    Internet Engineering Task Force (IETF)                   M. Jethanandani
    Request for Comments: 8519                                        VMware
    Category: Standards Track                                     S. Agarwal
    ISSN: 2070-1721                                      Cisco Systems, Inc.
                                                                    L. Huang
                                                                    D. Blair
                                                                  March 2019

            YANG Data Model for Network Access Control Lists (ACLs)

    Abstract

       This document defines a data model for Access Control Lists (ACLs).
       An ACL is a user-ordered set of rules used to configure the
       forwarding behavior in a device.  Each rule is used to find a match
       on a packet and define actions that will be performed on the packet.

    Status of This Memo

       This is an Internet Standards Track document.

       This document is a product of the Internet Engineering Task Force
       (IETF).  It represents the consensus of the IETF community.  It has
       received public review and has been approved for publication by the
       Internet Engineering Steering Group (IESG).  Further information on
       Internet Standards is available in Section 2 of RFC 7841.

       Information about the current status of this document, any errata,
       and how to provide feedback on it may be obtained at
       https://www.rfc-editor.org/info/rfc8519.

    Copyright Notice

       Copyright (c) 2019 IETF Trust and the persons identified as the
       document authors.  All rights reserved.

       This document is subject to BCP 78 and the IETF Trust's Legal
       Provisions Relating to IETF Documents
       (https://trustee.ietf.org/license-info) in effect on the date of
       publication of this document.  Please review these documents
       carefully, as they describe your rights and restrictions with respect
       to this document.  Code Components extracted from this document must
       include Simplified BSD License text as described in Section 4.e of
       the Trust Legal Provisions and are provided without warranty as
       described in the Simplified BSD License.

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    Table of Contents

       1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
         1.1.  Definitions and Acronyms  . . . . . . . . . . . . . . . .   3
         1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
         1.3.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .   4
       2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   4
       3.  Understanding ACL's Filters and Actions . . . . . . . . . . .   4
         3.1.  ACL Modules . . . . . . . . . . . . . . . . . . . . . . .   5
       4.  ACL YANG Models . . . . . . . . . . . . . . . . . . . . . . .   9
         4.1.  IETF Access Control List Module . . . . . . . . . . . . .   9
         4.2.  IETF Packet Fields Module . . . . . . . . . . . . . . . .  24
         4.3.  ACL Examples  . . . . . . . . . . . . . . . . . . . . . .  37
         4.4.  Port Range Usage and Other Examples . . . . . . . . . . .  39
       5.  Security Considerations . . . . . . . . . . . . . . . . . . .  42
       6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  43
         6.1.  URI Registration  . . . . . . . . . . . . . . . . . . . .  43
         6.2.  YANG Module Name Registration . . . . . . . . . . . . . .  44
       7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  44
         7.1.  Normative References  . . . . . . . . . . . . . . . . . .  44
         7.2.  Informative References  . . . . . . . . . . . . . . . . .  46
       Appendix A.  Extending ACL Model Examples . . . . . . . . . . . .  47
         A.1.  Example of a Company's Proprietary Module . . . . . . . .  47
         A.2.  Linux nftables  . . . . . . . . . . . . . . . . . . . . .  50
         A.3.  Ethertypes  . . . . . . . . . . . . . . . . . . . . . . .  51
       Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  60
       Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  60

    1.  Introduction

       An Access Control List (ACL) is one of the basic elements used to
       configure device-forwarding behavior.  It is used in many networking
       technologies such as Policy-Based Routing (PBR), firewalls, etc.

       An ACL is a user-ordered set of rules that is used to filter traffic
       on a networking device.  Each rule is represented by an Access
       Control Entry (ACE).

       Each ACE has a group of match criteria and a group of actions.

       The match criteria allow for the definition of packet headers and
       metadata, the contents of which must match the definitions.

       o  Packet header matches apply to fields visible in the packet such
          as address, Class of Service (CoS), or port number.

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       o  In case a vendor supports it, metadata matches apply to fields
          associated with the packet, that are not in the packet header,
          such as the input interface or length of the packet as received
          over the wire.

       The actions specify what to do with the packet when the matching
       criteria are met.  These actions are any operations that would apply
       to the packet, such as counting, policing, or simply forwarding.  The
       list of potential actions is unbounded depending on the capabilities
       of the networking devices.

       Access Control List is also widely known as ACL (pronounced as
       [ak-uh l]) or Access List.  In this document, Access Control List,
       ACL, and Access List are used interchangeably.

       The matching of filters and actions in an ACE/ACL is triggered only
       after the application/attachment of the ACL to an interface, a
       Virtual Routing and Forwarding (VRF) interface, a vty/tty session, a
       QoS policy, or routing protocols, amongst various other configuration
       attachment points.  Once attached, it is used for filtering traffic
       using the match criteria in the ACEs and taking appropriate action(s)
       that has been configured against that ACE.  In order to apply an ACL
       to any attachment point other than an interface, vendors would have
       to augment the ACL YANG model.

    1.1.  Definitions and Acronyms

       ACE: Access Control Entry

       ACL: Access Control List

       CoS: Class of Service

       DSCP: Differentiated Services Code Point

       ICMP: Internet Control Message Protocol

       IP: Internet Protocol

       IPv4: Internet Protocol version 4

       IPv6: Internet Protocol version 6

       MAC: Media Access Control

       PBR: Policy-Based Routing

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       TCP: Transmission Control Protocol

       UDP: User Datagram Protocol

    1.2.  Terminology

       The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
       "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
       "OPTIONAL" in this document are to be interpreted as described in
       BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
       capitals, as shown here.

    1.3.  Tree Diagram

       For a reference to the annotations used in the tree diagrams included
       in this document, please see "YANG Tree Diagrams" [RFC8340].

    2.  Problem Statement

       This document defines a YANG 1.1 data model [RFC7950] for the
       configuration of ACLs.  The model defines matching rules for commonly
       used protocols such as Ethernet, IPv4, IPv6, TCP, UDP, and ICMP.  If
       more protocols need to be supported in the future, this base model
       can be augmented.  An example of such an augmentation can be seen in
       Appendix A.

       ACL implementations in every device may vary greatly in terms of the
       filter constructs and actions that they support.  Therefore, this
       document proposes a model that can be augmented by standard
       extensions and vendor proprietary models.

    3.  Understanding ACL's Filters and Actions

       Although different vendors have different ACL data models, there is a
       common understanding of what an ACL is.  A network system usually has
       a list of ACLs, and each ACL contains an ordered list of rules, also
       known as ACEs.  Each ACE has a group of match criteria and a group of
       actions.  The match criteria allows for definition of the contents of
       the packet headers or metadata, if supported by the vendor.  Packet
       header matching applies to fields visible in the packet such as
       address, CoS, or port number.  Metadata matching applies to fields
       associated with the packet, that are not in the packet header, such
       as the input interface, packet length, or source or destination
       prefix length.  The actions can be any sort of operation from logging
       to rate-limiting or dropping to simply forwarding.  Actions on the
       first matching ACE are applied with no processing of subsequent ACEs.

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       The model also includes a container to hold overall operational state
       for each ACL and for each ACE.  One ACL can be applied to multiple
       targets within the device, such as the interface of a networking
       device, applications or features running in the device, etc.  When
       applied to interfaces of a networked device, distinct ACLs are
       defined for the ingress (input) or egress (output) interface.

       This document tries to address the commonalities between all vendors
       and creates a common model, which can be augmented with proprietary
       models.  The base model is simple in design, and we hope to achieve
       enough flexibility for each vendor to extend the base model.

       The use of feature statements in the model allows vendors to
       advertise match rules they are capable and willing to support.  There
       are two sets of feature statements a device needs to advertise.  The
       first set of feature statements specifies the capability of the
       device.  These include features such as "Device can support matching
       on Ethernet headers" or "Device can support matching on IPv4
       headers".  The second set of feature statements specifies the
       combinations of headers the device is willing to support.  These
       include features such as "Plain IPv6 ACL supported" or "Ethernet,
       IPv4 and IPv6 ACL combinations supported".

    3.1.  ACL Modules

       There are two YANG modules in the model.  The first module, "ietf-
       access-control-list", defines generic ACL aspects that are common to
       all ACLs regardless of their type or vendor.  In effect, the module
       can be viewed as providing a generic ACL "superclass".  It imports
       the second module, "ietf-packet-fields".  The match container in
       "ietf-access-control-list" uses groupings in "ietf-packet-fields" to
       specify match fields such as port numbers or protocols.  The
       combination of 'if-feature' checks and 'must' statements allows for
       the selection of relevant match fields that a user can define rules
       for.

       If there is a need to define a new "matches" choice, such as IP Flow
       Information Export (IPFIX) [RFC7011], the container "matches" can be
       augmented.

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       module: ietf-access-control-list
         +--rw acls
            +--rw acl* [name]
            |  +--rw name    string
            |  +--rw type?   acl-type
            |  +--rw aces
            |     +--rw ace* [name]
            |        +--rw name          string
            |        +--rw matches
            |        |  +--rw (l2)?
            |        |  |  +--:(eth)
            |        |  |     +--rw eth {match-on-eth}?
            |        |  |        +--rw destination-mac-address?
            |        |  |        |       yang:mac-address
            |        |  |        +--rw destination-mac-address-mask?
            |        |  |        |       yang:mac-address
            |        |  |        +--rw source-mac-address?
            |        |  |        |       yang:mac-address
            |        |  |        +--rw source-mac-address-mask?
            |        |  |        |       yang:mac-address
            |        |  |        +--rw ethertype?
            |        |  |                eth:ethertype
            |        |  +--rw (l3)?
            |        |  |  +--:(ipv4)
            |        |  |  |  +--rw ipv4 {match-on-ipv4}?
            |        |  |  |     +--rw dscp?
            |        |  |  |     |       inet:dscp
            |        |  |  |     +--rw ecn?
            |        |  |  |     |       uint8
            |        |  |  |     +--rw length?
            |        |  |  |     |       uint16
            |        |  |  |     +--rw ttl?
            |        |  |  |     |       uint8
            |        |  |  |     +--rw protocol?
            |        |  |  |     |       uint8
            |        |  |  |     +--rw ihl?
            |        |  |  |     |       uint8
            |        |  |  |     +--rw flags?
            |        |  |  |     |       bits
            |        |  |  |     +--rw offset?
            |        |  |  |     |       uint16
            |        |  |  |     +--rw identification?
            |        |  |  |     |       uint16
            |        |  |  |     +--rw (destination-network)?
            |        |  |  |     |  +--:(destination-ipv4-network)
            |        |  |  |     |     +--rw destination-ipv4-network?
            |        |  |  |     |             inet:ipv4-prefix

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            |        |  |  |     +--rw (source-network)?
            |        |  |  |        +--:(source-ipv4-network)
            |        |  |  |           +--rw source-ipv4-network?
            |        |  |  |                   inet:ipv4-prefix
            |        |  |  +--:(ipv6)
            |        |  |     +--rw ipv6 {match-on-ipv6}?
            |        |  |        +--rw dscp?
            |        |  |        |       inet:dscp
            |        |  |        +--rw ecn?
            |        |  |        |       uint8
            |        |  |        +--rw length?
            |        |  |        |       uint16
            |        |  |        +--rw ttl?
            |        |  |        |       uint8
            |        |  |        +--rw protocol?
            |        |  |        |       uint8
            |        |  |        +--rw (destination-network)?
            |        |  |        |  +--:(destination-ipv6-network)
            |        |  |        |     +--rw destination-ipv6-network?
            |        |  |        |             inet:ipv6-prefix
            |        |  |        +--rw (source-network)?
            |        |  |        |  +--:(source-ipv6-network)
            |        |  |        |     +--rw source-ipv6-network?
            |        |  |        |             inet:ipv6-prefix
            |        |  |        +--rw flow-label?
            |        |  |                inet:ipv6-flow-label
            |        |  +--rw (l4)?
            |        |  |  +--:(tcp)
            |        |  |  |  +--rw tcp {match-on-tcp}?
            |        |  |  |     +--rw sequence-number?          uint32
            |        |  |  |     +--rw acknowledgement-number?   uint32
            |        |  |  |     +--rw data-offset?              uint8
            |        |  |  |     +--rw reserved?                 uint8
            |        |  |  |     +--rw flags?                    bits
            |        |  |  |     +--rw window-size?              uint16
            |        |  |  |     +--rw urgent-pointer?           uint16
            |        |  |  |     +--rw options?                  binary
            |        |  |  |     +--rw source-port
            |        |  |  |     |  +--rw (source-port)?
            |        |  |  |     |     +--:(range-or-operator)
            |        |  |  |     |        +--rw (port-range-or-operator)?
            |        |  |  |     |           +--:(range)
            |        |  |  |     |           |  +--rw lower-port
            |        |  |  |     |           |  |       inet:port-number
            |        |  |  |     |           |  +--rw upper-port
            |        |  |  |     |           |          inet:port-number
            |        |  |  |     |           +--:(operator)

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            |        |  |  |     |              +--rw operator?     operator
            |        |  |  |     |              +--rw port
            |        |  |  |     |                      inet:port-number
            |        |  |  |     +--rw destination-port
            |        |  |  |        +--rw (destination-port)?
            |        |  |  |           +--:(range-or-operator)
            |        |  |  |              +--rw (port-range-or-operator)?
            |        |  |  |                 +--:(range)
            |        |  |  |                 |  +--rw lower-port
            |        |  |  |                 |  |       inet:port-number
            |        |  |  |                 |  +--rw upper-port
            |        |  |  |                 |          inet:port-number
            |        |  |  |                 +--:(operator)
            |        |  |  |                    +--rw operator?     operator
            |        |  |  |                    +--rw port
            |        |  |  |                            inet:port-number
            |        |  |  +--:(udp)
            |        |  |  |  +--rw udp {match-on-udp}?
            |        |  |  |     +--rw length?             uint16
            |        |  |  |     +--rw source-port
            |        |  |  |     |  +--rw (source-port)?
            |        |  |  |     |     +--:(range-or-operator)
            |        |  |  |     |        +--rw (port-range-or-operator)?
            |        |  |  |     |           +--:(range)
            |        |  |  |     |           |  +--rw lower-port
            |        |  |  |     |           |  |       inet:port-number
            |        |  |  |     |           |  +--rw upper-port
            |        |  |  |     |           |          inet:port-number
            |        |  |  |     |           +--:(operator)
            |        |  |  |     |              +--rw operator?     operator
            |        |  |  |     |              +--rw port
            |        |  |  |     |                      inet:port-number
            |        |  |  |     +--rw destination-port
            |        |  |  |        +--rw (destination-port)?
            |        |  |  |           +--:(range-or-operator)
            |        |  |  |              +--rw (port-range-or-operator)?
            |        |  |  |                 +--:(range)
            |        |  |  |                 |  +--rw lower-port
            |        |  |  |                 |  |       inet:port-number
            |        |  |  |                 |  +--rw upper-port
            |        |  |  |                 |          inet:port-number
            |        |  |  |                 +--:(operator)
            |        |  |  |                    +--rw operator?     operator
            |        |  |  |                    +--rw port
            |        |  |  |                            inet:port-number
            |        |  |  +--:(icmp)

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            |        |  |     +--rw icmp {match-on-icmp}?
            |        |  |        +--rw type?             uint8
            |        |  |        +--rw code?             uint8
            |        |  |        +--rw rest-of-header?   binary
            |        |  +--rw egress-interface?    if:interface-ref
            |        |  +--rw ingress-interface?   if:interface-ref
            |        +--rw actions
            |        |  +--rw forwarding    identityref
            |        |  +--rw logging?      identityref
            |        +--ro statistics {acl-aggregate-stats}?
            |           +--ro matched-packets?   yang:counter64
            |           +--ro matched-octets?    yang:counter64
            +--rw attachment-points
               +--rw interface* [interface-id] {interface-attachment}?
                  +--rw interface-id    if:interface-ref
                  +--rw ingress
                  |  +--rw acl-sets
                  |     +--rw acl-set* [name]
                  |        +--rw name              -> /acls/acl/name
                  |        +--ro ace-statistics* [name] {interface-stats}?
                  |           +--ro name
                  |           |       -> /acls/acl/aces/ace/name
                  |           +--ro matched-packets?   yang:counter64
                  |           +--ro matched-octets?    yang:counter64
                  +--rw egress
                     +--rw acl-sets
                        +--rw acl-set* [name]
                           +--rw name              -> /acls/acl/name
                           +--ro ace-statistics* [name] {interface-stats}?
                              +--ro name
                              |       -> /acls/acl/aces/ace/name
                              +--ro matched-packets?   yang:counter64
                              +--ro matched-octets?    yang:counter64

    4.  ACL YANG Models

    4.1.  IETF Access Control List Module

       The "ietf-access-control-list" module defines the "acls" container
       that has a list of each "acl".  Each "acl" has information
       identifying the access list by a name ("name") and a list ("aces") of
       rules associated with the "name".  Each of the entries in the list
       ("aces"), indexed by the string "name", has containers defining
       "matches" and "actions".

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       The model defines several ACL types and actions in the form of
       identities and features.  Features are used by implementors to select
       the ACL types the system can support, and identities are used to
       validate the types that have been selected.  These types are
       implicitly inherited by the "ace", thus safeguarding against
       misconfiguration of "ace" types in an "acl".

       The "matches" define criteria used to identify patterns in "ietf-
       packet-fields".  The choice statements within the match container
       allow for the selection of one header within each of "l2", "l3", or
       "l4" headers.  The "actions" define the behavior to undertake once a
       "match" has been identified.  In addition to permit and deny actions,
       a logging option allows for a match to be logged that can later be
       used to determine which rule was matched upon.  The model also
       defines the ability for ACLs to be attached to a particular
       interface.

       Statistics in the ACL can be collected for an "ace" or for an
       "interface".  The feature statements defined for statistics can be
       used to determine whether statistics are being collected per "ace" or
       per "interface".

       This module imports definitions from "Common YANG Data Types"
       [RFC6991] and "A YANG Data Model for Interface Management" [RFC8343].

    <CODE BEGINS> file "ietf-access-control-list@2019-03-04.yang"

    module ietf-access-control-list {
      yang-version 1.1;
      namespace "urn:ietf:params:xml:ns:yang:ietf-access-control-list";
      prefix acl;

      import ietf-yang-types {
        prefix yang;
        reference
          "RFC 6991 - Common YANG Data Types.";
      }

      import ietf-packet-fields {
        prefix pf;
        reference
          "RFC 8519 - YANG Data Model for Network Access Control
                      Lists (ACLs).";
      }

      import ietf-interfaces {
        prefix if;
        reference

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          "RFC 8343 - A YANG Data Model for Interface Management.";
      }

      organization
        "IETF NETMOD (Network Modeling) Working Group.";

      contact
        "WG Web:  <https://datatracker.ietf.org/wg/netmod/>
         WG List: netmod@ietf.org

         Editor: Mahesh Jethanandani
                 mjethanandani@gmail.com
         Editor: Lisa Huang
                 huangyi_99@yahoo.com
         Editor: Sonal Agarwal
                 sagarwal12@gmail.com
         Editor: Dana Blair
                 dana@blairhome.com";

      description
        "This YANG module defines a component that describes the
         configuration and monitoring of Access Control Lists (ACLs).

         The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
         'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
         'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
         are to be interpreted as described in BCP 14 (RFC 2119)
         (RFC 8174) when, and only when, they appear in all
         capitals, as shown here.

         Copyright (c) 2019 IETF Trust and the persons identified as
         the document authors.  All rights reserved.

         Redistribution and use in source and binary forms, with or
         without modification, is permitted pursuant to, and subject
         to the license terms contained in, the Simplified BSD
         License set forth in Section 4.c of the IETF Trust's Legal
         Provisions Relating to IETF Documents
         (http://trustee.ietf.org/license-info).

         This version of this YANG module is part of RFC 8519; see
         the RFC itself for full legal notices.";

      revision 2019-03-04 {
        description
          "Initial version.";
        reference
          "RFC 8519: YANG Data Model for Network Access Control

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                     Lists (ACLs).";
      }

      /*
       * Identities
       */
      /*
       * Forwarding actions for a packet
       */

      identity forwarding-action {
        description
          "Base identity for actions in the forwarding category.";
      }

      identity accept {
        base forwarding-action;
        description
          "Accept the packet.";
      }

      identity drop {
        base forwarding-action;
        description
          "Drop packet without sending any ICMP error message.";
      }

      identity reject {
        base forwarding-action;
        description
          "Drop the packet and send an ICMP error message to the source.";
      }

      /*
       * Logging actions for a packet
       */

      identity log-action {
        description
          "Base identity for defining the destination for logging
           actions.";
      }

      identity log-syslog {
        base log-action;
        description
          "System log (syslog) the information for the packet.";
      }

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      identity log-none {
        base log-action;
        description
          "No logging for the packet.";
      }

      /*
       * ACL type identities
       */

      identity acl-base {
        description
          "Base Access Control List type for all Access Control List type
           identifiers.";
      }

      identity ipv4-acl-type {
        base acl:acl-base;
        if-feature "ipv4";
        description
          "An ACL that matches on fields from the IPv4 header
           (e.g., IPv4 destination address) and Layer 4 headers (e.g., TCP
           destination port).  An ACL of type ipv4 does not contain
           matches on fields in the Ethernet header or the IPv6 header.";
      }

      identity ipv6-acl-type {
        base acl:acl-base;
        if-feature "ipv6";
        description
          "An ACL that matches on fields from the IPv6 header
           (e.g., IPv6 destination address) and Layer 4 headers (e.g., TCP
           destination port).  An ACL of type ipv6 does not contain
           matches on fields in the Ethernet header or the IPv4 header.";
      }

      identity eth-acl-type {
        base acl:acl-base;
        if-feature "eth";
        description
          "An ACL that matches on fields in the Ethernet header,
           like 10/100/1000baseT or a Wi-Fi Access Control List.  An ACL
           of type ethernet does not contain matches on fields in the
           IPv4 header, the IPv6 header, or Layer 4 headers.";
      }

      identity mixed-eth-ipv4-acl-type {
        base acl:eth-acl-type;

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        base acl:ipv4-acl-type;
        if-feature "mixed-eth-ipv4";
        description
          "An ACL that contains a mix of entries that match
           on fields in Ethernet headers and in IPv4 headers.
           Matching on Layer 4 header fields may also exist in the
           list.";
      }

      identity mixed-eth-ipv6-acl-type {
        base acl:eth-acl-type;
        base acl:ipv6-acl-type;
        if-feature "mixed-eth-ipv6";
        description
          "An ACL that contains a mix of entries that match on fields
           in Ethernet headers and in IPv6 headers.  Matching
           on Layer 4 header fields may also exist in the list.";
      }

      identity mixed-eth-ipv4-ipv6-acl-type {
        base acl:eth-acl-type;
        base acl:ipv4-acl-type;
        base acl:ipv6-acl-type;
        if-feature "mixed-eth-ipv4-ipv6";
        description
          "An ACL that contains a mix of entries that
           match on fields in Ethernet headers, IPv4 headers, and IPv6
           headers.  Matching on Layer 4 header fields may also exist
           in the list.";
      }

      /*
       * Features
       */

      /*
       * Features supported by device
       */
      feature match-on-eth {
        description
          "The device can support matching on Ethernet headers.";
      }

      feature match-on-ipv4 {
        description
          "The device can support matching on IPv4 headers.";
      }

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      feature match-on-ipv6 {
        description
          "The device can support matching on IPv6 headers.";
      }

      feature match-on-tcp {
        description
          "The device can support matching on TCP headers.";
      }

      feature match-on-udp {
        description
          "The device can support matching on UDP headers.";
      }

      feature match-on-icmp {
        description
          "The device can support matching on ICMP (v4 and v6) headers.";
      }

      /*
       * Header classifications combinations supported by
       * device
       */

      feature eth {
        if-feature "match-on-eth";
        description
          "Plain Ethernet ACL supported.";
      }

      feature ipv4 {
        if-feature "match-on-ipv4";
        description
          "Plain IPv4 ACL supported.";
      }

      feature ipv6 {
        if-feature "match-on-ipv6";
        description
          "Plain IPv6 ACL supported.";
      }

      feature mixed-eth-ipv4 {
        if-feature "match-on-eth and match-on-ipv4";
        description
          "Ethernet and IPv4 ACL combinations supported.";
      }

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      feature mixed-eth-ipv6 {
        if-feature "match-on-eth and match-on-ipv6";
        description
          "Ethernet and IPv6 ACL combinations supported.";
      }

      feature mixed-eth-ipv4-ipv6 {
        if-feature
          "match-on-eth and match-on-ipv4
           and match-on-ipv6";
        description
          "Ethernet, IPv4, and IPv6 ACL combinations supported.";
      }

      /*
       * Stats Features
       */
      feature interface-stats {
        description
          "ACL counters are available and reported only per interface.";
      }

      feature acl-aggregate-stats {
        description
          "ACL counters are aggregated over all interfaces and reported
           only per ACL entry.";
      }

      /*
       * Attachment point features
       */
      feature interface-attachment {
        description
          "ACLs are set on interfaces.";
      }

      /*
       * Typedefs
       */
      typedef acl-type {
        type identityref {
          base acl-base;
        }
        description
          "This type is used to refer to an ACL type.";
      }

      /*

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       * Groupings
       */
      grouping acl-counters {
        description
          "Common grouping for ACL counters.";
        leaf matched-packets {
          type yang:counter64;
          config false;
          description
            "Count of the number of packets matching the current ACL
             entry.

             An implementation should provide this counter on a
             per-interface, per-ACL-entry basis if possible.

             If an implementation only supports ACL counters on a per-
             entry basis (i.e., not broken out per interface), then the
             value should be equal to the aggregate count across all
             interfaces.

             An implementation that provides counters on a per-entry, per-
             interface basis is not required to also provide an aggregate
             count, e.g., per entry -- the user is expected to be able to
             implement the required aggregation if such a count is
             needed.";
        }

        leaf matched-octets {
          type yang:counter64;
          config false;
          description
            "Count of the number of octets (bytes) matching the current
             ACL entry.

             An implementation should provide this counter on a
             per-interface, per-ACL-entry basis if possible.

             If an implementation only supports ACL counters per entry
             (i.e., not broken out per interface), then the value
             should be equal to the aggregate count across all interfaces.

             An implementation that provides counters per entry per
             interface is not required to also provide an aggregate count,
             e.g., per entry -- the user is expected to be able to
             implement the required aggregation if such a count is needed.";
        }
      }

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      /*
       * Configuration and monitoring data nodes
       */

      container acls {
        description
          "This is a top-level container for Access Control Lists.
           It can have one or more acl nodes.";
        list acl {
          key "name";
          description
            "An ACL is an ordered list of ACEs.  Each ACE has a
             list of match criteria and a list of actions.
             Since there are several kinds of ACLs implemented
             with different attributes for different vendors,
             this model accommodates customizing ACLs for
             each kind and for each vendor.";
          leaf name {
            type string {
              length "1..64";
            }
            description
              "The name of the access list.  A device MAY further
               restrict the length of this name; space and special
               characters are not allowed.";
          }
          leaf type {
            type acl-type;
            description
              "Type of ACL.  Indicates the primary intended
               type of match criteria (e.g., Ethernet, IPv4, IPv6, mixed,
               etc.) used in the list instance.";
          }
          container aces {
            description
              "The aces container contains one or more ACE nodes.";
            list ace {
              key "name";
              ordered-by user;
              description
                "List of ACEs.";
              leaf name {
                type string {
                  length "1..64";
                }
                description
                  "A unique name identifying this ACE.";
              }

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              container matches {
                description
                  "The rules in this set determine what fields will be
                   matched upon before any action is taken on them.
                   The rules are selected based on the feature set
                   defined by the server and the acl-type defined.
                   If no matches are defined in a particular container,
                   then any packet will match that container.  If no
                   matches are specified at all in an ACE, then any
                   packet will match the ACE.";

                choice l2 {
                  container eth {
                    when "derived-from-or-self(/acls/acl/type, "
                       + "'acl:eth-acl-type')";
                    if-feature "match-on-eth";
                    uses pf:acl-eth-header-fields;
                    description
                      "Rule set that matches Ethernet headers.";
                  }
                  description
                    "Match Layer 2 headers, for example, Ethernet
                     header fields.";
                }

                choice l3 {
                  container ipv4 {
                    when "derived-from-or-self(/acls/acl/type, "
                       + "'acl:ipv4-acl-type')";
                    if-feature "match-on-ipv4";
                    uses pf:acl-ip-header-fields;
                    uses pf:acl-ipv4-header-fields;
                    description
                      "Rule set that matches IPv4 headers.";
                  }

                  container ipv6 {
                    when "derived-from-or-self(/acls/acl/type, "
                       + "'acl:ipv6-acl-type')";
                    if-feature "match-on-ipv6";
                    uses pf:acl-ip-header-fields;
                    uses pf:acl-ipv6-header-fields;
                    description
                      "Rule set that matches IPv6 headers.";
                  }
                  description
                    "Choice of either IPv4 or IPv6 headers";
                }

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                choice l4 {
                  container tcp {
                    if-feature "match-on-tcp";
                    uses pf:acl-tcp-header-fields;
                    container source-port {
                      choice source-port {
                        case range-or-operator {
                          uses pf:port-range-or-operator;
                          description
                            "Source port definition from range or
                             operator.";
                        }
                        description
                          "Choice of source port definition using
                           range/operator or a choice to support future
                           'case' statements, such as one enabling a
                           group of source ports to be referenced.";
                      }
                      description
                        "Source port definition.";
                    }
                    container destination-port {
                      choice destination-port {
                        case range-or-operator {
                          uses pf:port-range-or-operator;
                          description
                            "Destination port definition from range or
                             operator.";
                        }
                        description
                          "Choice of destination port definition using
                           range/operator or a choice to support future
                           'case' statements, such as one enabling a
                           group of destination ports to be referenced.";
                      }
                      description
                        "Destination port definition.";
                    }
                    description
                      "Rule set that matches TCP headers.";
                  }

                  container udp {
                    if-feature "match-on-udp";
                    uses pf:acl-udp-header-fields;
                    container source-port {
                      choice source-port {
                        case range-or-operator {

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                          uses pf:port-range-or-operator;
                          description
                            "Source port definition from range or
                             operator.";
                        }
                        description
                          "Choice of source port definition using
                           range/operator or a choice to support future
                           'case' statements, such as one enabling a
                           group of source ports to be referenced.";
                      }
                      description
                        "Source port definition.";
                    }
                    container destination-port {
                      choice destination-port {
                        case range-or-operator {
                          uses pf:port-range-or-operator;
                          description
                            "Destination port definition from range or
                             operator.";
                        }
                        description
                          "Choice of destination port definition using
                           range/operator or a choice to support future
                           'case' statements, such as one enabling a
                           group of destination ports to be referenced.";
                      }
                      description
                        "Destination port definition.";
                    }
                    description
                      "Rule set that matches UDP headers.";
                  }

                  container icmp {
                    if-feature "match-on-icmp";
                    uses pf:acl-icmp-header-fields;
                    description
                      "Rule set that matches ICMP headers.";
                  }
                  description
                    "Choice of TCP, UDP, or ICMP headers.";
                }

                leaf egress-interface {
                  type if:interface-ref;
                  description

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                    "Egress interface.  This should not be used if this ACL
                     is attached as an egress ACL (or the value should
                     equal the interface to which the ACL is attached).";
                }

                leaf ingress-interface {
                  type if:interface-ref;
                  description
                    "Ingress interface.  This should not be used if this ACL
                     is attached as an ingress ACL (or the value should
                     equal the interface to which the ACL is attached).";
                }
              }

              container actions {
                description
                  "Definition of actions for this ace entry.";
                leaf forwarding {
                  type identityref {
                    base forwarding-action;
                  }
                  mandatory true;
                  description
                    "Specifies the forwarding action per ace entry.";
                }

                leaf logging {
                  type identityref {
                    base log-action;
                  }
                  default "log-none";
                  description
                    "Specifies the log action and destination for
                     matched packets.  Default value is not to log the
                     packet.";
                }
              }
              container statistics {
                if-feature "acl-aggregate-stats";
                config false;
                description
                  "Statistics gathered across all attachment points for the
                   given ACL.";
                uses acl-counters;
              }
            }
          }
        }

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        container attachment-points {
          description
            "Enclosing container for the list of
             attachment points on which ACLs are set.";
          /*
           * Groupings
           */
          grouping interface-acl {
            description
              "Grouping for per-interface ingress ACL data.";
            container acl-sets {
              description
                "Enclosing container for the list of ingress ACLs on the
                 interface.";
              list acl-set {
                key "name";
                ordered-by user;
                description
                  "List of ingress ACLs on the interface.";
                leaf name {
                  type leafref {
                    path "/acls/acl/name";
                  }
                  description
                    "Reference to the ACL name applied on the ingress.";
                }
                list ace-statistics {
                  if-feature "interface-stats";
                  key "name";
                  config false;
                  description
                    "List of ACEs.";
                  leaf name {
                    type leafref {
                      path "/acls/acl/aces/ace/name";
                    }
                    description
                      "Name of the ace entry.";
                  }
                  uses acl-counters;
                }
              }
            }
          }

          list interface {
            if-feature "interface-attachment";
            key "interface-id";

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            description
              "List of interfaces on which ACLs are set.";

            leaf interface-id {
              type if:interface-ref;
              description
                "Reference to the interface id list key.";
            }

            container ingress {
              uses interface-acl;
              description
                "The ACLs applied to the ingress interface.";
            }
            container egress {
              uses interface-acl;
              description
                "The ACLs applied to the egress interface.";
            }
          }
        }
      }
    }

    <CODE ENDS>

    4.2.  IETF Packet Fields Module

       The packet fields module defines the necessary groups for matching on
       fields in the packet including Ethernet, IPv4, IPv6, and transport-
       layer fields.  The "type" node determines which of these fields get
       included for any given ACL with the exception of TCP, UDP, and ICMP
       header fields.  Those fields can be used in conjunction with any of
       the above Layer 2 or Layer 3 fields.

       Since the number of match criteria are very large, the base
       specification does not include these directly but references them by
       the 'uses' statement to keep the base module simple.  In case more
       match conditions are needed, those can be added by augmenting choices
       within container "matches" in the ietf-access-control-list.yang data
       model.

       This module imports definitions from "Common YANG Data Types"
       [RFC6991] and references "Internet Protocol" [RFC791], "Internet
       Control Message Protocol" [RFC792], "Transmission Control Protocol"
       [RFC793], "Definition of the Differentiated Services Field (DS Field)
       in the IPv4 and IPv6 Headers" [RFC2474], "The Addition of Explicit
       Congestion Notification (ECN) to IP" [RFC3168], "IPv6 Scoped Address

    Jethanandani, et al.         Standards Track                   [Page 24]

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       Architecture" [RFC4007], "IP Version 6 Addressing Architecture"
       [RFC4291], "A Recommendation for IPv6 Address Text Representation"
       [RFC5952], and "Internet Protocol, Version 6 (IPv6) Specification"
       [RFC8200].

    <CODE BEGINS> file "ietf-packet-fields@2019-03-04.yang"

    module ietf-packet-fields {
      yang-version 1.1;
      namespace "urn:ietf:params:xml:ns:yang:ietf-packet-fields";
      prefix packet-fields;

      import ietf-inet-types {
        prefix inet;
        reference
          "RFC 6991 - Common YANG Data Types.";
      }

      import ietf-yang-types {
        prefix yang;
        reference
          "RFC 6991 - Common YANG Data Types.";
      }

      import ietf-ethertypes {
        prefix eth;
        reference
          "RFC 8519 - YANG Data Model for Network Access Control
                      Lists (ACLs).";
      }

      organization
        "IETF NETMOD (Network Modeling) Working Group.";

      contact
        "WG Web:  <https://datatracker.ietf.org/wg/netmod/>
         WG List: netmod@ietf.org

         Editor: Mahesh Jethanandani
                 mjethanandani@gmail.com
         Editor: Lisa Huang
                 huangyi_99@yahoo.com
         Editor: Sonal Agarwal
                 sagarwal12@gmail.com
         Editor: Dana Blair
                 dana@blairhome.com";

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      description
        "This YANG module defines groupings that are used by
         the ietf-access-control-list YANG module.  Their usage
         is not limited to ietf-access-control-list and can be
         used anywhere as applicable.

         Copyright (c) 2019 IETF Trust and the persons identified as
         the document authors.  All rights reserved.

         Redistribution and use in source and binary forms, with or
         without modification, is permitted pursuant to, and subject
         to the license terms contained in, the Simplified BSD
         License set forth in Section 4.c of the IETF Trust's Legal
         Provisions Relating to IETF Documents
         (http://trustee.ietf.org/license-info).

         This version of this YANG module is part of RFC 8519; see
         the RFC itself for full legal notices.";

      revision 2019-03-04 {
        description
          "Initial version.";
        reference
          "RFC 8519: YANG Data Model for Network Access Control
                     Lists (ACLs).";
      }

      /*
       * Typedefs
       */
      typedef operator {
        type enumeration {
          enum lte {
            description
              "Less than or equal to.";
          }
          enum gte {
            description
              "Greater than or equal to.";
          }
          enum eq {
            description
              "Equal to.";
          }
          enum neq {
            description
              "Not equal to.";
          }

    Jethanandani, et al.         Standards Track                   [Page 26]

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        }
        description
          "The source and destination port range definitions
           can be further qualified using an operator.  An
           operator is needed only if the lower-port is specified
           and the upper-port is not specified.  The operator
           therefore further qualifies the lower-port only.";
      }

      /*
       * Groupings
       */
      grouping port-range-or-operator {
        choice port-range-or-operator {
          case range {
            leaf lower-port {
              type inet:port-number;
              must '. <= ../upper-port' {
                error-message
                  "The lower-port must be less than or equal to
                   the upper-port.";
              }
              mandatory true;
              description
                "Lower boundary for a port.";
            }
            leaf upper-port {
              type inet:port-number;
              mandatory true;
              description
                "Upper boundary for a port.";
            }
          }
          case operator {
            leaf operator {
              type operator;
              default "eq";
              description
                "Operator to be applied on the port below.";
            }
            leaf port {
              type inet:port-number;
              mandatory true;
              description
                "Port number along with the operator on which to
                 match.";
            }
          }

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          description
            "Choice of specifying a port range or a single
             port along with an operator.";
        }
        description
          "Grouping for port definitions in the form of a
           choice statement.";
      }

      grouping acl-ip-header-fields {
        description
          "IP header fields common to IPv4 and IPv6";
        reference
          "RFC 791: Internet Protocol.";

        leaf dscp {
          type inet:dscp;
          description
            "Differentiated Services Code Point.";
          reference
            "RFC 2474: Definition of the Differentiated Services
                       Field (DS Field) in the IPv4 and IPv6
                       Headers.";
        }

        leaf ecn {
          type uint8 {
            range "0..3";
          }
          description
            "Explicit Congestion Notification.";
          reference
            "RFC 3168: The Addition of Explicit Congestion
                       Notification (ECN) to IP.";
        }

        leaf length {
          type uint16;
          description
            "In the IPv4 header field, this field is known as the Total
             Length.  Total Length is the length of the datagram, measured
             in octets, including internet header and data.

             In the IPv6 header field, this field is known as the Payload
             Length, which is the length of the IPv6 payload, i.e., the rest
             of the packet following the IPv6 header, in octets.";
          reference
            "RFC 791: Internet Protocol

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             RFC 8200: Internet Protocol, Version 6 (IPv6) Specification.";
        }
        leaf ttl {
          type uint8;
          description
            "This field indicates the maximum time the datagram is allowed
             to remain in the internet system.  If this field contains the
             value zero, then the datagram must be dropped.

             In IPv6, this field is known as the Hop Limit.";
          reference
            "RFC 791: Internet Protocol
             RFC 8200: Internet Protocol, Version 6 (IPv6) Specification.";
        }
        leaf protocol {
          type uint8;
          description
            "Internet Protocol number.  Refers to the protocol of the
             payload.  In IPv6, this field is known as 'next-header',
             and if extension headers are present, the protocol is
             present in the 'upper-layer' header.";
          reference
            "RFC 791: Internet Protocol
             RFC 8200: Internet Protocol, Version 6 (IPv6) Specification.";
        }
      }

      grouping acl-ipv4-header-fields {
        description
          "Fields in the IPv4 header.";
        leaf ihl {
          type uint8 {
            range "5..60";
          }
          description
            "In an IPv4 header field, the Internet Header Length (IHL) is
             the length of the internet header in 32-bit words and
             thus points to the beginning of the data.  Note that the
             minimum value for a correct header is 5.";
        }
        leaf flags {
          type bits {
            bit reserved {
              position 0;
              description
                "Reserved.  Must be zero.";
            }
            bit fragment {

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              position 1;
              description
                "Setting the value to 0 indicates may fragment, while
                 setting the value to 1 indicates do not fragment.";
            }
            bit more {
              position 2;
              description
                "Setting the value to 0 indicates this is the last fragment,
                 and setting the value to 1 indicates more fragments are
                 coming.";
            }
          }
          description
            "Bit definitions for the Flags field in the IPv4 header.";
        }
        leaf offset {
          type uint16 {
            range "20..65535";
          }
          description
            "The fragment offset is measured in units of 8 octets (64 bits).
             The first fragment has offset zero.  The length is 13 bits";
        }
        leaf identification {
          type uint16;
          description
            "An identifying value assigned by the sender to aid in
             assembling the fragments of a datagram.";
        }

        choice destination-network {
          case destination-ipv4-network {
            leaf destination-ipv4-network {
              type inet:ipv4-prefix;
              description
                "Destination IPv4 address prefix.";
            }
          }
          description
            "Choice of specifying a destination IPv4 address or
             referring to a group of IPv4 destination addresses.";
        }

        choice source-network {
          case source-ipv4-network {
            leaf source-ipv4-network {
              type inet:ipv4-prefix;

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              description
                "Source IPv4 address prefix.";
            }
          }
          description
            "Choice of specifying a source IPv4 address or
             referring to a group of IPv4 source addresses.";
        }
      }

      grouping acl-ipv6-header-fields {
        description
          "Fields in the IPv6 header.";

        choice destination-network {
          case destination-ipv6-network {
            leaf destination-ipv6-network {
              type inet:ipv6-prefix;
              description
                "Destination IPv6 address prefix.";
            }
          }
          description
            "Choice of specifying a destination IPv6 address
             or referring to a group of IPv6 destination
             addresses.";
        }

        choice source-network {
          case source-ipv6-network {
            leaf source-ipv6-network {
              type inet:ipv6-prefix;
              description
                "Source IPv6 address prefix.";
            }
          }
          description
            "Choice of specifying a source IPv6 address or
             referring to a group of IPv6 source addresses.";
        }

        leaf flow-label {
          type inet:ipv6-flow-label;
          description
            "IPv6 Flow label.";
        }
        reference
          "RFC 4291: IP Version 6 Addressing Architecture

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           RFC 4007: IPv6 Scoped Address Architecture
           RFC 5952: A Recommendation for IPv6 Address Text
                     Representation.";
      }

      grouping acl-eth-header-fields {
        description
          "Fields in the Ethernet header.";
        leaf destination-mac-address {
          type yang:mac-address;
          description
            "Destination IEEE 802 Media Access Control (MAC)
             address.";
        }
        leaf destination-mac-address-mask {
          type yang:mac-address;
          description
            "Destination IEEE 802 MAC address mask.";
        }
        leaf source-mac-address {
          type yang:mac-address;
          description
            "Source IEEE 802 MAC address.";
        }
        leaf source-mac-address-mask {
          type yang:mac-address;
          description
            "Source IEEE 802 MAC address mask.";
        }
        leaf ethertype {
          type eth:ethertype;
          description
            "The Ethernet Type (or Length) value represented
             in the canonical order defined by IEEE 802.
             The canonical representation uses lowercase
             characters.";
          reference
            "IEEE 802-2014, Clause 9.2.";
        }
        reference
          "IEEE 802: IEEE Standard for Local and Metropolitan
           Area Networks: Overview and Architecture.";
      }

      grouping acl-tcp-header-fields {
        description
          "Collection of TCP header fields that can be used to
           set up a match filter.";

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        leaf sequence-number {
          type uint32;
          description
            "Sequence number that appears in the packet.";
        }
        leaf acknowledgement-number {
          type uint32;
          description
            "The acknowledgement number that appears in the
             packet.";
        }
        leaf data-offset {
          type uint8 {
            range "5..15";
          }
          description
            "Specifies the size of the TCP header in 32-bit
             words.  The minimum size header is 5 words and
             the maximum is 15 words; thus, this gives a
             minimum size of 20 bytes and a maximum of 60
             bytes, allowing for up to 40 bytes of options
             in the header.";
        }
        leaf reserved {
          type uint8;
          description
            "Reserved for future use.";
        }
        leaf flags {
          type bits {
            bit cwr {
              position 1;
              description
                "The Congestion Window Reduced (CWR) flag is set
                 by the sending host to indicate that it received
                 a TCP segment with the ECN-Echo (ECE) flag set
                 and had responded in the congestion control
                 mechanism.";
              reference
                "RFC 3168: The Addition of Explicit Congestion
                           Notification (ECN) to IP.";
            }
            bit ece {
              position 2;
              description
                "ECN-Echo has a dual role, depending on the value
                 of the SYN flag.  It indicates the following: if
                 the SYN flag is set (1), the TCP peer is ECN

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                 capable, and if the SYN flag is clear (0), a packet
                 with the Congestion Experienced flag set (ECN=11)
                 in the IP header was received during normal
                 transmission (added to the header by RFC 3168).
                 This serves as an indication of network congestion
                 (or impending congestion) to the TCP sender.";
              reference
                "RFC 3168: The Addition of Explicit Congestion
                           Notification (ECN) to IP.";
            }
            bit urg {
              position 3;
              description
                "Indicates that the Urgent Pointer field is significant.";
            }
            bit ack {
              position 4;
              description
                "Indicates that the Acknowledgement field is significant.
                 All packets after the initial SYN packet sent by the
                 client should have this flag set.";
            }
            bit psh {
              position 5;
              description
                "Push function.  Asks to push the buffered data to the
                 receiving application.";
            }
            bit rst {
              position 6;
              description
                "Reset the connection.";
            }
            bit syn {
              position 7;
              description
                "Synchronize sequence numbers.  Only the first packet
                 sent from each end should have this flag set.  Some
                 other flags and fields change meaning based on this
                 flag, and some are only valid for when it is set,
                 and others when it is clear.";
            }
            bit fin {
              position 8;
              description
                "Last package from the sender.";
            }
          }

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          description
            "Also known as Control Bits.  Contains nine 1-bit flags.";
          reference
            "RFC 793: Transmission Control Protocol.";
        }
        leaf window-size {
          type uint16;
          units "bytes";
          description
            "The size of the receive window, which specifies
             the number of window size units beyond the segment
             identified by the sequence number in the Acknowledgement
             field that the sender of this segment is currently
             willing to receive.";
        }
        leaf urgent-pointer {
          type uint16;
          description
            "This field is an offset from the sequence number
             indicating the last urgent data byte.";
        }
        leaf options {
          type binary {
            length "1..40";
          }
          description
            "The length of this field is determined by the
             Data Offset field.  Options have up to three
             fields: Option-Kind (1 byte), Option-Length
             (1 byte), and Option-Data (variable).  The Option-Kind
             field indicates the type of option and is the
             only field that is not optional.  Depending on
             what kind of option we are dealing with,
             the next two fields may be set: the Option-Length
             field indicates the total length of the option,
             and the Option-Data field contains the value of
             the option, if applicable.";
        }
      }

      grouping acl-udp-header-fields {
        description
          "Collection of UDP header fields that can be used
           to set up a match filter.";
        leaf length {
          type uint16;
          description
            "A field that specifies the length in bytes of

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             the UDP header and UDP data.  The minimum
             length is 8 bytes because that is the length of
             the header.  The field size sets a theoretical
             limit of 65,535 bytes (8-byte header plus 65,527
             bytes of data) for a UDP datagram.  However, the
             actual limit for the data length, which is
             imposed by the underlying IPv4 protocol, is
             65,507 bytes (65,535 minus 8-byte UDP header
             minus 20-byte IP header).

             In IPv6 jumbograms, it is possible to have
             UDP packets of a size greater than 65,535 bytes.
             RFC 2675 specifies that the Length field is set
             to zero if the length of the UDP header plus
             UDP data is greater than 65,535.";
        }
      }

      grouping acl-icmp-header-fields {
        description
          "Collection of ICMP header fields that can be
           used to set up a match filter.";
        leaf type {
          type uint8;
          description
            "Also known as control messages.";
          reference
            "RFC 792: Internet Control Message Protocol
             RFC 4443: Internet Control Message Protocol (ICMPv6)
                       for Internet Protocol Version 6 (IPv6)
                       Specification.";
        }
        leaf code {
          type uint8;
          description
            "ICMP subtype.  Also known as control messages.";
          reference
            "RFC 792: Internet Control Message Protocol
             RFC 4443: Internet Control Message Protocol (ICMPv6)
                       for Internet Protocol Version 6 (IPv6)
                       Specification.";
        }
        leaf rest-of-header {
          type binary;
          description
            "Unbounded in length, the contents vary based on the
             ICMP type and code.  Also referred to as 'Message Body'
             in ICMPv6.";

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          reference
            "RFC 792: Internet Control Message Protocol
             RFC 4443: Internet Control Message Protocol (ICMPv6)
                       for Internet Protocol Version 6 (IPv6)
                       Specification.";
        }
      }
    }

    <CODE ENDS>

    4.3.  ACL Examples

       Requirement: Deny tcp traffic from 192.0.2.0/24, destined to
       198.51.100.0/24.

       Here is the ACL configuration xml for this Access Control List:

       [note: '\' line wrapping for formatting only]

       <?xml version="1.0" encoding="UTF-8"?>
       <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
         <acls
           xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list">
           <acl>
             <name>sample-ipv4-acl</name>
             <type>ipv4-acl-type</type>
             <aces>
               <ace>
                 <name>rule1</name>
                 <matches>
                   <ipv4>
                     <protocol>6</protocol>
                     <destination-ipv4-network>198.51.100.0/24</destination\
       -ipv4-network>
                     <source-ipv4-network>192.0.2.0/24</source-ipv4-network>
                   </ipv4>
                 </matches>
                 <actions>
                   <forwarding>drop</forwarding>
                 </actions>
               </ace>
             </aces>
           </acl>
         </acls>
       </config>

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       The ACL and ACEs can be described in the command-line interface (CLI)
       as the following:

             acl ipv4 sample-ipv4-acl
             deny tcp 192.0.2.0/24 198.51.100.0/24

       Requirement: Accept all DNS traffic destined for 2001:db8::/32 on
       port 53.

       [note: '\' line wrapping for formatting only]

       <?xml version="1.0" encoding="UTF-8"?>
       <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
         <acls
           xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list">
           <acl>
             <name>allow-dns-packets</name>
             <type>ipv6-acl-type</type>
             <aces>
               <ace>
                 <name>rule1</name>
                 <matches>
                   <ipv6>
                     <destination-ipv6-network>2001:db8::/32</destination-i\
       pv6-network>
                   </ipv6>
                   <udp>
                     <destination-port>
                       <operator>eq</operator>
                       <port>53</port>
                     </destination-port>
                   </udp>
                 </matches>
                 <actions>
                   <forwarding>accept</forwarding>
                 </actions>
               </ace>
             </aces>
           </acl>
         </acls>
       </config>

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    4.4.  Port Range Usage and Other Examples

       When a lower-port and an upper-port are both present, it represents a
       range between the lower-port and upper-port with both the lower-port
       and upper-port included.  When only a port is present, it represents
       a port, with the operator specifying the range.

       The following XML example represents a configuration where TCP
       traffic from source ports 16384, 16385, 16386, and 16387 is dropped.

       <?xml version="1.0" encoding="UTF-8"?>
       <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
         <acls
           xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list">
           <acl>
             <name>sample-port-acl</name>
             <type>ipv4-acl-type</type>
             <aces>
               <ace>
                 <name>rule1</name>
                 <matches>
                   <tcp>
                     <source-port>
                       <lower-port>16384</lower-port>
                       <upper-port>16387</upper-port>
                     </source-port>
                   </tcp>
                 </matches>
                 <actions>
                   <forwarding>drop</forwarding>
                 </actions>
               </ace>
             </aces>
           </acl>
         </acls>
       </config>

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       The following XML example represents a configuration where all IPv4
       ICMP echo requests are dropped.

       <?xml version="1.0" encoding="UTF-8"?>
       <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
         <acls
           xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list">
           <acl>
             <name>sample-icmp-acl</name>
             <aces>
               <ace>
                 <name>rule1</name>
                 <matches>
                   <ipv4>
                     <protocol>1</protocol>
                   </ipv4>
                   <icmp>
                     <type>8</type>
                     <code>0</code>
                   </icmp>
                 </matches>
                 <actions>
                   <forwarding>drop</forwarding>
                 </actions>
               </ace>
             </aces>
           </acl>
         </acls>
       </config>

    Jethanandani, et al.         Standards Track                   [Page 40]

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       The following XML example represents a configuration of a single
       port, port 21, that accepts TCP traffic.

       <?xml version="1.0" encoding="UTF-8"?>
       <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
         <acls
           xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list">
           <acl>
             <name>sample-ipv4-acl</name>
             <type>ipv4-acl-type</type>
             <aces>
               <ace>
                 <name>rule1</name>
                 <matches>
                   <tcp>
                     <destination-port>
                       <operator>eq</operator>
                       <port>21</port>
                     </destination-port>
                   </tcp>
                 </matches>
                 <actions>
                   <forwarding>accept</forwarding>
                 </actions>
               </ace>
             </aces>
           </acl>
         </acls>
       </config>

    Jethanandani, et al.         Standards Track                   [Page 41]

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       The following XML example represents a configuration specifying all
       ports that are not equal to 21 that will drop TCP packets destined
       for those ports.

       <?xml version="1.0" encoding="UTF-8"?>
       <config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
         <acls
           xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list">
           <acl>
             <name>sample-ipv4-acl</name>
             <type>ipv4-acl-type</type>
             <aces>
               <ace>
                 <name>rule1</name>
                 <matches>
                   <tcp>
                     <destination-port>
                       <operator>neq</operator>
                       <port>21</port>
                     </destination-port>
                   </tcp>
                 </matches>
                 <actions>
                   <forwarding>drop</forwarding>
                 </actions>
               </ace>
             </aces>
           </acl>
         </acls>
       </config>

    5.  Security Considerations

       The YANG modules specified in this document define a schema for data
       that is designed to be accessed via network management protocol such
       as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
       is the secure transport layer, and the mandatory-to-implement secure
       transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
       is HTTPS, and the mandatory-to-implement secure transport is TLS
       [RFC8446].

       The NETCONF Access Control Model (NACM) [RFC8341] provides the means
       to restrict access for particular NETCONF or RESTCONF users to a
       preconfigured subset of all available NETCONF or RESTCONF protocol
       operations and content.

    Jethanandani, et al.         Standards Track                   [Page 42]

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       There are a number of data nodes defined in these YANG modules that
       are writable/creatable/deletable (i.e., config true, which is the
       default).  These data nodes may be considered sensitive or vulnerable
       in some network environments.  Write operations (e.g., edit-config)
       to these data nodes without proper protection can have a negative
       effect on network operations.  These are the subtrees and data nodes
       and their sensitivity/vulnerability:

          /acls/acl/aces: This list specifies all the configured access
          control entries on the device.  Unauthorized write access to this
          list can allow intruders to modify the entries so as to permit
          traffic that should not be permitted, or deny traffic that should
          be permitted.  The former may result in a DoS attack, or
          compromise the device.  The latter may result in a DoS attack.
          The impact of an unauthorized read access of the list will allow
          the attacker to determine which rules are in effect, to better
          craft an attack.

          /acls/acl/aces/ace/actions/logging: This node specifies ability to
          log packets that match this ace entry.  Unauthorized write access
          to this node can allow intruders to enable logging on one or many
          ace entries, overwhelming the server in the process.  Unauthorized
          read access of this node can allow intruders to access logging
          information, which could be used to craft an attack the server.

    6.  IANA Considerations

       This document registers three URIs and three YANG modules.

    6.1.  URI Registration

       This document registers three URIs in the "IETF XML Registry"
       [RFC3688] as follows:

       URI: urn:ietf:params:xml:ns:yang:ietf-access-control-list
       URI: urn:ietf:params:xml:ns:yang:ietf-packet-fields
       URI: urn:ietf:params:xml:ns:yang:ietf-ethertypes

       Registrant Contact: The IESG.

       XML: N/A; the requested URI is an XML namespace.

    Jethanandani, et al.         Standards Track                   [Page 43]

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    6.2.  YANG Module Name Registration

       This document registers three YANG modules in the "YANG Module Names"
       registry [RFC6020].

       Name: ietf-access-control-list
       Namespace: urn:ietf:params:xml:ns:yang:ietf-access-control-list
       Prefix: acl
       Reference: RFC 8519

       Name: ietf-packet-fields
       Namespace: urn:ietf:params:xml:ns:yang:ietf-packet-fields
       Prefix: packet-fields
       Reference: RFC 8519

       Name: ietf-ethertypes
       Namespace: urn:ietf:params:xml:ns:yang:ietf-ethertypes
       Prefix: ethertypes
       Reference: RFC 8519

    7.  References

    7.1.  Normative References

       [RFC791]   Postel, J., "Internet Protocol", STD 5, RFC 791,
                  DOI 10.17487/RFC0791, September 1981,
                  <https://www.rfc-editor.org/info/rfc791>.

       [RFC792]   Postel, J., "Internet Control Message Protocol", STD 5,
                  RFC 792, DOI 10.17487/RFC0792, September 1981,
                  <https://www.rfc-editor.org/info/rfc792>.

       [RFC793]   Postel, J., "Transmission Control Protocol", STD 7,
                  RFC 793, DOI 10.17487/RFC0793, September 1981,
                  <https://www.rfc-editor.org/info/rfc793>.

       [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
                  Requirement Levels", BCP 14, RFC 2119,
                  DOI 10.17487/RFC2119, March 1997,
                  <https://www.rfc-editor.org/info/rfc2119>.

       [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
                  "Definition of the Differentiated Services Field (DS
                  Field) in the IPv4 and IPv6 Headers", RFC 2474,
                  DOI 10.17487/RFC2474, December 1998,
                  <https://www.rfc-editor.org/info/rfc2474>.

    Jethanandani, et al.         Standards Track                   [Page 44]

    RFC 8519                YANG Data Model for ACLs              March 2019

       [RFC3168]  Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
                  of Explicit Congestion Notification (ECN) to IP",
                  RFC 3168, DOI 10.17487/RFC3168, September 2001,
                  <https://www.rfc-editor.org/info/rfc3168>.

       [RFC4007]  Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and
                  B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
                  DOI 10.17487/RFC4007, March 2005,
                  <https://www.rfc-editor.org/info/rfc4007>.

       [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
                  Architecture", RFC 4291, DOI 10.17487/RFC4291, February
                  2006, <https://www.rfc-editor.org/info/rfc4291>.

       [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
                  Address Text Representation", RFC 5952,
                  DOI 10.17487/RFC5952, August 2010,
                  <https://www.rfc-editor.org/info/rfc5952>.

       [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
                  RFC 6991, DOI 10.17487/RFC6991, July 2013,
                  <https://www.rfc-editor.org/info/rfc6991>.

       [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
                  RFC 7950, DOI 10.17487/RFC7950, August 2016,
                  <https://www.rfc-editor.org/info/rfc7950>.

       [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
                  2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
                  May 2017, <https://www.rfc-editor.org/info/rfc8174>.

       [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
                  (IPv6) Specification", STD 86, RFC 8200,
                  DOI 10.17487/RFC8200, July 2017,
                  <https://www.rfc-editor.org/info/rfc8200>.

       [RFC8343]  Bjorklund, M., "A YANG Data Model for Interface
                  Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
                  <https://www.rfc-editor.org/info/rfc8343>.

    Jethanandani, et al.         Standards Track                   [Page 45]

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    7.2.  Informative References

       [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
                  DOI 10.17487/RFC3688, January 2004,
                  <https://www.rfc-editor.org/info/rfc3688>.

       [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
                  the Network Configuration Protocol (NETCONF)", RFC 6020,
                  DOI 10.17487/RFC6020, October 2010,
                  <https://www.rfc-editor.org/info/rfc6020>.

       [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
                  and A. Bierman, Ed., "Network Configuration Protocol
                  (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
                  <https://www.rfc-editor.org/info/rfc6241>.

       [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
                  Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
                  <https://www.rfc-editor.org/info/rfc6242>.

       [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
                  "Specification of the IP Flow Information Export (IPFIX)
                  Protocol for the Exchange of Flow Information", STD 77,
                  RFC 7011, DOI 10.17487/RFC7011, September 2013,
                  <https://www.rfc-editor.org/info/rfc7011>.

       [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
                  Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
                  <https://www.rfc-editor.org/info/rfc8040>.

       [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
                  BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
                  <https://www.rfc-editor.org/info/rfc8340>.

       [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
                  Access Control Model", STD 91, RFC 8341,
                  DOI 10.17487/RFC8341, March 2018,
                  <https://www.rfc-editor.org/info/rfc8341>.

       [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
                  Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
                  <https://www.rfc-editor.org/info/rfc8446>.

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    Appendix A.  Extending ACL Model Examples

    A.1.  Example of a Company's Proprietary Module

       The "example-newco-acl" module is an example of a company's
       proprietary model that augments the "ietf-acl" module.  It shows how
       to use 'augment' with an XML Path Language (XPath) expression to add
       additional match criteria, actions, and default actions for when no
       ACE matches are found.  All these are company proprietary extensions
       or system feature extensions.  "example-newco-acl" is just an
       example, and it is expected that vendors will create their own
       proprietary models.

       module example-newco-acl {

         yang-version 1.1;

         namespace "http://example.com/ns/example-newco-acl";

         prefix example-newco-acl;

         import ietf-access-control-list {
           prefix acl;
         }

         organization
           "Newco model group.";

         contact
           "abc@newco.com";
         description
           "This YANG module augments the IETF ACL YANG module.";

         revision 2019-03-04 {
           description
             "Creating NewCo proprietary extensions to the ietf-acl
              model.";

           reference
             "RFC 8519: YANG Data Model for Network Access Control
                        Lists (ACLs).";
         }

         augment "/acl:acls/acl:acl/"
               + "acl:aces/acl:ace/"
               + "acl:matches" {
           description
             "Newco proprietary simple filter matches.";

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           choice protocol-payload-choice {
             description
               "Newco proprietary payload match condition.";
             list protocol-payload {
               key "value-keyword";
               ordered-by user;
               description
                 "Match protocol payload.";
               uses match-simple-payload-protocol-value;
             }
           }

           choice metadata {
             description
               "Newco proprietary interface match condition.";
             leaf packet-length {
               type uint16;
               description
                 "Match on packet length.";
             }
           }
         }

         augment "/acl:acls/acl:acl/"
               + "acl:aces/acl:ace/"
               + "acl:actions" {
           description
             "Newco proprietary simple filter actions.";
           choice action {
             description
               "Newco proprietary action choices.";
             case count {
               description
                 "Count the packet in the named counter.";
               leaf count {
                 type uint32;
                 description
                   "Count.";
               }
             }
             case policer {
               description
                 "Name of policer used to rate-limit traffic.";
               leaf policer {
                 type string;
                 description
                   "Name of the policer.";
               }

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             }
             case hierarchical-policer {
               leaf hierarchical-policer {
                 type string;
                 description
                   "Name of the hierarchical policer.";
               }
               description
                 "Name of the hierarchical policer used to
                  rate-limit traffic.";
             }
           }
         }

         augment "/acl:acls/acl:acl"
               + "/acl:aces/acl:ace/"
               + "acl:actions" {
           leaf default-action {
             type identityref {
               base acl:forwarding-action;
             }
             default "acl:drop";
             description
               "Actions that occur if no ACE is matched.";
           }
           description
             "Newco proprietary default action.";
         }

         grouping match-simple-payload-protocol-value {
           description
             "Newco proprietary payload";
           leaf value-keyword {
             type enumeration {
               enum icmp {
                 description
                   "Internet Control Message Protocol.";
               }
               enum icmp6 {
                 description
                   "Internet Control Message Protocol
                    Version 6.";
               }
               enum range {
                 description
                   "Range of values.";
               }
             }

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             description
               "(null).";
           }
         }
       }

       The following figure is the tree diagram of example-newco-acl.  In
       this example, /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace/
       ietf-acl:matches are augmented with two new choices: protocol-
       payload-choice and metadata.  The protocol-payload-choice uses a
       grouping with an enumeration of all supported protocol values.
       Metadata matches apply to fields associated with the packet, that are
       not in the packet header, such as overall packet length.  In another
       example, /ietf-acl:acls/ietf-acl:acl/ietf-acl:aces/ietf-acl:ace/
       ietf-acl:actions are augmented with a new choice of actions.

       module: example-newco-acl
         augment /acl:acls/acl:acl/acl:aces/acl:ace/acl:matches:
           +--rw (protocol-payload-choice)?
           |  +--:(protocol-payload)
           |     +--rw protocol-payload* [value-keyword]
           |        +--rw value-keyword    enumeration
           +--rw (metadata)?
              +--:(packet-length)
                 +--rw packet-length?      uint16
         augment /acl:acls/acl:acl/acl:aces/acl:ace/acl:actions:
           +--rw (action)?
              +--:(count)
              |  +--rw count?                   uint32
              +--:(policer)
              |  +--rw policer?                 string
              +--:(hierarchical-policer)
                 +--rw hierarchical-policer?   string
         augment /acl:acls/acl:acl/acl:aces/acl:ace/acl:actions:
           +--rw default-action?   identityref

    A.2.  Linux nftables

       As the Linux platform is becoming more popular than the networking
       platform, the Linux data model is changing.  Previously, ACLs in
       Linux were highly protocol specific, and different utilities were
       used (iptables, ip6tables, arptables, and ebtables), so each one had
       a separate data model.  Recently, this has changed, and a single
       utility, nftables, has been developed.  With a single application, it
       has a single data model for firewall filters, and it follows very
       similarly the ietf-access-control list module proposed in this
       document.  The nftables support input and output ACEs, and each ACE
       can be defined with match and action.

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       The example in Section 4.3 can be configured using nftable tool as
       below.

             nft add table ip filter
             nft add chain filter input
             nft add rule ip filter input ip protocol tcp ip saddr \
                 192.0.2.1/24 drop

       The configuration entries added in nftable would be:

             table ip filter {
               chain input {
                 ip protocol tcp ip saddr 192.0.2.1/24 drop
               }
             }

       We can see that there are many similarities between Linux nftables
       and IETF ACL YANG data models and their extension models.  It should
       be fairly easy to do translation between the ACL YANG model described
       in this document and Linux nftables.

    A.3.  Ethertypes

       The ACL module is dependent on the definition of Ethertypes.  IEEE
       owns the allocation of those Ethertypes.  This model is being
       included here to enable the definition of those types till such time
       that IEEE takes up the task of publication of the model that defines
       those Ethertypes.  At that time, this model can be deprecated.

       <CODE BEGINS> file "ietf-ethertypes@2019-03-04.yang"

       module ietf-ethertypes {
         namespace "urn:ietf:params:xml:ns:yang:ietf-ethertypes";
         prefix ethertypes;

         organization
           "IETF NETMOD (Network Modeling) Working Group.";

         contact
           "WG Web:   <https://datatracker.ietf.org/wg/netmod/>
            WG List:  <mailto:netmod@ietf.org>

            Editor:   Mahesh Jethanandani
                      <mjethanandani@gmail.com>";

         description
           "This module contains common definitions for the

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            Ethertype used by different modules.  It is a
            placeholder module, till such time that IEEE
            starts a project to define these Ethertypes
            and publishes a standard.

            At that time, this module can be deprecated.

            Copyright (c) 2019 IETF Trust and the persons identified as
            the document authors.  All rights reserved.

            Redistribution and use in source and binary forms, with or
            without modification, is permitted pursuant to, and subject
            to the license terms contained in, the Simplified BSD
            License set forth in Section 4.c of the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (http://trustee.ietf.org/license-info).

            This version of this YANG module is part of RFC 8519; see
            the RFC itself for full legal notices.";

         revision 2019-03-04 {
           description
             "Initial revision.";
           reference
             "RFC 8519: YANG Data Model for Network Access Control
                        Lists (ACLs).";
         }

         typedef ethertype {
           type union {
             type uint16;
             type enumeration {
               enum ipv4 {
                 value 2048;
                 description
                   "Internet Protocol version 4 (IPv4) with a
                    hex value of 0x0800.";
                 reference
                   "RFC 791: Internet Protocol.";
               }
               enum arp {
                 value 2054;
                 description
                   "Address Resolution Protocol (ARP) with a
                    hex value of 0x0806.";
                 reference
                   "RFC 826: An Ethernet Address Resolution Protocol: Or
                             Converting Network Protocol Addresses to 48.bit

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                             Ethernet Address for Transmission on Ethernet
                             Hardware.";
               }
               enum wlan {
                 value 2114;
                 description
                   "Wake-on-LAN.  Hex value of 0x0842.";
               }
               enum trill {
                 value 8947;
                 description
                   "Transparent Interconnection of Lots of Links.
                    Hex value of 0x22F3.";
                 reference
                   "RFC 6325: Routing Bridges (RBridges): Base Protocol
                              Specification.";
               }
               enum srp {
                 value 8938;
                 description
                   "Stream Reservation Protocol.  Hex value of
                    0x22EA.";
                 reference
                   "IEEE 801.1Q-2011.";
               }
               enum decnet {
                 value 24579;
                 description
                   "DECnet Phase IV.  Hex value of 0x6003.";
               }
               enum rarp {
                 value 32821;
                 description
                   "Reverse Address Resolution Protocol.
                    Hex value 0x8035.";
                 reference
                   "RFC 903: A Reverse Address Resolution Protocol.";
               }
               enum appletalk {
                 value 32923;
                 description
                   "Appletalk (Ethertalk).  Hex value of 0x809B.";
               }
               enum aarp {
                 value 33011;
                 description
                   "Appletalk Address Resolution Protocol.  Hex value
                    of 0x80F3.";

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               }
               enum vlan {
                 value 33024;
                 description
                   "VLAN-tagged frame (IEEE 802.1Q) and Shortest Path
                    Bridging IEEE 802.1aq with Network-Network
                    Interface (NNI) compatibility.  Hex value of
                    0x8100.";
                 reference
                   "IEEE 802.1Q.";
               }
               enum ipx {
                 value 33079;
                 description
                   "Internetwork Packet Exchange (IPX).  Hex value
                    of 0x8137.";
               }
               enum qnx {
                 value 33284;
                 description
                   "QNX Qnet.  Hex value of 0x8204.";
               }
               enum ipv6 {
                 value 34525;
                 description
                   "Internet Protocol Version 6 (IPv6).  Hex value
                    of 0x86DD.";
                 reference
                   "RFC 8200: Internet Protocol, Version 6 (IPv6)
                              Specification
                    RFC 8201: Path MTU Discovery for IP version 6.";
               }
               enum efc {
                 value 34824;
                 description
                   "Ethernet flow control using pause frames.
                    Hex value of 0x8808.";
                 reference
                   "IEEE 802.1Qbb.";
               }
               enum esp {
                 value 34825;
                 description
                   "Ethernet Slow Protocol.  Hex value of 0x8809.";
                 reference
                   "IEEE 802.3-2015.";
               }
               enum cobranet {

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                 value 34841;
                 description
                   "CobraNet.  Hex value of 0x8819.";
               }
               enum mpls-unicast {
                 value 34887;
                 description
                   "Multiprotocol Label Switching (MPLS) unicast traffic.
                    Hex value of 0x8847.";
                 reference
                   "RFC 3031: Multiprotocol Label Switching Architecture.";
               }
               enum mpls-multicast {
                 value 34888;
                 description
                   "MPLS multicast traffic.  Hex value of 0x8848.";
                 reference
                   "RFC 3031: Multiprotocol Label Switching Architecture.";
               }
               enum pppoe-discovery {
                 value 34915;
                 description
                   "Point-to-Point Protocol over Ethernet.  Used during
                    the discovery process.  Hex value of 0x8863.";
                 reference
                   "RFC 2516: A Method for Transmitting PPP Over Ethernet
                              (PPPoE).";
               }
               enum pppoe-session {
                 value 34916;
                 description
                   "Point-to-Point Protocol over Ethernet.  Used during
                    session stage.  Hex value of 0x8864.";
                 reference
                   "RFC 2516: A Method for Transmitting PPP Over Ethernet
                              (PPPoE).";
               }
               enum intel-ans {
                 value 34925;
                 description
                   "Intel Advanced Networking Services.  Hex value of
                    0x886D.";
               }
               enum jumbo-frames {
                 value 34928;
                 description
                   "Jumbo frames or Ethernet frames with more than
                    1500 bytes of payload, up to 9000 bytes.";

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               }
               enum homeplug {
                 value 34939;
                 description
                   "Family name for the various power line
                    communications.  Hex value of 0x887B.";
               }
               enum eap {
                 value 34958;
                 description
                   "Ethernet Access Protocol (EAP) over LAN.  Hex value
                    of 0x888E.";
                 reference
                   "IEEE 802.1X.";
               }
               enum profinet {
                 value 34962;
                 description
                   "PROcess FIeld Net (PROFINET).  Hex value of 0x8892.";
               }
               enum hyperscsi {
                 value 34970;
                 description
                   "Small Computer System Interface (SCSI) over Ethernet.
                    Hex value of 0x889A.";
               }
               enum aoe {
                 value 34978;
                 description
                   "Advanced Technology Advancement (ATA) over Ethernet.
                    Hex value of 0x88A2.";
               }
               enum ethercat {
                 value 34980;
                 description
                   "Ethernet for Control Automation Technology (EtherCAT).
                    Hex value of 0x88A4.";
               }
               enum provider-bridging {
                 value 34984;
                 description
                   "Provider Bridging (802.1ad) and Shortest Path Bridging
                    (801.1aq).  Hex value of 0x88A8.";
                 reference
                   "IEEE 802.1ad and IEEE 802.1aq).";
               }
               enum ethernet-powerlink {
                 value 34987;

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                 description
                   "Ethernet Powerlink.  Hex value of 0x88AB.";
               }
               enum goose {
                 value 35000;
                 description
                   "Generic Object Oriented Substation Event (GOOSE).
                    Hex value of 0x88B8.";
                 reference
                   "IEC/ISO 8802-2 and 8802-3.";
               }
               enum gse {
                 value 35001;
                 description
                   "Generic Substation Events.  Hex value of 88B9.";
                 reference
                   "IEC 61850.";
               }
               enum sv {
                 value 35002;
                 description
                   "Sampled Value Transmission.  Hex value of 0x88BA.";
                 reference
                   "IEC 61850.";
               }
               enum lldp {
                 value 35020;
                 description
                   "Link Layer Discovery Protocol (LLDP).  Hex value of
                    0x88CC.";
                 reference
                   "IEEE 802.1AB.";
               }
               enum sercos {
                 value 35021;
                 description
                   "Sercos Interface.  Hex value of 0x88CD.";
               }
               enum wsmp {
                 value 35036;
                 description
                   "WAVE Short Message Protocol (WSMP).  Hex value of
                    0x88DC.";
               }
               enum homeplug-av-mme {
                 value 35041;
                 description
                   "HomePlug AV Mobile Management Entity (MME).  Hex value

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                    of 88E1.";
               }
               enum mrp {
                 value 35043;
                 description
                   "Media Redundancy Protocol (MRP).  Hex value of
                    0x88E3.";
                 reference
                   "IEC 62439-2.";
               }
               enum macsec {
                 value 35045;
                 description
                   "MAC Security.  Hex value of 0x88E5.";
                 reference
                   "IEEE 802.1AE.";
               }
               enum pbb {
                 value 35047;
                 description
                   "Provider Backbone Bridges (PBB).  Hex value of
                    0x88E7.";
                 reference
                   "IEEE 802.1ah.";
               }
               enum cfm {
                 value 35074;
                 description
                   "Connectivity Fault Management (CFM).  Hex value of
                    0x8902.";
                 reference
                   "IEEE 802.1ag.";
               }
               enum fcoe {
                 value 35078;
                 description
                   "Fiber Channel over Ethernet (FCoE).  Hex value of
                    0x8906.";
                 reference
                   "T11 FC-BB-5.";
               }
               enum fcoe-ip {
                 value 35092;
                 description
                   "FCoE Initialization Protocol.  Hex value of 0x8914.";
               }
               enum roce {
                 value 35093;

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                 description
                   "RDMA over Converged Ethernet (RoCE).  Hex value of
                    0x8915.";
               }
               enum tte {
                 value 35101;
                 description
                   "TTEthernet Protocol Control Frame (TTE).  Hex value
                    of 0x891D.";
                 reference
                   "SAE AS6802.";
               }
               enum hsr {
                 value 35119;
                 description
                   "High-availability Seamless Redundancy (HSR).  Hex
                    value of 0x892F.";
                 reference
                   "IEC 62439-3:2016.";
               }
             }
           }
           description
             "The uint16 type placeholder is defined to enable
              users to manage their own ethertypes not
              covered by the module.  Otherwise, the module contains
              enum definitions for the more commonly used ethertypes.";
         }
       }

       <CODE ENDS>

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    Acknowledgements

       Alex Clemm, Andy Bierman, and Lisa Huang started by sketching an
       initial draft version in several past IETF meetings.  That document
       included an ACL YANG model structure and a rich set of match filters,
       and it acknowledged contributions by Louis Fourie, Dana Blair, Tula
       Kraiser, Patrick Gili, George Serpa, Martin Bjorklund, Kent Watsen,
       and Phil Shafer.  Many people have reviewed the various earlier draft
       versions that made the document that went into IETF charter.

       Dean Bogdanovic, Kiran Agrahara Sreenivasa, Lisa Huang, and Dana
       Blair each evaluated the YANG model in earlier draft versions
       separately, and then they worked together to create an ACL draft
       version that was supported by different vendors.  That document
       removed vendor-specific features and gave examples that allowed
       vendors to extend their own proprietary ACLs.  That earlier draft
       version was superseded with this document and received participation
       from many vendors.

       The authors would like to thank Jason Sterne, Lada Lhotka, Juergen
       Schoenwalder, David Bannister, Jeff Haas, Kristian Larsson, and Einar
       Nilsen-Nygaard for their reviews of and suggestions for the document.

    Authors' Addresses

       Mahesh Jethanandani
       VMware

       Email: mjethanandani@gmail.com

       Sonal Agarwal
       Cisco Systems, Inc.

       Email: sagarwal12@gmail.com

       Lisa Huang

       Email: huangyi_99@yahoo.com

       Dana Blair

       Email: dana@blairhome.com

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