Augmentaiton Addition into the IETF-YANG-LibraryHuaweiTownsend Street, George's CourtDublinIrelandzephyre888@gmail.comHuaweiBelgiumbenoit.claise@huawei.com
OPS
OPSAWGThis document augments the ietf-yang-library in [RFC8525] to provide the augmentation list. It facilitates the process of obtaining the entire dependencies of YANG model, by directly querying the server YANG module.
Discussion VenuesSource for this draft and an issue tracker can be found at .The YANG library specifies a YANG module that provides
the information about the YANG models and datastores to facilitate a client
application to fully utilize and understand the YANG data modelling language.
To know the YANG dependencies, has defined and provided the submodule list and the YANG modules deviation list. However, the YANG modules augmentation list is not provided.According to , both augmentations and deviations are
defining contents external to the model, but applying internally for the model.
Therefore, it is important to know the augmentation and deviation as they are
dependencies of the model, but it is also difficult because they are defined externally.
When we try to use the ietf-yang-library in to obtain the reverse
dependencies (augmentations and deviations), the augmentation is missing. However, the
augmentation and the deviation work similarly as YANG modules dependency, therefore it is
resonable to document them the same way in the IETF YANG library. Besides, it will be
easier to determine the reverse dependency if the augmentation is directly available,
through a GET request into this new YANG model.Therefore, this draft augments the ietf-yang-library to include the YANG modules augmentated information.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 when, and only
when, they appear in all capitals, as shown here.The terminology from is used in this documentTree diagrams in this document use the notation defined in
.When using one YANG model, it is important to make sure that all its dependencies
are presented. In there are four dependencies for one YANG mode:
Import: the "import" statement allows a module or submodule to reference
definitions defined in other modules.
Include: the "include" statement is used in a module to identify each
submodule that belongs to it.
Augmentation: the "augment" statement defines the location in the data model
hierarchy where additional nodes are inserted
Deviation: the "deviation" statement defines a hierarchy of a module that the
server does not implement faithfully.
The import and include are direct dependencies while the augmentation and deviation are reverse dependencies. To know a specific YANG model's direct dependencies, we can parse this YANG model as the dependencies are directly specified (import and include statements"). As for the reverse dependencies, since they are defined externally, we cannot parse the YANG model itself. Among all the methods for getting reverse dependency, getting the ietf-yang-library content is one of the most convenient way. However, it only provides the deviation list, not the augmentation list. It is reasonable to update it with the augmentation list, since both augmentation and deviation have similar behavior (both are invisible to the original model). A noticable difference between deviations and augmentations is that the deviations are required to understand the API contract between the client and the server.
Here is a typical use case: as the demand arises for YANG-based telemetry , there is a need for real-time knowledge of a specific YANG model's dependency list, when a specific YANG-Push message is received. The alternative, for a YANG-push receiver, to collect and store the entire module set for every single server who could be streaming data, is not always practical. Indeed, it's time consuming to request all YANG modules from the server.In an open-sourced project covering Support of Versioning in YANG Notifications Subscription,
Support of Network Observation Timestamping in YANG Notifications,
among others, the purpose is to provide adequate information in the YANG push notification so that when it is received, the model and its dependency can be parsed and found automatically from the vantage point. Currently, the method used for finding model's reverse dependency is get-all-schemas, that is to retrieve all YANG modules from the device to the client's disk to enable the client fully understand the YANG model relationship. This process is heavy because dependencies are recursive; each dependency module could have another set of dependencies. Considering the telemetry real-time aspects, this extra delay in processing the dependencies through get-all-schemas is a burden.
The YANG module in this draft is proposed to solve the above problem. It can make the process of discovering the augmentation easier.
This YANG module augments the ietf-yang-library module with the augmentation in the "yang-library/module-set". Note that this module only augments the ietf-yang-library defined in . At the time of writing this document, most router vendors support , a previous revision of the IETF-YANG-LIBRARY YANG module; The module that augments is provided in the appendix A.
The following is the YANG tree diagram for model ietf-yang-library-augmentation. /yanglib:yang-library/module-set/module/name
]]>
The following is the YANG tree diagram for the ietf-yang-
library-augmentation augmentation within the ietf-yang-library,
including the RPCs and notifications.
../../module/name
| | | +--ro yanglib-aug:augmentation* -> /yanglib:yang-library/module-set/module/name
| | +--ro import-only-module* [name revision]
| | +--ro name yang:yang-identifier
| | +--ro revision union
| | +--ro namespace inet:uri
| | +--ro location* inet:uri
| | +--ro submodule* [name]
| | +--ro name yang:yang-identifier
| | +--ro revision? revision-identifier
| | +--ro location* inet:uri
| +--ro schema* [name]
| | +--ro name string
| | +--ro module-set* -> ../../module-set/name
| +--ro datastore* [name]
| | +--ro name ds:datastore-ref
| | +--ro schema -> ../../schema/name
| +--ro content-id string
x--ro modules-state
x--ro module-set-id string
x--ro module* [name revision]
x--ro name yang:yang-identifier
x--ro revision union
+--ro schema? inet:uri
x--ro namespace inet:uri
x--ro feature* yang:yang-identifier
x--ro deviation* [name revision]
| x--ro name yang:yang-identifier
| x--ro revision union
x--ro conformance-type enumeration
x--ro submodule* [name revision]
x--ro name yang:yang-identifier
x--ro revision union
+--ro schema? inet:uri
notifications:
+---n yang-library-update
| +--ro content-id -> /yang-library/content-id
x---n yang-library-change
x--ro module-set-id -> /modules-state/module-set-id
]]>The YANG module augments the ietf-yang-library YANG module defined in . file "ietf-yang-library-augmentation@2023-10-27.yang"
module ietf-yang-library-augmentation {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-library-augmentation";
prefix yanglib-aug;
import ietf-yang-library {
prefix yanglib;
reference
"RFC 8525: YANG library";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web:
WG List:
Author: Zhuoyao Lin
Benoit Claise
";
description
"This module augments the ietf-yang-library defined in [RFC8525] to provide the augmentation list, in order to give sufficient information about the YANG models reverse dependency. It facilitates the process of obtaining the entire dependencies of YANG model.";
revision 2023-10-27 {
description
"Added list augmentation in yang-library/module-set/module to
make the module store the entire reverse dependency information
(augmentation and deviation).";
reference
"RFC XXXX: Support of augmentation in ietf-yang-library";
}
augment "/yanglib:yang-library/yanglib:module-set/yanglib:module" {
description
"Augment the augmentation from module info with the module-augmentation grouping" ;
uses yanglib-aug:module-augmentation;
}
/*
* Groupings
*/
grouping module-augmentation {
description
"This grouping defines a leaf-list that contains the augmentation list.";
leaf-list augmentation {
type leafref {
path "/yanglib:yang-library/yanglib:module-set/yanglib:module/yanglib:name";
}
description
"List of all YANG augmentation modules used by this server to
modify the conformance of the module associated with this
entry. Note that the same module can be used for augmentation
for multiple modules, so the same entry MAY appear within
multiple 'module' entries.
This reference MUST NOT (directly or indirectly)
refer to the module being augmented.
Robust clients may want to make sure that they handle a
situation where a module augments itself (directly or
indirectly) gracefully.";
}
}
}
]]>Security ConsiderationsTBCIANA ConsiderationsThis document has no actions for IANA.The following is the YANG tree diagram for augmenting RFC7895. /yanglib:yang-library/module-set/module/name
augment /yanglib:modules-state/yanglib:module:
x--ro augmentation* [name revision]
+--ro name -> /yanglib:modules-state/module/name
+--ro revision -> /yanglib:modules-state/module/revision
]]>The following is the full YANG tree diagram for ietf-yang-library with augmentation to RFC7895. ../../module/name
| | | +--ro yanglib-aug:augmentation* -> /yanglib:yang-library/module-set/module/name
| | +--ro import-only-module* [name revision]
| | +--ro name yang:yang-identifier
| | +--ro revision union
| | +--ro namespace inet:uri
| | +--ro location* inet:uri
| | +--ro submodule* [name]
| | +--ro name yang:yang-identifier
| | +--ro revision? revision-identifier
| | +--ro location* inet:uri
| +--ro schema* [name]
| | +--ro name string
| | +--ro module-set* -> ../../module-set/name
| +--ro datastore* [name]
| | +--ro name ds:datastore-ref
| | +--ro schema -> ../../schema/name
| +--ro content-id string
x--ro modules-state
x--ro module-set-id string
x--ro module* [name revision]
x--ro name yang:yang-identifier
x--ro revision union
+--ro schema? inet:uri
x--ro namespace inet:uri
x--ro feature* yang:yang-identifier
x--ro deviation* [name revision]
| x--ro name yang:yang-identifier
| x--ro revision union
x--ro conformance-type enumeration
x--ro submodule* [name revision]
| x--ro name yang:yang-identifier
| x--ro revision union
| +--ro schema? inet:uri
x--ro yanglib-aug:augmentation* [name revision]
+--ro yanglib-aug:name -> /yanglib:modules-state/module/name
+--ro yanglib-aug:revision -> /yanglib:modules-state/module/revision
notifications:
+---n yang-library-update
| +--ro content-id -> /yang-library/content-id
x---n yang-library-change
x--ro module-set-id -> /modules-state/module-set-id
]]>The YANG module that augments the ietf-yang-library RFC7895. file "ietf-yang-library-rfc7895-augmentation@2023-10-27.yang"
module ietf-yang-library-rfc7895-augmentation {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-library-rfc7895-augmentation";
prefix yanglib-aug;
import ietf-yang-library {
prefix yanglib;
revision-date 2016-06-21;
reference
"RFC 8525: YANG library";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web:
WG List:
Author: Zhuoyao Lin
Benoit Claise
";
description
"This module augments the ietf-yang-library defined in [RFC8525] to provide not only the deviation list, but also the augmentation list, in order to give sufficient information about the YANG models reverse dependency. It facilitates the process of obtaining the entire dependencies of YANG model.";
revision 2023-10-27 {
description
"Added list augmentation in yang-library/module-set/module to
make the module store the entire reverse dependency information
(augmentation and deviation).";
reference
"RFC XXXX: Support of augmentation in ietf-yang-library";
}
augment "/yanglib:yang-library/yanglib:module-set/yanglib:module" {
description
"Augment the augmentation from module info with the module-augmentation grouping" ;
uses yanglib-aug:module-augmentation;
}
augment "/yanglib:modules-state/yanglib:module" {
description
"Augment the augmentation from module info with the module-augmentation grouping" ;
uses yanglib-aug:module-state-augmentation;
}
/*
* Groupings
*/
grouping module-augmentation {
description
"This grouping defines a leaf-list that contains the augmentation list.";
leaf-list augmentation {
type leafref {
path "/yanglib:yang-library/yanglib:module-set/yanglib:module/yanglib:name";
}
description
"List of all YANG augmentation modules used by this server to
modify the conformance of the module associated with this
entry. Note that the same module can be used for augmentation
for multiple modules, so the same entry MAY appear within
multiple 'module' entries.
This reference MUST NOT (directly or indirectly)
refer to the module being augmented.
Robust clients may want to make sure that they handle a
situation where a module augments itself (directly or
indirectly) gracefully.";
}
}
grouping module-state-augmentation {
description
"This grouping defines a list with keys being the module
name and revison. The list contains the augmentation list.";
list augmentation {
key "name revision";
status deprecated;
description
"List of YANG augmentation module names and revisions
used by this server to modify the conformance of
the module associated with this entry. Note that
the same module can be used for augmentations for
multiple modules, so the same entry MAY appear
within multiple 'module' entries.
The augmentation module MUST be present in the 'module'
list, with the same name and revision values.
The 'conformance-type' value will be 'implement' for
the augmentation module.";
leaf name {
type leafref {
path "/yanglib:modules-state/yanglib:module/yanglib:name";
}
}
leaf revision {
type leafref {
path "/yanglib:modules-state/yanglib:module/yanglib:revision";
}
}
}
}
}
]]>ContributorsThe following people all contributed to creating this document:AcknowledgementsThanks to xx for their reviews and comments.