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Versions: 00

Network Working Group                                        A. Minaburo
Internet-Draft                                                    Acklio
Intended status: Informational                                L. Toutain
Expires: January 2, 2017       Institut MINES TELECOM ; TELECOM Bretagne
                                                            July 1, 2016


     YANG module for LPWAN Static Context Header Compression (SCHC)
             draft-toutain-lpwan-yang-static-context-hc-00

Abstract

   This document describes a yang model for Static Context Header
   Compression.  A generic module is defined, that can be applied for
   any headers.  A specific model for the IPv6 UDP protocol stack is
   also proposed.

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 January 2, 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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1.  Introduction

   [I-D.toutain-6lpwa-ipv6-static-context-hc] defines a compression
   technique for LPWA network based on static context.  The context is
   known by both ends.  A context contains an ordered list of rules (cf.
   Figure 1).  Each rule is a vector of entries.  Each entry is composed
   of a field descriptor, a prescribed matching value, a matching rule
   for the compression side, a matching rule for the decompression side
   and a compression/decompression action function.



            +---------------------------------------------------------------------+
            |                      Rule N                                         |
       +---------------------------------------------------------------------+    |
       |                    Rule i                                           |    |
+---------------------------------------------------------------------+      |    |
|                    Rule 1                                           |      |    |
|   +---------+-------+------------+--------------+-----------------+ |      |    |
|   | Field 1 | Value |match. comp.| match decomp | Action function | |      |    |
|   +---------+-------+------------+--------------+-----------------+ |      |    |
|   | Field 2 | Value |match. comp.| match decomp | Action function | |      |    |
|   +---------+-------+------------+--------------+-----------------+ |      |    |
|   | ...     | ...   |...         | ...          | ...             | |      |    |
|   +---------+-------+------------+--------------+-----------------+ |      |----+
|   | Field N | Value |match. comp.| match decomp | Action function | |      |
|   +---------+-------+------------+--------------+-----------------+ |------+
|                                                                     |
+---------------------------------------------------------------------+


                          Figure 1: Context in LC

2.  YANG types

2.1.  Value field

   A value may be associated for each field in a rule.  The value's type
   depends of the field.  It can be an integer, a prefix, a string, or
   any other type carried by the field.  The LPWA-types regroups all the
   possibles values.  Figure 2 gives its definition.










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        typedef LPWA-types {
                type union {
                        type uint8;
                        type uint16;
                        type uint32;
                        type uint64;
                        type inet:ipv6-prefix; // better use int64, more comptact ?
                        type string;
                }
        }



                           Figure 2: Value types

   Note that as defined in [I-D.toutain-6lpwa-ipv6-static-context-hc],
   ESprefix and LCprefix can be of inet:ipv6-prefix type, but this type
   derives from ASCII characters, a binary representation such as uint64
   will be more compact.

2.2.  Matching operator

   A matching operator is used to check the field value stored in the
   rule against the value contained in the header field.  If there is no
   matching the rule is not selected.  Two instances of matching
   operator are defined to allow the rule selection from informations
   contained either the compressed or uncompressed header.
   [I-D.toutain-6lpwa-ipv6-static-context-hc] defines three operators:

   o  equal: the rule's value must be equal to the packet header value
      for a specific field.

   o  lsb(L): this operator compare the most significant bits.  The
      operator takes one argument representing the length of least
      significant bit part, which will be ignored during the matching
      but sent if the rule matches.

   o  ignore: there is no check for this field.













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           grouping matching-operator {
                   leaf operator {
                           type enumeration {
                           enum operator-equal;
                           enum operator-lsb;
                           enum operator-ignore;
                           }
                   }
                   choice operator-lsb {
                           leaf lsb-length {
                                   type LPWA-types;
                           }
                   }



                       Figure 3: Matching operators

   Figure 3 represents the matching operator type definition.

2.3.  action function

   [I-D.toutain-6lpwa-ipv6-static-context-hc] defines some actions
   functions.  Action functions tell how to compress and inversely how
   to decompress the field.  They are defined in Figure 4


       typedef LPWA-action-functions {
          type enumeration {
                enum elided;
                enum send-value;
                enum compute-IPv6-length;
                enum compute-UDP-length;
                enum compute-UDP-checksum;
                enum ESiid-DID;
                enum LAiid-DID;
          }
       }


                        Figure 4: Action functions

3.  Generic rule definition

   Each rule's row is defined by several leaves, composed of:

   o  a field name that can be used for debugging purpose,




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   o  a field position which will be used as a key,

   o  a field value containing the value that will be compared,

   o  two matching operators for rule selection: one for compression and
      the other for decompression,

   o  an action function to compress/uncompress the field.

   Figure 5 defines the format.


           grouping field-context {
                   leaf field-name {
                           type string;
                   }
                   leaf field-pos {
                           type int8;
                   }
                   leaf field-value {
                           type LPWA-types;
                   }
                   container field-compression-match {
                           uses matching-operator;
                   }
                   container field-decompression-match {
                           uses matching-operator;
                   }
                   leaf action-function {
                           type LPWA-action-functions;
                   }
           }



                        Figure 5: Action functions

4.  Yang static context model

   This lead to the generic rule definition, represented Figure 6.











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      +--rw generic-rules
      |  +--rw context-name?    string
      |  +--rw context-rules* [rule-id]
      |     +--rw rule-name?     string
      |     +--rw rule-id        int8
      |     +--rw rule-fields* [field-pos]
      |        +--rw field-name?                  string
      |        +--rw field-pos                    int8
      |        +--rw field-value?                 LPWA-types
      |        +--rw field-compression-match
      |        |  +--rw operator?     enumeration
      |        |  +--rw (operator-lsb)?
      |        |     +--:(lsb-length)
      |        |        +--rw lsb-length?   LPWA-types
      |        +--rw field-decompression-match
      |        |  +--rw operator?     enumeration
      |        |  +--rw (operator-lsb)?
      |        |     +--:(lsb-length)
      |        |        +--rw lsb-length?   LPWA-types
      |        +--rw action-function?             LPWA-action-functions



                       Figure 6: Generic module tree

   A context is defined by a set of rules identified through a rule-id.
   Each rule contains a set of field definitions identified through a
   field position.  Figure 7 gives the yang definition of this module.























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           container generic-rules {
                   leaf context-name {
                           type string;
                   }
                   list context-rules {
                       key rule-id;

                           leaf rule-name {
                                   type string;
                           }
                           leaf rule-id {
                                   type int8;
                           }
                           list rule-fields {
                               key field-pos;
                                   uses field-context;
                           }
                   }

           }


              Figure 7: Yang definition of the generic module

   Specific modules can be defined based on the same principle.
   Figure 8 represents the module defined in
   [I-D.toutain-6lpwa-ipv6-static-context-hc].


        container IPv6-UDP-rules {
                leaf context-name {
                        type string;
                }
                list context-rules {
                    key rule-id;

                        leaf rule-name {
                                type string;
                        }
                        leaf rule-id {
                                type int8;
                        }
                        container shim-id {
                                uses field-context {
                                        refine field-name {
                                                default "shim identifier";
                                        }
                                        refine field-pos {



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                                                default 0;
                                        }
                                        refine field-value {
                                                default 0;
                                        }
                                }
                        }
                        container ES-device-id {
                                uses field-context {
                                        refine field-name {
                                                default "End System device identifier";
                                        }
                                        refine field-pos {
                                                default 1;
                                        }
                                        refine field-value {
                                                default 0;
                                        }
                                }
                        }
                        container ipv6-version {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 Version";
                                        }
                                        refine field-pos {
                                                default 2;
                                        }
                                        refine field-value {
                                                default 6;
                                        }
                                }
                        }
                        container ipv6-diffserv {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 Diffserv";
                                        }
                                        refine field-pos {
                                                default 3;
                                        }
                                        refine field-value {
                                                default 0;
                                        }
                                }
                        }
                        container ipv6-flow-label {
                                uses field-context {



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                                        refine field-name {
                                                default "IPv6 Flow Label";
                                        }
                                        refine field-pos {
                                                default 4;
                                        }
                                        refine field-value {
                                                default 0;
                                        }
                                }
                        }
                        container ipv6-length {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 length";
                                        }
                                        refine field-pos {
                                                default 5;
                                        }
                                }
                        }
                        container ipv6-next-header {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 next header";
                                        }
                                        refine field-pos {
                                                default 6;
                                        }
                                        refine field-value {
                                                default 17;
                                        }
                                }
                        }
                        container ipv6-hop-limit {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 Hop Limit";
                                        }
                                        refine field-pos {
                                                default 7;
                                        }
                                        refine field-value {
                                                default 17;
                                        }
                                }
                        }
                        container ipv6-ES-prefix {



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                                uses field-context {
                                        refine field-name {
                                                default "IPv6 ES Prefix";
                                        }
                                        refine field-pos {
                                                default 8;
                                        }
                                }
                        }
                        container ipv6-ES-iid {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 ES Interface ID";
                                        }
                                        refine field-pos {
                                                default 9;
                                        }
                                }
                        }
                        container ipv6-LC-prefix {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 LC Prefix";
                                        }
                                        refine field-pos {
                                                default 10;
                                        }
                                }
                        }
                        container ipv6-LC-iid {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 LC Interface ID";
                                        }
                                        refine field-pos {
                                                default 11;
                                        }
                                }
                        }

                        container udp-ES-port {
                                uses field-context {
                                        refine field-name {
                                                default "UDP ES port";
                                        }
                                        refine field-pos {
                                                default 12;
                                        }



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                                }
                        }
                        container udp-LC-port {
                                uses field-context {
                                        refine field-name {
                                                default "UDP LC port";
                                        }
                                        refine field-pos {
                                                default 13;
                                        }
                                }
                        }

                }

        }


           Figure 8: Yang definition of the IPv6 UDP compression

   Each field is specifically defined with some default values.

5.  Use of COMI/CoOL

   COMI/CoOL [I-D.veillette-core-cool] defines a management function set
   adapted to constrained networks.  In the generic format, the keys to
   access a field (referenced as field-SID) are the rule-id and the
   field-pos.  Therefore to modify one value for a specific rule and a
   specific field, a iPATCH will be used as defined in Figure 9


   iPATCH /c Content-Format(application/cool-value-pairs+cbor)
   [
     [field-SID, rule-id, field-pos], value
   ]


           Figure 9: Yang definition of the IPv6 UDP compression

   For a specific context, only the rule-id has to be specified in the
   iPATH methods since each field has its own sid value.

6.  Acknowledgement

   The authors would like to thank Michel Veillette, Alexander Pelov,
   Antoni Markovski for their help on COMI/CoOL and Yang.





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7.  Normative References

   [I-D.toutain-6lpwa-ipv6-static-context-hc]
              Minaburo, A. and L. Toutain, "6LPWA Static Context Header
              Compression (SCHC) for IPV6 and UDP", draft-toutain-6lpwa-
              ipv6-static-context-hc-00 (work in progress), June 2016.

   [I-D.veillette-core-cool]
              Veillette, M., Pelov, A., Somaraju, A., Turner, R., and A.
              Minaburo, "Constrained Objects Language", draft-veillette-
              core-cool-01 (work in progress), March 2016.

Appendix A.  Yang Model



 module LPWA-compression {

        namespace "http://ackl.io/compression";


        prefix "lpwa";

        import ietf-inet-types {
                        prefix inet;
        }

        description
                "Data model to compress headers on 6LPWA";

        revision 2016-06-01 {
                description "This module describes the context store in End-System (LC) and LPWA Compressor (LC). ";
        }

        typedef LPWA-types {
                type union {
                        type uint8;
                        type uint16;
                        type uint32;
                        type uint64;
                        type inet:ipv6-prefix; // better use int64, more comptact ?
                        type string;
                }
        }

        typedef LPWA-action-functions {
                type enumeration {
         enum elided;



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         enum send-value;
         enum compute-IPv6-length;
         enum compute-UDP-length;
         enum compute-UDP-checksum;
         enum ESiid-DID;
         enum LAiid-DID;
                }
        }

        grouping matching-operator {
                leaf operator {
                        type enumeration {
                        enum operator-equal;
                        enum operator-lsb;
                        enum operator-ignore;
                        }
                }
                choice operator-lsb {
                        leaf lsb-length {
                                type LPWA-types;
                        }
                }

        }

        grouping field-context {
                leaf field-name {
                        type string;
                }
                leaf field-pos {
                        type int8;
                }
                leaf field-value {
                        type LPWA-types;
                }
                container field-compression-match {
                        uses matching-operator;
                }
                container field-decompression-match {
                        uses matching-operator;
                }
                leaf action-function {
                        type LPWA-action-functions;
                }
        }

        container generic-rules {
                leaf context-name {



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                        type string;
                }
                list context-rules {
                    key rule-id;

                        leaf rule-name {
                                type string;
                        }
                        leaf rule-id {
                                type int8;
                        }
                        list rule-fields {
                            key field-pos;
                                uses field-context;
                        }
                }

        }

        container IPv6-UDP-rules {
                leaf context-name {
                        type string;
                }
                list context-rules {
                    key rule-id;

                        leaf rule-name {
                                type string;
                        }
                        leaf rule-id {
                                type int8;
                        }
                        container shim-id {
                                uses field-context {
                                        refine field-name {
                                                default "shim identifier";
                                        }
                                        refine field-pos {
                                                default 0;
                                        }
                                        refine field-value {
                                                default 0;
                                        }
                                }
                        }
                        container ES-device-id {
                                uses field-context {
                                        refine field-name {



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                                                default "End System device identifier";
                                        }
                                        refine field-pos {
                                                default 1;
                                        }
                                        refine field-value {
                                                default 0;
                                        }
                                }
                        }
                        container ipv6-version {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 Version";
                                        }
                                        refine field-pos {
                                                default 2;
                                        }
                                        refine field-value {
                                                default 6;
                                        }
                                }
                        }
                        container ipv6-diffserv {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 Diffserv";
                                        }
                                        refine field-pos {
                                                default 3;
                                        }
                                        refine field-value {
                                                default 0;
                                        }
                                }
                        }
                        container ipv6-flow-label {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 Flow Label";
                                        }
                                        refine field-pos {
                                                default 4;
                                        }
                                        refine field-value {
                                                default 0;
                                        }
                                }



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                        }
                        container ipv6-length {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 length";
                                        }
                                        refine field-pos {
                                                default 5;
                                        }
                                }
                        }
                        container ipv6-next-header {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 next header";
                                        }
                                        refine field-pos {
                                                default 6;
                                        }
                                        refine field-value {
                                                default 17;
                                        }
                                }
                        }
                        container ipv6-hop-limit {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 Hop Limit";
                                        }
                                        refine field-pos {
                                                default 7;
                                        }
                                        refine field-value {
                                                default 17;
                                        }
                                }
                        }
                        container ipv6-ES-prefix {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 ES Prefix";
                                        }
                                        refine field-pos {
                                                default 8;
                                        }
                                }
                        }
                        container ipv6-ES-iid {



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                                uses field-context {
                                        refine field-name {
                                                default "IPv6 ES Interface ID";
                                        }
                                        refine field-pos {
                                                default 9;
                                        }
                                }
                        }
                        container ipv6-LC-prefix {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 LC Prefix";
                                        }
                                        refine field-pos {
                                                default 10;
                                        }
                                }
                        }
                        container ipv6-LC-iid {
                                uses field-context {
                                        refine field-name {
                                                default "IPv6 LC Interface ID";
                                        }
                                        refine field-pos {
                                                default 11;
                                        }
                                }
                        }

                        container udp-ES-port {
                                uses field-context {
                                        refine field-name {
                                                default "UDP ES port";
                                        }
                                        refine field-pos {
                                                default 12;
                                        }
                                }
                        }
                        container udp-LC-port {
                                uses field-context {
                                        refine field-name {
                                                default "UDP LC port";
                                        }
                                        refine field-pos {
                                                default 13;
                                        }



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                                }
                        }

                }

        }
}

          Figure 10: Yang definition of the IPv6 UDP compression

Authors' Addresses

   Ana Minaburo
   Acklio
   2bis rue de la Chataigneraie
   35510 Cesson-Sevigne Cedex
   France

   Email: ana@ackl.io


   Laurent Toutain
   Institut MINES TELECOM ; TELECOM Bretagne
   2 rue de la Chataigneraie
   CS 17607
   35576 Cesson-Sevigne Cedex
   France

   Email: Laurent.Toutain@telecom-bretagne.eu






















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