| Internet-Draft | LPWAN SCHC YANG module | February 2021 |
| Minaburo & Toutain | Expires 6 August 2021 | [Page] |
This document describes a YANG data model for the SCHC (Static Context Header Compression) compression and fragmentation rules.¶
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This Internet-Draft will expire on 6 August 2021.¶
Copyright (c) 2021 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 (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.¶
SCHC is a compression and fragmentation mechanism for constrained networks defined in [RFC8724]. It is based on a static context shared by two entities at the boundary this constrained network. Draft [RFC8724] provides an non formal representation of the rules used either for compression/decompression (or C/D) or fragmentation/reassembly (or F/R). The goal of this document is to formalize the description of the rules to offer:¶
This document defines a YANG module to represent both compression and fragmentation rules, which leads to common representation for values for all the rules elements.¶
SCHC compression is generic, the main mechanism do no refers to a specific protocol. Any header field is abstracted through an ID, a position, a direction and a value that can be a numerical value or a string. [RFC8724] and [I-D.ietf-lpwan-coap-static-context-hc] specifies fields for IPv6, UDP, CoAP and OSCORE. [I-D.barthel-lpwan-oam-schc] decribes ICMPv6 header compression.¶
SCHC fragmentation requires a set of common parameters that are included in a rule. These parameters are defined in [RFC8724].¶
[RFC8724] proposes an non formal 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||| |+-------+--+--+--+------------+-----------------+---------------+|/ | | \-----------------------------------------------------------------/
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 against the rules to find the appropriate one and apply compression. The link between the list given by the parsed fields and the rules is done through a field ID. [RFC8724] do not state how the field ID value can be constructed. In examples, identification is done through a string indexed by the protocol name (e.g. IPv6.version, CoAP.version,...).¶
Using the YANG model, each field MUST 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";
}
...
Figure 2 gives some examples 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 (see Section 7) gives the full definition of the field ID for [RFC8724], [I-D.ietf-lpwan-coap-static-context-hc], and [I-D.barthel-lpwan-oam-schc].¶
The type associated to this identity is field-id-type (cf. Figure 3)¶
typedef field-id-type {
description "Field ID generic type.";
type identityref {
base field-id-base-type;
}
}
Field length is either an integer giving the size of a field in bits or a specific function. [RFC8724] 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";
}
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 {
description "Field length either a positive integer giving the size in bits
or a function defined through an identityref.";
type union {
type int64; /* positive length in bits */
type identityref { /* function */
base field-length-base-type;
}
}
}
The naming convention is fl followed by the function name as defined in SCHC specifications.¶
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.¶
The Direction Indicator (DI) is used to tell if a field appears in both direction (Bi) or 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 gives the identityref for Direction Indicators.¶
The type is "direction-indicator-type" (cf. Figure 7).¶
typedef direction-indicator-type {
description "direction in LPWAN network, up when emitted by the device,
down when received by the device, bi when emitted or received by the device.";
type identityref {
base direction-indicator-base-type;
}
}
Target Value may be either a string or binary sequence. For match-mapping, several of these values can be contained in a Target Value field. In the data model, this is generalized by adding a position, which orders the list of values. By default the position is set to 0.¶
The leaf "value" is not mandatory to represent a non existing value in a TV.¶
grouping target-values-struct {
description "defines the target value element. Can be either an arbitrary
binary or ascii element. All target values are considered as a matching lists.
Position is used to order values, by default position 0 is used when containing
a single element.";
leaf value {
type union {
type binary;
type string;
}
}
leaf position {
description "If only one element position is 0, otherwise position is the
matching list.";
type uint16;
}
}
Figure 8 gives the definition of a single element of a Target Value. In the rule, this will be used as a list, with position as a key. The highest position value is used to compute the size of the index sent in residue.¶
Matching Operator (MO) is a function applied between a field value provided by the parsed header and the target value. [RFC8724] 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 "RFC 8724";
}
identity mo-ignore {
base matching-operator-base-type;
description "RFC 8724";
}
identity mo-msb {
base matching-operator-base-type;
description "RFC 8724";
}
identity mo-matching {
base matching-operator-base-type;
description "RFC 8724";
}
the type is "matching-operator-type" (cf. Figure 10)¶
typedef matching-operator-type {
description "Matching Operator (MO) to compare fields values with target values";
type identityref {
base matching-operator-base-type;
}
}
Some Matching Operator such as MSB can take some values. Even if currently LSB is the only MO takes only one argument, in the future some MO may require several arguments. They are viewed as a list of target-values-type.¶
Compression Decompression Action (CDA) identified the function to use either for compression or decompression. [RFC8724] defines 6 CDA.¶
identity compression-decompression-action-base-type;
identity cda-not-sent {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-value-sent {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-lsb {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-mapping-sent {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-compute-length {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-compute-checksum {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-deviid {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-appiid {
base compression-decompression-action-base-type;
description "RFC 8724";
}
The type is "comp-decomp-action-type" (cf. Figure 12)¶
typedef comp-decomp-action-type {
description "Compression Decompression Action to compression or decompress a field.";
type identityref {
base compression-decompression-action-base-type;
}
}
Currently no CDA requires arguments, but the future some CDA may require several arguments. They are viewed as a list of target-values-type.¶
A rule is either a C/D or an F/R rule. A rule is identified by the rule ID value and its associated length. The YANG grouping rule-id-type defines the structure used to represent a rule ID. Length of 0 is allowed to represent an implicit rule.¶
// Define rule ID. Rule ID is composed of a RuleID value and a Rule ID Length
grouping rule-id-type {
leaf rule-id {
type uint32;
description "rule ID value, this value must be unique combined with the length";
}
leaf rule-length {
type uint8 {
range 0..32;
}
description "rule ID length in bits, value 0 is for implicit rules";
}
}
// SCHC table for a specific device.
container schc {
leaf version{
type uint64;
mandatory false;
description "used as an indication for versioning";
}
list rule {
key "rule-id rule-length";
uses rule-id-type;
choice nature {
case fragmentation {
uses fragmentation-content;
}
case compression {
uses compression-content;
}
}
}
}
To access to a specific 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 identified though a version id.¶
A compression rule is composed of entries describing its processing (cf. Figure 14). An entry contains all the information defined in Figure 1 with the types defined above.¶
The compression rule described Figure 1 is associated to a rule ID. The compression rule entry is 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 {
description "These entries defines a compression entry (i.e. a line)
as defined in RFC 8724 and fragmentation parameters.
+-------+--+--+--+------------+-----------------+---------------+
|Field 1|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act|
+-------+--+--+--+------------+-----------------+---------------+
An entry in a compression rule is composed of 7 elements:
- Field ID: The header field to be compressed. The content is a YANG identifer.
- Field Length : either a positive integer of a function defined as a YANG id.
- Field Position: a positive (and possibly equal to 0) integer.
- Direction Indicator: a YANG identifier giving the direction.
- Target value: a value against which the header Field is compared.
- Matching Operator: a YANG id giving the operation, parameters may be
associated to that operator.
- Comp./Decomp. Action: A YANG id giving the compression or decompression
action, parameters may be associated to that action.
";
leaf field-id {
description "Field ID, identify a field in the header with a YANG identityref.";
mandatory true;
type schc:field-id-type;
}
leaf field-length {
description "Field Length in bit or through a function defined as a YANG identityref";
mandatory true;
type schc:field-length-type;
}
leaf field-position {
description "field position in the header is a integer. If the field is not repeated
in the header the value is 1, and incremented for each repetition of the field. Position
0 means that the position is not important and order may change when decompressed";
mandatory true;
type uint8;
}
leaf direction-indicator {
description "Direction Indicator, a YANG identityref to say if the packet is bidirectionnal,
up or down";
mandatory true;
type schc:direction-indicator-type;
}
list target-values {
description "a list of value to compare with the header field value. If target value
is a singleton, position must be 0. For matching-list, should be consecutive position
values starting from 1.";
key position;
uses target-values-struct;
}
leaf matching-operator {
mandatory true;
type schc:matching-operator-type;
}
list matching-operator-value {
key position;
uses target-values-struct;
}
leaf comp-decomp-action {
mandatory true;
type schc:comp-decomp-action-type;
}
list comp-decomp-action-value {
key position;
uses target-values-struct;
}
}
A compression rule is a list of entries.¶
grouping compression-content {
description "define a compression rule composed of a list of entries.";
list entry {
key "field-id field-position direction-indicator";
uses compression-rule-entry;
}
}
To identify a specific entry Field ID, position and direction are needed.¶
Parameters for fragmentation are defined in Annex D of [RFC8724].¶
Figure 16 gives the first elements found in this structure. It starts with a direction. Since fragmentation rules work for a specific direction, they contain a mandatory direction. The type is the same as the one used in compression entries, but the use of bidirectionnal is forbidden.¶
The next elements describe size of SCHC fragmentation header fields. Only the FCN size is mandatory and value must be higher or equal to 1.¶
grouping fragmentation-content {
description "This grouping defines the fragmentation parameters for
all the modes (No Ack, Ack Always and Ack on Error) specified in
RFC 8724.";
leaf direction {
type schc:direction-indicator-type;
description "should be up or down, bi directionnal is forbidden.";
mandatory true;
}
leaf dtagsize {
type uint8;
description "size in bit of the DTag field";
}
leaf wsize {
type uint8;
description "size in bit of the window field";
}
leaf fcnsize {
type uint8 {
range 1..max;
}
description "size in bit of the FCN field";
mandatory true;
}
...
RCS algorithm is defined (Figure 17), by default with the CRC computation proposed in [RFC8724]. The algorithms are identified through an identityref specified in the SCHC Data Model and with the type RCS-algorithm-type (Figure 18).¶
...
leaf RCS-algorithm {
type RCS-algorithm-type;
default schc:RFC8724-RCS;
description "Algoritm used for RCS";
}
...
identity RCS-algorithm-base-type {
description "identify which algorithm is used to compute RSC.
The algorithm defines also the size if the RSC field.";
}
identity RFC8724-RCS {
description "CRC 32 defined as default RCS in RFC8724.";
base RCS-algorithm-base-type;
}
typedef RCS-algorithm-type {
type identityref {
base RCS-algorithm-base-type;
}
}
Figure 19 gives the parameters used by the state machine to handle fragmentation:¶
...
leaf maximum-window-size {
type uint16;
description "by default 2^wsize - 2";
}
leaf retransmission-timer {
type uint64 {
range 1..max;
}
description "duration in seconds of the retransmission timer"; // Check the units
}
leaf inactivity-timer {
type uint64;
description "duration is seconds of the inactivity timer, 0 indicates the timer is disabled"; // check units
}
leaf max-ack-requests {
type uint8 {
range 1..max;
}
description "the maximum number of retries for a specific SCHC ACK.";
}
leaf maximum-packet-size {
type uint16;
default 1280;
description "When decompression is done, packet size must not strictly exceed this limit in Bytes";
}
...
Figure 20 gives information related to a specific compression mode: fragmentation-mode MUST be set with a specific behavior. Identityref are given Figure 21.¶
For Ack on Error some specific information may be provided:¶
...
leaf fragmentation-mode {
type schc:fragmentation-mode-type;
description "which fragmentation mode is used (noAck, AckAlways, AckonError)";
mandatory true;
}
choice mode {
case no-ack;
case ack-always;
case ack-on-error {
leaf tile-size {
type uint8;
description "size in bit of tiles, if not specified or set to 0: tile fills the fragment.";
}
leaf tile-in-All1 {
type schc:all1-data-type;
description "When true, sender and receiver except a tile in All-1 frag";
}
leaf ack-behavior {
type schc:ack-behavior-type;
description "Sender behavior to acknowledge, after All-0, All-1 or when the
LPWAN allows it (Always)";
}
}
}
...
// -- FRAGMENTATION TYPE
// -- fragmentation modes
identity fragmentation-mode-base-type {
description "fragmentation mode";
}
identity fragmentation-mode-no-ack {
description "No Ack of RFC 8724.";
base fragmentation-mode-base-type;
}
identity fragmentation-mode-ack-always {
description "Ack Always of RFC8724.";
base fragmentation-mode-base-type;
}
identity fragmentation-mode-ack-on-error {
description "Ack on Error of RFC8724.";
base fragmentation-mode-base-type;
}
typedef fragmentation-mode-type {
type identityref {
base fragmentation-mode-base-type;
}
}
// -- Ack behavior
identity ack-behavior-base-type {
description "define when to send an Acknowledgment message";
}
identity ack-behavior-after-All0 {
description "fragmentation expects Ack after sending All0 fragment.";
base ack-behavior-base-type;
}
identity ack-behavior-after-All1 {
description "fragmentation expects Ack after sending All1 fragment.";
base ack-behavior-base-type;
}
identity ack-behavior-always {
description "fragmentation expects Ack after sending every fragment.";
base ack-behavior-base-type;
}
typedef ack-behavior-type {
type identityref {
base ack-behavior-base-type;
}
}
// -- All1 with data types
identity all1-data-base-type {
description "type to define when to send an Acknowledgment message";
}
identity all1-data-no {
description "All1 contains no tiles.";
base all1-data-base-type;
}
identity all1-data-yes {
description "All1 MUST contain a tile";
base all1-data-base-type;
}
identity all1-data-sender-choice {
description "Fragmentation process choose to send tiles or not in all1.";
base all1-data-base-type;
}
typedef all1-data-type {
type identityref {
base all1-data-base-type;
}
}
## YANG Tree¶
module: schc
+--rw schc
+--rw version? uint64
+--rw rule* [rule-id rule-length]
+--rw rule-id uint32
+--rw rule-length uint8
+--rw (nature)?
+--:(fragmentation)
| +--rw direction schc:direction-indicator-type
| +--rw dtagsize? uint8
| +--rw wsize? uint8
| +--rw fcnsize uint8
| +--rw RCS-algorithm? RCS-algorithm-type
| +--rw maximum-window-size? uint16
| +--rw retransmission-timer? uint64
| +--rw inactivity-timer? uint64
| +--rw max-ack-requests? uint8
| +--rw maximum-packet-size? uint16
| +--rw fragmentation-mode schc:fragmentation-mode-type
| +--rw (mode)?
| +--:(no-ack)
| +--:(ack-always)
| +--:(ack-on-error)
| +--rw tile-size? uint8
| +--rw tile-in-All1? schc:all1-data-type
| +--rw ack-behavior? schc:ack-behavior-type
+--:(compression)
+--rw entry* [field-id field-position direction-indicator]
+--rw field-id schc:field-id-type
+--rw field-length schc:field-length-type
+--rw field-position uint8
+--rw direction-indicator schc:direction-indicator-type
+--rw target-values* [position]
| +--rw value? union
| +--rw position uint16
+--rw matching-operator schc:matching-operator-type
+--rw matching-operator-value* [position]
| +--rw value? union
| +--rw position uint16
+--rw comp-decomp-action schc:comp-decomp-action-type
+--rw comp-decomp-action-value* [position]
+--rw value? union
+--rw position uint16
This document has no request to IANA.¶
This document does not have any more Security consideration than the ones already raised on [RFC8724]¶
The authors would like to thank Dominique Barthel, Carsten Bormann, Alexander Pelov.¶
<code begins> file schc@2020-02-28.yang
module schc{
yang-version "1";
namespace "urn:ietf:lpwan:schc:rules-description";
prefix "schc";
description
"Generic Data model for Static Context Header Compression Rule for SCHC,
based on draft-ietf-lpwan-ipv6-static-context-hc-18. Include compression
rules and fragmentation rules.
This module is a YANG model for SCHC rules (RFc 8724).
RFC 8724 describes a rule in a abstract way through a table.
|-----------------------------------------------------------------|
| (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||
+-------+--+--+--+------------+-----------------+---------------+||
|-----------------------------------------------------------------|
This module proposes a global data model that can be used for rule
exchanges or modification. It proposes both the data model format and
the global identifiers used to describes some operations in fields.
This data model applies both to compression and fragmentation.";
revision 2020-06-15 {
description "clean up and add descriptions, merge schc-id to this file";
}
revision 2020-02-28 {
description "Add Fragmentation parameters";
}
revision 2020-01-23 {
description "Modified TV with binary and union";
}
revision 2020-01-07 {
description "First version of the YANG model";
}
// -------------------------
// Field ID type definition
//--------------------------
// generic value TV definition
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-ipv6-flowlabel {
base field-id-base-type;
description "IPv6 Flow Label field from RFC8200";
}
identity fid-ipv6-payloadlength {
base field-id-base-type;
description "IPv6 Payload Length field from RFC8200";
}
identity fid-ipv6-nextheader {
base field-id-base-type;
description "IPv6 Next Header field from RFC8200";
}
identity fid-ipv6-hoplimit {
base field-id-base-type;
description "IPv6 Next Header field from RFC8200";
}
identity fid-ipv6-devprefix {
base field-id-base-type;
description "correspond either to the source address or the desdination
address prefix of RFC 8200. Depending if it is respectively
a uplink or an downklink message.";
}
identity fid-ipv6-deviid {
base field-id-base-type;
description "correspond either to the source address or the desdination
address prefix of RFC 8200. Depending if it is respectively
a uplink or an downklink message.";
}
identity fid-ipv6-appprefix {
base field-id-base-type;
description "correspond either to the source address or the desdination
address prefix of RFC 768. Depending if it is respectively
a downlink or an uplink message.";
}
identity fid-ipv6-appiid {
base field-id-base-type;
description "correspond either to the source address or the desdination
address prefix of RFC 768. Depending if it is respectively
a downlink or an uplink message.";
}
identity fid-udp-dev-port {
base field-id-base-type;
description "UDP length from RFC 768";
}
identity fid-udp-app-port {
base field-id-base-type;
description "UDP length from RFC 768";
}
identity fid-udp-length {
base field-id-base-type;
description "UDP length from RFC 768";
}
identity fid-udp-checksum {
base field-id-base-type;
description "UDP length from RFC 768";
}
identity fid-coap-version {
base field-id-base-type;
description "CoAP version from RFC 7252";
}
identity fid-coap-type {
base field-id-base-type;
description "CoAP type from RFC 7252";
}
identity fid-coap-tkl {
base field-id-base-type;
description "CoAP token length from RFC 7252";
}
identity fid-coap-code {
base field-id-base-type;
description "CoAP code from RFC 7252";
}
identity fid-coap-code-class {
base field-id-base-type;
description "CoAP code class from RFC 7252";
}
identity fid-coap-code-detail {
base field-id-base-type;
description "CoAP code detail from RFC 7252";
}
identity fid-coap-mid {
base field-id-base-type;
description "CoAP message ID from RFC 7252";
}
identity fid-coap-token {
base field-id-base-type;
description "CoAP token from RFC 7252";
}
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";
}
identity fid-coap-option-etag {
base field-id-base-type;
description "CoAP option Etag from RFC 7252";
}
identity fid-coap-option-if-none-match {
base field-id-base-type;
description "CoAP option if-none-match from RFC 7252";
}
identity fid-coap-option-observe {
base field-id-base-type;
description "CoAP option Observe from RFC 7641";
}
identity fid-coap-option-uri-port {
base field-id-base-type;
description "CoAP option Uri-Port from RFC 7252";
}
identity fid-coap-option-location-path {
base field-id-base-type;
description "CoAP option Location-Path from RFC 7252";
}
identity fid-coap-option-uri-path {
base field-id-base-type;
description "CoAP option Uri-Path from RFC 7252";
}
identity fid-coap-option-content-format {
base field-id-base-type;
description "CoAP option Content Format from RFC 7252";
}
identity fid-coap-option-max-age {
base field-id-base-type;
description "CoAP option Max-Age from RFC 7252";
}
identity fid-coap-option-uri-query {
base field-id-base-type;
description "CoAP option Uri-Query from RFC 7252";
}
identity fid-coap-option-accept {
base field-id-base-type;
description "CoAP option Max-Age from RFC 7252";
}
identity fid-coap-option-location-query {
base field-id-base-type;
description "CoAP option Location-Query from RFC 7252";
}
identity fid-coap-option-block2 {
base field-id-base-type;
description "CoAP option Block2 from RFC 7959";
}
identity fid-coap-option-block1 {
base field-id-base-type;
description "CoAP option Block1 from RFC 7959";
}
identity fid-coap-option-size2 {
base field-id-base-type;
description "CoAP option size2 from RFC 7959";
}
identity fid-coap-option-proxy-uri {
base field-id-base-type;
description "CoAP option Proxy-Uri from RFC 7252";
}
identity fid-coap-option-proxy-scheme {
base field-id-base-type;
description "CoAP option Proxy-scheme from RFC 7252";
}
identity fid-coap-option-size1 {
base field-id-base-type;
description "CoAP option Size1 from RFC 7252";
}
identity fid-coap-option-no-response {
base field-id-base-type;
description "CoAP option No response from RFC 7967";
}
identity fid-coap-option-oscore-flags {
base field-id-base-type;
description "CoAP option oscore flags (see draft schc coap, section 6.4)";
}
identity fid-coap-option-oscore-piv {
base field-id-base-type;
description "CoAP option oscore flags (see draft schc coap, section 6.4)";
}
identity fid-coap-option-oscore-kid {
base field-id-base-type;
description "CoAP option oscore flags (see draft schc coap, section 6.4)";
}
identity fid-coap-option-oscore-kidctx {
base field-id-base-type;
description "CoAP option oscore flags (see draft schc coap, section 6.4)";
}
identity fid-icmpv6-type {
base field-id-base-type;
description "ICMPv6 field (see draft OAM)";
}
identity fid-icmpv6-code {
base field-id-base-type;
description "ICMPv6 field (see draft OAM)";
}
identity fid-icmpv6-checksum {
base field-id-base-type;
description "ICMPv6 field (see draft OAM)";
}
identity fid-icmpv6-identifier {
base field-id-base-type;
description "ICMPv6 field (see draft OAM)";
}
identity fid-icmpv6-sequence {
base field-id-base-type;
description "ICMPv6 field (see draft OAM)";
}
/// !!!!!!! See future CoAP extentions
//----------------------------------
// Field Length type definition
//----------------------------------
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";
}
//---------------------------------
// Direction Indicator type
//---------------------------------
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";
}
//----------------------------------
// Matching Operator type definition
//----------------------------------
identity matching-operator-base-type {
description "used to extend Matching Operators with SID values";
}
identity mo-equal {
base matching-operator-base-type;
description "RFC 8724";
}
identity mo-ignore {
base matching-operator-base-type;
description "RFC 8724";
}
identity mo-msb {
base matching-operator-base-type;
description "RFC 8724";
}
identity mo-matching {
base matching-operator-base-type;
description "RFC 8724";
}
//------------------------------
// CDA type definition
//------------------------------
identity compression-decompression-action-base-type;
identity cda-not-sent {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-value-sent {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-lsb {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-mapping-sent {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-compute-length {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-compute-checksum {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-deviid {
base compression-decompression-action-base-type;
description "RFC 8724";
}
identity cda-appiid {
base compression-decompression-action-base-type;
description "RFC 8724";
}
// -- type definition
typedef field-id-type {
description "Field ID generic type.";
type identityref {
base field-id-base-type;
}
}
typedef field-length-type {
description "Field length either a positive integer giving the size in bits
or a function defined through an identityref.";
type union {
type int64; /* positive length in bits */
type identityref { /* function */
base field-length-base-type;
}
}
}
typedef direction-indicator-type {
description "direction in LPWAN network, up when emitted by the device,
down when received by the device, bi when emitted or received by the device.";
type identityref {
base direction-indicator-base-type;
}
}
typedef matching-operator-type {
description "Matching Operator (MO) to compare fields values with target values";
type identityref {
base matching-operator-base-type;
}
}
typedef comp-decomp-action-type {
description "Compression Decompression Action to compression or decompress a field.";
type identityref {
base compression-decompression-action-base-type;
}
}
// -- FRAGMENTATION TYPE
// -- fragmentation modes
identity fragmentation-mode-base-type {
description "fragmentation mode";
}
identity fragmentation-mode-no-ack {
description "No Ack of RFC 8724.";
base fragmentation-mode-base-type;
}
identity fragmentation-mode-ack-always {
description "Ack Always of RFC8724.";
base fragmentation-mode-base-type;
}
identity fragmentation-mode-ack-on-error {
description "Ack on Error of RFC8724.";
base fragmentation-mode-base-type;
}
typedef fragmentation-mode-type {
type identityref {
base fragmentation-mode-base-type;
}
}
// -- Ack behavior
identity ack-behavior-base-type {
description "define when to send an Acknowledgment message";
}
identity ack-behavior-after-All0 {
description "fragmentation expects Ack after sending All0 fragment.";
base ack-behavior-base-type;
}
identity ack-behavior-after-All1 {
description "fragmentation expects Ack after sending All1 fragment.";
base ack-behavior-base-type;
}
identity ack-behavior-always {
description "fragmentation expects Ack after sending every fragment.";
base ack-behavior-base-type;
}
typedef ack-behavior-type {
type identityref {
base ack-behavior-base-type;
}
}
// -- All1 with data types
identity all1-data-base-type {
description "type to define when to send an Acknowledgment message";
}
identity all1-data-no {
description "All1 contains no tiles.";
base all1-data-base-type;
}
identity all1-data-yes {
description "All1 MUST contain a tile";
base all1-data-base-type;
}
identity all1-data-sender-choice {
description "Fragmentation process choose to send tiles or not in all1.";
base all1-data-base-type;
}
typedef all1-data-type {
type identityref {
base all1-data-base-type;
}
}
// -- RCS algorithm types
identity RCS-algorithm-base-type {
description "identify which algorithm is used to compute RSC.
The algorithm defines also the size if the RSC field.";
}
identity RFC8724-RCS {
description "CRC 32 defined as default RCS in RFC8724.";
base RCS-algorithm-base-type;
}
typedef RCS-algorithm-type {
type identityref {
base RCS-algorithm-base-type;
}
}
// -------- RULE ENTRY DEFINITION ------------
grouping target-values-struct {
description "defines the target value element. Can be either an arbitrary
binary or ascii element. All target values are considered as a matching lists.
Position is used to order values, by default position 0 is used when containing
a single element.";
leaf value {
type union {
type binary;
type string;
}
}
leaf position {
description "If only one element position is 0, otherwise position is the
matching list.";
type uint16;
}
}
grouping compression-rule-entry {
description "These entries defines a compression entry (i.e. a line)
as defined in RFC 8724 and fragmentation parameters.
+-------+--+--+--+------------+-----------------+---------------+
|Field 1|FL|FP|DI|Target Value|Matching Operator|Comp/Decomp Act|
+-------+--+--+--+------------+-----------------+---------------+
An entry in a compression rule is composed of 7 elements:
- Field ID: The header field to be compressed. The content is a YANG identifer.
- Field Length : either a positive integer of a function defined as a YANF id.
- Field Position: a positive (and possibly equal to 0) integer.
- Direction Indicator: a YANG identifier giving the direction.
- Target value: a value against which the header Field is compared.
- Matching Operator: a YANG id giving the operation, paramters may be
associated to that operator.
- Comp./Decomp. Action: A YANG id giving the compression or decompression
action, paramters may be associated to that action.
";
leaf field-id {
description "Field ID, identify a field in the header with a YANG refenceid.";
mandatory true;
type schc:field-id-type;
}
leaf field-length {
description "Field Length in bit or through a function defined as a YANG referenceid";
mandatory true;
type schc:field-length-type;
}
leaf field-position {
description "field position in the header is a integer. If the field is not repeated
in the header the value is 1, and incremented for each repetition of the field. Position
0 means that the position is not important and order may change when decompressed";
mandatory true;
type uint8;
}
leaf direction-indicator {
description "Direction Indicator, a YANG referenceid to say if the packet is bidirectionnal,
up or down";
mandatory true;
type schc:direction-indicator-type;
}
list target-values {
description "a list of value to compare with the header field value. If target value
is a singleton, position must be 0. For matching-list, should be consecutive position
values starting from 1.";
key position;
uses target-values-struct;
}
leaf matching-operator {
mandatory true;
type schc:matching-operator-type;
}
list matching-operator-value {
key position;
uses target-values-struct;
}
leaf comp-decomp-action {
mandatory true;
type schc:comp-decomp-action-type;
}
list comp-decomp-action-value {
key position;
uses target-values-struct;
}
}
grouping compression-content {
description "define a compression rule composed of a list of entries.";
list entry {
key "field-id field-position direction-indicator";
uses compression-rule-entry;
}
}
grouping fragmentation-content {
description "This grouping defines the fragmentation parameters for
all the modes (No Ack, Ack Always and Ack on Error) specified in
RFC 8724.";
leaf direction {
type schc:direction-indicator-type;
description "should be up or down, bi directionnal is forbiden.";
mandatory true;
}
leaf dtagsize {
type uint8;
description "size in bit of the DTag field";
}
leaf wsize {
type uint8;
description "size in bit of the window field";
}
leaf fcnsize {
type uint8;
description "size in bit of the FCN field";
mandatory true;
}
leaf RCS-algorithm {
type RCS-algorithm-type;
default schc:RFC8724-RCS;
description "Algoritm used for RCS";
}
leaf maximum-window-size {
type uint16;
description "by default 2^wsize - 1";
}
leaf retransmission-timer {
type uint64 {
range 1..max;
}
description "duration in seconds of the retransmission timer"; // Check the units
}
leaf inactivity-timer {
type uint64;
description "duration is seconds of the inactivity timer, 0 indicates the timer is disabled"; // check units
}
leaf max-ack-requests {
type uint8 {
range 1..max;
}
description "the maximum number of retries for a specific SCHC ACK.";
}
leaf maximum-packet-size {
type uint16;
default 1280;
description "When decompression is done, packet size must not strictly exceed this limit in Bytes";
}
leaf fragmentation-mode {
type schc:fragmentation-mode-type;
description "which fragmentation mode is used (noAck, AckAlways, AckonError)";
mandatory true;
}
choice mode {
case no-ack;
case ack-always;
case ack-on-error {
leaf tile-size {
type uint8;
description "size in bit of tiles, if not specified or set to 0: tile fills the fragment.";
}
leaf tile-in-All1 {
type schc:all1-data-type;
description "When true, sender and receiver except a tile in All-1 frag";
}
leaf ack-behavior {
type schc:ack-behavior-type;
description "Sender behavior to acknowledge, after All-0, All-1 or when the
LPWAN allows it (Always)";
}
}
}
}
// Define rule ID. Rule ID is composed of a RuleID value and a Rule ID Length
grouping rule-id-type {
leaf rule-id {
type uint32;
description "rule ID value, this value must be unique combined with the length";
}
leaf rule-length {
type uint8 {
range 0..32;
}
description "rule ID length in bits, value 0 is for implicit rules";
}
}
// SCHC table for a specific device.
container schc {
leaf version{
type uint64;
mandatory false;
description "used as an indication for versioning";
}
list rule {
key "rule-id rule-length";
uses rule-id-type;
choice nature {
case fragmentation {
uses fragmentation-content;
}
case compression {
uses compression-content;
}
}
}
}
}
<code ends>