Network
I2NSF Working Group                                             J. Jeong
Internet-Draft                                                   S. Hyun                                   Sungkyunkwan University
Intended status: Informational                   Sungkyunkwan University                                   S. Hyun
Expires: September 6, 2018 January 3, 2019                               Chosun University
                                                                  T. Ahn
                                                           Korea Telecom
                                                                S. Hares
                                                                  Huawei
                                                                D. Lopez
                                                          Telefonica I+D
                                                           March 5,
                                                            July 2, 2018

 Applicability of Interfaces to Network Security Functions to Network-
                        Based Security Services
                   draft-ietf-i2nsf-applicability-02
                   draft-ietf-i2nsf-applicability-03

Abstract

   This document describes the applicability of Interface to Network
   Security Functions (I2NSF) to network-based security services in
   Network Functions Virtualization (NFV) environments, such as
   firewall, deep packet inspection, or attack mitigation engines.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 6, 2018. January 3, 2019.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  I2NSF Framework . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Time-dependent Web Access Control Service . . . . . . . .   5
   4.  I2NSF Framework with SDN SFC  . . . . . . . . . . . . . . . . . .   7
     4.1.
   5.  I2NSF Framework with SDN  . . . . . . . . . . . . . . . . . .   9
     5.1.  Firewall: Centralized Firewall System . . . . . . . . . .  10
     4.2.  11
     5.2.  Deep Packet Inspection: Centralized VoIP/VoLTE Security
           System  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     4.3.  12
     5.3.  Attack Mitigation: Centralized DDoS-attack Mitigation
           System  . . . . . . . . . . . . . . . . . . . . . . . . .  13
   5.  14
   6.  I2NSF Framework with NFV  . . . . . . . . . . . . . . . . . .  16
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   6.  18
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  15
   7.  18
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  15
   8.  18
   10. Informative References  . . . . . . . . . . . . . . . . . . .  15  19
   Appendix A.  Changes from draft-ietf-i2nsf-applicability-01 draft-ietf-i2nsf-applicability-02 . . .  19  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19  22

1.  Introduction

   Interface to Network Security Functions (I2NSF) defined a framework
   and interfaces for interacting with Network Security Functions
   (NSFs).  The I2NSF framework allows heterogeneous NSFs developed by
   different security solution vendors to be used in the NFV environment
   by utilizing the capabilities of such products and the virtualization
   of security functions in the NFV platform.  In the I2NSF framework,
   each NSF initially registers the profile of its own capabilities into
   the system in order for themselves to be available in the system.  In
   addition, the Security Controller registers itself to the I2NSF user
   so that the user can request security services to the Security
   Controller.

   This document describes the applicability of I2NSF framework to
   network-based security services with a use case of time-dependent web
   access control.  This document also describes integrating I2NSF
   framework with Software-Defined Networking (SDN) technology for
   efficient security services and use cases, such as firewall

   [opsawg-firewalls], Deep Packet Inspection (DPI), and Distributed
   Denial of Service (DDoS) attack mitigation.  We implemented the I2NSF
   framework based on SDN for these use cases, and the implementation
   successfully verified the effectiveness of the I2NSF framework.

2.  Terminology

   This document uses the terminology described in [RFC7149],
   [ITU-T.Y.3300], [ONF-OpenFlow], [ONF-SDN-Architecture],
   [ITU-T.X.1252], [ITU-T.X.800], [RFC8329], [i2nsf-terminology],
   [consumer-facing-inf-im], [consumer-facing-inf-dm],
   [i2nsf-nsf-cap-im], [nsf-facing-inf-dm], [registration-inf-im],
   [registration-inf-dm], and [nsf-triggered-steering].  In addition,
   the following terms are defined below:

   o  Software-Defined Networking (SDN): A set of techniques that
      enables to directly program, orchestrate, control, and manage
      network resources, which facilitates the design, delivery and
      operation of network services in a dynamic and scalable manner
      [ITU-T.Y.3300].

   o  Firewall: A service function at the junction of two network
      segments that inspects every packet that attempts to cross the
      boundary.  It also rejects any packet that does not satisfy
      certain criteria for, for example, disallowed port numbers or IP
      addresses.

   o  Centralized Firewall System: A centralized firewall that can
      establish and distribute policy rules into network resources for
      efficient firewall management.  These rules can be managed
      dynamically by a centralized server for firewall.  SDN can work as
      a network-based firewall system through a standard interface
      between an SDN switch and a firewall function as a vitual network
      function (VNF).

   o  Centralized VoIP Security System: A centralized security system
      that handles the security functions required for VoIP and VoLTE
      services.  SDN can work as a network-based security system through
      a standard interface between an SDN switch and a VoIP/VoLTE
      security function as a VNF.

   o  Centralized DDoS-attack Mitigation System: A centralized mitigator
      that can establish and distribute access control policy rules into
      network resources for efficient DDoS-attack mitigation.  These
      rules can be managed dynamically by a centralized server for DDoS-
      attack mitigation.  The SDN controller and switches can
      cooperatively work as a network-based firewall system through a
      standard interface between an SDN switch and a firewall function
      as a VNF running in the SDN controller.

3.  I2NSF Framework

   This section describes an I2NSF framework and its use case.  Figure 1
   shows an I2NSF framework [RFC8329] to support network-based security
   services.  As shown in Figure 1, I2NSF User can use security
   functions by delivering high-level security policies, which specify
   security requirements the I2NSF user wants to enforce, to the
   Security Controller via the Consumer-Facing Interface
   [consumer-facing-inf-im][consumer-facing-inf-dm].

   The Security Controller receives and analyzes the high-level security
   policies from an I2NSF User, and identifies what types of security
   capabilities are required to meet these high-level security policies.
   The Security Controller then identifies NSFs that have the required
   security capabilities, and generates low-level security policies for
   each of the NSFs so that the high-level security policies are
   eventually enforced by those NSFs.  Finally, the Security Controller
   sends the generated low-level security policies to the NSFs
   [i2nsf-nsf-cap-im][nsf-facing-inf-dm].

   The Security Controller requests NSFs to perform low-level security
   services via the NSF-Facing Interface.  The NSFs are enabled as
   Virtual Network Functions (VNFs) on top of virtual machines through
   Network Functions Virtualization (NFV) [ETSI-NFV].  In addition, the
   Security Controller uses the I2NSF Registration Interface
   [registration-inf-im][registration-inf-dm] to communicate with
   Developer's Management System (called Developer's Mgmt System) for
   registering (or deregistering) the developer's NSFs into (or from)
   the NFV system using the I2NSF framework.

   The Consumer-Facing Interface between an I2NSF User and the Security
   Controller can be implemented using, for example, RESTCONF [RFC8040].
   Data models specified by YANG [RFC6020] describe high-level security
   policies to be specified by an I2NSF User.  The data model defined in
   [consumer-facing-inf-dm] can be used for the I2NSF Consumer-Facing
   Interface.

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

                         Figure 1: I2NSF Framework

   The NSF-Facing Interface between Security Controller and NSFs can be
   implemented using NETCONF [RFC6241].  YANG data models describe low-
   level security policies for the sake of NSFs, which are translated
   from the high-level security policies by the Security Controller.
   The data model defined in [nsf-facing-inf-dm] can be used for the
   I2NSF NSF-Facing Interface.

   The Registration Interface between the Security Controller and the
   Developer's Mgmt System can be implemented by RESTCONF [RFC8040].
   The data model defined in [registration-inf-dm] can be used for the
   I2NSF Registration Interface.

   Also, the I2NSF framework can enforce multiple chained NSFs for the
   low-level security policies by means of service function chaining
   (SFC) techniques for the I2NSF architecture described in
   [nsf-triggered-steering].

   The following describes a security service scenario using the I2NSF
   framework.

3.1.  Time-dependent Web Access Control Service

   This service scenario assumes that an enterprise network
   administrator wants to control the staff members' access to Facebook
   during business hours.  The following is an example high-level
   security policy rule that the administrator requests: Block the staff
   members' access to Facebook from 9 am to 6 pm.  The administrator
   sends this high-level security policy to the security controller,
   then the security controller identifies required secuity
   capabilities, e.g., IP address and port number inspection
   capabilities and URL inspection capability.  In this scenario, it is
   assumed that the IP address and port number inspection capabilities
   are required to check whether a received packet is an HTTP packet
   from a staff member.  The URL inspection capability is required to
   check whether the target URL of a received packet is facebook.com or
   not.

   The Security Controller maintains the security capabilities of each
   NSF running in the I2NSF system, which have been reported by the
   Developer's Management System via the Registation interface.  Based
   on this information, the Security Controller identifies NSFs that can
   perform the IP address and port number inspection and URL inspection.
   In this scenario, it is assumed that an NSF of firewall has the IP
   address and port number inspection capabilities and an NSF of web
   filter has URL inspection capability.

   The Security Controller generates low-level security rules for the
   NSFs to perform IP address and port number inspection, URL
   inspection, and time checking.  Specifically, the Security Controller
   may interoperate with an access control server in the enterprise
   network in order to retrieve the information (e.g., IP address in
   use, company ID, identifier (ID), and role) of each employee that is
   currently using the network.  Based on the retrieved information, the
   Security Controller generates low-level security rules to check
   whether the source IP address of a received packet matches any one
   being used by a staff member.  In addition, the low-level security
   rules should be able to determine that a received packet is of HTTP
   protocol.  The low-level security rules for web filter checks that
   the target URL field of a received packet is equal to facebook.com.
   Finally, the Security Controller sends the low-level security rules
   of the IP address and port number inspection to the NSF of firewall
   and the low-level rules for URL inspection to the NSF of web filter.

   The following describes how the time-dependent web access control
   service is enforced by the NSFs of firewall and web filter.

   1.  A staff member tries to access Fackbook.com during business
       hours, e.g., 10 am.

   2.  The packet is forwarded from the staff member's device to the
       firewall, and the firewall checks the source IP address and port
       number.  Now the firewall identifies the received packet is an
       HTTP packet from the staff member.

   3.  The firewall triggers the web filter to further inspect the
       packet, and the packet is forwarded from the firewall to the web
       filter.  Service Function Chaining (SFC) technology can be
       utilized to support such packet forwarding in the I2NSF framework
       [nsf-triggered-steering].

   4.  The web filter checks the target URL field of the received
       packet, and realizes the packet is toward Facebook.com.  The web
       filter then checks that the current time is in business hours.
       If so, the web filter drops the packet, and consequently the
       staff member's access to Facebook during business hours is
       blocked.

4.  I2NSF Framework with SDN

   This section describes an I2NSF framework with SDN for SFC

   In the I2NSF
   applicability architecture, an NSF can trigger an advanced security
   action (e.g., DPI and use cases, such as firewall, deep DDoS attack mitigation) on a packet
   inspection, and DDoS-attack mitigation functions.  SDN enables some based on
   the result of its own security inspection of the packet.  For
   example, a firewall triggers further inspection of a suspicious
   packet filtering rules with DPI.  For this advanced security action to be enforced in fulfilled,
   the network switches by
   controlling their suspicious packet forwarding rules.  By taking advantage of
   this capability of SDN, it is possible should be forwarded from the current NSF to optimize the process of
   successor NSF.  Service Function Chaining (SFC) [RFC7665] is a
   technology that enables this advanced security action by steering a
   packet with multiple service enforcement in functions (e.g., NSFs), and this
   technology can be utilized by the I2NSF system.

   Figure 2 shows an I2NSF framework [RFC8329] with SDN networks architecture to support network-based security services.  In this system, the
   enforcement of
   advanced security policy rules is divided into the SDN switches action.

   SFC generally requires classifiers and NSFs.  Especially, SDN switches enforce simple service function forwarders
   (SFFs); classifiers are responsible for determining which service
   function path (SFP) (i.e., an ordered sequence of service functions)
   a given packet filtering
   rules that can be translated into their packet forwarding should pass through, according to pre-configured
   classification rules,
   whereas NSFs enforce NSF-related security rules requiring and SFFs perform forwarding the
   security capabilities of given packet to
   the NSFs.  For this purpose, next service function (e.g., NSF) on the Security
   Controller instructs SFP of the Switch Controller via NSF-Facing Interface
   so that SDN switches can perform packet by
   referring to their forwarding tables.  In the required security services I2NSF architecture with
   flow tables under the supervision of
   SFC, the Switch Controller (i.e., SDN
   Controller).

   As an example, let us consider two different types of security rules:
   Rule A is a simple packet fltering rule that checks only the IP
   address and port number controller can take responsibilities of a given packet, whereas rule B is a time-
   consuming packet inspection rule generating
   classification rules for classifiers and forwarding tables for SFFs.
   In particular, by analyzing whether an attached
   file being transmitted over a flow of packets contains malware.  Rule
   A high-level security policies from I2NSF
   users, the security controller can be translated into packet forwarding construct SFPs that are required
   to meet the high-level security policies, generates classification
   rules of SDN switches and
   thus be enforced by the switches.  In contrast, rule B cannot be
   enforced by switches, but it can be enforced by NSFs SFPs, and then configures classifiers with anti-
   malware capability.  Specifically, a flow of the
   classification rules so that relevant traffic packets is forwarded to
   and reassembled by an NSF to reconstruct can follow the attached file stored in
   SFPs.  Also, based on the flow global view of packets.  The NSF then analyzes the file to check instances available in
   the
   existence of malware.  If system, the file contains malware, security controller can construct forwarding tables
   required for SFFs to forward a given packet to the next NSF drops over the packets.

   In an I2NSF framework with SDN, the Security Controller can analyze
   given security policy rules and automatically determine which of the
   given security policy rules should be enforced by SDN switches and
   which should be enforced by NSFs.  If some of the given rules
   requires security capabilities that can be provided by SDN switches,
   then the Security Controller instructs the Switch Controller via NSF-
   Facing Interface so that SDN switches can enforce those security
   policy rules with flow tables under the supervision of the Switch
   Controller (i.e., SDN Controller).  Or if some rules require security
   capabilities that can be provided by not SDN switches but NSFs, then
   the Security Controller instructs relevant NSFs to enforce those
   rules.

      +------------+
      |
   SFP.

      +------------+
      | I2NSF User |
      +------------+
             ^
             | Consumer-Facing Interface
             v
   +-------------------+     Registration     +-----------------------+
   |Security Controller|<-------------------->|Developer's Mgmt System|
   +-------------------+       Interface      +-----------------------+
         ^       ^
         |       | NSF-Facing Interface
         |     v       |-------------------------
         | +----------------+ +---------------+   +-----------------------+                                |
   +-+-+-v-+-+-+-+-+-+             +------v-------+
   |      NSF-1     |-|     NSF-2     |...|         NSF-n  +-----------+  |      ------>|     NSF-1    |
   |   (Firewall)  |Classifier |  |     (DPI)      |   |(DDoS-Attack Mitigator)|      | +----------------+ +---------------+   +-----------------------+  (Firewall)  |         ^
   |  +-----------+  |      |         v      +--------------+
   |    +--------+     +-----+     |<-----|      +--------------+
   |     | SFF |     |    +--------+
      |         ^
      |         |
      |         V                                     SDN Network
   +--|----------------------------------------------------------------+
   |  V NSF-Facing Interface                                           |
   |  +-----------------+                                              |
   |  |Switch Controller|                                              |
   |  +-----------------+                                              |
   |           ^      |----->|     NSF-2    |
   |     +-----+     | SDN Southbound Interface      |      |           v     (DPI)    |
   +-+-+-+-+-+-+-+-+-+      |      +--------+ +--------+ +--------+      +--------+      +--------------+
                            |             .
                            |      |Switch 1|-|Switch 2|-|Switch 3|......|Switch m|             .
                            |             .
                            |      +--------+ +--------+ +--------+      +--------+      +-----------------------+
                            ------>|        NSF-n          |
   +-------------------------------------------------------------------+
                                   |(DDoS-Attack Mitigator)|
                                   +-----------------------+

                   Figure 2: An I2NSF Framework with SDN Network

   The following subsections introduce three use cases for cloud-based SFC

   To trigger an advanced security services: (i) firewall system, (ii) deep packet inspection
   system, and (iii) attack mitigation system.  [RFC8192]

4.1.  Firewall: Centralized Firewall System

   A centralized network firewall can manage each network resource and
   firewall rules can be managed flexibly by action in the I2NSF architecture, the
   current NSF appends a centralized server for
   firewall (called Firewall).  The centralized network firewall
   controls each switch metadata describing the security capability
   required for the network resource management advanced action to the suspicious packet and sends
   the
   firewall rules can be added or deleted dynamically.

   The procedure of firewall operations in this system is as follows:

   1.  A switch forwards an unknown flow's packet to one of the Switch
       Controllers.

   2.  The Switch Controller forwards classifier.  Based on the unknown flow's packet to metadata information, the
   classifier searches an
       appropriate security service application, such as SFP which includes an NSF with the Firewall.

   3.  The Firewall analyzes, typically, required
   security capability, changes the headers SFP-related information (e.g.,
   service path identifier and contents service index [RFC8300]) of the
       packet.

   4.  If the Firewall regards the packet as a malicious one
   with a
       suspicious pattern, it reports the malicious new SFP that has been found, and then forwards the packet to
   the Switch
       Controller.

   5.  The Switch Controller installs new rules (e.g., drop packets with SFF.  When receiving the suspicious pattern) into underlying switches.

   6.  The suspected packets are dropped by these switches.

   Existing SDN protocols can be used through standard interfaces
   between packet, the firewall application and switches
   [RFC7149][ITU-T.Y.3300][ONF-OpenFlow] [ONF-SDN-Architecture].

   Legacy firewalls have some challenges SFF checks the SFP-related
   information such as the expensive cost,
   performance, management of access control, establishment of policy, service path identifier and packet-based access mechanism.  The proposed framework can
   resolve service index
   contained in the challenges through packet and forwards the above centralized firewall system
   based packet to the next NSF on SDN as follows:

   o  Cost: The cost
   the SFP of adding firewalls the packet, according to network resources its forwarding table.

5.  I2NSF Framework with SDN

   This section describes an I2NSF framework with SDN for I2NSF
   applicability and use cases, such as
      routers, gateways, firewall, deep packet
   inspection, and switches is substantial due DDoS-attack mitigation functions.  SDN enables some
   packet filtering rules to be enforced in the reason
      that we need to add firewall on each network resource.  To solve
      this, each network resource can be managed centrally such that a
      single firewall is manipulated switches by a centralized server.

   o  Performance: The performance
   controlling their packet forwarding rules.  By taking advantage of firewalls is often slower than the
      link speed
   this capability of network interfaces.  Every network resource for
      firewall needs to check firewall rules according SDN, it is possible to network
      conditions.  Firewalls can be adaptively deployed among network
      switches, depending on network conditions in optimize the framework.

   o  The management of access control: Since there may be hundreds process of
      network resources
   security service enforcement in a network, the dynamic management of access
      control for I2NSF system.

   Figure 3 shows an I2NSF framework [RFC8329] with SDN networks to
   support network-based security services like firewall is a challenge. services.  In this system, the framework, firewall rules can be dynamically added for new
      malware.

   o  The establishment
   enforcement of policy: Policy should be established for each
      network resource.  However, it is difficult to describe what flows
      are permitted or denied for firewall within a specific
      organization network under management.  Thus, a centralized view
      is helpful to determine security policies for such a network.

   o  Packet-based access mechanism: Packet-based access mechanism policy rules is
      not enough for firewall in practice since divided into the basic unit of access
      control is usually users or applications.  Therefore, application
      level SDN switches
   and NSFs.  Especially, SDN switches enforce simple packet filtering
   rules that can be defined and added to translated into their packet forwarding rules,
   whereas NSFs enforce NSF-related security rules requiring the firewall system
      through
   security capabilities of the NSFs.  For this purpose, the centralized server.

4.2.  Deep Packet Inspection: Centralized VoIP/VoLTE Security System

   A centralized VoIP/VoLTE security system
   Controller instructs the Switch Controller via NSF-Facing Interface
   so that SDN switches can monitor each VoIP/VoLTE perform the required security services with
   flow and manage VoIP/VoLTE tables under the supervision of the Switch Controller (i.e., SDN
   Controller).

   As an example, let us consider two different types of security rules controlled by rules:
   Rule A is a centralized
   server for VoIP/VoLTE security service called VoIP Intrusion
   Prevention System (IPS).  The VoIP/VoLTE security system controls
   each switch for simple packet fltering rule that checks only the VoIP/VoLTE call IP
   address and port number of a given packet, whereas rule B is a time-
   consuming packet inspection rule for analyzing whether an attached
   file being transmitted over a flow management of packets contains malware.  Rule
   A can be translated into packet forwarding rules of SDN switches and
   thus be enforced by manipulating the rules that can switches.  In contrast, rule B cannot be added, deleted or modified dynamically.

   A centralized VoIP/VoLTE security system
   enforced by switches, but it can cooperate be enforced by NSFs with a network
   firewall to realize VoIP/VoLTE security service. anti-
   malware capability.  Specifically, a
   network firewall performs basic security checks flow of an unknown flow's
   packet observed packets is forwarded to
   and reassembled by a switch.  If an NSF to reconstruct the network firewall detects that attached file stored in
   the packet is an unknown VoIP call flow's packet that exhibits some
   suspicious patterns, flow of packets.  The NSF then it triggers analyzes the VoIP/VoLTE security system
   for more specialized security analysis of the suspicious VoIP call
   packet.

   The procedure of VoIP/VoLTE security operations in this system is as
   follows:

   1.  A switch forwards an unknown flow's packet to the Switch
       Controller, and the Switch Controller further forwards the
       unknown flow's packet file to check the Firewall for basic security
       inspection.

   2.  The Firewall analyzes the header fields of the packet, and
       figures out that this is an unknown VoIP call flow's signal
       packet (e.g., SIP packet) of a suspicious pattern.

   3.  The Firewall triggers an appropriate security service function,
       such as VoIP IPS, for detailed security analysis
   existence of malware.  If the
       suspicious signal packet.  That is, the firewall sends the packet
       to file contains malware, the Service Function Forwarder (SFF) in NSF drops
   the packets.

   In an I2NSF framework
       [nsf-triggered-steering], as shown in Figure 2.  The SFF forwards
       the suspicious signal packet to the VoIP IPS.

   4.  The VoIP IPS analyzes with SDN, the headers Security Controller can analyze
   given security policy rules and contents automatically determine which of the signal
       packet, such as calling number
   given security policy rules should be enforced by SDN switches and session description headers
       [RFC4566].

   5.  If, for example, the VoIP IPS regards the packet as a spoofed
       packet
   which should be enforced by hackers or a scanning packet searching for VoIP/VoLTE
       devices, it drops NSFs.  If some of the packet.  In addition, given rules
   requires security capabilities that can be provided by SDN switches,
   then the VoIP IPS requests Security Controller instructs the Switch Controller to block via NSF-
   Facing Interface so that packet and SDN switches can enforce those security
   policy rules with flow tables under the subsequent
       packets that have supervision of the same call-id.

   6.  The Switch
   Controller installs new rules (e.g., drop packets)
       into underlying switches.

   7.  The illegal packets are dropped by these switches.

   Existing SDN protocols can be used through standard interfaces
   between the VoIP IPS application and switches [RFC7149][ITU-T.Y.3300]
   [ONF-OpenFlow][ONF-SDN-Architecture].

   Legacy hardware based VoIP IPS has some challenges, such as
   provisioning time, the granularity of security, expensive cost, and
   the establishment of policy.  The I2NSF framework can resolve the
   challenges through the above centralized VoIP/VoLTE security system
   based on (i.e., SDN as follows:

   o  Provisioning: The provisioning time of setting up a legacy VoIP
      IPS to network is substantial because it takes from some hours to Controller).  Or if some days.  By managing the network resources centrally, VoIP IPS
      can provide more agility in provisioning both virtual and physical
      network resources from a central location.

   o  The granularity of security: The security rules of a legacy VoIP
      IPS are compounded considering the granularity of security.  The
      proposed framework can provide more granular security by
      centralizing security control into a switch controller.  The VoIP
      IPS can effectively manage require security rules throughout the network.

   o  Cost: The cost of adding VoIP IPS to network resources, such as
      routers, gateways, and switches is substantial due to the reason
   capabilities that we need to add VoIP IPS on each network resource.  To solve
      this, each network resource can be managed centrally such that a
      single VoIP IPS is manipulated provided by a centralized server.

   o  The establishment of policy: Policy should be established for each
      network resource.  However, it not SDN switches but NSFs, then
   the Security Controller instructs relevant NSFs to enforce those
   rules.

      +------------+
      | I2NSF User |
      +------------+
             ^
             | Consumer-Facing Interface
             v
   +-------------------+     Registration     +-----------------------+
   |Security Controller|<-------------------->|Developer's Mgmt System|
   +-------------------+       Interface      +-----------------------+
      ^     ^
      |     | NSF-Facing Interface
      |     v
      | +----------------+ +---------------+   +-----------------------+
      | |      NSF-1     |-|     NSF-2     |...|         NSF-n         |
      | |   (Firewall)   | |     (DPI)     |   |(DDoS-Attack Mitigator)|
      | +----------------+ +---------------+   +-----------------------+
      |         ^
      |         |
      |         v
      |    +--------+
      |    |   SFF  |
      |    +--------+
      |         ^
      |         |
      |         V                                     SDN Network
   +--|----------------------------------------------------------------+
   |  V NSF-Facing Interface                                           |
   |  +-----------------+                                              |
   |  |Switch Controller|                                              |
   |  +-----------------+                                              |
   |           ^                                                       |
   |           | SDN Southbound Interface                              |
   |           v                                                       |
   |      +--------+ +--------+ +--------+      +--------+             |
   |      |Switch 1|-|Switch 2|-|Switch 3|......|Switch m|             |
   |      +--------+ +--------+ +--------+      +--------+             |
   +-------------------------------------------------------------------+

               Figure 3: An I2NSF Framework with SDN Network

   The following subsections introduce three use cases for cloud-based
   security services: (i) firewall system, (ii) deep packet inspection
   system, and (iii) attack mitigation system.  [RFC8192]

5.1.  Firewall: Centralized Firewall System

   A centralized network firewall can manage each network resource and
   firewall rules can be managed flexibly by a centralized server for
   firewall (called Firewall).  The centralized network firewall
   controls each switch for the network resource management and the
   firewall rules can be added or deleted dynamically.

   The procedure of firewall operations in this system is as follows:

   1.  A switch forwards an unknown flow's packet to one of the Switch
       Controllers.

   2.  The Switch Controller forwards the unknown flow's packet to an
       appropriate security service application, such as the Firewall.

   3.  The Firewall analyzes, typically, the headers and contents of the
       packet.

   4.  If the Firewall regards the packet as a malicious one with a
       suspicious pattern, it reports the malicious packet to the Switch
       Controller.

   5.  The Switch Controller installs new rules (e.g., drop packets with
       the suspicious pattern) into underlying switches.

   6.  The suspected packets are dropped by these switches.

   Existing SDN protocols can be used through standard interfaces
   between the firewall application and switches
   [RFC7149][ITU-T.Y.3300][ONF-OpenFlow] [ONF-SDN-Architecture].

   Legacy firewalls have some challenges such as the expensive cost,
   performance, management of access control, establishment of policy,
   and packet-based access mechanism.  The proposed framework can
   resolve the challenges through the above centralized firewall system
   based on SDN as follows:

   o  Cost: The cost of adding firewalls to network resources such as
      routers, gateways, and switches is substantial due to the reason
      that we need to add firewall on each network resource.  To solve
      this, each network resource can be managed centrally such that a
      single firewall is manipulated by a centralized server.

   o  Performance: The performance of firewalls is often slower than the
      link speed of network interfaces.  Every network resource for
      firewall needs to check firewall rules according to network
      conditions.  Firewalls can be adaptively deployed among network
      switches, depending on network conditions in the framework.

   o  The management of access control: Since there may be hundreds of
      network resources in a network, the dynamic management of access
      control for security services like firewall is a challenge.  In
      the framework, firewall rules can be dynamically added for new
      malware.

   o  The establishment of policy: Policy should be established for each
      network resource.  However, it is difficult to describe what flows
      are permitted or denied for firewall within a specific
      organization network under management.  Thus, a centralized view
      is helpful to determine security policies for such a network.

   o  Packet-based access mechanism: Packet-based access mechanism is
      not enough for firewall in practice since the basic unit of access
      control is usually users or applications.  Therefore, application
      level rules can be defined and added to the firewall system
      through the centralized server.

5.2.  Deep Packet Inspection: Centralized VoIP/VoLTE Security System

   A centralized VoIP/VoLTE security system can monitor each VoIP/VoLTE
   flow and manage VoIP/VoLTE security rules controlled by a centralized
   server for VoIP/VoLTE security service called VoIP Intrusion
   Prevention System (IPS).  The VoIP/VoLTE security system controls
   each switch for the VoIP/VoLTE call flow management by manipulating
   the rules that can be added, deleted or modified dynamically.

   A centralized VoIP/VoLTE security system can cooperate with a network
   firewall to realize VoIP/VoLTE security service.  Specifically, a
   network firewall performs basic security checks of an unknown flow's
   packet observed by a switch.  If the network firewall detects that
   the packet is an unknown VoIP call flow's packet that exhibits some
   suspicious patterns, then it triggers the VoIP/VoLTE security system
   for more specialized security analysis of the suspicious VoIP call
   packet.

   The procedure of VoIP/VoLTE security operations in this system is as
   follows:

   1.  A switch forwards an unknown flow's packet to the Switch
       Controller, and the Switch Controller further forwards the
       unknown flow's packet to the Firewall for basic security
       inspection.

   2.  The Firewall analyzes the header fields of the packet, and
       figures out that this is an unknown VoIP call flow's signal
       packet (e.g., SIP packet) of a suspicious pattern.

   3.  The Firewall triggers an appropriate security service function,
       such as VoIP IPS, for detailed security analysis of the
       suspicious signal packet.  That is, the firewall sends the packet
       to the Service Function Forwarder (SFF) in the I2NSF framework
       [nsf-triggered-steering], as shown in Figure 3.  The SFF forwards
       the suspicious signal packet to the VoIP IPS.

   4.  The VoIP IPS analyzes the headers and contents of the signal
       packet, such as calling number and session description headers
       [RFC4566].

   5.  If, for example, the VoIP IPS regards the packet as a spoofed
       packet by hackers or a scanning packet searching for VoIP/VoLTE
       devices, it drops the packet.  In addition, the VoIP IPS requests
       the Switch Controller to block that packet and the subsequent
       packets that have the same call-id.

   6.  The Switch Controller installs new rules (e.g., drop packets)
       into underlying switches.

   7.  The illegal packets are dropped by these switches.

   Existing SDN protocols can be used through standard interfaces
   between the VoIP IPS application and switches [RFC7149][ITU-T.Y.3300]
   [ONF-OpenFlow][ONF-SDN-Architecture].

   Legacy hardware based VoIP IPS has some challenges, such as
   provisioning time, the granularity of security, expensive cost, and
   the establishment of policy.  The I2NSF framework can resolve the
   challenges through the above centralized VoIP/VoLTE security system
   based on SDN as follows:

   o  Provisioning: The provisioning time of setting up a legacy VoIP
      IPS to network is substantial because it takes from some hours to
      some days.  By managing the network resources centrally, VoIP IPS
      can provide more agility in provisioning both virtual and physical
      network resources from a central location.

   o  The granularity of security: The security rules of a legacy VoIP
      IPS are compounded considering the granularity of security.  The
      proposed framework can provide more granular security by
      centralizing security control into a switch controller.  The VoIP
      IPS can effectively manage security rules throughout the network.

   o  Cost: The cost of adding VoIP IPS to network resources, such as
      routers, gateways, and switches is substantial due to the reason
      that we need to add VoIP IPS on each network resource.  To solve
      this, each network resource can be managed centrally such that a
      single VoIP IPS is manipulated by a centralized server.

   o  The establishment of policy: Policy should be established for each
      network resource.  However, it is difficult to describe what flows
      are permitted or denied for VoIP IPS within a specific
      organization network under management.  Thus, a centralized view
      is helpful to determine security policies for such a network.

5.3.  Attack Mitigation: Centralized DDoS-attack Mitigation System

   A centralized DDoS-attack mitigation can manage each network resource
   and manipulate rules to each switch through a centralized server for
   DDoS-attack mitigation (called DDoS-attack Mitigator).  The
   centralized DDoS-attack mitigation system defends servers against
   DDoS attacks outside private network, that is, from public network.

   Servers are categorized into stateless servers (e.g., DNS servers)
   and stateful servers (e.g., web servers).  For DDoS-attack
   mitigation, traffic flows in switches are dynamically configured by
   traffic flow forwarding path management according to the category of
   servers [AVANT-GUARD].  Such a managenent should consider the load
   balance among the switches for the defense against DDoS attacks.

   The procedure of DDoS-attack mitigation operations in this system is
   as follows:

   1.  A Switch periodically reports an inter-arrival pattern of a
       flow's packets to one of the Switch Controllers.

   2.  The Switch Controller forwards the flow's inter-arrival pattern
       to an appropriate security service application, such as DDoS-
       attack Mitigator.

   3.  The DDoS-attack Mitigator analyzes the reported pattern for the
       flow.

   4.  If the DDoS-attack Mitigator regards the pattern as a DDoS
       attack, it computes a packet dropping probability corresponding
       to suspiciousness level and reports this DDoS-attack flow to
       Switch Controller.

   5.  The Switch Controller installs new rules into switches (e.g.,
       forward packets with the suspicious inter-arrival pattern with a
       dropping probability).

   6.  The suspicious flow's packets are randomly dropped by switches
       with the dropping probability.

   For the above centralized DDoS-attack mitigation system, the existing
   SDN protocols can be used through standard interfaces between the
   DDoS-attack mitigator application and switches [RFC7149]
   [ITU-T.Y.3300][ONF-OpenFlow][ONF-SDN-Architecture].

   The centralized DDoS-attack mitigation system has challenges similar
   to the centralized firewall system.  The proposed framework can
   resolve the challenges through the above centralized DDoS-attack
   mitigation system based on SDN as follows:

   o  Cost: The cost of adding DDoS-attack mitigators to network
      resources such as routers, gateways, and switches is substantial
      due to the reason that we need to add DDoS-attack mitigator on
      each network resource.  To solve this, each network resource can
      be managed centrally such that a single DDoS-attack mitigator is
      manipulated by a centralized server.

   o  Performance: The performance of DDoS-attack mitigators is often
      slower than the link speed of network interfaces.  The checking of
      DDoS attacks may reduce the performance of the network interfaces.
      DDoS-attack mitigators can be adaptively deployed among network
      switches, depending on network conditions in the framework.

   o  The management of network resources: Since there may be hundreds
      of network resources in an administered network, the dynamic
      management of network resources for performance (e.g., load
      balancing) is a challenge for DDoS-attack mitigation.  In the
      framework, as dynamic network resource management, traffic flow
      forwarding path management can handle the load balancing of
      network switches [AVANT-GUARD].  With this management, the current
      and near-future workload can be spread among the network switches
      for DDoS-attack mitigation.  In addition, DDoS-attack mitigation
      rules can be dynamically added for new DDoS attacks.

   o  The establishment of policy: Policy should be established for each
      network resource.  However, it is difficult to describe what flows
      are permitted or denied for new DDoS-attacks (e.g., DNS reflection
      attack) within a specific organization network under management.
      Thus, a centralized view is helpful to determine security policies
      for such a network.

   So far this document has described the procedure and impact of the
   three use cases for network-based security services using the I2NSF
   framework with SDN networks.  To support these use cases in the
   proposed data-driven security service framework, YANG data models
   described in [consumer-facing-inf-dm], [nsf-facing-inf-dm], and
   [registration-inf-dm] can be used as Consumer-Facing Interface, NSF-
   Facing Interface, and Registration Interface, respectively, along
   with RESTCONF [RFC8040] and NETCONF [RFC6241].

6.  I2NSF Framework with NFV

   This section discusses the implementation of the I2NSF framework with
   Network Functions Virtualization (called NFV).

                                                  +--------------------+
   +-------------------------------------------+  | ----------------   |
   |            I2NSF User (OSS/BSS)           |  | | NFV          |   |
   +------+------------------------------------+  | | Orchestrator +-+ |
          |  Consumer-Facing Interface            | ---+------------ | |
   +------|------------------------------------+  |    |             | |
   |  ----+--------------------------------    |  |    |             | |
   |  |       Security Controller(EM)     |    |  |    |             | |
   |  ----+-------------+-------------+----    |  | ---+----------   | |
   |      |     NSF-Facing Interface  |        |(a)-| Developer's|   | |
   |  ----+----     ----+----     ----+----    |    | Mgmt System|   | |
   |  |NSF(VNF)|    |NSF(VNF)|    |NSF(VNF)|   |(b)-| (VNFM)     |   | |
   |  ----+----     ----+----     ----+----    |  | ---+----------   | |
   |      |             |             |        |  |    |             | |
   +------|-------------|-------------|--------+  |    |             | |
          |             |             |           |    |             | |
   +------+-------------+-------------+--------+  |    |             | |
   |         NFV Infrastructure (NFVI)         |  |    |             | |
   | -----------    -----------    ----------- |  |    |             | |
   | | Virtual |    | Virtual |    | Virtual | |  |    |             | |
   | | Compute |    | Storage |    | Network | |  |    |             | |
   | -----------    -----------    ----------- |  | ---+------       | |
   | +---------------------------------------+ |  | |        |       | |
   | |         Virtualization Layer          | |--|-| VIM(s) +-------- |
   | +---------------------------------------+ |  | |        |         |
   | +---------------------------------------+ |  | ----------         |
   | | -----------  -----------  ----------- | |  |                    |
   | | | Compute |  | Storage |  | Network | | |  |                    |
   | | | hardware|  | hardware|  | hardware| | |  |                    |
   | | -----------  -----------  ----------- | |  |                    |
   | |          Hardware resources           | |  |  NFV Management    |
   | +---------------------------------------+ |  | and Orchestration  |
   +-------------------------------------------+  +--------------------+
   (a) = Registration Interface
   (b) = Ve-Vnfm Interface

         Figure 4: I2NSF Framework Implementation in NFV Reference
                          Architectural Framework

   NFV is difficult to describe what flows
      are permitted or denied for VoIP IPS within a specific
      organization network under management.  Thus, a centralized view
      is helpful to determine security policies promising technology for such a network.

4.3.  Attack Mitigation: Centralized DDoS-attack Mitigation System

   A centralized DDoS-attack mitigation can manage each improving the elasticity and
   efficiency of network resource
   and manipulate rules utilization.  In NFV environments,
   NSFs can be deployed in the forms of software-based virtual instances
   rather than physical appliances.  Virtualizing NSFs makes it possible
   to each switch through a centralized server for
   DDoS-attack mitigation (called DDoS-attack Mitigator).  The
   centralized DDoS-attack mitigation system defends servers against
   DDoS attacks outside private network, that is, from public network.

   Servers are categorized into stateless servers (e.g., DNS servers) rapidly and stateful servers (e.g., web servers).  For DDoS-attack
   mitigation, traffic flows in switches are dynamically configured flexibly respond to the amount of service requests by
   traffic flow forwarding path management
   dynamically increasing or decreasing the number of NSF instances.
   Moreover, NFV technology facilitates flexibly including or excluding
   NSFs from multiple security solution vendors according to the category changes
   on security requirements.  In order to take advantages of
   servers [AVANT-GUARD].  Such a managenent should consider the load
   balance among the switches for NFV
   technology, the defense against DDoS attacks.

   The procedure I2NSF framework can be implemented on top of DDoS-attack mitigation operations in this system is an NFV
   infrastructure as follows:

   1.  A Switch periodically reports show in Figure 4.

   Figure 4 shows an inter-arrival pattern of a
       flow's packets to one of I2NSF framework implementation based on the Switch Controllers.

   2.  The Switch Controller forwards NFV
   reference architecture that the flow's inter-arrival pattern
       to an appropriate security service application, such as DDoS-
       attack Mitigator.

   3. European Telecommunications Standards
   Institute (ETSI) defines [ETSI-NFV].  The NSFs are deployed as
   virtual network functions (VNFs) in Figure 4.  The DDoS-attack Mitigator analyzes Developer's
   Management System in the reported pattern I2NSF framework is responsible for creating
   or removing NSF instances, and can be implemented as the
       flow.

   4.  If virtual
   network functions manager (VNFM) in the DDoS-attack Mitigator regards NFV architecture that
   performs the pattern as a DDoS
       attack, it computes a packet dropping probability corresponding
       to suspiciousness level and reports this DDoS-attack flow to
       Switch Controller.

   5. life-cycle management of VNFs.  The Switch Security Controller installs new rules into switches (e.g.,
       forward packets with
   can be implemented as the suspicious inter-arrival pattern with a
       dropping probability).

   6.  The suspicious flow's packets are randomly dropped by switches
       with Element Management (EM) in the dropping probability.

   For NFV
   architecture that controls and monitors the above centralized DDoS-attack mitigation system, configurations (e.g.,
   function parameters and security policy rules) of VNFs.  Finally, the existing
   SDN protocols
   I2NSF User can be used through standard interfaces between implemented as OSS/BSS (Operational Support
   Systems/Business Support Systems) in the
   DDoS-attack mitigator application and switches [RFC7149]
   [ITU-T.Y.3300][ONF-OpenFlow][ONF-SDN-Architecture].

   The centralized DDoS-attack mitigation system has challenges similar
   to NFV architecture that
   provides interfaces for users in the centralized firewall NFV system.

   The proposed framework can
   resolve the challenges through operation procedure in the above centralized DDoS-attack
   mitigation system I2NSF framework based on SDN the NFV
   architecture is as follows:

   o  Cost:

   1.  The cost of adding DDoS-attack mitigators to network
      resources such as routers, gateways, and switches is substantial
      due to the reason that we need to add DDoS-attack mitigator on
      each network resource.  To solve this, each network resource can
      be managed centrally such that a single DDoS-attack mitigator is
      manipulated by Developer's Mgmt System (DMS) has a centralized server.

   o  Performance: The performance set of DDoS-attack mitigators is often
      slower than the link speed virtual machine
       (VM) images of network interfaces. NSFs, and each VM image can be used to create an
       NSF instance that provides a set of security capabilities.  The checking
       DMS initially registers a mapping table of
      DDoS attacks may reduce the performance ID of each VM
       image and the network interfaces.
      DDoS-attack mitigators can be adaptively deployed among network
      switches, depending on network conditions in the framework.

   o  The management set of network resources: Since there may capabilities that can be hundreds
      of network resources in provided by an administered network, NSF
       instance created from the dynamic
      management of network resources for performance (e.g., load
      balancing) is a challenge for DDoS-attack mitigation.  In VM image into the
      framework, as dynamic network resource management, traffic flow
      forwarding path management can handle Security Controller.

   2.  If the load balancing Security Controller does not have any instantiated NSF
       that has the set of
      network switches [AVANT-GUARD].  With this management, capabilities required to meet the current
      and near-future workload can be spread among security
       requirements from users, it searches the network switches
      for DDoS-attack mitigation.  In addition, DDoS-attack mitigation
      rules can be dynamically added mapping table
       (registered by the DMS) for new DDoS attacks.

   o  The establishment the VM image ID corresponding to the
       required set of policy: Policy should be established for each
      network resource.  However, it is difficult capabilities.

   3.  The Security Controller requests the DMS to describe what flows
      are permitted or denied instantiate an NSF
       with the VM image ID.

   4.  When receiving the instantiation request, the DMS first asks the
       NFV orchestrator for new DDoS-attacks (e.g., DNS reflection
      attack) within a specific organization network under management.
      Thus, a centralized view is helpful the permission required to determine security policies create the NSF
       instance, requests the VIM to allocate resources for such a network.

   So far this document the NSF
       instance, and finally creates the NSF instance based on the
       allocated resources.

   5.  Once the NSF instance has described been created, the DMS performs the
       initial configurations of the procedure NSF instance and impact then notifies the
       Security Controller of the
   three use cases for network-based NSF instance.

   6.  After being notified of the created NSF instance, the Security
       Controller delivers low-level security services using policy rules to the NSF
       instance for policy enforcement.

   The I2NSF framework with SDN networks.  To support these use cases in the
   proposed data-driven security service framework, YANG data models
   described in [consumer-facing-inf-dm], [nsf-facing-inf-dm], and
   [registration-inf-dm] can be used as Consumer-Facing Interface, NSF-
   Facing Interface, and implemented based on the NFV architecture.
   Note that the registration of the capabilities of NSFs is performed
   through the Registration Interface, respectively, along
   with RESTCONF [RFC8040] Interface and NETCONF [RFC6241].

5. the life-cycle management for
   NSFs (VNFs) is performed through the Ve-Vnfm interface, as shown in
   Figure 4.  More details about the I2NSF framework based on the NFV
   reference architecture are described in [i2nsf-nfv-architecture].

7.  Security Considerations

   The I2NSF framework with SDN networks in this document is derived
   from the I2NSF framework [RFC8329], so the security considerations of
   the I2NSF framework should be included in this document.  Therefore,
   proper secure communication channels should be used the delivery of
   control or management messages among the components in the proposed
   framework.

   This document shares all the security issues of SDN that are
   specified in the "Security Considerations" section of [ITU-T.Y.3300].

6.

8.  Acknowledgments

   This work was supported by Institute for Information & communications
   Technology Promotion (IITP) grant funded by the Korea government
   (MSIP) (No.R-20160222-002755, Cloud based Security Intelligence
   Technology Development for the Customized Security Service
   Provisioning).

7.

9.  Contributors

   I2NSF is a group effort.  I2NSF has had a number of contributing
   authors.  The following are considered co-authors:

   o  Hyoungshick Kim (Sungkyunkwan University)

   o  Jinyong Tim Kim (Sungkyunkwan University)
   o  Hyunsik Yang (Soongsil University)

   o  Younghan Kim (Soongsil University)

   o  Jung-Soo Park (ETRI)

   o  Se-Hui Lee (Korea Telecom)

   o  Mohamed Boucadair (Orange)

8.

10.  Informative References

   [AVANT-GUARD]
              Shin, S., Yegneswaran, V., Porras, P., and G. Gu, "AVANT-
              GUARD: Scalable and Vigilant Switch Flow Management in
              Software-Defined Networks", ACM CCS, November 2013.

   [consumer-facing-inf-dm]
              Jeong, J., Kim, E., Ahn, T., Kumar, R., and S. Hares,
              "I2NSF Consumer-Facing Interface YANG Data Model", draft-
              ietf-i2nsf-consumer-facing-interface-dm-00
              ietf-i2nsf-consumer-facing-interface-dm-01 (work in
              progress), March July 2018.

   [consumer-facing-inf-im]
              Kumar, R., Lohiya, A., Qi, D., Bitar, N., Palislamovic,
              S., Xia, L., and J. Jeong, "Information Model for
              Consumer-Facing Interface to Security Controller", draft-
              kumar-i2nsf-client-facing-interface-im-04
              kumar-i2nsf-client-facing-interface-im-06 (work in
              progress), October 2017. July 2018.

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

   [i2nsf-nfv-architecture]
              Yang, H. and Y. Kim, "I2NSF on the NFV Reference
              Architecture", draft-yang-i2nsf-nfv-architecture-02 (work
              in progress), June 2018.

   [i2nsf-nsf-cap-im]
              Xia, L., Strassner, J., Basile, C., and D. Lopez,
              "Information Model of NSFs Capabilities", draft-ietf-
              i2nsf-capability-00
              i2nsf-capability-02 (work in progress), September 2017. July 2018.

   [i2nsf-terminology]
              Hares, S., Strassner, J., Lopez, D., Xia, L., and H.
              Birkholz, "Interface to Network Security Functions (I2NSF)
              Terminology", draft-ietf-i2nsf-terminology-05 (work in
              progress), January 2018.

   [ITU-T.X.1252]
              Recommendation ITU-T X.1252, "Baseline Identity Management
              Terms and Definitions", April 2010.

   [ITU-T.X.800]
              Recommendation ITU-T X.800, "Security Architecture for
              Open Systems Interconnection for CCITT Applications",
              March 1991.

   [ITU-T.Y.3300]
              Recommendation ITU-T Y.3300, "Framework of Software-
              Defined Networking", June 2014.

   [nsf-facing-inf-dm]
              Kim, J., Jeong, J., Park, J., Hares, S., and Q. Lin,
              "I2NSF Network Security Function-Facing Interface YANG
              Data Model", draft-ietf-i2nsf-nsf-facing-interface-data-
              model-00
              model-01 (work in progress), March July 2018.

   [nsf-triggered-steering]
              Hyun, S., Jeong, J., Park, J., and S. Hares, "Service
              Function Chaining-Enabled I2NSF Architecture", draft-hyun-
              i2nsf-nsf-triggered-steering-05
              i2nsf-nsf-triggered-steering-06 (work in progress), March July
              2018.

   [ONF-OpenFlow]
              ONF, "OpenFlow Switch Specification (Version 1.4.0)",
              October 2013.

   [ONF-SDN-Architecture]
              ONF, "SDN Architecture", June 2014.

   [opsawg-firewalls]
              Baker, F. and P. Hoffman, "On Firewalls in Internet
              Security", draft-ietf-opsawg-firewalls-01 (work in
              progress), October 2012.

   [registration-inf-dm]
              Hyun, S., Jeong, J., Roh, T., Wi, S., and J. Park, "I2NSF
              Registration Interface YANG Data Model", draft-hyun-i2nsf-
              registration-dm-03
              registration-dm-04 (work in progress), March July 2018.

   [registration-inf-im]
              Hyun, S., Jeong, J., Roh, T., Wi, S., and J. Park, "I2NSF
              Registration Interface Information Model", draft-hyun-
              i2nsf-registration-interface-im-04
              i2nsf-registration-interface-im-05 (work in progress),
              March
              July 2018.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, July 2006.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", RFC 6020,
              October 2010.

   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)",
              RFC 6241, June 2011.

   [RFC7149]  Boucadair, M. and C. Jacquenet, "Software-Defined
              Networking: A Perspective from within a Service Provider
              Environment", RFC 7149, March 2014.

   [RFC7665]  Halpern, J. and C. Pignataro, "Service Function Chaining
              (SFC) Architecture", RFC 7665, October 2015.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, January 2017.

   [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, July
              2017.

   [RFC8300]  Quinn, P., Elzur, U., and C. Pignataro, "Network Service
              Header (NSH)", RFC 8300, January 2018.

   [RFC8329]  Lopez, D., Lopez, E., Dunbar, L., Strassner, J., and R.
              Kumar, "Framework for Interface to Network Security
              Functions", RFC 8329, February 2018.

Appendix A.  Changes from draft-ietf-i2nsf-applicability-01 draft-ietf-i2nsf-applicability-02

   The following changes have been made from draft-ietf-i2nsf-
   applicability-01:
   applicability-02:

   o  In Section 4, it is clarified what types of security policy rules
      can be enforced by SDN switches or NSFs in explained how the environment of I2NSF framework with SDN. and SFC can
      be combined to support chaining NSFs.

   o  In Section 4, 6, it is explained what should be done by the Security
      Controller in order to divide the enforcement of security policy
      rules into the SDN switches and NSFs in how the I2NSF framework with
      SDN. can be
      implemented based on the NFV reference architecture.

Authors' Addresses

   Jaehoon Paul Jeong
   Department of Software
   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

   Sangwon Hyun
   Department of Software
   Sungkyunkwan Computer Engineering
   Chosun University
   2066 Seobu-Ro, Jangan-Gu
   Suwon, Gyeonggi-Do  16419
   309 Pilmun-daero, Dong-Gu
   Gwangju  61452
   Republic of Korea

   Phone: +82 31 290 7222
   Fax:   +82 31 299 6673 62 230 7473
   EMail: swhyun77@skku.edu
   URI:   http://imtl.skku.ac.kr/ shyun@chosun.ac.kr

   Tae-Jin Ahn
   Korea Telecom
   70 Yuseong-Ro, Yuseong-Gu
   Daejeon  305-811
   Republic of Korea

   Phone: +82 42 870 8409
   EMail: taejin.ahn@kt.com
   Susan Hares
   Huawei
   7453 Hickory Hill
   Saline, MI  48176
   USA

   Phone: +1-734-604-0332
   EMail: shares@ndzh.com

   Diego R. Lopez
   Telefonica I+D
   Jose Manuel Lara, 9
   Seville  41013
   Spain

   Phone: +34 682 051 091
   EMail: diego.r.lopez@telefonica.com