I2NSF Working Group                                             J. Jeong
Internet-Draft                                                 P. Lingga
Intended status: Informational                   Sungkyunkwan University
Expires: August 26, 2021                                         J. Park
                                                                    ETRI
                                                       February 22, 2021


 An Extension of I2NSF Framework for Security Management Automation in
                     Cloud-Based Security Services
          draft-jeong-i2nsf-security-management-automation-01

Abstract

   This document describes an extension of the framework of Interface to
   Network Security Functions (I2NSF) for Security Management Automation
   (SMA) in cloud-based security services.  The security management
   automation in this document deals with a security polity translation
   and a feedback-based security service enforcement.  To support these
   two features in SMA, this document specifies an augmented
   architecture of the I2NSF framework with a new system component and a
   new interface.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at 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 August 26, 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of



Jeong, et al.            Expires August 26, 2021                [Page 1]


Internet-Draft    I2NSF Security Management Automation     February 2021


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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  I2NSF Framework for Security Management Automation  . . . . .   4
     3.1.  Components with I2NSF Framework for Security Management
           Automation  . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Interfaces with SMA-Based I2NSF Framework . . . . . . . .   5
   4.  Inter-Interface Automatic Policy Mapping  . . . . . . . . . .   6
   5.  Security Audit System . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  13
   Appendix B.  Contributors . . . . . . . . . . . . . . . . . . . .  13
   Appendix C.  Changes from draft-jeong-i2nsf-security-management-
                automation-00  . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   Interface to Network Security Functions (I2NSF) defines a framework
   and interfaces for interacting with Network Security Functions (NSFs)
   [RFC8192][RFC8329].  Note that an NSF is defined as software that
   provides a set of security-related services, such as (i) detecting
   unwanted activity, (ii) blocking or mitigating the effect of such
   unwanted activity in order to fulfill service requirements, and (iii)
   supporting communication stream integrity and confidentiality
   [RFC8329].  The NSF can be implemented as a Virtual Network Function
   (VNF) in a Network Functions Virtualization (NFV) environment
   [ETSI-NFV][I-D.ietf-i2nsf-applicability].

   This document describes an extension of the framework of Interface to
   Network Security Functions (I2NSF) for Security Management Automation
   (SMA) in cloud-based security services.  The security management
   automation includes a security polity translation and a feedback-
   based security service enforcement.  This document specifies an
   augmented architecture of the I2NSF framework for the SMA services
   with a new system component and a new interface.



Jeong, et al.            Expires August 26, 2021                [Page 2]


Internet-Draft    I2NSF Security Management Automation     February 2021


   For reliable management for networked security services, this
   document proposes a network management and verification facility
   using a decentralized audit system (e.g., blockchain [Bitcoin]).
   This audit system can facilitate the non-repudiation of configuration
   commands and monitoring data generated in the I2NSF framework.

   Therefore, with the security service automation, this document
   facilitates the foundation of Intent-Based Networking (IBN) for
   intelligent security services
   [I-D.irtf-nmrg-ibn-concepts-definitions].

2.  Terminology

   This document uses the terminology described in [RFC8329] and
   [I-D.ietf-i2nsf-applicability].  In addition, the following terms are
   defined below:

   o  Security Management Automation (SMA): It means that a high-level
      security policy from a user (or administrator) is well-enforced in
      a target I2NSF system.  The high-level security policy can be
      translated into the corresponding low-level security policy by a
      security policy translator and dispatched to appropriate NSFs.
      Through the monitoring of the NSFs, the activity and performace of
      the NSFs is monitored and analyzed.  If needed, the security rules
      of the low-level security policy are augmented or new security
      rules are generated and configured to appropriate NSFs.

   o  Security Policy Translation (SPT): It means that a high-level
      security policy is translated to a low-level security policy that
      can be understood and configured by an NSF for a specific security
      service, such as firewall, web filter, deep packet inspection,
      DDoS-attack mitigation, and anti-virus.

   o  Feedback-Based Security Management (FSM): It means that a security
      service is evolved by updating a security policy (having security
      rules) and adding new security rules for detected security attacks
      by processing and analzing the monitoring data of NSFs.














Jeong, et al.            Expires August 26, 2021                [Page 3]


Internet-Draft    I2NSF Security Management Automation     February 2021


      +------------+
      | I2NSF User |
      +------------+
             ^
             | Consumer-Facing Interface
             v
   +-------------------+     Registration     +-----------------------+
   |Security Controller|<-------------------->|Developer's Mgmt System|
   +-------------------+      Interface       +-----------------------+
             ^      ^
             |      |
             |      |  Application Interface  +-----------------------+
             |      +------------------------>|    I2NSF Analyzer     |
             |                                +-----------------------+
             | NSF-Facing Interface              ^       ^       ^
             |                                   |       |       |
             |                                   |       |       |
             |    +------------------------------+       |       |
             |    |              +-----------------------+       |
             |    |              |   Monitoring Interface        |
             v    v              v                               v
      +----------------+ +---------------+   +-----------------------+
      |      NSF-1     |-|     NSF-2     |...|         NSF-n         |
      |   (Firewall)   | | (Web Filter)  |   |(DDoS-Attack Mitigator)|
      +----------------+ +---------------+   +-----------------------+

       Figure 1: I2NSF Framework for Security Management Automation

3.  I2NSF Framework for Security Management Automation

   This section summarizes the I2NSF framework as defined in [RFC8329].
   As shown in Figure 1, an I2NSF User can use security functions by
   delivering high-level security policies, which specify security
   requirements that the I2NSF user wants to enforce, to the Security
   Controller via the Consumer-Facing Interface (CFI)
   [I-D.ietf-i2nsf-consumer-facing-interface-dm].

3.1.  Components with I2NSF Framework for Security Management Automation

   The following are the system components for the SMA-based I2NSF
   framework.

   o  I2NSF User: An entity that delivers a high-level security policy
      to Security Controller.

   o  Security Controller: An entity that controls and manages other
      system components in the I2NSF framework.  It translates a high-
      level security policy into the corresponding low-level security



Jeong, et al.            Expires August 26, 2021                [Page 4]


Internet-Draft    I2NSF Security Management Automation     February 2021


      policy and selects appropriate NSFs to execute the security rules
      of the low-level security policy.

   o  Developer's Management System (DMS): An entity that provides an
      image of of a virtualized NSF for a security service to the I2NSF
      framework, and registers the capability and access information of
      an NSF with Security Controller.

   o  Network Security Function (NSF): An entity that is a Virtual
      Network Function (VNF) for a specific network security service
      such as firewall, web filter, deep packet inspection, DDoS-attack
      mitigation, and anti-virus.

   o  I2NSF Analyzer: An entity that collects monitoring data from NSFs
      and analyzes such data for checking the activity and performance
      of the NSFs using machine learning techniques (e.g., Deep Learning
      [Deep-Learning]).  If there is a suspicious attack activity for
      the target network or NSF, I2NSF Analyzer delivers a report of the
      augmentation or generation of secuity rules to Security
      Controller.

   For SMA-based security services with Feedback-Based Security
   Management (FSM), I2NSF Analyzer as a new I2NSF component is required
   for the legacy I2NSF framework [RFC8329] to collect monitoring data
   of NSFs and analyzing them.

3.2.  Interfaces with SMA-Based I2NSF Framework

   The following are the interfaces for the SMA-based I2NSF framework.
   Note that the interfaces are modeled with YANG [RFC6020] and security
   policies are delivered through either RESTCONF [RFC8040] or NETCONF
   [RFC6241].

   o  Consumer-Facing Interface: An interface between I2NSF User and
      Security Controller for the delivery of a high-level security
      policy [I-D.ietf-i2nsf-consumer-facing-interface-dm].

   o  NSF-Facing Interface: An interface between Security Controller and
      an NSF for the delivery of a low-level security policy
      [I-D.ietf-i2nsf-nsf-facing-interface-dm].

   o  Registration Interface: An interface between a DMS and Security
      Controller for the registration of an NSF's capability and access
      information with Secutiy Controller or the query of an NSF for a
      required low-level security policy
      [I-D.ietf-i2nsf-registration-interface-dm].





Jeong, et al.            Expires August 26, 2021                [Page 5]


Internet-Draft    I2NSF Security Management Automation     February 2021


   o  Monitoring Interface: An interface between an NSF and I2NSF
      Analyzer for collecting monitoring data from an NSF to check the
      activity and performance of an NSF for a possible malicious
      traffic [I-D.ietf-i2nsf-nsf-monitoring-data-model].

   o  Application Interface: An interface between I2NSF Analyzer and
      Security Controller for the delivery of a report of the
      augmentation or generation of secuity rules to Security
      Controller, which lets Security Controller apply the report for
      security rules to its security policy management.

   For SMA-based security services with FSM, Application Interface as a
   new I2NSF interface is required for the legacy I2NSF framework
   [RFC8329] to deliver a report of the augmentation or generation of
   secuity rules to Security Controller on the basis of the analyzed
   monitoring data of NSFs.

4.  Inter-Interface Automatic Policy Mapping

   To facilitate Security Policy Translation (SPT), Security Controller
   needs to have a security policy translator that performs the
   translation of a high-level security policy into the corresponding
   low-level security policy.  For the automatic SPT services, the I2NSF
   framework needs to bridge a high-level YANG data model and a low-
   level YANG data model in an automatic manner [I-D.ietf-i2nsf-applicab
   ility][I-D.yang-i2nsf-security-policy-translation].  Note that a
   high-level YANG data model is for the I2NSF Consumer-Facing Interface
   [I-D.ietf-i2nsf-consumer-facing-interface-dm], and a low-level YANG
   data model is for the I2NSF NSF-Facing Interface
   [I-D.ietf-i2nsf-nsf-facing-interface-dm].

   Figure 2 shows automatic mapping of high-level and low-level data
   models.  Automatic Data Model Mapper takes a high-level YANG data
   module for the Consumer-Facing Inteface and a low-level YANG data
   module for the NSF-Facing Interface.  It then constructs a mapping
   table associating the data attributes (or variables) of the high-
   level YANG data module with the corresponding data attributes (or
   variables) of the low-level YANG data module.  Also, it generates a
   set of production rules of the grammar for the construction of an XML
   file of low-level security policy rules.

   Figure 3 shows high-to-low security policy translation.  A security
   policy translator is a component of Security Controller.  The
   translator consists of three components such as Policy Data
   Extractor, Policy Attribute Mapper, and Policy Constructor.






Jeong, et al.            Expires August 26, 2021                [Page 6]


Internet-Draft    I2NSF Security Management Automation     February 2021


          High-level YANG Data Module   Low-level YANG Data Model
                      |                              |
                      V                              V
            +---------+------------------------------+---------+
            |           Automatic Data Model Mapper            |
            +------------------------+-------------------------+
                                     |
                                     V
                          Data Model Mapping Table

    Figure 2: Automatic Mapping of High-level and Low-level Data Models








































Jeong, et al.            Expires August 26, 2021                [Page 7]


Internet-Draft    I2NSF Security Management Automation     February 2021


            +--------------------------------------------------+
            |                                                  |
            |                    I2NSF User                    |
            |                                                  |
            +------------------------+-------------------------+
                                     | Consumer-Facing Interface
                                     |
                         High-level Security Policy
            Security                 |
            Controller               V
            +------------------------+-------------------------+
            |  Security Policy       |                         |
            |  Translator            V                         |
            |  +---------------------+----------------------+  |
            |  |                                            |  |
            |  |         +-------------------------+        |  |
            |  |         |  Policy Data Extractor  |        |  |
            |  |         +-------------------------+        |  |
            |  |                                            |  |
            |  |         +-------------------------+        |  |
            |  |         | Policy Attribute Mapper |        |  |
            |  |         +-------------------------+        |  |
            |  |                                            |  |
            |  |         +-------------------------+        |  |
            |  |         |    Policy Constructor   |        |  |
            |  |         +-------------------------+        |  |
            |  |                                            |  |
            |  +---------------------+----------------------+  |
            |                        |                         |
            |                        V                         |
            +------------------------+-------------------------+
                                     |  NSF-Facing Interface
                                     |
                          Low-level Security Policy
                                     |
                                     V
            +------------------------+-------------------------+
            |                                                  |
            |                      NSF(s)                      |
            |                                                  |
            +--------------------------------------------------+

             Figure 3: High-to-Low Security Policy Translation

   Policy Data Extractor extracts attributes related to a security
   policy from a high-level security policy XML file that is delivered
   from an I2NSF User to a Security Controller
   [I-D.ietf-i2nsf-consumer-facing-interface-dm].



Jeong, et al.            Expires August 26, 2021                [Page 8]


Internet-Draft    I2NSF Security Management Automation     February 2021


   Policy Attribute Mapper maps the attributes and their values of a
   high-level security policy to the corresponding attributes and their
   values of a low-level security policy.

   Policy Constructor constructs a low-level security policy XML file
   that is delivered from the Security Controller to an appropriate NSF
   [I-D.ietf-i2nsf-nsf-facing-interface-dm].

5.  Security Audit System

   The I2NSF framework is weak to both an inside attack and a supply
   chain attack since it trusts in NSFs provided by Developer's
   Management System (DMS) and assumes that NSFs work for their security
   services appropriately.  [I-D.ietf-i2nsf-applicability].

   To detect the malicious activity of either an insider attacker with
   its DMS or a supply chain attacker with its compromised DMS, a
   security audit system is required for the I2NSF framework.  For this
   audit service in the I2NSF framework, a decentralized security audit
   system (e.g., blockchain [Bitcoin]) is required.  This audit system
   can facilitate the non-repudiation of configuration commands and
   monitoring data generated in the I2NSF framework.

   A security audit system has four main objectives such as follows:

   o  To check the existence of a security policy, a management system
      and its procedures;

   o  To identify and understand the existing vulnerabilities and risks
      of a supply chain attacker;

   o  To review existing security controls on operational,
      administrative and managerial issues;

   o  To provide recommendations and corrective actions for further
      improvement.















Jeong, et al.            Expires August 26, 2021                [Page 9]


Internet-Draft    I2NSF Security Management Automation     February 2021


+-----------------------------+                      +----------------+
|         I2NSF User          |                      |Developer's Mgmt|
|                             +--------------+       |     System     |
+--------------+--------------+              |       +--------+-------+
               | Consumer-Facing Interface   |                |
               |                             |                |
   High-level Security Policy                |                |
               |                             |                |
               |                             |                |
               V                             |                V
+--------------+--------------+              |      +---------+--------+
|                             |              V      |     Security     |
|     Security Controller     +------------->+----->|       Audit      |
|                             |              ^      |      System      |
+--------------+--------------+              |      |(e.g., Blockchain)|
               |  NSF-Facing Interface       |      +---------+--------+
               |                             |                ^
   Low-level Security Policy                 |                |
               |                             |                |
               V                             |                |
+--------------+--------------+              |       +--------+-------+
|            NSF(s)           |              |       | I2NSF Analyzer |
|                             +--------------+       |                |
+-----------------------------+                      +----------------+

          Figure 4: Activity Auditing with Security Audit System

   Figure 4 shows activity auditing with a security audit system in the
   I2NSF framework.  All the components in the I2NSF framwork report its
   activities (such as configuration commands and monitoring data) to
   Security Audit System (e.g., Blockchain) as transactions.  The
   security audit system can analyze the reported activities from the
   I2NSF components to detect malicious activities such as supply chain
   attack.

   In order to determine a minimum set of controls required to reduce
   the risks from a supply chain attacker, the security audit system
   should analyze the activities of all the components in the I2NSF
   framework periodically, evaluate possible risks, and take an action
   to such risks since vulnerabilities and threats may change in
   different environments over time.

6.  Security Considerations

   The same security considerations for the I2NSF framework [RFC8329]
   are applicable to this document.





Jeong, et al.            Expires August 26, 2021               [Page 10]


Internet-Draft    I2NSF Security Management Automation     February 2021


7.  IANA Considerations

   This document does not require any IANA actions.

8.  References

8.1.  Normative References

   [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", draft-
              ietf-i2nsf-consumer-facing-interface-dm-12 (work in
              progress), September 2020.

   [I-D.ietf-i2nsf-nsf-facing-interface-dm]
              Kim, J., Jeong, J., J., J., PARK, P., Hares, S., and Q.
              Lin, "I2NSF Network Security Function-Facing Interface
              YANG Data Model", draft-ietf-i2nsf-nsf-facing-interface-
              dm-10 (work in progress), August 2020.

   [I-D.ietf-i2nsf-nsf-monitoring-data-model]
              Jeong, J., Lingga, P., Hares, S., Xia, L., and H.
              Birkholz, "I2NSF NSF Monitoring YANG Data Model", draft-
              ietf-i2nsf-nsf-monitoring-data-model-04 (work in
              progress), September 2020.

   [I-D.ietf-i2nsf-registration-interface-dm]
              Hyun, S., Jeong, J., Roh, T., Wi, S., J., J., and P. PARK,
              "I2NSF Registration Interface YANG Data Model", draft-
              ietf-i2nsf-registration-interface-dm-09 (work in
              progress), August 2020.

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

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [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>.






Jeong, et al.            Expires August 26, 2021               [Page 11]


Internet-Draft    I2NSF Security Management Automation     February 2021


   [RFC8192]  Hares, S., Lopez, D., Zarny, M., Jacquenet, C., Kumar, R.,
              and J. Jeong, "Interface to Network Security Functions
              (I2NSF): Problem Statement and Use Cases", RFC 8192,
              DOI 10.17487/RFC8192, July 2017,
              <https://www.rfc-editor.org/info/rfc8192>.

   [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>.

8.2.  Informative References

   [Bitcoin]  Nakamoto, S., "Bitcoin: A Peer-to-Peer Electronic Cash
              System", URL: https://bitcoin.org/bitcoin.pdf, May 2009.

   [Deep-Learning]
              Goodfellow, I., Bengio, Y., and A. Courville, "Deep
              Learning", Publisher: The MIT Press,
              URL: https://www.deeplearningbook.org/, November 2016.

   [ETSI-NFV]
              "Network Functions Virtualisation (NFV); Architectural
              Framework", Available:
              https://www.etsi.org/deliver/etsi_gs/
              nfv/001_099/002/01.01.01_60/gs_nfv002v010101p.pdf, October
              2013.

   [I-D.ietf-i2nsf-applicability]
              Jeong, J., Hyun, S., Ahn, T., Hares, S., and D. Lopez,
              "Applicability of Interfaces to Network Security Functions
              to Network-Based Security Services", draft-ietf-i2nsf-
              applicability-18 (work in progress), September 2019.

   [I-D.irtf-nmrg-ibn-concepts-definitions]
              Clemm, A., Ciavaglia, L., Granville, L., and J. Tantsura,
              "Intent-Based Networking - Concepts and Definitions",
              draft-irtf-nmrg-ibn-concepts-definitions-02 (work in
              progress), September 2020.

   [I-D.yang-i2nsf-security-policy-translation]
              Jeong, J., Yang, J., Chung, C., and J. Kim, "Security
              Policy Translation in Interface to Network Security
              Functions", draft-yang-i2nsf-security-policy-
              translation-07 (work in progress), November 2020.






Jeong, et al.            Expires August 26, 2021               [Page 12]


Internet-Draft    I2NSF Security Management Automation     February 2021


Appendix A.  Acknowledgments

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

Appendix B.  Contributors

   This document is made by the group effort of I2NSF working group.
   Many people actively contributed to this document, such as Linda
   Dunbar, Yoav Nir, and Qin Wu.  The authors sincerely appreciate their
   contributions.

   The following are co-authors of this document:

   Yunchul Choi
   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 C.  Changes from draft-jeong-i2nsf-security-management-
             automation-00

   The following changes are made from draft-jeong-i2nsf-security-
   management-automation-00:

   o  In Section 5, four main objectives of a security audit system are
      explained.




Jeong, et al.            Expires August 26, 2021               [Page 13]


Internet-Draft    I2NSF Security Management Automation     February 2021


   o  In Section 5, the architecture and auditing procedure of a
      security audit system are described along with Figure 4.

Authors' Addresses

   Jaehoon (Paul) Jeong
   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
   Fax:   +82 31 290 7996
   EMail: pauljeong@skku.edu
   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


   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














Jeong, et al.            Expires August 26, 2021               [Page 14]