Toward RFC 9363bis: Changes to the SCHC YANG Data Model
draft-toutain-schc-toward-rfc9363bis-00
This document is an Internet-Draft (I-D).
Anyone may submit an I-D to the IETF.
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Laurent Toutain , Marco Tiloca , Ana Minaburo , Samar Sirohi | ||
| Last updated | 2026-09-23 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Yang Validation | 11 errors, 5 warnings | ||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-toutain-schc-toward-rfc9363bis-00
SCHC L. Toutain
Internet-Draft Institut MINES TELECOM; IMT Atlantique
Intended status: Standards Track M. Tiloca
Expires: 27 March 2027 RISE AB
A. Minaburo
Consultant
S. Sirohi
Institut MINES TELECOM; IMT Atlantique
23 September 2026
Toward RFC 9363bis: Changes to the SCHC YANG Data Model
draft-toutain-schc-toward-rfc9363bis-00
Abstract
This document is not a revision of RFC 9363, "A YANG Data Model for
Static Context Header Compression (SCHC)": it identifies changes --
additions to, and removals from, its YANG data model -- motivated by
discussions in the SCHC working group and by drafts published since
RFC 9363. These changes include more flexible compression Rule
entries through the use of Universal Options, which allow identifiers
to be added to or removed from a Rule Description depending on the
Universal Options in use; some new Field Length functions, and new
Matching Operators (MOs) and Compression/Decompression Actions
(CDAs); and a mechanism for the manual allocation of YANG Schema Item
iDentifiers (SIDs). Once the working group agrees on the resulting
wording, these changes are intended to be incorporated into a future
revision of RFC 9363.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at . Status
information for this document may be found at
https://datatracker.ietf.org/doc/draft-toutain-schc-toward-
rfc9363bis/.
Discussion of this document takes place on the SCHC Working Group
mailing list (mailto:schc@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/schc/. Subscribe at
https://www.ietf.org/mailman/listinfo/schc/.
Source for this draft and an issue tracker can be found at
https://github.com/.
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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-
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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 27 March 2027.
Copyright Notice
Copyright (c) 2026 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 Revised BSD License text as
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Universal Options . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Space ID . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Deprecating the Per-Option CoAP FIDs . . . . . . . . . . 7
3.3. OSCORE and KUDOS Suboptions . . . . . . . . . . . . . . . 10
3.4. Field Length Functions . . . . . . . . . . . . . . . . . 11
3.5. Example 1: OSCORE outer header . . . . . . . . . . . . . 12
4. Variable Length in Bits . . . . . . . . . . . . . . . . . . . 13
4.1. Example, Non-Byte-Aligned MSB Residue . . . . . . . . . . 14
5. ICMPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1. New FID . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.2. New Matching Operators and Compression/Decompression
Actions . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.2.1. Example, ICMPv6 Error with Reverse Compression . . . 16
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5.3. Alternative: Include IPv6 in Header Format . . . . . . . 18
6. Action . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7. Compound ACK . . . . . . . . . . . . . . . . . . . . . . . . 22
8. Rule Management . . . . . . . . . . . . . . . . . . . . . . . 22
9. Manual SID Allocation . . . . . . . . . . . . . . . . . . . . 25
10. Security Considerations . . . . . . . . . . . . . . . . . . . 26
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 26
12.1. Normative References . . . . . . . . . . . . . . . . . . 26
12.2. Informative References . . . . . . . . . . . . . . . . . 27
Appendix A. Full YANG Module . . . . . . . . . . . . . . . . . . 30
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 77
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 77
1. Introduction
This document is not itself a revision of RFC 9363 [RFC9363], the
YANG data model for Static Context Header Compression (SCHC)
[RFC8724]. Instead, it identifies the items that should be added to,
or removed from, that data model, taking into account discussions
held in the SCHC working group and drafts published since RFC 9363
(e.g. [I-D.ietf-schc-universal-option], [I-D.ietf-schc-8824-update],
and [I-D.ietf-schc-icmpv6-compression]). Once the working group
agrees on the resulting wording, a new revision of RFC 9363 will be
issued to formally incorporate it.
This document also introduces the framework for Rule management; the
details of Rule management are left to separate documents.
2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Universal Options
In RFC 9363 [RFC9363], each field found in a header is referenced by
a globally unique identifier called a Field ID (FID). The SCHC YANG
module defines an identityref for each FID. This static allocation
approach breaks down when a protocol carries options, such as CoAP
[RFC7252]: new options appear regularly, and the mapping between an
option number and a FID is not trivial.
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[I-D.ietf-schc-universal-option] augments the compression Rule entry,
in which the FID is replaced by a tuple made of a space ID and the
option number, so that any option of a given protocol can be
referenced without allocating a dedicated FID for it. In this
approach, the key used to access a regular field entry remains the
FID, the Direction Indicator, and the position, while the key used to
access an option entry becomes the space ID, the option number, and
the position.
This key-based approach does not guarantee that entries appear in the
same order as the corresponding fields in the header (all the options
will appear at the end of the rule), whereas RFC 8724 [RFC8724]
mandates that order and recent implementations have shown it to be
efficient. In addition, these three- or four-element keys remain
large, which may be a penalty when Rule management is used (see
Section 8).
This document deprecates the whole compression Rule entry structure
in favor of a new one, providing a uniform way to reference a field
entry. A new "entry-index" leaf is introduced as the key of the new
"entry-universal" list. The list is defined as "ordered-by user",
and "entry-index" values are assigned sequentially according to the
order of the entries in that list. The list order therefore
continues to convey the header field order (addressing the second
problem).
"entry-index" is then followed by a choice between a field-id and a
space-id/option-number. The rest of the entry is unchanged, except
for the new "field-length-value" leaf, added to carry the entry-index
argument discussed later.
RFC 7950 [RFC7950], Section 11, does not allow the "entry" list's
key, nor the "field-id" leaf, to be changed in place in a published
module ("Otherwise, if the semantics of any previous definition are
changed [...] then this MUST be achieved by a new definition with a
new identifier"). This document therefore leaves the RFC 9363
"compression-rule-entry" grouping, its "compression-content"
grouping, and the "compression" case untouched, and marks them
"status deprecated;" (RFC 8407 recommends a "deprecated" status be
kept for at least one year before moving to "obsolete"). The new
structure is defined in a new "compression-rule-entry-universal"
grouping, used by a new "compression-content-universal" grouping and
a new "compression-universal" case, sitting alongside the deprecated
ones in the "nature" choice.
Figure 1 shows the resulting YANG tree diagram for both cases
(deprecated "compression" and new "compression-universal").
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x--:(compression) {compression}?
| x--rw entry* [field-id field-position direction-indicator]
| +--rw field-id fid-type
| +--rw field-length union
| +--rw field-position uint8
| +--rw direction-indicator di-type
| +--rw target-value* [index]
| | +--rw index uint16
| | +--rw value? binary
| +--rw matching-operator mo-type
| +--rw matching-operator-value* [index]
| | +--rw index uint16
| | +--rw value? binary
| +--rw comp-decomp-action cda-type
| +--rw comp-decomp-action-value* [index]
| +--rw index uint16
| +--rw value? binary
+--:(compression-universal) {compression or management}?
+--rw entry-universal* [entry-index]
| +--rw entry-index uint16
| +--rw (field-or-space)
| | +--:(regular-field)
| | | +--rw field-id fid-type
| | +--:(universal-option)
| | +--rw space-id space-id-type
| | +--rw universal-value uint64
| +--rw field-length union
| +--rw field-length-value? uint16
| +--rw field-position uint8
| +--rw direction-indicator di-type
| +--rw target-value* [index]
| | +--rw index uint16
| | +--rw value? binary
| +--rw matching-operator mo-type
| +--rw matching-operator-value* [index]
| | +--rw index uint16
| | +--rw value? binary
| +--rw comp-decomp-action cda-type
| +--rw comp-decomp-action-value* [index]
| +--rw index uint16
| +--rw value? binary
+--rw action? action-type
+--rw action-value* [index]
+--rw index uint16
+--rw value? binary
Figure 1: Compression Rule Entry: deprecated (RFC 9363) and new
(-universal) cases
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Unlike the deprecated "entry" list, keyed by the compound "field-
id"/"field-position"/"direction-indicator", "entry-universal" is
keyed by the single-leaf "entry-index". This makes an entry cheap
and unambiguous to reference from elsewhere within the same Rule,
e.g. the "field-length-value" argument of "fl-length-bytes" and "fl-
length-bits" (Section 3.4), or a management operation targeting it
(Section 8).
3.1. Space ID
Several protocols define options: CoAP [RFC7252] is one example, but
other protocols define their own options too, each with its own
option numbering. A single "space-id" value is therefore not enough
by itself; it must be qualified by the protocol (option space) it
belongs to.
To identify these option spaces, this document creates a "space-id-
base-type" identity and derives one identity per protocol from it; a
"space-id-type" typedef is then created from "space-id-base-type",
following the identityref pattern used throughout RFC 9363 (e.g. for
"rcs-algorithm-type"). At present, the module only defines one such
identity, "space-id-coap", for the CoAP option space; other protocols
that define options can add their own "space-id-*" identity the same
way. Figure 2 shows this pattern, mirroring how RFC 9363 introduces
its own identityref-derived types.
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identity space-id-base-type {
base schc:space-field-id-base-type;
description
"Base identity for a Universal Option space. Several
protocols define options (e.g. CoAP); each such protocol
is identified by an identity derived from this base type.";
}
identity space-id-coap {
base space-id-base-type;
description
"Space ID identifying the CoAP option space.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
typedef space-id-type {
type identityref {
base space-id-base-type;
}
description
"Space ID type for universal option spaces (CoAP options,
etc.). Used in the universal-option case of
compression-rule-entry-universal.";
}
Figure 2: Space ID: base identity, one derived identity per
protocol, and typedef
"space-id-type" is used, together with "space-id-base-type" and "fid-
base-type"'s common ancestor "space-field-id-base-type", by the
"field-or-space" choice (see Figure 1).
3.2. Deprecating the Per-Option CoAP FIDs
RFC 9363 defines twenty per-option Field IDs deriving from "fid-coap-
option", one for each CoAP option registered at the time (see
Table 1). Now that Universal Options provide a "space-id-
coap"/"universal-value" pair to reference any CoAP option by its
option number, without needing a dedicated FID for it, each of these
twenty identities is superseded and marked deprecated.
RFC 7950 [RFC7950], Section 11, states that "Obsolete definitions
MUST NOT be removed from published modules, since their identifiers
may still be referenced by other modules": once RFC 9363 is
published, these twenty identities can only ever be marked
"deprecated" and then "obsolete"; they can never simply disappear
from a later revision of the module. RFC 8407 [RFC8407],
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Section 4.7, further recommends that "an object SHOULD be available
for at least one year with a 'deprecated' status before it is changed
to 'obsolete'", and that "the status SHOULD NOT be changed from
'current' directly to 'obsolete'": since these twenty identities are
"current" in RFC 9363, this document marks them "deprecated" rather
than "obsolete".
These twenty identities MUST NOT be used in a new "entry-universal"
list (Figure 1): the "space-id"/ "universal-value" pair introduced in
Section 3 supersedes them there. They remain usable only in the
deprecated "entry" list, for Rules that already reference them.
IANA has allocated the SID range 2550-2949 to the "ietf-schc" module.
At the time of writing, no SID file for "ietf-schc" is registered in
the IETF YANG-SID Modules registry. None from the range registered
for RFC 9363 MUST be allocated to these twenty deprecated identities:
a SID "immutably maps to EXACTLY one YANG name", so allocating one to
an identity already superseded by Universal Options would waste it
permanently, with no way to reclaim it later.
The working copy of the module has been corrected accordingly: the
twenty identities are present, each with "status deprecated;" (see
Figure 3).
+=================+===========+=========================+===========+
| RFC 9363 FID | CoAP | Replaced by (space-id- | Defined |
| | Option | coap / universal-value) | in |
+=================+===========+=========================+===========+
| fid-coap- | If-Match | 1 | [RFC7252] |
| option-if- | | | |
| match | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Uri-Host | 3 | [RFC7252] |
| option-uri- | | | |
| host | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | ETag | 4 | [RFC7252] |
| option-etag | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | If-None- | 5 | [RFC7252] |
| option-if- | Match | | |
| none-match | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Observe | 6 | [RFC7641] |
| option-observe | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Uri-Port | 7 | [RFC7252] |
| option-uri- | | | |
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| port | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Location- | 8 | [RFC7252] |
| option- | Path | | |
| location-path | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Uri-Path | 11 | [RFC7252] |
| option-uri- | | | |
| path | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Content- | 12 | [RFC7252] |
| option- | Format | | |
| content-format | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Max-Age | 14 | [RFC7252] |
| option-max-age | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Uri-Query | 15 | [RFC7252] |
| option-uri- | | | |
| query | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Accept | 17 | [RFC7252] |
| option-accept | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Location- | 20 | [RFC7252] |
| option- | Query | | |
| location-query | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Block2 | 23 | [RFC7959] |
| option-block2 | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Block1 | 27 | [RFC7959] |
| option-block1 | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Size2 | 28 | [RFC7959] |
| option-size2 | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Proxy-Uri | 35 | [RFC7252] |
| option-proxy- | | | |
| uri | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Proxy- | 39 | [RFC7252] |
| option-proxy- | Scheme | | |
| scheme | | | |
+-----------------+-----------+-------------------------+-----------+
| fid-coap- | Size1 | 60 | [RFC7252] |
| option-size1 | | | |
+-----------------+-----------+-------------------------+-----------+
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| fid-coap- | No- | 258 | [RFC7967] |
| option-no- | Response | | |
| response | | | |
+-----------------+-----------+-------------------------+-----------+
Table 1: RFC 9363 per-option CoAP FIDs and their Universal Option
replacement
identity fid-coap-option-uri-path {
base fid-coap-option;
status deprecated;
description
"CoAP option Uri-Path. Deprecated in favor of Universal
Options (space-id-coap / universal-value).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
Figure 3: Example: Deprecating a Per-Option CoAP FID (fid-coap-
option-uri-path)
3.3. OSCORE and KUDOS Suboptions
Universal Options allow any option to be compressed following the
SCHC principle, but compression can be more efficient when the sub-
fields of an option are taken into account individually. This is why
the module introduces specific fields for OSCORE [RFC8613] and KUDOS
[I-D.ietf-core-oscore-key-update]: each option is split into sub-
fields, each with its own identity ("fid-coap-option-oscore-piv",
"fid-coap-option-oscore-kid", "fid-coap-option-oscore-kidctx", "fid-
coap-option-kudos-nonce", etc.).
Note that the Flags field, for both OSCORE and KUDOS, is also split
so that its length indicator becomes a specific field of its own:
"fid-coap-option-oscore-flags-flagbits"/"fid-coap-option-oscore-
flags-n" for OSCORE, and "fid-coap-option-kudos-x-flagbits"/ "fid-
coap-option-kudos-x-m" for KUDOS. This will be exploited by the new
Field Length functions introduced in Section 3.4, which can reference
such a field, by its "entry-index", to determine the length of
another field (e.g. the Partial IV).
KUDOS's "fid-coap-option-kudos-x-m" cannot be treated in the same way
as OSCORE's "fid-coap-option-oscore-flags-n" for this purpose. The
value "m" encodes the Nonce length in bytes minus one; equivalently,
the Nonce length is "m + 1". Since "fl-length-bytes" and "fl-length-
bits" directly use the value of the referenced entry as the length,
they cannot directly represent this relationship. KUDOS therefore
requires separate handling of this length transformation.
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"fid-coap-option" itself is kept "current": it is still used,
unchanged, as the base identity of these OSCORE and KUDOS suboption
FIDs. Unlike the twenty per-option FIDs deprecated in the previous
subsection, they use "fid-coap-option" as a typing hierarchy for
parts of a single CoAP option (OSCORE, KUDOS), not as a stand-in for
an arbitrary CoAP option, and are therefore unaffected: they remain
"current".
3.4. Field Length Functions
RFC 8824 [RFC8824] defines a specific length function for the Token
field: when this function is specified, the value of the Token Length
(TKL) is used to indicate the length of the field.
[I-D.ietf-schc-8824-update] extends this principle to the Partial IV
field for OSCORE.
This approach is not scalable: a new function would have to be
defined for every new protocol field whose length needs to be carried
this way. This document instead introduces two new functions, "fl-
length-bytes" and "fl-length-bits". They both take an argument,
carried in the new Rule entry field "field-length-value", that points
to the entry where the length is specified, referenced by its "entry-
index" (see Figure 1). Having two separate functions, rather than a
single generic one, also conveys the unit of the length value: bytes
for "fl-length-bytes", bits for "fl-length-bits".
* "fl-length-bytes" generalizes "fl-token-length": for example, "fl-
token-length" is now equivalent to "fl-length-bytes(index)", where
"index" is the "entry-index" of the CoAP TKL field.
* "fl-length-bits" is the bit-level equivalent of "fl-length-bytes".
This is what Section 3.3 relies on: the OSCORE and KUDOS Flags field
is split so that its length indicator ("fid-coap-option-oscore-flags-
n", "fid-coap-option-kudos-x-m") is its own entry; "fl-length-bytes"
or "fl-length-bits" can then use that entry's "entry-index" to derive
the length of the corresponding Partial IV field. This works
directly for OSCORE; Section 3.3 explains why the same does not hold
for KUDOS's Nonce.
This document also introduces "fl-remaining", for an entry that is
always the last one in the Rule (see Section 5's "fid-payload").
Unlike "fl-variable", which prefixes its residue with an explicit
length (see Section 4), "fl-remaining" accepts a field of any length
but does not add that prefix when serializing the residue: being the
last entry, its residue already runs to the end of the compression
residue and needs no delimiter.
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3.5. Example 1: OSCORE outer header
Figure 4 shows an example SCHC Compression Rule (Rule ID 2, encoded
on 5 bits, i.e. "00010") that compresses, in both directions, the
outer CoAP header of a CoAP/OSCORE message.
The server is located on the Application side and the client on the
Device side. In OSCORE, the client's request carries an OSCORE
option with the security parameters, while the server's response
carries an empty OSCORE option; the Token links the response to its
request.
The first column is new and not defined in RFC 8724 [RFC8724]: it
numbers the entries in the rule. The names in the other columns are
the ones defined in the YANG module, without their prefix ("fid-",
"fl-", "mo-", "cda-"), for better legibility.
+----+----------------+----------+----+----+----+--------+----------+
| # | Field | FL | FP | DI | TV | MO | CDA |
+----+----------------+----------+----+----+----+--------+----------+
| 0 | coap-version | 2 | 1 | Bi | 01 | equal | not-sent |
| 1 | coap-type | 2 | 1 | Bi | - | ignore | value- |
| | | | | | | | sent |
| 2 | coap-tkl | 4 | 1 | Bi | - | ignore | value- |
| | | | | | | | sent |
| 3 | coap-code | 8 | 1 | Up | 02 | equal | not-sent |
| 4 | coap-code | 8 | 1 | Dw | 44 | equal | not-sent |
| 5 | coap-mid | 16 | 1 | Bi | 00 | ignore | value- |
| | | | | | | | sent |
| 6 | coap-token | length- | 1 | Bi | - | ignore | value- |
| | | bytes(2) | | | | | sent |
| 7 | coap-option- | 5 | 1 | Up | 01 | equal | not-sent |
| | oscore-flags- | | | | | | |
| | flagbits | | | | | | |
| 8 | coap-option- | 3 | 1 | Up | 01 | equal | not-sent |
| | oscore-flags-n | | | | | | |
| 9 | coap-option- | length- | 1 | Up | - | ignore | value- |
| | oscore-piv | bytes(8) | | | | | sent |
| 10 | coap-option- | 0 | 1 | Up | 00 | equal | not-sent |
| | oscore-kidctx | | | | | | |
| 11 | coap-option- | var | 1 | Up | - | ignore | value- |
| | oscore-kid | | | | | | sent |
| 12 | space-id- | 0 | 1 | Dw | - | equal | not-sent |
| | coap(9) | | | | | | |
+----+----------------+----------+----+----+----+--------+----------+
Figure 4: Example Compression Rule for an Outer CoAP/OSCORE Header
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This rule uses the new capabilities introduced above:
* The Token field's length no longer uses the legacy "fl-token-
length" function; instead, "fl-length-bytes" is used, with its
parameter set to 2, referring to entry 2, "coap-tkl".
* The OSCORE option's content is split into sub-fields. Note that
the Flags field is itself split between "coap-option-oscore-flags-
flagbits" and "coap-option-oscore-flags-n", the latter carrying
the length of the Partial IV field.
* The Partial IV length is likewise given by "fl-length-bytes", this
time with its parameter set to 8, referring to entry 8, "coap-
option-oscore-flags-n".
* In the other direction, the OSCORE option is empty and is
compressed using a Universal Option, indicating option number 9.
TO BE DISCUSSED: the "h" flag is set to 0, meaning the KID Context is
normally absent; should entry 10, "coap-option-oscore-kidctx", still
appear in the rule in that case? When present, the KID Context value
is itself encoded as a length byte followed by the context bytes.
Should this document keep it as a single "coap-option-oscore-kidctx"
entry of variable length -- which would send that length twice, once
through SCHC's own variable-length encoding and once through the
length byte already embedded in the OSCORE encoding -- or split it
into two entries, a length indicator and the context value, with the
latter using "fl-length-bytes" to point to the former?
4. Variable Length in Bits
"fl-variable-bits" generalizes RFC 8824's [RFC8824] "fl-variable" to
bit-level variable-length fields, the same way
[I-D.ietf-schc-8824-update]'s "var_bit" function does. RFC 8724
[RFC8724] requires the "MSB" matching operator's parameter to be a
multiple of 8 bits when applied to a byte-counted variable-length
field ("fl-variable"): the residue sent with the "LSB" action would
otherwise not be an integral number of bytes, and "fl-variable"'s
length prefix, itself byte-counted, could not express it. "fl-
variable-bits" removes that restriction by counting the residue's
length prefix in bits instead of bytes.
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The length prefix itself is encoded the same way as for "fl-
variable", following RFC 8724 [RFC8724], Section 7.4.2: sizes between
0 and 14 (in the unit defined by the FL -- bytes for "fl-variable",
bits for "fl-variable-bits") are encoded as a 4-bit unsigned integer;
sizes between 15 and 254 are encoded as 0b1111 followed by an 8-bit
unsigned integer; larger sizes are encoded as 0xfff followed by a
16-bit unsigned integer. Only the counted unit changes between the
two functions, not the escape structure of the length prefix.
4.1. Example, Non-Byte-Aligned MSB Residue
The case "var_bit" and "fl-variable-bits" actually address is a
variable-length field, whose residue needs an explicit length prefix.
[I-D.ietf-schc-8824-update] itself has such an example, for the
OSCORE "kid" sub-field (entry "coap-option-oscore-kid" in Figure 4,
which instead sends it unmatched): Figure 5. "msb(44)" matches the
KID's most significant 44 bits against the 6-byte (48-bit) target
value; only the remaining 4 bits are sent with "lsb". "var_bit" (this
document's "fl-variable-bits") carries that 4-bit length in its
residue length prefix; RFC 8824's byte-counted "fl-variable" could
not.
+----------------+-----------+----+----+----------+---------+-----+
| Field | FL | FP | DI | TV | MO | CDA |
+----------------+-----------+----+----+----------+---------+-----+
| coap-option- | variable- | 1 | Up | 0x636c69 | msb(44) | lsb |
| oscore-kid | bits | | | 656e70 | | |
+----------------+-----------+----+----+----------+---------+-----+
Figure 5: Non-Byte-Aligned MSB Residue on a Variable-Length Field
(adapted from I-D.ietf-schc-8824-update)
5. ICMPv6
[I-D.ietf-schc-icmpv6-compression] defines how SCHC can interact with
ICMPv6 [RFC4443], either to compress an ICMPv6 message or to generate
one. This document focuses only on the resulting impact on the YANG
Data Model. Since an ICMPv6 message may itself carry an IPv6 header
-- e.g. the offending packet embedded in an error message -- the
draft introduces new Matching Operators and Compression/Decompression
Actions to compress that payload; we open the discussion on an
alternative behavior for it below.
5.1. New FID
[I-D.ietf-schc-icmpv6-compression] introduces eight new Field IDs for
ICMPv6 [RFC4443]:
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* "fid-icmpv6-type", "fid-icmpv6-code", "fid-icmpv6-checksum":
present in every ICMPv6 message.
* "fid-icmpv6-mtu": present in the Packet Too Big message.
* "fid-icmpv6-pointer": present in the Parameter Problem message.
* "fid-icmpv6-identifier", "fid-icmpv6-sequence": present in the
Echo Request/Reply message.
* "fid-icmpv6-payload": the data following the ICMPv6 header.
Two more generic Field IDs, not specific to ICMPv6, are found in the
working copy of the module alongside them. Being generic, they can
be used as-is when compressing other protocols:
* "fid-unused": as its name suggests, used to skip an unused part of
a header. This matters when parsing and compression happen on the
fly, and reinforces the constraint that fields appear in the same
order as in the header. Setting its Target Value to 0, its
Matching Operator to "ignore", and its Compression/Decompression
Action to "not-sent" is RECOMMENDED.
* "fid-payload": MUST be the last entry of the Rule, matching its
position as the packet's trailing payload, and uses the new "fl-
remaining" (Section 3.4), which accepts any length without
prefixing the residue with one, since the last entry's residue
already runs to the end of the SCHC packet. With Matching
Operator "ignore" and Compression/Decompression Action "value-
sent", it behaves exactly as the usual, implicit SCHC behavior,
where the payload simply follows the compression residue. But it
can also be used to intercept the payload: Compression/
Decompression Action "not-sent" then elides it, or another CDA can
apply a special treatment to compress it, instead of sending it
verbatim.
5.2. New Matching Operators and Compression/Decompression Actions
[I-D.ietf-schc-icmpv6-compression] is also the origin of the "mo-
rule-match"/"mo-rev-rule-match" Matching Operators and the "cda-
compress-sent"/"cda-rev-compress-sent" Compression/ Decompression
Actions. "mo-rule-match" returns true if the Target Value matches
another Rule, keeping the Up/Down direction; "mo-rev-rule-match" does
the same but reversing that direction; "cda-compress-sent" and "cda-
rev-compress-sent" send a compressed version of the Target Value,
using respectively the matched Rule or its direction-reversed
counterpart.
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The reversed forms exist because, per RFC 4443 [RFC4443], an ICMPv6
error message carries back as much as possible of the IPv6 packet
that triggered it -- a packet that was sent in the opposite direction
from the error message itself. Compressing that embedded copy
therefore means matching it against, and generating its residue from,
a Rule for the reverse direction.
5.2.1. Example, ICMPv6 Error with Reverse Compression
Figure 6 adapts the "Time Exceeded" Rule from
[I-D.ietf-schc-icmpv6-compression], prefixed with the outer IPv6
header carrying the ICMPv6 message itself (as in Figure 8 below): the
Type and Code identify the error, the Checksum is recomputed on
decompression, the 32-bit "Unused" field mandated by RFC 4443
[RFC4443] for this message is elided with "fid-unused" (Section 5),
and the Payload -- the offending IPv6 packet -- is matched and
compressed against its own (Up) Rule with "rev-rule-match" and "rev-
compress-sent", instead of being sent in full.
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+--------------+-----------+----+----+--------+----------+-----------+
| Field | FL | FP | DI | TV | MO | CDA |
+--------------+-----------+----+----+--------+----------+-----------+
+------------------------ Outer IPv6 header -------------------------+
| ipv6-version | 4 | 1 | Dw | 6 | equal | not-sent |
| ipv6- | 8 | 1 | Dw | 0 | ignore | not-sent |
| trafficclass | | | | | | |
| ipv6- | 20 | 1 | Dw | 0 | ignore | not-sent |
| flowlabel | | | | | | |
| ipv6- | 16 | 1 | Dw | - | ignore | compute |
| payload- | | | | | | |
| length | | | | | | |
| ipv6- | 8 | 1 | Dw | 58 | equal | not-sent |
| nextheader | | | | | | |
| ipv6- | 8 | 1 | Dw | 1 | equal | not-sent |
| hoplimit | | | | | | |
| ipv6- | 64 | 1 | Dw | aaaa:: | equal | not-sent |
| devprefix | | | | | | |
| ipv6-deviid | 64 | 1 | Dw | ::zzzz | equal | not-sent |
| ipv6- | 64 | 1 | Dw | - | ignore | value- |
| appprefix | | | | | | sent |
| ipv6-appiid | 64 | 1 | Dw | - | ignore | value- |
| | | | | | | sent |
+-------------------------- ICMPv6 header ---------------------------+
| icmpv6-type | 8 | 1 | Dw | 3 | equal | not-sent |
| icmpv6-code | 8 | 1 | Dw | [0,1] | match- | mapping- |
| | | | | | mapping | sent |
| icmpv6- | 16 | 1 | Dw | - | ignore | compute |
| checksum | | | | | | |
| unused | 32 | 1 | Dw | 0 | ignore | not-sent |
| icmpv6- | variable- | 1 | Dw | 0 | rev- | rev- |
| payload | bits | | | | rule- | compress- |
| | | | | | match | sent |
+--------------+-----------+----+----+--------+----------+-----------+
Figure 6: ICMPv6 Error Compressed Against a Reverse-Direction
Rule (adapted from I-D.ietf-schc-icmpv6-compression)
Figure 6 shows a Rule inspired by [I-D.ietf-schc-icmpv6-compression].
One difference here is the addition of the "unused" entry, skipping
the 32 bits following the Checksum. The remaining bytes are assigned
to "icmpv6-payload" and contain the original (invoking) header. If a
Rule in the context matches that payload, compression applies to it
as well.
Figure 7 shows the resulting residue: the RuleID of the ICMPv6
message, followed by its own compression residue, then a length for
the variable-length structure, the RuleID of the Rule that compresses
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the original header, that Rule's compression residue, the remaining,
uncompressed payload, and, since this concludes the SCHC packet, the
final padding bits ([RFC8724]) that must bring it to a byte boundary,
since "Length" here counts bytes, not bits: spanning the inner
RuleID, header residue, and payload together, it is typically well
above the 14-byte escape threshold (Section 4), so counting it in
bytes keeps that length prefix itself compact.
|----------------Length-----------------|
+---------+---------+--------+---------+---------+---------+---------+
| RuleID | IPv6/ | Length | RuleID | IPv6/ | Payload | Padding |
| (outer) | ICMPv6 | | (inner) | UDP | | |
| | residue | | | residue | | |
+---------+---------+--------+---------+---------+---------+---------+
Figure 7: Residue Layout for an ICMPv6 Error Compressing an Embedded,
Compressed Header
5.3. Alternative: Include IPv6 in Header Format
An alternative to [I-D.ietf-schc-icmpv6-compression] is to continue
the compression process inside the ICMPv6 payload, instead of
matching it against a separate Rule. Figure 8 shows the resulting
Rule.
The invoking header's Field Descriptors are distinct from the outer
header's, and are designed from the ICMPv6 message's point of view.
Fields designed with an application or device role remain unchanged
(e.g. "ipv6-deviid" or "udp-app-port"), but the direction is
reversed. Field Position is also incremented if a field is repeated,
as for the IPv6 fields in the example.
The compression mechanism MUST also include the port numbers: an
ICMPv6 error message exists to inform the source that a given flow
failed to reach its destination, and the port numbers are part of
that flow's identification. It is RECOMMENDED to be able to fully
reconstruct the Layer 4 header this way, not just the ports.
+--------------+-----------+----+----+--------+--------+----------+
| Field | FL | FP | DI | TV | MO | CDA |
+--------------+-----------+----+----+--------+--------+----------+
+----------------------- Outer IPv6 header -----------------------+
| ipv6-version | 4 | 1 | Bi | 6 | equal | not-sent |
| ipv6- | 8 | 1 | Bi | 0 | ignore | not-sent |
| trafficclass | | | | | | |
| ipv6- | 20 | 1 | Bi | 0 | ignore | not-sent |
| flowlabel | | | | | | |
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| ipv6- | 16 | 1 | Bi | - | ignore | compute |
| payload- | | | | | | |
| length | | | | | | |
| ipv6- | 8 | 1 | Bi | 58 | equal | not-sent |
| nextheader | | | | | | |
| ipv6- | 8 | 1 | Up | - | ignore | value- |
| hoplimit | | | | | | sent |
| ipv6- | 8 | 1 | Dw | 1 | equal | not-sent |
| hoplimit | | | | | | |
| ipv6- | 64 | 1 | Bi | aaaa:: | equal | not-sent |
| devprefix | | | | | | |
| ipv6-deviid | 64 | 1 | Bi | ::zzzz | equal | not-sent |
| ipv6- | 64 | 1 | Bi | - | ignore | value- |
| appprefix | | | | | | sent |
| ipv6-appiid | 64 | 1 | Bi | - | ignore | value- |
| | | | | | | sent |
+------------------------- ICMPv6 header -------------------------+
| icmpv6-type | 8 | 1 | Bi | 1 | equal | not-sent |
| icmpv6-code | 8 | 1 | Bi | 4 | equal | not-sent |
| icmpv6- | 16 | 1 | Bi | 0 | ignore | compute |
| checksum | | | | | | |
| unused | 32 | 1 | Bi | 0 | ignore | not-sent |
+---------------- Invoking (embedded) IPv6 header ----------------+
| ipv6-version | 4 | 2 | Bi | 6 | equal | not-sent |
| ipv6- | 8 | 2 | Bi | 0 | ignore | not-sent |
| trafficclass | | | | | | |
| ipv6- | 20 | 2 | Bi | 0 | ignore | not-sent |
| flowlabel | | | | | | |
| ipv6- | 16 | 2 | Bi | - | ignore | compute |
| payload- | | | | | | |
| length | | | | | | |
| ipv6- | 8 | 2 | Bi | 17 | equal | not-sent |
| nextheader | | | | | | |
| ipv6- | 8 | 2 | Dw | 1 | equal | not-sent |
| hoplimit | | | | | | |
| ipv6- | 8 | 2 | Up | - | ignore | value- |
| hoplimit | | | | | | sent |
| ipv6- | 64 | 2 | Bi | aaaa:: | equal | not-sent |
| devprefix | | | | | | |
| ipv6-deviid | 64 | 2 | Bi | ::zzzz | equal | not-sent |
| ipv6- | 64 | 2 | Bi | - | ignore | value- |
| appprefix | | | | | | sent |
| ipv6-appiid | 64 | 2 | Bi | - | ignore | value- |
| | | | | | | sent |
+---------------- Invoking (embedded) UDP header -----------------+
| udp-dev-port | 16 | 1 | Bi | 5683 | equal | not-sent |
| udp-app-port | 16 | 1 | Bi | - | ignore | value- |
| | | | | | | sent |
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| udp-length | 16 | 1 | Bi | 0 | ignore | compute |
| udp-checksum | 16 | 1 | Bi | 0 | ignore | compute |
+--------------+-----------+----+----+--------+--------+----------+
| payload | remaining | 1 | Bi | - | ignore | not-sent |
+--------------+-----------+----+----+--------+--------+----------+
Figure 8: Alternative ICMPv6 Rule Embedding the Invoking IPv6/UDP
Header In Place
The compression result should be better, since there is no need to
send a variable-length residue and a second RuleID, at the cost of a
more complex Rule definition.
+----------+------------------------------------------+
| RuleID | IPv6/ICMPv6/IPv6/UDP residue |
+----------+------------------------------------------+
Figure 9: Residue Layout for the Alternative ICMPv6 Rule
6. Action
Selecting a compression Rule triggers compression and sends the
resulting SCHC Packet to the other end. [I-D.barthel-lpwan-oam-schc]
introduced an Action to change that behavior: the Rule is still
selected through its entries, but the packet description is handed
over to the process the Action names, instead of being sent to the
lower layer. Since the Rule is then used only for the selection, the
Compression/Decompression Actions of its entries do not matter and
are set to "not-sent".
The motivating example is an ICMPv6 [RFC4443] Echo Request sent to a
Device. The Device receives the compressed message and answers with
an Echo Reply, but propagating the Echo Request over the LPWAN costs
two messages on a constrained link, and the Identifier and Sequence
Number fields compress poorly when the sender is unaware of the
compression scheme. The Action "action-proxy-ping" avoids that
traffic: the core SCHC C/D answers the Echo Request on behalf of the
Device.
The Action takes a parameter, in seconds, giving the interval during
which the Device is considered active. During this interval, the
proxy echoes the ping requests; after it, they are discarded. The
parameter is carried in "action-value", a list reusing the Target
Value structure, so an Action may take several arguments.
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Figure 10 shows a compression Rule for pinging a Device, with the
entry-index column and the identity short names used in Figure 4.
The Action applies to the Rule as a whole, and is therefore shown
above its entries.
+--------------------------+
| Action: proxy-ping(300) |
+----+----------------+----+----+----+----+---------+----------+
| # | Field | FL | FP | DI | TV | MO | CDA |
+----+----------------+----+----+----+----+---------+----------+
| IPv6 Headers description (omitted) |
+----+----------------+----+----+----+----+---------+----------+
| 10 | icmpv6-type | 8 | 1 | Dw | 80 | equal | not-sent |
| 11 | icmpv6-code | 8 | 1 | Bi | 00 | equal | not-sent |
| 12 | icmpv6- | 16 | 1 | Bi | - | ignore | not-sent |
| | identifier | | | | | | |
| 13 | icmpv6- | 16 | 1 | Bi | 00 | MSB(24) | lsb |
| | sequence | | | | | | |
+----+----------------+----+----+----+----+---------+----------+
Figure 10: Example Compression Rule for a Ping to a Device
In the data model, the Action is added to the compression Rule
itself, as a sibling of its entries, and not to a single entry:
* "action": an identityref to "action-type", defaulting to "action-
forward". Being optional and defaulted, a Rule that does not
carry it behaves exactly as in RFC 8724 [RFC8724].
* "action-value": the Action's arguments, a list based on the Target
Value structure, as for Matching Operator and Compression/
Decompression Action arguments.
The corresponding new identities are:
* "action-base-type": base identity for the Action applied to a
packet matching a compression Rule.
* "action-forward": the default, where the packet is handed over to
the lower layer, as specified in RFC 8724 [RFC8724].
* "action-proxy-ping": the packet is processed locally by a ping
proxy, which answers the Echo Request on behalf of the Device.
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7. Compound ACK
RFC 9441 [RFC9441], "Static Context Header Compression (SCHC)
Compound Acknowledgement (ACK)", includes its own YANG module, "ietf-
schc-compound-ack", which augments the "ack-on-error" fragmentation
mode ("/schc/rule/nature/fragmentation/mode/ack-on-error") with two
new leaves. This document's module revision incorporates them:
* "bitmap-format": how bitmaps are carried in a SCHC ACK message: an
identityref to "bitmap-format-type", defaulting to "bitmap-
RFC8724".
* "last-bitmap-compression": a boolean, true by default, indicating
whether the last bitmap in a SCHC ACK message can be compressed.
The corresponding new identities are:
* "bitmap-format-base-type": base identity for how a bitmap is
formed in ACK messages.
* "bitmap-RFC8724": the default bitmap format, as already defined in
RFC 8724 [RFC8724].
* "bitmap-compound-ack": allows several bitmaps within a single ACK
message.
8. Rule Management
The SCHC YANG data model provides support for Rule management through
the "management" feature and the "nature-management" Rule nature. A
management Rule uses the compression Rule structure, but is kept
separate from regular compression Rules through the "nature-
management" Rule nature: IPv6 addresses and port numbers are
specially dedicated to identifying it, and MAY overlap with values
used by regular compression Rules; the nature of the Rule is what
allows distinguishing them. Management Rules are the only ones
allowed to access the Static Context, to read, create, update, or
delete Rules. Only the "entry-universal" structure supports
management Rules; the deprecated "entry" list does not.
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"guard-period", the management timer, is not really a property of any
single Rule: it applies to the SCHC context as a whole. Nesting it
inside "list rule" (whether inside one case or as a sibling of
"choice nature") would raise the same reachability problem "case
management" would have had, since it would need repeating, and re-
keying under SIDs, in every case that might need it. The revision
instead moves "guard-period" out of "list rule" entirely, into a new
top-level "context" container, a sibling of "schc", present only "if-
feature management". Being outside any Rule, it no longer needs a
"rule-nature"-based "must" at all.
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grouping compression-content-universal {
list entry-universal {
must "derived-from-or-self(../rule-nature,
'nature-compression') or
derived-from-or-self(../rule-nature,
'nature-management')" {
error-message
"Rule nature must be compression or management";
}
/* ... unchanged: key, ordered-by, uses, description ... */
}
/* ... action, action-value (Action section) ... */
}
container context {
if-feature "management";
uses management-content;
description
"Management-related parameters that apply to the whole SCHC
context rather than to a single Rule.";
}
list rule {
/* ... unchanged: key, rule-id-type, rule-nature ... */
choice nature {
case fragmentation {
if-feature "fragmentation";
uses fragmentation-content;
}
case compression {
/* ... unchanged, still deprecated ... */
}
case compression-universal {
if-feature "compression or management";
uses compression-content-universal;
}
}
}
Figure 11: Widening compression-universal to Also Serve
Management Rules (module revision 2026-09-22)
For management, a management context is added: its values are common
to all SCHC Rules in that management instance, rather than specific
to any one Rule. Currently, the context contains a guard period,
defining the time before a RuleID can be reused by management when a
new Rule is created.
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Different management operations can be defined to act on Rules or on
individual elements of a Rule. For example, the "duplicate-rule" RPC
can be used to create a new Rule from an existing one under a
different RuleID, with selected elements of the new Rule modified as
part of the operation.
This document defines the YANG structures needed to support Rule
management. The complete set of management operations -- their
semantics, encoding, exchange, and the procedures used to apply them
to a SCHC Context -- is specified separately.
9. Manual SID Allocation
The mapping between YANG identifiers and SID [RFC9595] values can be
generated automatically with the "pyang" tool (e.g. via "pyang --sid-
generate-file"). This automatic allocation, however, is not
optimized.
The first goal of a manual allocation is to minimize the delta
between SIDs used together as CBOR/CORECONF keys, so that delta
encodes on a single byte (i.e., a value between -24 and +23).
[I-D.toutain-schc-sid-allocation] shows that pyang's automatic,
alphabetical assignment defeats this: for example, "rule-id-value",
"rule-id-length", and "rule-nature", present in every Rule, end up
with a delta higher than 23 from their base, so every single Rule
pays for a 2-byte delta where a 1-byte one would do.
[I-D.toutain-schc-sid-allocation] makes two recommendations to keep
this delta small. First, keep data-carrying and identity-carrying
nodes in separate SID ranges, since they are rarely encoded together;
the distance between the two can then be as large as 255, allowing a
2-byte delta only where it does not matter. Second, leave some SIDs
unused around the SCHC Rule identifiers, so the module can be
augmented later (i.e. new leaves added) without pushing any of these
frequently co-occurring identifiers' deltas past the single-byte
threshold.
TODO: describe the resulting manual SID allocation mechanism: SIDs
are first generated automatically, then remapped to a stable,
manually curated allocation table (module, namespace, identifier) so
that previously published SIDs do not shift when the module evolves
(fields added, removed, or deprecated). Reference [RFC9595] for the
SID file format and describe the augmentation used to carry type
information per SID item.
The delta encoding above optimizes SIDs used as CBOR map keys, but
does nothing for a SID used as a value, for instance an identityref
leaf's value, such as a Rule entry's "matching-operator" or "comp-
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decomp-action". [I-D.toutain-core-private-sid-translation] addresses
this with a new Compression/Decompression Action, "cda-sid-
translation": it replaces such a SID value with a "private SID", a
small negative number, computed from the real SID, an "entry-point",
and an offset. It reports a worked IPv6/UDP/CoAP compression Rule
example where this reduces a 3994-byte file to 3057 bytes, a 23%
reduction.
With this technique, an identity's first 24 possible values (private
SIDs -1 to -24) each encode on a single byte -- valuable for the
identityref values used most intensively across a Rule, such as "mo-
equal", "mo-ignore", "cda-value-sent", and "cda-not-sent". The next
232 values (private SIDs -25 to -256) still encode on 2 bytes, an
improvement over an untranslated SID from the RFC SID range, which
always takes 3 bytes in the "ietf-schc" data model. Beyond that,
translation has no effect: the private SID also takes 3 bytes, same
as the original. Figure 12 summarizes this.
+------------------+------------+-------------+-----------+
| Private SID | Identities | Private SID | Plain SID |
| range | covered | bytes | bytes |
+------------------+------------+-------------+-----------+
| -1 to -24 | 24 | 1 | 3 |
| -25 to -256 | 232 | 2 | 3 |
| beyond -256 | -- | 3 | 3 |
+------------------+------------+-------------+-----------+
Figure 12: Private SID Encoding Size vs. Plain SID (RFC SID Range)
Beyond "entry_point + 256", a private SID can instead specify a
Rule's entry-index; beyond that, the remaining space is shared
between identity and data values, with no further reserved
distinction.
10. Security Considerations
TODO Security
11. IANA Considerations
TODO: register the (possibly updated) YANG module and namespace URI
with IANA, referencing this document instead of RFC 9363.
12. References
12.1. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/rfc/rfc7950>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC9595] Veillette, M., Ed., Pelov, A., Ed., Petrov, I., Ed.,
Bormann, C., and M. Richardson, "YANG Schema Item
iDentifier (YANG SID)", RFC 9595, DOI 10.17487/RFC9595,
July 2024, <https://www.rfc-editor.org/rfc/rfc9595>.
12.2. Informative References
[I-D.barthel-lpwan-oam-schc]
Barthel, D., Toutain, L., Kandasamy, A., Dujovne, D. R.,
and J. C. Zúñiga, "OAM for LPWAN using Static Context
Header Compression (SCHC)", Work in Progress, Internet-
Draft, draft-barthel-lpwan-oam-schc-05, 27 June 2023,
<https://datatracker.ietf.org/doc/html/draft-barthel-
lpwan-oam-schc-05>.
[I-D.ietf-core-oscore-key-update]
Höglund, R. and M. Tiloca, "Key Update for OSCORE
(KUDOS)", Work in Progress, Internet-Draft, draft-ietf-
core-oscore-key-update-14, 6 July 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-core-
oscore-key-update-14>.
[I-D.ietf-schc-8824-update]
Tiloca, M., Toutain, L., MartÃnez, I., and A. Minaburo,
"Static Context Header Compression (SCHC) for the
Constrained Application Protocol (CoAP)", Work in
Progress, Internet-Draft, draft-ietf-schc-8824-update-10,
26 July 2026, <https://datatracker.ietf.org/doc/html/
draft-ietf-schc-8824-update-10>.
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[I-D.ietf-schc-icmpv6-compression]
Barthel, D. and L. Toutain, "Static Context Header
Compression (SCHC) for the Internet Control Message
Protocol (ICMPv6)", Work in Progress, Internet-Draft,
draft-ietf-schc-icmpv6-compression-02, 13 June 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-schc-
icmpv6-compression-02>.
[I-D.ietf-schc-universal-option]
Lampin, Q., Minaburo, A., Tiloca, M., and L. Toutain,
"Options representation in SCHC YANG Data Models", Work in
Progress, Internet-Draft, draft-ietf-schc-universal-
option-01, 17 October 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-schc-
universal-option-01>.
[I-D.toutain-core-private-sid-translation]
Toutain, L., "Private SID Translation for CORECONF", Work
in Progress, Internet-Draft, draft-toutain-core-private-
sid-translation-00, 31 May 2026,
<https://datatracker.ietf.org/doc/html/draft-toutain-core-
private-sid-translation-00>.
[I-D.toutain-schc-sid-allocation]
Minaburo, A. and L. Toutain, "SCHC Sid Allocation", Work
in Progress, Internet-Draft, draft-toutain-schc-sid-
allocation-01, 7 July 2023,
<https://datatracker.ietf.org/doc/html/draft-toutain-schc-
sid-allocation-01>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/rfc/rfc4443>.
[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/rfc/rfc7252>.
[RFC7641] Hartke, K., "Observing Resources in the Constrained
Application Protocol (CoAP)", RFC 7641,
DOI 10.17487/RFC7641, September 2015,
<https://www.rfc-editor.org/rfc/rfc7641>.
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[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/rfc/rfc7959>.
[RFC7967] Bhattacharyya, A., Bandyopadhyay, S., Pal, A., and T.
Bose, "Constrained Application Protocol (CoAP) Option for
No Server Response", RFC 7967, DOI 10.17487/RFC7967,
August 2016, <https://www.rfc-editor.org/rfc/rfc7967>.
[RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
Documents Containing YANG Data Models", RFC 8407,
DOI 10.17487/RFC8407, October 2018,
<https://www.rfc-editor.org/rfc/rfc8407>.
[RFC8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments
(OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,
<https://www.rfc-editor.org/rfc/rfc8613>.
[RFC8724] Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and JC.
Zuniga, "SCHC: Generic Framework for Static Context Header
Compression and Fragmentation", RFC 8724,
DOI 10.17487/RFC8724, April 2020,
<https://www.rfc-editor.org/rfc/rfc8724>.
[RFC8824] Minaburo, A., Toutain, L., and R. Andreasen, "Static
Context Header Compression (SCHC) for the Constrained
Application Protocol (CoAP)", RFC 8824,
DOI 10.17487/RFC8824, June 2021,
<https://www.rfc-editor.org/rfc/rfc8824>.
[RFC9363] Minaburo, A. and L. Toutain, "A YANG Data Model for Static
Context Header Compression (SCHC)", RFC 9363,
DOI 10.17487/RFC9363, March 2023,
<https://www.rfc-editor.org/rfc/rfc9363>.
[RFC9441] Zúñiga, J., Gomez, C., Aguilar, S., Toutain, L., Céspedes,
S., and D. Wistuba, "Static Context Header Compression
(SCHC) Compound Acknowledgement (ACK)", RFC 9441,
DOI 10.17487/RFC9441, July 2023,
<https://www.rfc-editor.org/rfc/rfc9441>.
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Appendix A. Full YANG Module
Figure 13 shows the working copy of the "ietf-schc" module, kept up
to date with every change discussed in this document, taken from the
project's working file ("ietf-schc@2026-09-22.yang"), validated with
"pyang" (no errors; see the pre-existing RFC 8407 style findings
noted in its own revision history for remaining gaps).
<CODE BEGINS> file "ietf-schc@2026-09-22.yang"
module ietf-schc {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-schc";
prefix schc;
organization
"IETF IPv6 over Low Power Wide-Area Networks (lpwan) Working
Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/lpwan/about/>
WG List: <mailto:lp-wan@ietf.org>
Editor: Laurent Toutain
<mailto:laurent.toutain@imt-atlantique.fr>
Editor: Ana Minaburo
<mailto:ana@ackl.io>";
description
"Copyright (c) 2023 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Revised BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9363
(https://www.rfc-editor.org/info/rfc9363); see the RFC itself
for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
***************************************************************
Generic data model for the Static Context Header Compression
Rule for SCHC, based on RFCs 8724 and 8824. Including
compression, no-compression, and fragmentation Rules.
This module is a YANG data model for SCHC Rules (RFCs 8724 and
8824). RFC 8724 describes compression Rules in an abstract
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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 specifies a global data model that can be used for
Rule exchanges or modification. It specifies both the data
model format and the global identifiers used to describe some
operations in fields.
This data model applies to both compression and fragmentation.";
revision 2026-09-22 {
description
"Wire the 'nature-management' Rule nature into the data
model: widen 'compression-content-universal''s
'entry-universal' must to accept 'nature-compression' or
'nature-management', instead of adding a separate, SID-
duplicating 'case management' for an identical structure;
widen 'case compression-universal''s if-feature to
'compression or management' accordingly; and move
'management-content' (the 'guard-period' timer) out of
'list rule' into a new top-level 'context' container, gated
by 'if-feature management', since it applies to the whole
SCHC context rather than to a single Rule.";
}
revision 2026-08-20 {
description
"Add kudos FID defined in draft-ietf-core-oscore-key-update.
Restore the twenty per-CoAP-option FIDs (fid-coap-option-*)
that had been removed in an earlier revision, marking them
'status deprecated' instead of deleting them, per RFC 7950
Section 11 ('Obsolete definitions MUST NOT be removed from
published modules') and RFC 8407 Section 4.7 (an object
SHOULD stay 'deprecated' for at least one year before moving
to 'obsolete'). They are superseded by Universal Options
(space-id-coap / universal-value). Rename the '-v2'
compression-rule-entry/compression-content/case suffix to
'-universal'. Fix the space-id-coap identity description and
reference, mistakenly copy-pasted from fid-ipv6-*. Remove the
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unused fid-oscore-base-type identity: it was never used as a
base by any other identity (the OSCORE suboption FIDs derive
directly from fid-coap-option) and was never part of a
published RFC, so it can simply be dropped rather than
deprecated.";
}
revision 2026-05-07 {
description
"add two generic fid unused and payload to be used in any
protocol and for padding and payload definition.";
}
revision 2026-04-05 {
description
"Alternative: use choice/case to structurally distinguish regular
fields (field-id only) from universal options (space-id + mandatory
universal-value).";
}
revision 2026-02-24 {
description
"
- Add Management feature to support management of SCHC rules.
- Introduce RPCs to manage rules.";
}
revision 2026-01-12 {
description
"test module to unify universal option and regular entries:
- all options are identified with a space-id and an option-id.
For regular fields like fid-ipv6-version the space-id is set
to 0.
- the entries are identified by an index, reducing the keys to
a single element.
- introduction of a new function to define the length. This option
takes an entry-index as parameter to refer to a field indicating
length.
for instance fl-token-length is now equivalent to:
fl-length_byte(index) where index refers to an entry-index for
TKL field.";
}
revision 2025-11-24 {
description
"This version includes new developments in the SCHC architecture
and RFCs published since the initial version of this module.
It includes:
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* Data model for Compound Ack as described in RFC9441
* new Field IDs defined for CoAP OSCORE support as described
in draft-ietf-schc-8824-update.
* ICMPv6 FIDs defined in draft-ietf-schc-icmpv6.
* Universal options for CoAP and other protocols options parsing
as described in draft-ietf-schc-universal-options.
* the coap-option FIDs are deprecated in favor of the more generic
universal-option Field IDs.
";
reference
"RFC 9363 A YANG Data Model for Static Context Header
Compression (SCHC)
RFC 9441 Static Context Header Compression (SCHC)
Compound Acknowledgement (ACK)";
}
revision 2023-03-01 {
description
"Initial version from RFC 9363.";
reference
"RFC 9363 A YANG Data Model for Static Context Header
Compression (SCHC)";
}
feature compression {
description
"SCHC compression capabilities are taken into account.";
}
feature fragmentation {
description
"SCHC fragmentation capabilities are taken into account.";
}
feature management {
description
"SCHC compression capabilities for rule management.";
}
// -------------------------
// Field ID type definition
//--------------------------
// generic value TV definition
identity space-field-id-base-type {
description
"Field ID base type for all fields.";
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}
identity fid-base-type {
base space-field-id-base-type;
description
"Field ID base type for all fields.";
}
identity fid-unused {
base fid-base-type;
description
"Padding field in any protocol.";
}
identity fid-payload {
base fid-base-type;
description
"Payload field in any protocol. This field contains the remaining
bytes after the header fields.";
}
identity fid-ipv6-base-type {
base fid-base-type;
description
"Field ID base type for IPv6 headers described in RFC 8200.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
identity fid-ipv6-version {
base fid-ipv6-base-type;
description
"IPv6 version field.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
identity fid-ipv6-trafficclass {
base fid-ipv6-base-type;
description
"IPv6 Traffic Class field.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
identity fid-ipv6-trafficclass-ds {
base fid-ipv6-trafficclass;
description
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"IPv6 Traffic Class field: Diffserv field.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification,
RFC 3168 The Addition of Explicit Congestion Notification
(ECN) to IP";
}
identity fid-ipv6-trafficclass-ecn {
base fid-ipv6-trafficclass;
description
"IPv6 Traffic Class field: ECN field.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification,
RFC 3168 The Addition of Explicit Congestion Notification
(ECN) to IP";
}
identity fid-ipv6-flowlabel {
base fid-ipv6-base-type;
description
"IPv6 Flow Label field.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
identity fid-ipv6-payload-length {
base fid-ipv6-base-type;
description
"IPv6 Payload Length field.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
identity fid-ipv6-nextheader {
base fid-ipv6-base-type;
description
"IPv6 Next Header field.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
identity fid-ipv6-hoplimit {
base fid-ipv6-base-type;
description
"IPv6 Next Header field.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
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identity fid-ipv6-devprefix {
base fid-ipv6-base-type;
description
"Corresponds to either the source address or the destination
address prefix of RFC 8200 depending on whether it is an
uplink or a downlink message.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
identity fid-ipv6-deviid {
base fid-ipv6-base-type;
description
"Corresponds to either the source address or the destination
address IID of RFC 8200 depending on whether it is an uplink
or a downlink message.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
identity fid-ipv6-appprefix {
base fid-ipv6-base-type;
description
"Corresponds to either the source address or the destination
address prefix of RFC 8200 depending on whether it is an
uplink or a downlink message.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
identity fid-ipv6-appiid {
base fid-ipv6-base-type;
description
"Corresponds to either the source address or the destination
address IID of RFC 8200 depending on whether it is an uplink
or a downlink message.";
reference
"RFC 8200 Internet Protocol, Version 6 (IPv6) Specification";
}
identity fid-udp-base-type {
base fid-base-type;
description
"Field ID base type for UDP headers described in RFC 768.";
reference
"RFC 768 User Datagram Protocol";
}
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identity fid-udp-dev-port {
base fid-udp-base-type;
description
"UDP source or destination port, if uplink or downlink
communication, respectively.";
reference
"RFC 768 User Datagram Protocol";
}
identity fid-udp-app-port {
base fid-udp-base-type;
description
"UDP destination or source port, if uplink or downlink
communication, respectively.";
reference
"RFC 768 User Datagram Protocol";
}
identity fid-udp-length {
base fid-udp-base-type;
description
"UDP length.";
reference
"RFC 768 User Datagram Protocol";
}
identity fid-udp-checksum {
base fid-udp-base-type;
description
"UDP length.";
reference
"RFC 768 User Datagram Protocol";
}
identity fid-coap-base-type {
base fid-base-type;
description
"Field ID base type for UDP headers described.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-version {
base fid-coap-base-type;
description
"CoAP version.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
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}
identity fid-coap-type {
base fid-coap-base-type;
description
"CoAP type.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-tkl {
base fid-coap-base-type;
description
"CoAP token length.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-code {
base fid-coap-base-type;
description
"CoAP code.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-code-class {
base fid-coap-code;
description
"CoAP code class.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-code-detail {
base fid-coap-code;
description
"CoAP code detail.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-mid {
base fid-coap-base-type;
description
"CoAP message ID.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
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}
identity fid-coap-token {
base fid-coap-base-type;
description
"CoAP token.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option {
base fid-coap-base-type;
description
"Generic CoAP option.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-if-match {
base fid-coap-option;
status deprecated;
description
"CoAP option If-Match. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 1).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-uri-host {
base fid-coap-option;
status deprecated;
description
"CoAP option Uri-Host. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 3).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-etag {
base fid-coap-option;
status deprecated;
description
"CoAP option ETag. Deprecated in favor of Universal Options
(space-id-coap / universal-value = 4).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
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identity fid-coap-option-if-none-match {
base fid-coap-option;
status deprecated;
description
"CoAP option if-none-match. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 5).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-observe {
base fid-coap-option;
status deprecated;
description
"CoAP option Observe. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 6).";
reference
"RFC 7641 Observing Resources in the Constrained Application
Protocol (CoAP)";
}
identity fid-coap-option-uri-port {
base fid-coap-option;
status deprecated;
description
"CoAP option Uri-Port. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 7).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-location-path {
base fid-coap-option;
status deprecated;
description
"CoAP option Location-Path. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 8).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-uri-path {
base fid-coap-option;
status deprecated;
description
"CoAP option Uri-Path. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 11).";
reference
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"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-content-format {
base fid-coap-option;
status deprecated;
description
"CoAP option Content Format. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 12).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-max-age {
base fid-coap-option;
status deprecated;
description
"CoAP option Max-Age. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 14).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-uri-query {
base fid-coap-option;
status deprecated;
description
"CoAP option Uri-Query. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 15).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-accept {
base fid-coap-option;
status deprecated;
description
"CoAP option Accept. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 17).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-location-query {
base fid-coap-option;
status deprecated;
description
"CoAP option Location-Query. Deprecated in favor of Universal
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Options (space-id-coap / universal-value = 20).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-block2 {
base fid-coap-option;
status deprecated;
description
"CoAP option Block2. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 23).";
reference
"RFC 7959 Block-Wise Transfers in the Constrained Application
Protocol (CoAP)";
}
identity fid-coap-option-block1 {
base fid-coap-option;
status deprecated;
description
"CoAP option Block1. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 27).";
reference
"RFC 7959 Block-Wise Transfers in the Constrained Application
Protocol (CoAP)";
}
identity fid-coap-option-size2 {
base fid-coap-option;
status deprecated;
description
"CoAP option Size2. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 28).";
reference
"RFC 7959 Block-Wise Transfers in the Constrained Application
Protocol (CoAP)";
}
identity fid-coap-option-proxy-uri {
base fid-coap-option;
status deprecated;
description
"CoAP option Proxy-Uri. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 35).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
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identity fid-coap-option-proxy-scheme {
base fid-coap-option;
status deprecated;
description
"CoAP option Proxy-Scheme. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 39).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-size1 {
base fid-coap-option;
status deprecated;
description
"CoAP option Size1. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 60).";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
identity fid-coap-option-no-response {
base fid-coap-option;
status deprecated;
description
"CoAP option No response. Deprecated in favor of Universal
Options (space-id-coap / universal-value = 258).";
reference
"RFC 7967 Constrained Application Protocol (CoAP) Option for
No Server Response";
}
identity fid-coap-option-oscore-flags {
base fid-coap-option;
description
"CoAP option OSCORE flags.";
reference
"RFC 8824 Static Context Header Compression (SCHC) for the
Constrained Application Protocol (CoAP) (see
Section 6.4)";
}
identity fid-coap-option-oscore-flags-flagbits {
base fid-coap-option-oscore-flags;
description
"First 5 bits of the OSCORE flags field forming flags subfield.";
reference
"RFC 8824 Static Context Header Compression (SCHC) for the
Constrained Application Protocol (CoAP) (see
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Section 6.4)";
}
identity fid-coap-option-oscore-flags-n {
base fid-coap-option-oscore-flags;
description
"last 3 bits of the OSCORE flags field giving the length
of Partial IV.";
reference
"RFC 8824 Static Context Header Compression (SCHC) for the
Constrained Application Protocol (CoAP) (see
Section 6.4)";
}
identity fid-coap-option-oscore-piv {
base fid-coap-option;
description
"CoAP option OSCORE Partial IV.";
reference
"RFC 8824 Static Context Header Compression (SCHC) for the
Constrained Application Protocol (CoAP) (see
Section 6.4)";
}
identity fid-coap-option-oscore-kid {
base fid-coap-option;
description
"CoAP option OSCORE Key ID.";
reference
"RFC 8824 Static Context Header Compression (SCHC) for the
Constrained Application Protocol (CoAP) (see
Section 6.4)";
}
identity fid-coap-option-oscore-kidctx {
base fid-coap-option;
description
"CoAP option OSCORE Key ID Context.";
reference
"RFC 8824 Static Context Header Compression (SCHC) for the
Constrained Application Protocol (CoAP)(see
Section 6.4)";
}
identity fid-coap-option-kudos-x {
base fid-coap-option;
description
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"x field contained in the kudos option defined in
draft-ietf-core-oscore-key-update.";
reference
"draft-ietf-core-oscore-key-update";
}
identity fid-coap-option-kudos-x-flagbits {
base fid-coap-option-kudos-x;
description
"4 first bits of the x field in the kudos option defined in
draft-ietf-core-oscore-key-update.";
reference
"draft-ietf-core-oscore-key-update";
}
identity fid-coap-option-kudos-x-m {
base fid-coap-option-kudos-x;
description
"4 last bits of the x field in the kudos option defined in
draft-ietf-core-oscore-key-update.";
reference
"draft-ietf-core-oscore-key-update";
}
identity fid-coap-option-kudos-nonce {
base fid-coap-option;
description
"CoAP option kudos carrying the nonce.";
reference
"draft-ietf-core-oscore-key-update";
}
identity fid-icmpv6-base-type {
base schc:fid-base-type;
description
"Field IP base type for ICMPv6 headers described in RFC 4443";
reference
"RFC 4443 Internet Control Message Protocol (ICMPv6)
for the Internet Protocol Version 6 (IPv6)
Specification";
}
identity fid-icmpv6-type {
base fid-icmpv6-base-type;
description
"ICMPv6 code field present in all ICMPv6 messages.";
}
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identity fid-icmpv6-code {
base fid-icmpv6-base-type;
description
"ICMPv6 code field present in all ICMPv6 messages.";
}
identity fid-icmpv6-checksum {
base fid-icmpv6-base-type;
description
"ICMPv6 checksum field present in all ICMPv6 messages.";
}
identity fid-icmpv6-mtu {
base fid-icmpv6-base-type;
description
"ICMPv6 MTU, present in Packet Too Big message.";
}
identity fid-icmpv6-pointer {
base fid-icmpv6-base-type;
description
"ICMPv6 Pointer, present in Parameter Problem message.";
}
identity fid-icmpv6-identifier {
base fid-icmpv6-base-type;
description
"ICMPv6 identifier field, present in Echo Request/Reply
message.";
}
identity fid-icmpv6-sequence {
base fid-icmpv6-base-type;
description
"ICMPv6 sequence number field, present in Echo Request/Reply
message.";
}
identity fid-icmpv6-payload {
base fid-icmpv6-base-type;
description
"ICMPv6 payload following ICMPv6 header.
If payload is empty, this field exists with a length of 0.";
}
//----------------------------------
// Universal Option space IDs
//----------------------------------
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identity space-id-base-type {
base schc:space-field-id-base-type;
description
"Base identity for a Universal Option space. Several
protocols define options (e.g. CoAP); each such protocol
is identified by an identity derived from this base type.";
}
identity space-id-coap {
base space-id-base-type;
description
"Space ID identifying the CoAP option space.";
reference
"RFC 7252 The Constrained Application Protocol (CoAP)";
}
//----------------------------------
// Field Length type definition
//----------------------------------
identity fl-base-type {
description
"Used to extend Field Length functions.";
}
identity fl-variable {
base fl-base-type;
description
"Residue length in bytes is sent as defined for CoAP.";
reference
"RFC 8824 Static Context Header Compression (SCHC) for the
Constrained Application Protocol (CoAP) (see
Section 5.3)";
}
identity fl-variable-bits {
base fl-base-type;
description
"Residue length in bits is sent as defined for CoAP.";
reference
"NOT YET DEFINED IN RFCs. This function is a generalization of fl-variable to support bit-level length definition.";
}
identity fl-token-length {
base fl-base-type;
description
"Residue length in bytes is sent as defined for CoAP.";
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reference
"RFC 8824 Static Context Header Compression (SCHC) for the
Constrained Application Protocol (CoAP) (see
Section 4.5)";
}
identity fl-length-bytes {
base fl-base-type;
description "This function return the length a field
by its index in bytes. This is a generalation of fl-token-length.";
}
identity fl-length-bits {
base fl-base-type;
description "This function return the length in bits of a field
by its index in bits. ";
}
identity fl-remaining {
base fl-base-type;
description
"Field length is not explicitly carried in the Compression Residue.
This function is used for a field that extends to the end of the
SCHC packet, such as a trailing payload.";
}
//---------------------------------
// Direction Indicator type
//---------------------------------
identity di-base-type {
description
"Used to extend Direction Indicators.";
}
identity di-bidirectional {
base di-base-type;
description
"Direction Indicator of bidirectionality.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.1)";
}
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identity di-up {
base di-base-type;
description
"Direction Indicator of uplink.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.1)";
}
identity di-down {
base di-base-type;
description
"Direction Indicator of downlink.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.1)";
}
//----------------------------------
// Matching Operator type definition
//----------------------------------
identity mo-base-type {
description
"Matching Operator: used in the Rule selection process
to check if a Target Value matches the field's value.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.2)";
}
identity mo-equal {
base mo-base-type;
description
"equal MO.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.3)";
}
identity mo-ignore {
base mo-base-type;
description
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"ignore MO.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.3)";
}
identity mo-msb {
base mo-base-type;
description
"MSB MO.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.3)";
}
identity mo-match-mapping {
base mo-base-type;
description
"match-mapping MO.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.3)";
}
identity mo-rule-match {
base schc:mo-base-type;
description
"Macthing operator return true, if the TV matches a rule
keeping UP and DOWN direction.";
}
identity mo-rev-rule-match {
base schc:mo-base-type;
description
"Macthing operator return true, if the TV matches a rule
reversing UP and DOWN direction.";
}
//------------------------------
// CDA type definition
//------------------------------
identity cda-base-type {
description
"Compression Decompression Actions. Specify the action to
be applied to the field's value in a specific Rule.";
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reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.2)";
}
identity cda-not-sent {
base cda-base-type;
description
"not-sent CDA.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.4)";
}
identity cda-value-sent {
base cda-base-type;
description
"value-sent CDA.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.4)";
}
identity cda-lsb {
base cda-base-type;
description
"Least Significant Bit (LSB) CDA.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.4)";
}
identity cda-mapping-sent {
base cda-base-type;
description
"mapping-sent CDA.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.4)";
}
identity cda-compute {
base cda-base-type;
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description
"compute-* CDA.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.4)";
}
identity cda-deviid {
base cda-base-type;
description
"DevIID CDA.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.4)";
}
identity cda-appiid {
base cda-base-type;
description
"Application Interface Identifier (AppIID) CDA.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context
Header Compression and Fragmentation (see
Section 7.4)";
}
identity cda-compress-sent {
base schc:cda-base-type;
description
"Send a compressed version of TV keeping UP and
DOWN direction.";
}
identity cda-rev-compress-sent {
base schc:cda-base-type;
description
"Send a compressed version of TV reversing UP and
DOWN direction.";
}
// -- type definition
typedef space-field-id-type {
type identityref {
base space-field-id-base-type;
}
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description
"Field ID generic type.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
typedef fid-type {
type identityref {
base fid-base-type;
}
description
"Field ID type for regular protocol fields (IPv6, UDP, CoAP, etc.).
Used in the regular-field case of compression-rule-entry.";
}
typedef space-id-type {
type identityref {
base space-id-base-type;
}
description
"Space ID type for universal option spaces (CoAP options, etc.).
Used in the universal-option case of compression-rule-entry.";
}
typedef fl-type {
type identityref {
base fl-base-type;
}
description
"Function used to indicate Field Length.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
typedef di-type {
type identityref {
base di-base-type;
}
description
"Direction in LPWAN network: up when emitted by the device,
down when received by the device, or bi when emitted or
received by the device.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
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typedef mo-type {
type identityref {
base mo-base-type;
}
description
"Matching Operator (MO) to compare field values with
Target Values.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
typedef cda-type {
type identityref {
base cda-base-type;
}
description
"Compression Decompression Action to compress or
decompress a field.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
// -- FRAGMENTATION TYPE
// -- fragmentation modes
identity fragmentation-mode-base-type {
description
"Define the fragmentation mode.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
identity fragmentation-mode-no-ack {
base fragmentation-mode-base-type;
description
"No-ACK mode.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
identity fragmentation-mode-ack-always {
base fragmentation-mode-base-type;
description
"ACK-Always mode.";
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reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
identity fragmentation-mode-ack-on-error {
base fragmentation-mode-base-type;
description
"ACK-on-Error mode.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
typedef fragmentation-mode-type {
type identityref {
base fragmentation-mode-base-type;
}
description
"Define the type used for fragmentation mode in Rules.";
}
// -- Ack behavior
identity ack-behavior-base-type {
description
"Define when to send an Acknowledgment.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
identity ack-behavior-after-all-0 {
base ack-behavior-base-type;
description
"Fragmentation expects ACK after sending All-0 fragment.";
}
identity ack-behavior-after-all-1 {
base ack-behavior-base-type;
description
"Fragmentation expects ACK after sending All-1 fragment.";
}
identity ack-behavior-by-layer2 {
base ack-behavior-base-type;
description
"Layer 2 defines when to send an ACK.";
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}
typedef ack-behavior-type {
type identityref {
base ack-behavior-base-type;
}
description
"Define the type used for ACK behavior in Rules.";
}
// -- All-1 with data types
identity all-1-data-base-type {
description
"Type to define when to send an Acknowledgment message.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
identity all-1-data-no {
base all-1-data-base-type;
description
"All-1 contains no tiles.";
}
identity all-1-data-yes {
base all-1-data-base-type;
description
"All-1 MUST contain a tile.";
}
identity all-1-data-sender-choice {
base all-1-data-base-type;
description
"Fragmentation process chooses to send tiles or not in All-1.";
}
typedef all-1-data-type {
type identityref {
base all-1-data-base-type;
}
description
"Define the type used for All-1 format in Rules.";
}
// -- RCS algorithm types
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identity rcs-algorithm-base-type {
description
"Identify which algorithm is used to compute RCS.
The algorithm also defines the size of the RCS field.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
identity rcs-crc32 {
base rcs-algorithm-base-type;
description
"CRC32 defined as default RCS in RFC 8724. This RCS is
4 bytes long.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
typedef rcs-algorithm-type {
type identityref {
base rcs-algorithm-base-type;
}
description
"Define the type for RCS algorithm in Rules.";
}
// --------- COMPOUND ACK TYPE DEFINITION ---------
identity bitmap-format-base-type {
description
"Define how the bitmap is formed in ACK messages. ";
reference
"RFC9441 Static Context Header Compression (SCHC)
Compound Acknowledgement (ACK)";
}
identity bitmap-RFC8724 {
base bitmap-format-base-type;
description
"Bitmap by default as defined in RFC 8724.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation.
RFC9441 Static Context Header Compression (SCHC)
Compound Acknowledgement (ACK)";
}
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identity bitmap-compound-ack {
base bitmap-format-base-type;
description
"Compound ACK allows several bitmaps in an ACK message.";
reference
"RFC9441 Static Context Header Compression (SCHC)
Compound Acknowledgement (ACK)"; }
typedef bitmap-format-type {
type identityref {
base bitmap-format-base-type;
}
description
"Type of bitmap used in Rules.";
reference
"RFC9441 Static Context Header Compression (SCHC)
Compound Acknowledgement (ACK)";
}
// -------- RULE ENTRY DEFINITION ------------
grouping tv-struct {
description
"Defines the Target Value element. If the header field
contains a text, the binary sequence uses the same encoding.
field-id allows the conversion to the appropriate type.";
leaf index {
type uint16;
description
"Index gives the position in the matching list. If only one
element is present, index is 0. Otherwise, index is the
order in the matching list, starting at 0.";
}
leaf value {
type binary;
description
"Target Value content as an untyped binary value.";
}
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
grouping compression-rule-entry {
status deprecated;
description
"These entries define a compression entry (i.e., a line),
as defined in RFC 8724.
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+-------+--+--+--+------------+-----------------+---------------+
|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
- Field Length : either a positive integer or a function
- Field Position: a positive (and possibly equal to 0)
integer
- Direction Indicator: an indication in which direction the
compression and decompression process is effective
- Target Value: a value against which the header field is
compared
- Matching Operator: the comparison operation and optional
associate parameters
- Comp./Decomp. Action: the compression or decompression
action and optional parameters
Deprecated in favor of 'compression-rule-entry-universal', which
adds support for Universal Options.";
reference
"RFC 9363 A YANG Data Model for Static Context Header
Compression (SCHC)";
leaf field-id {
type schc:fid-type;
mandatory true;
description
"Field ID, identify a field in the header with a YANG
identity reference.";
}
leaf field-length {
type union {
type uint8;
type schc:fl-type;
}
mandatory true;
description
"Field Length, expressed in number of bits if the length is
known when the Rule is created or through a specific
function if the length is variable.";
}
leaf field-position {
type uint8;
mandatory true;
description
"Field Position in the header is an integer. Position 1
matches the first occurrence of a field in the header,
while incremented position values match subsequent
occurrences.
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Position 0 means that this entry matches a field
irrespective of its position of occurrence in the
header.
Be aware that the decompressed header may have
position-0 fields ordered differently than they
appeared in the original packet.";
}
leaf direction-indicator {
type schc:di-type;
mandatory true;
description
"Direction Indicator, indicate if this field must be
considered for Rule selection or ignored based on the
direction (bidirectional, only uplink, or only
downlink).";
}
list target-value {
key "index";
uses tv-struct;
description
"A list of values to compare with the header field value.
If Target Value is a singleton, position must be 0.
For use as a matching list for the mo-match-mapping Matching
Operator, index should take consecutive values starting
from 0.";
}
leaf matching-operator {
type schc:mo-type;
must "../target-value or derived-from-or-self(.,
'mo-ignore')" {
error-message
"mo-equal, mo-msb, and mo-match-mapping need target-value";
description
"target-value is not required for mo-ignore.";
}
must "not (derived-from-or-self(., 'mo-msb')) or
../matching-operator-value" {
error-message "mo-msb requires length value";
}
mandatory true;
description
"MO: Matching Operator.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation (see Section 7.3)";
}
list matching-operator-value {
key "index";
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uses tv-struct;
description
"Matching Operator Arguments, based on TV structure to allow
several arguments.
In RFC 8724, only the MSB Matching Operator needs arguments
(a single argument, which is the number of most significant
bits to be matched).";
}
leaf comp-decomp-action {
type schc:cda-type;
must "../target-value or
derived-from-or-self(., 'cda-value-sent') or
derived-from-or-self(., 'cda-compute') or
derived-from-or-self(., 'cda-appiid') or
derived-from-or-self(., 'cda-deviid')" {
error-message
"cda-not-sent, cda-lsb, and cda-mapping-sent need
target-value";
description
"target-value is not required for some CDA.";
}
mandatory true;
description
"CDA: Compression Decompression Action.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation (see Section 7.4)";
}
list comp-decomp-action-value {
key "index";
uses tv-struct;
description
"CDA arguments, based on a TV structure, in order to allow
for several arguments. The CDAs specified in RFC 8724
require no argument.";
}
}
grouping compression-rule-entry-universal {
description
"These entries define a compression entry (i.e., a line),
as defined in RFC 8724. The format has been generalized
to include universal options.
An entry in a compression Rule is composed of 7 elements:
- entry-index: position in the rule.
- space field ID: the identityref of a specific field or
space ID followed by an universal value.
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- universal-value: the value associated to the space field ID to identify
a specific field in the space. For regular fields, this
value is 0 and the space field ID is the field ID. For
universal options, the space field ID identifies the type
of option and the universal value identifies the specific
option.
- Field Length : either a positive integer or a function
- Field Position: a positive (and possibly equal to 0)
integer
- Direction Indicator: an indication in which direction the
compression and decompression process is effective
- Target Value: a value against which the header field is
compared
- Matching Operator: the comparison operation and optional
associate parameters
- Comp./Decomp. Action: the compression or decompression
action and optional parameters
";
leaf entry-index {
type uint16;
description
"Sequential position of the entry in the user-ordered Rule list.";
}
choice field-or-space {
mandatory true;
description
"Distinguishes a regular protocol field from a universal option.
Exactly one case must be present:
- regular-field: a standard protocol field identified by a field ID
(e.g., fid-ipv6-version, fid-udp-dev-port).
- universal-option: a generic option identified by a space ID
(e.g., space-id-coap) plus a numeric option value (e.g., the
CoAP option number).";
case regular-field {
description
"The entry refers to a regular protocol field.
No universal-value is needed.";
leaf field-id {
type schc:fid-type;
mandatory true;
description
"Field ID of a regular protocol field.";
}
}
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case universal-option {
description
"The entry refers to a universal option within a given space.
Both space-id and universal-value are required.";
leaf space-id {
type schc:space-id-type;
mandatory true;
description
"Space ID identifying the protocol option space
(e.g., space-id-coap for CoAP options).";
}
leaf universal-value {
type uint64;
mandatory true;
description
"Numeric value identifying the specific option within the space
(e.g., the CoAP option number).";
}
} // case universal-option
} // choice field-or-space
leaf field-length {
type union {
type uint8;
type schc:fl-type;
}
mandatory true;
description
"Field Length, expressed in number of bits if the length is
known when the Rule is created or through a specific
function if the length is variable.";
}
leaf field-length-value {
type uint16;
description
"Argument used by Field Length functions. For
fl-length-bytes and fl-length-bits, this value is the
entry-index of the Rule entry whose numerical field value
specifies the length.";
}
leaf field-position {
type uint8;
mandatory true;
description
"Field Position in the header is an integer. Position 1
matches the first occurrence of a field in the header,
while incremented position values match subsequent
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occurrences.
Position 0 means that this entry matches a field
irrespective of its position of occurrence in the
header.
Be aware that the decompressed header may have
position-0 fields ordered differently than they
appeared in the original packet.";
}
leaf direction-indicator {
type schc:di-type;
mandatory true;
description
"Direction Indicator, indicate if this field must be
considered for Rule selection or ignored based on the
direction (bidirectional, only uplink, or only
downlink).";
}
list target-value {
key "index";
uses tv-struct;
description
"A list of values to compare with the header field value.
If Target Value is a singleton, position must be 0.
For use as a matching list for the mo-match-mapping Matching
Operator, index should take consecutive values starting
from 0.";
}
leaf matching-operator {
type schc:mo-type;
must "../target-value or derived-from-or-self(.,
'mo-ignore')" {
error-message
"mo-equal, mo-msb, and mo-match-mapping need target-value";
description
"target-value is not required for mo-ignore.";
}
must "not (derived-from-or-self(., 'mo-msb')) or
../matching-operator-value" {
error-message "mo-msb requires length value";
}
mandatory true;
description
"MO: Matching Operator.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation (see Section 7.3)";
}
list matching-operator-value {
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key "index";
uses tv-struct;
description
"Matching Operator Arguments, based on TV structure to allow
several arguments.
In RFC 8724, only the MSB Matching Operator needs arguments
(a single argument, which is the number of most significant
bits to be matched).";
}
leaf comp-decomp-action {
type schc:cda-type;
must "../target-value or
derived-from-or-self(., 'cda-value-sent') or
derived-from-or-self(., 'cda-compute') or
derived-from-or-self(., 'cda-appiid') or
derived-from-or-self(., 'cda-deviid')" {
error-message
"cda-not-sent, cda-lsb, and cda-mapping-sent need
target-value";
description
"target-value is not required for some CDA.";
}
mandatory true;
description
"CDA: Compression Decompression Action.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation (see Section 7.4)";
}
list comp-decomp-action-value {
key "index";
uses tv-struct;
description
"CDA arguments, based on a TV structure, in order to allow
for several arguments. The CDAs specified in RFC 8724
require no argument.";
}
}
// --Rule nature
identity nature-base-type {
description
"A Rule, identified by its RuleID, is used for a single
purpose. RFC 8724 defines 3 natures:
compression, no-compression, and fragmentation.";
reference
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"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation (see Section 6)";
}
identity nature-compression {
base nature-base-type;
description
"Identify a compression Rule.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation (see Section 6)";
}
identity nature-no-compression {
base nature-base-type;
description
"Identify a no-compression Rule.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation (see Section 6)";
}
identity nature-fragmentation {
base nature-base-type;
description
"Identify a fragmentation Rule.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation (see Section 6)";
}
typedef nature-type {
type identityref {
base nature-base-type;
}
description
"Defines the type to indicate the nature of the Rule.";
}
identity nature-management {
base nature-base-type;
description
"Identify a management Rule. Management Rules use the
compression Rule structure to operate on the SCHC Context.";
/* Reference to be added when the Rule Management specification
is available. */
}
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identity action-base-type {
description
"Action applied to a packet matching a compression Rule, once
compression has been performed (or before decompression is
performed in the other direction). The default behavior of
RFC 8724 is to hand the SCHC Packet over to the lower layer;
other actions allow an intermediate entity, typically the
SCHC gateway, to process the packet locally instead.";
reference
"draft-barthel-lpwan-oam-schc-05 OAM for LPWAN using Static
Context Header Compression (SCHC) (see Section 5)";
}
identity action-forward {
base action-base-type;
description
"The packet is handed over to the lower layer. This is the
default behavior specified in RFC 8724.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
identity action-proxy-ping {
base action-base-type;
description
"The packet is not handed over to the lower layer but
processed locally by a ping proxy, which answers the ICMPv6
Echo Request on behalf of the Device.";
reference
"draft-barthel-lpwan-oam-schc-05 OAM for LPWAN using Static
Context Header Compression (SCHC) (see Section 5)";
}
typedef action-type {
type identityref {
base action-base-type;
}
description
"Defines the type to indicate the action associated with a
compression Rule.";
}
grouping compression-content {
status deprecated;
list entry {
status deprecated;
must "derived-from-or-self(../rule-nature,
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'nature-compression')" {
error-message "Rule nature must be compression";
}
key "field-id field-position direction-indicator";
uses compression-rule-entry {
status deprecated;
}
description
"A compression Rule is a list of Rule entries, each
describing a header field. An entry is identified
through a field-id, its position in the packet, and
its direction.";
}
description
"Define a compression Rule composed of a list of entries.
Deprecated in favor of 'compression-content-universal', which
adds support for Universal Options.";
reference
"RFC 9363 A YANG Data Model for Static Context Header
Compression (SCHC)";
}
grouping compression-content-universal {
list entry-universal {
must "derived-from-or-self(../rule-nature,
'nature-compression') or
derived-from-or-self(../rule-nature,
'nature-management')" {
error-message
"Rule nature must be compression or management";
}
key "entry-index";
ordered-by user;
uses compression-rule-entry-universal;
description
"A compression Rule is a list of Rule entries, each
describing a header field or Universal Option. An entry
is identified by its entry-index.";
}
leaf action {
type action-type;
default "schc:action-forward";
description
"Action to be applied to a packet matching this Rule, after
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compression or before decompression. When absent, the
packet is sent to the lower layer as specified in
RFC 8724.";
}
list action-value {
key "index";
uses tv-struct;
description
"Parameters associated with the action, based on a TV
structure, in order to allow for several arguments.
'action-forward' requires no argument.";
}
description
"Define a compression Rule composed of a list of entries,
using the Universal-Option-aware 'compression-rule-entry-universal'.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
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 fragmentation-mode {
type schc:fragmentation-mode-type;
must "derived-from-or-self(../rule-nature,
'nature-fragmentation')" {
error-message "Rule nature must be fragmentation";
}
mandatory true;
description
"Which fragmentation mode is used (No ACK, ACK Always, or
ACK on Error).";
}
leaf l2-word-size {
type uint8;
default "8";
description
"Size, in bits, of the Layer 2 Word.";
}
leaf direction {
type schc:di-type;
must "derived-from-or-self(., 'di-up') or
derived-from-or-self(., 'di-down')" {
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error-message
"Direction for fragmentation Rules are up or down.";
}
mandatory true;
description
"MUST be up or down, bidirectional MUST NOT be used.";
}
// SCHC Frag header format
leaf dtag-size {
type uint8;
default "0";
description
"Size, in bits, of the DTag field (T variable from
RFC 8724).";
}
leaf w-size {
when "derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-on-error')
or
derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-always') ";
type uint8;
description
"Size, in bits, of the window field (M variable from
RFC 8724).";
}
leaf fcn-size {
type uint8;
mandatory true;
description
"Size, in bits, of the FCN field (N variable from
RFC 8724).";
}
leaf rcs-algorithm {
type rcs-algorithm-type;
default "schc:rcs-crc32";
description
"Algorithm used for RCS. The algorithm specifies the RCS
size.";
}
// SCHC fragmentation protocol parameters
leaf maximum-packet-size {
type uint16;
default "1280";
description
"When decompression is done, packet size must not
strictly exceed this limit, expressed in bytes.";
}
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leaf window-size {
type uint16;
description
"By default, if not specified, the FCN value is 2^w-size - 1.
This value should not be exceeded. Possible FCN values
are between 0 and window-size - 1.";
}
leaf max-interleaved-frames {
type uint8;
default "1";
description
"Maximum of simultaneously fragmented frames. Maximum value
is 2^dtag-size. All DTag values can be used, but more than
max-interleaved-frames MUST NOT be active at any time.";
}
container inactivity-timer {
leaf ticks-duration {
type uint8;
default "20";
description
"Duration of one tick in microseconds:
2^ticks-duration/10^6 = 1.048s.";
}
leaf ticks-numbers {
type uint16 {
range "0..max";
}
description
"Timer duration = ticks-numbers*2^ticks-duration / 10^6.";
}
description
"Duration in seconds of the Inactivity Timer; 0 indicates
that the timer is disabled.
Allows a precision from microsecond to year by sending the
tick-duration value. For instance:
tick-duration: smallest value <-> highest value
20: 00y 000d 00h 00m 01s.048575<->00y 000d 19h 05m 18s.428159
21: 00y 000d 00h 00m 02s.097151<->00y 001d 14h 10m 36s.856319
22: 00y 000d 00h 00m 04s.194303<->00y 003d 04h 21m 13s.712639
23: 00y 000d 00h 00m 08s.388607<->00y 006d 08h 42m 27s.425279
24: 00y 000d 00h 00m 16s.777215<->00y 012d 17h 24m 54s.850559
25: 00y 000d 00h 00m 33s.554431<->00y 025d 10h 49m 49s.701119
Note that the smallest value is also the incrementation
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step.";
}
container retransmission-timer {
leaf ticks-duration {
type uint8;
default "20";
description
"Duration of one tick in microseconds:
2^ticks-duration/10^6 = 1.048s.";
}
leaf ticks-numbers {
type uint16 {
range "1..max";
}
description
"Timer duration = ticks-numbers*2^ticks-duration / 10^6.";
}
when "derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-on-error')
or
derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-always') ";
description
"Duration in seconds of the Retransmission Timer.
See the Inactivity Timer.";
}
leaf max-ack-requests {
when "derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-on-error')
or
derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-always') ";
type uint8 {
range "1..max";
}
description
"The maximum number of retries for a specific SCHC ACK.";
}
choice mode {
case no-ack;
case ack-always;
case ack-on-error {
leaf tile-size {
when "derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-on-error')";
type uint8;
description
"Size, in bits, of tiles. If not specified or set to 0,
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tiles fill the fragment.";
}
leaf tile-in-all-1 {
when "derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-on-error')";
type schc:all-1-data-type;
description
"Defines whether the sender and receiver expect a tile in
All-1 fragments or not, or if it is left to the sender's
choice.";
}
leaf ack-behavior {
when "derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-on-error')";
type schc:ack-behavior-type;
description
"Sender behavior to acknowledge, after All-0 or All-1 or
when the LPWAN allows it.";
}
leaf bitmap-format {
when "derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-on-error')";
type bitmap-format-type;
default "bitmap-RFC8724";
description
"How the bitmaps are included in the SCHC ACK message.
Defined in RFC 9441.";
reference
"RFC 9441 Static Context Header Compression (SCHC)
Compound Acknowledgement (ACK)";
}
leaf last-bitmap-compression {
when "derived-from-or-self(../fragmentation-mode,
'fragmentation-mode-ack-on-error')";
type boolean;
default "true";
description
"When true, the ultimate bitmap in the SCHC ACK message
can be compressed. Default behavior from RFC 8724.
Defined in RFC 9441.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation.
RFC 9441 Static Context Header Compression (SCHC)
Compound Acknowledgement (ACK)";
}
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}
description
"RFC 8724 defines 3 fragmentation modes.";
}
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
grouping management-content {
description
"This group contains parameters to control management procedure.";
container guard-period {
leaf ticks-duration {
type uint8;
default "20";
description
"Duration of one tick in microseconds:
2^ticks-duration/10^6 = 1.048s.";
}
leaf ticks-numbers {
type uint16 {
range "0..max";
}
description
"Timer duration = ticks-numbers*2^ticks-duration / 10^6.";
}
}
}
// Define RuleID. RuleID is composed of a RuleID value and a
// RuleID length
grouping rule-id-type {
leaf rule-id-value {
type uint32;
description
"RuleID value. This value must be unique, considering its
length.";
}
leaf rule-id-length {
type uint8 {
range "0..32";
}
description
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"RuleID length, in bits. The value 0 is for implicit
Rules.";
}
description
"A RuleID is composed of a value and a length, expressed in
bits.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
// SCHC table for a specific device.
container context {
if-feature "management";
uses management-content;
description
"Management-related parameters that apply to the whole SCHC
context rather than to a single Rule.";
}
container schc {
list rule {
key "rule-id-value rule-id-length";
uses rule-id-type;
leaf rule-nature {
type nature-type;
mandatory true;
description
"Specify the Rule's nature.";
}
choice nature {
case fragmentation {
if-feature "fragmentation";
uses fragmentation-content;
}
case compression {
status deprecated;
if-feature "compression";
uses compression-content {
status deprecated;
}
}
case compression-universal {
if-feature "compression or management";
uses compression-content-universal;
}
description
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"A Rule is for compression, no-compression, fragmentation,
or management.";
}
description
"Set of compression, no-compression, or fragmentation
Rules identified by their rule-id.";
}
description
"A SCHC set of Rules is composed of a list of Rules used for
compression, no-compression, fragmentation, or management.";
reference
"RFC 8724 SCHC: Generic Framework for Static Context Header
Compression and Fragmentation";
}
rpc duplicate-rule {
input {
container from {
uses schc:rule-id-type;
description
"Source Rule ID";
}
container to {
uses schc:rule-id-type;
description
"Destination Rule ID";
}
leaf ipatch-sequence {
type binary;
description
"CBOR sequence for an CORECONF iPatch used to modify the
newly created Rule.
This parameter is optional, and set by default to 0xF6 (CBOR null)";
}
}
output {
leaf status {
type enumeration {
enum success-with-validation {
value 0;
}
enum success-not-validated {
value 1;
}
enum to-rule-already-exists {
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value -1;
}
enum from-rule-not-found {
value -2;
}
enum invalid-ipatch {
value -3;
}
}
description
"Return the status of the RPC. TO BE DEFINED MORE PRECISELY";
}
}
description
"This RPC duplicate a rule, from a existing one given in leaf 'from' to a new
non existing rule defined by 'to'. The content of the new rule may be updated
with a iPatch, where the CORECONF payload contained in 'ipatch-sequence'.";
}
}
<CODE ENDS>
Figure 13: Working Copy of the ietf-schc YANG Module
Acknowledgments
This document reuses text and structure from RFC 9363. The authors
thank the contributors and reviewers of that document.
This work was supported by the Sweden's Innovation Agency VINNOVA
within the EUREKA CELTIC-NEXT project CYPRESS.
This work has been supported by the SCHC Chair from IMT Atlantique
and Afnic.
The authors also thank Claude (Anthropic) for rewriting parts of this
document in more correct English and for checking its consistency.
Authors' Addresses
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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Marco Tiloca
RISE AB
Isafjordsgatan 22
SE-16440 Kista
Sweden
Email: marco.tiloca@ri.se
Ana Minaburo
Consultant
Email: ana@minaburo.com
Samar Sirohi
Institut MINES TELECOM; IMT Atlantique
2 rue de la Chataigneraie CS 17607
35576 Cesson-Sevigne Cedex
France
Email: Samar.Sirohi@imt-atlantique.fr
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