Internet DRAFT - draft-toutain-lpwan-schc-yang-data-model
draft-toutain-lpwan-schc-yang-data-model
Network Working Group A. Minaburo
Internet-Draft Acklio
Intended status: Informational L. Toutain
Expires: September 12, 2019 Institut MINES TELECOM ; IMT Atlantique
March 11, 2019
Data Model for Static Context Header Compression (SCHC)
draft-toutain-lpwan-schc-yang-data-model-00
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 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.
Status of This Memo
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This Internet-Draft will expire on September 12, 2019.
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
SCHC [I-D.ietf-lpwan-ipv6-static-context-hc] defines a compression
technique for LPWAN networks based on static context. The context
contains a list of 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
The goal of this document is to provide an YANG data model to
represent SCHC Compression and Fragmentation rules, to allow
management over a LPWAN network. The main constraints are:
o since the device may be managed through the LPWAN network,
management messages must be compact. COREconf offers a
representation based on CBOR.
o this data model can be extended with new values, such as new field
id, new MO or CDA.
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2. YANG types
2.1. Field Identifier
The field identifier is used to identify a specific field. It is
viewed as an uint32.
2.2. Target Value field
A value may be associated for each field in a rule. The value's type
depends on 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.
typedef lpwan-types {
type union {
type uint8;
type uint16;
type uint32;
type uint64;
type inet:ipv6-prefix;
type string;
}
}
Figure 2: Value types
Note that as defined in [I-D.ietf-lpwan-ipv6-static-context-hc], Dev
and App Prefixes can be of type inet:ipv6-prefix-type, but this type
derives from ASCII characters, a binary representation such as uint64
will 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 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 in the compressed header or the uncompressed header.
The SCHC document [I-D.ietf-lpwan-ipv6-static-context-hc] defines
four operators:
o equal: The rule's value must be equal to the packet header value
for a specific field.
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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 of least
significant bit part, which will be ignored during the matching
but sent if the rule matches.
o match-mapping: From the list of values of the Target Value, This
operator will match if one of those values is equal to the field
value and will send the index of the list representing this value.
/**********************************/
/* Matching operator type */
/**********************************/
typedef matching-operator-type {
type enumeration {
enum equal;
enum ignore;
enum msb;
enum match-mapping;
}
}
Figure 3: Matching operators
Figure 3 represents the Matching Operator type definition.
2.4. Compression Decompression Actions
The SCHC document [I-D.ietf-lpwan-ipv6-static-context-hc] defines
some compression decompression actions (CDA). The CDA tells how to
compress and decompress the field. They are defined in Figure 4.
they are coded the same way as MO.
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/***********************************************/
/* Compression-Decompression action type */
/***********************************************/
typedef compression-decompression-action-type {
type enumeration {
enum not-sent;
enum value-sent;
enum lsb;
enum mapping-sent;
enum compute-length;
enum compute-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 key which will be used 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 of instances,
o a field direction indicates the packet direction,
o a field target value containing the value that will be compared,
o a matching operators for rule selection
o an compression/decompression action to compress/decompress the
field.
Figure 5 defines the format.
grouping rule-entry {
leaf field-id {
type int32;
description "Field ID unique value representing the Field";
}
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leaf field-length {
type uint8;
description "size in bits of the field";
}
leaf field-position {
type uint8;
description "For repeated fields, we need to be able to
distinguish between successive occurences";
}
leaf direction {
type direction-type;
}
list target-values {
key tv-key;
leaf tv-key {
type int8;
}
leaf target-value {
type lpwan-types;
}
description "Target Values can be a list of value, for
match-mapping. For other MO, only one entry is specified";
}
leaf matching-operator {
type matching-operator-type;
}
leaf matching-operator-parameter {
type lpwan-types;
description "If the matching operator requires a parameter
(for example lsb or msb), the value is provided here.";
}
leaf compression-decompression-action {
type compression-decompression-action-type;
}
leaf compression-decompression-action-parameter {
type lpwan-types;
description "If the matching operator requires a parameter
(for example lsb or msb), the value is provided here.";
}
}
Figure 5: Action functions
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4. YANG static context model
This lead to the generic rule definition, represented Figure 7. It
defines a set of rules.
grouping compression-rule {
leaf rule-id {
type uint8;
description "The number of the context rule that should be applied.";
}
leaf rule-id-length {
type uint8;
}
list rule-fields {
key "field-id field-position direction";
uses rule-entry;
}
}
Figure 6: YANG definition of the generic module
module: ietf-lpwan-schc-rule
+--rw rule-id? uint8
+--rw rule-id-length? uint8
+--rw rule-fields* [field-id field-position direction]
+--rw field-id int32
+--rw field-length? uint8
+--rw field-position uint8
+--rw direction direction-type
+--rw target-values* [tv-key]
| +--rw tv-key int8
| +--rw target-value? lpwan-types
+--rw matching-operator? m.-o.-type
+--rw matching-operator-parameter? lpwan-types
+--rw compression-decompression-action? c.-d.-a.-type
+--rw compression-decompression-action-parameter? lpwan-types
Figure 7: Generic module tree
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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
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 to 1012
are used in /generic-rules/context-rules/rule-fields/field-matching-
operator.
5. Acknowledgement
The authors would like to thank Michel Veillette, Alexander Pelov,
Antoni Markovski for their help on COMI/CoOL and YANG.
6. Normative References
[I-D.ietf-core-comi]
Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP
Management Interface", draft-ietf-core-comi-04 (work in
progress), November 2018.
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[I-D.ietf-lpwan-ipv6-static-context-hc]
Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and J.
Zuniga, "LPWAN Static Context Header Compression (SCHC)
and fragmentation for IPv6 and UDP", draft-ietf-lpwan-
ipv6-static-context-hc-18 (work in progress), December
2018.
Authors' Addresses
Ana Minaburo
Acklio
1137A Avenue des Champs Blancs
35510 Cesson-Sevigne Cedex
France
Email: ana@ackl.io
Laurent Toutain
Institut MINES TELECOM ; IMT Atlantique
2 rue de la Chataigneraie
CS 17607
35576 Cesson-Sevigne Cedex
France
Email: Laurent.Toutain@imt-atlantique.fr
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