Network
lpwan Working Group                                          A. Minaburo
Internet-Draft                                                    Acklio
Intended status: Informational Standards Track                              L. Toutain
Expires: October 23, 2019 July 26, 2020            Institut MINES TELECOM ; TELECOM; IMT Atlantique
                                                          April 21, 2019
                                                        January 23, 2020

        Data Model for Static Context Header Compression (SCHC)
                draft-ietf-lpwan-schc-yang-data-model-00
                draft-ietf-lpwan-schc-yang-data-model-01

Abstract

   This document describes a YANG data model for the SCHC (Static
   Context Header Compression).  A generic module is defined, that can
   be applied for any headers Compression) compression and also a specific model for the IPv6 UDP
   protocol stack is also proposed.  Note that this draft is a first
   attempt to define a YANG data module for SCHC, more work is needed to
   use all the YANG facilities. fragmentation rules.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on October 23, 2019. July 26, 2020.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  SCHC [I-D.ietf-lpwan-ipv6-static-context-hc] defines rules  . . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Compression Rules . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Field Identifier  . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Field length  . . . . . . . . . . . . . . . . . . . . . .   6
     2.4.  Field position  . . . . . . . . . . . . . . . . . . . . .   7
     2.5.  Direction Indicator . . . . . . . . . . . . . . . . . . .   7
     2.6.  Target Value  . . . . . . . . . . . . . . . . . . . . . .   8
     2.7.  Matching Operator . . . . . . . . . . . . . . . . . . . .   9
       2.7.1.  Matching Operator arguments . . . . . . . . . . . . .  10
     2.8.  Compression Decompresison Actions . . . . . . . . . . . .  10
       2.8.1.  Compression Decompression Action arguments  . . . . .  12
   3.  Rule definition . . . . . . . . . . . . . . . . . . . . . . .  12
     3.1.  Compression rule  . . . . . . . . . . . . . . . . . . . .  14
       3.1.1.  Compression context representation. . . . . . . . . .  14
       3.1.2.  Rule definition . . . . . . . . . . . . . . . . . . .  16
     3.2.  Fragmentation rule  . . . . . . . . . . . . . . . . . . .  16
     3.3.  YANG Tree . . . . . . . . . . . . . . . . . . . . . . . .  17
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   5.  Security considerations . . . . . . . . . . . . . . . . . . .  17
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  18
   7.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .  18
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

2.  SCHC rules

   SCHC is a compression
   technique and fragmentation mechanism for LPWAN constrained
   networks defined in [I-D.ietf-lpwan-ipv6-static-context-hc] it is
   based on a static context.  The context
   contains a list shared by two entities at the boundary this
   contrained network.  Draft [I-D.ietf-lpwan-ipv6-static-context-hc]
   provides an abstract representation of the rules (cf.  Figure 1).  Each rule contains itself
   a list of field descriptions composed of a field identifier (FID), a
   field length (FID), a field position (FP), a field direction (DI), a
   target value (TV), a matching operator (MO) and a Compression/
   Decompression Action (CDA).

     +-----------------------------------------------------------------+
     |                      Rule N                                     |
    +-----------------------------------------------------------------+|
    |                    Rule i                                       ||
   +-----------------------------------------------------------------+||
   |  (FID)            Rule 1                                        |||
   |+-------+--+--+--+------------+-----------------+---------------+|||
   ||Field 1|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act||||
   |+-------+--+--+--+------------+-----------------+---------------+|||
   ||Field 2|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act||||
   |+-------+--+--+--+------------+-----------------+---------------+|||
   ||...    |..|..|..|   ...      | ...             | ...           ||||
   |+-------+--+--+--+------------+-----------------+---------------+||/
   ||Field N|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act|||
   |+-------+--+--+--+------------+-----------------+---------------+|/
   |                                                                 |
   \-----------------------------------------------------------------/

                Figure 1: Compression Decompression Context used either for
   compression/decompression (or C/D) or fragmentation/reassembly (or F/
   R).  The goal of this document is to provide an YANG data model formalize the description of the
   rules to
   represent SCHC Compression and Fragmentation rules, offer:

   o  universal representation of the rule to allow
   management over a LPWAN network.  The main constraints are:

   o  since the same rule
      represention on both ends.  For instance; a device may be managed through can provide the LPWAN network,
      management messages must be compact.  COREconf offers a
      representation based on CBOR.
      rule it uses to store them in the core SCHC C/D and F/R.

   o  this data model  a device or the core SCHC instance may update the other end to set
      upsome specific values (e.g.  IPv6 prefix, Destination
      address,...)

   o  ...

   This document defines a YANG module to represent both compression and
   fragmentation rules, which leads to common representation and values
   for the elements of the rules.  SCHC compression is generic, the main
   mechanism do no refers to a specific fields.  A field is abstractedh
   through an ID, a position, a direction and a value that can be extended with new values, such as new field
      id, new MO a
   numerical value or CDA.

2.  YANG types a string.

   [I-D.ietf-lpwan-ipv6-static-context-hc] and
   [I-D.ietf-lpwan-coap-static-context-hc] specifies fields for IPv6,
   UDP, CoAP and OSCORE.

   Fragmentation requires a set of common parameters that are included
   in a rule.

2.1.  Compression Rules

   [I-D.ietf-lpwan-ipv6-static-context-hc] proposes an abstract
   representation of the compression rule.  A compression context for a
   device is composed of a set of rules.  Each rule contains information
   to describe a specific field in the header to be compressed.

     +-----------------------------------------------------------------+
     |                      Rule N                                     |
    +-----------------------------------------------------------------+|
    |                    Rule i                                       ||
   +-----------------------------------------------------------------+||
   |  (FID)            Rule 1                                        |||
   |+-------+--+--+--+------------+-----------------+---------------+|||
   ||Field 1|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act||||
   |+-------+--+--+--+------------+-----------------+---------------+|||
   ||Field 2|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act||||
   |+-------+--+--+--+------------+-----------------+---------------+|||
   ||...    |..|..|..|   ...      | ...             | ...           ||||
   |+-------+--+--+--+------------+-----------------+---------------+||/
   ||Field N|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act|||
   |+-------+--+--+--+------------+-----------------+---------------+|/
   |                                                                 |
   \-----------------------------------------------------------------/

                Figure 1: Compression Decompression Context

2.2.  Field Identifier

   In the process of compression, the headers of the original packet are
   first parsed to create a list of fields.  This list of fields is
   matched again the rules to find the appropriate one and apply
   compression.  The link between the list given by the parsed fields
   and the rules is doen through a field ID.
   [I-D.ietf-lpwan-ipv6-static-context-hc] do not state how the field ID
   value can be constructed.  In the given example, it was given through
   a string indexed by the protocol name (e.g.  IPv6.version,
   CoAP.version,...).

   Using the YANG model, each field can be identified through a global
   YANG identityref.  A YANG field ID derives from the field-id-base-
   type.  Figure 2 gives some field ID definitions.  Note that some
   field IDs can be splitted is smaller pieces.  This is the case for
   "fid-ipv6-trafficclass-ds" and "fid-ipv6-trafficclass-ecn" which are
   a subset of "fid-ipv6-trafficclass-ds".

     identity field-id-base-type  {
              description "Field ID with SID";
     }

     identity fid-ipv6-version {
              base field-id-base-type;
              description "IPv6 version field from RFC8200";
     }

     identity fid-ipv6-trafficclass {
              base field-id-base-type;
              description "IPv6 Traffic Class field from RFC8200";
     }

     identity fid-ipv6-trafficclass-ds {
             base field-id-base-type;
               description "IPv6 Traffic Class field from RFC8200,
                             DiffServ field from RFC3168";
     }

     identity fid-ipv6-trafficclass-ecn {
             base field-id-base-type;
               description "IPv6 Traffic Class field from RFC8200,
                      ECN field from RFC3168";
     }

     ...

     identity fid-coap-option-if-match {
             base field-id-base-type;
               description "CoAP option If-Match from RFC 7252";
     }

     identity fid-coap-option-uri-host {
             base field-id-base-type;
               description "CoAP option URI-Host from RFC 7252";
     }

     ...

            Figure 2: Definition of indentityref for field IDs

   Figure 2 gives an example of field ID identityref definitions.  The
   base identity is field-id-base-type, and field id are derived for it.
   The naming convention is "fid" followed by the protocol name and the
   field name.

   The yang model in annex gives the full definition of the field ID for
   [I-D.ietf-lpwan-ipv6-static-context-hc] and
   [I-D.ietf-lpwan-coap-static-context-hc].

The type associated to this identity is field-id-type (cf. {{Fig-field-id-type}})

    typedef field-id-type {
        description "Field ID generic type.";
        type identityref {
            base field-id-base-type;
        }
    }

            Figure 3: Definition of indentityref for field IDs

2.3.  Field length

   Field length is either an integer giving the size of a field in bits
   or a function.  [I-D.ietf-lpwan-ipv6-static-context-hc] defines the
   "var" function which allows variable length fields in byte and
   [I-D.ietf-lpwan-coap-static-context-hc] defines the "tkl" function
   for managing the CoAP Token length field.

     identity field-length-base-type {
           description "used to extend field length functions";
     }

     identity fl-variable {
              base field-length-base-type;
              description "residue length in Byte is sent";
     }

     identity fl-token-length {
              base field-length-base-type;
              description "residue length in Byte is sent";
     }

             Figure 4: Definition of indetntyref for field IDs

   As for field ID, field length function can be defined as a
   identityref as shown in Figure 4.

   Therefore the type for field length is a union between an integer
   giving in bits the size of the length and the identityref (cf.
   Figure 5).

       typedef field-length-type {
           type union {
               type int64; /* positive length */
               type identityref { /* function */
                   base field-length-base-type;
               }
           }
       }

             Figure 5: Definition of indetntyref for field IDs

   The naming convention is fl followed by the function name as defined
   in SCHC specifications.

2.4.  Field position

   Field position is a positive integer which gives the position of a
   field, the default value is 1, but if the field is repeated several
   times, the value is higher.  value 0 indicates that the position is
   not important and is not taken into account during the rule selection
   process.

   Field position is a positive integer.  The type is an uint8.

2.5.  Direction Indicator

   The field identifier Direction Indicator (DI) is used to identify tell if a specific field.  It is
   viewed as an uint32.

2.2.  Target Value field

   A value may be associated for each field appears in a rule.  The value's type
   depends on the field.  It can be an integer, a prefix, a string,
   both direction (Bi) or
   any other type carried by only uplink (Up) or Downlink (Dw).

     identity direction-indicator-base-type {
           description "used to extend field length functions";
     }

     identity di-bidirectional {
              base direction-indicator-base-type;
              description "Direction Indication of bi directionality";
     }

     identity di-up {
              base direction-indicator-base-type;
              description "Direction Indication of upstream";
     }

     identity di-down {
              base direction-indicator-base-type;
              description "Direction Indication of downstream";
     }

       Figure 6: Definition of identityref for direction indicators

   Figure 6 gives the field. identityref for Direction Indicators.

   The LPWA-types regroups all the
   possibles values. type is "direction-indicator-type" (cf.  Figure 2 gives its definition. 7).

       typedef lpwan-types direction-indicator-type {
           type union identityref {
           type uint8;
           type uint16;
           type uint32;
           type uint64;
           type inet:ipv6-prefix;
           type string;
               base direction-indicator-base-type;
           }
       }

       Figure 2: 7: Definition of identityref for direction indicators

2.6.  Target Value types

   Note that as defined in [I-D.ietf-lpwan-ipv6-static-context-hc], Dev
   and App Prefixes can

   Target Value may be of type inet:ipv6-prefix-type, but this type
   derives from ASCII characters, either a string or binary representation such as uint64
   will sequence.  For match-
   mapping, several of these values can be more compact.

2.3.  Matching Operators

   A matching operator is used to check the field value stored in the
   rule against the value contained in the header a Target Value
   field.  If there is no
   matching  In the rule data model, this is not selected.  Two instances of matching
   operator are defined to allow the rule selection from informations
   contained either in generalized by adding a position,
   which orders the compressed header or list of values.  By default the uncompressed header.
   The SCHC document [I-D.ietf-lpwan-ipv6-static-context-hc] defines
   four operators:

   o  equal: position is set to
   0.

   The rule's value must be equal leaf "value" is not mandatory to the packet header represent a non existing value
      for
   in a specific field.

   o  ignore: There is no check for this field.

   o  MSB(x): This operator compare the most significant bits.  The
      operator takes one argument representing the length TV.

     grouping target-values-struct {
       leaf value {
         type union {
           type binary;
           type string;
         }
       }
       leaf position {
             type uint16;
       }
     }

                   Figure 8: Definition of least
      significant bit part, which will be ignored during the matching
      but sent if the rule matches.

   o  match-mapping: From target value

   Figure 8 gives the list definition of values a single element of the a Target Value, This
      operator Value.
   In the rule, this will match if one of those values be used as a list, with position as a key.

2.7.  Matching Operator

   Matching Operator (MO) is equal to the a function applied between a field value and will send
   provided by the index of parsed header and the list representing this target value.

       /**********************************/
       /*
   [I-D.ietf-lpwan-ipv6-static-context-hc] defines 4 MO.

     identity matching-operator-base-type {
        description "used to extend Matching Operators with SID values";
     }

     identity mo-equal {
        base matching-operator-base-type;
        description "SCHC draft";
     }

     identity mo-ignore {
        base matching-operator-base-type;
        description "SCHC draft";
     }

     identity mo-msb {
        base matching-operator-base-type;
        description "SCHC draft";
     }

     identity mo-matching {
        base matching-operator-base-type;
        description "SCHC draft";
     }

            Figure 9: Definition of Matching operator Operator identity

   the type         */
       /**********************************/ is "matching-operator-type" (cf.  Figure 10)

      typedef matching-operator-type {
           type enumeration identityref {
               enum equal;
               enum ignore;
               enum msb;
               enum match-mapping;
               base matching-operator-base-type;
           }
       }

              Figure 3: Matching operators

   Figure 3 represents the 10: Definition of Matching Operator type definition.

2.4.  Compression Decompression Actions

   The SCHC document [I-D.ietf-lpwan-ipv6-static-context-hc] defines

2.7.1.  Matching Operator arguments

   Some Matching Operator such as MSB can take some compression decompression actions (CDA).  The CDA tells how to
   compress and decompress values.  Even if
   currently LSB is the field.  They are defined only MO takes only one argument, in Figure 4.
   they are coded the same way future
   some MO may require several arguments.  They are viewed as MO.

           /***********************************************/
           /* Compression-Decompression action a list of
   target-values-type.

2.8.  Compression Decompresison Actions

   Compresion Decompression Action (CDA) idenfied the function to use
   either for compression or decompression.
   [I-D.ietf-lpwan-ipv6-static-context-hc] defines 6 CDA.

       identity compression-decompression-action-base-type;

       identity cda-not-sent {
           base compression-decompression-action-base-type;
              description "from SCHC draft";
       }

       identity cda-value-sent {
           base compression-decompression-action-base-type;
              description "from SCHC draft";
       }

       identity cda-lsb {
           base compression-decompression-action-base-type;
              description "from SCHC draft";
       }

       identity cda-mapping-sent {
           base compression-decompression-action-base-type;
              description "from SCHC draft";
       }

       identity cda-compute-length {
           base compression-decompression-action-base-type;
              description "from SCHC draft";
       }

       identity cda-compute-checksum {
           base compression-decompression-action-base-type;
              description "from SCHC draft";
       }

       identity cda-deviid {
           base compression-decompression-action-base-type;
              description "from SCHC draft";
       }

      identity cda-appiid {
           base compression-decompression-action-base-type;
              description "from SCHC draft";
       }

     Figure 11: Definition of Compresion Decompression Action identity

   The type       */
           /***********************************************/ is "comp-decomp-action-type" (cf.  Figure 12)
      typedef compression-decompression-action-type comp-decomp-action-type {
           type enumeration identityref {
                                   enum not-sent;
                                   enum value-sent;
                                   enum lsb;
                                   enum mapping-sent;
                                   enum compute-length;
                                   enum compute-checksum;
                                   enum esiid-did;
                                   enum laiid-did;
               base compression-decompression-action-base-type;
           }
       }

       Figure 4: 12: Definition of Compresion Decompression Action functions

3.  Generic rule definition

   Each rule's row is defined by type

2.8.1.  Compression Decompression Action arguments

   Currently no CDA requires argumetns, but the future some CDA may
   require several leaves, composed of:

   o  a field key which will be used arguments.  They are viewed as a key,

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

   o  a field length that containing the length of the field,

   o  a field position that gives the number a list of instances,

   o target-
   values-type.

3.  Rule definition

   A rule is either a field direction indicates C/D or an F/R rule.  A rule is identified by the packet direction,

   o  a field target
   rule ID value containing and its associated length.  The YANG grouping rule-id-
   type defines the value that will be compared,

   o structure used to represent a matching operators for rule selection

   o  an compression/decompression action ID.  Length of 0
   is allowed to compress/decompress the
      field.

   Figure 5 defines the format. represent an implicit rule.

// Define rule ID. Rule ID is composed of a RuleID value and a Rule ID Length

  grouping rule-entry rule-id-type {
      leaf field-id rule-id {
        type int32; uint32;
        description "Field "rule ID unique value, this value representing must be unique combined with the Field"; length";
      }
      leaf field-length rule-length {
        type uint8; uint8 {
          range 0..32;
        }
                  description "size "rule ID length in bits of the field"; bits, value 0 is for implicit rules";
      }

                leaf field-position {
                        type uint8;
                        description "For repeated fields, we need to be able to
                                     distinguish between successive occurences";
  }

                leaf direction

// SCHC table for a specific device.

  container schc {
    leaf version{
        type direction-type; uint64;
        mandatory false;
        description "used as an indication for versioning";
    }
    list target-values rule {
        key tv-key;
                     leaf tv-key "rule-id rule-length";
                uses rule-id-type;
                  choice nature {
                        type int8;
                          case fragmentation {
                uses fragmentation-content;
              }
                     leaf target-value
                case compression {
                        type lpwan-types;
                uses compression-content;
         }
                     description "Target Values
       }
         }
   }

                  Figure 13: Definition of a SCHC Context

   To access to a specfic rule, rule-id and its specific length is used
   as a key.  The rule is either a compression or a fragmentation rule.

   Each context can be identify though a list version id.

3.1.  Compression rule

   A compression rule is composed of value, for
                                  match-mapping. For other MO, only one entries describing its processing
   (cf.  Figure 14).  An entry contains all the information defined in
   Figure 1 with the types defined above.

3.1.1.  Compression context representation.

   The compression rule described Figure 1 is associated to a rule ID.
   The compression rule entry is specified"; defined in Figure 14.  Each column in
   the table is either represented by a leaf or a list.  Note that
   Matching Operators and Compression Decompression actions can have
   arguments.  They are viewed a ordered list of strings and numbers as
   in target values.

  grouping compression-rule-entry {
      leaf field-id {
          mandatory true;
          type schc-id:field-id-type;
      }
      leaf field-length {
          mandatory true;
          type schc-id:field-length-type;
      }
      leaf field-position {
          mandatory true;
          type uint8;
      }
      leaf matching-operator direction-indicator {
          mandatory true;
          type matching-operator-type; schc-id:direction-indicator-type;
      }
      list target-values {
          key position;

                    uses target-values-struct;
      }
      leaf matching-operator-parameter mo {
          mandatory true;
          type lpwan-types;
                     description "If the matching operator requires schc-id:matching-operator-type;
      }
      // /!\ Not always good, it allows to give several arguments to a parameter
                                  (for example lsb MO, but
      // theses arguments are only int or msb), the value is provided here."; strings, cannot be arrays. Is it necessary?
      list mo-value {
          key position;
          uses target-values-struct;
      }
      leaf compression-decompression-action cda {
          mandatory true;
          type compression-decompression-action-type; schc-id:cda-type;
      }

                leaf compression-decompression-action-parameter
      list cda-value {
                     type lpwan-types;
                     description "If the matching operator requires
          key position;
                    uses target-values-struct;
      }
  }

               Figure 14: Definition of a parameter
                                  (for example lsb or msb), the value compression entry

3.1.2.  Rule definition

   A compression rule is provided here."; a list of entries.

  grouping compression-content {
    list entry {
        key "field-id field-position direction-indicator"; // field-position direction-indicator";
              uses compression-rule-entry;
    }
  }

                Figure 5: Action functions

4.  YANG static context model

   This lead to the generic 15: Definition of a compression rule definition, represented Figure 7.  It
   defines

   To identify a set of rules. specific entry Field ID, position and direction is
   needed.

3.2.  Fragmentation rule

   TBD

     grouping compression-rule fragmentation-content {
          leaf rule-id dtagsize {
             type uint8;
            description "The number of the context rule that should be applied.";
          }
          leaf rule-id-length wsize {
             type uint8;
          }

    list rule-fields
          leaf fcnsize {
      key "field-id field-position direction";
      uses rule-entry;
             type uint8;
          }
          choice mode {
             case no-ack;
                       case ack-always;
                   case ack-on-error {
                           leaf ack-method {
                                   type enumeration {
                                           enum afterAll0;
                                           enum afterAll1;
                                           enum always;
                                   }
                           }
                  }
          }
     }

               Figure 6: YANG definition 16: Definition of the generic module a fragmentation rule

3.3.  YANG Tree

module: ietf-lpwan-schc-rule schc
  +--rw schc
     +--rw version?   uint64
     +--rw rule-id? rule* [rule-id rule-length]
        +--rw rule-id                   uint32
        +--rw rule-length               uint8
        +--rw (nature)?
           +--:(fragmentation)
           |  +--rw dtagsize?           uint8
           |  +--rw wsize?              uint8
           |  +--rw rule-id-length? fcnsize?            uint8
           |  +--rw (mode)?
           |     +--:(no-ack)
           |     +--:(ack-always)
           |     +--:(ack-on-error)
           |        +--rw ack-method?   enumeration
           +--:(compression)
              +--rw rule-fields* entry* [field-id field-position direction] direction-indicator]
                 +--rw field-id                                      int32               schc-id:field-id-type
                 +--rw field-length?                                 uint8 field-length           schc-id:field-length-type
                 +--rw field-position         uint8
                 +--rw direction                                     direction-type direction-indicator    schc-id:direction-indicator-type
                 +--rw target-values* [tv-key] [position]
                 |  +--rw tv-key          int8 value?      union
                 |  +--rw target-value?   lpwan-types position    uint16
                 +--rw matching-operator?                            m.-o.-type mo                     schc-id:matching-operator-type
                 +--rw matching-operator-parameter?                  lpwan-types mo-value* [position]
                 |  +--rw compression-decompression-action?             c.-d.-a.-type value?      union
                 |  +--rw compression-decompression-action-parameter?   lpwan-types

                       Figure 7: Generic module tree

   The YANG tree is given Figure 7.

 SID        Assigned to
 ---------  --------------------------------------------------
 60000      node /rule-fields
 60001      node /rule-fields/compression-decompression-action
 60002      node /rule-fields/compression-decompression-action-parameter
 60003      node /rule-fields/direction
 60004      node /rule-fields/field-id
 60005      node /rule-fields/field-length
 60006      node /rule-fields/field-position
 60007      node /rule-fields/matching-operator
 60008      node /rule-fields/matching-operator-parameter
 60009      node /rule-fields/target-values
 60010      node /rule-fields/target-values/target-value
 60011      node /rule-fields/target-values/tv-key
 60012      node /rule-id
 60013      node /rule-id-length

 File ietf-lpwan-schc-rule@2016-10-31.sid created
 Number of SIDs available : 100
 Number of SIDs assigned : 14

                    Figure 8: Example of SID allocation position    uint16
                 +--rw cda                    schc-id:comp-decomp-action-type
                 +--rw cda-value* [position]
                    +--rw value?      union
                    +--rw position    uint16

                                 Figure 8 gives a simple allocation for SID value.  SID values from
   100 to 113 are used for /generic-rules/context-rules/rule-fields/
   field-compression-decompression-action.  SID value from 1009 17

4.  IANA Considerations

   This document has no request to 1012
   are used in /generic-rules/context-rules/rule-fields/field-matching-
   operator. IANA.

5.  Acknowledgement  Security considerations

   This document does not have any more Security consideration than the
   ones already raised on [I-D.ietf-lpwan-ipv6-static-context-hc]

6.  Acknowledgements

   The authors would like to thank Michel Veillette, Dominique Barthel, Carsten Bormann,
   Alexander Pelov,
   Antoni Markovski for their help on COMI/CoOL and YANG.

6. Pelov.

7.  YANG Module

8.  Normative References

   [I-D.ietf-core-comi]
              Veillette, M., Stok, P., Pelov,

   [I-D.ietf-lpwan-coap-static-context-hc]
              Minaburo, A., Toutain, L., and A. Bierman, "CoAP
              Management Interface", draft-ietf-core-comi-04 R. Andreasen, "LPWAN Static
              Context Header Compression (SCHC) for CoAP", draft-ietf-
              lpwan-coap-static-context-hc-12 (work in progress), November 2018.
              December 2019.

   [I-D.ietf-lpwan-ipv6-static-context-hc]
              Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and J.
              Zuniga, "LPWAN Static "Static Context Header Compression (SCHC) and
              fragmentation for IPv6 and UDP", draft-ietf-lpwan-
              ipv6-static-context-hc-18 LPWAN, application to UDP/IPv6", draft-
              ietf-lpwan-ipv6-static-context-hc-24 (work in progress),
              December
              2018. 2019.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,
              <https://www.rfc-editor.org/info/rfc7252>.

Authors' Addresses

   Ana Minaburo
   Acklio
   1137A Avenue avenue des Champs Blancs
   35510 Cesson-Sevigne Cedex
   France

   Email: ana@ackl.io

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

   Email: Laurent.Toutain@imt-atlantique.fr