I2NSF Working Group                                        J. Jeong, Ed.
Internet-Draft                                                 P. Lingga
Intended status: Standards Track                                 J. Yang
Expires: 30 October 2022                                          J. Kim
                                                 Sungkyunkwan University
                                                           28 April 2022


   Guidelines for Security Policy Translation in Interface to Network
                           Security Functions
            draft-yang-i2nsf-security-policy-translation-11

Abstract

   This document proposes the guidelines for security policy translation
   in Interface to Network Security Functions (I2NSF) Framework.  When
   I2NSF User delivers a high-level security policy for a security
   service, Security Policy Translator in Security Controller translates
   it into a low-level security policy for Network Security Functions
   (NSFs).  For this security policy translation, this document
   specifies the relation between a high-level security policy based on
   the Consumer-Facing Interface YANG data model and a low-level
   security policy based on the NSF-Facing Interface YANG data model.
   Also, it describes an architecture of a security policy translator
   along with an NSF database, and the process of security policy
   translation with the NSF database.

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 https://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 30 October 2022.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of 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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Necessity for Security Policy Translator  . . . . . . . . . .   3
   4.  Relation between Consumer-Facing Interface and NSF-Facing
           Interface YANG Data Models  . . . . . . . . . . . . . . .   4
     4.1.  The CFI and NFI Top-Level YANG Trees Comparison . . . . .   5
     4.2.  The CFI and NFI Rule-Level YANG Trees Comparison  . . . .   6
       4.2.1.  The CFI and NFI Event YANG Data Models Comparison . .   7
       4.2.2.  The CFI and NFI Condition YANG Data Models
               Comparison  . . . . . . . . . . . . . . . . . . . . .   7
       4.2.3.  The CFI and NFI Action YANG Data Models Comparison  .  14
   5.  Design of Security Policy Translator  . . . . . . . . . . . .  16
     5.1.  Overall Structure of Security Policy Translator . . . . .  16
     5.2.  DFA-based Data Extractor  . . . . . . . . . . . . . . . .  18
       5.2.1.  Design of DFA-based Data Extractor  . . . . . . . . .  18
       5.2.2.  Example Scenario for Data Extractor . . . . . . . . .  19
     5.3.  Data Converter  . . . . . . . . . . . . . . . . . . . . .  24
       5.3.1.  Role of Data Converter  . . . . . . . . . . . . . . .  24
       5.3.2.  NSF Database  . . . . . . . . . . . . . . . . . . . .  25
       5.3.3.  Data Conversion in Data Converter . . . . . . . . . .  27
       5.3.4.  Data Model Mapper . . . . . . . . . . . . . . . . . .  28
       5.3.5.  Policy Provisioning . . . . . . . . . . . . . . . . .  31
     5.4.  Policy Generator  . . . . . . . . . . . . . . . . . . . .  33
   6.  Implementation Considerations . . . . . . . . . . . . . . . .  34
     6.1.  Data Model Auto-adaptation  . . . . . . . . . . . . . . .  35
     6.2.  Data Conversion . . . . . . . . . . . . . . . . . . . . .  35
     6.3.  Policy Provisioning . . . . . . . . . . . . . . . . . . .  36
   7.  Features of Security Policy Translator Design . . . . . . . .  36
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  36
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  36
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  36
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  37
     10.2.  Informative References . . . . . . . . . . . . . . . . .  38
   Appendix A.  Mapping Information for Data Conversion  . . . . . .  38
   Appendix B.  Acknowledgments  . . . . . . . . . . . . . . . . . .  43
   Appendix C.  Contributors . . . . . . . . . . . . . . . . . . . .  43




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   Appendix D.  Changes from
           draft-yang-i2nsf-security-policy-translation-10 . . . . .  44
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  44

1.  Introduction

   This document proposes the guidelines for security policy translation
   in Interface to Network Security Functions (I2NSF) Framework
   [RFC8329].  First of all, this document explains the necessity of a
   security policy translator (shortly called policy translator) in the
   I2NSF framework.

   The policy translator resides in Security Controller in the I2NSF
   framework and translates a high-level security policy to a low-level
   security policy for Network Security Functions (NSFs).  A high-level
   policy is specified by I2NSF User in the I2NSF framework and is
   delivered to Security Controller via Consumer-Facing Interface
   [I-D.ietf-i2nsf-consumer-facing-interface-dm].  It is translated into
   a low-level policy by Policy Translator in Security Controller and is
   delivered to NSFs to execute the rules corresponding to the low-level
   policy via NSF-Facing Interface
   [I-D.ietf-i2nsf-nsf-facing-interface-dm].

2.  Terminology

   This document uses the terminology specified in [RFC8329].

3.  Necessity for Security Policy Translator

   Security Controller acts as a coordinator between I2NSF User and
   NSFs.  Also, Security Controller has capability information of NSFs
   that are registered via Registration Interface
   [I-D.ietf-i2nsf-registration-interface-dm] by Developer's Management
   System [RFC8329].  As a coordinator, Security Controller needs to
   generate a low-level policy in the form of security rules intended by
   the high-level policy, which can be understood by the corresponding
   NSFs.

   A high-level security policy is specified by RESTCONF/YANG
   [RFC8040][RFC6020], and a low-level security policy is specified by
   NETCONF/YANG [RFC6241][RFC6020].  The translation from a high-level
   security policy to the corresponding low-level security policy will
   be able to rapidly elevate I2NSF in real-world deployment.  A rule in
   a high-level policy can include a broad target object, such as
   employees in a company for a security service (e.g., firewall and web
   filter).  Such employees may be from human resource (HR) department,
   software engineering department, and advertisement department.  A
   keyword of employee needs to be mapped to these employees from



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   various departments.  This mapping needs to be handled by a security
   policy translator in a flexible way while understanding the intention
   of a policy specification.  Let us consider the following two
   policies:

   *  Block my son's computers from malicious websites.

   *  Drop packets from the IP address 10.0.0.1 and 10.0.0.3 to harm.com
      and illegal.com

   The above two sentences are examples of policies for blocking
   malicious websites.  Both policies are for the same operation.
   However, NSF cannot understand the first policy, because the policy
   does not have any specified information for NSF.  To set up the
   policy at an NSF, the NSF MUST receive at least the source IP address
   and website address for an operation.  It means that the first
   sentence is NOT compatible for an NSF policy.  Conversely, when I2NSF
   Users request a security policy to the system, they never make a
   security policy like the second example.  For generating a security
   policy like the second sentence, the user MUST know that the NSF
   needs to receive the specified information, source IP address and
   website address.  It means that the user understands the NSF
   professionally, but there are not many professional users in a small
   size of company or at a residential area.  In conclusion, the I2NSF
   User prefers to issue a security policy in the first sentence, but an
   NSF will require the same policy as the second sentence with specific
   information.  Therefore, an advanced translation scheme of security
   policy is REQUIRED in I2NSF.

   This document proposes an approach using Automata theory [Automata]
   for the policy translation, such as Deterministic Finite Automaton
   (DFA).  Note that Automata theory is the foundation of programming
   language and compiler.  Thus, with this approach, I2NSF User can
   easily specify a high-level security policy that will be enforced
   into the corresponding NSFs with a compatibly low-level security
   policy with the help of Security Policy Translator.  Also, for easy
   management, a modularized translator structure is proposed.

4.  Relation between Consumer-Facing Interface and NSF-Facing Interface
    YANG Data Models

   The Consumer-Facing Interface (CFI) YANG data model
   [I-D.ietf-i2nsf-consumer-facing-interface-dm] and NSF-Facing
   Interface (NFI) YANG data model
   [I-D.ietf-i2nsf-nsf-facing-interface-dm] are two data models designed
   with different objectives in mind.  The CFI is designed to be used by
   someone with little knowledge of network security can configure the
   NSFs by specifying the required information, their data types, and



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   encoding schemes as a high-level policy.  The NFI is designed to
   provide detailed security policy configuration for the NSFs as a low-
   level policy that can be used by the NSFs to deploy security
   services.  But even with the distinct objectives for the data models,
   the attributes between the two data models are constructed to have a
   relation for the purpose of automation.  Thus, this section provides
   the information of the relationship between the attributes in the CFI
   and NFI YANG data model.

4.1.  The CFI and NFI Top-Level YANG Trees Comparison

   Consumer-Facing Interface (CFI):
   module: ietf-i2nsf-cfi-policy
     +--rw i2nsf-cfi-policy* [name]
        +--rw name                   string
        +--rw language?              string
        +--rw resolution-strategy?   identityref
        +--rw rules* [name]
        |  ...
        +--rw endpoint-groups
        |  ...
        +--rw threat-prevention
           ...

   NSF-Facing Interface (NFI):
   module: ietf-i2nsf-policy-rule-for-nsf
     +--rw i2nsf-security-policy* [name]
        +--rw name                   string
        +--rw language?              string
        +--rw priority-usage?        identityref
        +--rw resolution-strategy?   identityref
        +--rw default-action?        identityref
        +--rw rules* [name]
        |  ...
        +--rw rule-group
           ...

               Figure 1: The CFI and NFI Top-Level YANG Trees

   Figure 1 shows the top-level of the CFI and NFI YANG Trees.  The CFI
   and NFI top-level provides the basic security policy information such
   as name of a policy, language tag, and resolution-strategy.  Both
   data models also provide list of rules to be executed to perform the
   network security services.

   The differences of the top-level data models are default action and
   priority usage are not provided in CFI YANG data model.  This is
   because the philosophy of CFI, i.e., To make CFI as simple as



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   possible for the user.  But this attributes can be given by the
   Security Controller with a default value in the translation process.
   Another important distinct point is CFI YANG data model also provides
   endpoint groups and threat prevention to register high-level
   information (e.g., mapping a user to an IP address) to the database
   for high-level configuration that can be used to translate the high-
   level policy into the low-level policy.

4.2.  The CFI and NFI Rule-Level YANG Trees Comparison

   Consumer-Facing Interface (CFI):
    +--rw rules* [name]
        |  +--rw name         string
        |  +--rw priority?    uint8
        |  +--rw event
        |  |  ...
        |  +--rw condition
        |  |  ...
        |  +--rw actions
        |     ...

   NSF-Facing Interface (NFI):
    +--rw rules* [name]
        |  +--rw name               string
        |  +--rw description?       string
        |  +--rw priority?          uint8
        |  +--rw enable?            boolean
        |  +--rw long-connection
        |  |  +--rw enable?     boolean
        |  |  +--rw duration?   uint32
        |  +--rw event
        |  |  ...
        |  +--rw condition
        |  |  ...
        |  +--rw action
        |     ...


              Figure 2: The CFI and NFI Rule-Level YANG Trees

   Figure 2 shows the rule-level YANG trees of the CFI and NFI YANG
   Trees.  Similarly to the top-level YANG data model, the long-
   connection is not provided in the CFI YANG data model to simplify the
   data model for the user configuration.  This value can also be added
   using a default value in the Security Controller for the low-level
   security policy.





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   In term of similarity, the CFI and NFI YANG data model provides the
   basic rule information such as the unique name the priority value for
   the rules.  Both data models utilize the Event-Condition-Action (ECA)
   policy rule described in Section 3.1 of the
   [I-D.ietf-i2nsf-capability-data-model].

4.2.1.  The CFI and NFI Event YANG Data Models Comparison

     Consumer-Facing Interface (CFI):
     |  +--rw event
     |  |  +--rw system-event*   identityref
     |  |  +--rw system-alarm*   identityref

     NSF-Facing Interface (NFI):
     |  +--rw event
     |  |  +--rw description?     string
     |  |  +--rw system-event*   identityref
     |  |  +--rw system-alarm*   identityref

                 Figure 3: The CFI and NFI Event YANG Trees

   As shown in Figure 3, CFI and NFI YANG data models have the almost
   same structures for Event except for description in NFI.  The
   description is optional because it contains human-readable text for
   the description of an event.

4.2.2.  The CFI and NFI Condition YANG Data Models Comparison

   Consumer-Facing Interface (CFI):
   |  +--rw condition
   |  |  +--rw firewall
   |  |  |  +--rw source*                     union
   |  |  |  +--rw destination*                union
   |  |  |  +--rw transport-layer-protocol?   identityref
   |  |  |  +--rw range-port-number
   |  |  |  |  +--rw start-port-number?   inet:port-number
   |  |  |  |  +--rw end-port-number?     inet:port-number
   |  |  |  +--rw icmp
   |  |  |     +--rw message*   identityref
   |  |  +--rw ddos
   |  |  |  +--rw rate-limit
   |  |  |     +--rw packet-rate-threshold?   uint64
   |  |  |     +--rw byte-rate-threshold?     uint64
   |  |  |     +--rw flow-rate-threshold?     uint64
   |  |  +--rw anti-virus
   |  |  |  +--rw exception-files*   string
   |  |  +--rw payload
   |  |  |  +--rw content*



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             -> /i2nsf-cfi-policy/threat-prevention/payload-content/name
   |  |  +--rw url-category
   |  |  |  +--rw url-name?
                     -> /i2nsf-cfi-policy/endpoint-groups/url-group/name
   |  |  +--rw voice
   |  |  |  +--rw source-id*        string
   |  |  |  +--rw destination-id*   string
   |  |  |  +--rw user-agent*       string
   |  |  +--rw context
   |  |  |  +--rw time
   |  |  |  |  +--rw start-date-time?   yang:date-and-time
   |  |  |  |  +--rw end-date-time?     yang:date-and-time
   |  |  |  |  +--rw period
   |  |  |  |  |  +--rw start-time?   time
   |  |  |  |  |  +--rw end-time?     time
   |  |  |  |  |  +--rw day*          day
   |  |  |  |  |  +--rw date*         int32
   |  |  |  |  |  +--rw month*        string
   |  |  |  |  +--rw frequency?         enumeration
   |  |  |  +--rw application
   |  |  |  |  +--rw protocol*      identityref
   |  |  |  +--rw device-type
   |  |  |  |  +--rw device*        identityref
   |  |  |  +--rw users
   |  |  |  |  +--rw user* [id]
   |  |  |  |  |  +--rw id      uint32
   |  |  |  |  |  +--rw name?   string
   |  |  |  |  +--rw group* [id]
   |  |  |  |     +--rw id      uint32
   |  |  |  |     +--rw name?   string
   |  |  |  +--rw geographic-location
   |  |  |     +--rw source*
                -> /i2nsf-cfi-policy/endpoint-groups/location-group/name
   |  |  |     +--rw destination*
                -> /i2nsf-cfi-policy/endpoint-groups/location-group/name
   |  |  +--rw threat-feed
   |  |     +--rw name*
           -> /i2nsf-cfi-policy/threat-prevention/threat-feed-list/name

   NSF-Facing Interface:
        |  +--rw condition
        |  |  +--rw description?    string
        |  |  +--rw layer-2* [destination-mac-address source-mac-address
                              ethertype]
        |  |  |  +--rw description?                    string
        |  |  |  +--rw destination-mac-address         yang:mac-address
        |  |  |  +--rw destination-mac-address-mask?   yang:mac-address
        |  |  |  +--rw source-mac-address              yang:mac-address



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        |  |  |  +--rw source-mac-address-mask?        yang:mac-address
        |  |  |  +--rw ethertype                       eth:ethertype
        |  |  +--rw (layer-3)?
        |  |  |  +--:(ipv4)
        |  |  |  |  +--rw ipv4
        |  |  |  |     +--rw description?                      string
        |  |  |  |     +--rw dscp?                             inet:dscp
        |  |  |  |     +--rw ecn?                              uint8
        |  |  |  |     +--rw length?                           uint16
        |  |  |  |     +--rw ttl?                              uint8
        |  |  |  |     +--rw protocol?                         uint8
        |  |  |  |     +--rw ihl?                              uint8
        |  |  |  |     +--rw flags?                            bits
        |  |  |  |     +--rw offset?                           uint16
        |  |  |  |     +--rw identification?                   uint16
        |  |  |  |     +--rw (destination-network)?
        |  |  |  |     |  +--:(destination-ipv4-network)
        |  |  |  |     |  |  +--rw destination-ipv4-network?
                                                        inet:ipv4-prefix
        |  |  |  |     |  +--:(destination-ipv4-range)
        |  |  |  |     |     +--rw destination-ipv4-range* [start end]
        |  |  |  |     |        +--rw start    inet:ipv4-address-no-zone
        |  |  |  |     |        +--rw end      inet:ipv4-address-no-zone
        |  |  |  |     +--rw (source-network)?
        |  |  |  |        +--:(source-ipv4-network)
        |  |  |  |        |  +--rw source-ipv4-network? inet:ipv4-prefix
        |  |  |  |        +--:(source-ipv4-range)
        |  |  |  |           +--rw source-ipv4-range* [start end]
        |  |  |  |              +--rw start    inet:ipv4-address-no-zone
        |  |  |  |              +--rw end      inet:ipv4-address-no-zone
        |  |  |  +--:(ipv6)
        |  |  |     +--rw ipv6
        |  |  |        +--rw description?                      string
        |  |  |        +--rw dscp?                             inet:dscp
        |  |  |        +--rw ecn?                              uint8
        |  |  |        +--rw length?                           uint16
        |  |  |        +--rw ttl?                              uint8
        |  |  |        +--rw protocol?                         uint8
        |  |  |        +--rw (destination-network)?
        |  |  |        |  +--:(destination-ipv6-network)
        |  |  |        |  |  +--rw destination-ipv6-network?
                                                        inet:ipv6-prefix
        |  |  |        |  +--:(destination-ipv6-range)
        |  |  |        |     +--rw destination-ipv6-range* [start end]
        |  |  |        |        +--rw start    inet:ipv6-address-no-zone
        |  |  |        |        +--rw end      inet:ipv6-address-no-zone
        |  |  |        +--rw (source-network)?
        |  |  |        |  +--:(source-ipv6-network)



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        |  |  |        |  |  +--rw source-ipv6-network? inet:ipv6-prefix
        |  |  |        |  +--:(source-ipv6-range)
        |  |  |        |     +--rw source-ipv6-range* [start end]
        |  |  |        |        +--rw start    inet:ipv6-address-no-zone
        |  |  |        |        +--rw end      inet:ipv6-address-no-zone
        |  |  |        +--rw flow-label?      inet:ipv6-flow-label
        |  |  +--rw (layer-4)?
        |  |  |  +--:(tcp)
        |  |  |  |  +--rw tcp
        |  |  |  |     +--rw description?               string
        |  |  |  |     +--rw source-port-number
        |  |  |  |     |  +--rw (source-port)?
        |  |  |  |     |     +--:(range-or-operator)
        |  |  |  |     |     |  +--rw (port-range-or-operator)?
        |  |  |  |     |     |     +--:(range)
        |  |  |  |     |     |     |  +--rw lower-port  inet:port-number
        |  |  |  |     |     |     |  +--rw upper-port  inet:port-number
        |  |  |  |     |     |     +--:(operator)
        |  |  |  |     |     |        +--rw operator?     operator
        |  |  |  |     |     |        +--rw port        inet:port-number
        |  |  |  |     |     +--:(port-list)
        |  |  |  |     |        +--rw port-numbers* [start end]
        |  |  |  |     |           +--rw start    inet:port-number
        |  |  |  |     |           +--rw end      inet:port-number
        |  |  |  |     +--rw destination-port-number
        |  |  |  |     |  +--rw (destination-port)?
        |  |  |  |     |     +--:(range-or-operator)
        |  |  |  |     |     |  +--rw (port-range-or-operator)?
        |  |  |  |     |     |     +--:(range)
        |  |  |  |     |     |     |  +--rw lower-port  inet:port-number
        |  |  |  |     |     |     |  +--rw upper-port  inet:port-number
        |  |  |  |     |     |     +--:(operator)
        |  |  |  |     |     |        +--rw operator?     operator
        |  |  |  |     |     |        +--rw port        inet:port-number
        |  |  |  |     |     +--:(port-list)
        |  |  |  |     |        +--rw port-numbers* [start end]
        |  |  |  |     |           +--rw start    inet:port-number
        |  |  |  |     |           +--rw end      inet:port-number
        |  |  |  |     +--rw sequence-number?           uint32
        |  |  |  |     +--rw acknowledgement-number?    uint32
        |  |  |  |     +--rw data-offset?               uint8
        |  |  |  |     +--rw reserved?                  uint8
        |  |  |  |     +--rw flags?                     bits
        |  |  |  |     +--rw window-size?               uint16
        |  |  |  |     +--rw urgent-pointer?            uint16
        |  |  |  |     +--rw options?                   binary
        |  |  |  +--:(udp)
        |  |  |  |  +--rw udp



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        |  |  |  |     +--rw description?               string
        |  |  |  |     +--rw source-port-number
        |  |  |  |     |  +--rw (source-port)?
        |  |  |  |     |     +--:(range-or-operator)
        |  |  |  |     |     |  +--rw (port-range-or-operator)?
        |  |  |  |     |     |     +--:(range)
        |  |  |  |     |     |     |  +--rw lower-port  inet:port-number
        |  |  |  |     |     |     |  +--rw upper-port  inet:port-number
        |  |  |  |     |     |     +--:(operator)
        |  |  |  |     |     |        +--rw operator?     operator
        |  |  |  |     |     |        +--rw port        inet:port-number
        |  |  |  |     |     +--:(port-list)
        |  |  |  |     |        +--rw port-numbers* [start end]
        |  |  |  |     |           +--rw start    inet:port-number
        |  |  |  |     |           +--rw end      inet:port-number
        |  |  |  |     +--rw destination-port-number
        |  |  |  |     |  +--rw (destination-port)?
        |  |  |  |     |     +--:(range-or-operator)
        |  |  |  |     |     |  +--rw (port-range-or-operator)?
        |  |  |  |     |     |     +--:(range)
        |  |  |  |     |     |     |  +--rw lower-port  inet:port-number
        |  |  |  |     |     |     |  +--rw upper-port  inet:port-number
        |  |  |  |     |     |     +--:(operator)
        |  |  |  |     |     |        +--rw operator?     operator
        |  |  |  |     |     |        +--rw port        inet:port-number
        |  |  |  |     |     +--:(port-list)
        |  |  |  |     |        +--rw port-numbers* [start end]
        |  |  |  |     |           +--rw start    inet:port-number
        |  |  |  |     |           +--rw end      inet:port-number
        |  |  |  |     +--rw length?                    uint16
        |  |  |  +--:(sctp)
        |  |  |  |  +--rw sctp
        |  |  |  |     +--rw description?               string
        |  |  |  |     +--rw source-port-number
        |  |  |  |     |  +--rw (source-port)?
        |  |  |  |     |     +--:(range-or-operator)
        |  |  |  |     |     |  +--rw (port-range-or-operator)?
        |  |  |  |     |     |     +--:(range)
        |  |  |  |     |     |     |  +--rw lower-port  inet:port-number
        |  |  |  |     |     |     |  +--rw upper-port  inet:port-number
        |  |  |  |     |     |     +--:(operator)
        |  |  |  |     |     |        +--rw operator?     operator
        |  |  |  |     |     |        +--rw port        inet:port-number
        |  |  |  |     |     +--:(port-list)
        |  |  |  |     |        +--rw port-numbers* [start end]
        |  |  |  |     |           +--rw start    inet:port-number
        |  |  |  |     |           +--rw end      inet:port-number
        |  |  |  |     +--rw destination-port-number



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        |  |  |  |     |  +--rw (destination-port)?
        |  |  |  |     |     +--:(range-or-operator)
        |  |  |  |     |     |  +--rw (port-range-or-operator)?
        |  |  |  |     |     |     +--:(range)
        |  |  |  |     |     |     |  +--rw lower-port  inet:port-number
        |  |  |  |     |     |     |  +--rw upper-port  inet:port-number
        |  |  |  |     |     |     +--:(operator)
        |  |  |  |     |     |        +--rw operator?     operator
        |  |  |  |     |     |        +--rw port        inet:port-number
        |  |  |  |     |     +--:(port-list)
        |  |  |  |     |        +--rw port-numbers* [start end]
        |  |  |  |     |           +--rw start    inet:port-number
        |  |  |  |     |           +--rw end      inet:port-number
        |  |  |  |     +--rw chunk-type*                uint8
        |  |  |  |     +--rw chunk-length?              uint16
        |  |  |  +--:(dccp)
        |  |  |  |  +--rw dccp
        |  |  |  |     +--rw description?               string
        |  |  |  |     +--rw source-port-number
        |  |  |  |     |  +--rw (source-port)?
        |  |  |  |     |     +--:(range-or-operator)
        |  |  |  |     |     |  +--rw (port-range-or-operator)?
        |  |  |  |     |     |     +--:(range)
        |  |  |  |     |     |     |  +--rw lower-port  inet:port-number
        |  |  |  |     |     |     |  +--rw upper-port  inet:port-number
        |  |  |  |     |     |     +--:(operator)
        |  |  |  |     |     |        +--rw operator?     operator
        |  |  |  |     |     |        +--rw port        inet:port-number
        |  |  |  |     |     +--:(port-list)
        |  |  |  |     |        +--rw port-numbers* [start end]
        |  |  |  |     |           +--rw start    inet:port-number
        |  |  |  |     |           +--rw end      inet:port-number
        |  |  |  |     +--rw destination-port-number
        |  |  |  |     |  +--rw (destination-port)?
        |  |  |  |     |     +--:(range-or-operator)
        |  |  |  |     |     |  +--rw (port-range-or-operator)?
        |  |  |  |     |     |     +--:(range)
        |  |  |  |     |     |     |  +--rw lower-port  inet:port-number
        |  |  |  |     |     |     |  +--rw upper-port  inet:port-number
        |  |  |  |     |     |     +--:(operator)
        |  |  |  |     |     |        +--rw operator?     operator
        |  |  |  |     |     |        +--rw port        inet:port-number
        |  |  |  |     |     +--:(port-list)
        |  |  |  |     |        +--rw port-numbers* [start end]
        |  |  |  |     |           +--rw start    inet:port-number
        |  |  |  |     |           +--rw end      inet:port-number
        |  |  |  |     +--rw service-code*              uint32
        |  |  |  |     +--rw type*                      uint8



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        |  |  |  |     +--rw data-offset?               uint8
        |  |  |  +--:(icmp)
        |  |  |     +--rw icmp
        |  |  |        +--rw description?      string
        |  |  |        +--rw version?          enumeration
        |  |  |        +--rw type?             uint8
        |  |  |        +--rw code?             uint8
        |  |  |        +--rw rest-of-header?   binary
        |  |  +--rw url-category
        |  |  |  +--rw description?    string
        |  |  |  +--rw pre-defined*    string
        |  |  |  +--rw user-defined*   string
        |  |  +--rw voice
        |  |  |  +--rw description?            string
        |  |  |  +--rw source-voice-id*        string
        |  |  |  +--rw destination-voice-id*   string
        |  |  |  +--rw user-agent*             string
        |  |  +--rw ddos
        |  |  |  +--rw description?         string
        |  |  |  +--rw alert-packet-rate?   uint32
        |  |  |  +--rw alert-flow-rate?     uint32
        |  |  |  +--rw alert-byte-rate?     uint32
        |  |  +--rw anti-virus
        |  |  |  +--rw profile*           string
        |  |  |  +--rw exception-files*   string
        |  |  +--rw payload
        |  |  |  +--rw description?   string
        |  |  |  +--rw content*       binary
        |  |  +--rw context
        |  |     +--rw description?           string
        |  |     +--rw time
        |  |     |  +--rw start-date-time?   yang:date-and-time
        |  |     |  +--rw end-date-time?     yang:date-and-time
        |  |     |  +--rw period
        |  |     |  |  +--rw start-time?   time
        |  |     |  |  +--rw end-time?     time
        |  |     |  |  +--rw day*          day
        |  |     |  |  +--rw date*         int8
        |  |     |  |  +--rw month*        string
        |  |     |  +--rw frequency?         enumeration
        |  |     +--rw application
        |  |     |  +--rw description?   string
        |  |     |  +--rw protocol*      identityref
        |  |     +--rw device-type
        |  |     |  +--rw description?   string
        |  |     |  +--rw device*        identityref
        |  |     +--rw users
        |  |     |  +--rw description?   string



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        |  |     |  +--rw user* [id]
        |  |     |  |  +--rw id      uint32
        |  |     |  |  +--rw name?   string
        |  |     |  +--rw group* [id]
        |  |     |     +--rw id      uint32
        |  |     |     +--rw name?   string
        |  |     +--rw geographic-location
        |  |        +--rw description?   string
        |  |        +--rw source*        string
        |  |        +--rw destination*   string

               Figure 4: The CFI and NFI Condition YANG Trees

   Figure 4 shows CFI and NFI Condition YANG Trees.  It shows a
   different way to manipulate the Access Control Lists (ACLs) for the
   CFI and NFI YANG data models.  The CFI aims at an easy security
   policy configuration, thus only provides a simple and most often
   needed fields in ACls, i.e., source and destination address (IPv4 or
   IPv6), type of transport protocol, source and destination port
   numbers, type of application protocol, and ICMP type and code.
   While, the NFI imports from [RFC8519] to provide a detailed
   configuration of packet header.

   Additionally, both data models provide configuration for advanced
   network security functions such as DDoS, Antivirus, Payload (DPI),
   URL Filtering, and Voice Filtering conditions.  The difference is
   that in CFI some of the information (name, value) for configuration
   is saved into a database in Security Controller for easy
   configuration.  The configuration can be done by using the key name
   that holds the corresponding value.

   The YANG data models also has context condition that can be one to
   one mapped, such as time condition to define the active period of a
   rule or geographic location condition to filter traffic from/to a
   certain region that can be mapped into the source and destination IP
   (IPv4 or IPv6) addresses based on the database provided.

4.2.3.  The CFI and NFI Action YANG Data Models Comparison













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     Consumer-Facing Interface (CFI):
      +--rw actions
          |  +--rw primary-action
          |  |  +--rw action?   identityref
          |  +--rw secondary-action
          |     +--rw log-action?   identityref

     NSF-Facing Interface (NFI):
      |  +--rw action
      |     +--rw description?       string
      |     +--rw packet-action
      |     |  +--rw ingress-action?   identityref
      |     |  +--rw egress-action?    identityref
      |     |  +--rw log-action?       identityref
      |     +--rw flow-action
      |     |  +--rw ingress-action?   identityref
      |     |  +--rw egress-action?    identityref
      |     |  +--rw log-action?       identityref
      |     +--rw advanced-action
      |        +--rw content-security-control*    identityref
      |        +--rw attack-mitigation-control*   identityref

                Figure 5: The CFI and NFI Action YANG Trees

   Figure 4 shows CFI and NFI Action YANG Trees.  The action in CFI YANG
   data model is separated into primary-action and secondary-action.
   Primary action is the Ingress and Egress action (i.e., pass, drop,
   reject, rate-limit, mirror, invoke-signaling, tunnel-encapsulation,
   forwarding, and transformation) in the NFI YANG data model.  The
   secondary-action is the log-action to log the rule that has been
   triggered by a packet/flow or log the packet/flow that triggered the
   rule.  The NFI also can specify the action as packet or flow action
   depending on the capability of the NSF.

   In NFI YANG data model, the advanced action is used to activate the
   Service Function Chaining (SFC) to apply multiple NSFs on network
   traffics.  This does not exist in CFI as the CFI is used to provide a
   high-level action.  The action of a certain policy in CFI may require
   multiple NSFs (e.g., a URL filtering with firewall) as a single NSF
   may not have the capability to handle the security policy.  Thus, the
   SFC of those NSFs is handled by NFI.










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5.  Design of Security Policy Translator

   Commonly used security policies are created as XML (Extensible Markup
   Language) [XML] files.  A popular way to change the format of an XML
   file is to use an XSLT (Extensible Stylesheet Language
   Transformation) [XSLT] document.  XSLT is an XML-based language to
   transform an input XML file into another output XML file.  However,
   the use of XSLT makes it difficult to manage the security policy
   translator and to handle the registration of new capabilities of
   NSFs.  With the necessity for a security policy translator, this
   document describes a security policy translator based on Automata
   theory.

5.1.  Overall Structure of Security Policy Translator





































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      +--------------------------------------------------+
      |                    I2NSF User                    |
      +------------------------+-------------------------+
                               | Consumer-Facing Interface
                               |
                   High-level Security Policy
                               |
      Security Controller      V
      +------------------------+--------------------------------+
      |  Security Policy       |                                |
      |  Translator            V                                |
      |  +---------------------+----------------------------++  |
      |  |                     |                             |  |
      |  |                     V                             |  |
      |  |             +-------+--------+       +----------+ |  |
      |  |             |   DFA-based    |       |Data Model| |  |
      |  |             | Data Extractor |       |  Mapper  | |  |
      |  |             +-------+--------+       +----------+ |  |
      |  | Extracted Data from |              Mapping |      |  |
      |  |   High-Level Policy V                Model V      |  |
      |  |               +-----+-----+           +--------+  |  |
      |  |               |    Data   |<--------->| NSF DB |  |  |
      |  |               | Converter |           +--------+  |  |
      |  |               +-----+-----+                       |  |
      |  |                     |  Required Data for          |  |
      |  |                     V  Target NSFs                |  |
      |  |            +--------+---------+                   |  |
      |  |            | Policy Generator |                   |  |
      |  |            +--------+---------+                   |  |
      |  |                     |                             |  |
      |  |                     V                             |  |
      |  +---------------------+-----------------------------+  |
      |                        |                                |
      |                        V                                |
      +------------------------+--------------------------------+
                               | NSF-Facing Interface
                               |
                    Low-level Security Policy
                               |
                               V
      +------------------------+-------------------------+
      |                      NSF(s)                      |
      +--------------------------------------------------+

         Figure 6: The Overall Design of Security Policy Translator






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   Figure 6 shows the overall design for Security Policy Translator in
   Security Controller.  There are four main components for Security
   Policy Translator: Data Extractor, Data Converter, Policy Generator,
   and Data Model Mapper.

   Extractor is a DFA-based module for extracting data from a high-level
   policy which I2NSF User delivered via Consumer-Facing Interface.
   Data Model Mapper creates a mapping model for mapping the elements
   between Consumer-Facing Interface and NSF-Facing Interface.  Data
   Converter converts the extracted data to the capabilities of target
   NSFs for a low-level policy.  It refers to an NSF Database (DB) in
   order to convert an abstract subject or object into the corresponding
   concrete subject or object (e.g., IP address and website URL).
   Policy Generator generates a low-level policy which will execute the
   NSF capabilities from Converter.

5.2.  DFA-based Data Extractor

5.2.1.  Design of DFA-based Data Extractor

                             +----------+
                             | accepter |
                             +----------+
                                  | ^
                           <tag 1>| |</tag 1>
                                  v |
        +------------------------------------------------------+
        |                      middle 1                        |
        +------------------------------------------------------+
            | ^                 | ^                      | ^
     <tag 2>| |</tag 2>  <tag 3>| |</tag 3>  ...  <tag n>| |</tag n>
            v |                 v |                      v |

            ...                 ...                      ...

      +-------------+      +-------------+          +-------------+
      | extractor 1 |      | extractor 2 |   ...    | extractor m |
      +-------------+      +-------------+          +-------------+
           data:1               data:2                   data:m

                Figure 7: DFA Architecture of Data Extractor










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   Figure 7 shows a design for Data Extractor in the security policy
   translator.  If a high-level policy contains data along the
   hierarchical structure of the standard Consumer-Facing Interface YANG
   data model [I-D.ietf-i2nsf-consumer-facing-interface-dm], data can be
   easily extracted using the state transition machine, such as DFA.
   The extracted data can be processed and used by an NSF to understand
   it.  Extractor can be constructed by designing a DFA with the same
   hierarchical structure as a YANG data model.

   After constructing a DFA, Data Extractor can extract all of data in
   the entered high-level policy by using state transitions.  Also, the
   DFA can easily detect the grammar errors of the high-level policy.
   The extracting algorithm of Data Extractor is as follows:

   1.  Start from the 'accepter' state.

   2.  Read the next tag from the high-level policy.

   3.  Transit to the corresponding state.

   4.  If the current state is in 'extractor', extract the corresponding
       data, and then go back to step 2.

   5.  If the current state is in 'middle', go back to step 2.

   6.  If there is no possible transition and arrived at 'accepter'
       state, the policy has no grammar error.  Otherwise, there is a
       grammar error, so stop the process with failure.

5.2.2.  Example Scenario for Data Extractor





















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     <i2nsf-cfi-policy
       xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-cfi-policy">
       <name>block_web_security_policy</name>
       <rules>
         <name>block_web</name>
         <condition>
           <firewall-condition>
             <source>Son's_PC</source>
           <firewall-condition>
           <url-condition>
             <url-name>malicious_websites</url-name>
           </url-condition>
         </condition>
         <actions>
           <primary-action>
             <action>drop</action>
           </primary-action>
         </actions>
       </rules>
     </i2nsf-cfi-policy>

                 Figure 8: The Example of High-level Policy





























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                           +----------+
                           | accepter |
                           +----------+
                                | ^
              <i2nsf-cfi-policy>| |</i2nsf-cfi-policy>
                                v |
       +------------------------------------------------------+
       |                      middle 1                        |
       +------------------------------------------------------+
          | ^                               | ^
    <name>| |</name>                        | |
          v |                               | |
    +-------------+                 <rules> | | </rules>
    | extractor 1 |                         | |
    +-------------+                         | |
    block_web_security                      | |
    _policy                                 v |
       +------------------------------------------------------+
       |                  middle 2                            |
       +------------------------------------------------------+
          | ^                   | ^                       | ^
    <name>| |</name> <condition>| | <condition>  <actions>| |</actions>
          v |                   v |                       v |
    +-------------+  +--------------------------+   +-------------+
    | extractor 2 |  |       middle 3           |   |   middle 6  |
    +-------------+  +--------------------------+   +-------------+
       block_web       | ^                  | ^            | ^
                       | |       <url-      | |</url-      | |
                       | |        condition>| | conition>  | |
                       | |                  | |            | |
            <firewall- | |</firewall-       | |   <primary-| |</primary
             condition>| | condition>       | |     action>| | action>
                       v |                  v |            v |
                 +-------------+   +-------------+   +-------------+
                 |   middle 4  |   |   middle 5  |   |   middle 7  |
                 +-------------+   +-------------+   +-------------+
                    | ^                  | ^                | ^
            <source>| |</source>   <url- | |</url-  <action>| |</action>
                    | |             name>| | name>          | |
                    v |                  v |                v |
                 +-------------+   +-------------+    +-------------+
                 | extractor 3 |   | extractor 4 |    | extractor 5 |
                 +-------------+   +-------------+    +-------------+
                    Son's_PC      malicious_websites        drop


                  Figure 9: The Example of Data Extractor




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   To explain the Data Extractor process by referring to an example
   scenario, assume that Security Controller received a high-level
   policy for a web-filtering as shown in Figure 8.  Then we can
   construct DFA-based Data Extractor by using the design as shown in
   Figure 7.  Figure 9 shows the architecture of Data Extractor that is
   based on the architecture in Figure 7 along with the input high-level
   policy in Figure 8.  Data Extractor can automatically extract all of
   data in the high-level policy according to the following process:

   1.   Start from the 'accepter' state.

   2.   Read the first opening tag called '<i2nsf-cfi-policy>', and
        transit to the 'middle 1' state.

   3.   Read the second opening tag called '<name>', and transit to the
        'extractor 1' state.

   4.   The current state is an 'extractor' state.  Extract the data of
        'name' field called 'block_web_security_policy'.

   5.   Read the second closing tag called '</name>', and go back to the
        'middle 1' state.

   6.   Read the third opening tag called '<rules>', and transit to the
        'middle 2' state.

   7.   Read the fourth opening tag called '<name>', and transit to the
        'extractor 2' state.

   8.   The current state is an 'extractor' state.  Extract the data of
        'name' field called 'block_web'.

   9.   Read the fourth closing tag called '</name>', and go back to the
        'middle 2' state.

   10.  Read the fifth opening tag called '<condition>', and transit to
        the 'middle 3' state.

   11.  Read the sixth opening tag called '<firewall-condition>', and
        transit to the 'middle 4' state.

   12.  Read the seventh opening tag called '<source>', and transit to
        the 'extractor 3' state.

   13.  The current state is an 'extractor' state.  Extract the data of
        'source' field called 'Son's_PC'.





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   14.  Read the seventh closing tag called '</source>', and go back to
        the 'middle 4' state.

   15.  Read the sixth closing tag called '</firewall-condition>', and
        go back to the 'middle 3' state.

   16.  Read the eight opening tag called '<url-condition>', and transit
        to the 'middle 5' state.

   17.  Read the ninth opening tag called '<url-name>', and transit to
        the 'extractor 4' state.

   18.  The current state is an 'extractor' state.  Extract the data of
        'url-name' field called 'malicious_websites'.

   19.  Read the ninth closing tag called '</url-name>', and go back to
        the 'middle 5' state.

   20.  Read the eight closing tag called '</url-condition>', and go
        back to the 'middle 3' state.

   21.  Read the fifth closing tag called '</condition>', and go back to
        the 'middle 2' state.

   22.  Read the tenth opening tag called '<actions>', and transit to
        the 'middle 6' state.

   23.  Read the eleventh opening tag called '<primary-action>', and
        transit to the 'middle 7' state.

   24.  Read the twelfth opening tag called '<action>', and transit to
        the 'extractor 5' state.

   25.  The current state is an 'extractor' state.  Extract the data of
        'action' field called 'drop'.

   26.  Read the twelfth closing tag called '</action>', and go back to
        the 'middle 7' state.

   27.  Read the eleventh closing tag called '</primary-action>', and go
        back to the 'middle 6' state.

   28.  Read the tenth closing tag called '</actions>', and go back to
        the 'middle 2' state.

   29.  Read the third closing tag called '</rules>', and go back to the
        'middle 2' state.




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   30.  Read the first closing tag called '</i2nsf-cfi-policy>', and go
        back to the 'accepter' state.

   31.  There is no further possible transition, and the state is
        finally on 'accepter' state.  There is no grammar error in
        Figure 8 so the scanning for data extraction is finished.

   The above process is constructed by an extracting algorithm.  After
   finishing all the steps of the above process, Data Extractor can
   extract all of data in Figure 8, 'block_web_security_policy',
   'block_malicious', 'Son's_PC', 'malicious_websites', and 'drop'.

   Since the translator is modularized into a DFA structure, a visual
   understanding is feasible.  Also, the performance of Data Extractor
   is excellent compared to one-to-one searching of data for a
   particular field.  In addition, the management is efficient because
   the DFA completely follows the hierarchy of Consumer-Facing
   Interface.  If I2NSF User wants to modify the data model of a high-
   level policy, it only needs to change the connection of the relevant
   DFA node.

5.3.  Data Converter

5.3.1.  Role of Data Converter

   Every NSF has its own unique capabilities.  The capabilities of an
   NSF are registered into Security Controller by a Developer's
   Management System, which manages the NSF, via Registration Interface.
   Therefore, Security Controller already has all information about the
   capabilities of NSFs.  This means that Security Controller can find
   target NSFs with only the data (e.g., subject and object for a
   security policy) of the high-level policy by comparing the extracted
   data with all capabilities of each NSF.  This search process for
   appropriate NSFs is called by policy provisioning, and it eliminates
   the need for I2NSF User to specify the target NSFs explicitly in a
   high-level security policy.

   Data Converter selects target NSFs and converts the extracted data
   into the capabilities of selected NSFs.  If Security Controller uses
   this data convertor, it can provide the policy provisioning function
   to I2NSF User automatically.  Thus, the translator design provides
   big benefits to the I2NSF Framework.









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5.3.2.  NSF Database

   The NSF Database contains all the information needed to convert high-
   level policy data to low-level policy data.  The contents of NSF
   Database are classified as the following two: "endpoint information"
   and "NSF capability information".

   The first is "endpoint information".  Endpoint information is
   necessary to convert an abstract high-level policy data such as
   Son's_PC, malicious to a specific low-level policy data such as
   10.0.0.1, illegal.com.  In the high-level policy, the range of
   endpoints for applying security policy MUST be provided abstractly.
   Thus, endpoint information is needed to specify the abstracted high-
   level policy data.  Endpoint information is provided by I2NSF User as
   the high-level policy through Consumer-Facing Interface, and Security
   Controller builds NSF Database based on received information.

   The second is "NSF capability information".  Since capability is
   information that allows NSF to know what features it can support, NSF
   capability information is used in policy provisioning process to
   search the appropriate NSFs through the security policy.  NSF
   capability information is provided by Developer's Management System
   (DMS) through Registration Interface, and Security Controller builds
   NSF Database based on received information.  In addition, if the NSF
   sends monitoring information such as initiating information to
   Security Controller through NSF-Facing Interface, Security Controller
   can modify NSF Database accordingly.
























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     NSF Capability Information                   Endpoint Information
     +-------------------+   has        convert   +------------------+
     |        NSF        +||---+        +-------||+     Endpoint     |
     +-------------------+     |        |         +------------------+
     | *nsf_id   (INT)   |     |        |         | *end_id (INT)    |
     | nsf_name  (STRING)|     |        |         | keyword (STRING) |
     | inbound   (INT)   |     |        |         +------------------+
     | outbound  (INT)   |     |        |
     | bandwidth (INT)   |     |        |
     | activated (BOOL)  |     |        |
     +-------------------+     |        |
               +---------------+        |        +---------------------+
              /|\                       +------||+ Mapping Information |
     +--------------------+   has       |        +---------------------+
     |     Capability     +||---+       |        | *element_id (INT)   |
     +--------------------+     |       |        | element_name(STR)   |
     | *capa_id   (INT)   |     |       |        | element_map (STR)   |
     | capa_name  (STRING)|     |       |        +---------------------+
     | capa_index (INT)   |     |       |
     +--------------------+     |       |
                               /|\     /|\
                        +-----------------------+
                        |         Field         |
                        +-----------------------+
                        | *field_id   (INT)     |
                        | field_name  (STRING)  |
                        | field_index (INT)     |
                        | mapped_data (STRING)  |
                        +-----------------------+

           Figure 10: Entity-Relationship Diagram of NSF Database

   Figure 10 shows an Entity-Relationship Diagram (ERD) of NSF Database
   designed to include both endpoint information received from I2NSF
   User and NSF capability information received from DMS.  By designing
   the NSF database based on the ERD, all the information necessary for
   security policy translation can be stored, and the network system
   administrator can manage the NSF database efficiently.

   ERD was expressed by using Crow's Foot notation.  Crow's Foot
   notation represents a relationship between entities as a line and
   represents the cardinality of the relationship as a symbol at both
   ends of the line.  Attributes prefixed with * are key values of each
   entity.  A link with two vertical lines represents one-to-one
   mapping, and a bird-shaped link represents one-to-many mapping.  An
   NSF entity stores the NSF name (nsf_name), NSF specification
   (inbound, outbound, bandwidth), and NSF activation (activated).  A
   Capability entity stores the capability name (capa_name) and the



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   index of the capability field in a Registration Interface YANG data
   model (capa_index).  An Endpoint entity stores the keyword of
   abstract data conversion from I2NSF User (keyword).  A Field entity
   stores the field name (field_name), the index of the field index in
   an NSF-Facing Interface YANG data model, and converted data by
   referring to the Endpoint entity and a 'convert' relationship.

5.3.3.  Data Conversion in Data Converter

      High-level                           Low-level
      Policy Data                          Policy Data
   +---------------+                    +------------------------------+
   |  Policy Name  |                    |  Policy Name                 |
   | +-----------+ | The same value     |  +-------------------------+ |
   | | block_web |-|------------------->|->|block_web_security_policy| |
   | | _security | |                    |  +-------------------------+ |
   | |  _policy  | |                    |                              |
   | +-----------+ |                    |                              |
   |               |                    |                              |
   |  Rule Name    |                    |  Rule Name                   |
   | +-----------+ | The same value     |  +-------------------------+ |
   | | block_web |-|------------------->|->|        block_web        | |
   | +-----------+ |                    |  +-------------------------+ |
   |               |                    |                              |
   |    Source     | Conversion into    |  Source IPv4 Range           |
   | +-----------+ | User's IP address  |  +-------------------------+ |
   | | Son's_PC  |-|------------------->|->| Start: 10.0.0.1         | |
   | |-----------+ |                    |  | End  : 10.0.0.3         | |
   |               |                    |  +-------------------------+ |
   |               |                    |                              |
   |  URL Name     | Conversion into    |  URL - User Defined          |
   | +-----------+ | malicious websites |  +-------------------------+ |
   | | malicious |-|------------------->|->|       [harm.com,        | |
   | | _websites | |                    |  |       illegal.com]      | |
   | +-----------+ |                    |  +-------------------------+ |
   |               |                    |                              |
   |    Action     | Conversion into    |   Action                     |
   | +-----------+ | NSF Capability     |  +-----------+               |
   | |   drop    |-|------------------->|->|drop/reject|               |
   | +-----------+ |                    |  +-----------+               |
   +---------------+                    +------------------------------+

                   Figure 11: Example of Data Conversion








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   Figure 11 shows an example for describing a data conversion in Data
   Converter.  High-level policy data MUST be converted into low-level
   policy data which are compatible with NSFs.  If a system
   administrator attaches a database to Data Converter, it can convert
   contents by referring to the database with SQL queries.  Data
   conversion in Figure 11 is based on the following list:

   *  'Policy Name' and 'Rule Name' fields do NOT need the conversion.

   *  'Source' field SHOULD be converted into a range (start and end) of
      IPv4 addresses.

   *  'URL Name' field SHOULD be converted into a URL list of malicious
      websites.

   *  'Action' field SHOULD be converted into the corresponding
      action(s) in NSF capabilities.

5.3.4.  Data Model Mapper

   When translating a policy, the mapping between each element of the
   data models are necessary to properly convert the data.  The Data
   Model Mapper create a mapping model between the elements in Consumer-
   Facing Interface YANG data model and NSF-Facing Interface YANG data
   model.  Each element in the Consumer-Facing Interface Policy Data
   Model has at least one or more corresponding element in NSF-Facing
   Interface Data Model.
























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       Consumer-Facing Interface          NSF-Facing Interface
            YANG data model                  YANG data model
                   |                               |
                   V                               V
         +---------+-------------------------------+------+
         |         |       Data Model Mapper       |      |
         |         |                               |      |
         |         |  +-------------------------+  |      |
         |         +->| Convert as a Tree Graph |<-+      |
         |            +------------+------------+         |
         |                         |                      |
         |                         v                      |
         |          +----------------------------+        |
         |          | Calculate each element     |        |
         |          | Tree Edit Distance         |        |
         |          | between the CFI and NFI    |        |
         |          +--------------+-------------+        |
         |                         |                      |
         |                         v                      |
         |            +-------------------------+         |
         |            |  Get the elements with  |         |
         |            |  smallest distance as   |         |
         |            |  the candidates         |         |
         |            +-------------------------+         |
         |                         |                      |
         +-------------------------+----------------------+
                                   |
                                   V
                     Data Model Mapping Information

   Note
   CFI: Consumer-Facing Interface
   NFI: NSF-Facing Interface


                       Figure 12: Data Model Mapping

   Figure 12 shows the automatic mapping method for I2NSF Security
   Policy Translator.  The automatic mapping is helpful as the CFI and
   NFI YANG data models can be extended.  The automatic mapper uses the
   CFI and NFI YANG data models as inputs.  The process the Data Model
   and converts it into a Tree Graph.  Tree Graph is used to proces the
   Data Model as a Tree instead of individual elements.  Then the Data
   Model Mapper calculates the Tree Edit Distance between each element
   in Consumer-Facing Interface and each element in NSF-Facing
   Interface.  The Tree Edit Distance can be calculated with an
   algorithm, e.g., Zhang-Shasha algorithm [Zhang-Shasha], with the
   calculation should start from the root of the tree.



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   The Zhang-Shasha calculates the distance by three operations:

   *  Insert: Inserting a node or element

   *  Delete: Deleting a node or element

   *  Change: Change the label of a node or element to another

   The insert and delete operations are a simple of adding/deleting a
   node or element with the length of the label of the node.  The change
   operation must be calculated between the label of the element to
   produce the distance.  There are methods to calculate this, such as
   Levenshtein Distance, Cosine Similarity, or Sequence Matching.  For
   this data model mapper, cosine similarity should be the best choice
   as it measures the similarity between words.  The data models have
   similarity between words and it can helps in calculating as minimum
   distance as possible.

   When the minimum distance is obtained, the NSF-Facing Interface
   element is saved as the candidates for mapping the Consumer-Facing
   Interface element.  This information should be saved to the NSF
   Database for the Data Converter.

   Do note that the proper mapping can be achieved because the
   similarity between the Consumer-Facing Interface and NSF-Facing
   Interface.  An extension created for the Consumer-Facing Interface
   and NSF-Facing Interface should keep the close similarity
   relationship between the data models to be able to produce the
   mapping model information automatically.

   The proper mapping between CFI YANG data model and NFI YANG data
   model provided in [I-D.ietf-i2nsf-consumer-facing-interface-dm] and
   [I-D.ietf-i2nsf-nsf-facing-interface-dm], respectively, can be seen
   in Appendix A.

5.3.4.1.  Handling of Default Values for a Low-level Security Policy

   Attributes in NFI YANG data model provide detailed configuration for
   NSFs to handle thorough examination for security services in a
   network.  Some of the attributes in the NFI YANG data model can be
   given directly after the mapping translation from a high-level
   policy.  But the CFI YANG data model is designed to be used easily by
   an I2NSF User, hence some attributes cannot be mapped directly to the
   attributes in the NFI YANG data model.

   To accommodate such attributes that cannot be given by the direct
   translation from the CFI YANG data model, default values can be used.
   For example, the attribute "default-action" in the NFI YANG data



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   model cannot be configured by the CFI YANG data model.  A firewall
   usually drops packets by default to make sure that only permitted
   packets are allowed to pass through to the network.  So, the default
   value for the attribute "default-action" will be a "drop" action.
   This can be done in the implementation of the translation so that the
   attribute can be given a default value.

   The default value for different NSFs can be different depending on
   the type of service it offers.  A typical firewall may use the
   default-value "drop" for the "default-action" attribute, but an
   antivirus may use a default-value "pass" for "default-action" to make
   sure that only the detected viruses are blocked.  Other types of
   firewalls may also use different default values for the "default-
   action".  Thus, the actual default values that are given to the NSFs
   are out of the scope of this document.

5.3.5.  Policy Provisioning


































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         Log-keeper              Low-level              Web-filter
            NSF                 Policy Data                NSF
   +-------------------+  +--------------------+  +-------------------+
   |    Policy Name    |  |     Policy Name    |  |     Policy Name   |
   | +--------------+  |  |  +--------------+  |  |  +--------------+ |
   | | block_web    |<-|<-|<-| block_web    |->|->|->| block_web    | |
   | | _security    |  |  |  | _security    |  |  |  | _security    | |
   | | _policy      |  |  |  | _policy      |  |  |  | _policy      | |
   | +--------------+  |  |  +--------------+  |  |  +--------------+ |
   |                   |  |                    |  |                   |
   |    Rule Name      |  |     Rule Name      |  |     Rule Name     |
   | +--------------+  |  |  +--------------+  |  |  +--------------+ |
   | |  block_web   |<-|<-|<-|   block_web  |->|->|->|   block_web  | |
   | +--------------+  |  |  +--------------+  |  |  +--------------+ |
   |                   |  |                    |  |                   |
   |   Source IPv4     |  |    Source IPv4     |  |    Source IPv4    |
   | +--------------+  |  |  +--------------+  |  |  +--------------+ |
   | |Start:10.0.0.1|<-|<-|<-|Start:10.0.0.1|->|->|->|Start:10.0.0.1| |
   | |End  :10.0.0.3|  |  |  |End  :10.0.0.3|  |  |  |End  :10.0.0.3| |
   | +--------------+  |  |  +--------------+  |  |  +--------------+ |
   |                   |  |                    |  |                   |
   |                   |  | URL - User Defined |  | URL - User Defined|
   |                   |  |  +--------------+  |  |  +--------------+ |
   |                   |  |  |  [harm.com,  |->|->|->|  [harm.com,  | |
   |                   |  |  | illegal.com] |  |  |  | illegal.com] | |
   |                   |  |  +--------------+  |  |  +--------------+ |
   |                   |  |                    |  |                   |
   |    Log Action     |  |     Log Action     |  |                   |
   | +--------------+  |  |  +--------------+  |  |                   |
   | |     True     |<-|<-|<-|     True     |  |  |                   |
   | +--------------+  |  |  +--------------+  |  |                   |
   +-------------------+  |                    |  |                   |
                          |       Action       |  |       Action      |
                          |  +--------------+  |  |  +--------------+ |
                          |  |     Drop     |->|->|->|  Drop/Reject | |
                          |  +--------------+  |  |  +--------------+ |
                          +--------------------+  +-------------------+

                 Figure 13: Example of Policy Provisioning

   Generator searches for proper NSFs which can cover all of
   capabilities in the high-level policy.  Generator searches for target
   NSFs by comparing only NSF capabilities which is registered by Vendor
   Management System.  This process is called by "policy provisioning"
   because Generator finds proper NSFs by using only the policy.  If
   target NSFs are found by using other data which is not included in a
   user's policy, it means that the user already knows the specific
   knowledge of an NSF in the I2NSF Framework.  Figure 13 shows an



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   example of policy provisioning.  In this example, log-keeper NSF and
   web-filter NSF are selected for covering capabilities in the security
   policy.  All of capabilities can be covered by two selected NSFs.

5.4.  Policy Generator

   Generator makes low-level security policies for each target NSF with
   the extracted data.  The low-level security policy can be produced in
   the form of XML or JSON.  Libray such as PyangBind [PyangBind] for
   Python can be used to parse the NFI YANG data model to produce an XML
   or JSON form automatically.

      +----------------------------------------------------------+
      |                    Policy Generator                      |
      |                                                          |
      |  +------------+      +-----------+    +-------------+    |
      |  | Low-level  | Pair | Low-Level |    |  NFI YANG   |    |
      |  | Attributes |<---->| Data      |    |  Data Model |    |
      |  +-----+------+      +-----+-----+    +-------+-----+    |
      |        |                   |                  |          |
      |        |                   |                  |          |
      |        +---------+---------+                  |          |
      |                  |                            |          |
      |                  |                            |          |
      |                  v                            v          |
      |          +---------------+             +------------+    |
      |          |   NFI Python  |<------------| PyangBind  |    |
      |          |     Class     |             +------------+    |
      |          +-------+-------+                               |
      |                  |                                       |
      |                  |                                       |
      |                  v                                       |
      |          +---------------+                               |
      |          |   Low-level   |                               |
      |          |    Policy     |                               |
      |          | (XML or JSON) |                               |
      |          +---------------+                               |
      |                                                          |
      +----------------------------------------------------------+

                  Figure 14: Policy Generator Architecture










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   Figure 14 shows the architecture of the Policy Generator.  First,
   PyangBind library generates a Python class hierarchy from an input of
   the NFI YANG data model.  This allows low-level data instances from
   the Data Converter (Section 5.3) to be inserted into the NFI Python
   Class.  To get the appropriate attributes, the low-level data is
   paired with the attributes received from the Data Model Mapper
   (Section 5.3.4).  The filled entry can then be encoded into an XML or
   JSON form automatically by PyangBind.

   Figure 15 shows an XML example of a low-level policy generated by the
   translator.

         <i2nsf-security-policy>
           <name>block_web_security_policy</name>
           <rules>
             <name>block_web</name>
             <condition>
               <ipv4>
                 <source-ipv4-range>
                   <start>10.0.0.1</start>
                   <end>10.0.0.3</end>
                 </source-ipv4-range>
               </ipv4>
               <url-category>
                 <user-defined>harm.com</user-defined>
                 <user-defined>illegal.com</user-defined>
               </url-category>
             </condition>
             <action>
               <packet-action>drop</packet-action>
             </action>
           </rules>
         </i2nsf-security-policy>

                   Figure 15: Example of Low-Level Policy

6.  Implementation Considerations

   The implementation considerations in this document include the
   following three: "data model auto-adaptation", "data conversion", and
   "policy provisioning".










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6.1.  Data Model Auto-adaptation

   Security Controller which acts as an intermediary entity MUST process
   the data according to the data model of the connected interfaces.
   However, the data model can be changed flexibly depending on the
   situation, and Security Controller may adapt to the change of the
   data model.  Therefore, Security Controller can be implemented for
   convenience so that the security policy translator can easily adapt
   to the change of the data model.

   The translator constructs and uses the DFA to adapt to the Consumer-
   Facing Interface Data Model.  The DFA starts from the root node of
   the YANG tree and expands operations by changing the state according
   to the input.  Based on the YANG data model, a container node is
   defined as a middle state and a leaf node is defined as an extractor
   node.  After that, if the nodes are connected in the same way as the
   hierarchical structure of the data model, Security Controller can
   automatically construct the DFA.  Therefore, the DFA can be
   conveniently built by investigating the link structure using the
   stack through a Depth-First Search, starting from the root node.

   The Policy Generator uses PyangBind to construct the hierarchy of the
   NFI YANG data model into a Python class.  This allows an XML or JSON
   form to be generated automatically even with updates of the NFI YANG
   data model.  Thus, the security policy translator is able to auto-
   adapt to the NFI YANG data model.

6.2.  Data Conversion

   Security Controller requires the ability to materialize the abstract
   data in the high-level security policy and forward it to NSFs.
   Security Controller can receive endpoint information as keywords
   through the high-level security policy.  At this time, if the
   endpoint information corresponding to the keyword is mapped and the
   query is transmitted to the NSF Database, the NSF Database can be
   conveniently registered with necessary information for data
   conversion.  When a policy tries to establish a policy through the
   keyword, Security Controller searches for the details corresponding
   to the keyword registered in the NSF Database and converts the
   keyword into appropriate and specific data.











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6.3.  Policy Provisioning

   This document states that a policy provisioning function is necessary
   to enable an I2NSF User without expert security knowledge to create
   policies.  Policy provisioning is determined by the capability of the
   NSF.  If the information about an NSF's capability for a policy is
   available to Security Controller, the probability of the selection of
   an appropriate NSF may increase.

   Most importantly, selected NSFs may be able to perform all
   capabilities in the security policy.  This document recommends the
   study of policy provisioning algorithms that are highly efficient and
   can satisfy all capabilities in the security policy.

7.  Features of Security Policy Translator Design

   First, by showing a visualized translator structure, the security
   manager can handle various policy changes.  Translator can be shown
   by visualizing DFA so that the manager can easily understand the
   structure of Security Policy Translator.

   Second, if it only keeps the hierarchy of the data model, an I2NSF
   User can freely create high-level policies.  In the case of DFA, data
   extraction can be performed in the same way even if the order of
   input is changed.  The design of the security policy translator is
   more flexible than the existing method that works by keeping the
   tag's position and order exactly.

   Third, the structure of Security Policy Translator can be updated
   even while Security Policy Translator is operating.  Because Security
   Policy Translator is modularized, the translator can adapt to changes
   in an NSF's capabilities while the I2NSF framework is running.  The
   function of changing the translator's structure can be provided
   through the Registration Interface
   [I-D.ietf-i2nsf-registration-interface-dm].

8.  Security Considerations

   There is no security concern in the proposed security policy
   translator as long as the I2NSF interfaces (i.e., Consumer-Facing
   Interface, NSF-Facing Interface, and Registration Interface) are
   protected by secure communication channels.

9.  IANA Considerations

   This document does not require any IANA actions.

10.  References



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10.1.  Normative References

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [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>.

   [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>.

   [RFC8329]  Lopez, D., Lopez, E., Dunbar, L., Strassner, J., and R.
              Kumar, "Framework for Interface to Network Security
              Functions", RFC 8329, DOI 10.17487/RFC8329, February 2018,
              <https://www.rfc-editor.org/info/rfc8329>.

   [I-D.ietf-i2nsf-consumer-facing-interface-dm]
              Jeong, J. (., Chung, C., Ahn, T., Kumar, R., and S. Hares,
              "I2NSF Consumer-Facing Interface YANG Data Model", Work in
              Progress, Internet-Draft, draft-ietf-i2nsf-consumer-
              facing-interface-dm-18, 13 April 2022,
              <https://www.ietf.org/archive/id/draft-ietf-i2nsf-
              consumer-facing-interface-dm-18.txt>.

   [I-D.ietf-i2nsf-nsf-facing-interface-dm]
              Kim, J. (., Jeong, J. (., Park, J., Hares, S., and Q. Lin,
              "I2NSF Network Security Function-Facing Interface YANG
              Data Model", Work in Progress, Internet-Draft, draft-ietf-
              i2nsf-nsf-facing-interface-dm-26, 19 April 2022,
              <https://www.ietf.org/archive/id/draft-ietf-i2nsf-nsf-
              facing-interface-dm-26.txt>.

   [I-D.ietf-i2nsf-registration-interface-dm]
              Hyun, S., Jeong, J. (., Roh, T., Wi, S., and J. Park,
              "I2NSF Registration Interface YANG Data Model", Work in
              Progress, Internet-Draft, draft-ietf-i2nsf-registration-
              interface-dm-16, 13 April 2022,
              <https://www.ietf.org/archive/id/draft-ietf-i2nsf-
              registration-interface-dm-16.txt>.

   [I-D.ietf-i2nsf-capability-data-model]
              Hares, S., Jeong, J. (., Kim, J. (., Moskowitz, R., and Q.
              Lin, "I2NSF Capability YANG Data Model", Work in Progress,



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              Internet-Draft, draft-ietf-i2nsf-capability-data-model-30,
              13 April 2022, <https://www.ietf.org/archive/id/draft-
              ietf-i2nsf-capability-data-model-30.txt>.

10.2.  Informative References

   [RFC8519]  Jethanandani, M., Agarwal, S., Huang, L., and D. Blair,
              "YANG Data Model for Network Access Control Lists (ACLs)",
              RFC 8519, DOI 10.17487/RFC8519, March 2019,
              <https://www.rfc-editor.org/info/rfc8519>.

   [Automata] Peter, L., "Formal Languages and Automata, 6th Edition",
              January 2016.

   [Zhang-Shasha]
              Zhang, K. and D. Shasha, "Simple Fast Algorithms for the
              Editing Distance Between Trees and Related Problems", SIAM
              J. Comput. https://www.researchgate.net/publication/220618
              233_Simple_Fast_Algorithms_for_the_Editing_Distance_Betwee
              n_Trees_and_Related_Problems, 1989.

   [PyangBind]
              Shakir, R., "PyangBind",
              PyangBind https://github.com/robshakir/pyangbind, 2018.

   [XML]      W3C, "On Views and XML (Extensible Markup Language)", June
              1999.

   [XSLT]     W3C, "Extensible Stylesheet Language Transformations
              (XSLT) Version 1.0", November 1999.

Appendix A.  Mapping Information for Data Conversion

   Figure 16 shows a mapping list of data fields between Consumer-Facing
   Interface YANG data model and NSF-Facing Interface YANG data model.
   Figure 16 describes the process of passing the data value to the
   appropriate data field of the Data Model in detail after the data
   conversion.

   #policy name mapping
   /consumer-facing/i2nsf-cfi-policy/name
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /name

   #rule name mapping
   /consumer-facing/i2nsf-cfi-policy/rules/name
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/name



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   #time mapping
   /consumer-facing/i2nsf-cfi-policy/
   /rules/event/time/start-date-time
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/event/time/start-date-time

   /consumer-facing/i2nsf-cfi-policy/
   /rules/event/time/end-date-time
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/event/time/end-date-time

   /consumer-facing/i2nsf-cfi-policy/
   /rules/event/time/period/day
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/event/time/period/day

   /consumer-facing/i2nsf-cfi-policy/
   /rules/event/time/period/date
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/event/time/period/date

   /consumer-facing/i2nsf-cfi-policy/
   /rules/event/time/period/month
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/event/time/period/month

   /consumer-facing/i2nsf-cfi-policy/
   /rules/event/time/frequency
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/event/time/frequency

   #firewall-condition source target reference and mapping
   /consumer-facing/i2nsf-cfi-policy/rules/condition
   /firewall-condition/source
       -> reference: /consumer-facing/policy
                     /endpoint-group/user-group/name
       -> reference: /consumer-facing/policy
                     /endpoint-group/device-group/name
           -> extract: /consumer-facing/policy
                       /endpoint-group/user-group/mac-address
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ethernet
                           /source-mac-address
           -> extract: /consumer-facing/policy
                       /endpoint-group/user-group/ip-address
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv4
                           /source-ipv4-network



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               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv4
                           /source-ipv4-range
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv6
                           /source-ipv6-network
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv6
                           /source-ipv6-range

   #firewall-condition destination target reference and mapping
   /consumer-facing/i2nsf-cfi-policy/rule/condition
   /firewall-condition/destination
       -> reference: /consumer-facing/policy
                     /endpoint-group/user-group/name
       -> reference: /consumer-facing/policy
                     /endpoint-group/device-group/name
           -> extract: /consumer-facing/policy
                       /endpoint-group/user-group/mac-address
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ethernet
                           /destination-mac-address
           -> extract: /consumer-facing/policy
                       /endpoint-group/user-group/ip-address
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv4
                           /destination-ipv4-network
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv4
                           /destination-ipv4-range
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv6
                           /destination-ipv6-network
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv6
                           /destination-ipv6-range

   #ddos-condition threshold mapping
   /consumer-facing/i2nsf-cfi-policy/rules/condition
   /ddos-condition/packet-rate-threshold
       -> mapping: /nsf-facing/i2nsf-security-policy/rules/condition
                   /ddos/alert-packet-rate

   /consumer-facing/i2nsf-cfi-policy/rules/condition
   /ddos-condition/packet-byte-threshold
       -> mapping: /nsf-facing/i2nsf-security-policy/rules/condition
                   /ddos/alert-byte-rate




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   /consumer-facing/i2nsf-cfi-policy/rules/condition
   /ddos-condition/flow-rate-threshold
       -> mapping: /nsf-facing/i2nsf-security-policy/rules/condition
                   /ddos/alert-flow-rate

   #payload-condition mapping
   /consumer-facing/i2nsf-cfi-policy/rules/condition
   /payload-condition/content
       -> reference: /consumer-facing/i2nsf-cfi-policy
                     /threat-prevention/payload-content/name
           -> extract: /consumer-facing/i2nsf-cfi-policy
                       /threat-prevention/payload-content/content
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/payload/content

   #voice-condition mapping
   /consumer-facing/i2nsf-cfi-policy/rules/condition
   /voice-condition/source-id
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/condition/voice
                   /source-voice-id

   /consumer-facing/i2nsf-cfi-policy/rules/condition
   /voice-condition/destination-id
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/condition/voice
                   /destination-voice-id

   /consumer-facing/i2nsf-cfi-policy/rules/condition
   /voice-condition/user-agent
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/condition/voice
                   /user-agent

   #geographic-location mapping
   /consumer-facing/i2nsf-cfi-policy/rules/condition/context
   /geographic-location/source
       -> reference: /consumer-facing/i2nsf-cfi-policy
                     /endpoint-groups/location-group/name
           -> extract: /consumer-facing/i2nsf-cfi-policy
                       /endpoint-groups/location-group
                       /geo-ip-ipv4/ipv4-address
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv4
                           /source-ipv4-network
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv4
                           /source-ipv4-range



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           -> extract: /consumer-facing/i2nsf-cfi-policy
                       /endpoint-groups/location-group
                       /continent
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/context
                           /geographic-location/source

   /consumer-facing/i2nsf-cfi-policy/rules/condition/context
   /geographic-location/destination
       -> reference: /consumer-facing/i2nsf-cfi-policy
                     /endpoint-groups/location-group/name
           -> extract: /consumer-facing/i2nsf-cfi-policy
                       /endpoint-groups/location-group
                       /geo-ip-ipv4/ipv4-address
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv4
                           /destination-ipv4-network
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/ipv4
                           /destination-ipv4-range
           -> extract: /consumer-facing/i2nsf-cfi-policy
                       /endpoint-groups/location-group
                       /continent
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/context
                           /geographic-location/destination

   #url-condition mapping
   /consumer-facing/i2nsf-cfi-policy/rules/condition
   /url-condition/url-name
       -> reference: /consumer-facing/i2nsf-cfi-policy
                     /endpoint-groups/url-group/name
           -> extract: /consumer-facing/i2nsf-cfi-policy
                       /endpoint-groups/url-group/url
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/url-category
                           /pre-defined
               -> mapping: /nsf-facing/i2nsf-security-policy
                           /rules/condition/url-category
                           /user-defined

   #rule action name mapping
   /consumer-facing/i2nsf-cfi-policy/rules/actions/primary-action
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/action
                   /packet-action/ingress-action
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/action



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                   /packet-action/egress-action
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/action
                   /advanced-action/content-security-control
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/action
                   /advanced-action/attack-mitigation-control

   /consumer-facing/i2nsf-cfi-policy/rules/actions/secondary-action
       -> mapping: /nsf-facing/i2nsf-security-policy
                   /rules/action/packet-action/log-action

             Figure 16: Mapping Information for Data Conversion

   The mapping list shown in the Figure 16 shows all mapped components.
   This data list should be saved into the NSF Database to provide the
   mapping information for converting the data.  It is important to
   produce the list automatically as the Consumer-Facing Interface and
   NSF-Facing Interface can be extended anytime by vendors according to
   the provided NSF.  The Data Model Mapper in Security Policy
   Translator should be used to produce the mapping model information
   automatically.

Appendix B.  Acknowledgments

   This document is a product by the I2NSF Working Group (WG) including
   WG Chairs (i.e., Linda Dunbar and Yoav Nir) and Diego Lopez.  This
   document took advantage of the review and comments from the following
   experts: Roman Danyliw and Tom Petch.  The authors sincerely
   appreciate their sincere efforts and kind help.

   This work was supported by Institute of Information & Communications
   Technology Planning & Evaluation (IITP) grant funded by the Korea
   MSIT (Ministry of Science and ICT) (2020-0-00395, Standard
   Development of Blockchain based Network Management Automation
   Technology).  This work was supported in part by the IITP
   (R-20160222-002755, Cloud based Security Intelligence Technology
   Development for the Customized Security Service Provisioning).  This
   work was supported in part by the MSIT under the Information
   Technology Research Center (ITRC) support program (IITP-
   2022-2017-0-01633) supervised by the IITP.

Appendix C.  Contributors

   The following are co-authors of this document:






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   Chaehong Chung - Department of Electrical and Computer Engineering,
   Sungkyunkwan University, 2066 Seobu-ro Jangan-gu, Suwon, Gyeonggi-do
   16419, Republic of Korea, EMail: darkhong@skku.edu

   Jung-Soo Park - Electronics and Telecommunications Research
   Institute, 218 Gajeong-Ro, Yuseong-Gu, Daejeon, 34129, Republic of
   Korea, EMail: pjs@etri.re.kr

   Younghan Kim - School of Electronic Engineering, Soongsil University,
   369, Sangdo-ro, Dongjak-gu, Seoul 06978, Republic of Korea, EMail:
   younghak@ssu.ac.kr

Appendix D.  Changes from draft-yang-i2nsf-security-policy-
             translation-10

   The following changes are made from draft-yang-i2nsf-security-policy-
   translation-10:

   *  This version describes the mapping between the latest versions of
      the Consumer-Facing Interface YANG data model
      [I-D.ietf-i2nsf-consumer-facing-interface-dm] and the NSF-Facing
      Interface YANG data model
      [I-D.ietf-i2nsf-nsf-facing-interface-dm].

   *  The title of the document is updated to "Guidelines for Security
      Policy Translation in Interface to Network Security Functions".

   *  Addition of new Section 4.  Relation between Consumer-Facing
      Interface and NSF-Facing Interface Data Models.

   *  Addition of new Section 5.3.4.1.  Handling of Default Values for a
      Low-level Security Policy.

   *  Movement of Mapping Information for Data Conversion into
      Appendix A (previously in Section 4.3.4).

Authors' Addresses

   Jaehoon Paul Jeong (editor)
   Department of Computer Science and Engineering
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon
   Gyeonggi-Do
   16419
   Republic of Korea
   Phone: +82 31 299 4957
   Email: pauljeong@skku.edu



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   URI:   http://iotlab.skku.edu/people-jaehoon-jeong.php


   Patrick Lingga
   Department of Electronic, Electrical and Computer Engineering
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon
   Gyeonggi-Do
   16419
   Republic of Korea
   Phone: +82 31 299 4957
   Email: patricklink@skku.edu


   Jinhyuk Yang
   Department of Electronic, Electrical and Computer Engineering
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon
   Gyeonggi-Do
   16419
   Republic of Korea
   Phone: +82 10 8520 8039
   Email: jin.hyuk@skku.edu


   Jeonghyeon Kim
   Department of Electronic, Electrical and Computer Engineering
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon
   Gyeonggi-Do
   16419
   Republic of Korea
   Phone: +82 31 299 4957
   Email: jeonghyeon12@skku.edu














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