draft-ietf-netmod-yang-model-classification-02.txt		draft-ietf-netmod-yang-model-classification-03.txt
	NETMOD D. Bogdanovic		NETMOD D. Bogdanovic
	Internet-Draft Volta Networks, Inc.		Internet-Draft Volta Networks, Inc.
	Intended status: Informational B. Claise		Intended status: Informational B. Claise
	Expires: December 24, 2016 C. Moberg		Expires: April 2, 2017 C. Moberg
	Cisco Systems, Inc.		Cisco Systems, Inc.
	June 22, 2016		September 29, 2016
	YANG Module Classification		YANG Module Classification
	draft-ietf-netmod-yang-model-classification-02		draft-ietf-netmod-yang-model-classification-03
	Abstract		Abstract
	The YANG [RFC6020] data modeling language is currently being		The YANG [RFC6020] data modeling language is currently being
	considered for a wide variety of applications throughout the		considered for a wide variety of applications throughout the
	networking industry at large. Many standards-defining organizations		networking industry at large. Many standards-defining organizations
	(SDOs), open source software projects, vendors and users are using		(SDOs), open source software projects, vendors and users are using
	YANG to develop and publish YANG modules of configuration, state data		YANG to develop and publish YANG modules for a wide variety of
	and operations for a wide variety of applications. At the same time,		applications. At the same time, there is currently no well-known
	there is currently no well-known terminology to categorize various		terminology to categorize various types of YANG modules.
	types of YANG modules.
	A consistent terminology would help with the categorization of YANG		A consistent terminology would help with the categorization of YANG
	modules, assist in the analysis the YANG data modeling efforts in the		modules, assist in the analysis of the YANG data modeling efforts in
	IETF and other organizations, and bring clarity to the YANG-related		the IETF and other organizations, and bring clarity to the YANG-
	discussions between the different groups.		related discussions between the different groups.
	This document describes a set of concepts and associated terms to		This document describes a set of concepts and associated terms to
	support consistent classification of YANG modules.		support consistent classification of YANG modules.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	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 24, 2016.		This Internet-Draft will expire on April 2, 2017.
	Copyright Notice		Copyright Notice
	Copyright (c) 2016 IETF Trust and the persons identified as the		Copyright (c) 2016 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4		1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
	2. First Dimension: YANG Data Model Abstraction Layers . . . . . 4		2. First Dimension: YANG Module Abstraction Layers . . . . . . . 4
	2.1. Network Service YANG Modules . . . . . . . . . . . . . . 6		2.1. Network Service YANG Modules . . . . . . . . . . . . . . 6
	2.2. Network Element YANG Modules . . . . . . . . . . . . . . 7		2.2. Network Element YANG Modules . . . . . . . . . . . . . . 7
	3. Second Dimension: Module Types . . . . . . . . . . . . . . . 7		3. Second Dimension: Module Types . . . . . . . . . . . . . . . 7
	3.1. Standard YANG Modules . . . . . . . . . . . . . . . . . . 8		3.1. Standard YANG Modules . . . . . . . . . . . . . . . . . . 8
	3.2. Vendor-specific YANG Modules and Extensions . . . . . . . 8		3.2. Vendor-specific YANG Modules and Extensions . . . . . . . 8
	3.3. User-specific YANG Modules and Extensions . . . . . . . . 9		3.3. User-specific YANG Modules and Extensions . . . . . . . . 9
	4. Adding The Classification Type to YANG Module Catalogs . . . 9		4. Adding The Classification Type to YANG Module Catalogs . . . 9
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 10		5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10		7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
	8. Change log [RFC Editor: Please remove] . . . . . . . . . . . 10		8. Change log [RFC Editor: Please remove] . . . . . . . . . . . 10
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
	9.1. Normative References . . . . . . . . . . . . . . . . . . 11		9.1. Normative References . . . . . . . . . . . . . . . . . . 11
	9.2. Informative References . . . . . . . . . . . . . . . . . 11		9.2. Informative References . . . . . . . . . . . . . . . . . 11
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
	1. Introduction		1. Introduction
	The Internet Engineering Steering Group (IESG) has been actively		The Internet Engineering Steering Group (IESG) has been actively
	encouraging IETF working groups to use the YANG [RFC6020]		encouraging IETF working groups to use the YANG modeling language
	[I-D.ietf-netmod-rfc6020bis] and NETCONF [RFC6241] and YANG standards		[RFC6020], [RFC7950] and NETCONF protocol [RFC6241] for configuration
	for configuration management purposes, especially in new working		management purposes, especially in new working group charters
	group charters [Writable-MIB-Module-IESG-Statement].		[Writable-MIB-Module-IESG-Statement].
	YANG is also gaining wide acceptance as the de-facto standard		YANG is also gaining wide acceptance as the de-facto standard
	modeling language in the broader industry. This extends beyond the		modeling language in the broader industry. This extends beyond the
	IETF, including many standards development organizations, industry		IETF, including many standards development organizations, industry
	consortia, ad hoc groups, open source projects, vendors, and end-		consortia, ad hoc groups, open source projects, vendors, and end-
	users.		users.
	There are currently no clear guidelines on how to classify the		There are currently no clear guidelines on how to classify the
	layering of YANG modules according to abstraction, or how to classify		layering of YANG modules according to abstraction, or how to classify
	modules along the continuum spanning formal standards publications,		modules along the continuum spanning formal standards publications,
	skipping to change at page 3, line 24 ¶		skipping to change at page 3, line 24 ¶
	dimensions:		dimensions:
	o The layering of modules based on their abstraction levels		o The layering of modules based on their abstraction levels
	o The type of module based on the nature and intent of the content		o The type of module based on the nature and intent of the content
	The intent of this document is to provide a taxonomy to simplify		The intent of this document is to provide a taxonomy to simplify
	human communication around YANG modules. The authors acknowledge		human communication around YANG modules. The authors acknowledge
	that the classification boundaries are at times blurry, but believe		that the classification boundaries are at times blurry, but believe
	that this document should provide a robust starting point as the YANG		that this document should provide a robust starting point as the YANG
	community gain further experience with designing and deploying		community gains further experience with designing and deploying
	modules. To be more explicit, the authors believe that the		modules. To be more explicit, the authors believe that the
	classification criteria will change over time.		classification criteria will change over time.
	An example of a type of module that have created substantial		A number of module types have created substantial discussion during
	discussion during the development of this document is topologies.		the development of this document including those concerned with
	Topology models are useful both on the Network Element level (e.g.		topologies. Topology modules are useful both on the Network Element
	link-state database content) as well as in the Network Service level		level (e.g. link-state database content) as well as on the Network
	(e.g. network-wide, configured topologies). In the end, it is the		Service level (e.g. network-wide, configured topologies). In the
	module developer that classifies the module according to the initial		end, it is the module developer that classifies the module according
	intent of the module content.		to the initial intent of the module content.
	This document should provide benefits to multiple audiences:		This document should provide benefits to multiple audiences:
	o First, a common taxonomy helps with the different standards		o First, a common taxonomy helps with the different standards
	development organizations and industry consortia discussions,		development organizations and industry consortia discussions,
	whose goals are determined in their respective areas of work.		whose goals are determined in their respective areas of work.
	o Second, operators might look at the YANG module classification		o Second, operators might look at the YANG module classification
	type to understand which Network Service YANG modules and Network		type to understand which Network Service YANG modules and Network
	Element YANG modules are available for their service composition.		Element YANG modules are available for their service composition.
	skipping to change at page 4, line 12 ¶		skipping to change at page 4, line 12 ¶
	Element YANG module that contains the L2VPN data definitions		Element YANG module that contains the L2VPN data definitions
	required to be configured on a single device.		required to be configured on a single device.
	o And thirdly, this taxonomy would help equipment vendors (whether		o And thirdly, this taxonomy would help equipment vendors (whether
	physical or virtual), controller vendors, orchestrator vendors to		physical or virtual), controller vendors, orchestrator vendors to
	explain to their customers the relationship between the different		explain to their customers the relationship between the different
	YANG modules they propose in their products. See Figure 1.		YANG modules they propose in their products. See Figure 1.
	1.1. Terminology		1.1. Terminology
	RFC6020bis [I-D.ietf-netmod-rfc6020bis] specifies:		[RFC7950] specifies:
	o data model: A data model describes how data is represented and		o data model: A data model describes how data is represented and
	accessed.		accessed.
	o module: A YANG module defines a hierarchy of nodes that can be		o module: A YANG module defines a hierarchy of nodes that can be
	used for NETCONF-based operations. With its definitions and the		used for NETCONF-based operations. With its definitions and the
	definitions it imports or includes from elsewhere, a module is		definitions it imports or includes from elsewhere, a module is
	self-contained and "compilable".		self-contained and "compilable".
	2. First Dimension: YANG Data Model Abstraction Layers		2. First Dimension: YANG Module Abstraction Layers
	Model developers have taken two approaches to developing YANG		Module developers have taken two approaches to developing YANG
	modules: top-down and bottom-up. The top-down approach starts with		modules: top-down and bottom-up. The top-down approach starts with
	high level abstractions modeling business or customer requirements		high level abstractions modeling business or customer requirements
	and maps them to specific networking technologies. The bottom-up		and maps them to specific networking technologies. The bottom-up
	approach starts with fundamental networking technologies and maps		approach starts with fundamental networking technologies and maps
	them into more abstract constructs.		them into more abstract constructs.
	There are currently no specific requirements on, or well-defined best		There are currently no specific requirements on, or well-defined best
	practices around the development of YANG modules For the purpose of		practices around the development of YANG modules. For the purpose of
	this document we assume that both approaches (bottom-up and top-down)		this document we assume that both approaches (bottom-up and top-down)
	will be used as they both provide benefits that appeal to different		will be used as they both provide benefits that appeal to different
	groups.		groups.
	For layering purposes, this document suggests the classification of		For layering purposes, this document suggests the classification of
	YANG modules into two distinct abstraction layers:		YANG modules into two distinct abstraction layers:
	o Network Element YANG Modules describe the configuration, state		o Network Element YANG Modules describe the configuration, state
	data and operations of specific device-centric technologies or		data, operations and notifications of specific device-centric
	features		technologies or features
	o Network Service YANG Modules describe the configuration, state		o Network Service YANG Modules describe the configuration, state
	data and operations of an abstract representation of a service		data, operations and notifications of abstract representations of
	implemented on one or multiple network elements		services implemented on one or multiple network elements
			+--------------------------+
			| Operations and Business |
			| Support Systems |
			| (OSS/BSS) |
			+--------------------------+
			- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
			Network Service YANG Modules
			+------------+ +-------------+ +-------------+
			| | | | | |
			| - L2VPN | | - L2VPN | | L3VPN |
			| - VPWS | | - VPLS | | |
			| | | | | |
			+------------+ +-------------+ +-------------+
			- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
			Network Element YANG Modules
			+------------+ +------------+ +-------------+ +------------+
			| | | | | | | |
			| MPLS | | BGP | | IPv4 / IPv6 | | Ethernet |
			| | | | | | | |
			+------------+ +------------+ +-------------+ +------------+
			L2VPN: Layer 2 Virtual Private Network
			L3VPN: Layer 3 Virtual Private Network
			VPWS: Virtual Private Wire Service
			VPLS: Virtual Private LAN Service
			Figure 1: YANG Module Layers
	Figure 1 illustrates the application of YANG modules at different		Figure 1 illustrates the application of YANG modules at different
	layers of abstraction. Layering of modules allows for reusability of		layers of abstraction. Layering of modules allows for reusability of
	existing lower layer modules by higher level modules while limiting		existing lower layer modules by higher level modules while limiting
	duplication of features across layers.		duplication of features across layers.
	For module developers, per-layer modeling allows for separation of		For module developers, per-layer modeling allows for separation of
	concern across editing teams focusing on specific areas.		concern across editing teams focusing on specific areas.
	As an example, experience from the IETF shows that creating useful		As an example, experience from the IETF shows that creating useful
	network element YANG modules for e.g. routing or switching protocols		network element YANG modules for e.g. routing or switching protocols
	requires teams that include developers with experience of		requires teams that include developers with experience of
	implementing those protocols.		implementing those protocols.
	On the other hand, network service YANG modules are best developed by		On the other hand, network service YANG modules are best developed by
	network operators experienced in defining network services for		network operators experienced in defining network services for
	consumption by programmers developing e.g. flow-through provisioning		consumption by programmers developing e.g. flow-through provisioning
	systems or self-service portals.		systems or self-service portals.
	+--------------------------+
	| Operations and Business |
	| Support Systems |
	| (OSS/BSS) |
	+--------------------------+
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
	Network Service YANG Modules
	+------------+ +-------------+ +-------------+
	| | | | | |
	| - L2VPN | | - L2VPN | | L3VPN |
	| - VPWS | | - VPLS | | |
	| | | | | |
	+------------+ +-------------+ +-------------+
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
	Network Element YANG Modules
	+------------+ +------------+ +-------------+ +------------+
	| | | | | | | |
	| MPLS | | BGP | | IPv4 / IPv6 | | Ethernet |
	| | | | | | | |
	+------------+ +------------+ +-------------+ +------------+
	L2VPN: Layer 2 Virtual Private Network
	L3VPN: Layer 3 Virtual Private Network
	VPWS: Virtual Private Wire Service
	VPLS: Virtual Private LAN Service
	Figure 1: YANG Module Layers
	2.1. Network Service YANG Modules		2.1. Network Service YANG Modules
	Network Service YANG Modules describe the characteristics of a		Network Service YANG Modules describe the characteristics of a
	service, as agreed upon with consumers of that service. That is, a		service, as agreed upon with consumers of that service. That is, a
	service model does not expose the detailed configuration parameters		service module does not expose the detailed configuration parameters
	of all participating network elements and features, but describes an		of all participating network elements and features, but describes an
	abstract model that allows instances of the service to be decomposed		abstract model that allows instances of the service to be decomposed
	into instance data according to the Network Element Modules of the		into instance data according to the Network Element YANG Modules of
	participating network elements. The service-to-element decomposition		the participating network elements. The service-to-element
	is a separate process with details depending on how the network		decomposition is a separate process with details depending on how the
	operator chooses to realize the service. For the purpose of this		network operator chooses to realize the service. For the purpose of
	document we will use the term "orchestrator" to describe a system		this document we will use the term "orchestrator" to describe a
	implementing such a process.		system implementing such a process.
	As an example, the Network Service YANG Module included in		As an example, the Network Service YANG Module defined in
	[YANG-Data-Model-for-L3VPN-service-delivery] provides an abstract		[YANG-Data-Model-for-L3VPN-service-delivery] provides an abstract
	model for Layer 3 IP VPN service configuration. This model includes		model for Layer 3 IP VPN service configuration. This module includes
	e.g. the concept of a 'site-network-access' to represent bearer and		e.g. the concept of a 'site-network-access' to represent bearer and
	connection parameters. An orchestrator receives operations on		connection parameters. An orchestrator receives operations on
	service instances according to the service model and decomposes the		service instances according to the service module and decomposes the
	data into specific Network Element Modules to configure the		data into specific Network Element YANG Modules to configure the
	participating network elements to perform the intent of the service.		participating network elements to perform the intent of the service.
	In the case of the L3VPN module, this would include translating the		In the case of the L3VPN module, this would include translating the
	'site-network-access' parameters to the appropriate parameters in the		'site-network-access' parameters to the appropriate parameters in the
	Network Element YANG Module implemented on the constituent elements.		Network Element YANG Module implemented on the constituent elements.
	Network Service YANG Modules define services models to be consumed by		Network Service YANG Modules define service models to be consumed by
	external systems. These modules are commonly designed, developed and		external systems. These modules are commonly designed, developed and
	deployed by network infrastructure teams.		deployed by network infrastructure teams.
	YANG allows for different design patterns to describe network		YANG allows for different design patterns to describe network
	services, ranging from monolithic to component-based approaches.		services, ranging from monolithic to component-based approaches.
	The monolithic approach captures the entire service in a single		The monolithic approach captures the entire service in a single
	module and does not put focus on reusability of internal data		module and does not put focus on reusability of internal data
	definitions and groupings. The monolithic approach has the		definitions and groupings. The monolithic approach has the
	advantages of single-purpose development including speed at the		advantages of single-purpose development including speed at the
	skipping to change at page 7, line 15 ¶		skipping to change at page 7, line 17 ¶
	As an example, an L2VPN service can be built on many different types		As an example, an L2VPN service can be built on many different types
	of transport network technologies, including e.g. MPLS or carrier		of transport network technologies, including e.g. MPLS or carrier
	ethernet. A component-based approach would allow for reuse of e.g.		ethernet. A component-based approach would allow for reuse of e.g.
	UNI-interface definitions independent of the underlying transport		UNI-interface definitions independent of the underlying transport
	network (e.g. MEF UNI interface or MPLS interface). The monolithic		network (e.g. MEF UNI interface or MPLS interface). The monolithic
	approach would assume a specific set of transport technologies and		approach would assume a specific set of transport technologies and
	interface definitions.		interface definitions.
	2.2. Network Element YANG Modules		2.2. Network Element YANG Modules
	Network Element YANG Modules describe the configuration, state data		Network Element YANG Modules describe the characteristics of a
	and operations of a network device as defined by the vendor of that		network device as defined by the vendor of that device. The modules
	device. The modules are commonly structured around features of the		are commonly structured around features of the device, e.g. interface
	device, e.g. interface configuration [RFC7223], OSPF configuration		configuration [RFC7223], OSPF configuration [I-D.ietf-ospf-yang], and
	[I-D.ietf-ospf-yang], and firewall rules definitions		firewall rules definitions [I-D.ietf-netmod-acl-model].
	[I-D.ietf-netmod-acl-model].
	The module provides a coherent data model representation of what is		The module provides a coherent data model representation of the
	commonly a very mixed software environment consisting of the		software environment consisting of the operating system and
	operating system and applications running on the device. The		applications running on the device. The decomposition, ordering, and
	decomposition, ordering, and execution of changes to the operating		execution of changes to the operating system and application
	system and application configuration is the task of the management		configuration is the task of the agent that implements the module.
	framework that implements the YANG module.
	3. Second Dimension: Module Types		3. Second Dimension: Module Types
	This document suggests classifying YANG module types as either		This document suggests classifying YANG module types as standard YANG
	standard YANG modules, vendor-specific YANG modules and extensions,		modules, vendor-specific YANG modules and extensions, or user-
	and user-specific YANG modules and extensions		specific YANG modules and extensions
	The suggested classification applies to both Network Element YANG		The suggested classification applies to both Network Element YANG
	Modules and Network Service YANG Modules.		Modules and Network Service YANG Modules.
	It is to be expected that real-world implementations of both Network		It is to be expected that real-world implementations of both Network
	Service and Network Element YANG Modules will include a mix of all		Service YANG Modules and Network Element YANG Modules will include a
	three types of modules.		mix of all three types of modules.
	Figure 2 illustrates the relationship between the three types of		Figure 2 illustrates the relationship between the three types of
	modules.		modules.
	+--------------+		+--------------+
	| User |		| User |
	| Extensions |		| Extensions |
	+------+-------+		+------+-------+
	Augments		Augments
	+------+-------+ +--------------+ +--------------+		+------+-------+ +--------------+ +--------------+
	| Vendor | | User | | User |		| Vendor | | User | | User |
	| Extensions | | Extensions | | Extensions |		| Extensions | | Extensions | | Extensions |
	+------+-------+ +------+-------+ +------+-------+		+------+-------+ +------+-------+ +------+-------+
	Augments Augments Augments		Augments Augments Augments
	+------+-----------------+-------+ +------+-------+ +--------------+		+------+-----------------+-------+ +------+-------+ +--------------+
	| Standard | | Vendor | | User |		| Standard | | Vendor | | User |
	| Models | | Models | | Models |		| Modules | | Modules | | Modules |
	+--------------------------------+ +--------------+ +--------------+		+--------------------------------+ +--------------+ +--------------+
	Figure 2: YANG Module Types		Figure 2: YANG Module Types
	3.1. Standard YANG Modules		3.1. Standard YANG Modules
	Standard YANG Modules are published by standards-defining		Standard YANG Modules are published by standards-defining
	organizations (SDOs). While there is no formal definition of what		organizations (SDOs). While there is no formal definition of what
	construes an SDO, a common feature is that they publish		construes an SDO, a common feature is that they publish
	specifications along specific processes with content that reflects		specifications along specific processes with content that reflects
	some sort of membership consensus. The specifications are developed		some sort of membership consensus. The specifications are developed
	for wide use among the membership or for audiences beyond that.		for wide use among the membership or for audiences beyond that.
	The lifecycle of these modules is driven by the editing cycle of the		The lifecycle of these modules is driven by the editing cycle of the
	specification and not tied to a specific implementation.		specification and not tied to a specific implementation.
	Examples of SDOs in the networking industry are the IETF, the IEEE		Examples of SDOs in the networking industry are the IETF, the IEEE
	(Institute of Electrical and Electronics Engineers) and the MEF.		and the MEF.
	3.2. Vendor-specific YANG Modules and Extensions		3.2. Vendor-specific YANG Modules and Extensions
	Vendor-specific YANG modules are developed by organizations with the		Vendor-specific YANG Modules are developed by organizations with the
	intent to support a specific set of implementations under control of		intent to support a specific set of implementations under control of
	that organization. For example vendors of virtual or physical		that organization. For example vendors of virtual or physical
	equipment, industry consortia, and opensource projects. The intent		equipment, industry consortia, and opensource projects. The intent
	of these modules range from providing openly published YANG modules		of these modules range from providing openly published YANG modules
	that may eventually be contributed back to, or adopted by an SDO, to		that may eventually be contributed back to, or adopted by, an SDO, to
	strictly internal YANG modules not intended for external consumption.		strictly internal YANG modules not intended for external consumption.
	The lifecycle of these modules are generally aligned with the release		The lifecycle of these modules are generally aligned with the release
	cycle of the product or open source software project deliverables.		cycle of the product or open source software project deliverables.
	It is worth noting that there is an increasing amount of interaction		It is worth noting that there is an increasing amount of interaction
	between open source projects and SDOs in the networking industry.		between open source projects and SDOs in the networking industry.
	This includes open source projects implementing published standards		This includes open source projects implementing published standards
	as well as open source projects contributing content to SDO		as well as open source projects contributing content to SDO
	processes.		processes.
	Vendors also develop Vendor-specific Extensions to standard modules		Vendors also develop Vendor-specific Extensions to standard modules
	using YANG constructs for extending data definitions of previously		using YANG constructs for extending data definitions of previously
	published modules. This is done using the 'augment' statement that		published modules. This is done using the 'augment' statement that
	allows locally defined data trees to be augmented into locations in		allows locally defined data trees to be augmented into locations in
	externally defined data trees.		externally defined data trees.
	Vendors use this to extend standard modules to cover the full scope		Vendors use this to extend standard modules to cover the full scope
	of features in implementations, which commonly is broader than what		of features in implementations, which commonly is broader than that
	is covered by the standard module.		covered by the standard module.
	3.3. User-specific YANG Modules and Extensions		3.3. User-specific YANG Modules and Extensions
	User-specific YANG modules are developed by organizations that		User-specific YANG Modules are developed by organizations that
	operate YANG-based infrastructure including devices and		operate YANG-based infrastructure including devices and
	orchestrators. For example, network administrators in enterprises,		orchestrators. For example, network administrators in enterprises,
	or operators service providers. The intent of these modules is to		or at service providers. The intent of these modules is to express
	express the specific needs for a certain implementation, above and		the specific needs for a certain implementation, above and beyond
	beyond what is provided by vendors.		what is provided by vendors.
	This module type obviously requires the infrastructure to support the		This module type obviously requires the infrastructure to support the
	introduction of user-provided modules and extensions. This would		introduction of user-provided modules and extensions. This would
	include ability to describe the service-to-network decomposition in		include ability to describe the service-to-network decomposition in
	orchestrators and the module to configuration decomposition in		orchestrators and the module to configuration decomposition in
	devices.		devices.
	The lifecycle of these modules are generally aligned with the change		The lifecycles of these modules are generally aligned with the change
	cadence of the infrastructure.		cadence of the infrastructure.
	4. Adding The Classification Type to YANG Module Catalogs		4. Adding The Classification Type to YANG Module Catalogs
	The suggested classification in this document would be an useful		The suggested classification in this document would be an useful
	information in a catalog of YANG modules. Such catalog allows for		information in a catalog of YANG modules. Such a catalog allows for
	easy lookup and reusability of YANG modules. Practically, the YANG		easy lookup and reusability of YANG modules. Practically, the YANG
	module classification type would be an additional leaf to YANG module		module classification type would be an additional leaf to a YANG
	specified in [I-D.openconfig-netmod-model-catalog]:		module specified in [I-D.openconfig-netmod-model-catalog]:
	leaf module-class{		leaf module-class{
	type enum {		type enum {
	service		service
	device		device
	notApplicable		notApplicable
	}		}
	description		description
	"Categorization of the YANG module based on		"Categorization of the YANG module based on
	draft-ietf-netmod-yang-model-classification.";		draft-ietf-netmod-yang-model-classification.";
	}		}
	Note: this leaf should actually be moved to		Note: this leaf should actually be moved to
	[I-D.openconfig-netmod-model-catalog]. Note2: since a YANG module		[I-D.openconfig-netmod-model-catalog]. Note2: since a YANG module
	can belong to both service and device, the ENUM is not appropriate.		can belong to both service and device, the ENUM is not appropriate.
	A extensible list of module type is more appropriate.		An extensible list of module type is more appropriate.
	Indeed, without inspecting the YANG module itself, it's difficult to		Indeed, without inspecting the YANG module itself, it's difficult to
	determine whether its type is a network service or a network element.		determine whether its type is a network service or a network element.
	The YANG module name might provide some useful information but is not		The YANG module name might provide some useful information but is not
	a definite answer.		a definitive answer.
	5. Security Considerations		5. Security Considerations
	This document doesn't have any Security Considerations".		This document doesn't have any Security Considerations.
	6. IANA Considerations		6. IANA Considerations
	This document has no IANA actions.		This document has no IANA actions.
	7. Acknowledgements		7. Acknowledgements
	Thanks to David Ball and David Hansford for feedback and suggestions.		Thanks to David Ball and David Hansford for feedback and suggestions.
	8. Change log [RFC Editor: Please remove]		8. Change log [RFC Editor: Please remove]
	version 00: Renamed and small fixes based on WG feedback.		version 00: Renamed and small fixes based on WG feedback.
	version 01: Language fixes, collapsing of vendor data models and		version 01: Language fixes, collapsing of vendor data models and
	extensions, and the introduction of user data models and extensions.		extensions, and the introduction of user data models and extensions.
	version 02: Updated the YANG Module Catalog section, terminology		version 02: Updated the YANG Module Catalog section, terminology
	alignment (YANG data model versus YANG module), epxlain better the		alignment (YANG data model versus YANG module), explain better the
	distinction between the Network Element and Service YANG data models		distinction between the Network Element and Service YANG data models
	even if sometimes there are grey areas, editorial pass. Changed the		even if sometimes there are grey areas, editorial pass. Changed the
	use of the term 'model' to 'module' to be better aligned with		use of the term 'model' to 'module' to be better aligned with
	RFC6020.		RFC6020.
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for		[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
	the Network Configuration Protocol (NETCONF)", RFC 6020,		the Network Configuration Protocol (NETCONF)", RFC 6020,
	DOI 10.17487/RFC6020, October 2010,		DOI 10.17487/RFC6020, October 2010,
	<http://www.rfc-editor.org/info/rfc6020>.		<http://www.rfc-editor.org/info/rfc6020>.
			[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
			and A. Bierman, Ed., "Network Configuration Protocol
			(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
			<http://www.rfc-editor.org/info/rfc6241>.
			[RFC7223] Bjorklund, M., "A YANG Data Model for Interface
			Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
			<http://www.rfc-editor.org/info/rfc7223>.
			[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
			RFC 7950, DOI 10.17487/RFC7950, August 2016,
			<http://www.rfc-editor.org/info/rfc7950>.
	9.2. Informative References		9.2. Informative References
	[I-D.ietf-netmod-acl-model]		[I-D.ietf-netmod-acl-model]
	Bogdanovic, D., Koushik, K., Huang, L., and D. Blair,		Bogdanovic, D., Koushik, K., Huang, L., and D. Blair,
	"Network Access Control List (ACL) YANG Data Model",		"Network Access Control List (ACL) YANG Data Model",
	draft-ietf-netmod-acl-model-07 (work in progress), March		draft-ietf-netmod-acl-model-08 (work in progress), July
	2016.
	[I-D.ietf-netmod-rfc6020bis]
	Bjorklund, M., "The YANG 1.1 Data Modeling Language",
	draft-ietf-netmod-rfc6020bis-14 (work in progress), June
	2016.		2016.
	[I-D.ietf-ospf-yang]		[I-D.ietf-ospf-yang]
	Yeung, D., Qu, Y., Zhang, Z., Bogdanovic, D., and K.		Yeung, D., Qu, Y., Zhang, Z., Bogdanovic, D., and K.
	Koushik, "Yang Data Model for OSPF Protocol", draft-ietf-		Koushik, "Yang Data Model for OSPF Protocol", draft-ietf-
	ospf-yang-04 (work in progress), March 2016.		ospf-yang-05 (work in progress), July 2016.
	[I-D.openconfig-netmod-model-catalog]		[I-D.openconfig-netmod-model-catalog]
	D'Souza, K., Shaikh, A., and R. Shakir, "Catalog and		D'Souza, K., Shaikh, A., and R. Shakir, "Catalog and
	registry for YANG models", draft-openconfig-netmod-model-		registry for YANG models", draft-openconfig-netmod-model-
	catalog-00 (work in progress), October 2015.		catalog-01 (work in progress), July 2016.
	[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
	and A. Bierman, Ed., "Network Configuration Protocol
	(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
	<http://www.rfc-editor.org/info/rfc6241>.
	[RFC7223] Bjorklund, M., "A YANG Data Model for Interface
	Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
	<http://www.rfc-editor.org/info/rfc7223>.
	[Writable-MIB-Module-IESG-Statement]		[Writable-MIB-Module-IESG-Statement]
	"Writable MIB Module IESG Statement",		"Writable MIB Module IESG Statement",
	<https://www.ietf.org/iesg/statement/writable-mib-		<https://www.ietf.org/iesg/statement/writable-mib-
	module.html>.		module.html>.
	[YANG-Data-Model-for-L3VPN-service-delivery]		[YANG-Data-Model-for-L3VPN-service-delivery]
	"YANG Data Model for L3VPN service delivery",		"YANG Data Model for L3VPN service delivery",
	<https://tools.ietf.org/id/draft-l3vpn-service-yang>.		<https://tools.ietf.org/id/draft-l3vpn-service-yang>.
End of changes. 45 change blocks.
	129 lines changed or deleted		124 lines changed or added
This html diff was produced by rfcdiff 1.45. The latest version is available from http://tools.ietf.org/tools/rfcdiff/