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Network Working Group                                            S. Hyun
Internet-Draft                                                  J. Jeong
Intended status: Standards Track                                  S. Woo
Expires: September 14, 2017                                       Y. Yeo
                                                 Sungkyunkwan University
                                                                 J. Park
                                                                    ETRI
                                                          March 13, 2017


                NSF-triggered Traffic Steering Framework
               draft-hyun-i2nsf-nsf-triggered-steering-02

Abstract

   This document describes an architecture of the Interface to Network
   Security Functions (I2NSF) framework which enables traffic steering
   between Network Security Functions (NSFs) for security policy
   enforcement.  Such traffic steering enables the composite inspection
   of network traffic by steering the traffic through multiple types of
   security functions according to the information model for the NSF-
   facing interface in the I2NSF framework.  This document explains the
   additional components integrated into the I2NSF framework and their
   functionalities to achieve NSF-triggered traffic steering.  It also
   describes representative use cases to address major benefits from the
   proposed architecture.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   Drafts.

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

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Objective  . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Architecture . . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  NSF Operation Manager  . . . . . . . . . . . . . . . . . .  7
     4.2.  Developer's Management System  . . . . . . . . . . . . . .  7
     4.3.  Network Security Function Forwarder (NSFF) . . . . . . . .  8
   5.  Information for Traffic Steering . . . . . . . . . . . . . . .  8
     5.1.  Packet Forwarding Header . . . . . . . . . . . . . . . . .  9
     5.2.  NSF Forwarding Information . . . . . . . . . . . . . . . .  9
       5.2.1.  Query of NSF forwarding information  . . . . . . . . . 10
       5.2.2.  Response of NSF forwarding information . . . . . . . . 10
   6.  Use Cases  . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     6.1.  Enforcing Different NSFs Depending on a Packet
           Source's Trust Level . . . . . . . . . . . . . . . . . . . 11
     6.2.  Effective Load Balancing with Dynamic NSF Instantiation  . 12
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 13
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 14
   Appendix A.  Changes from
                draft-hyun-i2nsf-nsf-triggered-steering-01  . . . . . 15









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1.  Introduction

   To effectively cope with emerging sophisticated network attacks, it
   is necessary that various security functions cooperatively analyze
   network traffic [sfc-ns-use-cases] [RFC7498] [i2nsf-problem]
   [capability-im].  In addition, depending on the characteristics of
   network traffic and their suspiciousness level, the different types
   of network traffic need to be analyzed through the different sets of
   security functions. [capability-im] proposes an information model for
   the interface between a Security Controller and Network Security
   Functions (NSFs) (called NSF-facing interface) in the Interface to
   Network Security Functions (I2NSF) framework [i2nsf-framework].  This
   NSF-facing interface enables an NSF to trigger further inspection by
   calling another NSF based on its own analysis results.  However, the
   current design of the I2NSF framework does not consider network
   traffic steering fully in order to enable such consecutive
   inspections through multiple security functions.

   In this document, we propose an architecture that integrates
   additional components for traffic steering over NSFs into the I2NSF
   framework.  We extend the security controller's functionalities such
   that it can interpret a high-level policy of NSF-triggered traffic
   steering into a low-level policy and manage them.  It also keeps
   track of the available network security function instances and their
   information (e.g., network information and workload), and makes a
   decision on which NSF instances to use for a given network security
   function.  Based on the forwarding information provided by the
   security controller, the security function forwarder performs network
   traffic steering through required security functions.  The security
   function forwarder is also responsible for interpreting inspection
   result from a network security function to enforce more advanced
   inspection.  We define an additional packet header format to specify
   security inspection results and advanced inspection requests.

2.  Objective

   o  Policy configuration for consecutive inspections: NSF-triggered
      traffic steering architecture allows policy configuration and
      management of network security function triggering.  Based on the
      triggering policy, relevant network traffic can be analyzed
      through various security functions in a composite, cooperative
      manner.

   o  Network traffic steering for consecutive inspection: NSF-triggered
      traffic steering architecture allows network traffic to be steered
      through multiple required network security functions based on the
      triggering policy.  Moreover, the I2NSF information model for NSF-
      facing interface [capability-im] requires a security function to



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      call another security function for further inspection based on its
      own inspection result.  To meet this requirement, NSF-triggered
      traffic steering architecture also enables traffic forwarding from
      one security function to another security function.

   o  Load balancing over network security function instances: NSF-
      triggered traffic steering architecture provides load balancing of
      incoming traffic over available network security function
      instances by leveraging the flexible traffic steering mechanism.
      For this objective, it also performs dynamic instantiation of a
      security function when there are an excessive amount of requests
      for that network security function.

3.  Terminology

   This document uses the terminology described in [RFC7665], [RFC7665]
   [sfc-ns-use-cases] [i2nsf-terminology][ONF-SFC-Architecture].

   o  Network Security Function (NSF): A function that is responsible
      for specific treatment of received packets.  A Network Security
      Function can act at various layers of a protocol stack (e.g., at
      the network layer or other OSI layers) [RFC7665].  Sample Network
      Security Service Functions are as follows: Firewall, Intrusion
      Prevention/Detection System (IPS/IDS), Deep Packet Inspection
      (DPI), Application Visibility and Control (AVC), network virus and
      malware scanning, sandbox, Data Loss Prevention (DLP), Distributed
      Denial of Service (DDoS) mitigation and TLS proxy.

   o  Advanced Inspection/Action: As like the I2NSF information model
      for NSF-facing interface [capability-im], Advanced Inspection/
      Action means that a security function calls another security
      function for further inspection based on its own inspection
      result.

   o  Network Security Function Profile (NSF Profile): NSF Profile
      represents NSF's inspection capabilities.  Each NSF has its own
      NSF Profile to specify the type of security service it provides
      and its resource capacity etc.

   o  Network Security Function Operation Manager (NSF Operation
      Manager): NSF Operation Manager consistently manages information
      and state of NSF instances and provides NSF network access
      information to support advanced inspection request.  For example,
      the information includes the supported transport protocols, IP
      addresses, and locations for the NSF instances.  Also, NSF
      Operation Manager takes charge of dynamic management of a pool of
      NSF instances by consulting with Developer's Management System and
      load balancing over NSF instances.



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   o  Packet Forwarding Header/Encapsulation: Packet Forwarding Header
      is used to forward a packet from one NSF to another for further
      inspection.  The former NSF constructs a Packet Forwarding Header
      with the NSF profile of the latter NSF and transmits it to a NSFF.
      The required fields are the action code, the number of the
      metadata, and the metadata.  In this context, the metadata is a
      part of NSF profile.

   o  Network Security Function Forwarder (NSFF): A security function
      forwarder is responsible for forwarding traffic to one or more
      connected network security functions according to the information
      carried in the packet forwarding encapsulation when the traffic
      comes back from an NSF.  Additionally, an NSFF is responsible for
      transporting traffic to another NSFF (in the same or the different
      type of overlay), and terminating overlay inspection [RFC7665].

4.  Architecture

   This section describes an NSF-triggered traffic steering architecture
   and the basic operations of traffic steering.  It also includes
   details about each component of the architecture.

   Figure 1 describes the components of NSF-triggered traffic steering
   architecture.  Our architecture enables support a composite
   inspection of packets in transit.  According to the inspection result
   of each NSF, which is stored in the Packet Forwarding Header, the
   traffic packets could be steered to another NSF for futher detailed
   analysis.  It is also possible to reflect a high-level advanced
   inspection policy and a configuration from I2NSF User which is a
   component of the original I2NSF framwork.  Moreover, the proposed
   architecture provides load balancing, auto supplementary NSF instance
   generation, and the elimination of unused NSF instances.  In order to
   achieve these design purposes, we integrate several components to the
   original I2NSF framwork.  In the following sections, we explain the
   details of each component.
















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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | I2NSF User                                                        |
   |              +-+-+-+-+-+-+-+-+                                    |
   |              |User/          |                                    |
   |              |App Controller |                                    |
   |              +-+-+-+^+-+-+-+-+                                    |
   |                     |                                             |
   |                     |                                             |
   +-+-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         | Consumer Facing Interface
                         |
   +-+-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Security Management System                                        |
   |                     |                                             |
   |       +-+-+-+-+-+-+-v-+-+-+-+                                     |
   |       |Security Controller  |                                     |
   |       |    +-+-+-+-+-+-+    | Registration                        |
   |       |    | NSF       |    |   Interface  +-+-+-+-++-+-+-+-+     |
   |       |    | Opeation  |    |<------------>| Developer's    |     |
   |       |    | Manager   |    |              | Mgnt System    |<--+ |
   |       |    +-+-+-+-+-+-+    |              +-+-+-+-++-+-+-+-+   | |
   |       +-+-+-+-+-+-^-+-+-+-+-+                                   | |
   +-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       | NSF-facing interface                        |
                       |                                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Security Network   |                                             | |
   |                   +-------------------------------------+       | |
   |                   |                                     |       | |
   |             +-+-+-v-+-+-+-+-+-+-+-+-+-+-+-+-+-+         |       | |
   |             |  +---------+       +---------+  |         |       | |
   |             |  |   NSFF  |  ...  |   NSFF  |  |         |       | |
   |             |  +---------+       +---------+  |         |       | |
   |             +-+-+-+-+-+-+-+-^-+-+-+-+-+-+-+-+-+         |       | |
   |                             |                           |       | |
   |       +-+-+-+-+-+-+-+-+-+-+-v-+-+-+-+-+-+-+-+-+-+-+--+  |       | |
   |       |  +---------+  +---------+       +---------+  |<-+       | |
   |       |  |   NSF   |  |   NSF   |  ...  |   NSF   |  |          | |
   |       |  +---------+  +---------+       +---------+  |<---------+ |
   |       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--+            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


           Figure 1: NSF-triggered Traffic Steering Architecture







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4.1.  NSF Operation Manager

   NSF Operation Manager is a core component in our system.  It is
   responsible for the following three things: (1) Maintaining the
   information of every available NSF instance such as IP address,
   supported transport protocol, NSF profile, and load status. (2)
   Responding the queries of available NSF instances from NSFF so as to
   help to conduct advanced inspection relevant to a given NSF profile.
   (3) Requesting Developer's Management System for the dynamic
   instantiation of supplementary NSF instances to avoid service
   congestion or the elimination of an existing NSF instance to avoid
   resource waste.  As Figure 1 describes, NSF Operation Manager is a
   sub-module of Security Controller.

   Whenever a new NSF instance is registered, Developer's Management
   System passes the information of the registered NSF instance to NSF
   Operation Manager, so NSF Operation Manager maintains a list of the
   information of every available NSF instance.  NSF Operation Manger
   will receive the request packet containing NSF profile for advanced
   inspection from NSFF.  Once receiving a query of a certain NSF
   profile from NSFF, NSF Operation Manager searches for all the
   available NSF instances applicable for that NSF profile and then
   finds the best instance with selection criteria like location and
   load status.  After finding the best instance, it returns the search
   result to NSFF.

   In our system, each NSF instance periodically reports its load status
   to NSF Operation Manager.  Based on such reports, NSF Operation
   Manager updates the information of the NSF instances and manages the
   pool of NSF instances by requesting Developer's Management System for
   the additional instantiation or elimination of the NSF instances.
   Consequently, NSF Operation Manager enables efficient resource
   utilization by avoiding congestion and resource waste.

4.2.  Developer's Management System

   We extend Developer's Management System for additional
   functionalities as follows.  As mentioned above, NSF Operation
   Manager requests Developer's Management System to create additional
   NSF instances when the existing instances of that security function
   are congested.  On the other hand, when there are an excessive number
   of instances for a certain security function, NSF Operation Manager
   requests Developer's Management System to eliminate some of the NSF
   instances.  As a response to such requests, Developer's Management
   System creates and/or removes NSF instances.  Once it creates a new
   NSF instance or removes an existing NSF instance, the changes must be
   notified to NSF Operation Manager.




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4.3.  Network Security Function Forwarder (NSFF)

   It is responsible for the following two functionalities: (1)
   Initially forwarding the incoming traffic/packets to Network Security
   Sub-Module, as described in the I2NSF information model for NSF-
   facing interface [capability-im]. (2) Forwarding the traffic/packets
   to the matched NSF with the NSF profile which is specified in a
   Packet Forwarding Header.

   An NSFF takes a gateway functionality, so it receives incoming
   traffic/packets first and attaches outer encapsulation in order to
   forward the traffic/packets to Network Sub-Module [capability-im].
   The example of Network Sub-Moudle is a firewall which performs packet
   header inspection.  This Network Security Sub-Module attaches a
   Packet Forwarding Header between the outer encapsulation and the
   original packet and specifies NSF Profile in that header so that it
   can be forwarded to Content Security Sub-Module or Mitigate Sub-
   Module for advanced inspection.

   When receiving a packet attached with a packet forwarding header of a
   specific NSF profile, an NSFF searches for an available NSF instance
   which provides the network security service corresponding to
   (matching with) the NSF profile and forward the packet to the NSF
   instance.  If an NSF decides that the packet requires further
   inspection via another type of network security function, it
   constructs a packet forwarding header specified with (including) the
   NSF profile of the advanced network security function, attaches the
   header to the packet, and then sends the resulting packet to the
   NSFF.  Once receiving the packet, the NSFF checks the NSF profile
   specified in the packet forwarding header.  Then it searches for an
   NSF instance matching with the NSF profile by consulting with NSF
   Operation Manager, and finally forwards the packet to the NSF
   instance.

5.  Information for Traffic Steering

   This section describes the details of Packet Forwarding Header and
   NSF Forwarding Information for traffic forwarding between NSFs in the
   I2NSF system












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5.1.  Packet Forwarding Header


   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Outer Encapsulation | Packet Forwarding Header| Origin Packet |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                        /                           \
             +---------+                             +-----------+
            /                                                     \
           /                                                       \
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
          | Action Code | SpecInfo Num| SpecInfo 0| ... | SpecInfo n|
          +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                 Figure 2: Packet Forwarding Header Format

   An NSF uses Packet Forwarding Header to inform an NSFF(NSF Forwarder)
   of its inspection results and/or an advanced security inspection
   which is further required.  As shown in Figure 2, Packet Forwarding
   Header consists of a single Action Code and a variable number of
   SpecInfo fields.  The Action Code field has a value out of "allow",
   "deny", "advanced", and "mirror".  SpecInfo Num field represents how
   many SpecInfos are included in this Packet Forwarding Header, and
   each SpecInfo includes a part of NSF Profile which describes the
   capabilities of an NSF required for an advanced security inspection.
   For instance, the value of SepcInfo can be "syn-flood-mitigate",
   "udp-flood-mitigate" or "content-matching-tcp" etc., which describes
   the service profile of an NSF.

5.2.  NSF Forwarding Information

   The NSF-facing interface takes charge of core functions for steering
   packets in the I2NSF system.


   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               NSF-facing interface                |
   |       +-+-+-+-+-+-+-+       +-+-+-+-+-+-+-+       |
   |       |  NSF Queru  |       |NSF Response |       |
   |       |  Sub-Model  |       |  Sub-Model  |       |
   |       +-+-+-+-+-+-+-+       +-+-+-+-+-+-+-+       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 3: NSF-facing interface Model Design






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5.2.1.  Query of NSF forwarding information

   An NSF can request an NSFF to forward packets to another NSF for more
   advanced security inspection of the packets.  In this case, if the
   NSFF fails to find an NSF that can provide the security capabilities
   required for the advanced inspection in its forwarding information
   table, it sends a query to NSF Operation Manager through NSF-facing
   interface.  The query contains an NSF profile which describes the
   security required for the advanced inspection capabilities.  We share
   the definition of NSF profile in Section 4.4 of [i2nsf-reg-inf-im].


           +-+-+-+-+-+-+-+-+-+-+
           | NSF Query Message |
           |                   |
           +-+-+-+-+-^-+-+-+-+-+
                     |
                     |
                     |
                     |
           +-+-+-+-+-+-+-+-+-+-+
           | Inspection Result |
           |                   |
           +-+-+-+-+-+-+-+-+-+-+

                        Figure 4: NSF Query Message

5.2.2.  Response of NSF forwarding information

   NSF Operation Manager maintains an information table of every NSF
   running in the system.  If it receives the query from an NSFF, NSF
   Operation Manager searches the table for an NSF matching with the NSF
   profile included in the query.  If there are multiple candidate NSFs,
   NSF Operation Manager could further consider the current workload
   levels of those NSFs.  After choosing an NSF, it notifies the NSFF of
   the network forwarding information of the chosen NSF.  The network
   forwarding information consists of IPv4 address, IPv6 address,
   supported transport protocols, and location information.

   o  IP address : As unique indetifier of an NSFs, IP address is the
      basic network information that allows forwarding packets to the
      NSF.

   o  Supported Transport Protocol : In order to forward packets to an
      NSF, it is essential to figure out which transport protocol(s) the
      NSF supports.  Examples of the transport protocols are as follows:
      Virtual Extensible LAN (VXLAN) [RFC7348], Generic Protocol
      Extension for VXLAN (VXLAN-GPE) [nvo3-vxlan-gpe], Generic Route



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      Encapsulation (GRE), Ethernet).  An NSFF performs encapsulation of
      the packets to forward as defined in the transport protocol.

   o  Location Information : NSFs in the system can be distributed over
      a wide physical region.  Unlike IP address, location information
      specifies the physical location of an NSF.  Thus, NSF Operation
      Manager can consider physical proximity as an additional factor to
      select an NSF.



           +-+-+-+-+-+-+-+-+-+-+
           |   NSF Response    |
           |     Message       |
           +-+-+-+-+-^-+-+-+-+-+
                     |
           +---------+----------------+
           |                          |
   +-+-+-+-+-+-+-+            +-+-+-+-+-+-+-+-+-+
   | NSF Profile |            | NSF forwarding  |
   |             |            |  Information    |
   +-+-+-+-+-+-+-+            +-+-+-+-+-+-+-+-+-+
                                      |
              +-----------------------+-----------------------+
              |                       |                       |
       +-+-+-+-+-+-+-+         +-+-+-+-+-+-+-+         +-+-+-+-+-+-+-+
       | IP Address  |         | Supported   |         | Location    |
       |             |         | Protocol    |         | Information |
       +-+-+-+-+-+-+-+         +-+-+-+-+-+-+-+         +-+-+-+-+-+-+-+

                      Figure 5: NSF Response Message

6.  Use Cases

   This section introduces two use cases for the NSF-triggered Traffic
   Steering Framework: (1) Enforcing Different NSFs Depending on a
   Packet Source's Trust Level, (2) Effective Load Balancing with
   Dynamic NSF Instantiation.

6.1.  Enforcing Different NSFs Depending on a Packet Source's Trust
      Level

   In the proposed architecture, all incoming packets initially arrive
   at the NSFF.  We assume that the current security policy forces all
   incoming packets to be by default inspected by a firewall in this
   scenario.  Thus the NSFF forwards the received packets to a firewall
   instance.  Then the firewall identifies the source of the traffic and
   evaluates the trust level of the source.  If the traffic comes from a



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   trusted source, it is likely to be benign.  In this case, the traffic
   is just forwarded to the destination without further detailed
   inspection via different types of security functions as illustrated
   in Figure 6-(a).  Otherwise if the traffic comes from an untrusted
   source, the firewall attaches a packet forwarding header including
   the NSF profile corresponding to DPI to the packet and returns the
   resulting packet to the NSFF.  Once receiving the packet, the NSFF
   forwards the packet to the DPI instance which will perform detailed
   inspection for the packet payload.  Figure 6-(b) illustrates this
   case.


   +-+-+-+-+-+            +-+-+-+-+-+            +-+-+-+-+-+-+-+
   | Source  |----------->| Firewall |----------->| Destination |
   +-+-+-+-+-+            +-+-+-+-+-+            +-+-+-+-+-+-+-+

             (a) Traffic flow of trusted source


   +-+-+-+-+-+     +-+-+-+-+-+     +-+-+-+-+-+     +-+-+-+-+-+-+-+
   | Source  |---->|Firewall |---->|   DPI   |---->| Destination |
   +-+-+-+-+-+     +-+-+-+-+-+     +-+-+-+-+-+     +-+-+-+-+-+-+-+

             (b) Traffic flow of untrusted source


    Figure 6:  Different path allocation depending on source of traffic

6.2.  Effective Load Balancing with Dynamic NSF Instantiation

   In a large-scale network domain, there typically exist a large number
   of NSF instances that provide various security services.  It is
   possible that a specific NSF instance experiences an excessive amount
   of traffic beyond its capacity.  In this case, it is required to
   allocate some of the traffic to another available instance of the
   same security function.  If there are no additional instances of the
   same security function available, we need to create a new NSF
   instance and then direct the subsequent traffic to the new instance.
   In this way, we can avoid service congestion and achieve more
   efficient resource utilization.

   This process is commonly called load balancing.  In our proposed
   architecture, NSF Operation Manager performs periodic monitoring of
   the load status of available NSF instances.  In addition, it is
   possible to dynamically generate a new NSF instance through
   Developer's Management System.  With these functionalities along with
   the flexible traffic steering mechanism, we can eventually provide
   load balancing service.



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   The following describes the detailed process of load balancing when
   congestion occurs at the firewall instance:

   1.  NSF Operation Manager detects that the firewall instance is
       receiving too much requests.  Currently, there are no additional
       firewall instances available.

   2.  NSF Operation Manager requests Developer's Management System to
       create a new firewall instance.

   3.  Developer's Management System creates a new firewall instance and
       then registers the information of the new firewall instance to
       NSF Operation Manager.

   4.  NSF Operation Manager updates the SFC Information Table to
       reflect the new firewall instance, and notifies NSF and NSFF of
       this update.

   5.  According to the new forwarding information, the NSFF forwards
       the subsequent traffic to the new firewall instance.  As a
       result, we can effectively alleviate the burden of the existing
       firewall instance.

7.  Security Considerations

   To enable security function chaining in the I2NSF framework, we adopt
   the additional components in the SFC architecture.  Thus, this
   document shares the security considerations of the SFC architecture
   that are specified in [RFC7665] for the purpose of achieving secure
   communication among components in the proposed architecture.

8.  Acknowledgements

   This work was supported by Institute for Information and
   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).

9.  References

9.1.  Normative References

   [RFC7665]               Boucadair, M. and C. Jacquenet, "Software-
                           Defined Networking: A Perspective from within
                           a Service Provider Environment", RFC 7665,
                           March 2014.




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   [RFC7348]               Mahalingam, M., Dutt, D., Duda, K., Agarwal,
                           P., Kreeger, L., Sridhar, T., Bursell, M.,
                           and C. Wright, "Virtual eXtensible Local Area
                           Network (VXLAN): A Framework for Overlaying
                           Virtualized Layer 2 Networks over Layer 3
                           Networks", RFC 7348, August 2014.

   [sfc-ns-use-cases]      Wang, E., Leung, K., Felix, J., and J. Iyer,
                           "Service Function Chaining Use Cases for
                           Network Security",
                           draft-wang-sfc-ns-use-cases-02 , October
                           2016.

9.2.  Informative References

   [RFC7498]               Quinn, P. and T. Nadeau, "Problem Statement
                           for Service Function Chaining", RFC 7498,
                           April 2015.

   [capability-im]         Xia, L., Strassner, J., Basile, C., and D.
                           Lopez, "Information Model of NSFs
                           Capabilities",
                           draft-xibassnez-i2nsf-capability-01 (work in
                           progress), March 2017.

   [i2nsf-reg-inf-im]      Hyun, S., Woo, S., Yeo, Y., Jeong, J., and J.
                           Park, "Registration Interface Information
                           Model",
                           draft-hyun-i2nsf-registration-interface-im-01
                           (work in progress), March 2017.

   [i2nsf-framework]       Lopez, D., Lopez, E., Dunbar, L., Strassner,
                           J., and R. Kumar, "Framework for Interface to
                           Network Security Functions",
                           draft-ietf-i2nsf-framework-04 (work in
                           progress), October 2016.

   [i2nsf-problem]         Hares, S., Lopez, D., Zarny, M., Jacquenet,
                           C., Kumar, R., and J. Jeong, "I2NSF Problem
                           Statement and Use cases",
                           draft-ietf-i2nsf-problem-and-use-cases-11
                           (work in progress), March  2017.

   [i2nsf-terminology]     Hares, S., Strassner, J., Lopez, D., Xia, L.,
                           and H. Birkholz, "Interface to Network
                           Security Functions (I2NSF) Terminology",
                           draft-ietf-i2nsf-terminology-03 (work in
                           progress), March 2017.



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   [ONF-SFC-Architecture]  ONF, "L4-L7 Service Function Chaining
                           Solution Architecture", June 2015.

   [nvo3-vxlan-gpe]        Maino, F., Kreeger, L., and U. Elzur,
                           "Generic Protocol Extension for VXLAN",
                           draft-ietf-nvo3-vxlan-gpe-03 (work in
                           progress), October 2016.

Appendix A.  Changes from draft-hyun-i2nsf-nsf-triggered-steering-01

   The following changes are made from
   draft-hyun-i2nsf-nsf-triggered-steering-01:

   o  Section 5 is added to explain more details of Packet Forwarding
      Header and NSF Forwarding Information than the previous version.

   o  In Section 5.1, the explanation of Packet Forwarding Header is
      clarified more clearly.

   o  In Section 5.2, we specify the details of NSF Forwarding
      Information.

Authors' Addresses

   Sangwon Hyun
   Department of Software
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon, Gyeonggi-Do  16419
   Republic of Korea

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
















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   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


   SangUk Woo
   Department of Software
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon, Gyeonggi-Do  16419
   Republic of Korea

   Phone: +82 31 290 7222
   Fax:   +82 31 299 6673
   EMail: suwoo@imtl.skku.ac.kr,
   URI:   http://imtl.skku.ac.kr/index.php?mid=member_student


   YunSuk Yeo
   Department of Software
   Sungkyunkwan University
   2066 Seobu-Ro, Jangan-Gu
   Suwon, Gyeonggi-Do  16419
   Republic of Korea

   Phone: +82 31 290 7222
   Fax:   +82 31 299 6673
   EMail: yunsuk@imtl.skku.ac.kr,
   URI:   http://imtl.skku.ac.kr/index.php?mid=member_student


   Jung-Soo Park
   Electronics and Telecommunications Research Institute
   218 Gajeong-Ro, Yuseong-Gu
   Daejeon  305-700
   Republic of Korea

   Phone: +82 42 860 6514
   EMail: pjs@etri.re.kr




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