Translation of the NOTIFICATION-TYPE Macro

 SMIv2 provides the NOTIFICATION-TYPE macro to define event
 notifications.  YANG provides the notification statement for the same
 purpose.  Invocations of the NOTIFICATION-TYPE macro MUST be
 translated into YANG notification statements as detailed below.

9.1. NOTIFICATION-TYPE Translation Rules

 The name of the NOTIFICATION-TYPE macro invocation is used as the
 name of the generated notification statement.  The clauses of the
 NOTIFICATION-TYPE macro are mapped to YANG statements embedded in the
 notification statement as follows.
 o  The SMIv2 OBJECTS clause is mapped to a sequence of YANG
    containers.  For each object listed in the OBJECTS clause value, a
    YANG container statement is generated.  The name of this container
    is the string "object-<n>", where <n> is the position of the
    object in the value of the OBJECTS clause (first element has
    position 1).  If the current object belongs to a conceptual table,
    then a sequence of leaf statements is generated for each INDEX
    object of the conceptual table.  These leafs are named after the
    INDEX objects and of type leafref.  Finally, a leaf statement is
    generated named after the current object.  If the current object
    has a MAX-ACCESS of "read-only", "read-write", or "read-create",
    then the generated leaf is of type leafref.  Otherwise, if the
    current object has a MAX-ACCESS of "accessible-for-notify", then a
    leaf is generated, following the steps in Section 7.1.
 o  The SMIv2 STATUS clause is mapped to the YANG status statement.
    The generation of the YANG status statement is skipped if the
    value of the STATUS clause is current.
 o  The SMIv2 DESCRIPTION clause is mapped to the YANG description
    statement.
 o  The SMIv2 REFERENCE clause is mapped to the YANG reference
    statement.
 o  The value of the SMIv2 NOTIFICATION-TYPE macro invocation is
    translated into an smiv2:oid statement.  Refer to the YANG
    extension defined in Section 10.

Schoenwaelder Standards Track [Page 22] RFC 6643 Translation of SMIv2 to YANG July 2012

9.2. Example: linkDown NOTIFICATION-TYPE of IF-MIB

 The translation of the linkDown notification of the IF-MIB [RFC2863]
 is shown below.
   notification linkDown {
     description
      "A linkDown trap signifies that the SNMP entity, acting in
       an agent role, has detected that the ifOperStatus object for
       one of its communication links is about to enter the down
       state from some other state (but not from the notPresent
       state).  This other state is indicated by the included value
       of ifOperStatus.";
     smiv2:oid "1.3.6.1.6.3.1.1.5.3";
     container object-1 {
       leaf ifIndex {
         type leafref {
           path "/if-mib:IF-MIB/if-mib:ifTable" +
                "/if-mib:ifEntry/if-mib:ifIndex";
         }
       }
     }
     container object-2 {
       leaf ifIndex {
         type leafref {
           path "/if-mib:IF-MIB/if-mib:ifTable" +
                "/if-mib:ifEntry/if-mib:ifIndex";
         }
       }
       leaf ifAdminStatus {
         type leafref {
           path "/if-mib:IF-MIB/if-mib:ifTable" +
                "/if-mib:ifEntry/if-mib:ifAdminStatus";
         }
       }
     }
     container object-3 {
       leaf ifIndex {
         type leafref {
           path "/if-mib:IF-MIB/if-mib:ifTable" +
                "/if-mib:ifEntry/if-mib:ifIndex";
         }
       }
       leaf ifOperStatus {
         type leafref {

Schoenwaelder Standards Track [Page 23] RFC 6643 Translation of SMIv2 to YANG July 2012

           path "/if-mib:IF-MIB/if-mib:ifTable" +
                "/if-mib:ifEntry/if-mib:ifOperStatus";
         }
       }
     }
   }

10. YANG Language Extension Definition

 This section defines some YANG extension statements that can be used
 to capture some information present in SMIv2 modules that is not
 translated into core YANG statements.  The YANG module references
 [RFC2578] and [RFC2579].
 <CODE BEGINS> file "ietf-yang-smiv2@2012-06-22.yang"

module ietf-yang-smiv2 {

 namespace "urn:ietf:params:xml:ns:yang:ietf-yang-smiv2";
 prefix "smiv2";
 organization
  "IETF NETMOD (NETCONF Data Modeling Language) Working Group";
 contact
  "WG Web:   <http://tools.ietf.org/wg/netmod/>
   WG List:  <mailto:netmod@ietf.org>
   WG Chair: David Kessens
             <mailto:david.kessens@nsn.com>
   WG Chair: Juergen Schoenwaelder
             <mailto:j.schoenwaelder@jacobs-university.de>
   Editor:   Juergen Schoenwaelder
             <mailto:j.schoenwaelder@jacobs-university.de>";
 description
  "This module defines YANG extensions that are used to translate
   SMIv2 concepts into YANG.
   Copyright (c) 2012 IETF Trust and the persons identified as
   authors of the code.  All rights reserved.
   Redistribution and use in source and binary forms, with or
   without modification, is permitted pursuant to, and subject
   to the license terms contained in, the Simplified BSD License
   set forth in Section 4.c of the IETF Trust's Legal Provisions

Schoenwaelder Standards Track [Page 24] RFC 6643 Translation of SMIv2 to YANG July 2012

   Relating to IETF Documents
   (http://trustee.ietf.org/license-info).
   This version of this YANG module is part of RFC 6643; see
   the RFC itself for full legal notices.";
 revision 2012-06-22 {
   description
    "Initial revision.";
   reference
    "RFC 6643: Translation of Structure of Management Information
     Version 2 (SMIv2) MIB Modules to YANG Modules";
 }
 identity object-identity {
   description
    "Base identity for all SMIv2 OBJECT-IDENTITYs.";
 }
 typedef opaque {
   type binary;
   description
    "The Opaque type supports the capability to pass arbitrary ASN.1
     syntax.  A value is encoded using the ASN.1 Basic Encoding Rules
     into a string of octets.  This, in turn, is encoded as an OCTET
     STRING, in effect 'double-wrapping' the original ASN.1 value.
     In the value set and its semantics, this type is equivalent to
     the Opaque type of the SMIv2.  This type exists in the SMIv2
     solely for backward-compatibility reasons and this is also
     true for this YANG data type.";
   reference
    "RFC 2578: Structure of Management Information Version 2 (SMIv2)";
 }
 extension display-hint {
   argument "format";
   description
    "The display-hint statement takes as an argument the DISPLAY-HINT
     assigned to an SMIv2 textual convention.";
   reference
    "RFC 2579: Textual Conventions for SMIv2";
 }

Schoenwaelder Standards Track [Page 25] RFC 6643 Translation of SMIv2 to YANG July 2012

 extension max-access {
   argument "access";
   description
    "The max-access statement takes as an argument the MAX-ACCESS
     assigned to an SMIv2 object definition.
     The MAX-ACCESS value is SMIv2 specific and has no impact on
     the access provided to YANG objects through protocols such
     as NETCONF.";
   reference
    "RFC 2578: Structure of Management Information Version 2 (SMIv2)";
 }
 extension defval {
   argument "value";
   description
    "The defval statement takes as an argument a default value
     defined by an SMIv2 DEFVAL clause.  Note that the value is in
     the SMIv2 value space defined by the SMIv2 syntax of the
     corresponding object and not in the YANG value space
     defined by the corresponding YANG data type.";
   reference
    "RFC 2578: Structure of Management Information Version 2 (SMIv2)";
 }
 extension implied {
   argument "index";
   description
    "If an SMIv2 INDEX object is preceded by the IMPLIED keyword, then
     the implied statement is present in the YANG module and takes as
     an argument the name of the IMPLIED index object.";
   reference
    "RFC 2578: Structure of Management Information Version 2 (SMIv2)";
  }
 extension alias {
   argument "descriptor";
   description
    "The alias statement introduces an SMIv2 descriptor.  The body of
     the alias statement is expected to contain an oid statement that
     provides the numeric OID associated with the descriptor.";
   reference
    "RFC 2578: Structure of Management Information Version 2 (SMIv2)";
 }

Schoenwaelder Standards Track [Page 26] RFC 6643 Translation of SMIv2 to YANG July 2012

 extension oid {
   argument "value";
   description
    "The oid statement takes as an argument the object identifier
     assigned to an SMIv2 definition.  The object identifier value
     is written in decimal dotted notation.";
   reference
    "RFC 2578: Structure of Management Information Version 2 (SMIv2)";
 }
 extension subid {
   argument "value";
   description
    "The subid statement takes as an argument the last sub-identifier
     of the object identifier assigned to an SMIv2 definition.  The
     sub-identifier value is a single positive decimal natural number.
     The subid statement may not be used as a substatement to any
     top-level node in a YANG document.  The subid substatement may
     be used only as a substatement to a node having a parent node
     defined with either an smiv2:oid or smiv2:subid substatement.";
   reference
    "RFC 2578: Structure of Management Information Version 2 (SMIv2)";
 }

}

 <CODE ENDS>

11. Implementing Configuration Data Nodes

 The result of the translation of SMIv2 MIB modules into YANG modules,
 even if SMIv2 objects are read-write or read-create, consists of
 read-only (config false) YANG objects.  One reason is that the
 persistency models of the underlying protocols, SNMP and NETCONF, are
 quite different.  With SNMP, the persistency of a writable object
 depends either on the object definition itself (i.e., the text in the
 DESCRIPTION clause) or the persistency properties of the conceptual
 row it is part of, sometimes controlled via a columnar object using
 the StorageType textual convention.  With NETCONF, the persistency of
 configuration objects is determined by the properties of the
 underlying datastore.  Furthermore, NETCONF as defined in [RFC6241]
 does not provide a standard operation to modify operational state.
 The <edit-config> and <copy-config> operations only manipulate
 configuration data.  As a consequence of these considerations, it is
 not possible to generate YANG configuration data nodes from SMIv2
 definitions in an automated way.

Schoenwaelder Standards Track [Page 27] RFC 6643 Translation of SMIv2 to YANG July 2012

 However, for selected SMIv2 objects where the SNMP and NETCONF
 persistency semantics are consistent, implementations may choose to
 implement some YANG data nodes generated from SMIv2 definitions as
 configuration data nodes.  Such a deviation from the generated read-
 only YANG module should be formally documented in the form of a
 separate YANG module that uses YANG deviation statements to change
 the config property of the data nodes implemented as configuration
 data nodes from false to true.  Deviations that change the config
 false property to true without any other changes to the semantics of
 the data node do not affect the compliance with the YANG module
 generated from an SMIv2 module.

11.1. Example: addressMapControlTable of RMON2-MIB

 The following example demonstrates how certain columnar objects of
 the addressMapControlTable of the RMON2-MIB [RFC4502] can be turned
 into YANG configuration data nodes.  Note that YANG deviations affect
 the property of the target node only and are not inherited downwards.
   module acme-RMON2-MIB-deviations {
     namespace "http://acme.example.com/RMON2-MIB-deviations";
     prefix "acme-rmon2-devs";
     import RMON2-MIB {
       prefix "rmon2-mib";
       revision-date 2006-05-02;
     }
     revision 2012-01-11 {
       description
         "First version.";
     }
     deviation "/rmon2-mib:RMON2-MIB" {
       deviate replace {
         config true;
       }
     }
     deviation "/rmon2-mib:RMON2-MIB/"
             + "rmon2-mib:addressMapControlTable" {
       deviate replace {
         config true;
       }
     }

Schoenwaelder Standards Track [Page 28] RFC 6643 Translation of SMIv2 to YANG July 2012

     deviation "/rmon2-mib:RMON2-MIB/"
             + "rmon2-mib:addressMapControlTable/"
             + "rmon2-mib:addressMapControlEntry" {
       deviate replace {
         config true;
       }
     }
     deviation "/rmon2-mib:RMON2-MIB/"
             + "rmon2-mib:addressMapControlTable/"
             + "rmon2-mib:addressMapControlEntry/"
             + "rmon2-mib:addressMapControlIndex" {
       deviate replace {
         config true;
       }
     }
     deviation "/rmon2-mib:RMON2-MIB/"
             + "rmon2-mib:addressMapControlTable/"
             + "rmon2-mib:addressMapControlEntry/"
             + "rmon2-mib:addressMapControlDataSource" {
       deviate replace {
         config true;
       }
     }
     deviation "/rmon2-mib:RMON2-MIB/"
             + "rmon2-mib:addressMapControlTable/"
             + "rmon2-mib:addressMapControlEntry/"
             + "rmon2-mib:addressMapControlOwner" {
       deviate replace {
         config true;
       }
     }
   }
 A NETCONF server that implements the RMON2-MIB module with these
 deviations would advertise the following capabilities in its <hello>
 message (where whitespace has been added for readability):

Schoenwaelder Standards Track [Page 29] RFC 6643 Translation of SMIv2 to YANG July 2012

   <capability>
     urn:ietf:params:xml:ns:yang:smiv2:RMON2-MIB?
       module=RMON2-MIB&amp;
       revision=2006-05-02&amp;
       deviations=acme-RMON2-MIB-deviations
   </capability>
   <capability>
     http://acme.example.com/RMON2-MIB-deviations?
       module=acme-RMON2-MIB-deviations&amp;
       revision=2012-01-11
   </capability>

12. IANA Considerations

 This document registers two URIs in the IETF XML registry [RFC3688].
 Following the format in RFC 3688, the following registrations have
 been made.
   URI: urn:ietf:params:xml:ns:yang:ietf-yang-smiv2
   Registrant Contact: The NETMOD WG of the IETF.
   XML: N/A, the requested URI is an XML namespace.
   URI: urn:ietf:params:xml:ns:yang:smiv2
   Registrant Contact: The NETMOD WG of the IETF.
   XML: N/A, the requested URI is an XML namespace.
 This document registers a YANG module in the YANG Module Names
 registry [RFC6020].
   Name:         ietf-yang-smiv2
   Namespace:    urn:ietf:params:xml:ns:yang:ietf-yang-smiv2
   Prefix:       smiv2
   Reference:    RFC 6643

13. Security Considerations

 This document defines a translation of SMIv2 MIB modules into YANG
 modules, enabling read-only (config false) access to data objects
 defined in SMIv2 MIB modules via NETCONF.  The translation itself has
 no security impact on the Internet.

Schoenwaelder Standards Track [Page 30] RFC 6643 Translation of SMIv2 to YANG July 2012

 Users of YANG data models generated from SMIv2 data models that have
 been published in the RFC series are advised to consult the security
 considerations of the respective RFCs.  The security considerations
 of RFCs containing SMIv2 data models explain which objects are
 sensitive and important to protect.  NETCONF users are encouraged to
 make use of the NETCONF access control model [RFC6536], which allows
 the specification of access control rules to protect potentially
 sensitive information.

14. Acknowledgements

 The author wishes to thank the following individuals for providing
 helpful comments on various draft versions of this document: Andy
 Bierman, Benoit Claise, Martin Bjorklund, Leif Johansson, David Reid,
 Dan Romascanu, and David Spakes.

15. References

15.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2578]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
            Schoenwaelder, Ed., "Structure of Management Information
            Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
 [RFC2579]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
            Schoenwaelder, Ed., "Textual Conventions for SMIv2",
            STD 58, RFC 2579, April 1999.
 [RFC2580]  McCloghrie, K., Perkins, D., and J. Schoenwaelder,
            "Conformance Statements for SMIv2", STD 58, RFC 2580,
            April 1999.
 [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
            the Network Configuration Protocol (NETCONF)", RFC 6020,
            October 2010.
 [RFC6021]  Schoenwaelder, J., "Common YANG Data Types", RFC 6021,
            October 2010.

15.2. Informative References

 [RFC2863]  McCloghrie, K. and F. Kastenholz, "The Interfaces Group
            MIB", RFC 2863, June 2000.

Schoenwaelder Standards Track [Page 31] RFC 6643 Translation of SMIv2 to YANG July 2012

 [RFC3289]  Baker, F., Chan, K., and A. Smith, "Management Information
            Base for the Differentiated Services Architecture",
            RFC 3289, May 2002.
 [RFC3584]  Frye, R., Levi, D., Routhier, S., and B. Wijnen,
            "Coexistence between Version 1, Version 2, and Version 3
            of the Internet-standard Network Management Framework",
            RFC 3584, August 2003.
 [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
            January 2004.
 [RFC4181]  Heard, C., "Guidelines for Authors and Reviewers of MIB
            Documents", BCP 111, RFC 4181, September 2005.
 [RFC4502]  Waldbusser, S., "Remote Network Monitoring Management
            Information  Base Version 2", RFC 4502, May 2006.
 [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
            and A. Bierman, Ed., "Network Configuration Protocol
            (NETCONF)", RFC 6241, June 2011.
 [RFC6536]  Bierman, A., Ed. and M. Bjorklund, Ed., "Network
            Configuration Protocol (NETCONF) Access Control Model",
            RFC 6536, March 2012.

Schoenwaelder Standards Track [Page 32] RFC 6643 Translation of SMIv2 to YANG July 2012

Appendix A. Mapping of Well-Known Types (Normative)

 This normative appendix describes the mapping of SMIv2 types to YANG
 types.  The mapping is fully consistent with Tables 1 and 2 of
 [RFC6021].
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   INTEGER       (used as an enumeration)
 YANG Type:    enumeration
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   INTEGER       (used as a numeric type)
 YANG Type:    int32
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   Integer32
 YANG Type:    int32
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   OCTET STRING  (used as a binary string)
 YANG Type:    binary
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   OCTET STRING  (used to hold UTF-8 or ASCII characters)
 YANG Type:    string
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   OBJECT IDENTIFIER
 YANG Module:  ietf-yang-types
 YANG Type:    object-identifier-128
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   BITS
 YANG Type:    bits
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   IpAddress
 YANG Module:  ietf-inet-types
 YANG Type:    ipv4-address
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   Counter32
 YANG Module:  ietf-yang-types
 YANG Type:    counter32

Schoenwaelder Standards Track [Page 33] RFC 6643 Translation of SMIv2 to YANG July 2012

 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   Gauge32
 YANG Module:  ietf-yang-types
 YANG Type:    gauge32
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   TimeTicks
 YANG Module:  ietf-yang-types
 YANG Type:    timeticks
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   Counter64
 YANG Module:  ietf-yang-types
 YANG Type:    counter64
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   Unsigned32
 YANG Type:    uint32
 SMIv2 Module: SNMPv2-SMI
 SMIv2 Type:   Opaque
 YANG Module:  ietf-yang-smiv2
 YANG Type:    opaque
 SMIv2 Module: SNMPv2-TC
 SMIv2 Type:   PhysAddress
 YANG Module:  ietf-yang-types
 YANG Type:    phys-address
 SMIv2 Module: SNMPv2-TC
 SMIv2 Type:   MacAddress
 YANG Module:  ietf-yang-types
 YANG Type:    mac-address
 SMIv2 Module: SNMPv2-TC
 SMIv2 Type:   TruthValue
 YANG Type:    boolean
 SMIv2 Module: SNMPv2-TC
 SMIv2 Type:   TimeStamp
 YANG Module:  ietf-yang-types
 YANG Type:    timestamp
 SMIv2 Module: RMON2-MIB
 SMIv2 Type:   ZeroBasedCounter32
 YANG Module:  ietf-yang-types
 YANG Type:    zero-based-counter32

Schoenwaelder Standards Track [Page 34] RFC 6643 Translation of SMIv2 to YANG July 2012

 SMIv2 Module: HCNUM-TC
 SMIv2 Type:   ZeroBasedCounter64
 YANG Module:  ietf-yang-types
 YANG Type:    zero-based-counter64
 SMIv2 Module: HCNUM-TC
 SMIv2 Type:   CounterBasedGauge64
 YANG Module:  ietf-yang-types
 YANG Type:    gauge64
 SMIv2 Module: INET-ADDRESS-MIB
 SMIv2 Type:   InetAutonomousSystemNumber
 YANG Module:  ietf-inet-types
 YANG Type:    as-number
 SMIv2 Module: INET-ADDRESS-MIB
 SMIv2 Type:   InetVersion
 YANG Module:  ietf-inet-types
 YANG Type:    ip-version
 SMIv2 Module: INET-ADDRESS-MIB
 SMIv2 Type:   InetPortNumber
 YANG Module:  ietf-inet-types
 YANG Type:    port-number
 SMIv2 Module: DIFFSERV-DSCP-TC
 SMIv2 Type:   Dscp
 YANG Module:  ietf-inet-types
 YANG Type:    dscp
 SMIv2 Module: IPV6-FLOW-LABEL-MIB
 SMIv2 Type:   IPv6FlowLabel
 YANG Module:  ietf-inet-types
 YANG Type:    ipv6-flow-label
 SMIv2 Module: URI-TC-MIB
 SMIv2 Type:   Uri
 YANG Module:  ietf-inet-types
 YANG Type:    uri

Appendix B. Module Prefix Generation (Informative)

 This section describes an algorithm to generate module prefixes to be
 used in the import statements.  The input of the prefix generation
 algorithm is a set of prefixes (usually derived from imported module
 names) and a specific module name to be converted into a prefix.  The
 algorithm described below produces a prefix for the given module name
 that is unique within the set of prefixes.

Schoenwaelder Standards Track [Page 35] RFC 6643 Translation of SMIv2 to YANG July 2012

                     +-----------------+--------+
                     | YANG Module     | Prefix |
                     +-----------------+--------+
                     | ietf-yang-types | yang   |
                     | ietf-inet-types | inet   |
                     | ietf-yang-smiv2 | smiv2  |
                     +-----------------+--------+
         Table 1: Special Prefixes For Well-Known YANG Modules
 o  First, some predefined translations mapping well-known YANG
    modules to short prefixes are tried (see Table 1).  If a fixed
    translation rule exists and leads to a conflict-free prefix, then
    the fixed translation is used.
 o  Otherwise, prefixes are generated by tokenizing a YANG module
    name, using hyphens as token separators.  The tokens derived from
    the module name are converted to lowercase characters.  The prefix
    then becomes the shortest sequence of tokens concatenated using
    hyphens as separators, which includes at least two tokens and
    which is unique among all prefixes used in the YANG module.
 In the worst case, the prefix derived from an SMIv2 module name
 becomes the SMIv2 module name translated to lowercase.  But on
 average, much shorter prefixes are generated.

Author's Address

 Juergen Schoenwaelder
 Jacobs University
 EMail: j.schoenwaelder@jacobs-university.de

Schoenwaelder Standards Track [Page 36]

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