OPS Area Working Group Q. Wu
Internet-Draft W. Liu
Intended status: Informational Huawei Technologies
Expires: July 4, 2017 A. Farrel
Juniper Networks
December 31, 2016
Service Models Explained
draft-wu-opsawg-service-model-explained-04
Abstract
The IETF has produced a considerable number of data models in the
YANG modelling language. The majority of these are used to model
devices and they allow access for configuration and to read
operational status.
A small number of YANG models are used to model services (for
example, the Layer Three Virtual Private Network Service Model
produced by the L3SM working group).
This document briefly sets out the scope of and purpose of an IETF
service model, and it shows where a service model might fit into a
Software Defined Networking architecture or deployment.
Status of This Memo
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This Internet-Draft will expire on July 2, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terms and Concepts . . . . . . . . . . . . . . . . . . . . . 3
3. Using Service Models . . . . . . . . . . . . . . . . . . . . 5
4. Service Models in an SDN Context . . . . . . . . . . . . . . 6
5. Possible Causes of Confusion . . . . . . . . . . . . . . . . 9
6. Comparison With Other Work . . . . . . . . . . . . . . . . . 10
6.1. Comparison With Network Service Models . . . . . . . . . 11
6.2. Service Delivery Model Work . . . . . . . . . . . . . . . 12
6.3. Customer Service Model Work . . . . . . . . . . . . . . . 13
6.4. The MEF Architecture . . . . . . . . . . . . . . . . . . 14
7. Further Concepts . . . . . . . . . . . . . . . . . . . . . . 15
7.1. Technology Agnostic . . . . . . . . . . . . . . . . . . . 15
7.2. Relationship to Policy . . . . . . . . . . . . . . . . . 15
7.3. Operator-Specific Features . . . . . . . . . . . . . . . 16
7.4. Supporting Multiple Services . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. Manageability Considerations . . . . . . . . . . . . . . . . 16
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
12.1. Normative References . . . . . . . . . . . . . . . . . . 17
12.2. Informative References . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
In recent years the number of data models written in the YANG
modelling language [RFC6020] for configuration and monitoring has
blossomed. Many of these are used for device-level configuration
(for example, [RFC7223]) or for control of protocols (for example,
[RFC7407]).
Within the context of Software Defined Networking (SDN) [RFC7426]
YANG data models may be used on Southbound Interfaces (SBIs) between
a controller and network devices, and between network orchestrators
and controllers. There may also be a hierarchy of such components
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with super-controllers, domain controllers, and device controllers
all exchanging information and instructions using YANG models.
Recently there has been interest in using YANG to define and document
data models that describe services in a portable way that is
independent of which network operator uses the model. These models
may be used in manual and even paper-driven service request processes
moving to IT-based mechanisms. Ultimately they could be used in
online, software-driven dynamic systems.
This document explains the scope and purpose of service models within
the IETF and describes how a service model can be used by a network
operator. Equally, this document clarifies what a service model is
not, and dispels some common misconceptions.
Other work on classifying YANG data models has been done in
[I-D.ietf-netmod-yang-model-classification]. That document provides
an important reference for this document, and also uses the term
"service model". Section 6.1 provides a comparison between these two
classifications.
2. Terms and Concepts
Readers should familiarize themselves with the description and
classification of YANG models provided in
[I-D.ietf-netmod-yang-model-classification].
The following terms are used in this document:
Network Operator: This term is used interchangeably to refer to the
company that owns a network that provides Internet connectivity
and services, or the individual who performs operations and
management on that network.
Customer: Someone who purchases connectivity and other services from
a network operator. In the context of this document, a customer
is usually the company that runs their own network or computing
platforms and wishes to connect to the Internet or between sites.
Such a customer may operate an enterprise network or a data
center. Sometimes this term may also be used to refer to the
individual in such a company who contracts to buy services from a
network operator. A customer as described here is a separate
commercial operation from the network operator, but some companies
may operate with internal customers so that, for example, an IP/
MPLS packet network is the customer of an optical transport
network.
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Service: A network operator delivers one or more services to a
customer. A service in the context of this document (sometimes
called a Network Service) is some form of connectivity between
customer sites and the Internet or between customer sites across
the network operator's network and across the Internet, however a
distinction should be drawn between the parameters that describe a
service as included in a customer service model (q.v.) and a
Service Level Agreement (SLA) as discussed in Section 5 and
Section 7.2.
A service may be limited to simple connectivity (such as IP-based
Internet access), may be a tunnel (such as a virtual circuit), or
may be a more complex connectivity model (such as a multi-site
virtual private network). Services may be further enhanced by
additional functions providing security, load-balancing,
accounting, and so forth. Additionally, services usually include
guarantees of quality, throughput, and fault reporting.
This document makes a distinction between a service as delivered
to a customer (that is, the service as discussed on the interface
between a customer and the network operator) and the service as
realized within the network (as described in
[I-D.ietf-netmod-yang-model-classification]. This distinction is
discussed further in Section 6
Data Model: The concepts of information models and data models are
described in [RFC3444]. That document defines a data model by
contrasting it with the definition of an information model, so it
may be helpful to quote some text to give context within this
document.
The main purpose of an information model is to model managed
objects at a conceptual level, independent of any specific
implementations or protocols used to transport the data. The
degree of specificity (or detail) of the abstractions defined
in the information model depends on the modeling needs of its
designers. In order to make the overall design as clear as
possible, an information model should hide all protocol and
implementation details. Another important characteristic of an
information model is that it defines relationships between
managed objects.
Data models, conversely, are defined at a lower level of
abstraction and include many details. They are intended for
implementors and include protocol-specific constructs.
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Service Model: A service model is a specific type of data model. It
describes a service and the parameters of the service in a
portable way. The service model may divided into to categories:
Customer Service Model: A customer service model is used to
describe a service as offer or delivered to a customer by a
network operator. It can be used by a human (via a user
interface such as a GUI, web form, or CLI) or by software to
configure or request a service and may equally be consumed by a
human (such as via an order fulfillment system) or by a
software component. Such models are sometimes referred to
simply as "service models" [I-D.ietf-l3sm-l3vpn-service-model].
A customer service model is expressed as a core set of
parameters that are common across network operators: additional
features that are specific to the offerings of individual
network operators would be defined in extensions or
augmentations of the model.
Service Delivery Model: A service delivery model is used by a
network operator to define and configure how a service is
provided by the network. It can be used by a human operator
(such as via a management station) or by a software tool to
instruct network components. Such models are sometimes
referred to as "network service models"
[I-D.ietf-netmod-yang-model-classification]. A service
delivery model is expressed as a core set of parameters that
are common across a network type and technology: additional
features that are specific to the configuration of individual
vendor equipment or proprietary protocols would be defined in
extensions or augmentations of the model.
The distinction between a customer service model and a service
delivery model needs to be repeatedly clarified. A customer service
model is not a data model used to directly configure network devices,
protocols, or functions: it is not something that is sent to network
devices (i.e., routers or switches) for processing. Equally, a
customer service model is not a data model that describes how a
network operator realizes and delivers the service described by the
model. This issue is discussed further in later sections.
3. Using Service Models
As already indicated, customer service models are used on the
interface between customers and network operators. This is shown
simply in Figure 1
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The language in which a customer service model is described is a
choice for whoever specifies the model. The IETF uses the YANG data
modeling language defined in [RFC6020]
The encoding and communication protocol used to exchange a customer
service model between customer and network operator are deployment-
and implementation-specific. The IETF has standardized the NETCONF
protocol [RFC6241] and the RESTCONF protocol
[I-D.ietf-netconf-restconf] for interactions "on the wire" between
software components with data encoded in XML or JSON. However, co-
located software components might use an API, while systems with more
direct human interactions might use web pages or even paper forms.
-------------- Customer ----------------------
| | Service Model | |
| Customer | <-----------------> | Network Operator |
| | | |
-------------- ----------------------
Figure 1: The Customer Service Models used on the Interface between
Customers and Network Operators
How a network operator processes a customer's service request
described with a customer service model will depend on the commercial
and operational tools, processes, and policies used by the operator.
These may vary considerably from one network operator to another.
However, the intent is that the network operator maps the service
request into configuration and operational parameters that control
one or more network to deliver the requested services. That means
that the network operator (or software run by the network operator)
takes the information in the customer service model and determines
how to deliver the service by enabling and configuring network
protocols and devices. They may achieve this by constructing service
delivery models and passing them southbound to network orchestrators
or controllers.
4. Service Models in an SDN Context
In an SDN system, the control and configuration of network resources
and protocols is performed by software systems that determine how
best to utilize the network. Figure 2 shows a common architectural
view of an SDN system where network elements are programmed by a
component called a controller, and where controllers are instructed
by an orchestrator that has a wider view of the whole of, or part of,
a network.
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------------------
| |
| Orchestrator |
| |
.------------------.
. : .
. : .
------------ ------------ ------------
| | | | | |
| Controller | | Controller | | Controller |
| | | | | |
------------ ------------ ------------
: . . :
: . . :
: . . :
--------- --------- --------- ---------
| Network | | Network | | Network | | Network |
| Element | | Element | | Element | | Element |
--------- --------- --------- ---------
Figure 2: A Common SDN Architecture
But a customer' service request is (or should be) network-agnostic.
That is, there should be an independence between the behavior and
functions that a customer requests and the technology that the
network operator has available to deliver the service. This means
that the service request must be mapped to the orchestrator's view,
and this mapping may include a choice of which networks to use
depending on what technologies are available and which service
features have been requested.
This mapping can be achieved by splitting the orchestration function
between a "Service Orchestrator" and a "Network Orchestrator" as
shown in Figure 3. In a system that is fully implemented in
software, this could lead to agile service delivery or service
automation.
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Customer
------------------ Service ----------
| | Model | |
| Service |<-------->| Customer |
| Orchestrator | | |
| | ----------
------------------
. .
. . -----------
. . ......|Application|
. . : | BSS/OSS |
. . : -----------
. Service Delivery . :
. Model . :
------------------ ------------------
| | | |
| Network | | Network |
| Orchestrator | | Orchestrator |
| | | |
.------------------ ------------------.
. : : .
. : Network Configuration : .
. : Model : .
------------ ------------ ------------ ------------
| | | | | | | |
| Controller | | Controller | | Controller | | Controller |
| | | | | | | |
------------ ------------ ------------ ------------
: . . : :
: . . Device : :
: . . Configuration : :
: . . Model : :
--------- --------- --------- --------- ---------
| Network | | Network | | Network | | Network | | Network |
| Element | | Element | | Element | | Element | | Element |
--------- --------- --------- --------- ---------
Figure 3: An SDN Architecture with a Service Orchestrator
Figure 3 also shows where different data models might be applied
within the architecture.
The split between control components that exposes a "service
interface" is present in many figures showing extended SDN
architectures:
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o Figure 1 of [RFC7426] shows a separation of the "Application
Plane", the "Network Services Abstraction Layer (NSAL)", and the
"Control Plane". It marks the "Service Interface" as situated
between the NSAL and the Control Plane.
o [RFC7491] describes an interface between an "Application Service
Coordinator" and an "Application-Based Network Operations
Controller".
o Figure 1 of [I-D.ietf-netmod-yang-model-classification] shows an
interface from an Operations Support System (OSS) or a Business
Support System (BSS) that is expressed in "service models".
This can all lead to some confusion around the definition of a
"service interface" and a "service model". Some previous literature
considers the interface that is northbound of the Network
Orchestrator to be a "service interface" used by an application (as
shown in Figure 3), but the service described at this interface is
network-centric and is aware of many features such as topology,
technology, and operator policy. Thus, we make a distinction between
this type of service interface and the more abstract service
interface where the service is described by a service model and the
interaction is between customer and operator. Further discussion of
this point is provided in Section 5.
5. Possible Causes of Confusion
In discussing service models, there are several possible causes of
confusion:
o The services we are discussing are services provided by network
operators to customers. This is a completely different thing to
"Foo as a Service" (for example, Infrastructure as a Service
(IaaS)) where a service provider offers a service at some location
that is reached across a network. The confusion arises not only
because of the use of the word "service", but also because network
operators may offer value-added services as well as network
connection services to their customers.
o Network operation is completely out of scope in the discussion of
services between a network operator and a customer. That means
that the customer service model does not reveal to the customer
anything about how the network operator delivers the service. The
model does not expose details of technology or network resources
used to provide the service. For example, in the simple case of
point-to-point virtual link connectivity provided by a network
tunnel (such as an MPLS pseudowire) the network operator does not
expose the path through the network that the tunnel follows. Of
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course, this does not preclude the network operator from taking
guidance from the customer (such as to avoid routing traffic
through a particular country) or from disclosing specific details
(such as might be revealed by a route trace), but these are not
standard features of the service as described in the customer
service model.
o The network operator may use further data models (service delivery
models) that help to describe how the service is realized in the
network. These models might be used on the interface between the
Service Orchestrator and the Network Orchestrator as shown in
Figure 3 and might include many of the pieces of information from
the customer service model alongside protocol parameters and
device configuration information.
[I-D.ietf-netmod-yang-model-classification] also terms these data
models as "service models" and a comparison is provided in
Section 6.1. It is important that the Service Orchestrator should
be able to map from a customer service model to these service
delivery models, but they are not the same things.
o Commercial terms are generally not a good subject for
standardization. It is possible that some network operators will
enhance standard customer service models to include commercial
information, but the way this is done is likely to vary widely
between network operators.
o Service Level Agreements (SLAs) have a high degree of overlap with
the definition of services present in customer service models.
Requests for specific bandwidth, for example, might be present in
a customer service model, and agreement to deliver a service is a
commitment to the description of the service in the customer
service model. However, SLAs typically include a number of fine-
grained details about how services are allowed to vary, by how
much, and how often. SLAs are also linked to commercial terms
with penalties and so forth, and so are also not good topics for
standardization.
6. Comparison With Other Work
Other work has classified YANG models, produced parallel
architectures, and developed a range of YANG models. This section
briefly examines that other work and shows how it fits with the
description of service models introduced in this document.
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6.1. Comparison With Network Service Models
As previously noted, [I-D.ietf-netmod-yang-model-classification]
provides a classification of YANG data models. It introduces the
term "Network Service YANG Module" to identify the type of model used
to "describe the configuration, state data and operations of an
abstract representation of a service implemented on one or multiple
network elements." These are service delivery models as described in
this document, that is, they are the models used on the interface
between the Service Orchestrator or OSS/BSS and the Network
Orchestrator as shown in Figure 3.
Figure 1 of [I-D.ietf-netmod-yang-model-classification] can be
modified to make this more clear and to add an additional example of
a Network Service YANG model as shown in Figure 4.
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+---------------+
| |
| Customers |
| |
+---------------+
- - - - - - - - - - - - - -
Service YANG Modules
+--------------------------+ +--------------------------+
| | | Operations and Business |
| Service Orchestrator | | Support Systems |
| | | (OSS/BSS) |
+--------------------------+ +--------------------------+
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Network Service YANG Modules
+------------+ +-------------+ +-------------+ +-------------+
| | | | | | | |
| - L2VPN | | - L2VPN | | EVPN | | 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 4: YANG Module Layers Showing Service Models
6.2. Service Delivery Model Work
A number of IETF working groups are developing YANG models related to
services. These models focus on how the network operator configures
the network through protocols and devices to deliver a service.
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A sample set of these models is listed here:
o [I-D.dhjain-bess-bgp-l3vpn-yang] defines a YANG model that can be
used to configure and manage BGP Layer 3 VPNs.
o [I-D.ietf-bess-l2vpn-yang] documents a YANG model that it is
expected will be used by the management tools run by the network
operators in order to manage and monitor the network resources
that they use to deliver L2VPN services.
o [I-D.ietf-bess-evpn-yang] defines YANG models for delivering an
Ethernet VPN service.
All of these models are service delivery models in the context of
this document.
6.3. Customer Service Model Work
Several initiatives within the IETF are developing customer service
models. The most advanced presents the Layer Three Virtual Private
Network (L3VPN) service as described by a network operator to a
customer. This L3VPN service model (L3SM) is documented in
[I-D.ietf-l3sm-l3vpn-service-model] where its usage is described as
in Figure 5 which is reproduced from that document. As can be seen,
the L3SM is a customer service model as described in this document.
L3VPN-SVC |
MODEL |
|
+------------------+ +-----+
| Orchestration | < --- > | OSS |
+------------------+ +-----+
| |
+----------------+ |
| Config manager | |
+----------------+ |
| |
| Netconf/CLI ...
| |
+------------------------------------------------+
Network
Figure 5: The L3SM Service Architecture
A Layer Two VPN service model (L2SM) is defined in
[I-D.wen-l2sm-l2vpn-service-model]. That model's usage is described
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as in Figure 6 which is a reproduction of Figure 5 from that
document. As can be seen, the L2SM is a customer service model as
described in this document.
----------------------------
| Customer Service Requester |
----------------------------
|
L2VPN |
Service |
Model |
|
-----------------------
| Service Orchestration |
-----------------------
|
| Service +-------------+
| Delivery +------>| Application |
| Model | | BSS/OSS |
| V +-------------+
-----------------------
| Network Orchestration |
-----------------------
| |
+----------------+ |
| Config manager | |
+----------------+ | Device
| | Models
| |
--------------------------------------------
Network
Figure 6: The L2SM Service Architecture
6.4. The MEF Architecture
The MEF Forum has developed an architecture for network management
and operation. It is documented as the Lifecycle Service
Orchestration (LSO) Reference Architecture and illustrated in
Figure 2 of [MEF-55].
The work of the MEF Forum embraces all aspects of Lifecycle Service
Orchestration including billing, SLAs, order management, and life-
cycle management. The IETF's work on service models is typically
smaller offering a simple, self-contained service YANG module. Thus,
it may be impractical to fit IETF service models into the MEF Forum
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LSO architecture. This does not invalidate either approach, but only
observes that they are different.
7. Further Concepts
This section introduces a few further, more advanced concepts
7.1. Technology Agnostic
Service models should generally be technology agnostic. That is to
say, the customer should not care how the service is provided so long
as the service is delivered.
However, some technologies reach the customer site and make a
definition to the type of service delivered. Such features do need
to be described in the service model.
Two examples are:
o The data passed between customer equipment and network operator
equipment will be encapsulated in a specific way, and that data
plane type forms part of the service.
o Protocols that are run between customer equipment and network
operator equipment (for example, Operations, Administration, and
Maintenance protocols, or protocols for exchanging routing
information) need to be selected and configured as part of the
service description.
7.2. Relationship to Policy
Policy appears as a crucial function in many places during network
orchestration. A Service Orchestrator will, for example, apply the
network operator's policies to determine how to provide a service for
a particular customer (possibly considering commercial terms).
However, the policies within a service model are limited to those
over which a customer has direct influence, but which are acted on by
the network operator.
The policies that express desired behavior of services on occurrence
of specific events are close to SLA definitions: they should only be
included in the base service model where they are common to all
network operators' offerings. Policies that describe who at a
customer may request or modify services (that is, authorization) are
close to commercial terms: they, too, should only be included in the
base service model where they are common to all network operators'
offerings.
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Nevertheless, policy is so important that all service models should
be designed to be easily extensible to allow policy components to be
added and associated with services as needed.
7.3. Operator-Specific Features
When work in Layer Three Virtual Private Network Service Model (L3SM)
was started, there was some doubt as to whether network operators
would be able to agree on a common description of the services that
they offer to their customers because, in a competitive environment,
each markets the services in a different way with different
additional features. Thus, when a basic description of the core
service is agreed and documented in a service model, it is important
that that model should be easily extended or augmented by each
network operator so that the standardized model can be used in a
common way and only the operator- specific features vary from one
environment to another.
7.4. Supporting Multiple Services
Network operators will, in general, offer many different services to
their customers. Each would normally be the subject of a separate
service model.
It is an implementation and deployment choice whether all service
models are processed by a single Service Orchestrator that can
coordinate between the different services, or whether each service
model is handled by a specialized Service Orchestrator able to
provide tuned behavior for a specific service.
8. Security Considerations
TBD
9. Manageability Considerations
TBD
10. IANA Considerations
This document makes no requests for IANA action
11. Acknowledgements
Thanks to Daniel King, Xian Zhang, and Michael Scharf for useful
review and comments.
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12. References
12.1. Normative References
[I-D.ietf-l3sm-l3vpn-service-model]
Litkowski, S., Tomotaki, L., and K. Ogaki, "YANG Data
Model for L3VPN service delivery", draft-ietf-l3sm-l3vpn-
service-model-19 (work in progress), November 2016.
[I-D.ietf-netmod-yang-model-classification]
Bogdanovic, D., Claise, B., and C. Moberg, "YANG Module
Classification", draft-ietf-netmod-yang-model-
classification-04 (work in progress), October 2016.
[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
Information Models and Data Models", RFC 3444,
DOI 10.17487/RFC3444, January 2003,
<http://www.rfc-editor.org/info/rfc3444>.
[RFC7426] Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
Defined Networking (SDN): Layers and Architecture
Terminology", RFC 7426, DOI 10.17487/RFC7426, January
2015, <http://www.rfc-editor.org/info/rfc7426>.
12.2. Informative References
[I-D.dhjain-bess-bgp-l3vpn-yang]
Jain, D., Patel, K., Brissette, P., Li, Z., Zhuang, S.,
Liu, X., Haas, J., Esale, S., and B. Wen, "Yang Data Model
for BGP/MPLS L3 VPNs", draft-dhjain-bess-bgp-l3vpn-yang-02
(work in progress), August 2016.
[I-D.ietf-bess-evpn-yang]
Brissette, P., Sajassi, A., Shah, H., Li, Z.,
Tiruveedhula, K., Hussain, I., and J. Rabadan, "Yang Data
Model for EVPN", draft-ietf-bess-evpn-yang-01 (work in
progress), July 2016.
[I-D.ietf-bess-l2vpn-yang]
Shah, H., Brissette, P., Chen, I., Hussain, I., and B.
Wen, "YANG Data Model for MPLS-based L2VPN", draft-ietf-
bess-l2vpn-yang-02 (work in progress), October 2016.
[I-D.ietf-netconf-restconf]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", draft-ietf-netconf-restconf-18 (work in
progress), October 2016.
Wu, et al. Expires July 2, 2017 [Page 17]
Internet-Draft Service Models Explained December 2016
[I-D.wen-l2sm-l2vpn-service-model]
Wen, B., Fioccola, G., Xie, C., and L. Jalil, "A YANG Data
Model for L2VPN Service Delivery", draft-wen-l2sm-l2vpn-
service-model-03 (work in progress), October 2016.
[MEF-55] MEF Forum, "Service Operations Specification MEF 55 :
Lifecycle Service Orchestration (LSO) Reference
Architecture and Framework", March 2016.
[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.,
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>.
[RFC7407] Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for
SNMP Configuration", RFC 7407, DOI 10.17487/RFC7407,
December 2014, <http://www.rfc-editor.org/info/rfc7407>.
[RFC7491] King, D. and A. Farrel, "A PCE-Based Architecture for
Application-Based Network Operations", RFC 7491,
DOI 10.17487/RFC7491, March 2015,
<http://www.rfc-editor.org/info/rfc7491>.
Authors' Addresses
Qin Wu
Huawei Technologies
Email: bill.wu@huawei.com
Will Liu
Huawei Technologies
Email: liushucheng@huawei.com
Wu, et al. Expires July 2, 2017 [Page 18]
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Adrian Farrel
Juniper Networks
Email: afarrel@juniper.net
Wu, et al. Expires July 2, 2017 [Page 19]