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IETF RFC 9595
Last modified on Thursday, August 1st, 2024
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Internet Engineering Task Force (IETF) M. Veillette, Ed.
Request for Comments: 9595 Trilliant Networks Inc.
Category: Standards Track A. Pelov, Ed.
ISSN: 2070-1721 IMT Atlantique
I. Petrov, Ed.
Google Switzerland GmbH
C. Bormann
Universität Bremen TZI
M. Richardson
Sandelman Software Works
July 2024
YANG Schema Item iDentifier (YANG SID)
 Abstract
YANG Schema Item iDentifiers (YANG SIDs) are globally unique 63-bit
unsigned integers used to identify YANG items. SIDs provide a more
compact method for identifying those YANG items that can be used
efficiently, notably in constrained environments (RFC 7228). This
document defines the semantics, registration processes, and
assignment processes for YANG SIDs for IETF-managed YANG modules. To
enable the implementation of these processes, this document also
defines a file format used to persist and publish assigned YANG SIDs.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/RFC 9595.
Copyright Notice
Copyright (c) 2024 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 described in Section 4.e of the
Trust Legal Provisions and are provided without warranty as described
in the Revised BSD License.
Table of Contents
1. Introduction
1.1. Terminology and Notation
2. Objectives
2.1. Technical Objectives
2.2. Module Evolution and Versioning
2.3. Solution Components and Derived Objectives
2.4. Parties and Roles
3. ".sid" File Lifecycle
4. ".sid" File Format
5. Security Considerations
6. IANA Considerations
6.1. YANG Namespace Registration
6.2. ".sid" File Format Module Registration
6.3. New IANA Registry: YANG-SID Mega-Ranges
6.3.1. Structure
6.3.2. Allocation Policy
6.3.2.1. First Allocation
6.3.2.2. Consecutive Allocations
6.3.3. Initial Contents of the Registry
6.4. New IANA Registry: IETF YANG-SID Ranges
6.4.1. Structure
6.4.2. Allocation Policy
6.4.3. Publication of the ".sid" File
6.4.4. Initial Contents of the Registry
6.5. New IANA Registry: IETF YANG-SID Modules
6.5.1. Structure
6.5.2. Allocation Policy
6.5.3. Recursive Allocation of YANG SIDs at Document Adoption
6.5.4. Initial Contents of the Registry
6.6. Media Type and Content-Format Registration
6.6.1. Media Type application/yang-sid+json
6.6.2. CoAP Content-Format
7. References
7.1. Normative References
7.2. Informative References
Appendix A. ".sid" File Example
Appendix B. SID Autogeneration
Appendix C. ".sid" File Lifecycle
C.1. ".sid" File Creation
C.2. ".sid" File Update
Appendix D. Keeping a ".sid" File in a YANG Instance Data File
Acknowledgments
Contributors
Authors' Addresses
1. Introduction
Some of the items defined in YANG [RFC 7950] require the use of a
unique identifier. In both the Network Configuration Protocol
(NETCONF) [RFC 6241] and RESTCONF [RFC 8040], these identifiers are
implemented using names. To allow the implementation of data models
defined in YANG in constrained devices [RFC 7228] and constrained
networks, a more compact method to identify YANG items is required.
This compact identifier, called the YANG Schema Item iDentifier or
YANG SID (or simply SID in this document and when the context is
clear), is encoded using a 63-bit unsigned integer. The limitation
to 63-bit unsigned integers allows SIDs to be manipulated more easily
on platforms that might otherwise lack 64-bit unsigned arithmetic.
The loss of a single bit of range is not significant, given the size
of the remaining space.
The following items are identified using SIDs:
* identities
* data nodes (note: including those nodes defined by the 'rc:yang-
data' extension [RFC 8040] and the 'sx:structure' extension
[RFC 8791])
* remote procedure calls (RPCs) and associated input(s) and
output(s)
* actions and associated input(s) and output(s)
* notifications and associated information
* YANG modules and features
It is possible that some protocols will use only a subset of the
assigned SIDs; for example, for protocols other than NETCONF
[RFC 6241] that provide access to YANG-modeled data, such as
[CORE-COMI], the transport of YANG module SIDs might be unnecessary.
Other protocols might need to be able to transport this information
-- for example, protocols related to discovery such as the
Constrained YANG Module Library [YANG-LIBRARY].
SIDs are globally unique integers. A registration system is used in
order to guarantee their uniqueness. SIDs are registered in blocks
called "SID ranges". Once they are considered "stable", SIDs are
assigned permanently. Items introduced by a new revision of a YANG
module are added to the list of SIDs already assigned. This is
discussed in more detail in Section 2.
The assignment of SIDs to YANG items is usually automated as
discussed in Appendix B, which also discusses some cases where manual
interventions may be appropriate.
Section 3 provides more details about the registration processes for
YANG modules and associated SIDs. To enable the implementation of
these processes, Section 4 defines a standard file format used to
store and publish SIDs.
IETF-managed YANG modules that need to allocate SIDs will use the
IANA mechanisms specified in this document. See Section 6 for
details. YANG modules created by other parties allocate SID ranges
using the IANA allocation mechanisms via Mega-Ranges (see
Section 6.3); within the Mega-Range allocation, those other parties
are free to make up their own mechanism.
Among other uses, YANG SIDs are particularly useful for obtaining a
compact encoding for YANG-CBOR [RFC 9254]. At the time of writing, a
tool for automated ".sid" file generation is available as part of the
open-source project PYANG [PYANG].
1.1. Terminology and Notation
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
[BCP14] (RFC 2119) (RFC 8174) when, and only when, they appear in all
capitals, as shown here.
The following terms are defined in [RFC 7950]:
* action
* feature
* module
* notification
* RPC
* schema node
* schema tree
* submodule
This specification also makes use of the following terminology:
item: A schema node, an identity, a module, or a feature defined
using the YANG modeling language.
YANG Schema Item iDentifier (YANG SID or simply SID): Unsigned
integer used to identify different YANG items (cf. Section 3.2 of
[RFC 9254]).
YANG name: Text string used to identify different YANG items
(cf. Section 3.3 of [RFC 9254]).
2. Objectives
The overriding objective of the SID assignment and registration
system is to ensure global interoperability of protocols that employ
SIDs in order to communicate about data modeled in YANG. This
objective poses certain requirements on the stability of SIDs while
at the same time not hindering active evolution of the YANG modules
the SIDs are intended to support.
Additional objectives include:
* enabling the developer of a YANG module to also be the originating
entity for the SIDs pertaining to that module.
* making it easy for YANG developers to obtain SIDs.
* enabling other developers to define SIDs for a module where the
developer of the module is not interested in assigning the SIDs.
* keeping an assignment regime that keeps short SIDs (2..4 bytes)
readily available for the applications that would benefit from
them while at the same time employing the vast 63-bit SID space to
facilitate permissionless actions.
* enabling multiple entities to provide services that support the
assignment of SIDs.
* maintaining some locality in the assignment of SIDs so the
efficiencies of the SID delta mechanism can be fully employed.
* enabling various software components to operate in terms of SIDs
without having complete information about other parties in the
communication process.
While IANA ultimately maintains the registries that govern SIDs for
IETF-defined modules, various support tools (such as, at the time of
writing, the YANG Catalog [yangcatalog]) need to provide the support
to enable SID assignment and use for modules still in IETF
development. Developers of open-source or proprietary YANG modules
also need to be able to serve as such entities autonomously, possibly
forming alliances independent of the IETF, while still fitting in the
overall SID number space managed by IANA. Obviously, this process
has a number of parallels to the management of IP addresses but is
also very different.
2.1. Technical Objectives
As discussed in the Introduction, SIDs are intended as globally
unique (unsigned) integers.
Specifically, this means that:
*Objective 1* (MUST): Any 63-bit unsigned integer either (1) is
unassigned as a SID or (2) immutably maps to EXACTLY one YANG
name. Only the transition from unassigned to that immutable
mapping is defined.
This enables a recipient of a data structure employing SIDs to
translate them into the globally meaningful YANG names that the
existing encodings of YANG data such as YANG-XML [RFC 7950] and YANG-
JSON [RFC 7951] employ today.
The term "YANG name" is not defined outside this document, and YANG
has a complex system of names and entities that can have those names.
Instead of defining the term technically, this set of objectives uses
it in such a way that the overall objectives of YANG SID can be
achieved.
A desirable objective is that:
*Objective 2* (SHOULD): Any YANG name in active use has one SID
assigned.
This means that:
1. There should not be YANG names without SIDs assigned.
2. YANG names should not have multiple SIDs assigned.
These objectives are unattainable in full, because YANG names are not
necessarily born with a SID assignment and because entirely
autonomous entities might decide to assign SIDs for the same YANG
name without communicating ("like ships in the night"). Note that as
long as this autonomy is maintained, any single observer will have
the impression that Objective 2 is attained. Only when entities that
have acted autonomously start communicating will a deviation be
observed.
2.2. Module Evolution and Versioning
YANG modules evolve (see Section 11 of [RFC 7950] and Section 4.27 of
RFC 8407 [BCP216]). The technical objectives listed above are stated
in terms that are independent of this evolution.
However, some modules are still in a very fluid state, and the
assignment of permanent SIDs to the YANG names created in them is
less desirable. This is true not only for new modules but also for
emerging new revisions of existing stable modules.
*Objective 3* (MUST): The SID management system is independent of
any module versioning.
2.3. Solution Components and Derived Objectives
A registration system is used in order to guarantee the uniqueness of
SIDs. To be able to provide some autonomy in allocation (and avoid
information disclosure where it is not desirable), SIDs are
registered in blocks called "SID ranges".
SIDs are assigned permanently.
Items introduced by a new revision of a YANG module are added to the
list of SIDs already assigned.
2.4. Parties and Roles
In the YANG development process, we can discern a number of parties
that are concerned with a YANG module:
module controller:
The owner of the YANG module, i.e., the controller of the module's
evolution.
registration entity:
The controller of the module namespace, specifically also of the
prefixes that are in common use. (This is not a required party.)
module repository:
An entity that supplies modules to module users. This can be an
"official" entity (e.g., IANA for IETF modules) or an "unofficial"
entity (e.g., the YANG Catalog [yangcatalog]). Not all
repositories are in a position to act as a registry, i.e., as a
permanent record for the information they supply; these
repositories need to recur to module owners as a stable source.
module user:
An entity that uses a module, after obtaining it from the module
controller or a module repository.
This set of parties needs to evolve to take on the additional roles
that the SID assignment process requires:
SID assigner:
An entity that assigns SIDs for a module. Objective 2 aims at
having only one SID assigner for each module. SID assigners
preferably stay the same over a module development process;
however, this specification provides ".sid" files to ensure an
organized handover.
SID range registry:
An entity that supplies a SID assigner with SID ranges that it can
use in assigning SIDs for a module. (In this specification, there
is a structure with Mega-Ranges and individual SID ranges; this is
not relevant here.)
SID repository:
An entity that supplies SID assignments to SID users, usually in
the form of a ".sid" file.
SID user:
The module user that uses the SIDs provided by a SID assigner for
a YANG module. SID users need to find SID assigners (or at least
their SID assignments).
As the use of SIDs with YANG data models is introduced, the
distribution of the SID roles to the existing parties for a YANG
module will evolve.
The desirable end state of this evolution is shown in Table 1.
+====================+======================================+
| Role | Party |
+====================+======================================+
| SID assigner | module developer |
+--------------------+--------------------------------------+
| SID range registry | (as discussed in this specification) |
+--------------------+--------------------------------------+
| SID repository | module repository |
+--------------------+--------------------------------------+
| SID user | module user (naturally) |
+--------------------+--------------------------------------+
Table 1: Roles and Parties: Desired End State
This grouping of roles and parties puts the module developer in a
position where it can achieve the objectives laid out in this section
(a "type-1", "SID-guiding" module controller). (While a third party
might theoretically assign additional SIDs and conflict with
Objective 2, there is very little reason to do so if ".sid" files are
always provided by the module developer with the module.)
The rest of this section is concerned with the transition to this end
state.
For existing modules, there is no ".sid" file. The entity that
stands in as the SID assigner is not specified. This situation has
the highest potential for conflict with Objective 2.
Similarly, for new module development, the module owner may not have
heard about SIDs or may not be interested in assigning them (e.g.,
because of lack of software or procedures within their organization).
For these two cases (which we will collectively call "type-3", "SID-
oblivious" module controller), module repositories can act as a
mediator, giving SID users access to a SID assigner that is carefully
chosen to be a likely choice by other module repositories as well,
maximizing the likelihood of achieving Objective 2.
If a module controller has heard about SIDs but is not assigning them
yet, it can designate a SID assigner instead. This can lead to a
stable, unique set of SID assignments being provided indirectly by a
("type-2", "SID-aware") module developer. Entities offering
designated SID assigner services could make these available in an
easy-to-use way, e.g., via a web interface.
The entity acting as a SID assigner minimally needs to record the SID
range it uses for the SID assignment. If the SID range registry
employed can record the module name and revision and if the
assignment processes (including the software used) are stable, the
SID assigner can theoretically reconstruct its assignments, but this
could invite implementation bugs.
SID assigners attending to a module in development (not yet stable)
need to decide whether SIDs for a new revision are reassigned from
scratch ("clean slate") or use existing assignments from a previous
revision as a base, only assigning new SIDs for new names. Once a
module is declared stable, its SID assignments SHOULD be declared
stable as well (except that, for existing YANG modules, some review
may be needed before this is done).
This specification does not further discuss how mediating entities
such as designated SID assigners or SID repositories could operate;
instead, it supplies objectives for their operation.
3. ".sid" File Lifecycle
YANG is a language designed to model data accessed using one of the
compatible protocols (e.g., NETCONF [RFC 6241], RESTCONF [RFC 8040],
and the CoAP Management Interface (CORECONF) [CORE-COMI]). A YANG
module defines hierarchies of data, including configuration, state
data, RPCs, actions, and notifications.
Many YANG modules are not created in the context of constrained
applications. YANG modules can be implemented using NETCONF
[RFC 6241] or RESTCONF [RFC 8040] without the need to assign SIDs.
As needed, authors of YANG modules can assign SIDs to their YANG
modules. In order to do that, they should first obtain a SID range
from a registry and use that range to assign or generate SIDs to
items in their YANG module. The assignments can then be stored in a
".sid" file. For an example of how this could be achieved, please
refer to Appendix C.
Items introduced by a new revision of a YANG module are added to the
list of SIDs already assigned. When this is done during the
development of a new protocol document, it may be necessary to make
provisional assignments. They may get changed, revised, or withdrawn
during the development of a new standard. These provisional
assignments are marked with a status of "unstable", so that they can
be removed and the SID number possibly reassigned for a different
YANG schema name/path later in the development process. When the
specification is advanced to a final document, the assignment is
marked with a status of "stable". During a period of development
starting from a published specification, two variants of the ".sid"
file should be made available by the tooling involved in that
development: (1) a "published" ".sid" file with the existing stable
SID assignments only (which the development effort should keep
stable), as well as (2) an "unpublished" ".sid" file that also
contains the unstable SID assignments.
Registration of the ".sid" file associated with a YANG module is
optional but recommended; doing so will promote interoperability
between devices and avoid duplicate allocation of SIDs to a single
YANG module. Different registries might have different requirements
for the registration and publication of the ".sid" files. For a
diagram of one possible scenario, please refer to the activity
diagram shown in Figure 4 in Appendix C.
Each time a YANG module, one or more of its imported modules, or one
or more of its included submodules are updated, a new ".sid" file MAY
be created if the new or updated items will need SIDs. All the SIDs
present in a previous version of the ".sid" file that was in active
use MUST be present in the new version as well. The creation of this
new version of the ".sid" file SHOULD be performed using an automated
tool.
If a new revision requires more SIDs than initially allocated, a new
SID range MUST be added to the 'assignment-range' item as defined in
Section 4. These extra SIDs are used for subsequent assignments.
For an example of this update process, see the activity diagram shown
in Figure 5 in Appendix C.
4. ".sid" File Format
".sid" files are used to persist and publish SIDs assigned to the
different YANG items in a specific YANG module.
The following tree diagram [BCP215] provides an overview of the data
model:
module: ietf-sid-file
structure sid-file:
+-- module-name yang:yang-identifier
+-- module-revision? revision-identifier
+-- sid-file-version? sid-file-version-identifier
+-- sid-file-status? enumeration
+-- description? string
+-- dependency-revision* [module-name]
| +-- module-name yang:yang-identifier
| +-- module-revision revision-identifier
+-- assignment-range* [entry-point]
| +-- entry-point sid
| +-- size uint64
+-- item* [namespace identifier]
+-- status? enumeration
+-- namespace enumeration
+-- identifier union
+-- sid sid
Figure 1: YANG Tree for 'ietf-sid-file'
The following YANG module defines the structure of ".sid" files.
Encoding is performed in JSON [STD90] using the rules defined in
[RFC 7951]. This module imports 'ietf-yang-types' [RFC 6991] and
'ietf-yang-structure-ext' [RFC 8791]. It also references [STD68],
[RFC 7950], and [BCP216].
<CODE BEGINS> file "ietf-sid-file@2024-07-31.yang"
module ietf-sid-file {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-sid-file";
prefix sid;
import ietf-yang-types {
prefix yang;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-yang-structure-ext {
prefix sx;
reference
"RFC 8791: YANG Data Structure Extensions";
}
organization
"IETF CORE Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/core/>
WG List: <mailto:core@ietf.org>
Editor: Michel Veillette
<mailto:michel.veillette@trilliant.com>
Editor: Andy Bierman
<mailto:andy@yumaworks.com>
Editor: Alexander Pelov
<mailto:alexander.pelov@imt-atlantique.fr>
Editor: Ivaylo Petrov
<mailto:ivaylopetrov@google.com>";
description
"This module defines the structure of the '.sid' files.
Each '.sid' file contains the mapping between each
string identifier defined by a YANG module and a
corresponding numeric value called a YANG SID.
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.
Copyright (c) 2024 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 9595; see
the RFC itself for full legal notices.";
revision 2024-07-31 {
description
"Initial revision.";
reference
"RFC 9595: YANG Schema Item iDentifier (YANG SID)";
}
typedef revision-identifier {
type string {
pattern '[0-9]{4}-[0-9]{2}-[0-9]{2}';
}
description
"Represents a date in YYYY-MM-DD format.";
}
typedef sid-file-version-identifier {
type uint32;
description
"Represents the version of a '.sid' file.";
}
typedef sid {
type uint64 {
range "0..9223372036854775807";
}
description
"YANG Schema Item iDentifier.";
reference
"RFC 9595: YANG Schema Item iDentifier (YANG SID)";
}
typedef schema-node-path {
type string {
pattern
'/[a-zA-Z_][a-zA-Z0-9\-_.]*:[a-zA-Z_][a-zA-Z0-9\-_.]*' +
'(/[a-zA-Z_][a-zA-Z0-9\-_.]*(:[a-zA-Z_][a-zA-Z0-9\-_.]*)?)*';
}
description
"A schema-node path is an absolute YANG schema-node
identifier as defined by the YANG ABNF rule
'absolute-schema-nodeid', except that module names are used
instead of prefixes.
This string additionally follows the following rules:
- The leftmost (top-level) data node name is always in the
namespace-qualified form.
- Any subsequent schema-node name is in the
namespace-qualified form if the node is defined in a
module other than its parent node. Otherwise, the
simple form is used. No predicates are allowed.";
reference
"RFC 5234 (STD 68): Augmented BNF for Syntax Specifications:
ABNF
RFC 7950: The YANG 1.1 Data Modeling Language,
Section 6.5: Schema Node Identifier";
}
sx:structure sid-file {
uses sid-file-contents;
}
grouping sid-file {
description
"A grouping that contains a YANG container
representing the file structure of a '.sid' file.";
container sid-file {
description
"A wrapper container that together with the 'sx:structure'
extension marks the YANG data structures inside as not
being intended to be implemented as part of a
configuration datastore or as an operational state within
the server.";
uses sid-file-contents;
}
}
grouping sid-file-contents {
description
"A grouping that defines the contents of a container that
represents the file structure of a '.sid' file.";
leaf module-name {
type yang:yang-identifier;
mandatory true;
description
"Name of the YANG module associated with this
'.sid' file.";
}
leaf module-revision {
type revision-identifier;
description
"Revision of the YANG module associated with this '.sid'
file.
This leaf is not present if no revision statement is
defined in the YANG module.";
}
leaf sid-file-version {
type sid-file-version-identifier;
default 0;
description
"Optional leaf that specifies the version number of the
'.sid' file. '.sid' files and the version sequence are
specific to a given YANG module revision. This number
starts at zero when there is a new YANG module revision
and increases monotonically. This number can distinguish
updates to the '.sid' file - for instance, as the result
of new processing or reported errata.";
}
leaf sid-file-status {
type enumeration {
enum unpublished {
description
"This '.sid' file is unpublished (BCP 216) and is
also called a work-in-progress or workfile.
This may be when it accompanies an unpublished YANG
module or when only the '.sid' file itself is
unpublished.
The 'item' list MAY contain entries with a status
value of 'unstable'.";
reference
"RFC 8407 (BCP 216): Guidelines for Authors and
Reviewers of Documents Containing
YANG Data Models";
}
enum published {
description
"This '.sid' file is published. This status
applies to '.sid' files for published YANG modules.
The 'item' list MUST NOT contain entries with a
status value of 'unstable'.";
}
}
default "published";
description
"Optional leaf that specifies the status of the
'.sid' file.";
}
leaf description {
type string;
description
"Free-form meta-information about the generated file. It
might include a '.sid' file generation tool and time,
among other things.";
}
list dependency-revision {
key "module-name";
description
"Information about the revision used during the
'.sid' file generation of each dependency, i.e., each
YANG module that the YANG module associated with this
'.sid' file imported.";
leaf module-name {
type yang:yang-identifier;
description
"YANG module name of this dependency.";
}
leaf module-revision {
type revision-identifier;
mandatory true;
description
"Revision of the YANG module of this dependency.";
}
}
list assignment-range {
key "entry-point";
description
"YANG-SID Range(s) allocated to the YANG module
identified by 'module-name' and 'module-revision'.
- The first available value in the YANG-SID Range is
'entry-point', and the last available value in the
range is ('entry-point' + size - 1).
- The YANG-SID Ranges specified by all
'assignment-range' entries MUST NOT overlap.";
leaf entry-point {
type sid;
description
"Lowest YANG SID available for assignment.";
}
leaf size {
type uint64;
mandatory true;
description
"Number of YANG SIDs available for assignment.";
}
}
list item {
key "namespace identifier";
unique "sid";
description
"Each entry within this list defines the mapping between
a YANG item string identifier and a YANG SID. This list
MUST include a mapping entry for each YANG item defined
by the YANG module identified by 'module-name' and
'module-revision'.";
leaf status {
type enumeration {
enum stable {
value 0;
description
"This SID allocation has been published as the
stable allocation for the given namespace and
identifier.";
}
enum unstable {
value 1;
description
"This SID allocation has been done during a
development process; it is not yet stable.";
}
enum obsolete {
value 2;
description
"This SID allocation is no longer in use. It is
recorded to avoid reallocation of its SID value.";
}
}
default "stable";
description
"The status field contains information about the
stability of the allocation. For each specific SID
value, over time it can only transition from
'unstable' to 'stable', and possibly from 'stable' to
'obsolete'.";
}
leaf namespace {
type enumeration {
enum module {
value 0;
description
"All module and submodule names share the same
global module identifier namespace.";
}
enum identity {
value 1;
description
"All identity names defined in a module and its
submodules share the same identity identifier
namespace.";
}
enum feature {
value 2;
description
"All feature names defined in a module and its
submodules share the same feature identifier
namespace.";
}
enum data {
value 3;
description
"The namespace for all data nodes, as defined in
YANG.";
}
}
description
"Namespace of the YANG item for this mapping entry.";
}
leaf identifier {
type union {
type yang:yang-identifier;
type schema-node-path;
}
description
"String identifier of the YANG item for this mapping
entry.
If the corresponding 'namespace' field is 'module',
'feature', or 'identity', then this field MUST
contain a valid YANG identifier string.
If the corresponding 'namespace' field is 'data',
then this field MUST contain a valid schema-node
path.";
}
leaf sid {
type sid;
mandatory true;
description
"YANG SID assigned to the YANG item for this mapping
entry.";
}
}
}
}
<CODE ENDS>
Figure 2: YANG Module 'ietf-sid-file'
5. Security Considerations
This document defines a new type of identifier used to encode data
that are modeled in YANG [RFC 7950]. This new identifier maps
semantic concepts to integers, and if the source of this mapping is
not trusted, then new security risks might occur if an attacker can
control the mapping.
At the time of writing, it is expected that the ".sid" files will be
processed by a software developer, within a software development
environment. Developers are advised to only import ".sid" files from
authoritative sources. IANA is the authoritative source for IETF-
managed YANG modules.
Conceptually, ".sid" files could be processed by less-constrained
target systems such as network management systems. Such systems need
to take extra care to make sure that they are only processing ".sid"
files from authoritative sources that are as authoritative as the
YANG modules that they are using.
".sid" files are identified with and can employ _dereferenceable
identifiers_, i.e., identifiers that could lead implementations in
certain situations to automatically perform remote access, the target
of which is indicated at least partially by those identifiers. This
can give an attacker information from and/or control over such
accesses, which can have security and privacy implications. Please
also see Sections 6 and 7 of [DEREF-ID] for further considerations
that may be applicable.
6. IANA Considerations
6.1. YANG Namespace Registration
This document registers the following XML namespace URN in the "IETF
XML Registry", following the format defined in [BCP81]:
URI: urn:ietf:params:xml:ns:yang:ietf-sid-file
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
Reference: RFC 9595
6.2. ".sid" File Format Module Registration
This document registers one YANG module in the "YANG Module Names"
registry [RFC 6020]:
Name: ietf-sid-file
Namespace: urn:ietf:params:xml:ns:yang:ietf-sid-file
Prefix: sid
Reference: RFC 9595
6.3. New IANA Registry: YANG-SID Mega-Ranges
The name of this registry is "YANG-SID Mega-Ranges". This registry
is used to record the delegation of the management of a block of SIDs
to a third party (such as Standards Development Organizations (SDOs)
or registrars).
6.3.1. Structure
Each entry in this registry must include:
* The entry point (first SID) of the registered SID block.
* The size of the registered SID block. The size SHOULD be one
million (1,000,000) SIDs, but in exceptional cases, it MAY be a
multiple of 1,000,000.
* The policy of SID range allocations: Public, Private, or both.
* The contact information of the requesting organization, including
the following:
- Organization name.
- URL.
6.3.2. Allocation Policy
The IANA policy for future additions to this registry is "Expert
Review" (Section 4.5 of RFC 8126 [BCP26]).
An organization requesting to manage a YANG-SID Range (and thus have
an entry in the "YANG-SID Mega-Ranges" registry) must ensure the
following capacities:
* The capacity to manage and operate a registry of YANG-SID Ranges.
A registry of YANG-SID Ranges MUST provide the following
information for all YANG-SID Ranges allocated by the registry:
- The entry point of the allocated YANG-SID Range.
- The size of the allocated YANG-SID Range.
- Type: Public or Private.
o Public ranges MUST include at least a reference to the YANG
module and ".sid" files for that YANG-SID Range (e.g., see
Section 6.4.3 as an example for how this is handled for the
"IETF YANG-SID Ranges" registry).
o Private ranges MUST be marked as "Private".
* A policy of allocation, which clearly identifies whether the YANG-
SID Range allocations would be Private, Public, or both.
* Technical capacity to provide or refer to ".sid" files in a way
that meets the security objective of data integrity for these
files (see also Section 5).
* Technical capacity to ensure the sustained operation of the
registry for a period of at least 5 years. If registrations in
the Private category are allowed, the period must be at least 10
years.
If a size of the allocation beyond 1,000,000 is desired, the
organization must demonstrate the sustainability of the technical
approach for utilizing this size of allocation and how it does not
negatively impact the overall usability of the SID allocation
mechanisms; such allocations are preferably placed in the space above
4,295,000,000 (64-bit space).
6.3.2.1. First Allocation
For a first allocation to be provided, the requesting organization
must demonstrate a functional registry infrastructure.
6.3.2.2. Consecutive Allocations
On one or more subsequent allocation requests, the organization must
demonstrate the exhaustion of the prior range. These conditions need
to be asserted by the assigned expert(s).
If such a request for an additional allocation is made within 3 years
of the last allocation, the experts need to discuss this request on
the CORE Working Group mailing list and consensus needs to be
obtained before allocating a new Mega-Range.
6.3.3. Initial Contents of the Registry
This registry contains the following initial entry:
+=====+=========+==========+============+=========================+
|Entry|Size |Allocation|Organization| URL |
|Point| | |Name | |
+=====+=========+==========+============+=========================+
|0 |1,000,000|Public |IANA | <https://www.iana.org/> |
+-----+---------+----------+------------+-------------------------+
Table 2: YANG-SID Mega-Ranges Registry: Initial Assignment
6.4. New IANA Registry: IETF YANG-SID Ranges
The name of this registry is "IETF YANG-SID Ranges". This registry
is used to record information related to the assignment of SID Ranges
(e.g., entry point and size) to YANG modules identified by module
name.
6.4.1. Structure
Each entry in this registry must include:
* The SID range entry point.
* The SID range size.
* The YANG module name.
* A document reference (the document making the registration).
6.4.2. Allocation Policy
The first million SIDs assigned to IANA are subdivided as follows:
1. The range of 0 to 999 (size 1,000) is subject to "IESG Approval"
as defined in Section 4.10 of RFC 8126 [BCP26]; of these, SID
value 0 has been reserved for implementations to internally
signify the absence of a SID number and does not occur in
interchange.
2. The ranges of 1,000 to 59,999 (size 59,000) and 100,000 to
299,999 (size 200,000) are designated for YANG modules defined in
RFCs.
a. The IANA policy for additions to this registry is:
i. "Expert Review" (Section 4.5 of RFC 8126 [BCP26]) if the
".sid" file comes from a YANG module from an existing
RFC.
ii. "RFC Required" (Section 4.7 of RFC 8126 [BCP26])
otherwise.
b. The expert MUST verify that the YANG module for which this
allocation is made has an RFC (existing RFC) OR is on track
to become an RFC (Early Allocation with a request from the
working group chairs as defined by [BCP100]).
3. The range of 60,000 to 99,999 (size 40,000) is reserved for
experimental YANG modules. This range MUST NOT be used in
operational deployments, since these SIDs are not globally unique
and their interoperability is therefore limited. The IANA policy
for this range is "Experimental Use" (Section 4.2 of RFC 8126
[BCP26]).
4. The range of 300,000 to 999,999 (size 700,000) is "Reserved" as
defined in Section 6 of RFC 8126 [BCP26].
+=============+=========+=============================+
| Entry Point | Size | IANA Policy |
+=============+=========+=============================+
| 0 | 1,000 | IESG Approval |
+-------------+---------+-----------------------------+
| 1,000 | 59,000 | RFC and Expert Review |
| | | Required (see item 2 above) |
+-------------+---------+-----------------------------+
| 60,000 | 40,000 | Reserved for Experimental |
| | | Use |
+-------------+---------+-----------------------------+
| 100,000 | 200,000 | RFC and Expert Review |
| | | Required (see item 2 above) |
+-------------+---------+-----------------------------+
| 300,000 | 700,000 | Reserved |
+-------------+---------+-----------------------------+
Table 3: IETF YANG-SID Ranges Registry: Policies
for IETF Ranges
The size of the SID range allocated for a YANG module is recommended
to be a multiple of 50 and to be at least 33% above the current
number of YANG items. This headroom allows assignments within the
same range of new YANG items introduced by subsequent revisions. The
SID range size SHOULD NOT exceed 1,000; a larger size may be
requested by the authors if this recommendation is considered
insufficient. It is important to note that an additional SID range
can be allocated to an existing YANG module if the initial range is
exhausted; this then just leads to a slightly less efficient
representation.
If a SID range is allocated for an existing RFC through the "Expert
Review" policy (Section 4.5 of RFC 8126 [BCP26]), the Reference field
for the given allocation should point to the RFC that the YANG module
is defined in.
If a SID range is required before publishing the RFC due to
implementations needing stable SID values, Early Allocation as
defined in [BCP100] can be employed for the "RFC Required" range
(Section 2 of RFC 7120 [BCP100]).
6.4.3. Publication of the ".sid" File
During an RFC's publication process, IANA contacts the designated
expert team ("the team"), who are responsible for delivering a final
".sid" file for each module defined by the RFC. For a type-3
developer (SID-oblivious; see Section 2.4), the team creates a new
".sid" file from each YANG module; see below. For a type-2 (SID-
aware) developer, the team first obtains the existing draft ".sid"
file from a stable reference in the approved draft; for a type-1
(SID-guiding) developer, the team extracts the ".sid" file from the
approved draft.
The team uses a tool to generate a final ".sid" file from each YANG
module; the final ".sid" file has all SID assignments set to "stable"
and the ".sid" file status set to "published". A published ".sid"
file MUST NOT contain SID assignments with a status of "unstable".
For the cases other than type-3 (SID-oblivious), the team feeds the
existing draft ".sid" file as an input ("reference ".sid" file") to
the tool so that the changes resulting from regeneration are minimal.
For YANG modules that are revisions of previously published modules,
any existing published ".sid" file needs to serve as a reference
".sid" file for the tool, during generation of either the revised
draft ".sid" file (type-1, type-2) or the final ".sid" file (type-3).
In any case, the team checks the generated file, including checking
for validity as a ".sid" file, for consistency with the SID range
allocations, for full coverage of the YANG items in the YANG module,
and for the best achievable consistency with the existing draft
".sid" file.
The designated experts then give the ".sid" file to IANA to publish
in the "IETF YANG-SID Modules" registry (Section 6.5) along with the
YANG module.
The ".sid" file MUST NOT be published as part of the RFC: the IANA
registry is authoritative, and a link to it is to be inserted in the
RFC. (Note that the present RFC is an exception to this rule, as the
".sid" file also serves as an example for exposition.) Internet-
Drafts that need SIDs assigned to their new modules for use in the
text of the document, e.g., for examples, need to alert the RFC
Editor in the draft text that this is the case. Such RFCs cannot be
produced by type-3 (SID-oblivious) developers: the SIDs used in the
text need to be assigned in the existing draft ".sid" file, and the
designated expert team needs to check that the assignments in the
final ".sid" file are consistent with the usage in the RFC text or
that the approved draft text is changed appropriately.
6.4.4. Initial Contents of the Registry
Initial entries in this registry are as follows:
+=============+======+=============================+=============+
| Entry Point | Size | Module Name | Reference |
+=============+======+=============================+=============+
| 0 | 1 | (Reserved: not a valid SID) | RFC 9595 |
+-------------+------+-----------------------------+-------------+
| 1,000 | 100 | ietf-coreconf | RFC 9595, |
| | | | [CORE-COMI] |
+-------------+------+-----------------------------+-------------+
| 1,100 | 50 | ietf-yang-types | [RFC 6991] |
+-------------+------+-----------------------------+-------------+
| 1,150 | 50 | ietf-inet-types | [RFC 6991] |
+-------------+------+-----------------------------+-------------+
| 1,200 | 50 | iana-crypt-hash | [RFC 7317] |
+-------------+------+-----------------------------+-------------+
| 1,250 | 50 | ietf-netconf-acm | [STD91] |
+-------------+------+-----------------------------+-------------+
| 1,300 | 50 | ietf-sid-file | RFC 9595 |
+-------------+------+-----------------------------+-------------+
| 1,500 | 100 | ietf-interfaces | [RFC 8343] |
+-------------+------+-----------------------------+-------------+
| 1,600 | 100 | ietf-ip | [RFC 8344] |
+-------------+------+-----------------------------+-------------+
| 1,700 | 100 | ietf-system | [RFC 7317] |
+-------------+------+-----------------------------+-------------+
| 1,800 | 400 | iana-if-type | [RFC 7224] |
+-------------+------+-----------------------------+-------------+
Table 4: IETF YANG-SID Ranges Registry: Initial Range Assignments
For allocation, RFC publication of the YANG module is required as per
the "RFC Required" policy defined in Section 4.7 of RFC 8126 [BCP26].
The YANG module must be registered in the "YANG Module Names"
registry according to the rules specified in Section 14 of [RFC 6020].
6.5. New IANA Registry: IETF YANG-SID Modules
The name of this registry is "IETF YANG-SID Modules". This registry
is used to record the allocation of SIDs for individual YANG module
items.
6.5.1. Structure
Each entry in this registry must include:
* The YANG module name. This module name must be present in the
"Name" column of the "YANG Module Names" registry.
* A URI for the associated ".yang" file. This file link must be
present in the "File" column of the "YANG Module Names" registry.
* The URI for the ".sid" file that defines the allocation. The
".sid" file is stored by IANA.
* The number of actually allocated SIDs in the ".sid" file.
6.5.2. Allocation Policy
The allocation policy is "Expert Review" (Section 4.5 of RFC 8126
[BCP26]). The expert MUST ensure that the following conditions are
met:
* The ".sid" file has a valid structure:
- The ".sid" file MUST be a valid JSON file following the
structure of the module defined in this document.
* The ".sid" file allocates individual SIDs ONLY in the YANG-SID
Ranges for this YANG module (as allocated in the "IETF YANG-SID
Ranges" registry):
- All SIDs in this ".sid" file MUST be within the ranges
allocated to this YANG module in the "IETF YANG-SID Ranges"
registry.
* If another ".sid" file has already allocated SIDs for this YANG
module (e.g., for older or newer versions of the YANG module), the
YANG items are assigned the same SIDs as those in the other ".sid"
file.
* If there is an older version of the ".sid" file, all allocated
SIDs from that version are still present in the current version of
the ".sid" file.
6.5.3. Recursive Allocation of YANG SIDs at Document Adoption
Due to the difficulty in changing SID values during IETF document
processing, it is expected that most documents will ask for SID range
allocations using Early Allocations [BCP100]. The details of the
Early Allocation to be requested, including the timeline envisioned,
should be included in any working group adoption call. Prior to
working group adoption, an Internet-Draft author can use the
experimental SID range (as per Section 6.4.2) for their SID
allocations or other values that do not create ambiguity with other
SID uses (for example, they can use ranges and SIDs registered in a
non-IANA-managed registry that is based on a YANG-SID Mega-Range
assignment).
After working group adoption, any modification of a ".sid" file is
expected to be discussed on the mailing lists of the appropriate
working groups. Specific attention should be paid to implementers'
opinions after Working Group Last Call if a SID value is to change
its meaning. In all cases, a ".sid" file and the SIDs associated
with it are subject to change before the publication of an Internet-
Draft as an RFC.
As the concept of SIDs is first used, many existing, previously
published YANG modules will not have SID allocations. For an
allocation to be useful, the included YANG modules may also need to
have SID allocations made, in a process that will generally be
analogous to that in Section 6.4.3 for the type-3 (SID-oblivious)
case.
The expert reviewer who performs the (Early) Allocation analysis will
need to go through the list of included YANG modules and perform SID
allocations for those modules as well.
* If the document is a published RFC, then the allocation of SIDs
for its referenced YANG modules is permanent. The expert reviewer
provides the generated ".sid" file to IANA for registration.
* If the document is an unprocessed Internet-Draft adopted in a
working group, then an Early Allocation is performed for this
document as well. Early Allocations require approval by an IESG
area director. An Early Allocation that requires additional
allocations will list the other allocations in its description and
will be cross-posted to the mailing lists of any other working
groups concerned.
* A YANG module that references a module in a document that has not
yet been adopted by any working group will be unable to perform an
Early Allocation for that other document until it is adopted by a
working group. As described in Section 3 of RFC 7120 [BCP100], a
shepherding AD will stand in for the working group chairs if the
document is not the product of an IETF working group, effectively
allowing the AD to exempt a document from this policy.
At the end of the IETF process, all the dependencies of a given
module for which SIDs are assigned should also have SIDs assigned.
Those dependencies' assignments should be permanent (not Early
Allocation).
A previously SID-allocated YANG module that changes its references to
include a YANG module for which there is no SID allocation needs to
repeat the Early Allocation process.
[BCP100] defines a time limit for the validity of Early Allocations,
after which they expire unless they are renewed. Section 3.3 of RFC
7120 [BCP100] also says:
| Note that if a document is submitted for review to the IESG, and
| at the time of submission some Early Allocations are valid (not
| expired), these allocations must not be considered to have expired
| while the document is under IESG consideration or is awaiting
| publication in the RFC Editor's queue after approval by the IESG.
6.5.4. Initial Contents of the Registry
At the time of writing, this registry does not contain any entries.
6.6. Media Type and Content-Format Registration
6.6.1. Media Type application/yang-sid+json
This document adds the following media type to the "Media Types"
registry.
+===============+===========================+===========+
| Name | Template | Reference |
+===============+===========================+===========+
| yang-sid+json | application/yang-sid+json | RFC 9595 |
+---------------+---------------------------+-----------+
Table 5: ".sid" File Media Type Registration
Type name: application
Subtype name: yang-sid+json
Required parameters: N/A
Optional parameters: N/A
Encoding considerations: binary (UTF-8)
Security considerations: See Section 5 of RFC 9595.
Published specification: RFC 9595
Applications that use this media type: Applications that need to
obtain YANG SIDs to interchange YANG-modeled data in a concise and
efficient representation.
Fragment identifier considerations: The syntax and semantics of
fragment identifiers specified for "application/yang-sid+json" is
as specified for "application/json". (At publication of this
document, there is no fragment identification syntax defined for
"application/json".)
Additional information:
Magic number(s): N/A
File extension(s): .sid
Macintosh file type code(s): N/A
Person & email address to contact for further information: CORE WG
mailing list (core@ietf.org) or IETF Applications and Real-Time
Area (art@ietf.org)
Intended usage: COMMON
Restrictions on usage: none
Author/Change controller: IETF
6.6.2. CoAP Content-Format
This document adds the following Content-Format to the "CoAP Content-
Formats" registry within the "Constrained RESTful Environments (CoRE)
Parameters" group of registries, where 260 has been assigned from the
"IETF Review" (256-9,999) range (see Section 4.8 of RFC 8126
[BCP26]).
+===========================+================+=====+===========+
| Content Type | Content Coding | ID | Reference |
+===========================+================+=====+===========+
| application/yang-sid+json | - | 260 | RFC 9595 |
+---------------------------+----------------+-----+-----------+
Table 6: ".sid" File Content-Format Registration
7. References
7.1. Normative References
[BCP100] Best Current Practice 100,
<https://www.rfc-editor.org/info/bcp100>.
At the time of writing, this BCP comprises the following:
Cotton, M., "Early IANA Allocation of Standards Track Code
Points", BCP 100, RFC 7120, DOI 10.17487/RFC 7120, January
2014, <https://www.rfc-editor.org/info/RFC 7120>.
[BCP14] Best Current Practice 14,
<https://www.rfc-editor.org/info/bcp14>.
At the time of writing, this BCP comprises the following:
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC 2119, March 1997,
<https://www.rfc-editor.org/info/RFC 2119>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC 8174,
May 2017, <https://www.rfc-editor.org/info/RFC 8174>.
[BCP81] Best Current Practice 81,
<https://www.rfc-editor.org/info/bcp81>.
At the time of writing, this BCP comprises the following:
Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC 3688, January 2004,
<https://www.rfc-editor.org/info/RFC 3688>.
[RFC 6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC 6991, July 2013,
<https://www.rfc-editor.org/info/RFC 6991>.
[RFC 7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC 7950, August 2016,
<https://www.rfc-editor.org/info/RFC 7950>.
[RFC 7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC 7951, August 2016,
<https://www.rfc-editor.org/info/RFC 7951>.
[RFC 8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC 8040, January 2017,
<https://www.rfc-editor.org/info/RFC 8040>.
[RFC 8791] Bierman, A., Björklund, M., and K. Watsen, "YANG Data
Structure Extensions", RFC 8791, DOI 10.17487/RFC 8791,
June 2020, <https://www.rfc-editor.org/info/RFC 8791>.
[STD68] Internet Standard 68,
<https://www.rfc-editor.org/info/std68>.
At the time of writing, this STD comprises the following:
Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC 5234, January 2008,
<https://www.rfc-editor.org/info/RFC 5234>.
[STD90] Internet Standard 90,
<https://www.rfc-editor.org/info/std90>.
At the time of writing, this STD comprises the following:
Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC 8259, December 2017,
<https://www.rfc-editor.org/info/RFC 8259>.
7.2. Informative References
[BCP215] Best Current Practice 215,
<https://www.rfc-editor.org/info/bcp215>.
At the time of writing, this BCP comprises the following:
Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC 8340, March 2018,
<https://www.rfc-editor.org/info/RFC 8340>.
[BCP216] Best Current Practice 216,
<https://www.rfc-editor.org/info/bcp216>.
At the time of writing, this BCP comprises the following:
Bierman, A., "Guidelines for Authors and Reviewers of
Documents Containing YANG Data Models", BCP 216, RFC 8407,
DOI 10.17487/RFC 8407, October 2018,
<https://www.rfc-editor.org/info/RFC 8407>.
[BCP26] Best Current Practice 26,
<https://www.rfc-editor.org/info/bcp26>.
At the time of writing, this BCP comprises the following:
Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC 8126, June 2017,
<https://www.rfc-editor.org/info/RFC 8126>.
[CORE-COMI]
Veillette, M., Ed., van der Stok, P., Ed., Pelov, A., Ed.,
Bierman, A., and C. Bormann, Ed., "CoAP Management
Interface (CORECONF)", Work in Progress, Internet-Draft,
draft-ietf-core-comi-18, 23 July 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-core-
comi-18>.
[DEREF-ID] Bormann, C. and C. Amsüss, "The 'dereferenceable
identifier' pattern", Work in Progress, Internet-Draft,
draft-bormann-t2trg-deref-id-03, 2 March 2024,
<https://datatracker.ietf.org/doc/html/draft-bormann-
t2trg-deref-id-03>.
[PYANG] Björklund, M., "An extensible YANG validator and converter
in python", commit fc9a965, May 2024,
<https://github.com/mbj4668/pyang>.
[RFC 6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC 6020, October 2010,
<https://www.rfc-editor.org/info/RFC 6020>.
[RFC 6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC 6241, June 2011,
<https://www.rfc-editor.org/info/RFC 6241>.
[RFC 7224] Bjorklund, M., "IANA Interface Type YANG Module",
RFC 7224, DOI 10.17487/RFC 7224, May 2014,
<https://www.rfc-editor.org/info/RFC 7224>.
[RFC 7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC 7228, May 2014,
<https://www.rfc-editor.org/info/RFC 7228>.
[RFC 7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for
System Management", RFC 7317, DOI 10.17487/RFC 7317, August
2014, <https://www.rfc-editor.org/info/RFC 7317>.
[RFC 8343] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 8343, DOI 10.17487/RFC 8343, March 2018,
<https://www.rfc-editor.org/info/RFC 8343>.
[RFC 8344] Bjorklund, M., "A YANG Data Model for IP Management",
RFC 8344, DOI 10.17487/RFC 8344, March 2018,
<https://www.rfc-editor.org/info/RFC 8344>.
[RFC 8792] Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
"Handling Long Lines in Content of Internet-Drafts and
RFCs", RFC 8792, DOI 10.17487/RFC 8792, June 2020,
<https://www.rfc-editor.org/info/RFC 8792>.
[RFC 9195] Lengyel, B. and B. Claise, "A File Format for YANG
Instance Data", RFC 9195, DOI 10.17487/RFC 9195, February
2022, <https://www.rfc-editor.org/info/RFC 9195>.
[RFC 9254] Veillette, M., Ed., Petrov, I., Ed., Pelov, A., Bormann,
C., and M. Richardson, "Encoding of Data Modeled with YANG
in the Concise Binary Object Representation (CBOR)",
RFC 9254, DOI 10.17487/RFC 9254, July 2022,
<https://www.rfc-editor.org/info/RFC 9254>.
[STD91] Internet Standard 91,
<https://www.rfc-editor.org/info/std91>.
At the time of writing, this STD comprises the following:
Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC 8341, March 2018,
<https://www.rfc-editor.org/info/RFC 8341>.
[YANG-LIBRARY]
Veillette, M., Ed. and I. Petrov, Ed., "Constrained YANG
Module Library", Work in Progress, Internet-Draft, draft-
ietf-core-yang-library-03, 11 January 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-core-
yang-library-03>.
[yangcatalog]
"YANG Catalog", <https://yangcatalog.org>.
Appendix A. ".sid" File Example
The following ".sid" file ('ietf-system@2014-08-06.sid') has been
generated using the following YANG modules:
* 'ietf-system@2014-08-06.yang' (defined in [RFC 7317])
* 'ietf-yang-types@2013-07-15.yang' (defined in [RFC 6991])
* 'ietf-inet-types@2013-07-15.yang' (defined in [RFC 6991])
* 'ietf-netconf-acm@2018-02-14.yang' (defined in [STD91])
* 'iana-crypt-hash@2014-08-06.yang' (defined in [RFC 7317])
For purposes of exposition, per [RFC 8792], line breaks have been
introduced below in some JSON strings that represent overly long
identifiers.
=============== NOTE: '\' line wrapping per RFC 8792 ================
{
"ietf-sid-file:sid-file": {
"module-name": "ietf-system",
"module-revision": "2014-08-06",
"description": "Example '.sid' file",
"dependency-revision": [
{
"module-name": "ietf-yang-types",
"module-revision": "2013-07-15"
},
{
"module-name": "ietf-inet-types",
"module-revision": "2013-07-15"
},
{
"module-name": "ietf-netconf-acm",
"module-revision": "2018-02-14"
},
{
"module-name": "iana-crypt-hash",
"module-revision": "2014-08-06"
}
],
"assignment-range": [
{
"entry-point": "1700",
"size": "100"
}
],
"item": [
{
"namespace": "module",
"identifier": "ietf-system",
"sid": "1700"
},
{
"namespace": "identity",
"identifier": "authentication-method",
"sid": "1701"
},
{
"namespace": "identity",
"identifier": "local-users",
"sid": "1702"
},
{
"namespace": "identity",
"identifier": "radius",
"sid": "1703"
},
{
"namespace": "identity",
"identifier": "radius-authentication-type",
"sid": "1704"
},
{
"namespace": "identity",
"identifier": "radius-chap",
"sid": "1705"
},
{
"namespace": "identity",
"identifier": "radius-pap",
"sid": "1706"
},
{
"namespace": "feature",
"identifier": "authentication",
"sid": "1707"
},
{
"namespace": "feature",
"identifier": "dns-udp-tcp-port",
"sid": "1708"
},
{
"namespace": "feature",
"identifier": "local-users",
"sid": "1709"
},
{
"namespace": "feature",
"identifier": "ntp",
"sid": "1710"
},
{
"namespace": "feature",
"identifier": "ntp-udp-port",
"sid": "1711"
},
{
"namespace": "feature",
"identifier": "radius",
"sid": "1712"
},
{
"namespace": "feature",
"identifier": "radius-authentication",
"sid": "1713"
},
{
"namespace": "feature",
"identifier": "timezone-name",
"sid": "1714"
},
{
"namespace": "data",
"identifier": "/ietf-system:set-current-datetime",
"sid": "1715"
},
{
"namespace": "data",
"identifier": "/ietf-system:set-current-datetime/input",
"sid": "1775"
},
{
"namespace": "data",
"identifier": "/ietf-system:set-current-datetime/input/\
current-datetime",
"sid": "1776"
},
{
"namespace": "data",
"identifier": "/ietf-system:system",
"sid": "1717"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-restart",
"sid": "1718"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-shutdown",
"sid": "1719"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-state",
"sid": "1720"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-state/clock",
"sid": "1721"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-state/clock/boot-datetime\
",
"sid": "1722"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-state/clock/current-\
datetime",
"sid": "1723"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-state/platform",
"sid": "1724"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-state/platform/machine",
"sid": "1725"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-state/platform/os-name",
"sid": "1726"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-state/platform/os-release\
",
"sid": "1727"
},
{
"namespace": "data",
"identifier": "/ietf-system:system-state/platform/os-version\
",
"sid": "1728"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/authentication",
"sid": "1729"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/authentication/user",
"sid": "1730"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/authentication/user-\
authentication-order",
"sid": "1731"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/authentication/user/\
authorized-key",
"sid": "1732"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/authentication/user/\
authorized-key/algorithm",
"sid": "1733"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/authentication/user/\
authorized-key/key-data",
"sid": "1734"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/authentication/user/\
authorized-key/name",
"sid": "1735"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/authentication/user/name",
"sid": "1736"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/authentication/user/\
password",
"sid": "1737"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/clock",
"sid": "1738"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/clock/timezone-name",
"sid": "1739"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/clock/timezone-utc-offset\
",
"sid": "1740"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/contact",
"sid": "1741"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/dns-resolver",
"sid": "1742"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/dns-resolver/options",
"sid": "1743"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/dns-resolver/options/\
attempts",
"sid": "1744"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/dns-resolver/options/\
timeout",
"sid": "1745"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/dns-resolver/search",
"sid": "1746"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/dns-resolver/server",
"sid": "1747"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/dns-resolver/server/name",
"sid": "1748"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/dns-resolver/server/udp-\
and-tcp",
"sid": "1749"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/dns-resolver/server/udp-\
and-tcp/address",
"sid": "1750"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/dns-resolver/server/udp-\
and-tcp/port",
"sid": "1751"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/hostname",
"sid": "1752"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/location",
"sid": "1753"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/ntp",
"sid": "1754"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/ntp/enabled",
"sid": "1755"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/ntp/server",
"sid": "1756"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/ntp/server/association-\
type",
"sid": "1757"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/ntp/server/iburst",
"sid": "1758"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/ntp/server/name",
"sid": "1759"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/ntp/server/prefer",
"sid": "1760"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/ntp/server/udp",
"sid": "1761"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/ntp/server/udp/address",
"sid": "1762"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/ntp/server/udp/port",
"sid": "1763"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius",
"sid": "1764"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius/options",
"sid": "1765"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius/options/attempts",
"sid": "1766"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius/options/timeout",
"sid": "1767"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius/server",
"sid": "1768"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius/server/\
authentication-type",
"sid": "1769"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius/server/name",
"sid": "1770"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius/server/udp",
"sid": "1771"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius/server/udp/address\
",
"sid": "1772"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius/server/udp/\
authentication-port",
"sid": "1773"
},
{
"namespace": "data",
"identifier": "/ietf-system:system/radius/server/udp/shared-\
secret",
"sid": "1774"
}
]
}
}
Figure 3: Example ".sid" File ('ietf-system', with Extra Line Breaks)
Appendix B. SID Autogeneration
The assignment of SIDs to YANG items SHOULD be automated. The
recommended process to assign SIDs is as follows:
1. A tool extracts the different items defined for a specific YANG
module.
2. The list of items is sorted in alphabetical order. 'namespace'
entries are sorted in descending order, and 'identifier' entries
are sorted in ascending order. The 'namespace' and 'identifier'
formats are described in the YANG module 'ietf-sid-file' defined
in Section 4.
3. SIDs are assigned sequentially from the entry point up to the
size of the registered SID range. This approach is recommended
to minimize the serialization overhead, especially when the delta
between a reference SID and the current SID is used by protocols
aiming to reduce message size.
4. If the number of items exceeds the SID range(s) allocated to a
YANG module, an extra range is added for subsequent assignments.
5. The 'dependency-revision' list item should reflect the revision
numbers of each YANG module that the YANG module imports at the
moment of file generation.
When updating a YANG module that is in active use, the existing SID
assignments are maintained. (In contrast, when evolving an early
version of an Internet-Draft that has not yet been adopted by a
community of developers, SID assignments are often better done from
scratch after a revision.) If the name of a schema node changes but
the data remain structurally and semantically similar to what was
previously available under an old name, the SID that was used for the
old name MAY continue to be used for the new name. If the meaning of
an item changes, a new SID MAY be assigned to it; this is
particularly useful for allowing the new SID to identify the new
structure or semantics of the item. If the YANG data type changes in
a new revision of a published module such that the resulting CBOR
encoding is changed, then implementations will be aided significantly
if a new SID is assigned. Note that these decisions are generally at
the discretion of the YANG module author, who should decide if the
benefits of a manual intervention are worth the deviation from
automatic assignment.
In the case of an update to an existing ".sid" file, an additional
step is needed that increments the ".sid" file version number. If
there was no version number in the previous version of the ".sid"
file, 0 is assumed to be the version number of the old version of the
".sid" file and the version number is 1 for the new ".sid" file.
Apart from that, changes to ".sid" files can also be automated using
the same method as that described above, except that in step #3,
previous SID assignments are kept, only previously unassigned YANG
items are processed, and these are assigned previously unassigned
SIDs. Already-existing items in the ".sid" file should not be given
new SIDs.
Note that ".sid" file versions are specific to a YANG module
revision. For each new YANG module or each new revision of an
existing YANG module, the version number of the initial ".sid" file
either (1) should be 0 or (2) should not be present.
Note also that RPC or action "input" and "output" YANG items MUST
always be assigned SIDs even if they don't contain further YANG
items. The reason for this requirement is that other modules can
augment the given module and those SIDs might be necessary.
Appendix C. ".sid" File Lifecycle
Before assigning SIDs to their YANG modules, YANG module authors must
acquire a SID range from a registry of YANG-SID Ranges. If the YANG
module is part of an IETF Internet-Draft or RFC, the SID range needs
to be acquired from the "IETF YANG-SID Ranges" registry as defined in
Section 6.4. For the other YANG modules, the authors can choose to
acquire a SID range from any registry of YANG-SID Ranges.
Once the SID range is acquired, owners can use it to generate one or
more ".sid" files for their YANG module or modules. It is
recommended to leave some unallocated SIDs following the allocated
range in each ".sid" file in order to allow better evolution of the
owners' YANG modules in the future. Generation of ".sid" files
should be performed using an automated tool. Note that ".sid" files
can only be generated for YANG modules and not for submodules.
C.1. ".sid" File Creation
The following activity diagram summarizes the creation of a YANG
module and its associated ".sid" file.
+---------------+
o | Creation of a |
-+- -->| YANG module |
/ \ +------+--------+
|
v
.-------------.
/ Standardized \ yes
\ YANG module? /------------+
'-----+-------' |
| no |
v v
.-------------. +---------------+
+--> / Constrained \ yes | SID range |
| \ application? /---->| registration |<--------+
| '-----+-------' +------+--------+ |
| | no | |
| v v |
| +---------------+ +---------------+ |
+----+ YANG module | | SID subrange | |
| update | | assignment |<---------+
+---------------+ +-------+-------+ |
| |
v |
+---------------+ +------+------+
| ".sid" file | | Rework YANG |
| generation | | module |
+-------+-------+ +-------------+
| ^
v |
.----------. yes |
/ Work-in- \ ------------+
\ progress? /
'----+-----'
| no
v
.-------------.
/ RFC \ no
\ publication? /--------------+
'------+------' |
yes | |
v v
+---------------+ +---------------+
| IANA | | Third-party |
| registration | | registration |
+-------+-------+ +-------+-------+
| |
+------------------------+
v
[DONE]
Figure 4: SID Lifecycle
C.2. ".sid" File Update
The following activity diagram summarizes the update of a YANG module
and its associated ".sid" file.
+--------------------+
o | Update of the |
-+- -->| YANG module, its |
/ \ | include(s), or its |
| import(s) |
+------+-------------+
|
v
.-------------.
/ New items \ yes
\ created? /------+
'------+------' |
| no v
| .-------------. +----------------+
| / SID range \ yes | Extra subrange |
| \ exhausted? /---->| assignment |
| '------+------' +-------+--------+
| | no |
| +---------------------+
| |
| v
| +---------------+
| | ".sid" file |
| | update based |
| | on previous |
| | ".sid" file |
| +-------+-------+
| |
| v
| .-------------. +---------------+
| / Publicly \ yes | YANG module |
| \ available? /---->| registration |
| '------+------' +-------+-------+
| | no |
+--------------+---------------------+
|
v
[DONE]
Figure 5: YANG and ".sid" File Update
Appendix D. Keeping a ".sid" File in a YANG Instance Data File
[RFC 9195] defines a format for "YANG instance data". This
essentially leads to an encapsulation of the instance data within
some metadata envelope.
If a ".sid" file needs to be stored in a YANG instance data file,
this can be achieved by embedding the value of the ".sid" file as the
value of the content-data member in the following template and
copying over the second-level members as indicated with the angle
brackets:
{
"ietf-yang-instance-data:instance-data-set": {
"name": "<module-name>@<module-revision>.sid",
"description": ["<description>"],
"content-schema": {
"module": "ietf-sid-file@2024-06-17"
},
"content-data": { <replace this object>
"ietf-sid-file:sid-file" : {
"module-name": ...
}
}
}
}
Acknowledgments
The authors would like to thank Andy Bierman, Abhinav Somaraju, Peter
van der Stok, Laurent Toutain, and Randy Turner for their help during
the development of this document and their useful comments during the
review process. Special thanks go to the IESG members who supplied
very useful comments during the IESG processing phase, in particular
to Benjamin Kaduk and Rob Wilton, and to Francesca Palombini as
responsible AD.
Contributors
Andy Bierman
YumaWorks
685 Cochran St.
Suite #160
Simi Valley, CA 93065
United States of America
Email: andy@yumaworks.com
Authors' Addresses
Michel Veillette (editor)
Trilliant Networks Inc.
610 Rue du Luxembourg
Granby Quebec J2J 2V2
Canada
Phone: +1-450-375-0556
Email: michel.veillette@trilliant.com
Alexander Pelov (editor)
IMT Atlantique
2 rue de la Châtaigneraie
35510 Cesson-Sévigné Cedex
France
Email: alexander.pelov@imt-atlantique.fr
Ivaylo Petrov (editor)
Google Switzerland GmbH
Brandschenkestrasse 110
CH-8002 Zurich
Switzerland
Email: ivaylopetrov@google.com
Carsten Bormann
Universität Bremen TZI
Postfach 330440
D-28359 Bremen
Germany
Phone: +49-421-218-63921
Email: cabo@tzi.org
Michael Richardson
Sandelman Software Works
Canada
Email: mcr+ietf@sandelman.ca
RFC TOTAL SIZE: 92938 bytes
PUBLICATION DATE: Thursday, August 1st, 2024
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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