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Versions: (draft-wu-opsawg-service-model-explained)
00 01 02 03 04 05 RFC 8309
OPS Area Working Group Q. Wu
Internet-Draft W. Liu
Intended status: Informational Huawei Technologies
Expires: February 25, 2018 A. Farrel
Juniper Networks
August 24, 2017
Service Models Explained
draft-ietf-opsawg-service-model-explained-02
Abstract
The IETF has produced many data modules in the YANG modeling
language. The majority of these modules are used to construct data
models to model devices or monolithic functions.
A small number of YANG modules have been defined to model services
(for example, the Layer Three Virtual Private Network Service Model
produced by the L3SM working group and documented in RFC 8049).
This document describes service models as used within the IETF, and
also shows where a service model might fit into a Software Defined
Networking architecture. Note that service models do not make any
assumption of how a service is actually engineered and delivered for
a customer; details of how network protocols and devices are
engineered to deliver a service are captured in other models that are
not exposed through the Customer-Provider Interface.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 25, 2018.
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Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terms and Concepts . . . . . . . . . . . . . . . . . . . . . 3
3. Using Service Models . . . . . . . . . . . . . . . . . . . . 6
4. Service Models in an SDN Context . . . . . . . . . . . . . . 8
5. Possible Causes of Confusion . . . . . . . . . . . . . . . . 10
6. Comparison With Other Work . . . . . . . . . . . . . . . . . 12
6.1. Comparison With Network Service Models . . . . . . . . . 12
6.2. Service Delivery and Network Element Model Work . . . . . 14
6.3. Customer Service Model Work . . . . . . . . . . . . . . . 14
6.4. The MEF Architecture . . . . . . . . . . . . . . . . . . 16
7. Further Concepts . . . . . . . . . . . . . . . . . . . . . . 17
7.1. Technology Agnostic . . . . . . . . . . . . . . . . . . . 17
7.2. Relationship to Policy . . . . . . . . . . . . . . . . . 17
7.3. Operator-Specific Features . . . . . . . . . . . . . . . 18
7.4. Supporting Multiple Services . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
9. Manageability Considerations . . . . . . . . . . . . . . . . 19
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
12.1. Normative References . . . . . . . . . . . . . . . . . . 20
12.2. Informative References . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction
In recent years the number of data modules written in the YANG
modeling language [RFC6020] for configuration and monitoring has
blossomed. Many of these are used for device-level configuration
(for example, [RFC7223]) or for control of monolithic functions or
protocol instances (for example, [RFC7407]).
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Within the context of Software Defined Networking (SDN) [RFC7149]
[RFC7426] YANG data models may be used on the interface between a
controller and network devices, and between network orchestrators and
controllers. There may also be a hierarchy of such components with
super controllers, domain controllers, and device controllers all
exchanging information and instructions using YANG models.
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. For example, the Layer
Three Virtual Private Network Service Model (L3SM) [RFC8049]. Such
models may be used in manual and even paper-driven service request
processes with a gradual transition to IT-based mechanisms.
Ultimately they could be used in online, software-driven dynamic
systems, and eventually as part of an SDN system.
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.
The document also shows where a service model might fit into an SDN
architecture, but it is important to note that a service model does
not require or preclude the use of SDN. Note that service models do
not make any assumption of how a service is actually engineered and
delivered to a customer; details of how network protocols and devices
are engineered to deliver a service are captured in other models that
are not exposed through the Customer-Provider Interface.
In summary, a service model is a formal representation of the data
elements that describe a network service as that service is described
to or requested by a customer of a network operator. Details
included in the service model include a description of the service as
experienced by the customer, but not features of how that service is
delivered or realized by the service provider.
Other work on classifying YANG data models has been done in
[RFC8199]. That document provides an important reference for this
document, and also uses the term "service model". Section 6.1 in
this document provides a comparison between these two uses of the
same terminology.
2. Terms and Concepts
Readers should familiarize themselves with the description and
classification of YANG models provided in [RFC8199].
The following terms are used in this document:
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Network Operator: This term is used to refer to the company that
owns and operates one or more networks that provide Internet
connectivity services and/or other services.
Customer: This term refers to someone who purchases a service
(including connectivity) from a network operator. In the context
of this document, a customer is usually a 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 may be the customer of an
optical transport network.
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 [RFC8199]). This
distinction is discussed further in Section 6.
Readers may also refer to [RFC7297] for an example of how an IP
connectivity service may be characterized.
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 as
follows:
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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.
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 be divided into two
categories:
Customer Service Model: A customer service model is used to
describe a service as offered 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" [RFC8049]. 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. Except where
specific technology details (such as encapsulations, or
mechanisms applied on access links) are directly pertinent to
the customer, customer service models are technology agnostic
so that the customer does not have influence over or knowledge
of how the network operator engineers the service.
An example of where such details are relevant to the customer
are when they describe the behavior or interactions on the
interface between the equipment at the customer site (often
referred to as the Customer Edge or CE equipment) and the
equipment at the network operator's site (usually referred to
as the Provider Edge or PE equipment).
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Service Delivery Model: A service delivery model is used by a
network operator to define and manage how a service is
engineered in 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" [RFC8199] and are
consumed by "external systems" such as Operations Support
System (OSS). 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. Service delivery models include technology-specific
modules.
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 distinction 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.
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 [RFC8040] for
interactions "on the wire" between software components with data
encoded in XML or JSON. However, co-located software components
might use an internal API, while systems with more direct human
interactions might use web pages or even paper forms.
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-------------- 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 depends on the commercial and
operational tools, processes, and policies used by the network
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 networks 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 to network orchestrators or
controllers. The use of standard customer service models eases
service delivery by means of automation.
The practicality of customer service models has been repeatedly
debated. It has been suggested that network operators have radically
different business modes and widely diverse commercial offerings
making a common customer service model is impractical. However, the
L3SM [RFC8049] results from the consensus of multiple individuals
working at network operators and offers a common core of service
options that can be augmented according to the needs of individual
network operators.
It has also been suggested that there should be a single, base
customer service module, and that details of individual services
should be offered as extensions or augmentations of this. It is
quite possible that a number of service parameters (such as the
identity and postal address of a customer) will be common and it
would be a mistake to define them multiple times, once in each
customer service model. However, the distinction between a 'module'
and a 'model' should be considered at this point: modules are how the
data for models is logically broken out and documented especially for
re-use in multiple models.
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4. Service Models in an SDN Context
In an SDN system, the management of network resources and protocols
is performed by software systems that determine how best to utilize
the network. Figure 2 shows a sample architectural view of an SDN
system where network elements are programmed by a component called an
"SDN controller" (or "controller" for short), and where controllers
are instructed by an orchestrator that has a wider view of the whole
of, or part of, a network. The internal organization of an SDN
control plane is deployment-specific.
------------------
| |
| Orchestrator |
| |
.------------------.
. : .
. : .
------------ ------------ ------------
| | | | | |
| Controller | | Controller | | Controller |
| | | | | |
------------ ------------ ------------
: . . :
: . . :
: . . :
--------- --------- --------- ---------
| Network | | Network | | Network | | Network |
| Element | | Element | | Element | | Element |
--------- --------- --------- ---------
Figure 2: A Sample SDN Architecture
But a customer's service request is (or should be) technology-
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. The
orchestrator must map the service request to its view, and this
mapping may include a choice of which networks and technologies to
use depending on which service features have been requested.
One implementation option to achieve this mapping is to split the
orchestration function between a "Service Orchestrator" and a
"Network Orchestrator" as shown in Figure 3.
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Customer
------------------ Service ----------
| | Model | |
| Service |<-------->| Customer |
| Orchestrator | (a) | |
| | ----------
------------------
. .
. . (b) -----------
. (b) . ......|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 Example 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 Figure 1 of [RFC7491] shows an interface between an "Application
Service Coordinator" and an "Application-Based Network Operations
Controller".
o Figure 1 of [RFC8199] shows an interface from an OSS or a Business
Support System (BSS) that is expressed in "Network Service YANG
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 northbound of the Network Orchestrator
(labeled "(b)" in Figure 3) to be a "service interface" used by an
application, 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 (labeled
"(a)" in Figure 3) where the service is described by a service model
and the interaction is between customer and network 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. [RFC8199] also terms these data
models as "service models" or "Network Service YANG 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. Thus, this feature is out of scope for
standardized customer service models.
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. As with commercial terms, it is expected that
some network operators will enhance standard customer service
models to include SLA parameters either using their own work or
depending on material from standards bodies that specialize in
this topic, but this feature is out of scope for the IETF's
customer service models.
If a network operator chooses to express an SLA using a data
model, that model might be referenced as an extension or an
augmentation of the customer service model.
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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.
6.1. Comparison With Network Service Models
As previously noted, [RFC8199] 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, operations and notifications of abstract representations of
services 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 [RFC8199] 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. This figure illustrates a functional architecture and an
implementation might choose to make different distinctions and
separations between components so that the functional units and
interfaces illustrated might fall within a single implementation.
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+---------------+
| |
| Customers |
| |
+---------------+
- - - - - - - - - - - - - -
Customer 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
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6.2. Service Delivery and Network Element 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. Some
of these models are classified as service delivery models while
others have details that are related to specific element
configuration and so are classed as network element models (also
called device models).
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 L3VPNs.
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.
6.3. Customer Service Model Work
Several initiatives within the IETF are developing customer service
models. The most advanced presents the L3VPN service as described by
a network operator to a customer. The L3SM is described as in
Figure 5 which is reproduced from [RFC8049]. As can be seen, the
L3SM is a customer service model as described in this document.
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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.ietf-l2sm-l2vpn-service-model]. That model's usage is described
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.
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----------------------------
| 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
LSO architecture. This does not invalidate either approach, but only
observes that they are different.
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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
difference 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, protocols for discovery, 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 and that 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.
As with commercial terms and SLAs discussed in Section 5 it is
expected that some network operators will enhance standard customer
service models to include policy parameters either using their own
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work or depending on specific policy models built in the IETF or
other standards bodies.
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 on the 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. However, the working group was
able to agree on a core set of features that multiple network
operators were willing to consider as "common". They also understood
that should an individual network operator want to describe
additional features (operator-specific features) they could do so by
extending or augmenting the L3SM model.
Thus, when a basic description of a 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 varied 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.
It is expected that, over time, certain elements of the service
models will be seen to repeat in each model. An example of such an
element is the postal address of the customer.
It is anticipated that, while access to such information from each
service model is important, the data will be described in its own
module and may form part of the service model either by inclusion or
by index.
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8. Security Considerations
The interface between customer and service provider is a commercial
interface and needs to be subject to appropriate confidentiality.
Additionally, knowledge of what services are provided to a customer
or delivered by a network operator may supply information that can be
used in a variety of security attacks.
Clearly, the ability to modify information exchanges between customer
and network operator may result in bogus requests, unwarranted
billing, and false expectations. Furthermore, in an automated
system, modifications to service requests or the injection of bogus
requests may lead to attacks on the network and delivery of customer
traffic to the wrong place.
Therefore it is important that the protocol interface used to
exchange service request information between customer and network
operator is subject to authorization, authentication, and encryption.
Equally, all external intefaces, such as any of those between the
functional components in Figure 3 needs to be correctly secured.
This document discusses modeling the information, not how it is
exchanged.
9. Manageability Considerations
This whole document discusses issues related to network management
and control.
It is important to observe that automated service provisioning
resulting from use of a customer service model may result in rapid
and significant changes in traffic load within a network and that
that might have an effect on other services carried in a network.
It is expected, therefore, that a Service Orchestration component has
awareness of other service commitments, that the Network
Orchestration component will not commit network resources to fulfill
a service unless doing so is appropriate, and that a feedback loop
will be provided to report on degradation of the network that will
impact the service.
The operational state of a service does not form part of a customer
service model. However, it is likely that a network operator may
want to report some state information about various components of the
service, and that could be achieved through extensions to the core
service model just as SLA extensions could be made as described in
Section 5.
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10. IANA Considerations
This document makes no requests for IANA action
11. Acknowledgements
Thanks to Daniel King, Xian Zhang, Michael Scharf, Med Boucadair, and
Luis Miguel Contreras Murillo for useful review and comments.
Thanks to Dean Bogdanovic, Tianran Zhou, and Carl Moberg for their
help coordinating with [RFC8199].
Many thanks to Jerry Bonner for spotting a tiny, one-word, but
critical typo.
12. References
12.1. Normative References
[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
Information Models and Data Models", RFC 3444,
DOI 10.17487/RFC3444, January 2003, <https://www.rfc-
editor.org/info/rfc3444>.
[RFC8199] Bogdanovic, D., Claise, B., and C. Moberg, "YANG Module
Classification", RFC 8199, DOI 10.17487/RFC8199, July
2017, <https://www.rfc-editor.org/info/rfc8199>.
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-02 (work in
progress), March 2017.
[I-D.ietf-bess-l2vpn-yang]
Shah, H., Brissette, P., Chen, I., Hussain, I., Wen, B.,
and K. Tiruveedhula, "YANG Data Model for MPLS-based
L2VPN", draft-ietf-bess-l2vpn-yang-06 (work in progress),
June 2017.
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[I-D.ietf-l2sm-l2vpn-service-model]
Wen, B., Fioccola, G., Xie, C., and L. Jalil, "A YANG Data
Model for L2VPN Service Delivery", draft-ietf-l2sm-l2vpn-
service-model-02 (work in progress), July 2017.
[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, <https://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,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined
Networking: A Perspective from within a Service Provider
Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014,
<https://www.rfc-editor.org/info/rfc7149>.
[RFC7223] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
<https://www.rfc-editor.org/info/rfc7223>.
[RFC7297] Boucadair, M., Jacquenet, C., and N. Wang, "IP
Connectivity Provisioning Profile (CPP)", RFC 7297,
DOI 10.17487/RFC7297, July 2014, <https://www.rfc-
editor.org/info/rfc7297>.
[RFC7407] Bjorklund, M. and J. Schoenwaelder, "A YANG Data Model for
SNMP Configuration", RFC 7407, DOI 10.17487/RFC7407,
December 2014, <https://www.rfc-editor.org/info/rfc7407>.
[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, <https://www.rfc-editor.org/info/rfc7426>.
[RFC7491] King, D. and A. Farrel, "A PCE-Based Architecture for
Application-Based Network Operations", RFC 7491,
DOI 10.17487/RFC7491, March 2015, <https://www.rfc-
editor.org/info/rfc7491>.
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[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8049] Litkowski, S., Tomotaki, L., and K. Ogaki, "YANG Data
Model for L3VPN Service Delivery", RFC 8049,
DOI 10.17487/RFC8049, February 2017, <https://www.rfc-
editor.org/info/rfc8049>.
Authors' Addresses
Qin Wu
Huawei Technologies
Email: bill.wu@huawei.com
Will Liu
Huawei Technologies
Email: liushucheng@huawei.com
Adrian Farrel
Juniper Networks
Email: afarrel@juniper.net
Wu, et al. Expires February 25, 2018 [Page 22]
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