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Versions: 00 draft-veillette-core-yang-library

Internet Engineering Task Force                        M. Veillette, Ed.
Internet-Draft                                   Trilliant Networks Inc.
Intended status: Standards Track                         August 23, 2016
Expires: February 24, 2017


                    Constrained YANG Module Library
                  draft-veillette-core-cool-library-00

Abstract

   This document describes a library, which provides information about
   all YANG modules implemented by a CoOL server endpoint.  A simple
   caching mechanism is provided to minimize retrieval of this
   information by CoOL clients.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 24, 2017.

Copyright Notice

   Copyright (c) 2016 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.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Notation  . . . . . . . . . . . . . . . . . .   2
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Tree diagram  . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Description . . . . . . . . . . . . . . . . . . . . . . .   4
       3.2.1.  modules-state . . . . . . . . . . . . . . . . . . . .   4
       3.2.2.  modules-state/module-set-id . . . . . . . . . . . . .   4
       3.2.3.  modules-state/module  . . . . . . . . . . . . . . . .   4
   4.  YANG Module "ietf-cool-library" . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  YANG Module Registry  . . . . . . . . . . . . . . . . . .  10
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   The YANG module defined in this meno is available to CoOL clients to
   discover the different YANG data models supported by a CoOL server
   endpoint.  The following YANG module information is needed by client
   applications to fully utilize the YANG data modeling language:

   o  module list: The list of YANG modules implemented by the CoOL
      server endpoint, each module is identified by its SID and
      revision.

   o  submodule list: The list of YANG submodules included by each
      module, each submodule is identified by its SID and revision.

   o  feature list: The list of features supported by each YANG module,
      each feature is identified by its SID.

   o  deviation list: The list of YANG modules used for deviation
      statements associated with each YANG module, each module is
      identified by its SID and revision.

2.  Terminology and Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   The following terms are defined in [I-D.ietf-netmod-rfc6020bis]:



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   o  module

   o  submodule

   o  feature

   o  deviation

   The following terms are defined in [I-D.somaraju-core-sid]:

   o  Structured IDentifier (SID)

   The following terms are defined in [I-D.veillette-core-cool]:

   o  CoOL client

   o  CoOL server

   o  endpoint

   The following terms are used within this document:

   o  library: a collection of YANG modules used by a server endpoint

3.  Overview

   The "ietf-cool-library" module provides information about the YANG
   library used by a server endpoint.  This module is defined using YANG
   version 1, but it supports the description of YANG modules written in
   any revision of YANG.

3.1.  Tree diagram

   A simplified graphical representation of the YANG module specified in
   this document (ietf-cool-library) is provided below.  The meaning of
   the symbols in this diagram is as follows:

   o  Brackets "[" and "]" enclose list keys.

   o  Abbreviations before data node names: "rw" means configuration
      data (read-write) and "ro" state data (read-only).

   o  Symbols after data node names: "?" means an optional node, "!"
      means a presence container, and "*" denotes a list and leaf-list.







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   module: ietf-cool-library
      +--ro modules-state
         +--ro module-set-id    union
         +--ro module* [sid revision]
            +--ro sid                 sid
            +--ro revision            revision
            +--ro feature*            sid
            +--ro deviation* [sid revision]
            |  +--ro sid         sid
            |  +--ro revision    revision
            +--ro conformance-type    enumeration
            +--ro submodule* [sid revision]
               +--ro sid         sid
               +--ro revision    revision
   notifications:
      +---n cool-library-change
         +--ro module-set-id    -> /modules-state/module-set-id

3.2.  Description

3.2.1.  modules-state

   This mandatory container holds the module set identifier and the list
   of modules supported by the server endpoint.

3.2.2.  modules-state/module-set-id

   This mandatory leaf contains an identifier representing the current
   set of modules and submodules used by a server endpoint.  This
   identifier is endpoint-specific when implemented as unit32 or shared
   between multiple endpoints on one or multiple servers when
   implemented as identityref.  The value of this leaf MUST change
   whenever the set of modules and submodules in the library changes.
   There is no requirement that the same set always results in the same
   module-set-id value.

   This leaf allows a client to fetch the module list once, cache it,
   and only re-fetch it if the value of this leaf has been changed.

   If the value of this leaf changes, the server also generates a "cool-
   library-change" notification, with the new value of "module-set-id".

3.2.3.  modules-state/module

   This mandatory list contains one entry for each YANG module supported
   by the server endpoint.  There MUST be an entry in this list for each
   revision of each YANG module that is used by the server.




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4.  YANG Module "ietf-cool-library"

   RFC Ed.: update the date below with the date of RFC publication and
   remove this note.

   <CODE BEGINS> file "ietf-cool-library@2016-06-01.yang"
   module ietf-cool-library {
     namespace "urn:ietf:params:xml:ns:yang:ietf-cool-library";
     prefix "coollib";

     organization
       "IETF CORE (Constrained RESTful Environments) Working Group";

     contact
       "WG Web:   <http://datatracker.ietf.org/wg/core/>

        WG List:  <mailto:core@ietf.org>

        WG Chair: Carsten Bormann
                  <mailto:cabo@tzi.org>

        WG Chair: Jaime Jimenez
                  <mailto:jaime.jimenez@ericsson.com>

        Editor:   Michel Veillette
                  <mailto:michel.veillette@trilliantinc.com>";

     description
       "This module contains the list of YANG modules and submodules
       implemented by a CoOL server endpoint.

        Copyright (c) 2016 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
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; see
        the RFC itself for full legal notices.";

     // RFC Ed.: replace XXXX with actual RFC number and remove
     // this note.

     // RFC Ed.: update the date below with the date of the RFC



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     // publication and remove this note.

     // RFC Ed.: update [I-D.somaraju-core-sid] with actual RFC
     // number and remove this note.

     revision 2016-06-01 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: Contrained YANG Module Library.";
     }

     /*
      * Typedefs
      */

     typedef revision {
       type binary {
         length "4";
       }
       description
         "Revision date encoded as a binary string as follow:
         - First byte = Century
         - Second byte = Year (0 to 99)
         - Third byte = Month (1 = January to 12 = december)
         - Forth byte = Day (1 to 31)";
     }

     typedef sid {
       type uint32;
       description
         "Unique identifier assigned to different YANG items
         such as data nodes, RPCs and actions, notifications,
         modules, sub-modules, features and deviations. The SID
         registration process is defined in
         [I-D.somaraju-core-sid].";
     }

     /*
      * Groupings
      */

     grouping identification-info {
       description
         "YANG modules and submodules identification information.";

       leaf sid {
         type sid;



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         mandatory true;
         description
           "SID assigned to this module or submodule.";
       }

       leaf revision {
         type revision;
         description
           "Revision date assigned to this module or submodule.
           A zero-length binary string is used if no revision statement
           is present in the YANG module or submodule.";
       }
     }

     identity module-set {
         description
           "Base identity from which shared module-set identifiers
           are derived.";
       }

     /*
      * Operational state data nodes
      */

     container modules-state {
       config false;
       description
         "Contain information about the different data models
         implement by a CoOL endpoint.";

       leaf module-set-id {
         type union {
           type uint32;
           type identityref {
             base "coollib:module-set";
           }
         }
         mandatory true;
         description
           "Identifier representing the current set of modules
           and submodules listed in the 'module' list. This
           identifier is endpoint-specific when implemented as
           unit32 or shared between multiple endpoints on one
           or multiple servers when implemented as identityref.
           The server MUST change the value of this leaf each
           time the information represented by the 'module'
           list instance changes.";
       }



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       list module {
         key "sid revision";
         description
           "Each entry represents one revision of one module
            currently supported by the server endpoint.";

         uses identification-info;

         leaf-list feature {
           type sid;
           description
             "List of YANG features from this module that are
             supported by the server endpoint, regardless whether
             they are defined in the module or any included
             submodule.";
         }

         list deviation {
           key "sid revision";
           description
             "List of YANG deviation modules used by this server
             endpoint to modify the conformance of the module
             associated with this entry.  Note that the same module
             can be used for deviations for multiple modules, so the
             same entry MAY appear within multiple 'module' entries.

             The deviation module MUST be present in the 'module'
             list, with the same sid and revision values.
             The 'conformance-type' value will be 'implement' for
             the deviation module.";

           uses identification-info;
         }

         leaf conformance-type {
           type enumeration {
             enum implement {
               value 0;
               description
                 "Indicates that the server endpoint implements one or
                 more protocol-accessible objects defined in the YANG
                 module identified in this entry.  This includes
                 deviation statements defined in the module.

                 For YANG version 1.1 modules, there is at most one
                 module entry with conformance type 'implement' for a
                 particular module, since YANG 1.1 requires that
                 at most one revision of a module is implemented.



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                 For YANG version 1 modules, there SHOULD NOT be more
                 than one module entry for a particular module.";
             }
             enum import {
               value 1;
               description
                 "Indicates that the server endpoint imports reusable
                 definitions from the specified revision of the module,
                 but does not implement any protocol accessible objects
                 from this revision.

                 Multiple module entries for the same module MAY
                 exist. This can occur if multiple modules import the
                 same module, but specify different revision-dates in
                 the import statements.";
             }
           }
           mandatory true;
           description
             "Indicates the type of conformance the server endpoint is
             claiming for the YANG module identified by this entry.";
         }

         list submodule {
           key "sid revision";
           description
             "Each entry represents one submodule within the
              parent module.";
           uses identification-info;
         }
       }
     }

     /*
      * Notifications
      */

     notification cool-library-change {
       description
         "Generated when the set of modules and submodules supported
         by the server endpoint has changed.";

       leaf module-set-id {
         type leafref {
           path "/coollib:modules-state/coollib:module-set-id";
         }
         mandatory true;
         description



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           "Contains the module-set-id value representing the
           set of modules and submodules supported at the server
           endpoint at the time the notification is generated.";
       }
     }
   }
   <CODE ENDS>

5.  IANA Considerations

5.1.  YANG Module Registry

   This document registers one YANG module in the YANG Module Names
   registry [I-D.ietf-netmod-rfc6020bis].

   name: ietf-cool-library

   namespace: urn:ietf:params:xml:ns:yang:ietf-cool-library

   prefix: coollib

   reference: RFC XXXX

   // RFC Ed.: replace XXXX with RFC number and remove this note

6.  Security Considerations

   This YANG module is designed to be accessed via the CoOL protocol
   [I-D.veillette-core-cool].  Some of the readable data nodes in this
   YANG module may be considered sensitive or vulnerable in some network
   environments.  It is thus important to control read access to these
   data nodes.

   Specifically, the 'module' list may help an attacker identify the
   server capabilities and server implementations with known bugs.
   Server vulnerabilities may be specific to particular modules, module
   revisions, module features, or even module deviations.  This
   information is included in each module entry.  For example, if a
   particular operation on a particular data node is known to cause a
   server to crash or significantly degrade device performance, then the
   module list information will help an attacker identify server
   implementations with such a defect, in order to launch a denial of
   service attack on the device.








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7.  Acknowledgments

   The YANG module defined by this memo have been derived from an
   already existing YANG module targeting the RESTconf protocol
   [I-D.ietf-netconf-restconf].  We will like to thank the authors of
   this prior work [I-D.ietf-netconf-yang-library] which have been
   essential for the development of "ietf-cool-library" targeting the
   Constrained Objects Language [I-D.veillette-core-cool] protocol.  The
   authors would also like to thank Andy Bierman for his recommendations
   and his review of the resulting YANG module.

8.  References

8.1.  Normative References

   [I-D.ietf-netmod-rfc6020bis]
              Bjorklund, M., "The YANG 1.1 Data Modeling Language",
              draft-ietf-netmod-rfc6020bis-14 (work in progress), June
              2016.

   [I-D.somaraju-core-sid]
              Somaraju, A., Veillette, M., Pelov, A., Turner, R., and A.
              Minaburo, "Structure Identifier (SID)", draft-somaraju-
              core-sid-01 (work in progress), July 2016.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

8.2.  Informative References

   [I-D.ietf-netconf-restconf]
              Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", draft-ietf-netconf-restconf-16 (work in
              progress), August 2016.

   [I-D.ietf-netconf-yang-library]
              Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
              Library", draft-ietf-netconf-yang-library-06 (work in
              progress), April 2016.

   [I-D.veillette-core-cool]
              Veillette, M., Pelov, A., Somaraju, A., Turner, R., and A.
              Minaburo, "Constrained Objects Language", draft-veillette-
              core-cool-02 (work in progress), July 2016.





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Author's Address

   Michel Veillette (editor)
   Trilliant Networks Inc.
   610 Rue du Luxembourg
   Granby, Quebec  J2J 2V2
   Canada

   Phone: +14503750556
   Email: michel.veillette@trilliantinc.com









































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