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.

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
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 14, 2017.

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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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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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