draft-ietf-netmod-yang-model-classification-04.txt		draft-ietf-netmod-yang-model-classification-05.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: April 29, 2017 C. Moberg		Expires: September 14, 2017 C. Moberg
	Cisco Systems, Inc.		Cisco Systems, Inc.
	October 26, 2016		March 13, 2017
	YANG Module Classification		YANG Module Classification
	draft-ietf-netmod-yang-model-classification-04		draft-ietf-netmod-yang-model-classification-05
	Abstract		Abstract
	The YANG [RFC6020] data modeling language is currently being		The YANG data modeling language is currently being considered for a
	considered for a wide variety of applications throughout the		wide variety of applications throughout the networking industry at
	networking industry at large. Many standards-defining organizations		large. Many standards-defining organizations (SDOs), open source
	(SDOs), open source software projects, vendors and users are using		software projects, vendors and users are using YANG to develop and
	YANG to develop and publish YANG modules for a wide variety of		publish YANG modules for a wide variety of applications. At the same
	applications. At the same time, there is currently no well-known		time, there is currently no well-known terminology to categorize
	terminology to categorize various types of YANG modules.		various 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 of the YANG data modeling efforts in		modules, assist in the analysis of the YANG data modeling efforts in
	the IETF and other organizations, and bring clarity to the YANG-		the IETF and other organizations, and bring clarity to the YANG-
	related 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
	skipping to change at page 1, line 46 ¶		skipping to change at page 1, line 46 ¶
	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 April 29, 2017.		This Internet-Draft will expire on September 14, 2017.
	Copyright Notice		Copyright Notice
	Copyright (c) 2016 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.
	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
	skipping to change at page 2, line 34 ¶		skipping to change at page 2, line 34 ¶
	2. First Dimension: YANG Module 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. Security Considerations . . . . . . . . . . . . . . . . . . . 9		4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
	6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9		6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
	7. Change log [RFC Editor: Please remove] . . . . . . . . . . . 9		7. Change log [RFC Editor: Please remove] . . . . . . . . . . . 10
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
	8.1. Normative References . . . . . . . . . . . . . . . . . . 10		8.1. Normative References . . . . . . . . . . . . . . . . . . 10
	8.2. Informative References . . . . . . . . . . . . . . . . . 10		8.2. Informative References . . . . . . . . . . . . . . . . . 10
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
	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 modeling language		encouraging IETF working groups to use the YANG data modeling
	[RFC6020], [RFC7950] and NETCONF protocol [RFC6241] for configuration		language [RFC7950], [RFC7950] and NETCONF protocol [RFC6241] for
	management purposes, especially in new working group charters		configuration management purposes, especially in new working group
	[Writable-MIB-Module-IESG-Statement].		charters [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 data
	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,
	vendor-specific modules and modules provided by end-users.		vendor-specific modules and modules provided by end-users.
	skipping to change at page 3, line 47 ¶		skipping to change at page 3, line 47 ¶
	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.
	It is difficult to determine the module type without inspecting		It is difficult to determine the module type without inspecting
	the YANG module itself. The YANG module name might provide some		the YANG module itself. The YANG module name might provide some
	useful information but is not a definite answer. For example, an		useful information but is not a definite answer. For example, an
	L2VPN YANG module might be a Network Service YANG module, ready to		L2VPN YANG module might be a Network Service YANG module, ready to
	be used by the operators. Alternatively, it might be a Network		be used as a service model by network operator. Alternatively, it
	Element YANG module that contains the L2VPN data definitions		might be a Network Element YANG module that contains the L2VPN
	required to be configured on a single device.		data definitions 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 support in their products. See Figure 1.
	1.1. Terminology		1.1. Terminology
	[RFC7950] 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 hierarchies of schema nodes. With
	used for NETCONF-based operations. With its definitions and the		its definitions and the definitions it imports or includes from
	definitions it imports or includes from elsewhere, a module is		elsewhere, a module is self-contained and "compilable".
	self-contained and "compilable".
	2. First Dimension: YANG Module Abstraction Layers		2. First Dimension: YANG Module Abstraction Layers
	Module 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.
	skipping to change at page 6, line 22 ¶		skipping to change at page 6, line 22 ¶
	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 YANG Modules of		into instance data according to the Network Element YANG Modules of
	the participating network elements. The service-to-element		the participating network elements. The service-to-element
	decomposition is a separate process with details depending on how the		decomposition is a separate process with details depending on how the
	network operator chooses to realize the service. For the purpose of		network operator chooses to realize the service. For the purpose of
	this document we will use the term "orchestrator" to describe a		this document we will use the term "orchestrator" to describe a
	system implementing such a process.		system implementing such a process.
	As an example, the Network Service YANG Module defined in		As an example, the Network Service YANG Module defined in
	[YANG-Data-Model-for-L3VPN-service-delivery] provides an abstract		[draft-ietf-l3sm-l3vpn-service-model] provides an abstract model for
	model for Layer 3 IP VPN service configuration. This module includes		Layer 3 IP VPN service configuration. This module includes e.g. the
	e.g. the concept of a 'site-network-access' to represent bearer and		concept of a 'site-network-access' to represent bearer and connection
	connection parameters. An orchestrator receives operations on		parameters. An orchestrator receives operations on service instances
	service instances according to the service module and decomposes the		according to the service module and decomposes the data into specific
	data into specific Network Element YANG Modules to configure the		Network Element YANG Modules to configure the participating network
	participating network elements to perform the intent of the service.		elements to the service. In the case of the L3VPN module, this would
	In the case of the L3VPN module, this would include translating the		include translating the 'site-network-access' parameters to the
	'site-network-access' parameters to the appropriate parameters in the		appropriate parameters in the Network Element YANG Module implemented
	Network Element YANG Module implemented on the constituent elements.		on the constituent elements.
	Network Service YANG Modules define service 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. External systems can be provisioning systems,
	deployed by network infrastructure teams.		service orchestrators, Operations Support Systems, Business Support
			Systems and applications exposed to network service consumers, being
			either internal network operations peole or extarnal customers.
			These modules are commonly designed, developed and 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
	expense of reusability.		expense of reusability.
	skipping to change at page 7, line 23 ¶		skipping to change at page 7, line 27 ¶
	interface definitions.		interface definitions.
	2.2. Network Element YANG Modules		2.2. Network Element YANG Modules
	Network Element YANG Modules describe the characteristics of a		Network Element YANG Modules describe the characteristics of a
	network device as defined by the vendor of that device. The modules		network device as defined by the vendor of that device. The modules
	are commonly structured around features of the device, e.g. interface		are commonly structured around features of the device, e.g. interface
	configuration [RFC7223], OSPF configuration [I-D.ietf-ospf-yang], and		configuration [RFC7223], OSPF configuration [I-D.ietf-ospf-yang], and
	firewall rules definitions [I-D.ietf-netmod-acl-model].		firewall rules definitions [I-D.ietf-netmod-acl-model].
	The module provides a coherent data model representation of the		Although the [RFC7950], [RFC7950] doesn't explain the relationship of
	software environment consisting of the operating system and		the terms '(YANG) data model' and '(YANG) module', the authors
	applications running on the device. The decomposition, ordering, and		understand there is a 1:1 relationship between a data model and a
	execution of changes to the operating system and application		YANG module, but a data model may also be expressed using a
	configuration is the task of the agent that implements the module.		collection of YANG modules (and submodules). The module provides a
			coherent data model representation of the software environment
			consisting of the operating system and applications running on the
			device. The decomposition, ordering, and execution of changes to the
			operating system and application configuration is the task of the
			agent that implements the module.
	3. Second Dimension: Module Types		3. Second Dimension: Module Types
	This document suggests classifying YANG module types as standard YANG		This document suggests classifying YANG module types as standard YANG
	modules, vendor-specific YANG modules and extensions, or user-		modules, vendor-specific YANG modules and extensions, or 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.
	skipping to change at page 10, line 19 ¶		skipping to change at page 10, line 23 ¶
	alignment (YANG data model versus YANG module), explain 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.
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
	the Network Configuration Protocol (NETCONF)", RFC 6020,
	DOI 10.17487/RFC6020, October 2010,
	<http://www.rfc-editor.org/info/rfc6020>.
	[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,		[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
	and A. Bierman, Ed., "Network Configuration Protocol		and A. Bierman, Ed., "Network Configuration Protocol
	(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,		(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
	<http://www.rfc-editor.org/info/rfc6241>.		<http://www.rfc-editor.org/info/rfc6241>.
	[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>.		<http://www.rfc-editor.org/info/rfc7223>.
	[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>.		<http://www.rfc-editor.org/info/rfc7950>.
	8.2. Informative References		8.2. Informative References
			[draft-ietf-l3sm-l3vpn-service-model]
			"YANG Data Model for L3VPN service delivery",
			<https://tools.ietf.org/id/draft-ietf-l3sm-l3vpn-service-
			model>.
	[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-09 (work in progress), October		draft-ietf-netmod-acl-model-10 (work in progress), March
	2016.		2017.
	[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., Chen, I., and A. Lindem,
	Koushik, "Yang Data Model for OSPF Protocol", draft-ietf-		"Yang Data Model for OSPF Protocol", draft-ietf-ospf-
	ospf-yang-05 (work in progress), July 2016.		yang-06 (work in progress), October 2016.
	[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",
	<https://tools.ietf.org/id/draft-l3vpn-service-yang>.
	Authors' Addresses		Authors' Addresses
	Dean Bogdanovic		Dean Bogdanovic
	Volta Networks, Inc.		Volta Networks, Inc.
	Email: dean@voltanet.io		Email: dean@voltanet.io
	Benoit Claise		Benoit Claise
	Cisco Systems, Inc.		Cisco Systems, Inc.
	De Kleetlaan 6a b1		De Kleetlaan 6a b1
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