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
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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
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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
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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.
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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.
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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.
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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.
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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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