Internet DRAFT - draft-li-intent-classification
draft-li-intent-classification
Internet Engineering Task Force C. Li
Internet-Draft China Telecom
Intended status: Informational Y. Cheng
Expires: September 14, 2017 China Unicom
T. Peng
X. Song
J. Strassner
Huawei Technologies
March 13, 2017
Internet Classfication
draft-li-intent-classification-00
Abstract
Intent is an abstract high-level policy used to operate the network
RFC 7575 [RFC7575]. Intent management system includes an interface
for users to input requests and an engine to manage the requests. Up
to now, there is no commonly agreed interface or model of intent.
This document describes different ways to classify intent, and an
associated taxonomy of this classification.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. The Policy Continuum . . . . . . . . . . . . . . . . . . . . 3
5. Functional Characteristics and Behavior . . . . . . . . . . . 3
5.1. Persistence . . . . . . . . . . . . . . . . . . . . . . . 3
5.2. Abstracting Intent Operation . . . . . . . . . . . . . . 4
5.3. Policy Subjects and Policy Targets . . . . . . . . . . . 4
5.4. Policy Scope . . . . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Different SDOs (such as [ANIMA][ONF]) have proposed intent as a
declarative interface for defining a set of network operations to
execute. Although there is no common definition or model of intent
which are agreed by all SDOs, there are several shared principles:
o intent should be declarative, using and depending on as few
deployment details as possible
o intent should provide an easy-to-use interface, and use
terminology and concepts familiar to its target audience
o intent should be vendor-independent and portable across platforms
o the intent framework should be able to detect and resolve
conflicts between multiple intents
SDOs have different perspectives on what intent is, what set of
actors it is intended to serve, and how it should be used. This
document provides several dimensions to classify intents.
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2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Acronyms
CLI: Command Line Interface
SDO: Standards Development Organisation
SUPA: Simplified Use of Policy Abstractions
VPN: Virtual Private Network
4. The Policy Continuum
The Policy Continuum defines the set of actors that will create,
read, use, and manage policy. Each set of actors has their own
terminology and concepts that they are familiar with. This captures
the fact that business people do not want to use CLI, and network
operations center personnel do not want to use non-technical
languages.
5. Functional Characteristics and Behavior
Intent can be used to operate immediately on a target (much like
issuing a command), or whenever it is appropriate (e.g., in response
to an event). In either case, intent has a number of behaviors that
serve to further organize its purpose, as described by the following
subsections.
5.1. Persistence
Intents can be classified into transient/persistent intents.
If intent is transient, it has no lifecycle management. As soon as
the specified operation is successfully carried out, the intent is
finished, and can no longer affect the target object.
If the intent is persistent, it has lifecycle management. Once the
intent is successfully activated and deployed, the system will keep
all relevant intents active until they are deactivated or removed.
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5.2. Abstracting Intent Operation
The modeling of Policies can be abstracting using the following
three-tuple:
{Context, Capabilities, Constraints}
Context grounds the policy, and determines if it is relevant or not
for the current situation. Capabilities describe the functionality
that the policy can perform. Capabilities take different forms,
depending on the expressivity of the policy as well as the
programming paradigm(s) used. Constraints define any restrictions on
the capabilities to be used for that particular context. Metadata
can be optionally attached to each of the elements of the three-
tuple, and may be used to describe how the policy should be used and
how it operates, as well as prescribe any operational dependencies
that must be taken into account. Put another way:
o Context selects policies based on applicability
o Capabilities describe the functionality provided by the policy
o Constraints restrict the capabilities offered and/or the behavior
of the policy
Hence, the difference between imperative, declarative, and other
types of policies lies in how the elements of this three-tuple are
used according to that particular programming paradigm. This is how
[SUPA] was designed: a Policy is a container that aggregates a set of
statements .
5.3. Policy Subjects and Policy Targets
Policy subject is the actor that performs the action specified in the
policy. It can be the intent management system which executes the
policy. Policy target is a set of managed objects which may be
affected in the policy enforcement.
5.4. Policy Scope
Policies used to manage the behavior of objects that they are applied
to (e.g., the target of the policy). It is useful to differentiate
between the following categories of targets:
o Policies defined for the Customer or End-User
o Policies defined for the management system to act on objects in
the domain that the management system controls
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o Policies defined for the management system to act on objects in
one or more domains that the management system does not directly
control
The different origins and views of these three categories of actors
lead to the following important differences:
- Network Knowledge. This area is explored using three exemplary
actors that have different knowledge of the network.
Customers and end-users do not necessarily know the functional and
operational details of the network that they are using. Furthermore,
most of the actors in this category lack skills to understand such
details; in fact, such knowledge is typically not relevant to their
job. In addition, the network may not expose these details to its
users. This class of actor focuses on the applications that they
run, and uses services offered by the network. Hence, they want to
specify policies that provide consistent behavior according to their
business needs. They do not have to worry about how the policies are
deployed onto the underlying network, and especially, whether the
policies need to be translated to different forms to enable network
elements to understand them.
Application developers work in a set of abstractions defined by their
application and programming environment(s). For example, many
application developers think in terms of objects (for example, a
VPN). While this makes sense to the application developer, most
network devices do not have a VPN object per se; rather, the VPN is
formed through a set of configuration statements for that device in
concert with configuration statements for the other devices that
together make up the VPN. Hence, the view of application developers
matches the services provided by the network, but may not directly
correspond to other views of other actors.
Management personnel, such as network Administrators, have complete
knowledge of the underlying network. However, they may not
understand the details of the applications and services of Customers
and End-Users.
- Automation. In theory, intents from both end-user and management
system can be automated. In practice, most intents from end-user are
created manually according to business request. End-users do not
create or alter intents unless there is change in business. Intents
from management systems can be created or altered to reflect with
network policy change. For example, end-users create intents to set
up paths between hosts, while the management system creates an intent
to set a global link utilization limit.
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6. Acknowledgements
The authors would like to thank Will (Shucheng) Liu for his comments
to this document.
7. IANA Considerations
This document includes no request to IANA.
8. Security Considerations
This document does not have any Security Considerations.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC7575] Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
Networking: Definitions and Design Goals", RFC 7575,
DOI 10.17487/RFC7575, June 2015,
<http://www.rfc-editor.org/info/rfc7575>.
[SUPA] Strassner, J., "Simplified Use of Policy Abstractions",
2017, <https://datatracker.ietf.org/doc/draft-ietf-supa-
generic-policy-info-model/?include_text=1>.
9.2. Informative References
[ANIMA] Du, Z., "ANIMA Intent Policy and Format", 2017,
<https://datatracker.ietf.org/doc/draft-du-anima-an-
intent/>.
[ONF] ONF, "Intent Definition Principles", 2017,
<https://www.opennetworking.org/images/stories/downloads/
sdn-resources/technical-reports/TR-
523_Intent_Definition_Principles.pdf>.
[ONOS] ONOS, "ONOS Intent Framework", 2017,
<https://wiki.onosproject.org/display/ONOS/
Intent+Framework/>.
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[RFC3198] Westerinen, A., Schnizlein, J., Strassner, J., Scherling,
M., Quinn, B., Herzog, S., Huynh, A., Carlson, M., Perry,
J., and S. Waldbusser, "Terminology for Policy-Based
Management", RFC 3198, DOI 10.17487/RFC3198, November
2001, <http://www.rfc-editor.org/info/rfc3198>.
Authors' Addresses
Chen Li
China Telecom
No.118 Xizhimennei street, Xicheng District
Beijing 100035
P.R. China
Email: lichen.bri@chinatelecom.cn
Ying Cheng
China Unicom
No.21 Financial Street, XiCheng District
Beijing 100033
P.R. China
Email: chengying10@chinaunicom.cn
Tao Peng
Huawei Technologies
Bantian
Shenzhen, Longgang District 518129
P.R. China
Email: dr.pengtao@huawei.com
Xiaolin Song
Huawei Technologies
Bantian
Shenzhen 518129
P.R. China
Email: sxlin@huawei.com
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John Strassner
Huawei Technologies
2330 Central Expressway
Santa Clara 95138
P.R. China
Email: john.sc.strassner@huawei.com
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