draft-ietf-netmod-yang-tree-diagrams-01.txt   draft-ietf-netmod-yang-tree-diagrams-02.txt 
Network Working Group M. Bjorklund Network Working Group M. Bjorklund
Internet-Draft Tail-f Systems Internet-Draft Tail-f Systems
Intended status: Standards Track L. Berger, Ed. Intended status: Standards Track L. Berger, Ed.
Expires: December 31, 2017 LabN Consulting, L.L.C. Expires: April 28, 2018 LabN Consulting, L.L.C.
June 29, 2017 October 25, 2017
YANG Tree Diagrams YANG Tree Diagrams
draft-ietf-netmod-yang-tree-diagrams-01 draft-ietf-netmod-yang-tree-diagrams-02
Abstract Abstract
This document captures the current syntax used in YANG module Tree This document captures the current syntax used in YANG module Tree
Diagrams. The purpose of the document is to provide a single Diagrams. The purpose of the document is to provide a single
location for this definition. This syntax may be updated from time location for this definition. This syntax may be updated from time
to time based on the evolution of the YANG language. to time based on the evolution of the YANG language.
Status of This Memo Status of This Memo
skipping to change at page 1, line 34 skipping to change at page 1, line 34
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 31, 2017. This Internet-Draft will expire on April 28, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Tree Diagram Syntax . . . . . . . . . . . . . . . . . . . . . 3 2. Tree Diagram Syntax . . . . . . . . . . . . . . . . . . . . . 3
2.1. Submodules . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Submodules . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Groupings . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Groupings . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Collapsed Node Representation . . . . . . . . . . . . . . 4 2.3. yang-data . . . . . . . . . . . . . . . . . . . . . . . . 5
2.4. Node Representation . . . . . . . . . . . . . . . . . . . 4 2.4. Collapsed Node Representation . . . . . . . . . . . . . . 5
2.5. Extensions . . . . . . . . . . . . . . . . . . . . . . . 5 2.5. Comments . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Usage Guidelines For RFCs . . . . . . . . . . . . . . . . . . 5 2.6. Node Representation . . . . . . . . . . . . . . . . . . . 5
3.1. Wrapping Long Lines . . . . . . . . . . . . . . . . . . . 6 3. Usage Guidelines For RFCs . . . . . . . . . . . . . . . . . . 6
4. YANG Schema Mount Tree Diagrams . . . . . . . . . . . . . . . 6 3.1. Wrapping Long Lines . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 3.2. Long Diagrams . . . . . . . . . . . . . . . . . . . . . . 7
6. Informative References . . . . . . . . . . . . . . . . . . . 7 4. YANG Schema Mount Tree Diagrams . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 4.1. Representation of Instance Data Trees . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. Informative References . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
YANG Tree Diagrams were first published in [RFC7223]. Such diagrams YANG Tree Diagrams were first published in [RFC7223]. Such diagrams
are commonly used to provided a simplified graphical representation are commonly used to provided a simplified graphical representation
of a data model and can be automatically generated via tools such as of a data model and can be automatically generated via tools such as
"pyang". (See <https://github.com/mbj4668/pyang>). This document "pyang". (See <https://github.com/mbj4668/pyang>). This document
provides the syntax used in YANG Tree Diagrams. It is expected that provides the syntax used in YANG Tree Diagrams. It is expected that
this document will be updated or replaced as changes to the YANG this document will be updated or replaced as changes to the YANG
language, see [RFC7950], necessitate. language, see [RFC7950], necessitate.
skipping to change at page 2, line 50 skipping to change at page 3, line 5
portion of which follows: portion of which follows:
+--rw interfaces +--rw interfaces
| +--rw interface* [name] | +--rw interface* [name]
| +--rw name string | +--rw name string
| +--rw description? string | +--rw description? string
| +--rw type identityref | +--rw type identityref
| +--rw enabled? boolean | +--rw enabled? boolean
| +--rw link-up-down-trap-enable? enumeration | +--rw link-up-down-trap-enable? enumeration
The remainder of this document contains YANG Tree Diagram syntax
based on output from pyang version 1.7.1.
2. Tree Diagram Syntax 2. Tree Diagram Syntax
This section provides the meaning of the symbols used in YANG Tree This section provides the meaning of the symbols used in YANG Tree
diagrams. diagrams.
A full tree diagram of a module represents all elements. It includes A full tree diagram of a module represents all elements. It includes
the name of the module and sections for top level module statements the name of the module and sections for top level module statements
(typically containers), augmentations, rpcs and notifications all (typically containers), augmentations, rpcs and notifications all
identified under a module statement. Module trees may be included in identified under a module statement. Module trees may be included in
a document as a whole, by one or more sections, or even subsets of a document as a whole, by one or more sections, or even subsets of
nodes. nodes.
A module is identified by "module:" followed the module-name. Top A module is identified by "module:" followed the module-name. This
level module statements are listed immediately following, offset by 4 is followed by one or more sections, in order:
spaces. Augmentations are listed next, offset by 2 spaces and
identified by the keyword "augment" followed by the augment target 1. The top-level data nodes defined in the module, offset by 4
node and a colon (':') character. This is followed by, RPCs which spaces.
are identified by "rpcs:" and are also offset by 2 spaces.
Notifications are last and are identified by "notifications:" and are 2. Augmentations, offset by 2 spaces and identified by the keyword
also offset by 2 spaces. "augment" followed by the augment target node and a colon (":")
character.
3. RPCs, offset by 2 spaces and identified by "rpcs:".
4. Notifications, offset by 2 spaces and identified by
"notifications:".
5. Groupings, offset by 2 spaces, and identified by the keyword
"grouping" followed by the name of the grouping and a colon (":")
character.
6. yang-data, offset by 2 spaces, and identified by the keyword
"yang-data" followed by the name of the yang-data structure and a
colon (":") character.
The relative organization of each section is provided using a text- The relative organization of each section is provided using a text-
based format that is typical of a file system directory tree display based format that is typical of a file system directory tree display
command. Each node in the tree is prefaces with '+--'. Schema nodes command. Each node in the tree is prefaces with "+--". Schema nodes
that are children of another node are offset from the parent by 3 that are children of another node are offset from the parent by 3
spaces. Schema peer nodes separated are listed with the same space spaces. Schema peer nodes separated are listed with the same space
offset and, when separated by lines, linked via a pipe ('|') offset and, when separated by lines, linked via a vertical bar ("|")
character. character.
The full format, including spacing conventions is: The full format, including spacing conventions is:
module: <module-name> module: <module-name>
+--<node>
| +--<node>
| +--<node>
+--<node>
+--<node>
+--<node>
+--<node>
| +--<node>
| +--<node>
+--<node>
+--<node>
+--<node>
augment <target-node>: augment <target-node>:
+--<node> +--<node>
+--<node> +--<node>
+--<node> +--<node>
+--<node> +--<node>
augment <target-node>:
+--<node>
rpcs: rpcs:
+--<rpc-node>
+--<rpc-node>
+--<node>
| +--<node>
+--<node>
notifications:
+--<notification-node>
+--<notification-node>
+--<node>
| +--<node>
+--<node>
grouping <grouping-name>:
+--<node> +--<node>
+--<node>
| +--<node>
+--<node>
grouping <grouping-name>:
+--<node> +--<node>
notifications: yang-data <yang-data-name>:
+--<node> +--<node>
+--<node> +--<node>
| +--<node> | +--<node>
+--<node> +--<node>
yang-data <yang-data-name>:
+--<node>
2.1. Submodules 2.1. Submodules
Submodules are represented in the same fashion as modules, but are Submodules are represented in the same fashion as modules, but are
identified by "submodule:" followed the (sub)module-name. For identified by "submodule:" followed the (sub)module-name. For
example: example:
submodule: <module-name> submodule: <module-name>
+--<node> +--<node>
| +--<node> | +--<node>
| +--<node> | +--<node>
2.2. Groupings 2.2. Groupings
Nodes within a used grouping are expanded as if the nodes were Nodes within a used grouping are expanded as if the nodes were
defined at the location of the uses statement. defined at the location of the uses statement.
2.3. Collapsed Node Representation Groupings may optionally be present in the "groupings" section.
2.3. yang-data
If the module defines a "yang-data" structure [RFC8040], these
structures may optionally be present in the "yang-data" section.
2.4. Collapsed Node Representation
At times when the composition of the nodes within a module schema are At times when the composition of the nodes within a module schema are
not important in the context of the presented tree, peer nodes and not important in the context of the presented tree, peer nodes and
their children can be collapsed using the notation '...' in place of their children can be collapsed using the notation "..." in place of
the text lines used to represent the summarized nodes. For example: the text lines used to represent the summarized nodes. For example:
+--<node> +--<node>
| ... | ...
+--<node> +--<node>
+--<node> +--<node>
+--<node> +--<node>
2.4. Node Representation 2.5. Comments
Single line comments, starting with "//" and ending at the end of the
line, may be used in the tree notation.
2.6. Node Representation
Each node in a YANG module is printed as: Each node in a YANG module is printed as:
<status> <flags> <name> <opts> <type> <if-features> <status> <flags> <name> <opts> <type> <if-features>
<status> is one of:
+ for current
x for deprecated
o for obsolete
<flags> is one of: <status> is one of:
rw for configuration data
ro for non-configuration data
-x for rpcs and actions
-n for notifications
mp for schema mount points
<name> is the name of the node + for current
(<name>) means that the node is a choice node
:(<name>) means that the node is a case node
If the node is augmented into the tree from another module, its x for deprecated
o for obsolete
name is printed as <prefix>:<name>. <flags> is one of:
rw for configuration data
ro for non-configuration data
-x for rpcs and actions
-n for notifications
mp for nodes containing a "mount-point" extension statment
<opts> is one of: <name> is the name of the node
? for an optional leaf, choice, anydata or anyxml (<name>) means that the node is a choice node
! for a presence container :(<name>) means that the node is a case node
* for a leaf-list or list
[<keys>] for a list's keys
/ for a mounted module
@ for a node made available via a schema mount
parent reference
<type> is the name of the type for leafs and leaf-lists If the node is augmented into the tree from another module,
its name is printed as <prefix>:<name>.
If the type is a leafref, the type is printed as "-> TARGET", <opts> is one of:
where TARGET is either the leafref path, with prefixed removed ? for an optional leaf, choice, anydata or anyxml
if possible. ! for a presence container
* for a leaf-list or list
[<keys>] for a list's keys
/ for a top-level data node in a mounted module
@ for a top-level data node in a parent referenced module
<if-features> is the list of features this node depends on, <type> is the name of the type for leafs and leaf-lists
printed within curly brackets and a question mark "{...}?"
2.5. Extensions If the type is a leafref, the type is printed as "-> TARGET",
where TARGET is either the leafref path, with prefixed removed
if possible.
TBD <if-features> is the list of features this node depends on,
printed within curly brackets and a question mark "{...}?"
3. Usage Guidelines For RFCs 3. Usage Guidelines For RFCs
This section provides general guidelines related to the use of tree This section provides general guidelines related to the use of tree
diagrams in RFCs. This section covers [Authors' note: will cover] diagrams in RFCs.
different types of trees and when to use them; for example, complete
module trees, subtrees, trees for groupings etc.
3.1. Wrapping Long Lines 3.1. Wrapping Long Lines
Internet Drafts and RFCs limit the number of characters that may in a Internet Drafts and RFCs limit the number of characters that may in a
line of text to 72 characters. When the tree representation of a line of text to 72 characters. When the tree representation of a
node results in line being longer than this limit the line should be node results in line being longer than this limit the line should be
broken between <opts> and <type>. The type should be indented so broken between <opts> and <type>. The type should be indented so
that the new line starts below <name> with a white space offset of at that the new line starts below <name> with a white space offset of at
least two characters. For example: least two characters. For example:
notifications: notifications:
+---n yang-library-change +---n yang-library-change
+--ro module-set-id +--ro module-set-id
-> /modules-state/module-set-id -> /modules-state/module-set-id
The previously 'pyang' command can be helpful in producing such The previously mentioned "pyang" command can be helpful in producing
output, for example the above example was produced using: such output, for example the above example was produced using:
pyang -f tree --tree-line-length 50 < ietf-yang-library.yang pyang -f tree --tree-line-length 50 ietf-yang-library.yang
When a tree diagram is included as a figure in an Internet Draft or
RFC, "--tree-line-length 69" works well.
3.2. Long Diagrams
As tree diagrams are intended to provide a simplified view of a
module, diagrams longer than a page should generally be avoided. If
the complete tree diagram for a module becomes too long, the diagram
can be split into several smaller diagrams. For example, it might be
possible to have one diagram with the data node and another with all
notifications. If the data nodes tree is too long, it is also
possible to split the diagram into smaller diagrams for different
subtrees. When long diagrams are included in a document, authors
should consider whether to include the long diagram in the main body
of the document or in an appendix.
An example of such a split can be found in [RFC7407], where section
2.4 shows the diagram for "engine configuration":
+--rw snmp
+--rw engine
// more parameters from the "engine" subtree here
Further, section 2.5 shows the diagram for "target configuration":
+--rw snmp
+--rw target* [name]
// more parameters from the "target" subtree here
The previously mentioned "pyang" command can be helpful in producing
such output, for example the above example was produced using:
pyang -f tree --tree-path /snmp/target ietf-snmp.yang
4. YANG Schema Mount Tree Diagrams 4. YANG Schema Mount Tree Diagrams
YANG Schema Mount is defined in [I-D.ietf-netmod-schema-mount] and YANG Schema Mount is defined in [I-D.ietf-netmod-schema-mount] and
warrants some specific discussion. Schema mount document is a warrants some specific discussion. Schema mount is a generic
generic mechanism that allows for mounting one data model consisting mechanism that allows for mounting of one or more data modules at a
of any number of YANG modules at a specified location of another specified location of another (parent) schema. The specific location
(parent) schema. Modules containing mount points will identify mount is referred to as a mount point, and any container or list node in a
points by name using the mount-point extension. These mount-points schema may serve as a mount point. Mount points are identified via
should be identified, as indicated above using the 'mp' flag. For the inclusion of the "mount-point" extension statement as a
example: substament under a container or list node. Mount point nodes are
thus directly identified in a module schema definition and can be
identified in a tree diagram as indicated above using the "mp" flag.
In the following example taken from [I-D.ietf-rtgwg-ni-model],
"vrf-root" is a container that includes the "mount-point" extension
statement as part of its definition:
module: ietf-network-instance module: ietf-network-instance
+--rw network-instances +--rw network-instances
+--rw network-instance* [name] +--rw network-instance* [name]
+--rw name string +--rw name string
+--rw enabled? boolean +--rw enabled? boolean
+--rw description? string +--rw description? string
+--rw (ni-type)? +--rw (ni-type)?
+--rw (root-type)? +--rw (root-type)
+--:(vrf-root) +--:(vrf-root)
| +--mp vrf-root? | +--mp vrf-root
Note that a mount point definition alone is not sufficient to 4.1. Representation of Instance Data Trees
identify if a mount point configuration or for non-configuration
data. This is determined by the yang-schema-mount module 'config'
leaf associated with the specific mount point.
In describing the intended use of a module containing a mount point, The actual modules made available under a mount point is controlled
it is helpful to show how the mount point would look with mounted by a server and is provided to clients. This information is
modules. In such cases, the mount point should be treated much like typically provided via the Schema Mount module defined in
a container that uses a grouping. The flags should also be set based [I-D.ietf-netmod-schema-mount]. The Schema Mount module supports
on the 'config' leaf mentioned above, and the mount realted options exposure of both mounted schema and "parent-references". Parent
indicated above should be shown. For example, the following references are used for XPath evaluation within mounted modules and
represents the prior example with YANG Routing and OSPF modules do not represent client-accessible paths; the referenced information
mounted, YANG Interface module nodes accessible via a parent- is available to clients via the parent schema. Schema mount also
reference, and 'config' indicating true: defines an "inline" type mount point where mounted modules are
exposed via the YANG library module.
module: ietf-network-instance While the modules made available under a mount point are not
+--rw network-instances specified in YANG modules that include mount points, the document
+--rw network-instance* [name] defining the module will describe the intended use of the module and
+--rw name string may identify both modules that will be mounted and parent modules
+--rw enabled? boolean that can be referenced by mounted modules. An example of such a
+--rw description? string description can be found in [I-D.ietf-rtgwg-ni-model]. A specific
+--rw (ni-type)? implementation of a module containing mount points will also support
+--rw (root-type)? a specific list of mounted and referenced modules. In describing
+--:(vrf-root) both intended use and actual implementations, it is helpful to show
+--mp vrf-root? how mounted modules would be instantiated and referenced under a
+--ro rt:routing-state/ mount point using tree diagrams.
| ...
+--rw rt:routing/
| ...
+--ro if:interfaces@
| ...
+--ro if:interfaces-state@
...
The with 'config' indicating false, the only change would be to the In such diagrams, the mount point should be treated much like a
flag on the rt:routing node: container that uses a grouping. The flags should also be set based
on the "config" leaf mentioned above, and the mount realted options
indicated above should be shown for the top level nodes in a mounted
or referenced module. The following example, taken from
[I-D.ietf-rtgwg-ni-model], represents the prior example with YANG
Routing and OSPF modules mounted, YANG Interface module nodes
accessible via a parent-reference, and "config" indicating true:
module: ietf-network-instance
+--rw network-instances
+--rw network-instance* [name]
+--rw name string
+--rw enabled? boolean
+--rw description? string
+--rw (ni-type)?
+--rw (root-type)
+--:(vrf-root)
+--mp vrf-root
+--ro rt:routing-state/
| +--ro router-id?
| +--ro control-plane-protocols
| +--ro control-plane-protocol* [type name]
| +--ro ospf:ospf
| +--ro instance* [af]
| ...
+--rw rt:routing/
| +--rw router-id?
| +--rw control-plane-protocols
| +--rw control-plane-protocol* [type name]
| +--rw ospf:ospf
| +--rw instance* [af]
| ...
+--ro if:interfaces@
| ...
+--ro if:interfaces-state@
| ...
It is worth highlighting that the OSPF module augments the Routing
module, and while it is listed in the Schema Mount module (or inline
YANG library) there is no special mount-related notation in the tree
diagram.
A mount point definition alone is not sufficient to identify if the
mounted modules are used for configuration or for non-configuration
data. This is determined by the "ietf-yang-schema-mount" module's
"config" leaf associated with the specific mount point and is
indicated on the top level mounted nodes. For example in the above
tree, when the "config" for the routing module indicates false, the
only change would be to the flag on the rt:routing node:
+--ro rt:routing/ +--ro rt:routing/
5. IANA Considerations 5. IANA Considerations
There are no IANA requests or assignments included in this document. There are no IANA requests or assignments included in this document.
6. Informative References 6. Security Considerations
There is no security impact related to the tree diagrams defined in
this document.
7. Informative References
[I-D.ietf-netmod-schema-mount] [I-D.ietf-netmod-schema-mount]
Bjorklund, M. and L. Lhotka, "YANG Schema Mount", draft- Bjorklund, M. and L. Lhotka, "YANG Schema Mount", draft-
ietf-netmod-schema-mount-05 (work in progress), May 2017. ietf-netmod-schema-mount-08 (work in progress), October
2017.
[I-D.ietf-rtgwg-ni-model]
Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and X.
Liu, "YANG Network Instances", draft-ietf-rtgwg-ni-
model-04 (work in progress), September 2017.
[RFC7223] Bjorklund, M., "A YANG Data Model for Interface [RFC7223] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 7223, DOI 10.17487/RFC7223, May 2014, Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
<http://www.rfc-editor.org/info/rfc7223>. <https://www.rfc-editor.org/info/rfc7223>.
[RFC7407] Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for
SNMP Configuration", RFC 7407, DOI 10.17487/RFC7407,
December 2014, <https://www.rfc-editor.org/info/rfc7407>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016, RFC 7950, DOI 10.17487/RFC7950, August 2016,
<http://www.rfc-editor.org/info/rfc7950>. <https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
Authors' Addresses Authors' Addresses
Martin Bjorklund Martin Bjorklund
Tail-f Systems Tail-f Systems
Email: mbj@tail-f.com Email: mbj@tail-f.com
Lou Berger (editor) Lou Berger (editor)
LabN Consulting, L.L.C. LabN Consulting, L.L.C.
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