Information Model of NSFs Capabilities
draft-ietf-i2nsf-capability-00

I2NSF                                                             L. Xia
Internet-Draft                                              J. Strassner
Intended status: Standard Track                                   Huawei
Expires:  March 29, 2018                                      C. Basile
                                                                  PoliTO
                                                                D. Lopez
                                                                     TID
                                                            Sep 29, 2017


                 Information Model of NSFs Capabilities
                   draft-ietf-i2nsf-capability-00.txt

Abstract

   This document defines the concept of an NSF (Network Security
   Function) Capability, as well as its information model. Capabilities
   are a set of features that are available from a managed entity, and
   are represented as data that unambiguously characterizes an NSF.
   Capabilities enable management entities to determine the set offer
   features from available NSFs that will be used, and simplify the
   management of NSFs.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six
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   as reference material or to cite them other than as "work in
   progress."

   This Internet-Draft will expire on March 29, 2018.

Copyright Notice

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

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   without warranty as described in the Simplified BSD License.

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Table of Contents

   1. Introduction ................................................... 4
   2. Conventions used in this document .............................. 5
      2.1. Acronyms .................................................. 5
   3. Capability Information Model Design ............................ 6
      3.1. Design Principles and ECA Policy Model Overview ........... 6
      3.2. Relation with the External Information Model .............. 8
      3.3. I2NSF Capability Information Model Theory of Operation ... 10
         3.3.1. I2NSF Condition Clause Operator Types ............... 11
         3.3.2  Capability Selection and Usage ...................... 12
         3.3.3.  Capability Algebra ................................. 13
      3.4. Initial NSFs Capability Categories ....................... 16
         3.4.1. Network Security Capabilities ....................... 16
         3.4.2. Content Security Capabilities ....................... 17
         3.4.3. Attack Mitigation Capabilities ...................... 17
   4. Information Sub-Model for Network Security Capabilities ....... 18
      4.1. Information Sub-Model for Network Security ............... 18
         4.1.1. Network Security Policy Rule Extensions ............. 19
         4.1.2. Network Security Policy Rule Operation .............. 20
         4.1.3. Network Security Event Sub-Model .................... 22
         4.1.4. Network Security Condition Sub-Model ................ 23
         4.1.5. Network Security Action Sub-Model ................... 25
      4.2. Information Model for I2NSF Capabilities ................. 26
      4.3. Information Model for Content Security Capabilities ...... 27
      4.4. Information Model for Attack Mitigation Capabilities ..... 28
   5. Security Considerations ....................................... 29
   6. IANA Considerations ........................................... 29
   7. Contributors .................................................. 29
   8. References .................................................... 29
      8.1. Normative References ..................................... 29
      8.2. Informative References ................................... 30
   Appendix A. Network Security Capability Policy Rule Definitions .. 32
      A.1. AuthenticationECAPolicyRule Class Definition ............. 32
      A.2. AuthorizationECAPolicyRuleClass Definition ............... 34
      A.3. AccountingECAPolicyRuleClass Definition .................. 35
      A.4. TrafficInspectionECAPolicyRuleClass Definition ........... 37
      A.5. ApplyProfileECAPolicyRuleClass Definition ................ 38
      A.6. ApplySignatureECAPolicyRuleClass Definition .............. 40
   Appendix B. Network Security Event Class Definitions ............. 42
      B.1. UserSecurityEvent Class Description ...................... 42
         B.1.1. The usrSecEventContent Attribute .................... 42
         B.1.2. The usrSecEventFormat Attribute ..................... 42
         B.1.3. The usrSecEventType Attribute ....................... 42
      B.2. DeviceSecurityEvent Class Description .................... 43
         B.2.1. The devSecEventContent Attribute .................... 43
         B.2.2. The devSecEventFormat Attribute ..................... 43
         B.2.3. The devSecEventType Attribute ....................... 44
         B.2.4. The devSecEventTypeInfo[0..n] Attribute ............. 44
         B.2.5. The devSecEventTypeSeverity Attribute ............... 44



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Table of Contents (continued)

      B.3. SystemSecurityEvent Class Description .................... 44
         B.3.1. The sysSecEventContent Attribute .................... 45
         B.3.2. The sysSecEventFormat Attribute ..................... 45
         B.3.3. The sysSecEventType Attribute ....................... 45
      B.4. TimeSecurityEvent Class Description ...................... 45
         B.4.1. The timeSecEventPeriodBegin Attribute ............... 46
         B.4.2. The timeSecEventPeriodEnd Attribute ................. 46
         B.4.3. The timeSecEventTimeZone Attribute .................. 46
   Appendix C. Network Security Condition Class Definitions ......... 47
      C.1. PacketSecurityCondition .................................. 47
         C.1.1. PacketSecurityMACCondition .......................... 47
            C.1.1.1. The pktSecCondMACDest Attribute ................ 47
            C.1.1.2. The pktSecCondMACSrc Attribute ................. 47
            C.1.1.3. The pktSecCondMAC8021Q Attribute ............... 48
            C.1.1.4. The pktSecCondMACEtherType Attribute ........... 48
            C.1.1.5. The pktSecCondMACTCI Attribute ................. 48
         C.1.2. PacketSecurityIPv4Condition ......................... 48
            C.1.2.1. The pktSecCondIPv4SrcAddr Attribute ............ 48
            C.1.2.2. The pktSecCondIPv4DestAddr Attribute ........... 48
            C.1.2.3. The pktSecCondIPv4ProtocolUsed Attribute ....... 48
            C.1.2.4. The pktSecCondIPv4DSCP Attribute ............... 48
            C.1.2.5. The pktSecCondIPv4ECN Attribute ................ 48
            C.1.2.6. The pktSecCondIPv4TotalLength Attribute ........ 49
            C.1.2.7. The pktSecCondIPv4TTL Attribute ................ 49
         C.1.3. PacketSecurityIPv6Condition ......................... 49
            C.1.3.1. The pktSecCondIPv6SrcAddr Attribute ............ 49
            C.1.3.2. The pktSecCondIPv6DestAddr Attribute ........... 49
            C.1.3.3. The pktSecCondIPv6DSCP Attribute ............... 49
            C.1.3.4. The pktSecCondIPv6ECN Attribute ................ 49
            C.1.3.5. The pktSecCondIPv6FlowLabel Attribute .......... 49
            C.1.3.6. The pktSecCondIPv6PayloadLength Attribute ...... 49
            C.1.3.7. The pktSecCondIPv6NextHeader Attribute ......... 50
            C.1.3.8. The pktSecCondIPv6HopLimit Attribute ........... 50
         C.1.4. PacketSecurityTCPCondition .......................... 50
            C.1.4.1. The pktSecCondTCPSrcPort Attribute ............. 50
            C.1.4.2. The pktSecCondTCPDestPort Attribute ............ 50
            C.1.4.3. The pktSecCondTCPSeqNum Attribute .............. 50
            C.1.4.4. The pktSecCondTCPFlags Attribute ............... 50
            C.1.5. PacketSecurityUDPCondition ....................... 50
               C.1.5.1.1. The pktSecCondUDPSrcPort Attribute ........ 50
               C.1.5.1.2. The pktSecCondUDPDestPort Attribute ....... 51
               C.1.5.1.3. The pktSecCondUDPLength Attribute ......... 51
      C.2. PacketPayloadSecurityCondition ........................... 51
      C.3. TargetSecurityCondition .................................. 51
      C.4. UserSecurityCondition .................................... 51
      C.5. SecurityContextCondition ................................. 52
      C.6. GenericContextSecurityCondition .......................... 52




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Table of Contents (continued)

  Appendix D. Network Security Action Class Definitions ............. 53
      D.1. IngressAction ............................................ 53
      D.2. EgressAction ............................................. 53
      D.3. ApplyProfileAction ....................................... 53
   Appendix E. Geometric Model ...................................... 54
   Authors' Addresses ............................................... 57

1.  Introduction

   The rapid development of virtualized systems requires advanced
   security protection in various scenarios. Examples include network
   devices in an enterprise network, User Equipment in a mobile network,
   devices in the Internet of Things, or residential access users
   [I-D.draft-ietf-i2nsf-problem-and-use-cases].

   NSFs produced by multiple security vendors provide various security
   Capabilities to customers. Multiple NSFs can be combined together to
   provide security services over the given network traffic, regardless
   of whether the NSFs are implemented as physical or virtual functions.

   Security Capabilities describe the set of network security-related
   features that are available to use for security policy enforcement
   purposes. Security Capabilities are independent of the actual
   security control mechanisms that will implement them. Every NSF
   registers the set of Capabilities it offers. Security Capabilities
   are a market enabler, providing a way to define customized security
   protection by unambiguously describing the security features offered
   by a given NSF. Moreover, Security Capabilities enable security
   functionality to be described in a vendor-neutral manner. That is,
   it is not required to refer to a specific product when designing the
   network; rather, the functionality characterized by their
   Capabilities are considered.

   According to [I-D.draft-ietf-i2nsf-framework], there are two types
   of I2NSF interfaces available for security policy provisioning:

      o Interface between I2NSF users and applications, and a security
        controller (Consumer-Facing Interface): this is a service-
        oriented interface that provides a communication channel
        between consumers of NSF data and services and the network
        operator's security controller. This enables security
        information to be exchanged between various applications (e.g.,
        OpenStack, or various BSS/OSS components) and the security
        controller. The design goal of the Consumer-Facing Interface
        is to decouple the specification of security services from
        their implementation.





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      o Interface between NSFs (e.g., firewall, intrusion prevention,
        or anti-virus) and the security controller (NSF-Facing
        Interface): The NSF-Facing Interface is used to decouple the
        security management scheme from the set of NSFs and their
        various implementations for this scheme, and is independent
        of how the NSFs are implemented (e.g., run in Virtual
        Machines or physical appliances). This document defines an
        object-oriented information model for network security, content
        security, and attack mitigation Capabilities, along with
        associated I2NSF Policy objects.

   This document is organized as follows. Section 2 defines conventions
   and acronyms used. Section 3 discusses the design principles for the
   I2NSF Capability information model and related policy model objects.
   Section 4 defines the structure of the information model, which
   describes the policy and capability objects design; details of the
   model elements are contained in the appendices.

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC-2119 [RFC2119].

   This document uses terminology defined in
   [I-D.draft-ietf-i2nsf-terminology] for security related and I2NSF
   scoped terminology.

2.1.  Acronyms

   AAA:     Access control, Authorization, Authentication
   ACL:     Access Control List
   (D)DoD:  (Distributed) Denial of Service (attack)
   ECA:     Event-Condition-Action
   FMR:     First Matching Rule (resolution strategy)
   FW:      Firewall
   GNSF:    Generic Network Security Function
   HTTP:    HyperText Transfer Protocol
   I2NSF:   Interface to Network Security Functions
   IPS:     Intrusion Prevention System
   LMR:     Last Matching Rule (resolution strategy)
   MIME:    Multipurpose Internet Mail Extensions
   NAT:     Network Address Translation
   NSF:     Network Security Function
   RPC:     Remote Procedure Call
   SMA:     String Matching Algorithm
   URL:     Uniform Resource Locator
   VPN:     Virtual Private Network




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3.  Information Model Design

   The starting point of the design of the Capability information model
   is the categorization of types of security functions.  For instance,
   experts agree on what is meant by the terms "IPS", "Anti-Virus", and
   "VPN concentrator".  Network security experts unequivocally refer to
   "packet filters" as stateless devices able to allow or deny packet
   forwarding based on various conditions (e.g., source and destination
   IP addresses, source and destination ports, and IP protocol type
   fields) [Alshaer].

   However, more information is required in case of other devices, like
   stateful firewalls or application layer filters.  These devices
   filter packets or communications, but there are differences in the
   packets and communications that they can categorize and the states
   they maintain. Analogous considerations can be applied for channel
   protection protocols, where we all understand that they will protect
   packets by means of symmetric algorithms whose keys could have been
   negotiated with asymmetric cryptography, but they may work at
   different layers and support different algorithms and protocols. To
   ensure protection, these protocols apply integrity, optionally
   confidentiality, anti-reply protections, and authenticate peers.

3.1.  Capability Information Model Overview

   This document defines a model of security Capabilities that provides
   the foundation for automatic management of NSFs. This includes
   enabling the security controller to properly identify and manage
   NSFs, and allow NSFs to properly declare their functionality, so
   that they can be used in the correct way.

   Some basic design principles for security Capabilities and the
   systems that have to manage them are:

   o Independence: each security Capability should be an independent
      function, with minimum overlap or dependency on other
      Capabilities. This enables each security Capability to be
      utilized and assembled together freely. More importantly,
      changes to one Capability will not affect other Capabilities.
      This follows the Single Responsibility Principle
      [Martin] [OODSRP].
   o Abstraction: each Capability should be defined in a vendor-
      independent manner, and associated to a well-known interface
      to provide a standardized ability to describe and report its
      processing results. This facilitates multi-vendor
      interoperability.
   o Automation: the system must have the ability to auto-discover,
      auto-negotiate, and auto-update its security Capabilities
      (i.e., without human intervention). These features are
      especially useful for the management of a large number of
      NSFs. They are essential to add smart services (e.g., analysis,


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      refinement, Capability reasoning, and optimization) for the
      security scheme employed. These features are supported by many
      design patterns, including the Observer Pattern [OODOP], the
      Mediator Pattern [OODMP], and a set of Message Exchange
      Patterns [Hohpe].
    o Scalability: the management system must have the Capability to
      scale up/down or scale in/out. Thus, it can meet various
      performancerequirements derived from changeable network traffic
      or service requests. In addition, security Capabilities that are
      affected by scalability changes must support reporting statistics
      to the security controller to assist its decision on whether it
      needs to invoke scaling or not. However, this requirement is for
      information only, and is beyond the scope of this document.

   Based on the above principles, a set of abstract and vendor-neutral
   Capabilities with standard interfaces is defined. This provides a
   Capability model that enables a set of NSFs that are required at a
   given time to be selected, as well as the unambiguous definition of
   the security offered by the set of NSFs used. The security
   controller can compare the requirements of users and applications to
   the set of Capabilities that are currently available in order to
   choose which NSFs are needed to meet those requirements. Note that
   this choice is independent of vendor, and instead relies specifically
   on the Capabilities (i.e., the description) of the functions
   provided. The security controller may also be able to customize the
   functionality of selected NSFs.

   Furthermore, when an unknown threat (e.g., zero-day exploits and
   unknown malware) is reported by a NSF, new Capabilities may be
   created, and/or existing Capabilities may be updated (e.g., by
   updating its signature and algorithm). This results in enhancing
   existing NSFs (and/or creating new NSFs) to address the new threats.
   New Capabilities may be sent to and stored in a centralized
   repository, or stored separately in a vendor's local repository.
   In either case, a standard interface facilitates the update process.

   Note that most systems cannot dynamically create a new Capability
   without human interaction. This is an area for further study.

3.2.  ECA Policy Model Overview

   The "Event-Condition-Action" (ECA) policy model is used as the basis
   for the design of I2NSF Policy Rules; definitions of all I2NSF
   policy-related terms are also defined in
   [I-D.draft-ietf-i2nsf-terminology]:

      o Event: An Event is any important occurrence in time of a change
        in the system being managed, and/or in the environment of the
        system being managed. When used in the context of I2NSF
        Policy Rules, it is used to determine whether the Condition
        clause of the I2NSF Policy Rule can be evaluated or not.


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        Examples of an I2NSF Event include time and user actions (e.g.,
        logon, logoff, and actions that violate an ACL).
      o Condition: A condition is defined as a set of attributes,
        features, and/or values that are to be compared with a set of
        known attributes, features, and/or values in order to determine
        whether or not the set of Actions in that (imperative) I2NSF
        Policy Rule can be executed or not. Examples of I2NSF Conditions
        include matching attributes of a packet or flow, and comparing
        the internal state of an NSF to a desired state.
      o Action: An action is used to control and monitor aspects of
        flow-based NSFs when the event and condition clauses are
        satisfied. NSFs provide security functions by executing various
        Actions. Examples of I2NSF Actions include providing intrusion
        detection and/or protection, web and flow filtering, and deep
        packet inspection for packets and flows.

   An I2NSF Policy Rule is made up of three Boolean clauses: an Event
   clause, a Condition clause, and an Action clause. A Boolean clause
   is a logical statement that evaluates to either TRUE or FALSE. It
   may be made up of one or more terms; if more than one term, then a
   Boolean clause connects the terms using logical connectives (i.e.,
   AND, OR, and NOT). It has the following semantics:

         IF <event-clause> is TRUE
            IF <condition-clause> is TRUE
               THEN execute <action-clause>
            END-IF
         END-IF

   Technically, the "Policy Rule" is really a container that aggregates
   the above three clauses, as well as metadata.

   The above ECA policy model is very general and easily extensible,
   and can avoid potential constraints that could limit the
   implementation of generic security Capabilities.

3.3.  Relation with the External Information Model

   Note: the symbology used from this point forward is taken from
   section 3.3 of [I-D.draft-ietf-supa-generic-policy-info-model].

   The I2NSF NSF-Facing Interface is in charge of selecting and
   managing the NSFs using their Capabilities. This is done using
   the following approach:

      1) Each NSF registers its Capabilities with the management system
         when it "joins", and hence makes its Capabilities available to
         the management system;
      2) The security controller selects the set of Capabilities
         required to meet the needs of the security service from all
         available NSFs that it manages;


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      3) The security controller uses the Capability information model
         to match chosen Capabilities to NSFs, independent of vendor;
      4) The security controller takes the above information and
         creates or uses one or more data models from the Capability
         information model to manage the NSFs;
      5) Control and monitoring can then begin.

   This assumes that an external information model is used to define
   the concept of an ECA Policy Rule and its components (e.g., Event,
   Condition, and Action objects). This enables I2NSF Policy Rules
   [I-D.draft-ietf-i2nsf-terminology] to be subclassed from an external
   information model.

   Capabilities are defined as classes (e.g., a set of objects that
   exhibit a common set of characteristics and behavior
   [I-D.draft-ietf-supa-generic-policy-info-model].

   Each Capability is made up of at least one model element (e.g.,
   attribute, method, or relationship) that differentiates it from all
   other objects in the system. Capabilities are, generically, a type
   of metadata (i.e., information that describes, and/or prescribes,
   the behavior of objects); hence, it is also assumed that an external
   information model is used to define metadata (preferably, in the
   form of a class hierarchy). Therefore, it is assumed that
   Capabilities are subclassed from an external metadata model.

   The Capability sub-model is used for advertising, creating,
   selecting, and managing a set of specific security Capabilities
   independent of the type and vendor of device that contains the NSF.
   That is, the user of the NSF-Facing Interface does not care whether
   the NSF is virtualized or hosted in a physical device, who the
   vendor of the NSF is, and which set of entities the NSF is
   communicating with (e.g., a firewall or an IPS). Instead, the user
   only cares about the set of Capabilities that the NSF has, such as
   packet filtering or deep packet inspection. The overall structure
   is illustrated in the figure below:

   +-------------------------+ 0..n         0..n +---------------+
   |                         |/ \               \|   External    |
   | External ECA Info Model + A ----------------+   Metadata    |
   |                         |\ /  Aggregates   /|  Info Model   |
   +-----------+------------+      Metadata      +-------+-------+
               |                                        / \
               |                                         |
              / \                                        |
   Subclasses derived for I2NSF                    +-----+------+
        Security Policies                          | Capability |
                                                   | Sub-Model  |
                                                   +------------+

          Figure 1. The Overall I2NSF Information Model Design


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   This draft defines a set of extensions to a generic, external, ECA
   Policy Model to represent various NSF ECA Security Policy Rules. It
   also defines the Capability Sub-Model; this enables ECA Policy
   Rules to control which Capabilities are seen by which actors, and
   used by the I2NSF system. Finally, it places requirements on what
   type of extensions are required to the generic, external, ECA
   information model and metadata models, in order to manage the
   lifecycle of I2NSF Capabilities.

   Both of the external models shown in Figure 1 could, but do not have
   to, be based on the SUPA information model
   [I-D.draft-ietf-supa-generic-policy-info-model]. Note that classes in
   the Capability Sub-Model will inherit the AggregatesMetadata
   aggregation from the External Metadata Information Model.

   The external ECA Information Model supplies at least a set of classes
   that represent a generic ECA Policy Rule, and a set of classes that
   represent Events, Conditions, and Actions that can be aggregated by
   the generic ECA Policy Rule. This enables I2NSF to reuse this
   generic model for different purposes, as well as refine it (i.e.,
   create new subclasses, or add attributes and relationships) to
   represent I2NSF-specific concepts.

   It is assumed that the external ECA Information Model has the
   ability to aggregate metadata. Capabilities are then sub-classed
   from an appropriate class in the external Metadata Information Model;
   this enables the ECA objects to use the existing aggregation between
   them and Metadata to add Metadata to appropriate ECA objects.

   Detailed descriptions of each portion of the information model are
   given in the following sections.

3.4.  I2NSF Capability Information Model: Theory of Operation

   Capabilities are typically used to represent NSF functions that can
   be invoked. Capabilities are objects, and hence, can be used in the
   event, condition, and/or action clauses of an I2NSF ECA Policy Rule.
   The I2NSF Capability information model refines a predefined metadata
   model; the application of I2NSF Capabilities is done by refining a
   predefined ECA Policy Rule information model that defines how to
   use, manage, or otherwise manipulate a set of Capabilities. In this
   approach, an I2NSF Policy Rule is a container that is made up of
   three clauses: an event clause, a condition clause, and an action
   clause. When the I2NSF policy engine receives a set of events, it
   matches those events to events in active ECA Policy Rules. If the
   event matches, then this triggers the evaluation of the condition
   clause of the matched I2NSF Policy Rule. The condition clause is
   then evaluated; if it matches, then the set of actions in the
   matched I2NSF Policy Rule MAY be executed.




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   This document defines additional important extensions to both the
   external ECA Policy Rule model and the external Metadata model that
   are used by the I2NSF Information Model; examples include
   resolution strategy, external data, and default action. All these
   extensions come from the geometric model defined in [Bas12]. A more
   detailed description is provided in Appendix E; a summary of the
   important points follows.

   Formally, given a set of actions in an I2NSF Policy Rule, the
   resolution strategy maps all the possible subsets of actions to an
   outcome. In other words, the resolution strategy is included in the
   I2NSF Policy Rule to decide how to evaluate all the actions in a
   particular I2NSF Policy Rule. This is then extended to include all
   possible I2NSF Policy Rules that can be applied in a particular
   scenario. Hence, the final action set from all I2NSF Policy Rules
   is deduced.

   Some concrete examples of resolution strategy are the First Matching
   Rule (FMR) or Last Matching Rule (LMR) resolution strategies. When
   no rule matches a packet, the NSFs may select a default action, if
   they support one.

   Resolution strategies may use, besides intrinsic rule data (i.e.,
   event, condition, and action clauses), "external data" associated to
   each rule, such as priority, identity of the creator, and creation
   time. Two examples of this are attaching metadata to the policy
   action and/or policy rule, and associating the policy rule with
   another class to convey such information.

3.4.1.  I2NSF Condition Clause Operator Types

   After having analyzed the literature and some existing NSFs, the
   types of selectors are categorized as exact-match, range-based,
   regex-based, and custom-match [Bas15][Lunt].

   Exact-match selectors are (unstructured) sets: elements can only be
   checked for equality, as no order is defined on them. As an example,
   the protocol type field of the IP header is an unordered set of
   integer values associated to protocols. The assigned protocol
   numbers are maintained by the IANA (http://www.iana.org/assignments/
   protocol-numbers/protocol-numbers.xhtml).

   In this selector, it is only meaningful to specify condition clauses
   that use either the "equals" or "not equals" operators:

      proto = tcp, udp       (protocol type field equals to TCP or UDP)
      proto != tcp           (protocol type field different from TCP)

   No other operators are allowed on exact-match selectors. For example,
   the following is an invalid condition clause, even if protocol types
   map to integers:


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      proto < 62             (invalid condition)

   Range-based selectors are ordered sets where it is possible to
   naturally specify ranges as they can be easily mapped to integers.
   As an example, the ports in the TCP protocol may be represented with
   a range-based selector (e.g., 1024-65535). As another example, the
   following are examples of valid condition clauses:

      source_port = 80
      source_port < 1024
      source_port < 30000 && source_port >= 1024

   We include, in range-based selectors, the category of selectors that
   have been defined by Al-Shaer et al. as "prefix-match" [Alshaer].
   These selectors allow the specification of ranges of values by means
   of simple regular expressions. The typical case is the IP address
   selector (e.g., 10.10.1.*).

   There is no need to distinguish between prefix match and range-based
   selectors; for example, the address range "10.10.1.*" maps to
   "[10.10.1.0,10.10.1.255]".

   Another category of selector types includes those based on regular
   expressions. This selector type is used frequently at the application
   layer, where data are often represented as strings of text. The
   regex-based selector type also includes string-based selectors, where
   matching is evaluated using string matching algorithms (SMA)
   [Cormen]. Indeed, for our purposes, string matching can be mapped to
   regular expressions, even if in practice SMA are much faster. For
   instance, Squid (http://www.squid-cache.org/), a popular Web caching
   proxy that offers various access control Capabilities, allows the
   definition of conditions on URLs that can be evaluated with SMA
   (e.g., dstdomain) or regex matching (e.g., dstdom_regex).

   As an example, the condition clause:

      "URL = *.website.*"

   matches all the URLs that contain a subdomain named website and the
   ones whose path contain the string ".website.". As another example,
   the condition clause:

      "MIME_type = video/*"

   matches all MIME objects whose type is video.

   Finally, the idea of a custom check selector is introduced. For
   instance, malware analysis can look for specific patterns, and
   returns a Boolean value if the pattern is found or not.




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   In order to be properly used by high-level policy-based processing
   systems (such as reasoning systems and policy translation systems),
   these custom check selectors can be modeled as black-boxes (i.e., a
   function that has a defined set of inputs and outputs for a
   particular state), which provide an associated Boolean output.

   More examples of custom check selectors will be presented in the
   next versions of the draft. Some examples are already present in
   Section 6.

3.4.2.  Capability Selection and Usage

   Capability selection and usage are based on the set of security
   traffic classification and action features that an NSF provides;
   these are defined by the Capability model. If the NSF has the
   classification features needed to identify the packets/flows
   required by a policy, and can enforce the needed actions, then
   that particular NSF is capable of enforcing the policy.

   NSFs may also have specific characteristics that automatic processes
   or administrators need to know when they have to generate
   configurations, like the available resolution strategies and the
   possibility to set default actions.

   The Capability information model can be used for two purposes:
   describing the features provided by generic security functions, and
   describing the features provided by specific products. The term
   Generic Network Security Function (GNSF) refers to the classes of
   security functions that are known by a particular system. The idea
   is to have generic components whose behavior is well understood, so
   that the generic component can be used even if it has some vendor-
   specific functions. These generic functions represent a point of
   interoperability, and can be provided by any product that offers the
   required Capabilities. GNSF examples include packet filter, URL
   filter, HTTP filter, VPN gateway, anti-virus, anti-malware, content
   filter, monitoring, and anonymity proxy; these will be described
   later in a revision of this draft as well as in an upcoming data
   model contribution.

   The next section will introduce the algebra to define the
   information model of Capability registration. This associates
   NSFs to Capabilities, and checks whether a NSF has the
   Capabilities needed to enforce policies.

3.4.3.  Capability Algebra

   We introduce a Capability Algebra to ensure that the actions of
   different policy rules do not conflict with each other.

   Formally, two I2NSF Policy Actions conflict with each other if:



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      o the event clauses of each evaluate to TRUE
      o the condition clauses of each evaluate to TRUE
      o the action clauses affect the same object in different ways

   For example, if we have two Policies:

      P1: During 8am-6pm, if traffic is external, then run through FW
      P2: During 7am-8pm, conduct anti-malware investigation

   There is no conflict between P1 and P2, since the actions are
   different. However, consider these two policies:

      P3: During 8am-6pm, John gets GoldService
      P4: During 10am-4pm, FTP from all users gets BronzeService

   P3 and P4 are now in conflict, because between the hours of 10am and
   4pm, the actions of P3 and P4 are different and apply to the same
   user (i.e., John).

   Let us define the concept of a "matched" policy rule as one in which
   its event and condition clauses both evaluate to true. This enables
   the actions in this policy rule to be evaluated. Then, the
   conflict matrix is defined by a 5-tuple {Ac, Cc, Ec, RSc, Dc},
   where:

      o Ac is the set of Actions currently available from the NSF;
      o Cc is the set of Conditions currently available from the NSF;
      o Ec is the set of Events the NSF is able to respond to.
        Therefore, the event clause of an I2NSF ECA Policy Rule that is
        written for an NSF will only allow a set of designated events
        in Ec. For compatibility purposes, we will assume that if Ec={}
        (that is, Ec is empty), the NSF only accepts CA policies.
      o RSc is the set of Resolution Strategies that can be used to
        specify how to resolve conflicts that occur between the actions
        of the same or different policy rules that are matched and
        contained in this particular NSF;
      o Dc defines the notion of a Default action that can be used to
        specify a predefined action when no other alternative action
        was matched by the currently executing I2NSF Policy Rule. An
        analogy is the use of a default statement in a C switch
        statement. This field of the Capability algebra can take the
        following values:
           - An explicit action (that has been predefined; typically,
             this means that it is fixed and not configurable), denoted
             as Dc ={a}. In this case, the NSF will always use the
             action as as the default action.
           - A set of explicit actions, denoted Dc={a1,a2, ...};
             typically, this means that any **one** action can be used
             as the default action. This enables the policy writer to
             choose one of a predefined set of actions {a1, a2, ...} to
             serve as the default action.


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           - A fully configurable default action, denoted as Dc={F}.
             Here, F is a dummy symbol (i.e., a placeholder value) that
             can be used to indicate that the default action can be
             freely selected by the policy editor from the actions Ac
             available at the NSF. In other words, one of the actions
             Ac may be selected by the policy writer to act as the
             default action.
           - No default action, denoted as Dc={}, for cases where the
             NSF does not allow the explicit selection of a default
             action.

*** Note to WG: please review the following paragraphs
*
*  Interesting Capability concepts that could be considered for a next
*  version of the Capability model and algebra include:
*
*     o Event clause representation (e.g., conjunctive vs. disjunctive
*       normal form for Boolean clauses)
*     o Event clause evaluation function, which would enable more
*       complex expressions than simple Boolean expressions to be used
*
*
*     o Condition clause representation (e.g., conjunctive vs.
*       disjunctive normal form for Boolean clauses)
*     o Condition clause evaluation function, which would enable more
*       complex expressions than simple Boolean expressions to be used
*     o Action clause evaluation strategies (e.g., execute first
*       action only, execute last action only, execute all actions,
*       execute all actions until an action fails)
*     o The use of metadata, which can be associated to both an I2NSF
*       Policy Rule as well as objects contained in the I2NSF Policy
*       Rule (e.g., an action), that describe the object and/or
*       prescribe behavior. Descriptive examples include adding
*       authorship information and defining a time period when an NSF
*       can be used to be defined; prescriptive examples include
*       defining rule priorities and/or ordering.
*
*  Given two sets of Capabilities, denoted as
*
*     cap1=(Ac1,Cc1,Ec1,RSc1,Dc1) and
*     cap2=(Ac2,Cc2,Ec2,RSc2,Dc2),
*
*  two set operations are defined for manipulating Capabilities:
*
*     o Capability addition:
*          cap1+cap2 = {Ac1 U Ac2, Cc1 U Cc2, Ec1 U Ec2, RSc1, Dc1}
*     o Capability subtraction:
*          cap1-cap2 = {Ac1 \ Ac2, Cc1 \ Cc2, Ec1 \ Ec2, RSc1, Dc1}
*
*  In the above formulae, "U" is the set union operator and "\" is the
*  set difference operator.


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*  The addition and subtraction of Capabilities are defined as the
*  addition (set union) and subtraction (set difference) of both the
*  Capabilities and their associated actions. Note that **only** the
*  leftmost (in this case, the first matched policy rule) Resolution
*  Strategy and Default Action are used.
*
*  Note: actions, events, and conditions are **symmetric**. This means
*  that when two matched policy rules are merged, the resultant actions
*  and Capabilities are defined as the union of each individual matched
*  policy rule. However, both resolution strategies and default actions
*  are **asymmetric** (meaning that in general, they can **not** be
*  combined, as one has to be chosen). In order to simplify this, we
*  have chosen that the **leftmost** resolution strategy and the
*  **leftmost** default action are chosen. This enables the developer
*  to view the leftmost matched rule as the "base" to which other
*  elements are added.
*
*  As an example, assume that a packet filter Capability, Cpf, is
*  defined. Further, assume that a second Capability, called Ctime,
*  exists, and that it defines time-based conditions. Suppose we need
*  to construct a new generic packet filter, Cpfgen, that adds
*  time-based conditions to Cpf.
*
*
*  Conceptually, this is simply the addition of the Cpf and Ctime
*  Capabilities, as follows:
*     Apf   =  {Allow, Deny}
*     Cpf   =  {IPsrc,IPdst,Psrc,Pdst,protType}
*     Epf   =  {}
*     RSpf  =  {FMR}
*     Dpf   =  {A1}
*
*     Atime =  {Allow, Deny, Log}
*     Ctime =  {timestart, timeend, datestart, datestop}
*     Etime =  {}
*     RStime = {LMR}
*     Dtime =  {A2}
*
*  Then, Cpfgen is defined as:
*     Cpfgen = {Apf U Atime, Cpf U Ctime, Epf U Etime, RSpf, Dpf}
*            = {Allow, Deny, Log},
*              {{IPsrc, IPdst, Psrc, Pdst, protType} U
*               {timestart, timeend, datestart, datestop}},
*              {},
*              {FMR},
*              {A1}
*
*  In other words, Cpfgen provides three actions (Allow, Deny, Log),
*  filters traffic based on a 5-tuple that is logically ANDed with a
*  time period, and uses FMR; it provides A1 as a default action, and
*  it does not react to events.


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*  Note: We are investigating, for a next revision of this draft, the
*  possibility to add further operations that do not follow the
*  symmetric vs. asymmetric properties presented in the previous note.
*  We are looking for use cases that may justify the complexity added
*  by the availability of more Capability manipulation operations.
*
*** End Note to WG


3.5.  Initial NSFs Capability Categories

   The following subsections define three common categories of
   Capabilities: network security, content security, and attack
   mitigation. Future versions of this document may expand both the
   number of categories as well as the types of Capabilities within a
   given category.

3.5.1.  Network Security Capabilities

   Network security is a category that describes the inspecting and
   processing of network traffic based on the use of pre-defined
   security policies.

   The inspecting portion may be thought of as a packet-processing
   engine that inspects packets traversing networks, either directly or
   in the context of flows with which the packet is associated. From
   the perspective of packet-processing, implementations differ in the
   depths of packet headers and/or payloads they can inspect, the
   various flow and context states they can maintain, and the actions
   that can be applied to the packets or flows.

3.5.2.  Content Security Capabilities

   Content security is another category of security Capabilities
   applied to the application layer. Through analyzing traffic contents
   carried in, for example, the application layer, content security
   Capabilities can be used to identify various security functions that
   are required. These include defending against intrusion, inspecting
   for viruses, filtering malicious URL or junk email, blocking illegal
   web access, or preventing malicious data retrieval.

   Generally, each type of threat in the content security category has
   a set of unique characteristics, and requires handling using a set
   of methods that are specific to that type of content. Thus, these
   Capabilities will be characterized by their own content-specific
   security functions.







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3.5.3.  Attack Mitigation Capabilities

   This category of security Capabilities is used to detect and mitigate
   various types of network attacks. Today's common network attacks can
   be classified into the following sets:

      o DDoS attacks:
        - Network layer DDoS attacks: Examples include SYN flood, UDP
          flood, ICMP flood, IP fragment flood, IPv6 Routing header
          attack, and IPv6 duplicate address detection attack;
        - Application layer DDoS attacks: Examples include HTTP flood,
          https flood, cache-bypass HTTP floods, WordPress XML RPC
          floods, and ssl DDoS.
      o Single-packet attacks:
        - Scanning and sniffing attacks: IP sweep, port scanning, etc.
        - malformed packet attacks: Ping of Death, Teardrop, etc.
        - special packet attacks: Oversized ICMP, Tracert, IP timestamp
          option packets, etc.

   Each type of network attack has its own network behaviors and
   packet/flow characteristics. Therefore, each type of attack needs a
   special security function, which is advertised as a set of
   Capabilities, for detection and mitigation. The implementation and
   management of this category of security Capabilities of attack
   mitigation control is very similar to the content security control
   category. A standard interface, through which the security controller
   can choose and customize the given security Capabilities according to
   specific requirements, is essential.


4.  Information Sub-Model for Network Security Capabilities

   The purpose of the Capability Information Sub-Model is to define the
   concept of a Capability, and enable Capabilities to be aggregated to
   appropriate objects. The following sections present the Network
   Security, Content Security, and Attack Mitigation Capability
   sub-models.

4.1.  Information Sub-Model for Network Security

   The purpose of the Network Security Information Sub-Model is to
   define how network traffic is defined, and determine if one or more
   network security features need to be applied to the traffic or not.
   Its basic structure is shown in the following figure:









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                                      +---------------------+
     +---------------+ 1..n      1..n |                     |
     |               |/ \            \| A Common Superclass |
     | ECAPolicyRule + A -------------+   for ECA Objects   |
     |               |\ /            /|                     |
     +-------+-------+                +---------+-----------+
            / \                                / \
             |                                  |
             |                                  |
  (subclasses to define Network         (subclasses of Event,
    Security ECA Policy Rules       Condition, and Action Objects
    extensibly, so that other           for Network Security
    Policy Rules can be added)              Policy Rules)

       Figure 2. Network Security Information Sub-Model Overview

   In the above figure, the ECAPolicyRule, along with the Event,
   Condition, and Action Objects, are defined in the external ECA
   Information Model. The Network Security Sub-Model extends all of
   these objects in order to define security-specific ECA Policy Rules,
   as well as extensions to the (generic) Event, Condition, and
   Action objects.

   An I2NSF Policy Rule is a special type of Policy Rule that is in
   event-condition-action (ECA) form. It consists of the Policy Rule,
   components of a Policy Rule (e.g., events, conditions, actions, and
   some extensions like resolution policy, default action and external
   data), and optionally, metadata. It can be applied to both uni- and
   bi-directional traffic across the NSF.

   Each rule is triggered by one or more events. If the set of events
   evaluates to true, then a set of conditions are evaluated and, if
   true, enable a set of actions to be executed. This takes the
   following conceptual form:

      IF <event-clause> is TRUE
         IF <condition-clause> is TRUE
            THEN execute <action-clause>
         END-IF
      END-IF

   In the above example, the Event, Condition, and Action portions of a
   Policy Rule are all **Boolean Clauses**. Hence, they can contain
   combinations of terms connected by the three logical connectives
   operators (i.e., AND, OR, NOT). An example is:

      ((SLA==GOLD) AND ((numPackets>burstRate) OR NOT(bwAvail<minBW)))

   Note that Metadata, such as Capabilities, can be aggregated by I2NSF
   ECA Policy Rules.



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4.1.1.  Network Security Policy Rule Extensions

   Figure 3 shows an example of more detailed design of the ECA Policy
   Rule subclasses that are contained in the Network Security
   Information Sub-Model, which just illustrates how more specific
   Network Security Policies are inherited and extended from the
   SecurityECAPolicyRule class. Any new kinds of specific Network
   Security Policy can be created by following the same pattern of
   class design as below.

                            +---------------+
                            |    External   |
                            | ECAPolicyRule |
                            +-------+-------+
                                   / \
                                    |
                                    |
                       +------------+----------+
                       | SecurityECAPolicyRule |
                       +------------+----------+
                                    |
                                    |
          +----+-----+--------+-----+----+---------+---------+--- ...
          |          |        |          |         |         |
          |          |        |          |         |         |
   +------+-------+  |  +-----+-------+  |  +------+------+  |
   |Authentication|  |  |  Accounting |  |  |ApplyProfile |  |
   |ECAPolicyRule |  |  |ECAPolicyRule|  |  |ECAPolicyRule|  |
   +--------------+  |  +-------------+  |  +-------------+  |
                     |                   |                   |
              +------+------+     +------+------+     +--------------+
              |Authorization|     |   Traffic   |     |ApplySignature|
              |ECAPolicyRule|     | Inspection  |     |ECAPolicyRule |
              +-------------+     |ECAPolicyRule|     +--------------+
                                  +-------------+

   Figure 3. Network Security Info Sub-Model ECAPolicyRule Extensions

   The SecurityECAPolicyRule is the top of the I2NSF ECA Policy Rule
   hierarchy. It inherits from the (external) generic ECA Policy Rule,
   and represents the specialization of this generic ECA Policy Rule to
   add security-specific ECA Policy Rules. The SecurityECAPolicyRule
   contains all of the attributes, methods, and relationships defined in
   its superclass, and adds additional concepts that are required for
   Network Security (these will be defined in the next version of this
   draft). The six SecurityECAPolicyRule subclasses extend the
   SecurityECAPolicyRule class to represent six different types of
   Network Security ECA Policy Rules. It is assumed that the (external)
   generic ECAPolicyRule class defines basic information in the form of
   attributes, such as an unique object ID, as well as a description
   and other necessary information.


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*** Note to WG
*
*   The design in Figure 3 represents the simplest conceptual design
*   for network security. An alternative model would be to use a
*   software pattern (e.g., the Decorator pattern); this would result
*   in the SecurityECAPolicyRule class being "wrapped" by one or more
*   of the six subclasses shown in Figure 3. The advantage of such a
*   pattern is to reduce the number of active objects at runtime, as
*   well as offer the ability to combine multiple actions of different
*   policy rules (e.g., inspect traffic and then apply a filter) into
*   one. The disadvantage is that it is a more complex software design.
*   The design team is requesting feedback from the WG regarding this.
*
*** End of Note to WG

   It is assumed that the (external) generic ECA Policy Rule is
   abstract; the SecurityECAPolicyRule is also abstract. This enables
   data model optimizations to be made while making this information
   model detailed but flexible and extensible. For example, abstract
   classes may be collapsed into concrete classes.

   The SecurityECAPolicyRule defines network security policy as a
   container that aggregates Event, Condition, and Action objects,
   which are described in Section 4.1.3, 4.1.4, and 4.1.5,
   respectively. Events, Conditions, and Actions can be generic or
   security-specific.

   Brief class descriptions of these six ECA Policy Rules are provided
   in Appendix A.

4.1.2.  Network Security Policy Rule Operation

   A Network Security Policy consists of one or more ECA Policy Rules
   formed from the information model described above. In simpler cases,
   where the Event and Condition clauses remain unchanged, then the
   action of one Policy Rule may invoke additional network security
   actions from other Policy Rules. Network security policy examines
   and performs basic processing of the traffic as follows:

      1. The NSF evaluates the Event clause of a given
         SecurityECAPolicyRule (which can be generic or specific to
         security, such as those in Figure 3). It may use security
         Event objects to do all or part of this evaluation, which are
         defined in section 4.1.3. If the Event clause evaluates to
         TRUE, then the Condition clause of this SecurityECAPolicyRule
         is evaluated; otherwise, the execution of this
         SecurityECAPolicyRule is stopped, and the next
         SecurityECAPolicyRule (if one exists) is evaluated.





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      2. The Condition clause is then evaluated.  It may use security
         Condition objects to do all or part of this evaluation, which
         are defined in section 4.1.4. If the Condition clause
         evaluates to TRUE, it is defined as "matching" the
         SecurityECAPolicyRule; otherwise, execution of this
         SecurityECAPolicyRule is stopped, and the next
         SecurityECAPolicyRule (if one exists) is evaluated.
      3. The set of actions to be executed are retrieved, and then the
         resolution strategy is used to define their execution order.
         This process includes using any optional external data
         associated with the SecurityECAPolicyRule.
      4. Execution then takes one of the following three forms:
         a. If one or more actions is selected, then the NSF may
            perform those actions as defined by the resolution
            strategy. For example, the resolution strategy may only
            allow a single action to be executed (e.g., FMR or LMR),
            or it may allow all actions to be executed (optionally,
            in a particular order). In these and other cases, the NSF
            Capability MUST clearly define how execution will be done.
            It may use security Action objects to do all or part of
            this execution, which are defined in section 4.1.5. If the
            basic Action is permit or mirror, the NSF firstly performs
            that function, and then checks whether certain other
            security Capabilities are referenced in the rule. If yes,
            go to step 5. If no, the traffic is permitted.
         b. If no actions are selected, and if a default action exists,
            then the default action is performed. Otherwise, no actions
            are performed.
         c. Otherwise, the traffic is denied.
      5. If other security Capabilities (e.g., the conditions and/or
         actions implied by Anti-virus or IPS profile NSFs) are
         referenced in the action set of the SecurityECAPolicyRule, the
         NSF can be configured to use the referenced security
         Capabilities (e.g., check conditions or enforce actions).
         Execution then terminates.

   One policy or rule can be applied multiple times to different
   managed objects (e.g., links, devices, networks, VPNS). This not
   only guarantees consistent policy enforcement, but also decreases
   the configuration workload.

4.1.3.  Network Security Event Sub-Model

   Figure 4 shows a more detailed design of the Event subclasses that
   are contained in the Network Security Information Sub-Model.

   The four Event classes shown in Figure 4 extend the (external)
   generic Event class to represent Events that are of interest to
   Network Security. It is assumed that the (external) generic Event
   class defines basic Event information in the form of attributes,
   such as a unique event ID, a description, as well as the date and
   time that the event occurred.

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                                     +---------------------+
        +---------------+ 1..n   1..n|                     |
        |               |/ \        \| A Common Superclass |
        | ECAPolicyRule + A ---------+   for ECA Objects   |
        |               |\ /        /|                     |
        +---------------+            +---------+-----------+
                                              / \
                                               |
                                               |
                   +---------------+-----------+------+
                   |               |                  |
                   |               |                  |
             +-----+----+   +------+------+     +-----+-----+
             | An Event |   | A Condition |     | An Action |
             |   Class  |   |    Class    |     |   Class   |
             +-----+----+   +-------------+     +-----------+
                  / \
                   |
                   |
             +-----+---------+----------------+--------------+-- ...
             |               |                |              |
             |               |                |              |
     +-------+----+ +--------+-----+ +--------+-----+ +------+-----+
     |UserSecurity| |    Device    | |    System    | |TimeSecurity|
     |   Event    | | SecurityEvent| | SecurityEvent| |     Event  |
     +------------+ +--------------+ +--------------+ +------------+

    Figure 4. Network Security Info Sub-Model Event Class Extensions

   The following are assumptions that define the functionality of the
   generic Event class. If desired, these could be defined as
   attributes in a SecurityEvent class (which would be a subclass of
   the generic Event class, and a superclass of the four Event classes
   shown in Figure 4). However, this makes it harder to use any
   generic Event model with the I2NSF events. Assumptions are:

      - All four SecurityEvent subclasses are concrete
      - The generic Event class uses the composite pattern, so
        individual Events as well as hierarchies of Events are
        available (the four subclasses in Figure 4 would be
        subclasses of the Atomic Event class); otherwise, a mechanism
        is needed to be able to group Events into a collection
      - The generic Event class has a mechanism to uniquely identify
        the source of the Event
      - The generic Event class has a mechanism to separate header
        information from its payload
      - The generic Event class has a mechanism to attach zero or more
        metadata objects to it





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*** Note to WG:
*
*   The design in Figure 4 represents the simplest conceptual design
*   design for describing Security Events. An alternative model would
*   be to use a software pattern (e.g., the Decorator pattern); this
*   would result in the SecurityEvent class being "wrapped" by one or
*   more of the four subclasses shown in Figure 4. The advantage of
*   such a pattern is to reduce the number of active objects at runtime,
*   as well as offer the ability to combine multiple events of different
*   types into one. The disadvantage is that it is a more complex
*   software design.
*
*** End of Note to WG

   Brief class descriptions are provided in Appendix B.

4.1.4.  Network Security Condition Sub-Model

   Figure 5 shows a more detailed design of the Condition subclasses
   that are contained in the Network Security Information Sub-Model.
   The six Condition classes shown in Figure 5 extend the (external)
   generic Condition class to represent Conditions that are of interest
   to Network Security. It is assumed that the (external) generic
   Condition class is abstract, so that data model optimizations may be
   defined. It is also assumed that the generic Condition class defines
   basic Condition information in the form of attributes, such as a
   unique object ID, a description, as well as a mechanism to attach
   zero or more metadata objects to it. While this could be defined as
   attributes in a SecurityCondition class (which would be a subclass
   of the generic Condition class, and a superclass of the six
   Condition classes shown in Figure 5), this makes it harder to use
   any generic Condition model with the I2NSF conditions.


*** Note to WG:
*
*   The design in Figure 5 represents the simplest conceptual design
*   for describing Security Conditions. An alternative model would be
*   to use a software pattern (e.g., the Decorator pattern); this would
*   result in the SecurityCondition class being "wrapped" by one or
*   more of the six subclasses shown in Figure 5. The advantage of such
*   a pattern is to reduce the number of active objects at runtime, as
*   well as offer the ability to combine multiple conditions of
*   different types into one. The disadvantage is that it is a more
*   complex software design.
*   The design team is requesting feedback from he WG regarding this.
*
*** End of Note to WG





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                                     +---------------------+
     +---------------+ 1..n     1..n |                     |
     |               |/ \           \| A Common Superclass |
     | ECAPolicyRule+ A -------------+   for ECA Objects   |
     |               |\ /           /|                     |
     +-------+-------+               +-----------+---------+
                                                / \
                                                 |
                                                 |
                       +--------------+----------+----+
                       |              |               |
                       |              |               |
                 +-----+----+  +------+------+  +-----+-----+
                 | An Event |  | A Condition |  | An Action |
                 |   Class  |  |    Class    |  |   Class   |
                 +----------+  +------+------+  +-----------+
                                     / \
                                      |
                                      |
           +--------+----------+------+---+---------+--------+--- ...
           |        |          |          |         |        |
           |        |          |          |         |        |
     +-----+-----+  |  +-------+-------+  |  +------+-----+  |
     |   Packet  |  |  | PacketPayload |  |  |    Target  |  |
     |  Security |  |  |    Security   |  |  |  Security  |  |
     | Condition |  |  |   Condition   |  |  |  Condition |  |
     +-----------+  |  +---------------+  |  +------------+  |
                    |                     |                  |
             +------+-------+  +----------+------+  +--------+-------+
             | UserSecurity |  | SecurityContext |  | GenericContext |
             |   Condition  |  |    Condition    |  |    Condition   |
             +--------------+  +-----------------+  +----------------+

  Figure 5. Network Security Info Sub-Model Condition Class Extensions

   Brief class descriptions are provided in Appendix C.

4.1.5.  Network Security Action Sub-Model

   Figure 6 shows a more detailed design of the Action subclasses that
   are contained in the Network Security Information Sub-Model.

   The four Action classes shown in Figure 6 extend the (external)
   generic Action class to represent Actions that perform a Network
   Security Control function.

   The three Action classes shown in Figure 6 extend the (external)
   generic Action class to represent Actions that are of interest to
   Network Security. It is assumed that the (external) generic Action
   class is abstract, so that data model optimizations may be defined.



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                                      +---------------------+
      +---------------+ 1..n     1..n |                     |
      |               |/ \           \| A Common Superclass |
      | ECAPolicyRule+ A -------------+   for ECA Objects   |
      |               |\ /           /|                     |
      +---------------+               +-----------+---------+
                                                 / \
                                                  |
                                                  |
                          +--------------+--------+------+
                          |              |               |
                          |              |               |
                    +-----+----+  +------+------+  +-----+-----+
                    | An Event |  | A Condition |  | An Action |
                    |   Class  |  |    Class    |  |   Class   |
                    +----------+  +-------------+  +-----+-----+
                                                        / \
                                                         |
                                                         |
                       +-----------------+---------------+------- ...
                       |                 |               |
                       |                 |               |
                   +---+-----+      +----+---+    +------+-------+
                   | Ingress |      | Egress |    | ApplyProfile |
                   | Action  |      | Action |    |     Action   |
                   +---------+      +--------+    +--------------+

      Figure 6. Network Security Info Sub-Model Action Extensions

   It is also assumed that the generic Action class defines basic
   Action information in the form of attributes, such as a unique
   object ID, a description, as well as a mechanism to attach zero or
   more metadata objects to it. While this could be defined as
   attributes in a SecurityAction class (which would be a subclass of
   the generic Action class, and a superclass of the six Action classes
   shown in Figure 6), this makes it harder to use any generic Action
   model with the I2NSF actions.

*** Note to WG
*   The design in Figure 6 represents the simplest conceptual design
*   for describing Security Actions. An alternative model would be to
*   use a software pattern (e.g., the Decorator pattern); this would
*   result in the SecurityAction class being "wrapped" by one or more
*   of the three subclasses shown in Figure 6. The advantage of such a
*   pattern is to reduce the number of active objects at runtime, as
*   well as offer the ability to combine multiple actions of different
*   types into one. The disadvantage is that it is a more complex
*   software design.
*   The design team is requesting feedback from the WG regarding this.
*** End of Note to WG

   Brief class descriptions are provided in Appendix D.

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4.2.  Information Model for I2NSF Capabilities

   The I2NSF Capability Model is made up of a number of Capabilities
   that represent various content security and attack mitigation
   functions. Each Capability protects against a specific type of
   threat in the application layer. This is shown in Figure 7.

   +-------------------------+ 0..n         0..n +---------------+
   |                         |/ \               \|   External    |
   | External ECA Info Model + A ----------------+   Metadata    |
   |                         |\ /  Aggregates   /|  Info Model   |
   +----+--------------------+      Metadata     +-----+---------+
        |                                             / \
        |                                              |
       / \                                             |
    Subclasses    +------------------------------------+-----------+
     derived      | Capability                      |              |
    for I2NSF     | Sub-Model            +----------+---------+    |
   Policy Rules   |                      | SecurityCapability |    |
                  |                      +----------+---------+    |
                  |                                 |              |
                  |                                 |              |
                  |          +----------------------+---+          |
                  |          |                          |          |
                  | +--------+---------+     +----------+--------+ |
                  | | Content Security |     | Attack Mitigation | |
                  | |   Capabilities   |     |    Capabilities   | |
                  | +------------------+     +-------------------+ |
                  +------------------------------------------------+

        Figure 7. I2NSF Security Capability High-Level Model

   Figure 7 shows a common I2NSF Security Capability class, called
   SecurityCapability. This enables us to add common attributes,
   relationships, and behavior to this class without affecting the
   design of the external metadata information model. All I2NSF
   Security Capabilities are then subclassed from the
   SecuritCapability class.

   Note: the SecurityCapability class will be defined in the next
   version of this draft, after feedback from the WG is obtained.


4.3.  Information Model for Content Security Capabilities

   Content security is composed of a number of distinct security
   Capabilities; each such Capability protects against a specific type
   of threat in the application layer. Content security is a type of
   Generic Network Security Function (GNSF), which summarizes a
   well-defined set of security Capabilities, and was shown in Figure 7.


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   Figure 8 shows exemplary types of the content security GNSF.

     +--------------------------------------------------------------+
     |                             +--------------------+           |
     |   Capability                | SecurityCapability |           |
     |   Sub-Model:                +---------+----------+           |
     | Content Security                   / \                       |
     |                                     |                        |
     |                                     |                        |
     |       +-------+----------+----------+---------------+        |
     |       |       |          |                          |        |
     | +-----+----+  |  +-------+----+             +-------+------+ |
     | |Anti-Virus|  |  | Intrusion  |             |    Attack    | |
     | |Capability|  |  | Prevention |             |  Mitigation  | |
     | +----------+  |  | Capability |             | Capabilities | |
     |               |  +------------+             +--------------+ |
     |               |                                              |
     |      +--------+----+------------+-----------+--------+       |
     |      |             |            |           |        |       |
     | +----+-----+ +-----+----+ +-----+----+ +----+-----+  |       |
     | |   URL    | |   Mail   | |   File   | |  Data    |  |       |
     | |Filtering | |Filtering | |Filtering | |Filtering |  |       |
     | |Capability| |Capability| |Capability| |Capability|  |       |
     | +----------+ +----------+ +----------+ +----------+  |       |
     |                                                      |       |
     |             +----------------+------------------+----+       |
     |             |                |                  |            |
     |      +------+------+  +------+------+ +---------+---------+  |
     |      |PacketCapture|  |FileIsolation| |ApplicationBehavior|  |
     |      | Capability  |  | Capability  | |    Capability     |  |
     |      +-------------+  +-------------+ +-------------------+  |
     +--------------------------------------------------------------+

          Figure 8. Network Security Capability Information Model


   The detailed description about a standard interface, and the
   parameters for all the security Capabilities of this category, will
   be defined in a future version of this document.

4.4.  Information Model for Attack Mitigation Capabilities

   Attack mitigation is composed of a number of GNSFs; each one
   protects against a specific type of network attack. Attack
   Mitigation security is a type of GNSF, which summarizes a
   well-defined set of security Capabilities, and was shown in
   Figure 7. Figure 9 shows exemplary types of Attack Mitigation GNSFs.






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     +---------------------------------------------------------------+
     |                           +--------------------+              |
     |    Capability             | SecurityCapability |              |
     |    Sub-Model:             +---------+----------+              |
     | Attack Mitigation                  / \                        |
     |                                     |                         |
     |                                     |                         |
     |       +-------+--------+------------+-------------+           |
     |       |       |        |                          |           |
     | +-----+----+  |  +-----+----+             +-------+------+    |
     | | SSLDDoS  |  |  | PortScan |             |    Content   |    |
     | |Capability|  |  |Capability|             |   Security   |    |
     | +----------+  |  +----------+             | Capabilities |    |
     |               |                           +--------------+    |
     |               |                                               |
     |      +--------+----+------------+-----------+--------+        |
     |      |             |            |           |        |        |
     | +----+-----+ +-----+----+ +-----+----+ +----+-----+  |        |
     | | SYNFlood | | UDPFlood | |ICMPFlood | | WebFlood |  |        |
     | |Capability| |Capability| |Capability| |Capability|  |        |
     | +----------+ +----------+ +----------+ +----------+  |        |
     |                                                      |        |
     |         +-----------------+--------------+-----------+        |
     |         |                 |              |                    |
     | +-------+-------+ +-------+------+ +-----+-----+ +-----+----+ |
     | |IPFragmentFlood| |DNSAmplication| |PingOfDeath| | IPSweep  | |
     | |  Capability   | |  Capability  | |Capability | |Capability| |
     | +---------------+ +--------------+ +-----------+ +----------+ |
     +---------------------------------------------------------------+

        Figure 9. Attack Mitigation Capability Information Model

   The detailed description about a standard interface, and the
   parameters for all the security Capabilities of this category, will
   be defined in a future version of this document.


















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5.  Security Considerations

   The security Capability policy information sent to NSFs should be
   protected by a secure communication channel, to ensure its
   confidentiality and integrity. Note that the NSFs and security
   controller can all be spoofed, which leads to undesirable results
   (e.g., security policy leakage from security controller, or a spoofed
   security controller sending false information to mislead the NSFs).
   Hence, mutual authentication MUST be supported to protected against
   this kind of threat.  The current mainstream security technologies
   (i.e., TLS, DTLS, and IPSEC) can be employed to protect against the
   above threats.

   In addition, to defend against DDoS attacks caused by a hostile
   security controller sending too many configuration messages to the
   NSFs, rate limiting or similar mechanisms should be considered.


6.  IANA Considerations

   TBD


7.  Contributors

   The following people contributed to creating this document, and are
   listed below in alphabetical order:

      Antonio Lioy (Politecnico di Torino)
      Dacheng Zhang (Huawei)
      Edward Lopez (Fortinet)
      Fulvio Valenza (Politecnico di Torino)
      Kepeng Li (Alibaba)
      Luyuan Fang (Microsoft)
      Nicolas Bouthors (QoSmos)


8.  References

8.1.  Normative References

   [RFC2119]
      Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.
   [RFC3539]
      Aboba, B., and Wood, J., "Authentication, Authorization, and
      Accounting (AAA) Transport Profile", RFC 3539, June 2003.






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8.2.  Informative References

   [RFC2975]
      Aboba, B., et al., "Introduction to Accounting Management",
      RFC 2975, October 2000.
   [I-D.draft-ietf-i2nsf-problem-and-use-cases]
      Hares, S., et.al., "I2NSF Problem Statement and Use cases",
      draft-ietf-i2nsf-problem-and-use-cases-16, May 2017.
   [I-D.draft-ietf-i2nsf-framework]
      Lopez, E., et.al., "Framework for Interface to Network Security
      Functions", draft-ietf-i2nsf-framework-06, July, 2017.
   [I-D.draft-ietf-i2nsf-terminology]
      Hares, S., et.al., "Interface to Network Security Functions
      (I2NSF) Terminology", draft-ietf-i2nsf-terminology-03,
      March, 2017
   [I-D.draft-ietf-supa-generic-policy-info-model]
      Strassner, J., Halpern, J., van der Meer, S., "Generic Policy
      Information Model for Simplified Use of Policy Abstractions
      (SUPA)", draft-ietf-supa-generic-policy-info-model-03,
      May, 2017.
   [Alshaer]
      Al Shaer, E. and H. Hamed, "Modeling and management of firewall
      policies", 2004.
   [Bas12]
      Basile, C., Cappadonia, A., and A. Lioy, "Network-Level Access
      Control Policy Analysis and Transformation", 2012.
   [Bas15]
      Basile, C. and Lioy, A., "Analysis of application-layer filtering
      policies with application to HTTP", IEEE/ACM Transactions on
      Networking, Vol 23, Issue 1, February 2015.
   [Cormen]
      Cormen, T., "Introduction to Algorithms", 2009.
   [Hohpe]
      Hohpe, G. and Woolf, B., "Enterprise Integration Patterns",
      Addison-Wesley, 2003, ISBN 0-32-120068-3
   [Lunt]
      van Lunteren, J. and T. Engbersen, "Fast and scalable packet
      classification", IEEE Journal on Selected Areas in Communication,
      vol 21, Issue 4, September 2003.
   [Martin]
      Martin, R.C., "Agile Software Development, Principles, Patterns,
      and Practices", Prentice-Hall, 2002, ISBN: 0-13-597444-5
   [OODMP]
      http://www.oodesign.com/mediator-pattern.html
   [OODOP]
      http://www.oodesign.com/observer-pattern.html
   [OODSRP]
      http://www.oodesign.com/single-responsibility-principle.html





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Appendix A.  Network Security Capability Policy Rule Definitions

   Six exemplary Network Security Capability Policy Rules are
   introduced in this Appendix to clarify how to create different kinds
   of specific ECA policy rules to manage Network Security Capabilities.

   Note that there is a common pattern that defines how these
   ECAPolicyRules operate; this simplifies their implementation. All of
   these six ECA Policy Rules are concrete classes.

   In addition, none of these six subclasses define attributes. This
   enables them to be viewed as simple object containers, and hence,
   applicable to a wide variety of content. It also means that the
   content of the function (e.g., how an entity is authenticated, what
   specific traffic is inspected, or which particular signature is
   applied) is defined solely by the set of events, conditions, and
   actions that are contained by the particular subclass. This enables
   the policy rule, with its aggregated set of events, conditions, and
   actions, to be treated as a reusable object.

A.1.  AuthenticationECAPolicyRule Class Definition

   The purpose of an AuthenticationECAPolicyRule is to define an I2NSF
   ECA Policy Rule that can verify whether an entity has an attribute
   of a specific value. A high-level conceputal figure is shown below.

                                                    +----------------+
   +----------------+ 1..n                    1...n |                |
   |                |/ \  HasAuthenticationMethod  \| Authentication |
   | Authentication + A ----------+-----------------+     Method     |
   | ECAPolicyRule  |\ /          ^                /|                |
   |                |             |                 +----------------+
   +----------------+             |
                                  |
                     +------------+-------------+
                     | AuthenticationRuleDetail |
                     +------------+-------------+
                                 / \ 0..n
                                  |
                                  | PolicyControlsAuthentication
                                  |
                                 / \
                                  A
                                 \ / 0..n
                       +----------+--------------+
                       | ManagementECAPolicyRule |
                       +-------------------------+

            Figure 10.  Modeling Authentication Mechanisms




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   This class does NOT define the authentication method used. This is
   because this would effectively "enclose" this information within the
   AuthenticationECAPolicyRule. This has two drawbacks. First, other
   entities that need to use information from the Authentication
   class(es) could not; they would have to associate with the
   AuthenticationECAPolicyRule class, and those other classes would not
   likely be interested in the AuthenticationECAPolicyRule. Second, the
   evolution of new authentication methods should be independent of the
   AuthenticationECAPolicyRule; this cannot happen if the
   Authentication class(es) are embedded in the
   AuthenticationECAPolicyRule.

   This document only defines the AuthenticationECAPolicyRule; all other
   classes, and the aggregations, are defined in an external model. For
   completeness, descriptions of how the two aggregations are used are
   described below.

   Figure 10 defines an aggregation between an external class, which
   defines one or more authentication methods, and an
   AuthenticationECAPolicyRule. This decouples the implementation of
   authentication mechanisms from how authentication mechanisms are
   managed and used.

   Since different AuthenticationECAPolicyRules can use different
   authentication mechanisms in different ways, the aggregation is
   realized as an association class. This enables the attributes and
   methods of the association class (i.e., AuthenticationRuleDetail) to
   be used to define how a given AuthenticationMethod is used by a
   particular AuthenticationECAPolicyRule.

   Similarly, the PolicyControlsAuthentication aggregation defines
   Policy Rules to control the configuration of the
   AuthenticationRuleDetail association class. This enables the entire
   authentication process to be managed by ECA PolicyRules.

   Note: a data model MAY choose to collapse this design into a more
   efficient implementation. For example, a data model could define two
   attributes for the AuthenticationECAPolicyRule class (e.g., called
   authenticationMethodCurrent and authenticationMethodSupported), to
   represent the HasAuthenticationMethod aggregation and its
   association class. The former would be a string attribute that
   defines the current authentication method used by this
   AuthenticationECAPolicyRule, while the latter would define a set of
   authentication methods, in the form of an authentication Capability,
   which this AuthenticationECAPolicyRule can advertise.








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A.2.  AuthorizationECAPolicyRuleClass Definition

   The purpose of an AuthorizationECAPolicyRule is to define an I2NSF
   ECA Policy Rule that can determine whether access to a resource
   should be given and, if so, what permissions should be granted to
   the entity that is accessing the resource.

   This class does NOT define the authorization method(s) used. This
   is because this would effectively "enclose" this information within
   the AuthorizationECAPolicyRule. This has two drawbacks. First, other
   entities that need to use information from the Authorization
   class(es) could not; they would have to associate with the
   AuthorizationECAPolicyRule class, and those other classes would not
   likely be interested in the AuthorizationECAPolicyRule. Second, the
   evolution of new authorization methods should be independent of the
   AuthorizationECAPolicyRule; this cannot happen if the Authorization
   class(es) are embedded in the AuthorizationECAPolicyRule. Hence,
   this document recommends the following design:

                                                    +---------------+
    +----------------+ 1..n                   1...n |               |
    |                |/ \   HasAuthorizationMethod \| Authorization |
    | Authorization  + A ----------+----------------+     Method    |
    | ECAPolicyRule  |\ /          ^               /|               |
    |                |             |                +---------------+
    +----------------+             |
                                   |
                      +------------+------------+
                      | AuthorizationRuleDetail |
                      +------------+------------+
                                  / \ 0..n
                                   |
                                   | PolicyControlsAuthorization
                                   |
                                  / \
                                   A
                                  \ / 0..n
                        +----------+--------------+
                        | ManagementECAPolicyRule |
                        +-------------------------+

             Figure 11.  Modeling Authorization Mechanisms

   This document only defines the AuthorizationECAPolicyRule; all other
   classes, and the aggregations, are defined in an external model. For
   completeness, descriptions of how the two aggregations are used are
   described below.






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   Figure 11 defines an aggregation between the
   AuthorizationECAPolicyRule and an external class that defines one or
   more authorization methods. This decouples the implementation of
   authorization mechanisms from how authorization mechanisms are
   managed and used.

   Since different AuthorizationECAPolicyRules can use different
   authorization mechanisms in different ways, the aggregation is
   realized as an association class. This enables the attributes and
   methods of the association class (i.e., AuthorizationRuleDetail)
   to be used to define how a given AuthorizationMethod is used by a
   particular AuthorizationECAPolicyRule.

   Similarly, the PolicyControlsAuthorization aggregation defines
   Policy Rules to control the configuration of the
   AuthorizationRuleDetail association class. This enables the entire
   authorization process to be managed by ECA PolicyRules.

   Note: a data model MAY choose to collapse this design into a more
   efficient implementation. For example, a data model could define
   two attributes for the AuthorizationECAPolicyRule class, called
   (for example) authorizationMethodCurrent and
   authorizationMethodSupported, to represent the
   HasAuthorizationMethod aggregation and its association class. The
   former is a string attribute that defines the current authorization
   method used by this AuthorizationECAPolicyRule, while the latter
   defines a set of authorization methods, in the form of an
   authorization Capability, which this AuthorizationECAPolicyRule
   can advertise.

A.3.  AccountingECAPolicyRuleClass Definition

   The purpose of an AccountingECAPolicyRule is to define an I2NSF
   ECA Policy Rule that can determine which information to collect,
   and how to collect that information, from which set of resources
   for the purpose of trend analysis, auditing, billing, or cost
   allocation [RFC2975] [RFC3539].

   This class does NOT define the accounting method(s) used. This is
   because this would effectively "enclose" this information within
   the AccountingECAPolicyRule. This has two drawbacks. First, other
   entities that need to use information from the Accounting class(es)
   could not; they would have to associate with the
   AccountingECAPolicyRule class, and those other classes would not
   likely be interested in the AccountingECAPolicyRule. Second, the
   evolution of new accounting methods should be independent of the
   AccountingECAPolicyRule; this cannot happen if the Accounting
   class(es) are embedded in the AccountingECAPolicyRule. Hence, this
   document recommends the following design:




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                                                    +-------------+
      +----------------+ 1..n                 1...n |             |
      |                |/ \   HasAccountingMethod  \| Accounting  |
      |  Accounting    + A ----------+--------------+   Method    |
      | ECAPolicyRule  |\ /          ^             /|             |
      |                |             |              +-------------+
      +----------------+             |
                                     |
                          +----------+-----------+
                          | AccountingRuleDetail |
                          +----------+-----------+
                                    / \ 0..n
                                     |
                                     | PolicyControlsAccounting
                                     |
                                    / \
                                     A
                                    \ / 0..n
                          +----------+--------------+
                          | ManagementECAPolicyRule |
                          +-------------------------+

              Figure 12.  Modeling Accounting Mechanisms

   This document only defines the AccountingECAPolicyRule; all other
   classes, and the aggregations, are defined in an external model.
   For completeness, descriptions of how the two aggregations are used
   are described below.

   Figure 12 defines an aggregation between the AccountingECAPolicyRule
   and an external class that defines one or more accounting methods.
   This decouples the implementation of accounting mechanisms from how
   accounting mechanisms are managed and used.

   Since different AccountingECAPolicyRules can use different
   accounting mechanisms in different ways, the aggregation is realized
   as an association class. This enables the attributes and methods of
   the association class (i.e., AccountingRuleDetail) to be used to
   define how a given AccountingMethod is used by a particular
   AccountingECAPolicyRule.

   Similarly, the PolicyControlsAccounting aggregation defines Policy
   Rules to control the configuration of the AccountingRuleDetail
   association class. This enables the entire accounting process to be
   managed by ECA PolicyRules.

   Note: a data model MAY choose to collapse this design into a more
   efficient implementation. For example, a data model could define
   two attributes for the AccountingECAPolicyRule class, called
   (for example) accountingMethodCurrent and accountingMethodSupported,
   to represent the HasAccountingMethod aggregation and its association
   class.

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   The former is a string attribute that defines the current accounting
   method used by this AccountingECAPolicyRule, while the latter
   defines a set of accounting methods, in the form of an accounting
   Capability, which this AccountingECAPolicyRule can advertise.

A.4.  TrafficInspectionECAPolicyRuleClass Definition

   The purpose of a TrafficInspectionECAPolicyRule is to define an I2NSF
   ECA Policy Rule that, based on a given context, can determine which
   traffic to examine on which devices, which information to collect
   from those devices, and how to collect that information.

   This class does NOT define the traffic inspection method(s) used.
   This is because this would effectively "enclose" this information
   within the TrafficInspectionECAPolicyRule. This has two drawbacks.
   First, other entities that need to use information from the
   TrafficInspection class(es) could not; they would have to associate
   with the TrafficInspectionECAPolicyRule class, and those other
   classes would not likely be interested in the
   TrafficInspectionECAPolicyRule. Second, the evolution of new traffic
   inspection methods should be independent of the
   TrafficInspectionECAPolicyRule; this cannot happen if the
   TrafficInspection class(es) are embedded in the
   TrafficInspectionECAPolicyRule. Hence, this document recommends the
   following design:

                                                  +------------------+
   +-------------------+1..n                   1..n|                  |
   |                   |/ \ HasTrafficInspection  \|      Traffic     |
   | TrafficInspection + A ----------+-------------+ InspectionMethod |
   |   ECAPolicyRule   |\ /          ^           / |                  |
   |                   |             |             +------------------+
   +-------------------+             |
                                     |
                        +------------+------------+
                        | TrafficInspectionDetail |
                        +------------+------------+
                                    / \ 0..n
                                     |
                                     | PolicyControlsTrafficInspection
                                     |
                                    / \
                                     A
                                    \ / 0..n
                          +----------+--------------+
                          | ManagementECAPolicyRule |
                          +-------------------------+

           Figure 13.  Modeling Traffic Inspection Mechanisms




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   This document only defines the TrafficInspectionECAPolicyRule; all
   other classes, and the aggregations, are defined in an external
   model. For completeness, descriptions of how the two aggregations
   are used are described below.

   Figure 13 defines an aggregation between the
   TrafficInspectionECAPolicyRule and an external class that defines
   one or more traffic inspection mechanisms. This decouples the
   implementation of traffic inspection mechanisms from how traffic
   inspection mechanisms are managed and used.

   Since different TrafficInspectionECAPolicyRules can use different
   traffic inspection mechanisms in different ways, the aggregation is
   realized as an association class. This enables the attributes and
   methods of the association class (i.e., TrafficInspectionDetail) to
   be used to define how a given TrafficInspectionMethod is used by a
   particular TrafficInspectionECAPolicyRule.

   Similarly, the PolicyControlsTrafficInspection aggregation defines
   Policy Rules to control the configuration of the
   TrafficInspectionDetail association class. This enables the entire
   traffic inspection process to be managed by ECA PolicyRules.

   Note: a data model MAY choose to collapse this design into a more
   efficient implementation. For example, a data model could define
   two attributes for the TrafficInspectionECAPolicyRule class, called
   (for example) trafficInspectionMethodCurrent and
   trafficInspectionMethodSupported, to represent the
   HasTrafficInspectionMethod aggregation and its association class.
   The former is a string attribute that defines the current traffic
   inspection method used by this TrafficInspectionECAPolicyRule,
   while the latter defines a set of traffic inspection methods, in
   the form of a traffic inspection Capability, which this
   TrafficInspectionECAPolicyRule can advertise.

A.5.  ApplyProfileECAPolicyRuleClass Definition

   The purpose of an ApplyProfileECAPolicyRule is to define an I2NSF
   ECA Policy Rule that, based on a given context, can apply a
   particular profile to specific traffic. The profile defines the
   security Capabilities for content security control and/or attack
   mitigation control; these will be described in sections 4.4 and
   4.5, respectively.

   This class does NOT define the set of Profiles used. This is
   because this would effectively "enclose" this information within
   the ApplyProfileECAPolicyRule. This has two drawbacks. First, other
   entities that need to use information from the Profile class(es)
   could not; they would have to associate with the




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   ApplyProfileECAPolicyRule class, and those other classes would not
   likely be interested in the ApplyProfileECAPolicyRule. Second, the
   evolution of new Profile classes should be independent of the
   ApplyProfileECAPolicyRule; this cannot happen if the Profile
   class(es) are embedded in the ApplyProfileECAPolicyRule. Hence,
   this document recommends the following design:

                                                       +-------------+
      +-------------------+ 1..n                  1..n |             |
      |                   |/ \  ProfileApplied        \|             |
      | ApplyProfile      + A -----------+-------------+   Profile   |
      |   ECAPolicyRule   |\ /           ^            /|             |
      |                   |              |             +-------------+
      +-------------------+              |
                                         |
                            +------------+---------+
                            | ProfileAppliedDetail |
                            +------------+---------+
                                        / \ 0..n
                                         |
                                         |
        PolicyControlsProfileApplication |
                                         |
                                        / \
                                         A
                                        \ / 0..n
                              +----------+--------------+
                              | ManagementECAPolicyRule |
                              +-------------------------+

           Figure 14.  Modeling Profile ApplicationMechanisms

   This document only defines the ApplyProfileECAPolicyRule; all other
   classes, and the aggregations, are defined in an external model.
   For completeness, descriptions of how the two aggregations are used
   are described below.

   Figure 14 defines an aggregation between the
   ApplyProfileECAPolicyRule and an external Profile class. This
   decouples the implementation of Profiles from how Profiles are used.

   Since different ApplyProfileECAPolicyRules can use different
   Profiles in different ways, the aggregation is realized as an
   association class. This enables the attributes and methods of the
   association class (i.e., ProfileAppliedDetail) to be used to define
   how a given Profile is used by a particular
   ApplyProfileECAPolicyRule.

   Similarly, the PolicyControlsProfileApplication aggregation defines
   policies to control the configuration of the ProfileAppliedDetail
   association class. This enables the application of Profiles to be
   managed and used by ECA PolicyRules.

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   Note: a data model MAY choose to collapse this design into a more
   efficient implementation. For example, a data model could define two
   attributes for the ApplyProfileECAPolicyRuleclass, called (for
   example) profileAppliedCurrent and profileAppliedSupported, to
   represent the ProfileApplied aggregation and its association class.
   The former is a string attribute that defines the current Profile
   used by this ApplyProfileECAPolicyRule, while the latter defines a
   set of Profiles, in the form of a Profile Capability, which this
   ApplyProfileECAPolicyRule can advertise.

A.6.  ApplySignatureECAPolicyRuleClass Definition

   The purpose of an ApplySignatureECAPolicyRule is to define an I2NSF
   ECA Policy Rule that, based on a given context, can determine which
   Signature object (e.g., an anti-virus file, or aURL filtering file,
   or a script) to apply to which traffic. The Signature object defines
   the security Capabilities for content security control and/or attack
   mitigation control; these will be described in sections 4.4 and 4.5,
   respectively.

   This class does NOT define the set of Signature objects used. This
   is because this would effectively "enclose" this information within
   the ApplySignatureECAPolicyRule. This has two drawbacks. First,
   other entities that need to use information from the Signature
   object class(es) could not; they would have to associate with the
   ApplySignatureECAPolicyRule class, and those other classes would not
   likely be interested in the ApplySignatureECAPolicyRule. Second, the
   evolution of new Signature object classes should be independent of
   the ApplySignatureECAPolicyRule; this cannot happen if the Signature
   object class(es) are embedded in the ApplySignatureECAPolicyRule.
   Hence, this document recommends the following design:

   This document only defines the ApplySignatureECAPolicyRule; all
   other classes, and the aggregations, are defined in an external
   model. For completeness, descriptions of how the two aggregations
   are used are described below.

   Figure 15 defines an aggregation between the
   ApplySignatureECAPolicyRule and an external Signature object class.
   This decouples the implementation of signature objects from how
   Signature objects are used.

   Since different ApplySignatureECAPolicyRules can use different
   Signature objects in different ways, the aggregation is realized as
   an association class. This enables the attributes and methods of the
   association class (i.e., SignatureAppliedDetail) to be used to
   define how a given Signature object is used by a particular
   ApplySignatureECAPolicyRule.




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                                                 +-------------+
    +---------------+ 1..n                  1..n |             |
    |               |/ \   SignatureApplied     \|             |
    | ApplySignature+ A ----------+--------------+  Signature  |
    | ECAPolicyRule |\ /          ^             /|             |
    |               |             |              +-------------+
    +---------------+             |
                                  |
                     +------------+-----------+
                     | SignatureAppliedDetail |
                     +------------+-----------+
                                 / \ 0..n
                                  |
                                  | PolicyControlsSignatureApplication
                                  |
                                 / \
                                  A
                                 \ / 0..n
                       +----------+--------------+
                       | ManagementECAPolicyRule |
                       +-------------------------+

         Figure 15.  Modeling Sginature Application Mechanisms

   Similarly, the PolicyControlsSignatureApplication aggregation
   defines policies to control the configuration of the
   SignatureAppliedDetail association class. This enables the
   application of the Signature object to be managed by policy.

   Note: a data model MAY choose to collapse this design into a more
   efficient implementation. For example, a data model could define
   two attributes for the ApplySignatureECAPolicyRule class, called
   (for example) signature signatureAppliedCurrent and
   signatureAppliedSupported, to represent the SignatureApplied
   aggregation and its association class. The former is a string
   attribute that defines the current Signature object used by this
   ApplySignatureECAPolicyRule, while the latter defines a set of
   Signature objects, in the form of a Signature Capability, which
   this ApplySignatureECAPolicyRule can advertise.













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Appendix B. Network Security Event Class Definitions

   This Appendix defines a preliminary set of Network Security Event
   classes, along with their attributes.

B.1.  UserSecurityEvent Class Description

   The purpose of this class is to represent Events that are initiated
   by a user, such as logon and logoff Events. Information in this
   Event may be used as part of a test to determine if the Condition
   clause in this ECA Policy Rule should be evaluated or not. Examples
   include user identification data and the type of connection used by
   the user.

   The UserSecurityEvent class defines the following attributes.

B.1.1.  The usrSecEventContent Attribute

   This is a mandatory string that contains the content of the
   UserSecurityEvent. The format of the content is specified in the
   usrSecEventFormat class attribute, and the type of Event is defined
   in the usrSecEventType class attribute. An example of the
   usrSecEventContent attribute is the string "hrAdmin", with the
   usrSecEventFormat set to 1 (GUID) and the usrSecEventType attribute
   set to 5 (new logon).

B.1.2.  The usrSecEventFormat Attribute

   This is a mandatory non-negative enumerated integer, which is used
   to specify the data type of the usrSecEventContent attribute. The
   content is specified in the usrSecEventContent class attribute, and
   the type of Event is defined in the usrSecEventType class attribute.
   An example of the usrSecEventContent attribute is the string
   "hrAdmin", with the usrSecEventFormat attribute set to 1 (GUID) and
   the usrSecEventType attribute set to 5 (new logon). Values include:

      0:  unknown
      1:  GUID (Generic Unique IDentifier)
      2:  UUID (Universal Unique IDentifier)
      3:  URI (Uniform Resource Identifier)
      4:  FQDN (Fully Qualified Domain Name)
      5:  FQPN (Fully Qualified Path Name)

B.1.3.  The usrSecEventType Attribute

   This is a mandatory non-negative enumerated integer, which is used
   to specify the type of Event that involves this user. The content
   and format are specified in the usrSecEventContent and
   usrSecEventFormat class attributes, respectively.




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   An example of the usrSecEventContent attribute is the string
   "hrAdmin", with the usrSecEventFormat attribute set to 1 (GUID), and
   the usrSecEventType attribute set to 5 (new logon). Values include:

      0:  unknown
      1:  new user created
      2:  new user group created
      3:  user deleted
      4:  user group deleted
      5:  user logon
      6:  user logoff
      7:  user access request
      8:  user access granted
      9:  user access violation

B.2.  DeviceSecurityEvent Class Description

   The purpose of a DeviceSecurityEvent is to represent Events that
   provide information from the Device that are important to I2NSF
   Security. Information in this Event may be used as part of a test
   to determine if the Condition clause in this ECA Policy Rule should
   be evaluated or not. Examples include alarms and various device
   statistics (e.g., a type of threshold that was exceeded), which may
   signal the need for further action.

   The DeviceSecurityEvent class defines the following attributes.

B.2.1.  The devSecEventContent Attribute

   This is a mandatory string that contains the content of the
   DeviceSecurityEvent. The format of the content is specified in the
   devSecEventFormat class attribute, and the type of Event is defined
   in the devSecEventType class attribute. An example of the
   devSecEventContent attribute is "alarm", with the devSecEventFormat
   attribute set to 1 (GUID), the devSecEventType attribute set to
   5 (new logon).

B.2.2.  The devSecEventFormat Attribute

   This is a mandatory non-negative enumerated integer, which is used
   to specify the data type of the devSecEventContent attribute.
   Values include:

      0:  unknown
      1:  GUID (Generic Unique IDentifier)
      2:  UUID (Universal Unique IDentifier)
      3:  URI (Uniform Resource Identifier)
      4:  FQDN (Fully Qualified Domain Name)
      5:  FQPN (Fully Qualified Path Name)




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B.2.3.  The devSecEventType Attribute

   This is a mandatory non-negative enumerated integer, which is used
   to specify the type of Event that was generated by this device.
   Values include:

      0:  unknown
      1:  communications alarm
      2:  quality of service alarm
      3:  processing error alarm
      4:  equipment error alarm
      5:  environmental error alarm

   Values 1-5 are defined in X.733. Additional types of errors may also
   be defined.

B.2.4.  The devSecEventTypeInfo[0..n] Attribute

   This is an optional array of strings, which is used to provide
   additional information describing the specifics of the Event
   generated by this Device. For example, this attribute could contain
   probable cause information in the first array, trend information in
   the second array, proposed repair actions in the third array, and
   additional information in the fourth array.

B.2.5.  The devSecEventTypeSeverity Attribute

   This is a mandatory non-negative enumerated integer, which is used
   to specify the perceived severity of the Event generated by this
   Device. Values (which are defined in X.733) include:

      0:  unknown
      1:  cleared
      2:  indeterminate
      3:  critical
      4:  major
      5:  minor
      6:  warning

B.3.  SystemSecurityEvent Class Description

   The purpose of a SystemSecurityEvent is to represent Events that
   are detected by the management system, instead of Events that are
   generated by a user or a device. Information in this Event may be
   used as part of a test to determine if the Condition clause in
   this ECA Policy Rule should be evaluated or not. Examples include
   an event issued by an analytics system that warns against a
   particular pattern of unknown user accesses, or an Event issued by
   a management system that represents a set of correlated and/or
   filtered Events.



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   The SystemSecurityEvent class defines the following attributes.

B.3.1.  The sysSecEventContent Attribute

   This is a mandatory string that contains the content of the
   SystemSecurityEvent. The format of the content is specified in the
   sysSecEventFormat class attribute, and the type of Event is defined
   in the sysSecEventType class attribute. An example of the
   sysSecEventContent attribute is the string "sysadmin3", with the
   sysSecEventFormat attribute set to 1 (GUID), and the sysSecEventType
   attribute set to 2 (audit log cleared).

B.3.2.  The sysSecEventFormat Attribute

   This is a mandatory non-negative enumerated integer, which is used
   to specify the data type of the sysSecEventContent attribute.
   Values include:

      0:  unknown
      1:  GUID (Generic Unique IDentifier)
      2:  UUID (Universal Unique IDentifier)
      3:  URI (Uniform Resource Identifier)
      4:  FQDN (Fully Qualified Domain Name)
      5:  FQPN (Fully Qualified Path Name)

B.3.3.  The sysSecEventType Attribute

   This is a mandatory non-negative enumerated integer, which is used
   to specify the type of Event that involves this device.
   Values include:

      0:  unknown
      1:  audit log written to
      2:  audit log cleared
      3:  policy created
      4:  policy edited
      5:  policy deleted
      6:  policy executed

B.4.  TimeSecurityEvent Class Description

   The purpose of a TimeSecurityEvent is to represent Events that are
   temporal in nature (e.g., the start or end of a period of time).
   Time events signify an individual occurrence, or a time period, in
   which a significant event happened. Information in this Event may be
   used as part of a test to determine if the Condition clause in this
   ECA Policy Rule should be evaluated or not. Examples include issuing
   an Event at a specific time to indicate that a particular resource
   should not be accessed, or that different authentication and
   authorization mechanisms should now be used (e.g., because it is now
   past regular business hours).


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   The TimeSecurityEvent class defines the following attributes.

B.4.1.  The timeSecEventPeriodBegin Attribute

   This is a mandatory DateTime attribute, and represents the beginning
   of a time period. It has a value that has a date and/or a time
   component (as in the Java or Python libraries).

B.4.2.  The timeSecEventPeriodEnd Attribute

   This is a mandatory DateTime attribute, and represents the end of a
   time period. It has a value that has a date and/or a time component
   (as in the Java or Python libraries). If this is a single Event
   occurence, and not a time period when the Event can occur, then the
   timeSecEventPeriodEnd attribute may be ignored.

B.4.3.  The timeSecEventTimeZone Attribute

   This is a mandatory string attribute, and defines the time zone that
   this Event occurred in using the format specified in ISO8601.

































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Appendix C. Network Security Condition Class Definitions

   This Appendix defines a preliminary set of Network Security Condition
   classes, along with their attributes.

C.1.  PacketSecurityCondition

   The purpose of this Class is to represent packet header information
   that can be used as part of a test to determine if the set of Policy
   Actions in this ECA Policy Rule should be executed or not. This class
   is abstract, and serves as the superclass of more detailed conditions
   that act on different types of packet formats. Its subclasses are
   shown in Figure 16, and are defined in the following sections.

                             +-------------------------+
                             | PacketSecurityCondition |
                             +------------+------------+
                                         / \
                                          |
                                          |
                 +---------+----------+---+-----+----------+
                 |         |          |         |          |
                 |         |          |         |          |
        +--------+-------+ | +--------+-------+ | +--------+-------+
        | PacketSecurity | | | PacketSecurity | | | PacketSecurity |
        |  MACCondition  | | | IPv4Condition  | | | IPv6Condition  |
        +----------------+ | +----------------+ | +----------------+
                           |                    |
                  +--------+-------+   +--------+-------+
                  |  TCPCondition  |   |  UDPCondition  |
                  +----------------+   +----------------+

   Figure 16. Network Security Info Sub-Model PacketSecurityCondition
              Class Extensions

C.1.1.  PacketSecurityMACCondition

   The purpose of this Class is to represent packet MAC packet header
   information that can be used as part of a test to determine if the
   set of Policy Actions in this ECA Policy Rule should be executed or
   not. This class is concrete, and defines the following attributes.

C.1.1.1.  The pktSecCondMACDest Attribute

   This is a mandatory string attribute, and defines the MAC
   destination address (6 octets long).

C.1.1.2.  The pktSecCondMACSrc Attribute

   This is a mandatory string attribute, and defines the MAC source
   address (6 octets long).


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C.1.1.3.  The pktSecCondMAC8021Q Attribute

   This is an optional string attribute, and defines the 802.1Q tag
   value (2 octets long). This defines VLAN membership and 802.1p
   priority values.

C.1.1.4.  The pktSecCondMACEtherType Attribute

   This is a mandatory string attribute, and defines the EtherType
   field (2 octets long). Values up to and including 1500 indicate the
   size of the payload in octets; values of 1536 and above define
   which protocol is encapsulated in the payload of the frame.

C.1.1.5.  The pktSecCondMACTCI Attribute

   This is an optional string attribute, and defines the Tag Control
   Information. This consists of a 3 bit user priority field, a drop
   eligible indicator (1 bit), and a VLAN identifier (12 bits).

C.1.2.  PacketSecurityIPv4Condition

   The purpose of this Class is to represent packet IPv4 packet header
   information that can be used as part of a test to determine if the
   set of Policy Actions in this ECA Policy Rule should be executed or
   not. This class is concrete, and defines the following attributes.

C.1.2.1.  The pktSecCondIPv4SrcAddr Attribute

   This is a mandatory string attribute, and defines the IPv4 Source
   Address (32 bits).

C.1.2.2.  The pktSecCondIPv4DestAddr Attribute

   This is a mandatory string attribute, and defines the IPv4
   Destination Address (32 bits).

C.1.2.3.  The pktSecCondIPv4ProtocolUsed Attribute

   This is a mandatory string attribute, and defines the protocol used
   in the data portion of the IP datagram (8 bits).

C.1.2.4.  The pktSecCondIPv4DSCP Attribute

   This is a mandatory string attribute, and defines the Differentiated
   Services Code Point field (6 bits).

C.1.2.5.  The pktSecCondIPv4ECN Attribute

   This is an optional string attribute, and defines the Explicit
   Congestion Notification field (2 bits).



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C.1.2.6.  The pktSecCondIPv4TotalLength Attribute

   This is a mandatory string attribute, and defines the total length
   of the packet (including header and data) in bytes (16 bits).

C.1.2.7.  The pktSecCondIPv4TTL Attribute

   This is a mandatory string attribute, and defines the Time To Live
   in seconds (8 bits).

C.1.3.  PacketSecurityIPv6Condition

   The purpose of this Class is to represent packet IPv6 packet header
   information that can be used as part of a test to determine if the
   set of Policy Actions in this ECA Policy Rule should be executed or
   not. This class is concrete, and defines the following attributes.

C.1.3.1.  The pktSecCondIPv6SrcAddr Attribute

   This is a mandatory string attribute, and defines the IPv6 Source
   Address (128 bits).

C.1.3.2.  The pktSecCondIPv6DestAddr Attribute

   This is a mandatory string attribute, and defines the IPv6
   Destination Address (128 bits).

C.1.3.3.  The pktSecCondIPv6DSCP Attribute

   This is a mandatory string attribute, and defines the Differentiated
   Services Code Point field (6 bits). It consists of the six most
   significant bits of the Traffic Class field in the IPv6 header.

C.1.3.4.  The pktSecCondIPv6ECN Attribute

   This is a mandatory string attribute, and defines the Explicit
   Congestion Notification field (2 bits). It consists of the two least
   significant bits of the Traffic Class field in the IPv6 header.

C.1.3.5.  The pktSecCondIPv6FlowLabel Attribute

   This is a mandatory string attribute, and defines an IPv6 flow
   label. This, in combination with the Source and Destination Address
   fields, enables efficient IPv6 flow classification by using only the
   IPv6 main header fields (20 bits).

C.1.3.6.  The pktSecCondIPv6PayloadLength Attribute

   This is a mandatory string attribute, and defines the total length
   of the packet (including the fixed and any extension headers, and
   data) in bytes (16 bits).


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C.1.3.7.  The pktSecCondIPv6NextHeader Attribute

   This is a mandatory string attribute, and defines the type of the
   next header (e.g., which extension header to use) (8 bits).

C.1.3.8.  The pktSecCondIPv6HopLimit Attribute

   This is a mandatory string attribute, and defines the maximum
   number of hops that this packet can traverse (8 bits).

C.1.4.  PacketSecurityTCPCondition

   The purpose of this Class is to represent packet TCP packet header
   information that can be used as part of a test to determine if the
   set of Policy Actions in this ECA Policy Rule should be executed or
   not. This class is concrete, and defines the following attributes.

C.1.4.1.  The pktSecCondTPCSrcPort Attribute

   This is a mandatory string attribute, and defines the Source Port
   number (16 bits).

C.1.4.2.  The pktSecCondTPCDestPort Attribute

   This is a mandatory string attribute, and defines the Destination
   Port number (16 bits).

C.1.4.3.  The pktSecCondTCPSeqNum Attribute

   This is a mandatory string attribute, and defines the sequence
   number (32 bits).

C.1.4.4.  The pktSecCondTCPFlags Attribute

   This is a mandatory string attribute, and defines the nine Control
   bit flags (9 bits).

C.1.5.  PacketSecurityUDPCondition

   The purpose of this Class is to represent packet UDP packet header
   information that can be used as part of a test to determine if the
   set of Policy Actions in this ECA Policy Rule should be executed or
   not. This class is concrete, and defines the following attributes.

C.1.5.1.1.  The pktSecCondUDPSrcPort Attribute

   This is a mandatory string attribute, and defines the UDP Source
   Port number (16 bits).





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C.1.5.1.2.  The pktSecCondUDPDestPort Attribute

   This is a mandatory string attribute, and defines the UDP
   Destination Port number (16 bits).

C.1.5.1.3.  The pktSecCondUDPLength Attribute

   This is a mandatory string attribute, and defines the length in
   bytes of the UDP header and data (16 bits).

C.2.  PacketPayloadSecurityCondition

   The purpose of this Class is to represent packet payload data that
   can be used as part of a test to determine if the set of Policy
   Actions in this ECA Policy Rule should be executed or not. Examples
   include a specific set of bytes in the packet payload.

C.3.  TargetSecurityCondition

   The purpose of this Class is to represent information about
   different targets of this policy (i.e., entities to which this
   Policy Rule should be applied), which can be used as part of a
   test to determine if the set of Policy Actions in this ECA Policy
   Rule should be executed or not. Examples include whether the
   targeted entities are playing the same role, or whether each
   device is administered by the same set of users, groups, or roles.
   This Class has several important subclasses, including:

      a. ServiceSecurityContextCondition is the superclass for all
         information that can be used in an ECA Policy Rule that
         specifies data about the type of service to be analyzed
         (e.g., the protocol type and port number)
      b. ApplicationSecurityContextCondition is the superclass for all
         information that can be used in a ECA Policy Rule that
         specifies data that identifies a particular application
         (including metadata, such as risk level)
      c. DeviceSecurityContextCondition is the superclass for all
         information that can be used in a ECA Policy Rule that
         specifies data about a device type and/or device OS that is
         being used

C.4.  UserSecurityCondition

   The purpose of this Class is to represent data about the user or
   group referenced in this ECA Policy Rule that can be used as part of
   a test to determine if the set of Policy Actions in this ECA Policy
   Rule should be evaluated or not. Examples include the user or group
   id used, the type of connection used, whether a given user or group
   is playing a particular role, or whether a given user or group has
   failed to login a particular number of times.



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C.5.  SecurityContextCondition

   The purpose of this Class is to represent security conditions that
   are part of a specific context, which can be used as part of a test
   to determine if the set of Policy Actions in this ECA Policy Rule
   should be evaluated or not. Examples include testing to determine
   if a particular pattern of security-related data have occurred, or
   if the current session state matches the expected session state.

C.6.  GenericContextSecurityCondition

   The purpose of this Class is to represent generic contextual
   information in which this ECA Policy Rule is being executed, which
   can be used as part of a test to determine if the set of Policy
   Actions in this ECA Policy Rule should be evaluated or not.
   Examples include geographic location and temporal information.




































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Appendix D. Network Security Action Class Definitions

   This Appendix defines a preliminary set of Network Security Action
   classes, along with their attributes.

D.1.  IngressAction

   The purpose of this Class is to represent actions performed on
   packets that enter an NSF. Examples include pass, dropp, or
   mirror traffic.

D.2.  EgressAction

   The purpose of this Class is to represent actions performed on
   packets that exit an NSF. Examples include pass, drop, or mirror
   traffic, signal, and encapsulate.

D.3.  ApplyProfileAction

   The purpose of this Class is to define the application of a profile
   to packets to perform content security and/or attack mitigation
   control.































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Appendix E. Geometric Model

   The geometric model defined in [Bas12] is summarized here. Note that
   our work has extended the work of [Bas12] to model ECA Policy Rules,
   instead of just condition-action Policy Rules. However, the
   geometric model in this Appendix is simplified in this version of
   this I-D, and is used to define just the CA part of the ECA model.

   All the actions available to the security function are well known
   and organized in an action set A.

   For filtering controls, the enforceable actions are either Allow or
   Deny, thus A={Allow,Deny}. For channel protection controls, they may
   be informally written as "enforce confidentiality", "enforce data
   authentication and integrity", and "enforce confidentiality and data
   authentication and integrity". However, these actions need to be
   instantiated to the technology used. For example, AH-transport mode
   and ESP-transport mode (and combinations thereof) are a more precise
   definition of channel protection actions.

   Conditions are typed predicates concerning a given selector. A
   selector describes the values that a protocol field may take. For
   example, the IP source selector is the set of all possible IP
   addresses, and it may also refer to the part of the packet where the
   values come from (e.g., the IP source selector refers to the IP
   source field in the IP header). Geometrically, a condition is the
   subset of its selector for which it evaluates to true. A condition
   on a given selector matches a packet if the value of the field
   referred to by the selector belongs to the condition.  For instance,
   in Figure 17 the conditions are s1 <= S1 (read as s1 subset of or
   equal to S1) and s2 <= S2 (s2 subset of or equal to S2), both s1 and
   s2 match the packet x1, while only s2 matches x2.

   To consider conditions in different selectors, the decision space is
   extended using the Cartesian product because distinct selectors
   refer to different fields, possibly from different protocol headers.
   Hence, given a policy-enabled element that allows the definition of
   conditions on the selectors S1, S2,..., Sm (where m is the number
   of Selectors available at the security control we want to model),
   its selection space is:

      S=S1 X S2 X ...  X Sm

   To consider conditions in different selectors, the decision space is
   extended using the Cartesian product because distinct selectors
   refer to different fields, possibly from different protocol headers.







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        S2 ^ Destination port
           |
           |      x2
           +......o
           |      .
           |      .
         --+.............+------------------------------------+
         | |      .      |                                    |
         s |      .      |                                    |
         e |      .      |            (rectangle)             |
         g |      .      |        condition clause (c)        |
         m |      .      |   here the action a is applied     |
         e |      .      |                                    |
         n |      .      |             x1=point=packet        |
         t +.............|.............o                      |
         | |      .      |             .                      |
         --+.............+------------------------------------+
           |      .      .             .                      .
           |      .      .             .                      .
     +------------+------+-------------+----------------------+------>
           |             |---- segment = condition in S1 -----|     S1
           +                                                 IP source

      Figure 17: Geometric representation of a rule r=(c,a) that
                 matches x1, but does not match x2.

   Accordingly, the condition clause c is a subset of S:

      c = s1 X s2 X ...  X sm <= S1 X S2 X ...  X Sm = S

   S represents the totality of the packets that are individually
   selectable by the security control to model when we use it to
   enforce a policy. Unfortunately, not all its subsets are valid
   condition clauses: only hyper-rectangles, or the union of
   hyper-rectangles (as they are Cartesian product of conditions),
   are valid. This is an intrinsic constraint of the policy
   language, as it specifies rules by defining a condition for each
   selector. Languages that allow specification of conditions as
   relations over more fields are modeled by the geometric model as
   more complex geometric shapes determined by the equations. However,
   the algorithms to compute intersections are much more sophisticated
   than intersection hyper-rectangles. Figure 17 graphically represents
   a condition clause c in a two-dimensional selection space.

   In the geometric model, a rule is expressed as r=(c,a), where c <= S
   (the condition clause is a subset of the selection space), and the
   action a belongs to A. Rule condition clauses match a packet (rules
   match a packet), if all the conditions forming the clauses match the
   packet. In Figure 17, the rule with condition clause c matches the
   packet x1 but not x2.



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   The rule set R is composed of n rules ri=(ci,ai).

   The decision criteria for the action to apply when a packet matches
   two or more rules is abstracted by means of the resolution strategy

      RS: Pow(R) -> A

   where Pow(R) is the power set of rules in R.

   Formally, given a set of rules, the resolution strategy maps all the
   possible subsets of rules to an action a in A. When no rule matches a
   packet, the security controls may select the default action d in A,
   if they support one.

   Resolution strategies may use, besides intrinsic rule data (i.e.,
   condition clause and action clause), also external data associated to
   each rule, such as priority, identity of the creator, and creation
   time.  Formally, every rule ri is associated by means of the
   function e(.):

      e(ri) = (ri,f1(ri),f2(ri),...)

   where E={fj:R -> Xj} (j=1,2,...) is the set that includes all
   functions that map rules to external attributes in Xj. However,
   E, e, and all the Xj are determined by the resolution strategy used.

   A policy is thus a function p: S -> A that connects each point of
   the selection space to an action taken from the action set A
   according to the rules in R. By also assuming RS(0)=d (where 0 is
   the empty-set) and RS(ri)=ai, the policy p can be described as:

      p(x)=RS(match{R(x)}).

   Therefore, in the geometric model, a policy is completely defined by
   the 4-tuple (R,RS,E,d): the rule set R, the resolution function RS,
   the set E of mappings to the external attributes, and the default
   action d.

   Note that, the geometric model also supports ECA paradigms by simply
   modeling events like an additional selector.













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Authors' Addresses
Liang Xia (Frank)
Huawei
101 Software Avenue, Yuhuatai District
Nanjing, Jiangsu  210012
China
Email: Frank.xialiang@huawei.com

John Strassner
Huawei
Email: John.sc.Strassner@huawei.com

Cataldo Basile
Politecnico di Torino
Corso Duca degli Abruzzi, 34
Torino, 10129
Italy
Email: cataldo.basile@polito.it

Diego R. Lopez
Telefonica I+D
Zurbaran, 12
Madrid,   28010
Spain
Phone: +34 913 129 041
Email: diego.r.lopez@telefonica.com



























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