I2NSF                                                           D. Lopez
Internet-Draft                                            Telefonica I+D
Intended status: Informational                                  E. Lopez
Expires: November 4, 2017                                       Fortinet
                                                               L. Dunbar
                                                            J. Strassner
                                                                R. Kumar
                                                        Juniper Networks
                                                             May 3, 2017

         Framework for Interface to Network Security Functions


   This document describes the framework for the Interface to Network
   Security Functions (I2NSF), and defines a reference model (including
   major functional components) for I2NSF.  Network security functions
   (NSFs) are packet-processing engines that inspect and optionally
   modify packets traversing networks, either directly or in the context
   of sessions in which the packet is associated.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 4, 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
   Provisions Relating to IETF Documents

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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions used in this document  . . . . . . . . . . . . . .  3
     2.1.  Acronyms . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  I2NSF Reference Model  . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Consumer-Facing Interface  . . . . . . . . . . . . . . . .  6
     3.2.  NSF-Facing Interface . . . . . . . . . . . . . . . . . . .  6
     3.3.  Registration Interface . . . . . . . . . . . . . . . . . .  7
   4.  Threats Associated with Externally Provided NSFs . . . . . . .  8
   5.  Avoiding NSF Ossification  . . . . . . . . . . . . . . . . . .  9
   6.  The Network Connecting I2NSF Components  . . . . . . . . . . .  9
     6.1.  Network Connecting I2NSF Users and I2NSF Controller  . . .  9
     6.2.  Network Connecting the Security Controller and NSFs  . . . 10
     6.3.  Interface to vNSFs . . . . . . . . . . . . . . . . . . . . 11
   7.  I2NSF Flow Security Policy Structure . . . . . . . . . . . . . 12
     7.1.  Customer-Facing Flow Security Policy Structure . . . . . . 12
     7.2.  NSF-Facing Flow Security Policy Structure  . . . . . . . . 14
     7.3.  Differences from ACL Data Models . . . . . . . . . . . . . 15
   8.  Capability Negotiation . . . . . . . . . . . . . . . . . . . . 15
   9.  Registration Considerations  . . . . . . . . . . . . . . . . . 16
     9.1.  Flow-Based NSF Capability Characterization . . . . . . . . 16
     9.2.  Categories Applicable to the Registration Interface  . . . 17
   10. Manageability Considerations . . . . . . . . . . . . . . . . . 20
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 20
   12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20
   13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
   14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
     14.1. Normative References . . . . . . . . . . . . . . . . . . . 21
     14.2. Informative References . . . . . . . . . . . . . . . . . . 21
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22

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1.  Introduction

   This document describes the framework for the Interface to Network
   Security Functions (I2NSF), and defines a reference model (including
   major functional components) for I2NSF.  This includes an analysis of
   the threats implied by the deployment of NSFs that are externally
   provided.  It also describes how I2NSF facilitates Software-Defined
   Networking (SDN) and Network Function Virtualization (NFV) control,
   while avoiding potential constraints that could limit the internal
   functionality and capabilities of NSFs.

   The I2NSF use cases [I-D.ietf-i2nsf-problem-and-use-cases] call for
   standard interfaces for users of an I2NSF system (e.g., applications,
   overlay or cloud network management system, or enterprise network
   administrator or management system), to inform the I2NSF system which
   I2NSF functions should be applied to which traffic (or traffic
   patterns).  The I2NSF system realizes this as a set of security rules
   for monitoring and controlling the behavior of different traffic.  It
   also provides standard interfaces for users to monitor flow-based
   security functions hosted and managed by different administrative

   [I-D.ietf-i2nsf-problem-and-use-cases] also describes the motivation
   and the problem space for an Interface to Network Security Functions

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

   In this document, these words will appear with that interpretation
   only when in ALL CAPS.  Lower case uses of these words are not to be
   interpreted as carrying RFC-2119 significance.

2.1.  Acronyms

   The following acronyms are used in this document:

   BSS  Business Support System

   CDN  Content Delivery Networks

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   ICN  Information-Centric Networks

   IDS  Intrusion Detection System

   IoT  Internet of Things

   IPS  Intrusion Protection System

   NSF  Network Security Function

   OSS  Operation Support System

2.2.  Definitions

   The following terms, which are used in this document, are defined in
   the I2NSF terminology document [I-D.ietf-i2nsf-terminology]:






      Interface Group

      Intrusion Detection System

      Intrusion Protection System

      Network Security Function


3.  I2NSF Reference Model

   Figure 1 shows a reference model (including major functional
   components and interfaces) for an I2NSF system.  This figure is drawn
   from the point-of-view of the security controller; hence, this view
   does not assume any particular management architecture for either the
   NSFs or for how NSFs are managed (on the function developer's side).
   In particular, the security controller does not participate in NSF
   data plane activities.

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       |  I2NSF User (e.g., Overlay Network Mgnt, Enterprise   |
       |  network Mgnt, another network domain's mgnt, etc.)   |
                            |  Consumer-Facing Interface
               +------------+---------+ Registration  +-------------+
               | Network Operator Mgmt|  Interface    | Developer's |
               | Security Controller  | < --------- > | Mgnt System |
               +----------------+-----+               +-------------+
                                | NSF-Facing Interface
           |               |                 |               |
       +---+---+       +---+---+         +---+---+       +---+---+
       | NSF-1 |  ...  | NSF-m |         | NSF-1 |  ...  | NSF-m |  ...
       +-------+       +-------+         +-------+       +-------+

      Developer Mgnt System A              Developer Mgnt System B

                      Figure 1: I2NSF Reference Model

   When defining controller interfaces, this framework adheres to the
   following principles:

   o  Agnostic of network topology and NSF location in the network

   o  Agnostic of provider of the NSF (i.e., independent of the way that
      the provider makes an NSF available, as well as how the provider
      allows the NSF to be managed)

   o  Agnostic of any vendor-specific operational, administrative, and
      management implementation, hosting environment, and form-factor
      (physical or virtual)

   o  Agnostic to NSF control plane implementation (e.g., signaling

   o  Agnostic to NSF data plane implementation (e.g., encapsulation

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3.1.  Consumer-Facing Interface

   The Consumer-Facing Interface is used to enable different users of a
   given I2NSF system to define, manage, and monitor security policies
   for specific flows within an administrative domain.  In today's
   world, where everything is connected, preventing unwanted traffic has
   become a key challenge.  More and more networks are implemented as a
   form of overlay network, with their paths or links among nodes being
   provided by other networks (a.k.a. underlay networks).

   The overlay network's own security solutions cannot prevent various
   attacks from saturating the access links to the overlay network
   nodes, which may cause various components of one or more overlay
   nodes (e.g., CPU or link bandwidth) to become overloaded, and unable
   to handle their own legitimate traffic.  An I2NSF system can be used
   by overlay networks to request certain flow-based security rules to
   be enforced by underlay networks.  This operates in a similar manner
   to how traditional networks use firewalls or IPS devices to enforce
   traffic rules.  The I2NSF system can reduce, or even eliminate,
   unwanted traffic, which prevents unwanted traffic from consuming
   critical node resources.  The same approach can be used by enterprise
   networks to request their specific flow security policies to be
   enforced by the provider network that interconnects their users.  The
   location and implementation of I2NSF policies are irrelevant to the
   consumer of I2NSF policies.

   Some examples of I2NSF Consumers include:

   o  A videoconference network manager that needs to dynamically inform
      the underlay network to allow, rate-limit, or deny flows (some of
      which are encrypted) based on specific fields in the packets for a
      certain time span

   o  Enterprise network administrators and management systems that need
      to request their provider network to enforce specific I2NSF
      policies for particular flows

   o  An IoT management system sending requests to the underlay network
      to block flows that match a set of specific conditions.

3.2.  NSF-Facing Interface

   The NSF-Facing Interface is used to specify and monitor flow-based
   security policies enforced by one or more NSFs.  Note that the
   controller does not need to use all features of a given NSF, nor does
   it need to use all available NSFs.  Hence, this abstraction enables
   the different features from the set of NSFs that make up able given
   I2NSF system to be treated as building blocks, so that developers are

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   free to use the security functions needed independent of vendor and

   Flow-based NSFs [I-D.ietf-i2nsf-problem-and-use-cases] inspect
   packets in the order that they are received.  The Interface to flow-
   based NSFs can be grouped into the following types of Interface

   1.  NSF Operational and Administrative Interface: an Interface Group
       used by a controller to program the operational state of the NSF;
       this also includes administrative control functions.  Since
       applications and controllers need to dynamically control the
       behavior of traffic that they send and receive, much of the I2NSF
       effort is focused on this Interface Group.

   2.  Monitoring Interface: an Interface Group used by a controller to
       obtain monitoring information from one or more selected NSFs.
       Each interface in this Interface Group could be a query- or a
       report-based interface (as dedcribed above).  This Interface
       Group includes logging and query functions between the NSF and
       external systems.  The functionality of this Interface Group may
       also be defined by other protocols, such as SYSLOG and DOTS.

   3.  Notification Interface: an Interface Group used by a controller
       to receive notification events (e.g., alarms) from NSFs.  This
       requires the NSF to be registered.  The controller may take an
       action based on the event; this SHOULD be specified by an I2NSF
       policy.  This Interface Group does NOT change the operational
       state of the NSF.

   This draft proposes that the flow-based paradigm is used to develop
   the NSF-Facing Interface.  A common trait of flow-based NSFs is in
   the processing of packets based on the content (e.g., header/payload)
   and/or context (e.g., session state, authentication state) of the
   received packets.

3.3.  Registration Interface

   NSFs provided by different vendors may have different capabilities.
   In order to automate the process of utilizing multiple types of
   security functions provided by different vendors, it is necessary to
   have an interface for vendors to define the capabilities of their
   NSFs.  This Interface Group is called the Registration Interface

   An NSF's capabilities can either be pre-configured or retrieved
   dynamically through the Registration Interface Group.  If a new
   function that is exposed to the consumer is added to an NSF, then

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   those capabilities SHOULD be notified to security controllers via the
   Registration Interface Group.

4.  Threats Associated with Externally Provided NSFs

   While associated with a much higher flexibility, and in many cases a
   necessary approach given the deployment conditions, the usage of
   externally provided NSFs implies several additional concerns in
   security.  The most relevant threats associated with a security
   platform of this nature are:

   o  An unknown/unauthorized user can try to impersonate another user
      that can legitimately access external NSF services.  This attack
      may lead to accessing the policies and applications of the
      attacked user or to generate network traffic outside the security
      functions with a falsified identity.

   o  An authorized user may misuse assigned privileges to alter the
      network traffic processing of other users in the NSF underlay or
      platform.  This can become especially serious when such a user has
      higher (or even administration) privileges granted by the provider
      (the direct NSF provider, the ISP or the underlay network

   o  A usermay try to install malformed elements (policy or
      configuration), trying to directly take the control of a NSF or
      the whole provider platform, for example by exploiting a
      vulnerability on one of the functions, or may try to intercept or
      modify the traffic of other users in the same provider platform.

   o  A malicious provider can modify the software providing the
      functions (the operating system or the specific NSF
      implementations) to alter the behavior of the latter.  This event
      has a high impact on all users accessing NSFs as the provider has
      the highest level of privilege on the software in execution.

   o  A user that has physical access to the provider platform can
      modify the behavior of the hardware/software components, or the
      components themselves.  Furthermore, it can access a serial
      console (most devices offer this interface for maintenance
      reasons) to access the NSF software with the same level of
      privilege of the provider.

   The authentication between the user and the NSF environment and, what
   is more important, the attestation of the elements in the NSF
   environment by users could address these threats to an acceptable
   level of risk.  Periodical attestation enables users to detect

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   alterations in the NSFs and their supporting infrastructure, and
   raises the degree of physical control necessary to perform an
   untraceable malicious modification of the environment.

5.  Avoiding NSF Ossification

   An important concept underlying this framework is the fact that
   attackers do not have standards as to how to attack networks, so it
   is equally important not to constrain NSF developers to offering a
   limited set of security functions.  In other words, the introduction
   of I2NSF standards should not make it easier for attackers to
   compromise the network.  Therefore, in constructing standards for
   rules provisioning interfaces to NSFs, it is equally important to
   allow support for specific functions, as this enables the
   introduction of NSFs that evolve to meet new threats.  Proposed
   standards for rules provisioning interfaces to NSFs SHOULD NOT:

   o  Narrowly define NSF categories, or their roles when implemented
      within a network

   o  Attempt to impose functional requirements or constraints, either
      directly or indirectly, upon NSF developers

   o  Be a limited lowest common denominator approach, where interfaces
      can only support a limited set of standardized functions, without
      allowing for developer-specific functions

   o  Be seen as endorsing a best common practice for the implementation
      of NSFs

   To prevent constraints on NSF developers' creativity and innovation,
   this document recommends the Flow-based NSF interfaces to be designed
   from the paradigm of processing packets in the network.  Flow-based
   NSFs ultimately are packet-processing engines that inspect packets
   traversing networks, either directly or in the context of sessions in
   which the packet is associated.  The goal is to create a workable
   interface to NSFs that aids in their integration within legacy, SDN,
   and/or NFV environments, while avoiding potential constraints which
   could limit their functional capabilities.

6.  The Network Connecting I2NSF Components

6.1.  Network Connecting I2NSF Users and I2NSF Controller

   [TBD: should we add the Remote Attestation to this section?]

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   As a general principle, in the I2NSF environment users directly
   interact with the controller.  Given the role of the Security
   Controller, a mutual authentication of users and the Security
   Controller maybe required.  I2NSF does not mandate a specific
   authentication scheme; it is up to the users to choose available
   authentication scheme based on their needs.

   Upon successful authentication, a trusted connection between the user
   and the Security Controller (or an endpoint designated by it) SHALL
   be established.  All traffic to and from the NSF environment will
   flow through this connection.  The connection is intended not only to
   be secure, but trusted in the sense that it SHOULD be bound to the
   mutual authentication between user and Security Controller, as
   described in [I-D.pastor-i2nsf-nsf-remote-attestation], with the only
   possible exception of the application of the lowest levels of
   assurance, in which case the user MUST be made aware of this

6.2.  Network Connecting the Security Controller and NSFs

   Most likely the NSFs are not directly attached to the I2NSF
   Controller; for example, NSFs can be distributed across the network.
   The network that connects the I2NSF Controller with the NSFs can be
   the same network that carries the data traffic, or can be a dedicated
   network for management purposes only.  In either case, packet loss
   could happen due to failure, congestion, or other reasons.

   Therefore, the transport mechanism used to carry the control messages
   and monitoring information should provide reliable message delivery.
   Transport redundancy mechanisms such as Multipath TCP (MPTCP) and the
   Stream Control Transmission Protocol (SCTP) will need to be evaluated
   for applicability.  Latency requirements for control message delivery
   must also be evaluated.

   The network connection between the Security Controller and NSFs can
   rely either on:

   o  Closed environments, where there is only one administrative
      domain.  Less restrictive access control and simpler validation
      can be used inside the domain because of the protected

   o  Open environments, where some NSFs can be hosted in external
      administrative domains or reached via secure external network
      domains.  This requires more restrictive security control to be
      placed over the I2NSF interface.  The information over the I2NSF
      interfaces SHALL be exchanged used trusted channels as described
      in the previous section.

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   When running in an open environment, I2NSF needs to rely on
   interfaces to properly verify peer identities e.g. through an AAA
   framework.  The implementation of identity management functions is
   out of scope for I2NSF.

6.3.  Interface to vNSFs

   Even though there is no difference between virtual network security
   functions (vNSF) and physical NSFs from the policy provisioning
   perspective, there are some unique characteristics in interfacing to
   the vNSFs:

   o  There could be multiple instantiations of one single NSF that has
      been distributed across a network.  When different instantiations
      are visible to the Security Controller, different policies may be
      applied to different instantiations of an individual NSF (e.g., to
      reflect the different roles that each vNSF is designated for).

   o  When multiple instantiations of one single NSF appear as one
      single entity to the Security Controller, the policy provisioning
      has to be sent to the NSF Manager, which in turn disseminates the
      polices to the corresponding instantiations of the NSF, as shown
      in Figure 2 below.

   o  Policies to one vNSF may need to be retrieved and moved to another
      vNSF of the same type when user flows are moved from one vNSF to

   o  Multiple vNSFs may share the same physical platform.

   o  There may be scenarios where multiple vNSFs collectively perform
      the security policies needed.

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                          | Security Controller    |
                                   ^        ^
                                   |        |
                       +-----------+        +------------+
                       |                                 |
                       v                                 v
    + - - - - - - - - - - - - - - - +  + - - - - - - - - - - - - - - - +
    |  NSF-A  +--------------+      |  |  NSF-B  +--------------+      |
    |         |NSF Manager   |      |  |         |NSF Manager   |      |
    |         +--------------+      |  |         +--------------+      |
    | + - - - - - - - - - - - - - + |  | + - - - - - - - - - - - - - + |
    | |+---------+     +---------+| |  | |+---------+     +---------+| |
    | || NSF-A#1 | ... |  NSF-A#n|| |  | ||  NSF-B#1| ... |  NSF-B#m|| |
    | |+---------+     +---------+| |  | |+---------+     +---------+| |
    | |         NSF-A cluster     | |  | |          NSF-B cluster    | |
    | + - - - - - - - - - - - - - + |  | + - - - - - - - - - - - - - + |
    + - - - - - - - - - - - - - - - +  + - - - - - - - - - - - - - - - +

            Figure 2: Cluster of NSF Instantiations Management

7.  I2NSF Flow Security Policy Structure

   Even though security functions come in a variety of form factors and
   have different features, provisioning to flow-based NSFs can be
   standardized by using Event - Condition - Action (ECA) policy

   Event is used to determine whether the condition clause of the Policy
   Rule can be evaluated or not.

   A Condition, when used in the context of policy rules for flow-based
   NSFs, is used to determine whether or not the set of Actions in that
   Policy Rule can be executed or not.  A condition can be based on
   various combinations of the content (header/payload) and/or the
   context (session state, authentication state, etc) of the received

   Action can be simple permit/deny/rate-limiting, applying specify
   profile, or establishing specific secure tunnels, etc.

7.1.  Customer-Facing Flow Security Policy Structure

   This layer is for user's network management system to express and
   monitor the needed flow security policies for their specific flows.

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   Some customers may not have security skills.  As such, they are not
   able to express requirements or security policies that are precise
   enough.  These customers may instead express expectations or intent
   of the functionality desired by their security policies.  Customers
   may also express guidelines such as which certain types of
   destinations are not allowed for certain groups.  As a result, there
   could be different depths or layers of Service Layer policies.  Here
   are some examples of more abstract security Policies that can be
   developed based on the I2NSF defined customer-facing interfaces:

      Pass for Subscriber "xxx"

      Enable basic parental control

      Enable "school protection control"

      Allow Internet traffic from 8:30 to 20:00

      Scan email for malware detection protect traffic to corporate
      network with integrity and confidentiality

      Remove tracking data from Facebook [website = *.facebook.com]

      My son is allowed to access Facebook from 18:30 to 20:00

   One flow policy over Customer-Facing Interface may need multiple
   network functions at various locations to achieve the enforcement.
   Some flow security policies from users may not be granted because of
   resource constraints.

   I2NSF will first focus on simple user policies that can be modeled as
   closely as possible to the flow security policies to individual NSFs.
   The I2NSF simple user flow policies should have similar structure as
   the policies to NSFs, but with more of a user-oriented expression for
   the packet content, context, and other parts of an ECA policy rule.
   This enables the user to construct an ECA policy rule without having
   to know actual tags or addresses in the packets.

   For example, when used in the context of policy rules over the
   Customer-Facing Interface:

      An Event can be "traffic of type X detected"

      A Condition can be a "user identifier is Z" and/or "traffic from
      domain-A to domain-B"

      An Action can be "establish an IPSec tunnel"

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7.2.  NSF-Facing Flow Security Policy Structure

   The NSF-Facing Interface is to pass explicit rules to individual NSFs
   to treat packets, as well as methods to monitor the execution status
   of those functions.

   Here are some examples of events over the NSF facing interface:

      time == 08:00

      NSF state change from standby to active

   Here are some examples of conditions over the NSF facing interface

   o  Packet content values are based on one or more packet headers,
      data from the packet payload, bits in the packet, or something
      derived from the packet

   o  Context values are based on measured and inferred knowledge that
      define the state and environment in which a managed entity exists
      or has existed.  In addition to state data, this includes data
      from sessions, direction of the traffic, time, and geo-location
      information.  State refers to the behavior of a managed entity at
      a particular point in time.  Hence, it may refer to situations in
      which multiple pieces of information that are not available at the
      same time must be analyzed.  For example, tracking established TCP
      connections (connections that have gone through the initial three-
      way handshake).

   Actions to individual flow-based NSFs include:

   o  Action ingress processing, such as pass, drop, rate limiting,
      mirroring, etc.

   o  Action egress processing, such as invoke signaling, tunnel
      encapsulation, packet forwarding and/or transformation.

   o  Applying a specific functional profile or signature - e.g., an IPS
      Profile, a signature file, an anti-virus file, or a URL filtering
      file.  Many flow-based NSFs utilize profile and/or signature files
      to achieve more effective threat detection and prevention.  It is
      not uncommon for a NSF to apply different profiles and/or
      signatures for different flows.  Some profiles/signatures do not
      require any knowledge of past or future activities, while others
      are stateful, and may need to maintain state for a specific length
      of time.

   The functional profile or signature file is one of the key properties

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   that determine the effectiveness of the NSF, and is mostly NSF-
   specific today.  The rulesets and software interfaces of I2NSF aim to
   specify the format to pass profile and signature files while
   supporting specific functionalities of each.

   Policy consistency among multiple security function instances is very
   critical because security policies are no longer maintained by one
   central security device, but instead are enforced by multiple
   security functions instantiated at various locations.

7.3.  Differences from ACL Data Models

   [I-D.ietf-netmod-acl-model] has defined rules for the Access Control
   List supported by most routers/switches that forward packets based on
   packets' L2, L3, or sometimes L4 headers.  The actions for Access
   Control Lists include Pass, Drop, or Redirect.

   The functional profiles (or signatures) for NSFs are not present in
   [I-D.ietf-netmod-acl-model] because the functional profiles are
   unique to specific NSFs.  For example, most IPS/IDS implementations
   have their proprietary functions/profiles.  One of the goals of I2NSF
   is to define a common envelop format for exchanging or sharing
   profiles among different organizations to achieve more effective
   protection against threats.

   The "packet content matching" of the I2NSF policies should not only
   include the matching criteria specified by
   [I-D.ietf-netmod-acl-model] but also the L4-L7 fields depending on
   the NSFs selected.

   Some Flow-based NSFs need matching criteria that include the context
   associated with the packets.

   The I2NSF "actions" should extend the actions specified by
   [I-D.ietf-netmod-acl-model] to include applying statistics functions,
   threat profiles, or signature files that clients provide.

8.  Capability Negotiation

   It is very possible that the underlay network does not have the
   capability or resource to enforce the flow security policies
   requested by the overlay network.  Therefore, it is very important to
   have capability discovery or inquiry mechanisms over the I2NSF
   Customer-Facing Interface for the clients to discover if the needed
   flow polices can be supported or not.

   When an NSF cannot perform the desired provisioning (e.g., due to

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   resource constraints), it MUST inform the controller.

   The protocol needed for this security function/capability negotiation
   may be somewhat correlated to the dynamic service parameter
   negotiation procedure described in [RFC7297].  The Connectivity
   Provisioning Profile (CPP) template, even though currently covering
   only Connectivity requirements (but includes security clauses such as
   isolation requirements, non-via nodes, etc.), could be extended as a
   basis for the negotiation procedure.  Likewise, the companion
   Connectivity Provisioning Negotiation Protocol (CPNP) could be a
   candidate to proceed with the negotiation procedure.

   The "security as a service" would be a typical example of the kind of
   (CPP-based) negotiation procedures that could take place between a
   corporate customer and a service provider.  However, more security
   specific parameters have to be considered.

9.  Registration Considerations

9.1.  Flow-Based NSF Capability Characterization

   There are many types of flow-based NSFs, although the differences
   among them are definitely blurring, due to technological capacity
   increases, integration of platforms, and new threats.  Flow-based
   NSFs differ in the depth of packet header or payload they can
   inspect, the various session/context states they can maintain, and
   the specific profiles and the actions they can apply.  Among the most
   common flow-based NSFs we can consider:

   o  A firewall analyzes packet headers attributes and enforces policy
      based on them.

   o  An IDS (Intrusion Detection System) analyzes packets, both header
      and payload, looking for known events, and generate an event
      (report, warning...) about them.

   o  And IPS (Intrusion Prevention System) analyzes packets, both
      header and payload, looking for known events, and enforces
      policies associated with them.

   o  A security gateway acts as one of the endpoints of an IPsec
      connection, establishing it with other security gateways and
      negotiating IPsec parameters.

   Typically, additional functions, such as logging and notification of
   a system administrator, could optionally be enforced as well.

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9.2.  Categories Applicable to the Registration Interface

   Developers can register their NSFs using Packet Content Match
   categories.  The IDR Flow Specification [RFC5575] has specified 12
   different packet header matching types.  More packet content matching
   types have been proposed in the IDR WG.  I2NSF should re-use the
   packet matching types being specified as much as possible.  More
   matching types might be added for Flow-based NSFS.  Tables 1-4 below
   list the applicable packet content categories that can be potentially
   used as packet matching types by Flow-based NSFs:

        |         Packet Content Matching Capability Index          |
        | Layer 2       | Layer 2 header fields:                    |
        | Header        | Source/Destination/s-VID/c-VID/EtherType/.|
        |               |                                           |
        | Layer 3       | Layer  header fields:                     |
        |               |            protocol                       |
        | IPv4 Header   |            dest port                      |
        |               |            src port                       |
        |               |            src address                    |
        |               |            dest address                   |
        |               |            dscp                           |
        |               |            length                         |
        |               |            flags                          |
        |               |            ttl                            |
        |               |                                           |
        | IPv6 Header   |                                           |
        |               |            addr                           |
        |               |            protocol/nh                    |
        |               |            src port                       |
        |               |            dest port                      |
        |               |            src address                    |
        |               |            dest address                   |
        |               |            length                         |
        |               |            traffic class                  |
        |               |            hop limit                      |
        |               |            flow label                     |
        |               |            dscp                           |
        |               |                                           |
        | TCP           |            Port                           |
        | SCTP          |            syn                            |
        | DCCP          |            ack                            |
        |               |            fin                            |
        |               |            rst                            |
        |               |          ? psh                            |

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        |               |          ? urg                            |
        |               |          ? window                         |
        |               |            sockstress                     |
        |               | Note: bitmap could be used to             |
        |               |   represent all the fields                |
        |               |                                           |
        | UDP           |                                           |
        |               |            flood abuse                    |
        |               |            fragment abuse                 |
        |               |            Port                           |
        | HTTP layer    |                                           |
        |               |          | hash collision                 |
        |               |          | http - get flood               |
        |               |          | http - post flood              |
        |               |          | http - random/invalid url      |
        |               |          | http - slowloris               |
        |               |          | http - slow read               |
        |               |          | http - r-u-dead-yet (rudy)     |
        |               |          | http - malformed request       |
        |               |          | http - xss                     |
        |               |          | https - ssl session exhaustion |
        | IETF PCP      | Configurable                              |
        |               | Ports                                     |
        |               |                                           |
        | IETF TRAM     | profile                                   |
        |               |                                           |
        |               |                                           |

   Table 1: Subject Capability Index

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        |      context  matching Capability Index                   |
        | Session       |   Session state,                          |
        |               |   bidirectional state                     |
        |               |                                           |
        | Time          |   time span                               |
        |               |   time occurrence                         |
        | Events        |   Event URL, variables                    |
        | Location      |   Text string, GPS coords, URL            |
        | Connection    |   Internet (unsecured), Internet          |
        |   Type        |   (secured by VPN, etc.), Intranet, ...   |
        |  Direction    |  Inbound, Outbound                        |
        |  State        |  Authentication State                     |
        |               |  Authorization State                      |
        |               |  Accounting State                         |
        |               |  Session State                            |

   Table 2: Object Capability Index

        |      Action Capability Index                              |
        | Ingress port  |   SFC header termination,                 |
        |               |   VxLAN header termination                |
        |               |   Pass                                    |
        | Actions       |   Deny                                    |
        |               |   Mirror                                  |
        |               |   Simple Statistics: Count (X min; Day;..)|
        |               |   Client specified Functions: URL         |
        | Egress        |   Encap SFC, VxLAN, or other header       |

   Table 3: Action Capability Index

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        |      Functional profile Index                             |
        | Profile types |   Name, type, or                          |
        | Signature     |   Flexible Profile/signature URL          |
        |               | Command for Controller to enable/disable  |
        |               |                                           |

   Table 4: Function Capability Index

10.  Manageability Considerations

   Management of NSFs usually includes:

   o  Lifecycle management and resource management of NSFs

   o  Configuration of devices, such as address configuration, device
      internal attributes configuration, etc.

   o  Signaling

   o  Policy rules provisioning

   I2NSF only focuses on the policy rule provisioning part, i.e. the
   last bullet listed above.

11.  Security Considerations

   Having a secure access to control and monitor NSFs is crucial for
   hosted security services.  Therefore, proper secure communication
   channels have to be carefully specified for carrying the controlling
   and monitoring information between the NSFs and their management
   entity or entities.

12.  IANA Considerations

   This document requires no IANA actions.  RFC Editor: Please remove
   this section before publication.

13.  Acknowledgements

   This document includes significant contributions from Seetharama Rao

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   Durbha (Cablelabs), Ramki Krishnan (Dell), Anil Lohiya (Juniper
   Networks), Joe Parrott (BT), and XiaoJun Zhuang (China Mobile).

   Some of the results leading to this work have received funding from
   the European Union Seventh Framework Programme (FP7/2007-2013) under
   grant agreement no. 611458.

14.  References

14.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
              RFC2119, March 1997,

   [RFC5575]  Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
              and D. McPherson, "Dissemination of Flow Specification
              Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,

   [RFC7297]  Boucadair, M., Jacquenet, C., and N. Wang, "IP
              Connectivity Provisioning Profile (CPP)", RFC 7297,
              DOI 10.17487/RFC7297, July 2014,

14.2.  Informative References

              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-12 (work in
              progress), April 2017.

              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.

              Bogdanovic, D., Koushik, K., Huang, L., and D. Blair,
              "Network Access Control List (ACL) YANG Data Model",
              draft-ietf-netmod-acl-model-10 (work in progress),
              March 2017.


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              Pastor, A., Lopez, D., and A. Shaw, "Remote Attestation
              Procedures for Network Security Functions (NSFs) through
              the I2NSF Security Controller",
              draft-pastor-i2nsf-nsf-remote-attestation-01 (work in
              progress), March 2017.

Authors' Addresses

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

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

   Edward Lopez
   899 Kifer Road
   Sunnyvale, CA  94086

   Phone: +1 703 220 0988
   Email: elopez@fortinet.com

   Linda Dunbar

   Email: Linda.Dunbar@huawei.com

   John Strassner

   Email: John.sc.Strassner@huawei.com

   Rakesh Kumar
   Juniper Networks

   Email: rkkumar@juniper.net

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