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I2NSF                                                           D. Lopez
Internet-Draft                                            Telefonica I+D
Intended status: Informational                                  E. Lopez
Expires: November 3, 2017                             Curveball Networks
                                                               L. Dunbar
                                                            J. Strassner
                                                                R. Kumar
                                                        Juniper Networks
                                                            July 2, 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 to 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 3, 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.  I2NSF Consumer-Facing Interface  . . . . . . . . . . . . .  6
     3.2.  I2NSF NSF-Facing Interface . . . . . . . . . . . . . . . .  6
     3.3.  I2NSF 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 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.  Registration Categories  . . . . . . . . . . . . . . . . . 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 Network Security Functions
   (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.

   Note:  as this is an informational document, no RFC-2119 key words
   are used.

2.1.  Acronyms

   The following acronyms are used in this document:

      IDS  Intrusion Detection System
      IoT  Internet of Things
      IPS  Intrusion Protection System
      NSF  Network Security Function

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2.2.  Definitions

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




      I2NSF Consumer

      I2NSF NSF-Facing Interface

      I2NSF Policy Rule

      I2NSF Producer

      I2NSF Registration Interface

      I2NSF Registry


      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 Controller; hence, this view does not
   assume any particular management architecture for either the NSFs
   or for how NSFs are managed (on the developer's side).  In
   particular, the controller does not participate in NSF data
   plane activities.

   Note that the term "Controller" is defined in

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

   The I2NSF 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. 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.  I2NSF NSF-Facing Interface

   The I2NSF NSF-Facing Interface (NSF-Facing Interface for short) 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 free to use the security
   functions needed independent of vendor and technology.

   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.  I2NSF
       Policy Rules represent one way to change this Interface Group in
       a consistent manner. 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.

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   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 described 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
       (DDoS Open Threat Signaling). This Interface Group does NOT
       change the operational state of the NSF.

   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 Rule.  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.  I2NSF 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 a dedicated interface for vendors to define the capabilities of
   (i.e., register) their NSFs.  This Interface is called the
   I2NSF Registration Interface.

   An NSF's capabilities can either be pre-configured or retrieved
   dynamically through the I2NSF Registration Interface.  If a new
   function that is exposed to the consumer is added to an NSF, then
   the capabilities of that new function should be registered in the
   I2NSF Registry via the I2NSF Registration Interface, so that
   interested management and control entities may be made aware of them.

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:

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   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 I2NSF Policy Rules and applications of
      the attacked user, and/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

   o  A user may try to install malformed elements (e.g., I2NSF Policy
      Rules, or configuration files), trying to directly take the
      control of a NSF or the whole provider platform. For example,
      a user may exploit 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 (e.g., the operating
      system or the specific NSF implementation) to alter the behavior
      of one or more NSFs.  This event has a high impact on all users
      accessing NSFs, since the provider has the highest level of
      privileges controlling the operation of the software.

   o  A user that has physical access to the provider platform can
      modify the behavior of the hardware/software components, or the
      components themselves. For example, the user 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 above threats may be mitigated by requiring the use of an AAA
   framework for all users to access the I2NSF environment. This could
   be further enhanced by requiring attestation to be used to detect
   changes to the I2NSF environment by authorized parties. Note that
   periodical attestation enables users to detect alterations in
   the NSFs and their supporting infrastructure, and raises the degree
   of physical control necessary to perform an untraceable malicious
   modification of the I2NSF environment.

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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 to not 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
   I2NSF Interfaces as well as I2NSF Policy Rules, 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 I2NSF Interfaces to communicate with NSFs, as well as
   I2NSF Policy Rules to control NSF functionality, 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

   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.

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   Upon successful authentication, a trusted connection between the
   user and the 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 the user and the Controller, as
   described in [I-D.pastor-i2nsf-remote-attestation]. The only
   possible exception is when the required level of assurance is lower,
   (see Section 4.1 of [I-D.pastor-i2nsf-remote-attestation], in which
   case the user must be made aware of this circumstance.

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

6.2.  Network Connecting the 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 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 nature of
      a closed environment.

   o  Open environments, where one or more NSFs can be hosted in one or
      more external administrative domains that are reached via secure
      external network connections.  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.

   When running in an open environment, I2NSF needs to rely on
   interfaces to properly verify peer identities (e.g., through an AAA
   framework).  The implementations of identity management functions,
   as well as the AAA framework, are out of scope for I2NSF.

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6.3.  Interface to vNSFs

   There are some unique characteristics in interfacing to virtual NSFs:

   o  There could be multiple instantiations of one single NSF that has
      been distributed across a network.  When different instantiations
      are visible to the  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).
      Therefore, it is recommended that Roles, in addition to the use
      of robust identities, be used to distinguish between different
      instantiations of the same vNSF.

   o  When multiple instantiations of one single NSF appear as one
      single entity to the Controller, the Controller may need to
      either get assistance from other entities in the I2NSF
      Management System, and/or delegate the provisioning of the
      multiple instantiations of the (single) NSF to other entities in
      the I2NSF Management System. This is 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.

                          |       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

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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 policy rules.

   In this version of I2NSF, policy rules are limited to imperative
   paradigms. I2NSF is using an Event - Condition - Action (ECA) policy,

     o An Event clause is used to trigger the evaluation of the
       Condition clause of the Policy Rule.

     o A Condition clause is used to determine whether or not the set of
         Actions in the I2NSF Policy Rule can be executed or not.

     o An Action clause defines the type of operations that may be
       performed on this packet or flow.

   Each of the above three clauses are defined to be Boolean clauses.
   This means that each is a logical statement that evaluates to either

   The above concepts are described in detail in

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.

   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

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      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.  [I-D.xie-i2nsf-demo-outline-design] describes
   an implementation of translating a set of user policies to the flow
   policies to individual NSFs.

   I2NSF will first focus on simple client policies that can be modeled
   as closely as possible to the flow security policies to individual
   NSFs.  The I2NSF simple client flow policies should have similar
   structure as the policies to NSFs, but with more of a client-oriented
   expression for the packet content, context, and other parts of an ECA
   policy rule.  This enables the client to construct an I2NSF 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 Client
   Facing Interface:

      An Event can be "the client has passed AAA process"

      A Condition can be matching user identifier, or from specific
      ingress or egress points

      An action can be establishing a IPSec tunnel

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

      a 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 data that
      are derived from the packet

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   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
   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

   Policy rules are very different from ACLs. An ACL is NOT a policy.
   Rather, policies are used to manage the construction and lifecycle
   of an ACL.

   [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.

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   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. This may also include metadata.

   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 (or provider network)
   does not have the capability or resource to enforce the flow security
   policies requested by the overlay network (or enterprise network).
   Therefore, it is very important to have a capability discovery or
   inquiry mechanism over the I2NSF Customer-Facing Interface for the
   clients to discover if the needed flow polices can be supported or

   When an NSF cannot perform the desired provisioning (e.g., due to
   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, includes security clauses such as
   isolation requirements and non-via nodes. Hence, could be extended
   as a basis for the negotiation procedure.  Likewise, the companion
   Connectivity Provisioning Negotiation Protocol (CPNP) could be a
   candidate for the negotiation procedure.

   "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.

   [I.D.-draft-xibassnez-i2nsf-capability] describes the concepts of
   capabilities in detail.

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9.  Registration Considerations

9.1.  Flow-Based NSF Capability Characterization

   There are many types of flow-based NSFs.  Firewall, IPS, and IDS are
   the commonly deployed flow-based NSFs.  However, the differences
   among them are definitely blurring, due to more powerful technology,
   integration of platforms, and new threats.  Basic types of
   flow-based NSFs include:

   o  Firewall - A device or a function that analyzes packet headers and
      enforces policy based on protocol type, source address,
      destination address, source port, destination port, and/or other
      attributes of the packet header.  Packets that do not match policy
      are rejected.  Note that additional functions, such as logging and
      notification of a system administrator, could optionally be
      enforced as well.

   o  IDS (Intrusion Detection System) - A device or function that
      analyzes packets, both header and payload, looking for known
      events.  When a known event is detected, a log message is
      generated detailing the event.  Note that additional functions,
      such as notification of a system administrator, could optionally
      be enforced as well.

   o  IPS (Intrusion Prevention System) - A device or function that
      analyzes packets, both header and payload, looking for known
      events.  When a known event is detected, the packet is rejected.
      Note that additional functions, such as logging and notification
      of a system administrator, could optionally be enforced as well.

   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.  An example
   of a session is "allowing outbound connection requests and only
   allowing return traffic from the external network".

9.2.  Registration Categories

   Developers can register their NSFs using Packet Content Match
   categories.  The IDR (Inter-Domain Routing) 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:

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        |         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                            |
        |               |          ? 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              |

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        |               |          | 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: Packet Content Matching Capability Index

Note:  DCCP:  Datagram Congestion Control Protocol
       PCP:   Port Control Protocol
       TRAM:  TURN Revised and Modernized, where TURN stands for
              Traversal Using Relays around NAT

        |      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: Context Matching Capability Index

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        |      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

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

   Table 4: Function Profile Index

10.  Manageability Considerations

   Management of NSFs 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

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

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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
   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., Dunbar, L., Lopez, D., Zarny, M., and C.
              Jacquenet, "I2NSF Problem Statement and Use cases",
              draft-ietf-i2nsf-problem-and-use-cases-16 (work in
              progress),  May 2017.

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              Bogdanovic, D., Sreenivasa, K., Huang, L., and D. Blair,
              "Network Access Control List (ACL) YANG Data Model",
              draft-ietf-netmod-acl-model-11 (work in progress),
              June, 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.

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

              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.

              Xie, Y., Xia, L., and J. Wu, "Interface to Network
              Security Functions Demo Outline Design",
              draft-xie-i2nsf-demo-outline-design-00 (work in progress),
              April 2015.

   [gs_NFV]   "ETSI NFV Group Specification; Network Functions
              Virtualization (NFV) Use Cases. ETSI GS NFV 001v1.1.1",

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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
   Curveball Networks
   Chantilly, Virgina

   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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