file "ietf-yang-instance-data@2022-02-17.yang"
module ietf-yang-instance-data {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data";
prefix yid;
import ietf-yang-structure-ext {
prefix sx;
reference
"RFC 8791: YANG Data Structure Extensions";
}
import ietf-datastores {
prefix ds;
reference
"RFC 8342: Network Management Datastore Architecture (NMDA)";
}
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-yang-types {
prefix yang;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-netconf-with-defaults {
prefix ncwd;
reference
"RFC 6243: With-defaults Capability for NETCONF";
}
organization
"IETF NETMOD Working Group";
contact
"WG Web:
WG List:
Author: Balazs Lengyel
Author: Benoit Claise
";
description
"The module defines the structure and content of YANG
instance data sets.
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) 2022 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 9195
(https://www.rfc-editor.org/info/rfc9195); see the RFC itself
for full legal notices.";
revision 2022-02-17 {
description
"Initial revision.";
reference
"RFC 9195: YANG Instance Data File Format";
}
typedef module-with-revision-date {
type string {
pattern '[a-zA-Z_][a-zA-Z0-9\-_.]*'
+ '(@\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1]))?';
pattern '.|..|[^xX].*|.[^mM].*|..[^lL].*';
}
description
"A type defining a module name and an optional revision
date, e.g., ietf-yang-library@2019-01-04.";
}
sx:structure instance-data-set {
description
"A data structure to define a format for YANG instance
data. The majority of the YANG nodes provides metadata
about the instance data; the instance data itself is
contained only in the 'content-data' node.";
leaf name {
type string;
description
"An arbitrary name for the YANG instance data set. This
value is primarily used for descriptive purposes. However,
when the instance data set is saved to a file, then the
filename MUST encode the name's value per Section 2
of RFC 9195.";
}
leaf format-version {
type string {
pattern '\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1])';
}
default "2022-01-20";
description
"The 'revision' of the 'ietf-yang-instance-data' module
used to encode this 'instance-data-set'.";
}
leaf includes-defaults {
type ncwd:with-defaults-mode;
default "report-all";
description
"Indicates how data nodes with default values are
represented for all data nodes contained in the
instance-data-set.
It uses the same definitions as per Section 3 of RFC 6243
but applied in the context of an instance data file rather
than a NETCONF request using the
parameter.
For JSON files, the encoding of the 'report-all-tagged'
option is as defined in Section 4.8.9 of RFC 8040.";
reference
"RFC 6243: With-defaults Capability for NETCONF";
}
container content-schema {
description
"The content schema (i.e., YANG modules) used to create
the instance data set.
If not present, the user needs to obtain the information
through external documents.";
choice content-schema-spec {
description
"Specification of the content-schema.";
case simplified-inline {
leaf-list module {
type module-with-revision-date;
min-elements 1;
description
"The list of content-defining YANG modules.
The value SHALL start with the module name.
If the module contains a revision statement, the
revision date SHALL be included in the leaf-list
entry, e.g., ietf-yang-library@2019-01-04.
Usage of this leaf-list implies the modules are
used without any deviations and with all features
supported. Multiple revisions of the same module
MUST NOT be specified.";
}
}
case inline {
anydata inline-yang-library {
mandatory true;
description
"Instance data corresponding to the
ietf-yang-library@2019-01-04 defining
the set of content-defining YANG modules for
this instance-data-set.";
}
}
case uri {
leaf same-schema-as-file {
type inet:uri;
description
"A reference to another YANG instance data file.
This instance data file uses the same
content schema as the referenced file.
Referenced files using the 'inline' or the
'simplified-inline' methods MUST be supported.
Referenced files using the 'URI method' MAY be
supported.
The URL schemes 'file://' and 'https://' MUST
be supported; other schemes MAY also be
supported.";
}
}
}
}
leaf-list description {
type string;
description
"Description of the instance data set.";
}
leaf contact {
type string;
description
"Contact information for the person or
organization to whom queries concerning this
instance data set should be sent.";
}
leaf organization {
type string;
description
"Organization responsible for the instance
data set.";
}
leaf datastore {
type ds:datastore-ref;
description
"The identity of the datastore with which the
instance data set is associated, e.g., the datastore from
where the data was read, the datastore into which the data
may be loaded, or the datastore that is being documented.
If a single specific datastore cannot be specified, the
leaf MUST be absent.
If this leaf is absent, then the datastore to which the
instance data belongs is unspecified.";
}
list revision {
key "date";
description
"Instance data sets that are produced as
a result of some sort of specification or design effort
SHOULD have at least one revision entry. For every
published editorial change, a new unique revision SHOULD
be added in front of the revisions sequence so that all
revisions are in reverse chronological order.
In cases of instance data sets that are read from
or produced by a server or otherwise subject to
frequent updates or changes, revision
SHOULD NOT be present.";
leaf date {
type string {
pattern '\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1])';
}
description
"Specifies the date the instance data set
was last modified. Formatted as YYYY-MM-DD.";
}
leaf description {
type string;
description
"Description of this revision of the instance data set.";
}
}
leaf timestamp {
type yang:date-and-time;
description
"The date and time when the instance data set
was last modified.
In cases of instance data sets that are read from or
produced by a server or otherwise subject to frequent
updates or changes, the timestamp SHOULD be present.
If both a revision list entry and timestamp are present,
the timestamp SHOULD contain the same date as the
latest revision statement.";
}
anydata content-data {
description
"Contains the real instance data.
The data MUST conform to the relevant YANG modules
specified either in the content-schema or in some other
implementation-specific manner.";
}
}
}
4. Security Considerations
The YANG module defined in this document only defines a wrapper
structure specifying a format and a metadata header for YANG instance
data defined by the content-schema. Because of this, the security
considerations template for YANG models in Section 3.7.1 of [RFC8407]
is not followed. The instance data is designed to be accessed as a
stored file or over any file access method or protocol.
The document does not specify any method to influence the behavior of
a server.
The header part is usually not security sensitive; however, sensitive
information may be included, in which case it needs to be handled
securely, as mentioned below. Information to consider includes:
* If the URI method is used for specification of the content-schema
and the URI includes a userinfo subcomponent
* Any description text
The content part may contain sensitive data. The security
sensitivity of this data is completely dependent on the content-
schema. Depending on the nature of the instance data, instance data
files MAY need to be handled securely. The same kind of handling
should be applied to this file at rest and in transit that would be
needed for the result of a read operation returning the same data.
These in-transit protection mechanisms will also mitigate integrity
issues when transporting the file.
Instance data files should be protected against modification or
unauthorized access using normal file-handling mechanisms. When
copying the original files or providing file access for additional
users, care should be taken not to reveal information
unintentionally.
If the URI method is used for specification of the content-schema,
there is a risk that the config schema section in the referenced YANG
instance data file may be altered maliciously or even as part of its
normal handling. In this case, the content-schema might differ from
the one expected. Protecting the integrity and stability of the
referenced file should be ensured.
5. IANA Considerations
This document registers one URI and one YANG module.
5.1. URI Registration
This document registers the following URI in the "IETF XML Registry"
[RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-yang-instance-data
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
5.2. YANG Module Name Registration
This document registers the following YANG module in the "YANG Module
Names" registry [RFC6020]:
Name: ietf-yang-instance-data
Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-instance-data
Prefix: yid
Reference: RFC 9195
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
.
[RFC6243] Bierman, A. and B. Lengyel, "With-defaults Capability for
NETCONF", RFC 6243, DOI 10.17487/RFC6243, June 2011,
.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
.
[RFC7952] Lhotka, L., "Defining and Using Metadata with YANG",
RFC 7952, DOI 10.17487/RFC7952, August 2016,
.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, .
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
.
[RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
and R. Wilton, "YANG Library", RFC 8525,
DOI 10.17487/RFC8525, March 2019,
.
[RFC8526] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "NETCONF Extensions to Support the Network
Management Datastore Architecture", RFC 8526,
DOI 10.17487/RFC8526, March 2019,
.
[RFC8527] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "RESTCONF Extensions to Support the Network
Management Datastore Architecture", RFC 8527,
DOI 10.17487/RFC8527, March 2019,
.
[RFC8791] Bierman, A., Björklund, M., and K. Watsen, "YANG Data
Structure Extensions", RFC 8791, DOI 10.17487/RFC8791,
June 2020, .
6.2. Informative References
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
.
[RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
Documents Containing YANG Data Models", BCP 216, RFC 8407,
DOI 10.17487/RFC8407, October 2018,
.
[RFC8632] Vallin, S. and M. Bjorklund, "A YANG Data Model for Alarm
Management", RFC 8632, DOI 10.17487/RFC8632, September
2019, .
[RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications
for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
September 2019, .
[RFC8792] Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
"Handling Long Lines in Content of Internet-Drafts and
RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
.
[RFC8808] Wu, Q., Lengyel, B., and Y. Niu, "A YANG Data Model for
Factory Default Settings", RFC 8808, DOI 10.17487/RFC8808,
August 2020, .
Appendix A. Backwards Compatibility
The concept of "backwards compatibility" and what changes are
backwards compatible are not defined for instance data sets as they
are highly dependent on the specific use case and the content-schema.
In case of "instance data sets" that are the result of design or
specification activity, some changes that may be good to avoid are
listed below.
YANG uses the concept of managed entities identified by key values;
if the connection between the represented entity and the key value is
not preserved during an update, this may lead to the following
problems.
* If the key value of a list entry that represents the same managed
entity as before is changed, the user may mistakenly identify the
list entry as new.
* If the meaning of a list entry is changed but the key values are
not (e.g., redefining an alarm-type but not changing its alarm-
type-id), the change may not be noticed.
* If the key value of a previously removed list entry is reused for
a different entity, the change may be misinterpreted as
reintroducing the previous entity.
Appendix B. Detailed Use Cases
This section is non-normative.
B.1. Use Case 1: Early Documentation of Server Capabilities
A server has a number of server capabilities that are defined in YANG
modules and can be retrieved from the server using protocols like
NETCONF or RESTCONF. Server capabilities include:
* data defined in "ietf-yang-library": YANG modules, submodules,
features, deviations, schema-mounts, and datastores supported
([RFC8525]).
* alarms supported ([RFC8632]).
* data nodes and subtrees that support or do not support on-change
notifications ([RFC8641]).
* netconf-capabilities in ietf-netconf-monitoring.
While it is good practice to allow a client to query these
capabilities from the live server, that is often not possible.
Often when a network node is released, an associated Network
Management System (NMS) is also released with it. The NMS depends on
the capabilities of the server. During NMS implementation,
information about server capabilities is needed. If the information
is unavailable early in some offline document but only as instance
data from the live network node, the NMS implementation will be
delayed because it has to wait until the network node is ready.
Also, assuming that all NMS implementors will have correctly
configured network nodes from which data can be retrieved is a very
expensive proposition. (An NMS may handle dozens of node types.)
Network operators often build their own homegrown NMS systems that
need to be integrated with a vendor's network node. The operator
needs to know the network node's server capabilities in order to do
this. Moreover, the network operator's decision to buy a vendor's
product may even be influenced by the network node's Operations,
Administration, and Maintenance (OAM) feature set documented as the
server's capabilities.
Beside NMS implementors, system integrators and many others also need
the same information early. Examples could be model-driven testing,
generating documentation, etc.
Most server capabilities are relatively stable and change only during
upgrade or due to licensing or the addition or removal of hardware.
They are usually defined by a vendor at design time, before the
product is released. It is feasible and advantageous to define and
document them early, e.g., in a YANG instance data file.
It is anticipated that a separate IETF document will define in detail
how and which set of server capabilities should be documented.
B.2. Use Case 2: Preloading Data
There are parts of the configuration that must be fully configurable
by the operator. However, a simple default configuration often will
be sufficient.
One example is access control groups/roles and related rules. While
a sophisticated operator may define dozens of different groups, often
a basic (read-only operator, read-write system administrator,
security-administrator) triplet will be enough. Vendors will often
provide such default configuration data to make device configuration
easier for an operator.
The device vendor may define a set of default groups (/nacm:nacm/
groups) and rules for these groups to access specific parts of the
common models (/nacm:nacm/rule-list/rule).
YANG instance data files can be used to document and/or preload the
default configuration.
B.3. Use Case 3: Documenting Factory Default Settings
Nearly every server has a factory default configuration. If the
system is really badly misconfigured or if the current configuration
is to be abandoned, the system can be reset to the default factory
configuration.
YANG instance data can be used to document the factory default
configuration. See [RFC8808].
Acknowledgments
For their valuable comments, discussions, and feedback, we wish to
acknowledge Andy Bierman, Juergen Schoenwaelder, Rob Wilton, Joe
Clarke, Kent Watsen, Martin Bjorklund, Ladislav Lhotka, Qin Wu, and
other members of the Netmod Working Group.
Authors' Addresses
Balazs Lengyel
Ericsson
Budapest
Magyar Tudosok korutja 11
1117
Hungary
Email: balazs.lengyel@ericsson.com
Benoit Claise
Huawei
Email: benoit.claise@huawei.com
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