I2NSF Registration Interface YANG Data Model for NSF Capability Registration
draft-ietf-i2nsf-registration-interface-dm-21

I2NSF Working Group                                         S. Hyun, Ed.
Internet-Draft                                        Myongji University
Intended status: Standards Track                           J. Jeong, Ed.
Expires: 12 March 2023                                            T. Roh
                                                                   S. Wi
                                                 Sungkyunkwan University
                                                                 J. Park
                                                                    ETRI
                                                        8 September 2022

    I2NSF Registration Interface YANG Data Model for NSF Capability
                              Registration
             draft-ietf-i2nsf-registration-interface-dm-21

Abstract

   This document defines an information model and a YANG data model for
   Registration Interface between Security Controller and Developer's
   Management System (DMS) in the Interface to Network Security
   Functions (I2NSF) framework to register Network Security Functions
   (NSF) of the DMS with the Security Controller.  The objective of
   these information and data models is to support NSF capability
   registration and query via I2NSF Registration Interface.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   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 12 March 2023.

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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Information Model . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  NSF Capability Registration . . . . . . . . . . . . . . .   5
       4.1.1.  NSF Capability Information  . . . . . . . . . . . . .   6
       4.1.2.  NSF Access Information  . . . . . . . . . . . . . . .   8
     4.2.  NSF Capability Query  . . . . . . . . . . . . . . . . . .   8
   5.  Data Model  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  YANG Tree Diagram . . . . . . . . . . . . . . . . . . . .   8
       5.1.1.  Definitions of Symbols in Tree Diagrams . . . . . . .   9
       5.1.2.  YANG Tree of I2NSF Registration Interface . . . . . .   9
     5.2.  YANG Data Module  . . . . . . . . . . . . . . . . . . . .  12
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  18
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  20
   Appendix A.  XML Examples of an NSF Registration with I2NSF
           Registration Interface Data Model . . . . . . . . . . . .  21
   Appendix B.  XML Examples of an NSF Query with I2NSF Registration
           Interface Data Model  . . . . . . . . . . . . . . . . . .  25
   Appendix C.  NSF Lifecycle Management in NFV Environments . . . .  27
   Appendix D.  Acknowledgments  . . . . . . . . . . . . . . . . . .  27
   Appendix E.  Contributors . . . . . . . . . . . . . . . . . . . .  27
   Appendix F.  Changes from
           draft-ietf-i2nsf-registration-interface-dm-20 . . . . . .  28
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  28

1.  Introduction

   A number of Network Security Functions (NSF) may exist in the
   Interface to Network Security Functions (I2NSF) framework [RFC8329].
   Since each of these NSFs likely has different security capabilities
   from each other, it is important to register the security
   capabilities of the NSF with the security controller.  In addition,
   it is required to search NSFs of some required security capabilities

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   on demand.  As an example, if additional security capabilities are
   required to serve some security service request(s) from an I2NSF
   user, the security controller SHOULD be able to request the DMS for
   NSFs that have the required security capabilities.

   As the main focus of the YANG module defined in
   [I-D.ietf-i2nsf-capability-data-model] is to define the security
   capabilities of an NSF, it lacks in some information (e.g., network
   access information to an NSF) needed by the Security Controller.
   Hence, this document provides extended information for the I2NSF
   Registration Interface.

   This document describes an information model (see Section 4) and an
   augmented YANG [RFC7950] data model from I2NSF Capability YANG data
   model [I-D.ietf-i2nsf-capability-data-model] (see Section 5) for the
   I2NSF Registration Interface [RFC8329] between the security
   controller and the developer's management system (DMS) to support NSF
   capability registration and query via the registration interface.  It
   also describes the operations which SHOULD be performed by the
   security controller and the DMS via the Registration Interface using
   the defined model.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119][RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   This document uses the following terms defined in [RFC3444],
   [RFC8329] and [I-D.ietf-i2nsf-capability-data-model].

   *  Network Security Function (NSF): A function that is responsible
      for a specific treatment of received packets.  A Network Security
      Function can act at various layers of a protocol stack (e.g., at
      the network layer or other OSI layers).  Sample Network Security
      Service Functions are as follows: Firewall, Intrusion Prevention/
      Detection System (IPS/IDS), Deep Packet Inspection (DPI),
      Application Visibility and Control (AVC), network virus and
      malware scanning, sandbox, Data Loss Prevention (DLP), Distributed
      Denial of Service (DDoS) mitigation and TLS proxy.

   *  Data Model: Data Models define managed objects at a lower level of
      abstraction, which include implementation- and protocol-specific
      details, e.g., rules that explain how to map managed objects onto
      lower-level protocol constructs [RFC3444].

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   *  Information Model: Information Models are primarily useful for
      designers to describe the managed environment, for operators to
      understand the modeled objects, and for implementers as a guide to
      the functionality that must be described and coded in the Data
      Models [RFC3444].

   *  YANG: This document follows the guidelines of [RFC8407], uses the
      common YANG types defined in [RFC6991], and adopts the Network
      Management Datastore Architecture (NMDA) [RFC8342].  The meaning
      of the symbols in tree diagrams is defined in [RFC8340].

3.  Objectives

   *  Registering NSFs with the I2NSF framework: Developer's Management
      System (DMS) in I2NSF framework is typically run by an NSF vendor,
      and uses Registration Interface to provide NSFs developed by the
      NSF vendor to Security Controller.  Since there may be multiple
      vendors that provide NSFs for a target network, the I2NSF
      Registration Interface can be used as a standard interface for the
      DMSs to provide NSFs capability information to the Security
      Controller.  For the registered NSFs, Security Controller
      maintains a catalog of the capabilities of those NSFs to select
      appropriate NSFs for the requested security services.

   *  Updating the capabilities of registered NSFs: After an NSF is
      registered with Security Controller, some modifications on the
      capability of the NSF MAY be required later.  In this case, DMS
      uses Registration Interface to update the capability of the NSF,
      and this update SHOULD be reflected in the catalog of NSFs.

   *  Asking DMS about some required capabilities: In cases that some
      security capabilities are required to serve the security service
      request from an I2NSF user, Security Controller searches through
      the registered NSFs to find ones that can provide the required
      capabilities.  But Security Controller might fail to find any NSFs
      having the required capabilities among the registered NSFs.  In
      this case, Security Controller needs to request DMS for additional
      NSF(s) that can provide the required security capabilities via
      Registration Interface.

4.  Information Model

   The I2NSF registration interface is used by Security Controller and
   Developer's Management System (DMS) in I2NSF framework.  The
   following summarizes the operations done through the registration
   interface:

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   1)  DMS registers NSFs and their capabilities with Security
       Controller via the registration interface.  DMS also uses the
       registration interface to update the capabilities of the NSFs
       registered previously.

   2)  In case that an I2NSF user requests a certain security service,
       and the Security Controller fails to find some of the required
       security capabilities from any registered NSFs, the Security
       Controller queries DMS about an additional NSF(s) having the
       required security capabilities via the registration interface.

   Figure 1 shows the information model of the I2NSF registration
   interface, which consists of two submodels: NSF capability
   registration and NSF capability query.  Each submodel is used for the
   operations listed above.  The remainder of this section will provide
   in-depth explanations of each submodel.

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      I2NSF Registration Interface Information Model       |
     |                                                           |
     |         +-+-+-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+-+-+          |
     |         | NSF Capability  |  | NSF Capability  |          |
     |         | Registration    |  | Query           |          |
     |         +-+-+-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+-+-+          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          Figure 1: I2NSF Registration Interface Information Model

4.1.  NSF Capability Registration

   This submodel is used by DMS to register an NSF with Security
   Controller.  Figure 2 shows how this submodel is constructed.  The
   most important part in Figure 2 is the NSF capability, and this
   specifies the set of capabilities that the NSF to be registered can
   offer.  The NSF Name contains a unique name of this NSF with the
   specified set of capabilities.  When registering the NSF, DMS
   additionally includes the network access information of the NSF which
   is required to enable network communications with the NSF.

   The following will further explain the NSF capability information and
   the NSF access information in more detail.

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                          +-+-+-+-+-+-+-+-+-+
                          | NSF Capability  |
                          | Registration    |
                          +-+-+-+-+^+-+-+-+-+
                                   |
             +---------------------+--------------------+
             |                     |                    |
             |                     |                    |
       +-+-+-+-+-+-+       +-+-+-+-+-+-+-+-+      +-+-+-+-+-+-+-+
       |   NSF     |       | NSF Capability|      | NSF Access  |
       |   Name    |       | Information   |      | Information |
       +-+-+-+-+-+-+       +-+-+-+-+-+-+-+-+      +-+-+-+-+-+-+-+

              Figure 2: NSF Capability Registration Sub-Model

4.1.1.  NSF Capability Information

   NSF Capability Information basically describes the security
   capabilities of an NSF.  In Figure 3, we show capability objects of
   an NSF.  Following the information model of NSF capabilities defined
   in [I-D.ietf-i2nsf-capability-data-model], we share the same I2NSF
   security capabilities: Directional Capabilities, Event Capabilities,
   Condition Capabilities, Action Capabilities, Resolution Strategy
   Capabilities, Default Action Capabilities.  Also, NSF Capability
   Information additionally contains the specification of an NSF as
   shown in Figure 3.

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                             +-+-+-+-+-+-+-+-+-+
                             | NSF Capability  |
                             |   Information   |
                             +-+-+-+-^-+-+-+-+-+
                                     |
                                     |
              +----------------------+----------------------+
              |                                             |
              |                                             |
      +-+-+-+-+-+-+-+-+                             +-+-+-+-+-+-+-+-+
      |     I2NSF     |                             |      NSF      |
      | Capabilities  |                             | Specification |
      +-+-+-+-+-+-+-+-+                             +-+-+-+-+-+-+-+-+
              |
       +------+-------------+----------------+----------------+-------+
       |                    |                |                |       |
   +-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+ |
   | Directional |  |    Event    |  |  Condition  |  |    Action   | |
   | Capabilities|  | Capabilities|  | Capabilities|  | Capabilities| |
   +-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+ |
                                                                      |
                    +--------------------+--------------------+-------+
                    |                    |
              +-+-+-+-+-+-+-+      +-+-+-+-+-+-+-+
              | Resolution  |      |   Default   |
              | Strategy    |      |   Action    |
              | Capabilities|      | Capabilities|
              +-+-+-+-+-+-+-+      +-+-+-+-+-+-+-+

                    Figure 3: NSF Capability Information

4.1.1.1.  NSF Specification

   This information represents the processing capability of an NSF.
   Assuming that the current workload status of each NSF is being
   collected through NSF monitoring
   [I-D.ietf-i2nsf-nsf-monitoring-data-model], this capability
   information of the NSF can be used to determine whether the NSF is in
   congestion by comparing it with the current workload of the NSF.
   Moreover, this information can specify an available amount of each
   type of resource, such as processing power which are available on the
   NSF.  (The registration interface can control the usages and
   limitations of the created instance and make the appropriate request
   according to the status.)  As illustrated in Figure 4, this
   information consists of two items: Processing and Bandwidth.
   Processing information describes the NSF's available processing
   power.  Bandwidth describes the information about available network
   amount in two cases, outbound, inbound.  These two information can be

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   used for the NSF's instance request.

                      +-+-+-+-+-+-+-+-+-+
                      |       NSF       |
                      |  Specification  |
                      +-+-+-+-^-+-+-+-+-+
                              |
                  +----------------------------+
                  |                            |
                  |                            |
          +-+-+-+-+-+-+-+-+            +-+-+-+-+-+-+-+
          |  Processing   |            |  Bandwidth  |
          +-+-+-+-+-+-+-+-+            +-+-+-+-+-+-+-+

                    Figure 4: NSF Specification Overview

4.1.2.  NSF Access Information

   NSF Access Information contains the following that are required to
   communicate with an NSF through NETCONF [RFC6241] or RESTCONF
   [RFC8040]: an IP address (i.e., IPv4 or IPv6 address) and a port
   number.  Note that TCP is used as a transport layer protocol due to
   either NETCONF or RESTCONF.  In this document, NSF Access Information
   is used to identify a specific NSF instance.  That is, NSF Access
   Information is the signature (i.e., unique identifier) of an NSF
   instance in the overall I2NSF system.

4.2.  NSF Capability Query

   Security Controller MAY require some additional capabilities to serve
   the security service request from an I2NSF user, but none of the
   registered NSFs has the required capabilities.  In this case,
   Security Controller makes a description of the required capabilities
   by using the NSF capability information submodel in Section 4.1.1,
   and sends DMS a query about which NSF(s) can provide these
   capabilities.

5.  Data Model

5.1.  YANG Tree Diagram

   This section provides the YANG Tree diagram of the I2NSF registration
   interface.

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5.1.1.  Definitions of Symbols in Tree Diagrams

   A simplified graphical representation of the data model is used in
   this section.  The meaning of the symbols used in the following
   diagrams [RFC8431] is as follows:

      Brackets "[" and "]" enclose list keys.

      Abbreviations before data node names: "rw" means configuration
      (read-write) and "ro" state data (read-only).

      Symbols after data node names: "?" means an optional node and "*"
      denotes a "list" and "leaf-list".

      Parentheses enclose choice and case nodes, and case nodes are also
      marked with a colon (":").

      Ellipsis ("...") stands for contents of subtrees that are not
      shown.

5.1.2.  YANG Tree of I2NSF Registration Interface

   The I2NSF registration interface is used by the Developer's
   Management System (DMS) to register NSFs and their capabilities with
   the Security Controller.  In case that the Security Controller fails
   to find any NSF among the registered NSFs which can provide some
   required capabilities, Security Controller uses the registration
   interface to query DMS about NSF(s) having the required capabilities.
   The following sections describe the YANG data models to support these
   operations.

5.1.2.1.  NSF Capability Registration

   This section describe the YANG tree for the NSF capability
   registration.

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     NSF Capability Registration
     augment /i2nsfcap:nsf:
       +--rw nsf-specification
       |  +--rw processing
       |  |  +--rw processing-average?   uint16
       |  |  +--rw processing-peak?      uint16
       |  +--rw bandwidth
       |     +--rw outbound
       |     |  +--rw outbound-average?   uint32
       |     |  +--rw outbound-peak?      uint32
       |     +--rw inbound
       |        +--rw inbound-average?   uint32
       |        +--rw inbound-peak?      uint32
       +--rw nsf-access-info
          +--rw ip?                    inet:ip-address-no-zone
          +--rw port?                  inet:port-number
          +--rw management-protocol?   enumeration

         Figure 5: YANG Tree of NSF Capability Registration Module

   When registering an NSF with Security Controller, DMS uses the
   augmented I2NSF Capability YANG Data Model
   [I-D.ietf-i2nsf-capability-data-model] to describe what capabilities
   the NSF can offer.  DMS includes the access information of the NSF
   which is required to make a network connection with the NSF as well
   as the specification of the NSFs.  The NSF access information
   consists of ip, port, and management-protocol.  The field of ip can
   have either an IPv4 address or an IPv6 address.  The port field is
   used to get the transport protocol port number.  As I2NSF uses a YANG
   data model, the management protocol can be either NETCONF or
   RESTCONF.

   The DMS can also include the resource capacity information in terms
   of processing power and network bandwidth of the NSF.  Detailed
   overview of NSF specification can be seen in Section 4.1.1.1.

5.1.2.2.  NSF Capability Query

   This section describe the YANG tree for the NSF capability query.

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   I2NSF Capability Query
   rpcs:
     +---x nsf-capability-query
        +---w input
        |  +---w query-nsf-capability
        |     +---w directional-capabilities*           identityref
        |     +---w event-capabilities
        |     |  +---w system-event-capability*   identityref
        |     |  +---w system-alarm-capability*   identityref
        |     +---w condition-capabilities
        |     |  +---w generic-nsf-capabilities
        |     |  |  +---w ethernet-capability*   identityref
        |     |  |  +---w ipv4-capability*       identityref
        |     |  |  +---w ipv6-capability*       identityref
        |     |  |  +---w icmpv4-capability*     identityref
        |     |  |  +---w icmpv6-capability*     identityref
        |     |  |  +---w tcp-capability*        identityref
        |     |  |  +---w udp-capability*        identityref
        |     |  |  +---w sctp-capability*       identityref
        |     |  |  +---w dccp-capability*       identityref
        |     |  +---w advanced-nsf-capabilities
        |     |  |  +---w anti-ddos-capability*             identityref
        |     |  |  +---w ips-capability*                   identityref
        |     |  |  +---w anti-virus-capability*            identityref
        |     |  |  +---w url-filtering-capability*         identityref
        |     |  |  +---w voip-vocn-filtering-capability*   identityref
        |     |  +---w context-capabilities
        |     |     +---w time-capabilities*                 identityref
        |     |     +---w application-filter-capabilities*   identityref
        |     |     +---w device-type-capabilities*          identityref
        |     |     +---w user-condition-capabilities*       identityref
        |     |     +---w geographic-capabilities*           identityref
        |     +---w action-capabilities
        |     |  +---w ingress-action-capability*   identityref
        |     |  +---w egress-action-capability*    identityref
        |     |  +---w log-action-capability*       identityref
        |     +---w resolution-strategy-capabilities*   identityref
        |     +---w default-action-capabilities*        identityref
        +--ro output
           +--ro nsf-access-info
              +--ro nsf-name?              string
              +--ro ip?                    inet:ip-address-no-zone
              +--ro port?                  inet:port-number
              +--ro management-protocol?   enumeration

           Figure 6: YANG Tree of NSF Capability Query Module

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   Security Controller MAY require some additional capabilities to
   provide the security service requested by an I2NSF user, but none of
   the registered NSFs has the required capabilities.  In this case,
   Security Controller makes a description of the required capabilities
   using this module and then queries DMS about which NSF(s) can provide
   these capabilities.  Use NETCONF RPCs to send a NSF capability query.
   Input data is query-i2nsf-capability-info and output data is nsf-
   access-info.  In Figure 6, the ietf-i2nsf-capability refers to the
   module defined in [I-D.ietf-i2nsf-capability-data-model].

5.2.  YANG Data Module

   This section provides a YANG module of the data model for the
   registration interface between Security Controller and Developer's
   Management System, as defined in Section 4.

   This YANG module imports from [RFC6991] and
   [I-D.ietf-i2nsf-capability-data-model].  It makes references to
   [RFC6241] [RFC8040]

   <CODE BEGINS> file "ietf-i2nsf-registration-interface@2022-09-08.yang"
   module ietf-i2nsf-registration-interface {
     yang-version 1.1;

     namespace
       "urn:ietf:params:xml:ns:yang:ietf-i2nsf-registration-interface";

     prefix
       i2nsfri;

     //RFC Ed.: replace occurences of XXXX with actual RFC number and
     //remove this note

     import ietf-inet-types {
       prefix inet;
       reference "RFC 6991";
     }
     import ietf-i2nsf-capability {
       prefix i2nsfcap;
     // RFC Ed.: replace YYYY with actual RFC number of
     // draft-ietf-i2nsf-capability-data-model and remove this note.
       reference "RFC YYYY: I2NSF Capability YANG Data Model";
     }

     organization
      "IETF I2NSF (Interface to Network Security Functions)
       Working Group";

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     contact
       "WG Web: <https://datatracker.ietf.org/wg/i2nsf>
        WG List: <mailto:i2nsf@ietf.org>

        Editor: Sangwon Hyun
        <mailto:shyun@mju.ac.kr>

        Editor: Jaehoon Paul Jeong
        <mailto:pauljeong@skku.edu>";

     description
       "This module defines a YANG data model for I2NSF
        Registration Interface.

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
        'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
        'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this
        document are to be interpreted as described in BCP 14
        (RFC 2119) (RFC 8174) when, and only when, they appear
        in all capitals, as shown here.

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

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Revised BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; see
        the RFC itself for full legal notices.";

     revision "2022-09-08" {
       description "Initial revision";
       reference
         "RFC XXXX: I2NSF Registration Interface YANG Data Model";
       // RFC Ed.: replace XXXX with actual RFC number and remove
       // this note
     }

     grouping nsf-specification {
       description
         "Description of the specification of an NSF";

       container processing {
         description

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           "Processing power of an NSF in the unit of GHz (gigahertz)";

         leaf processing-average {
           type uint16;
           units "GHz";
           description
             "Average processing power";
         }
         leaf processing-peak {
           type uint16;
           units "GHz";
           description
             "Peak processing power";
         }
       }

       container bandwidth {
         description
           "Network bandwidth available on an NSF
            in the unit of Mbps (megabits per second)";

         container outbound {
           description
             "Outbound network bandwidth";
           leaf outbound-average {
             type uint32;
             units "Mbps";
             description
               "Average outbound bandwidth";
           }
           leaf outbound-peak {
             type uint32;
             units "Mbps";
             description
               "Peak outbound bandwidth";
           }
         }

         container inbound {
           description
             "Inbound network bandwidth";
           leaf inbound-average {
             type uint32;
             units "Mbps";
             description
               "Average inbound bandwidth";
           }
           leaf inbound-peak {

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             type uint32;
             units "Mbps";
             description
               "Peak inbound bandwidth";
           }
         }
       }
     }

     grouping nsf-access-info {
       description
         "Information required to access an NSF";
       leaf ip {
         type inet:ip-address-no-zone;
         description
           "Either an IPv4 address or an IPv6 address of this NSF";
       }
       leaf port {
         type inet:port-number;
         description
           "Port available on this NSF";
       }
       leaf management-protocol {
         type enumeration {
           enum NETCONF {
             description
               "Represents the management protocol NETCONF";
             reference
               "RFC 6241: Network Configuration Protocol (NETCONF)";
           }
           enum RESTCONF {
             description
               "Represents the management protocol RESTCONF";
             reference
               "RFC 8040: RESTCONF Protocol";
           }
         }
         description
           "The management protocol used to manage the NSF";
       }
     }

     augment "/i2nsfcap:nsf" {
       description
         "Augmented information of an NSF's capability that DMS
          registers with Security Controller";
       reference
         "draft-ietf-i2nsf-capability-data-model-32: I2NSF Capability

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          YANG Data Model";
       container nsf-specification {
         description
           "The specification of an NSF";
         uses nsf-specification;
       }
       container nsf-access-info {
         description
           "Network access information of this NSF";
         uses nsf-access-info;
       }
     }

     rpc nsf-capability-query {
       description
         "Description of the capabilities that the
          Security Controller requests to the DMS";
       input {
         container query-nsf-capability {
           description
             "Description of the capabilities to request";
           uses i2nsfcap:nsf-capabilities;
           reference "RFC YYYY: I2NSF Capability YANG Data Model";
         //RFC Ed.: replace YYYY with actual RFC number of
         //draft-ietf-i2nsf-capability-data-model and remove this note.
         }
       }
       output {
         container nsf-access-info {
           description
             "Network access information of an NSF
              with the requested capabilities";
           leaf nsf-name {
             type string;
             description
             "The name of this registered NSF. The NSF name MUST be
              unique to identify the NSF with the capability. The name
              can be an arbitrary string including FQDN (Fully Qualified
              Domain Name).";
           }
           uses nsf-access-info;
         }
       }
     }
   }
   <CODE ENDS>

              Figure 7: Registration Interface YANG Data Model

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6.  IANA Considerations

   This document requests IANA to register the following URI in the
   "IETF XML Registry" [RFC3688]:

   URI: urn:ietf:params:xml:ns:yang:ietf-i2nsf-registration-interface
   Registrant Contact: The IESG.
   XML: N/A; the requested URI is an XML namespace.

   This document requests IANA to register the following YANG module in
   the "YANG Module Names" registry [RFC7950][RFC8525]:

Name: ietf-i2nsf-registration-interface
Namespace: urn:ietf:params:xml:ns:yang:ietf-i2nsf-registration-interface
Prefix: i2nsfri
Reference: RFC XXXX

// RFC Ed.: replace XXXX with actual RFC number and remove
// this note

7.  Security Considerations

   The YANG module specified in this document defines a data schema
   designed to be accessed through network management protocols such as
   NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer is
   the secure transport layer, and the required secure transport is
   Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer is HTTPS,
   and the required secure transport is TLS [RFC8446].

   The NETCONF access control model [RFC8341] provides a means of
   restricting access to specific NETCONF or RESTCONF users to a
   preconfigured subset of all available NETCONF or RESTCONF protocol
   operations and content.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes MAY be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

   *  nsf-registration: The attacker MAY exploit this to register a
      compromised or malicious NSF instead of a legitimate NSF with the
      Security Controller.

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   *  nsf-specification: The attacker MAY provide incorrect information
      of the specification of any target NSF by illegally modifying
      this.

   *  nsf-capability-info: The attacker MAY provide incorrect
      information of the security capability of any target NSF by
      illegally modifying this.

   *  nsf-access-info: The attacker MAY provide incorrect network access
      information of any target NSF by illegally modifying this.

   Some of the readable data nodes in this YANG module MAY be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  These are the subtrees and data
   nodes and their sensitivity/vulnerability:

   *  nsf-registration: The attacker MAY try to gather some sensitive
      information of a registered NSF by sniffing this.

   *  nsf-specification: The attacker MAY gather the specification
      information of any target NSF and misuse the information for
      subsequent attacks.

   *  nsf-capability-info: The attacker MAY gather the security
      capability information of any target NSF and misuse the
      information for subsequent attacks.

   *  nsf-access-info: The attacker MAY gather the network access
      information of any target NSF and misuse the information for
      subsequent attacks.

   The RPC operation in this YANG module MAY be considered sensitive or
   vulnerable in some network environments.  It is thus important to
   control access to this operation.  The following is the operation and
   its sensitivity/vulnerability:

   *  nsf-capability-query: The attacker MAY exploit this RPC operation
      to deteriorate the availability of the DMS and/or gather the
      information of some interested NSFs from the DMS.

8.  References

8.1.  Normative References

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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [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>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

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   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <https://www.rfc-editor.org/info/rfc8407>.

   [RFC8431]  Wang, L., Chen, M., Dass, A., Ananthakrishnan, H., Kini,
              S., and N. Bahadur, "A YANG Data Model for the Routing
              Information Base (RIB)", RFC 8431, DOI 10.17487/RFC8431,
              September 2018, <https://www.rfc-editor.org/info/rfc8431>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8525]  Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
              and R. Wilton, "YANG Library", RFC 8525,
              DOI 10.17487/RFC8525, March 2019,
              <https://www.rfc-editor.org/info/rfc8525>.

   [I-D.ietf-i2nsf-capability-data-model]
              Hares, S., Jeong, J. P., Kim, J. T., Moskowitz, R., and Q.
              Lin, "I2NSF Capability YANG Data Model", Work in Progress,
              Internet-Draft, draft-ietf-i2nsf-capability-data-model-32,
              23 May 2022, <https://www.ietf.org/archive/id/draft-ietf-
              i2nsf-capability-data-model-32.txt>.

8.2.  Informative References

   [RFC3444]  Pras, A. and J. Schoenwaelder, "On the Difference between
              Information Models and Data Models", RFC 3444,
              DOI 10.17487/RFC3444, January 2003,
              <https://www.rfc-editor.org/info/rfc3444>.

   [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
              Reserved for Documentation", RFC 3849,
              DOI 10.17487/RFC3849, July 2004,
              <https://www.rfc-editor.org/info/rfc3849>.

   [RFC5737]  Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks
              Reserved for Documentation", RFC 5737,
              DOI 10.17487/RFC5737, January 2010,
              <https://www.rfc-editor.org/info/rfc5737>.

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   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
              <https://www.rfc-editor.org/info/rfc7348>.

   [I-D.ietf-i2nsf-nsf-monitoring-data-model]
              Jeong, J. P., Lingga, P., Hares, S., Xia, L. F., and H.
              Birkholz, "I2NSF NSF Monitoring Interface YANG Data
              Model", Work in Progress, Internet-Draft, draft-ietf-
              i2nsf-nsf-monitoring-data-model-20, 1 June 2022,
              <https://www.ietf.org/archive/id/draft-ietf-i2nsf-nsf-
              monitoring-data-model-20.txt>.

   [I-D.ietf-nvo3-vxlan-gpe]
              (Editor), F. M., (editor), L. K., and U. E. (editor),
              "Generic Protocol Extension for VXLAN (VXLAN-GPE)", Work
              in Progress, Internet-Draft, draft-ietf-nvo3-vxlan-gpe-12,
              22 September 2021, <https://www.ietf.org/archive/id/draft-
              ietf-nvo3-vxlan-gpe-12.txt>.

   [nfv-framework]
              "Network Functions Virtualisation (NFV); Architectureal
              Framework", ETSI GS NFV 002 ETSI GS NFV 002 V1.1.1,
              October 2013.

Appendix A.  XML Examples of an NSF Registration with I2NSF Registration
             Interface Data Model

   This section shows XML examples of the I2NSF Registration Interface
   data model for registering the capabilities in either IPv4 networks
   [RFC5737] or IPv6 networks [RFC3849] with Security Controller.

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   <nsf
     xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-capability"
     xmlns:i2nsfri="urn:ietf:params:xml:ns:yang
                    :ietf-i2nsf-registration-interface">
     <nsf-name>ipv4_general_firewall</nsf-name>
     <condition-capabilities>
       <generic-nsf-capabilities>
         <ipv4-capability>next-header</ipv4-capability>
         <ipv4-capability>source-address</ipv4-capability>
         <ipv4-capability>destination-address</ipv4-capability>
         <tcp-capability>source-port-number</tcp-capability>
         <tcp-capability>destination-port-number</tcp-capability>
       </generic-nsf-capabilities>
     </condition-capabilities>
     <action-capabilities>
       <ingress-action-capability>pass</ingress-action-capability>
       <ingress-action-capability>drop</ingress-action-capability>
       <ingress-action-capability>mirror</ingress-action-capability>
       <egress-action-capability>pass</egress-action-capability>
       <egress-action-capability>drop</egress-action-capability>
       <egress-action-capability>mirror</egress-action-capability>
     </action-capabilities>
     <i2nsfri:nsf-specification>
       <i2nsfri:processing>
         <i2nsfri:processing-average>1000</i2nsfri:processing-average>
         <i2nsfri:processing-peak>5000</i2nsfri:processing-peak>
       </i2nsfri:processing>
       <i2nsfri:bandwidth>
         <i2nsfri:outbound>
           <i2nsfri:outbound-average>1000</i2nsfri:outbound-average>
           <i2nsfri:outbound-peak>5000</i2nsfri:outbound-peak>
         </i2nsfri:outbound>
         <i2nsfri:inbound>
           <i2nsfri:inbound-average>1000</i2nsfri:inbound-average>
           <i2nsfri:inbound-peak>5000</i2nsfri:inbound-peak>
         </i2nsfri:inbound>
       </i2nsfri:bandwidth>
     </i2nsfri:nsf-specification>
     <i2nsfri:nsf-access-info>
       <i2nsfri:ip>192.0.2.11</i2nsfri:ip>
       <i2nsfri:port>49152</i2nsfri:port>
       <i2nsfri:management-protocol>
         i2nsfri:NETCONF
       </i2nsfri:management-protocol>
     </i2nsfri:nsf-access-info>
   </nsf>

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         Figure 8: Configuration XML for Registration of a General
                        Firewall in an IPv4 Network

   Figure 8 shows the configuration XML for registering a general
   firewall in an IPv4 network [RFC5737] and its capabilities as
   follows.

   1.  The instance name of the NSF is ipv4_general_firewall.

   2.  The NSF can inspect IPv4 protocol header field, source
       address(es), and destination address(es).

   3.  The NSF can inspect the port number(s) for the transport layer
       protocol, i.e., TCP.

   4.  The NSF can determine whether the packets are allowed to pass,
       drop, or mirror.

   5.  The NSF can have processing power and bandwidth.

   6.  The IPv4 address of the NSF is 192.0.2.11.

   7.  The port of the NSF is 49152.

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   <nsf
     xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-capability"
     xmlns:i2nsfri="urn:ietf:params:xml:ns:yang
                    :ietf-i2nsf-registration-interface">
     <nsf-name>ipv6_general_firewall</nsf-name>
     <condition-capabilities>
       <generic-nsf-capabilities>
         <ipv6-capability>next-header</ipv6-capability>
         <ipv6-capability>source-address</ipv6-capability>
         <ipv6-capability>destination-address</ipv6-capability>
         <tcp-capability>source-port-number</tcp-capability>
         <tcp-capability>destination-port-number</tcp-capability>
       </generic-nsf-capabilities>
     </condition-capabilities>
     <action-capabilities>
       <ingress-action-capability>pass</ingress-action-capability>
       <ingress-action-capability>drop</ingress-action-capability>
       <ingress-action-capability>mirror</ingress-action-capability>
       <egress-action-capability>pass</egress-action-capability>
       <egress-action-capability>drop</egress-action-capability>
       <egress-action-capability>mirror</egress-action-capability>
     </action-capabilities>
     <i2nsfri:nsf-specification>
       <i2nsfri:processing>
         <i2nsfri:processing-average>1000</i2nsfri:processing-average>
         <i2nsfri:processing-peak>5000</i2nsfri:processing-peak>
       </i2nsfri:processing>
       <i2nsfri:bandwidth>
         <i2nsfri:outbound>
           <i2nsfri:outbound-average>1000</i2nsfri:outbound-average>
           <i2nsfri:outbound-peak>5000</i2nsfri:outbound-peak>
         </i2nsfri:outbound>
         <i2nsfri:inbound>
           <i2nsfri:inbound-average>1000</i2nsfri:inbound-average>
           <i2nsfri:inbound-peak>5000</i2nsfri:inbound-peak>
         </i2nsfri:inbound>
       </i2nsfri:bandwidth>
     </i2nsfri:nsf-specification>
     <i2nsfri:nsf-access-info>
       <i2nsfri:ip>2001:db8:0:1::11</i2nsfri:ip>
       <i2nsfri:port>49152</i2nsfri:port>
       <i2nsfri:management-protocol>
         i2nsfri:NETCONF
       </i2nsfri:management-protocol>
     </i2nsfri:nsf-access-info>
   </nsf>

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         Figure 9: Configuration XML for Registration of a General
                        Firewall in an IPv6 Network

   In addition, Figure 9 shows the configuration XML for registering a
   general firewall in an IPv6 network [RFC3849] and its capabilities as
   follows.

   1.  The instance name of the NSF is ipv6_general_firewall.

   2.  The NSF can inspect IPv6 next header, flow direction, source
       address(es), and destination address(es)

   3.  The NSF can inspect the port number(s) and flow direction for the
       transport layer protocol, i.e., TCP and UDP.

   4.  The NSF can determine whether the packets are allowed to pass,
       drop, or mirror.

   5.  The NSF can have processing power and bandwidth.

   6.  The IPv6 address of the NSF is 2001:db8:0:1::11.

   7.  The port of the NSF is 49152.

Appendix B.  XML Examples of an NSF Query with I2NSF Registration
             Interface Data Model

   This section shows an XML example of the Security Controller
   requesting an additional NSF with a certain capability.  In this
   example, an I2NSF user requests a security service that is able to
   block the specified websites.  When the Security Controller checks
   that no registered NSF can provide such a service, it makes a query
   to the DMS with the following XML:

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<rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <rock-the-house
  xmlns="urn:ietf:params:xml:ns:yang:ietf-i2nsf-registration-interface">
    <nsf-capability-query>
      <query-nsf-capability>
        <condition-capabilities>
          <advanced-nsf-capabilities>
            <url-filtering-capability>
              user-defined
            </url-filtering-capability>
          </advanced-nsf-capabilities>
        </condition-capabilities>
        <action-capabilities>
          <ingress-action-capability>drop</ingress-action-capability>
          <egress-action-capability>drop</egress-action-capability>
        </action-capabilities>
      </query-nsf-capability>
    </nsf-capability-query>
  </rock-the-house>
</rpc>

             Figure 10: XML for NSF Query of a Web Filter

   Figure 10 shows the XML for requesting an unregistered web filter
   with its capabilities as follows.

   1.  The NSF can inspect a URL matched from a user-defined URL where
       the user can specify their own URL.

   2.  The NSF can control the network by dropping the packets that
       match the condition.  It can drop packets that are entering or
       leaving the target network.

   After receiving a query given in Figure 10, the DMS can reply with
   following XML:

   <rpc-reply message-id="101"
             xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
     <nsf-access-info>
       <nsf-name>web_filter</nsf-name>
       <ip>192.0.2.13</ip>
       <port>49152</port>
       <management-protocol>NETCONF</management-protocol>
     </nsf-access-info>
   </rpc-reply>

         Figure 11: XML for the Reply of NSF Query of a Web Filter

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   In the reply shown in Figure 11, the additional NSF called web_filter
   can be used by accessing the NSF with the IPv4 address of 192.0.2.13
   and the port number of 49152, using the NETCONF management protocol.

Appendix C.  NSF Lifecycle Management in NFV Environments

   Network Functions Virtualization (NFV) can be used to implement I2NSF
   framework.  In NFV environments, NSFs are deployed as virtual network
   functions (VNFs).  Security Controller can be implemented as an
   Element Management (EM) of the NFV architecture, and is connected
   with the VNF Manager (VNFM) via the Ve-Vnfm interface
   [nfv-framework].  Security Controller can use this interface for the
   purpose of the lifecycle management of NSFs.  If some NSFs need to be
   instantiated to enforce security policies in the I2NSF framework,
   Security Controller could request the VNFM to instantiate them
   through the Ve-Vnfm interface.  Or if an NSF, running as a VNF, is
   not used by any traffic flows for a time period, Security Controller
   MAY request deinstantiating it through the interface for efficient
   resource utilization.

Appendix D.  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
   people: Roman Danyliw, Reshad Rahman (YANG doctor), and Tom Petch.
   We 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) (No. 2016-0-00078, Cloud Based
   Security Intelligence Technology Development for the Customized
   Security Service Provisioning).  This work was supported in part by
   the IITP (2020-0-00395-003, Standard Development of Blockchain based
   Network Management Automation Technology).

Appendix E.  Contributors

   The following are co-authors of this document:

   Patrick Lingga - Department of Electrical and Computer Engineering,
   Sungkyunkwan University, 2066 Seo-ro Jangan-gu, Suwon, Gyeonggi-do
   16419, Republic of Korea.  EMail: patricklink@skku.edu

   Jinyong (Tim) Kim - Department of Electronic, Electrical and Computer
   Engineering, Sungkyunkwan University, 2066 Seo-ro Jangan-gu, Suwon,
   Gyeonggi-do 16419, Republic of Korea.  EMail: timkim@skku.edu

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

   Susan Hares - Huawei, 7453 Hickory Hill, Saline, MI 48176, USA.
   EMail: shares@ndzh.com

   Diego R.  Lopez - Telefonica I+D, Jose Manuel Lara, 9, Seville,
   41013, Spain.  EMail: diego.r.lopez@telefonica.com

Appendix F.  Changes from draft-ietf-i2nsf-registration-interface-dm-20

   The following changes are made from draft-ietf-i2nsf-registration-
   interface-dm-20:

   *  The updates are made following Qin Wu's comments.  The important
      updates are as follows:

      1.  This version clarifies the third objective (i.e., an query to
          an NSF for a given security capability) discussed in
          Section 3.

      2.  This version provides a new XML example for requesting
          additional NSF via the I2NSF Registration Interface, that is,
          an query to an NSF for a given security capability in
          Appendix B.

      3.  This version updates the information model and data model for
          NSF registration by using the "augment" statement instead of
          reusing the "grouping" from the
          [I-D.ietf-i2nsf-capability-data-model].

Authors' Addresses

   Sangwon Hyun (editor)
   Department of Computer Engineering
   Myongji University
   116 Myongji-ro, Cheoin-gu
   Yongin
   Gyeonggi-do
   17058
   Republic of Korea
   Email: shyun@mju.ac.kr

   Jaehoon Paul Jeong (editor)
   Department of Computer Science and Engineering
   Sungkyunkwan University

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Internet-Draft   Registration Interface YANG Data Model   September 2022

   2066 Seobu-Ro, Jangan-Gu
   Suwon
   Gyeonggi-Do
   16419
   Republic of Korea
   Phone: +82 31 299 4957
   Email: pauljeong@skku.edu
   URI:   http://iotlab.skku.edu/people-jaehoon-jeong.php

   Taekyun Roh
   Department of Electronic, Electrical and Computer Engineering
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon
   Gyeonggi-Do
   16419
   Republic of Korea
   Phone: +82 31 290 7222
   Email: tkroh0198@skku.edu

   Sarang Wi
   Department of Electronic, Electrical and Computer Engineering
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon
   Gyeonggi-Do
   16419
   Republic of Korea
   Phone: +82 31 290 7222
   Email: dnl9795@skku.edu

   Jung-Soo Park
   Electronics and Telecommunications Research Institute
   218 Gajeong-Ro, Yuseong-Gu
   Daejeon
   305-700
   Republic of Korea
   Phone: +82 42 860 6514
   Email: pjs@etri.re.kr

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