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Versions: (draft-clacla-netmod-yang-model-update) 00 01

Network Working Group                                          B. Claise
Internet-Draft                                            J. Clarke, Ed.
Intended status: Standards Track                               R. Rahman
Expires: April 13, 2020                                   R. Wilton, Ed.
                                                     Cisco Systems, Inc.
                                                              B. Lengyel
                                                                Ericsson
                                                               J. Sterne
                                                                   Nokia
                                                              K. D'Souza
                                                                    AT&T
                                                        October 11, 2019


                        YANG Semantic Versioning
                   draft-verdt-netmod-yang-semver-01

Abstract

   This document specifies a scheme for applying a modified set of
   semantic versioning rules to revisions of YANG modules.
   Additionally, this document defines a revision label for this
   modified semver scheme based on the specification in draft-verdt-
   netmod-yang-module-versioning.

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 https://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 April 13, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Conventions . . . . . . . . . . . . . . . . .   3
   3.  YANG Semantic Versioning  . . . . . . . . . . . . . . . . . .   3
     3.1.  YANG Semantic Versioning Pattern  . . . . . . . . . . . .   3
     3.2.  Semantic Versioning Scheme for YANG Artifacts . . . . . .   4
       3.2.1.  Examples for YANG semantic version numbers  . . . . .   6
     3.3.  YANG Semantic Version Update Rules  . . . . . . . . . . .   7
     3.4.  Examples of the YANG Semver Label . . . . . . . . . . . .   8
       3.4.1.  Example Module Using YANG Semver  . . . . . . . . . .   8
       3.4.2.  Example of Package Using YANG Semver  . . . . . . . .  10
   4.  Import Module by Semantic Version . . . . . . . . . . . . . .  10
   5.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .  11
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  12
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   [I-D.verdt-netmod-yang-module-versioning] puts forth a number of
   concepts relating to modified rules for updating modules, a means to
   signal when a new revision of a module has non-backwards-compatible
   (NBC) changes compared to its previous revision, and a versioning
   scheme that uses the revision history as a lineage for determining
   from where a specific revision of a YANG module is derived.
   Additionally, section 3.3 of
   [I-D.verdt-netmod-yang-module-versioning] defines a revision label
   which can be used as an overlay or alias to provide additional
   context or an additional way to refer to a specific revision.

   This document defines a labeling scheme that uses modified [semver]
   rules for YANG artifacts (i.e., YANG modules and YANG packages
   [I-D.rwilton-netmod-yang-packages]) as well as the revision label



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   definition for using this scheme.  The goal of this is to add a human
   readble version label that provides compatibility information for the
   YANG artifact without one needing to compare or parse its body.  The
   label and rules defined herein represent the RECOMMENDED revision
   label scheme for IETF YANG artifacts.

2.  Terminology and Conventions

   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] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   Additionally, this document uses the following terminology:

   o  YANG artifact: YANG modules, YANG packages
      [I-D.rwilton-netmod-yang-packages], and YANG schema elements are
      examples of YANG artifacts for the purposes of this document.

3.  YANG Semantic Versioning

   This section defines YANG Semantic Versioning, explains how it is
   used with YANG artifacts, and the rules associated with changing a
   artifact's semantic version number when its contents are updated.

3.1.  YANG Semantic Versioning Pattern

   YANG artifacts that employ semantic versioning MUST use a version
   string (e.g., in revision-label or as a package version) that
   corresponds to the following pattern: X.Y.Zv.  Where:

   o  X, Y and Z are mandatory non-negative integers that are each less
      than 32768 and MUST NOT contain leading zeroes

   o  The '.' is a literal period (ASCII character 0x2e)

   o  v is an optional single character modifier that MUST be either 'm'
      or 'M' if it is specified

   Additionally, [semver] defines two specific types of metadata that
   may be appended to a semantic version string.  Pre-release metadata
   MAY be appended to a semver string after a trailing '-' character.
   Build metadata MAY be appended after a trailing '+' character.  If
   both pre-release and build metadata are present, then build metadata
   MUST follow pre-release metadata.  These optional elements MUST be
   ignored by YANG semver parsers, but are allowed in order to support




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   all of the [semver] rules.  Thus, a version lineage that follows
   strict [semver] rules is allowed for a YANG artifact.

   Other version schemes MUST NOT use version strings that match this
   same pattern.  For example, they may choose to use leading characters
   to distinguish themselves from YANG semver.

   A YANG module is defined in this document which contains single
   typedef that formally specifies this version pattern.

3.2.  Semantic Versioning Scheme for YANG Artifacts

   This document defines the YANG semantic versioning scheme that is
   used for YANG artifacts that employ the semver label.  The versioning
   scheme has the following properties:

      The YANG semantic versioning scheme is extended from version 2.0.0
      of the semantic versioning scheme defined at semver.org [semver]
      to cover the additional requirements for the management of YANG
      artifact lifecyles that cannot be addressed using the semver.org
      2.0.0 versioning scheme alone.

      Unlike the [semver] versioning scheme, the YANG semantic
      versioning scheme supports limited updates to older versions of
      YANG artifacts, to allow for bug fixes and enhancements to
      artifact versions that are not the latest.  However, it does not
      provide for the unlimited branching and updating of older
      revisions which are documented by the general rules in
      [I-D.verdt-netmod-yang-module-versioning].

      YANG artifacts that follow the [semver] versioning scheme are
      fully compatible with implementations that understand the YANG
      semantic versioning scheme defined in this document.

      If updates are always restricted to the latest revision of the
      artifact only, then the version numbers used by the YANG semantic
      versioning scheme are exactly the same as those defined by the
      [semver] versioning scheme.

   Every YANG module versioned using the YANG semantic versioning scheme
   specifies the module's semantic version number as the argument to the
   'rev:revision-label' statement.

   Because the rules put forth in
   [I-D.verdt-netmod-yang-module-versioning] are designed to work well
   with existing versions of YANG and allow for artifact authors to
   migrate to this scheme, it is not expected that all revisions of a
   given YANG artifact will have a semantic version label.  For example,



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   the first revision of a module may have been produced before this
   scheme was available.

   YANG packages that make use of this semantic versioning scheme will
   have their semantic version as the value of the "revision_label"
   property.

   As stated above, the YANG semver version number is expressed as a
   string of the form: 'X.Y.Zv'; where X, Y, and Z each represent non-
   negative integers smaller than 32768 without leading zeroes, and v
   represents an optional single character suffix: 'm' or 'M'.

   o  'X' is the MAJOR version.  Changes in the major version number
      indicate changes that are non-backwards-compatible to versions
      with a lower major version number.

   o  'Y' is the MINOR version.  Changes in the minor version number
      indicate changes that are backwards-compatible to versions with
      the same major version number, but a lower minor version number
      and no patch 'm' or 'M' modifier.

   o  'Zv' is the PATCH version and modifier.  Changes in the patch
      version number can indicate editorial, backwards-compatible, or
      non-backwards-compatible changes relative to versions with the
      same major and minor version numbers, but lower patch version
      number, depending on what form modifier 'v' takes:

      *  If the modifier letter is absent, the change represents an
         editorial change.  An editorial change is defined to be a
         change in the YANG artifact's content that does not affect the
         semantic meaning or functionality provided by the artifact in
         any way.  An example is correcting a spelling mistake in the
         description of a leaf within a YANG module.  Note:
         restructuring how a module uses, or does not use, submodules is
         treated as an editorial level change on the condition that
         there is no change in the module's semantic behavior due to the
         restructuring.

      *  If, however, the modifier letter is present, the meaning is
         described below:

      *  'm' - the change represents a backwards-compatible change

      *  'M' - the change represents a non-backwards-compatible change

   The YANG articact name and YANG semantic version number uniquely
   identifies a revision of said artifact.  There MUST NOT be multiple
   instances of a YANG artifact definition with the same name and YANG



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   semantic version number but different content (and in the case of
   modules, different revision dates).

   There MUST NOT be multiple versions of a YANG artifact that have the
   same MAJOR, MINOR and PATCH version numbers, but different patch
   modifier letters.  E.g., artifact version "1.2.3M" MUST NOT be
   defined if artifact version "1.2.3" has already been defined.

3.2.1.  Examples for YANG semantic version numbers

   The following diagram and explanation illustrates how YANG semantic
   version numbers work.

   Example YANG semantic version numbers for an example artifact:

           0.1.0
             |
           0.2.0
             |
           1.0.0
             |  \
             |   1.1.0 -> 1.1.1m -> 1.1.2M
             |    |
             |   1.2.0 -> 1.2.1M -> 1.2.2M
             |    |
             |   1.3.0 -> 1.3.1
             |
           2.0.0
             |
           3.0.0
                \
                 3.1.0

   Assume the tree diagram above illustrates how an example YANG
   module's version history might evolve.  For example, the tree might
   represent the following changes, listed in chronological order from
   oldest revision to newest:

      0.1.0 - first beta module version

      0.2.0 - second beta module version (with NBC changes)

      1.0.0 - first release (may have NBC changes from 0.2.0)

      1.1.0 - added new functionality, leaf "foo" (BC)

      1.2.0 - added new functionality, leaf "baz" (BC)




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      1.3.0 - improve existing functionality, added leaf "foo-64" (BC)

      1.3.1 - improve description wording for "foo-64" (Editorial)

      1.1.1m - backport "foo-64" leaf to 1.1.x to avoid implementing
      "baz" from 1.2.0 (BC)

      2.0.0 - change existing model for performance reasons, e.g. re-key
      list (NBC)

      1.1.2M - NBC point bug fix, not required in 2.0.0 due to model
      changes (NBC)

      3.0.0 - NBC bugfix, rename "baz" to "bar"; also add new BC leaf
      "wibble"; (NBC)

      1.2.1M - backport NBC fix, changing "baz" to "bar"

      1.2.2M - backport "wibble".  This is a BC change but "M" modifier
      is sticky.

      3.1.0 - introduce new leaf "wobble" (BC)

   The partial ordering relationships based on the semantic versioning
   numbers can be defined as follows:

      1.0.0 < 1.1.0 < 1.2.0 < 1.3.0 < 2.0.0 < 3.0.0 < 3.1.0

      1.0.0 < 1.1.0 < 1.1.1m < 1.1.2M

      1.0.0 < 1.1.0 < 1.2.0 < 1.2.1M < 1.2.2M

   There is no ordering relationship between 1.1.1M and either 1.2.0 or
   1.2.1M, except that they share the common ancestor of 1.1.0.

   Looking at the version number alone, the module definition in 2.0.0
   does not necessarily contain the contents of 1.3.0.  However, the
   module revision history in 2.0.0 may well indicate that it was edited
   from module version 1.3.0.

3.3.  YANG Semantic Version Update Rules

   When a new revision of an artifact is produced, then the following
   rules define how the YANG semantic version number for the new
   artifact revision is calculated, based on the changes between the two
   artifact revisions, and the YANG semantic version number of the base
   artifact revision from which the changes are derived:




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   1.  If an artifact is being updated in a non-backwards-compatible
       way, then the artifact version "X.Y.Z[m|M]" MUST be updated to
       "X+1.0.0" unless that artifact version has already been defined
       with different content, in which case the artifact version
       "X.Y.Z+1M" MUST be used instead.

   2.  If an artifact is being updated in a backwards-compatible way,
       then the next version number depends on the format of the current
       version number:

       i     "X.Y.Z" - the artifact version MUST be updated to
             "X.Y+1.0", unless that artifact version has already been
             defined with different content, when the artifact version
             MUST be updated to "X.Y.Z+1m" instead.

       ii    "X.Y.Zm" - the artifact version MUST be updated to
             "X.Y.Z+1m".

       iii   "X.Y.ZM" - the artifact version MUST be updated to
             "X.Y.Z+1M".

   3.  If an artifact is being updated in an editorial way, then the
       next version number depends on the format of the current version
       number:

       i     "X.Y.Z" - the artifact version MUST be updated to "X.Y.Z+1"

       ii    "X.Y.Zm" - the artifact version MUST be updated to
             "X.Y.Z+1m".

       iii   "X.Y.ZM" - the artifact version MUST be updated to
             "X.Y.Z+1M".

   4.  YANG artifact semantic version numbers beginning with 0, i.e
       "0.X.Y" are regarded as beta definitions and need not follow the
       rules above.  Either the MINOR or PATCH version numbers may be
       updated, regardless of whether the changes are non-backwards-
       compatible, backwards-compatible, or editorial.

3.4.  Examples of the YANG Semver Label

3.4.1.  Example Module Using YANG Semver

   Below is a sample YANG module that uses the YANG semver revision
   label based on the rules defined in this document.

       module yang-module-name {




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         namespace "name-space";
         prefix "prefix-name";

         import ietf-yang-revisions { prefix "rev"; }

         description
           "to be completed";

         revision 2018-02-28 {
           description "Added leaf 'wobble'";
           rev:revision-label "3.1.0";
         }

         revision 2017-12-31 {
           description "Rename 'baz' to 'bar', added leaf 'wibble'";
           rev:revision-label "3.0.0";
           rev:nbc-changes;
         }

         revision 2017-10-30 {
           description "Change the module structure";
           rev:revision-label "2.0.0";
           rev:nbc-changes;
         }

         revision 2017-08-30 {
           description "Clarified description of 'foo-64' leaf";
           rev:revision-label "1.3.1";
         }

         revision 2017-07-30 {
           description "Added leaf foo-64";
           rev:revision-label "1.3.0";
         }

         revision 2017-04-20 {
           description "Add new functionality, leaf 'baz'";
           rev:revision-label "1.2.0";
         }

         revision 2017-04-03 {
           description "Add new functionality, leaf 'foo'";
           rev:revision-label "1.1.0";
         }

         revision 2017-04-03 {
           description "First release version.";
           rev:revision-label "1.0.0";



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         }

         // Note: semver rules do not apply to 0.X.Y labels.

         revision 2017-01-30 {
           description "NBC changes to initial revision";
           semver:module-version "0.2.0";
         }

         revision 2017-01-26 {
           description "Initial module version";
           semver:module-version "0.1.0";
         }

         //YANG module definition starts here

3.4.2.  Example of Package Using YANG Semver

   Below is an example YANG package that uses the semver revision label
   based on the rules defined in this document.

      {
        "ietf-yang-instance-data:instance-data-set": {
          "name": "example-yang-pkg",
          "target-ptr": "TBD",
          "timestamp": "2018-09-06T17:00:00Z",
          "description": "Example IETF package definition",
          "content-data": {
            "ietf-yang-package:yang-package": {
              "name": "example-yang-pkg",
              "version": "1.3.1",
              ...
     }

4.  Import Module by Semantic Version

   [I-D.verdt-netmod-yang-module-versioning] allows for imports to be
   done based on a module or a derived revision of a module.  The
   rev:revision-or-derived statement can specify either a revision date
   or a revision label.  When importing by semver, the YANG semver
   revision label value MAY be used as an argument to rev:revision-or-
   derived.  In so, any module which has that semver label as its latest
   revision label or has that label in its revision history can be used
   to satisfy the import requirement.  For example:

           import example-module {
             rev:revision-or-derived "3.0.0";
           }



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   Note: the import lookup does not stop when a non-backward-compatible
   change is encountered.  That is, if module B imports a module A at or
   derived from version 2.0.0, resolving that import will pass through a
   revision of module A with version 2.1.0M in order to determine if the
   present instance of module A derives from 2.0.0.

5.  YANG Module

   This YANG module contains the typedef for the YANG semantic version.


<CODE BEGINS> file "ietf-yang-semver@2019-09-06.yang"
  module ietf-yang-semver {
    yang-version 1.1;
    namespace "urn:ietf:params:xml:ns:yang:ietf-yang-semver";
    prefix yangver;

    organization
      "IETF NETMOD (Network Modeling) Working Group";
    contact
      "WG Web:   <http://tools.ietf.org/wg/netmod/>
       WG List:  <mailto:netmod@ietf.org>

       Author:   Joe Clarke
                 <mailto:jclarke@cisco.com>";
    description
      "This module provides type and grouping definitions for YANG
       packages.

       Copyright (c) 2019 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.: update the date below with the date of RFC publication
    // and remove this note.
    // RFC Ed.: replace XXXX with actual RFC number and remove this
    // note.

    revision 2019-09-06 {



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      description
        "Initial revision";
      reference
        "RFC XXXX: YANG Semantic Versioning.";
    }

    /*
     * Typedefs
     */

    typedef version {
      type string {
        pattern '\d+[.]\d+[.]\d+[mM]?(-[\w\d.]+)?([+][\w\d\.]+)?';
      }
      description
        "Represents a YANG semantic version number.  Note:
         additional rules apply to the dot-separated numeric identifiers
         which are spelled out in the reference for this typedef.";
      reference
        "RFC XXXX: YANG Semantic Versioning.";
    }
  }
    <CODE ENDS>


6.  Contributors

   This document grew out of the YANG module versioning design team that
   started after IETF 101.  The design team consists of the following
   members whom have worked on the YANG versioning project:

   o  Balazs Lengyel

   o  Benoit Claise

   o  Ebben Aries

   o  Jason Sterne

   o  Joe Clarke

   o  Juergen Schoenwaelder

   o  Mahesh Jethanandani

   o  Michael (Wangzitao)

   o  Qin Wu



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   o  Reshad Rahman

   o  Rob Wilton

   The initial revision of this document was refactored and built upon
   [I-D.clacla-netmod-yang-model-update].

   Discussons on the use of Semver for YANG versioning has been held
   with authors of the OpenConfig YANG models based on their own
   [openconfigsemver].  We would like thank both Anees Shaikh and Rob
   Shakir for their input into this problem space.

7.  Security Considerations

   The document does not define any new protocol or data model.  There
   are no security impacts.

8.  IANA Considerations

   None.

9.  References

9.1.  Normative References

   [I-D.verdt-netmod-yang-module-versioning]
              Claise, B., Clarke, J., Rahman, R., Wilton, R., Lengyel,
              B., Sterne, J., and K. D'Souza, "Updated YANG Module
              Revision Handling", draft-verdt-netmod-yang-module-
              versioning-00 (work in progress), July 2019.

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

   [RFC7895]  Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
              Library", RFC 7895, DOI 10.17487/RFC7895, June 2016,
              <https://www.rfc-editor.org/info/rfc7895>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8525]  Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
              and R. Wilton, "YANG Library", RFC 8525,
              DOI 10.17487/RFC8525, March 2019,
              <https://www.rfc-editor.org/info/rfc8525>.



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9.2.  Informative References

   [I-D.clacla-netmod-yang-model-update]
              Claise, B., Clarke, J., Lengyel, B., and K. D'Souza, "New
              YANG Module Update Procedure", draft-clacla-netmod-yang-
              model-update-06 (work in progress), July 2018.

   [I-D.ietf-netmod-yang-instance-file-format]
              Lengyel, B. and B. Claise, "YANG Instance Data File
              Format", draft-ietf-netmod-yang-instance-file-format-04
              (work in progress), August 2019.

   [I-D.rwilton-netmod-yang-packages]
              Wilton, R., "YANG Packages", draft-rwilton-netmod-yang-
              packages-01 (work in progress), March 2019.

   [openconfigsemver]
              "Semantic Versioning for Openconfig Models",
              <http://www.openconfig.net/docs/semver/>.

   [semver]   "Semantic Versioning 2.0.0", <https://www.semver.org>.

Authors' Addresses

   Benoit Claise
   Cisco Systems, Inc.
   De Kleetlaan 6a b1
   1831 Diegem
   Belgium

   Phone: +32 2 704 5622
   Email: bclaise@cisco.com


   Joe Clarke (editor)
   Cisco Systems, Inc.
   7200-12 Kit Creek Rd
   Research Triangle Park, North Carolina
   United States of America

   Phone: +1-919-392-2867
   Email: jclarke@cisco.com


   Reshad Rahman
   Cisco Systems, Inc.

   Email: rrahman@cisco.com



Claise, et al.           Expires April 13, 2020                [Page 14]


Internet-Draft                 YANG Semver                  October 2019


   Robert Wilton (editor)
   Cisco Systems, Inc.

   Email: rwilton@cisco.com


   Balazs Lengyel
   Ericsson
   Magyar Tudosok Korutja
   1117 Budapest
   Hungary

   Phone: +36-70-330-7909
   Email: balazs.lengyel@ericsson.com


   Jason Sterne
   Nokia

   Email: jason.sterne@nokia.com


   Kevin D'Souza
   AT&T
   200 S. Laurel Ave
   Middletown, NJ
   United States of America

   Email: kd6913@att.com






















Claise, et al.           Expires April 13, 2020                [Page 15]


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