NETMOD WG                                                  D. Bogdanovic
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                           K. Sreenivasa
Expires: August 9, September 6, 2015                 Brocade Communications System
                                                                L. Huang
                                                                D. Blair
                                                           Cisco Systems
                                                       February 05,
                                                           March 5, 2015

           Network Access Control List (ACL) YANG Data Model
                     draft-ietf-netmod-acl-model-01
                     draft-ietf-netmod-acl-model-02

Abstract

   This document describes a data model of Access Control List (ACL)
   basic building blocks.

Status of This Memo

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

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

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

   This Internet-Draft will expire on August 9, September 6, 2015.

Copyright Notice

   Copyright (c) 2015 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Definitions and Acronyms  . . . . . . . . . . . . . . . .   3
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Design of the ACL Model . . . . . . . . . . . . . . . . . . .   3
     3.1.  ACL Modules . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  ACL YANG Models . . . . . . . . . . . . . . . . . . . . . . .   6   5
     4.1.  IETF-ACL module . . . . . . . . . . . . . . . . . . . . .   6   5
     4.2.  Packet Header  IETF-PACKET-FIELDS module . . . . . . . . . . . . . . . . . .  11
     4.3.  A company proprietary module example  . . . . . . . . . .  15
     4.4.  An ACL Example  . . . . . . . . . . . . . . . . . . . . .  17
     4.5.  16
     4.4.  Port Range Usage Example  . . . . . . . . . . . . . . . .  18  17
   5.  Example of extending existing model for route filtering . . .  19
   6.  Linux nftables  . . . . . . . . . . . . . . . . . . . . . . .  21
   7.  17
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   8.  18
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22
   9.  18
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  22
   10. Change log [RFC Editor: Please remove]  19
   9.  References  . . . . . . . . . . .  23
   11. References . . . . . . . . . . . . . .  19
     9.1.  Normative References  . . . . . . . . . . .  23
     11.1.  Normative . . . . . . .  19
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Appendix A.  Extending ACL model examples . . . .  23
     11.2.  Informative References . . . . . . . .  20
     A.1.  Example of extending existing model for route filtering .  20
     A.2.  A company proprietary module example  . . . . . . . . . .  22
     A.3.  Attaching Access Control List to interfaces . . . . . . .  23  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23  26

1.  Introduction

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

   An ACL is an 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 action
   criteria.

   The match criteria consist of a tuple of packet header match criteria
   and metadata match criteria.

   o  Packet header matches apply to fields visible in the packet such
      as address or class of service or port numbers.

   o  Metadata matches apply to fields associated with the packet but
      not in the packet header such as input interface or overall packet
      length

   The actions specify what to do with the packet when the matching
   criteria is 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 endless depending on the innovations of
   the networked devices.

1.1.  Definitions and Acronyms

   ACE: Access Control Entry

   ACL: Access Control List

   AFI: Address Field Identifier

   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

   TCP: Transmission Control Protocol

2.  Problem Statement

   This document defines a YANG [RFC6020] data model for the
   configuration of ACLs.  It is very important that model can be easily
   reused between vendors and between applications.

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

3.  Design of the ACL Model

   Although different vendors have different ACL data models, there is a
   common understanding of what access control list (ACL) is.  A network
   system usually have a list of ACLs, and each ACL contains an ordered
   list of rules, also known as access list entries - ACEs.  Each ACE
   has a group of match criteria and a group of action criteria.  The
   match criteria consist of packet header matching and metadata
   matching.  Packet header matching applies to fields visible in the
   packet such as address or class of service or port numbers.  Metadata
   matching applies to fields associated with the packet, but not in the
   packet header such as 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.  The model also includes overall operational state
   for the ACL and operational state for each ACE, targets where the ACL
   applied.  One ACL can be applied to multiple targets within the
   device, such as interfaces of a networked device, applications or
   features running in the device, etc.  When applied to interfaces of a
   networked device, the ACL is applied in a direction which indicates
   if it should be applied to packet entering (input) or leaving the
   device (output).

   This draft tries to address the commonalities between all vendors and
   create a common model, which can be augmented with proprietary
   models.  The base model is very simple and with this design we hope
   to achieve needed flexibility for each vendor to extend the base
   model.

3.1.  ACL Modules

   There are three two YANG modules in the model.  The first module, "ietf-
   acl", defines generic ACL aspects which 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, "packet-headers". "ietf-packet-fields".  The match container in "ietf-acl" "ietf-
   acl" uses groupings in "packet-headers". "ietf-packet-fields".  The "packet-headers" "ietf-packet-
   fields" modules can easily be extended to reuse definitions from
   other modules such as IPFIX [RFC5101] or migrate proprietary
   augmented module definitions into the standard module.

module: ietf-acl
+--rw access-lists
+--rw access-list* [acl-name] [access-control-list-name]
+--rw acl-name access-control-list-name         string
+--rw acl-type?              acl-type access-control-list-type?        access-control-list-type
+--ro acl-oper-data access-control-list-oper-data
|  +--ro match-counter?   ietf:counter64 (targets)?
|     +--:(interface-name)
|        +--ro targets* interface-name*   string
+--rw access-list-entries
+--rw access-list-entry* [rule-name]
+--rw rule-name                        string
+--rw matches
|  +--rw (ace-type)? (access-list-entries-type)?
|  |  +--:(ace-ip)  +--:(access-list-entries-ip)
|  |  |  +--rw source-port-range
|  |  |  |  +--rw lower-port    inet:port-number
|  |  |  |  +--rw upper-port?   inet:port-number
|  |  |  +--rw destination-port-range
|  |  |  |  +--rw lower-port    inet:port-number
|  |  |  |  +--rw upper-port?   inet:port-number
|  |  |  +--rw dscp?                           inet:dscp
|  |  |  +--rw protocol?                       uint8
|  |  |  +--rw (ace-ip-version)? (access-list-entries-ip-version)?
|  |  |     +--:(ace-ipv4)     +--:(access-list-entries-ipv4)
|  |  |     |  +--rw destination-ipv4-address? destination-ipv4-network?       inet:ipv4-prefix
|  |  |     |  +--rw source-ipv4-address? source-ipv4-network?            inet:ipv4-prefix
|  |  |     +--:(ace-ipv6)     +--:(access-list-entries-ipv6)
|  |  |        +--rw destination-ipv6-address? destination-ipv6-network?       inet:ipv6-prefix
|  |  |        +--rw source-ipv6-address? source-ipv6-network?            inet:ipv6-prefix
|  |  |        +--rw flow-label?                     inet:ipv6-flow-label
|  |  +--:(ace-eth)  +--:(access-list-entries-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 input-interface?                string
|  +--rw absolute
|     +--rw start?    yang:date-and-time
|     +--rw end?      yang:date-and-time
|     +--rw active?   boolean
+--rw actions
|  +--rw (packet-handling)?
|     +--:(deny)
|     |  +--rw deny?     empty
|     +--:(permit)
|        +--rw permit?   empty
+--ro ace-oper-data access-list-entries-oper-data
             +--ro match-counter?   ietf:counter64

   Module "newco-acl" is an example of company proprietary model, that
   augments "ietf-acl" module.  It shows how to add additional match
   criteria, action criteria, and default actions when no ACE matches
   found.  All these are company proprietary extensions or system
   feature extensions. "newco-acl" is just an example and it is expected
   from vendors to create their own propietary models.

module: newco-acl
augment /ietf-acl:access-list/ietf-acl:access-list-entries/ietf-acl:matches:
   +--rw (protocol_payload_choice)?
      +--:(protocol_payload)
         +--rw protocol_payload* [value_keyword]
            +--rw value_keyword    enumeration
augment /ietf-acl:access-list/ietf-acl:access-list-entries/ietf-acl:actions:
   +--rw (action)?
      +--:(count)
      |  +--rw count?                   string
      +--:(policer)
      |  +--rw policer?                 string
      +--:(hiearchical-policer)
         +--rw hierarchitacl-policer?   string
augment /ietf-acl:access-lists/ietf-acl:access-list:
   +--rw default-actions
      +--rw deny?   empty   yang:counter64

4.  ACL YANG Models

4.1.  IETF-ACL module

   "ietf-acl" is the standard top level module for Access lists.  It has
   a container for "access-list" to store access list information.  This
   container has information identifying the access list by a name("acl-
   name") and a list("access-list-entries") of rules associated with the
   "acl-name".  Each of the entries in the list("access-list-entries")
   indexed by the string "rule-name" have containers defining "matches"
   and "actions".  The "matches" define criteria used to identify
   patterns in "packet-fields". "ietf-packet-fields".  The "actions" define behavior to
   undertake once a "match" has been identified.

<CODE BEGINS>file "ietf-acl@2015-03-04.yang"
module ietf-acl {
  yang-version 1;

  namespace "urn:ietf:params:xml:ns:yang:ietf-acl";

  prefix acl; access-control-list;

  import ietf-yang-types {
    prefix "ietf"; "yang";

  }

  import packet-fields ietf-packet-fields {
    prefix "packet-fields";
  }

  organization
    "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

  contact
    "WG Web: http://tools.ietf.org/wg/netmod/
    WG List: netmod@ietf.org

    WG Chair: Juergen Schoenwaelder
    j.schoenwaelder@jacobs-university.de

    WG Chair: Tom Nadeau
    tnadeau@lucidvision.com

    Editor: Dean Bogdanovic
    deanb@juniper.net

    Editor: Kiran Agrahara Sreenivasa
    kkoushik@brocade.com

    Editor: Lisa Huang
    yihuan@cisco.com

    Editor: Dana Blair
    dblair@cisco.com";

  description
    "This YANG module defines a component that describing the
    configuration of Access Control Lists (ACLs).";

     revision 2014-10-10 {
       description "Creating base model for netmod.";
       reference
         "RFC 6020: YANG - A Data Modeling Language for (ACLs).

    Copyright (c) 2015 IETF Trust and the
         Network Configuration Protocol (NETCONF)";
     }

     identity acl-base {
       description "Base acl type for all ACL type identifiers.";
     }

     identity ip-acl {
       base "acl:acl-base";
       description "layer 3 ACL type";
     }
    identity eth-acl {
       base "acl:acl-base";
       description "layer 2 ACL type";
     }

     typedef acl-type 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 XXXX; see
    the RFC itself for full legal notices.";

    // RFC Ed.: replace XXXX with actual RFC number and remove this
    // note.

  revision 2015-03-04 {
    description "Base model for Network Access Control List (ACL).";
    reference
      "RFC XXXX: Network Access Control List (ACL)
      YANG Data  Model";
  }

  identity access-control-list-base {
    description "Base access control list type for all access control list type
      identifiers.";
  }

  identity IP-access-control-list {
    base "access-control-list:access-control-list-base";
    description "IP-access control list is common name for layer 3 and 4 access
    control list types. It is common among vendors to call 3-tupple or 5 tupple
    IP access control lists";
  }

  identity eth-access-control-list {
    base "access-control-list:access-control-list-base";
    description "Ethernet access control list is name for layer 2 Ethernet
    technology access control list types, like 10/100/1000baseT or WiFi
    access control list";
  }

  typedef access-control-list-type {
    type identityref {
      base "acl-base"; "access-control-list-base";
    }
    description
      "This type is used to refer to an Access Control List
      (ACL) type";
  }

  typedef acl-ref access-control-list-ref {
    type leafref {
      path "/acl:access-lists/acl:access-list/acl:acl-name"; "/access-lists/access-list/access-control-list-name";
    }
    description "This type is used by data models that need to referenced an acl";
      access control list";

  }

  container access-lists {
    description
         "Access control lists.";
      "This is top level container for Access Control Lists. It can have one
        or more Access Control List.";

    list access-list {
      key acl-name; access-control-list-name;
      description "
           An "An access list (acl) is an ordered list of
        access list entries (ace). (ACE). Each ace access control entries has a
           sequence number to define the order,
        list of match criteria, and a list of actions.
        Since there are several kinds of acls
           implementeded access control lists
        implemented with different attributes for
        each and different for each vendor, this
        model accomodates accommodates customizing acls access control lists for
        each kind and for each vendor.
           "; vendor.";

      leaf acl-name access-control-list-name {
        type string;
        description "The name of access-list. A device MAY restrict the length
        and value of this name, possibly space and special characters are not
        allowed.";
      }

      leaf acl-type access-control-list-type {
        type acl-type; access-control-list-type;
        description "Type of ACL"; access control list. When this
        type is not explicitely specified, if vendor implementation permits,
        the access control entires in the list can be mixed,
        by containing L2, L3 and L4 entries";
      }
      container acl-oper-data access-control-list-oper-data {
        config false;
        description "Overall ACL access control list operational data";
           leaf match-counter {
             type ietf:counter64;

        choice targets{
          description "Total match count for ACL";
           }

           leaf-list "List of targets where access control list is applied";
          leaf-list interface-name {
            type string;
            description "List of targets "Interfaces where ACL access control list is applied";
          }
        }
      }

      container access-list-entries {
        description "The access-list-entries container contains
          a list of access-list-entry(ACE).";

        list access-list-entry {
          key rule-name;
          ordered-by user;
          description "List of access list entries(ACE)";
          leaf rule-name {
              type string;
              description "Entry name.";
          }

          container matches {
            description "Define match criteria";
            choice ace-type access-list-entries-type {
              description "Type of ace."; access list entry.";
              case ace-ip access-list-entries-ip {
                uses packet-fields:acl-ip-header-fields; packet-fields:access-control-list-ip-header-fields;
                choice ace-ip-version access-list-entries-ip-version {
                  description "Choice of IP version.";
                  case ace-ipv4 access-list-entries-ipv4 {
                    uses packet-fields:acl-ipv4-header-fields; packet-fields:access-control-list-ipv4-header-fields;
                  }
                  case ace-ipv6 access-list-entries-ipv6 {

                   uses packet-fields:acl-ipv6-header-fields; packet-fields:access-control-list-ipv6-header-fields;
                  }
                }
              }
              case ace-eth access-list-entries-eth {
                description "Ethernet MAC address entry.";
                uses packet-fields:acl-eth-header-fields; packet-fields:access-control-list-eth-header-fields;
              }
            }
            uses packet-fields:metadata;
          }

          container actions {
            description "Define action criteria";
            choice packet-handling {
              default deny;

              description "Packet handling action.";
              case deny {
                leaf deny {
                  type empty;
                  description "Deny action.";

                }
              }
              case permit {
                leaf permit {
                  type empty;
                  description "Permit action.";
                }
              }
            }
          }

          container ace-oper-data access-list-entries-oper-data {
            config false;

            description "Per ace access list entries operational data";
            leaf match-counter {
              type ietf:counter64; yang:counter64;
              description "Number of matches for an ace"; access list entry";
            }
          }
        }
      }
    }
  }
}

<CODE ENDS>
4.2.  Packet Header  IETF-PACKET-FIELDS module

   The packet fields module defines the necessary groups for matching on
   fields in the packet including ethernet, ipv4, ipv6, transport layer
   fields and metadata.  These groupings can be augmented to include
   other proprietary matching criteria.  Since the number of match
   criteria is very large, the base draft does not include these
   directly but references them by "uses" to keep the base module
   simple.

<CODE BEGINS>file "ietf-packet-fields@2015-03-04.yang"

module packet-fields ietf-packet-fields {
  yang-version 1;

  namespace "urn:ietf:params:xml:ns:yang:packet-fields"; "urn:ietf:params:xml:ns:yang:ietf-packet-fields";

  prefix packet-fields;

  import ietf-inet-types {
    prefix "inet";

  }

  import ietf-yang-types {
    prefix "yang";
  }

  organization
  "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

  contact
    "WG Web: http://tools.ietf.org/wg/netmod/
    WG List: netmod@ietf.org

    WG Chair: Juergen Schoenwaelder
    j.schoenwaelder@jacobs-university.de

    WG Chair: Tom Nadeau
    tnadeau@lucidvision.com

    Editor: Dean Bogdanovic
    deanb@juniper.net

    Editor: Kiran Agrahara Sreenivasa
    kkoushik@brocade.com

    Editor: Lisa Huang
    yihuan@cisco.com

    Editor: Dana Blair

    dblair@cisco.com";

  description
    "This YANG module defines groupings that used by ietf-acl
    but not limited to acl.";

     revision 2014-11-06 {
       description "Initial version of packet fields used by acl.

    Copyright (c) 2015 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 XXXX; see
    the RFC itself for full legal notices.";

    // RFC Ed.: replace XXXX with actual RFC number and remove this
    // note.

  revision 2015-03-04 {
    description "Initial version of packet fields used by
      access-lists";
    reference
      "RFC 6020: XXXX: Network Access Control List (ACL)
      YANG - A Data Modeling Language for the
         Network Configuration Protocol (NETCONF)";  Model";
  }

  grouping acl-transport-header-fields access-control-list-transport-header-fields {
    description "Transport header fields";

    container source-port-range {
      description "inclusive range of source ports";
      leaf lower-port {
        type inet:port-number;
        mandatory true;
        description "Lower boundary.";
      }
      leaf upper-port {
        type inet:port-number;
        description "Upper boundary."; boundary. If exist, upper port must be greater or
        equal to lower port.";

      }
    }

    container destination-port-range {
      description "inclusive range of destination ports";
      leaf lower-port {
        type inet:port-number;
        mandatory true;
        description "Lower boundary.";
      }
      leaf upper-port {
        type inet:port-number;
        description "Upper boundary.";
      }
    }
  }

  grouping acl-ip-header-fields access-control-list-ip-header-fields {
    description "Header fields common to ipv4 and ipv6";

    uses acl-transport-header-fields; access-control-list-transport-header-fields;

    leaf dscp {
      type inet:dscp;

      description "Value of dscp.";
    }

    leaf protocol {
      type uint8;
      description "Internet Protocol number.";
    }

  }

  grouping acl-ipv4-header-fields access-control-list-ipv4-header-fields {
    description "fields in IPv4 header";

    leaf destination-ipv4-network {
      type inet:ipv4-prefix;
      description "One or more ip addresses.";
    }

    leaf source-ipv4-network {
      type inet:ipv4-prefix;
      description "One or more ip addresses.";
    }

  }

  grouping acl-ipv6-header-fields access-control-list-ipv6-header-fields {
    description "fields in IPv6 header";

    leaf destination-ipv6-network {
      type inet:ipv6-prefix;
      description "One or more ip addresses.";
    }

    leaf source-ipv6-network {
      type inet:ipv6-prefix;
      description "One or more ip addresses.";
    }

    leaf flow-label {
      type inet:ipv6-flow-label;
      description "Flow label.";
    }

  }

  grouping acl-eth-header-fields access-control-list-eth-header-fields {

    description "fields in ethernet header";

    leaf destination-mac-address {
      type yang:mac-address;
      description "Mac addresses.";
    }

    leaf destination-mac-address-mask {
      type yang:mac-address;
      description "Mac addresses mask.";
    }

    leaf source-mac-address {
      type yang:mac-address;
      description "Mac addresses.";
    }

    leaf source-mac-address-mask {
      type yang:mac-address;
      description "Mac addresses mask.";
    }
  }

  grouping timerange {
    description "Define time "Time range entries contains time
    segments to restrict allow access-control-list to be
    active/inactive when the access. The system time range
    is identified by a name
             and then referenced by a function, so that those
             time restrictions are imposed on within the function itself."; time segments.";

    container absolute {
      description
        "Absolute time and date that
        the associated function starts
        going into effect.";

      leaf start {
        type yang:date-and-time;
        description
        "Start time and date";
      }
      leaf end {
        type yang:date-and-time;
        description "Absolute end time and date";
      }
      leaf active {
        type boolean;
        default "true";
        description

          "Specify the associated function

          active or inactive state when
          starts going into effect";
      }
    } // container absolute
  } //grouping timerange

  grouping metadata {
    description "Fields associated with a packet but not in
      the header";

    leaf input-interface {
      type string;
      description "Packet was received on this interface";
    }
    uses timerange;
  }
}

<CODE ENDS>
4.3.  A company proprietary module example  An ACL Example

   Requirement: Deny All traffic from 10.10.10.1 bound for host
   10.10.10.255 from leaving.

   In order to achieve the figure below is requirement, an example how proprietary models name access control list is
   needed.  The acl and aces can be
   created on top of base ACL module.  It described in CLI as the following:

           access-list ip iacl
           deny tcp host 10.10.10.1 host 10.10.10.255

                                 Figure 1

   Here is a simple the example of how to
   use 'augment' acl configuration xml:

<rpc message-id="101" xmlns:nc="urn:cisco:params:xml:ns:yang:ietf-acl:1.0">
// replace with an XPath expression which extends instances of IANA namespace when assigned
<edit-config>
  <target>
    <running/>
  </target>
  <config>
    <top xmlns="http://example.com/schema/1.2/config">
      <access-lists>
        <access-list>
        <access-control-list-name>sample-ip-acl</access-control-list-name>
        <access-list-entries>
          <access-list-entry>
          <rule-name>telnet-block-rule</rule-name>
          <matches>
            <destination-ipv4-address>10.10.10.255/24</destination-ipv4-address>
            <source-ipv4-address>10.10.10.1/24</source-ipv4-address>
          </matches>
          <actions>
          <deny/>
          </actions>
          </access-list-entry>
        </access-list-entries>
        </access-list>
      </access-lists>
    </top>
  </config>
</edit-config>
</rpc>

                                 Figure 2

4.4.  Port Range Usage Example

   When a
   particular type.  In this example, all /ietf-acl:access-list/ietf-
   acl:access-list-entries/ietf-acl:matches lower-port and an upper-port are augmented both present, it represents a
   range between lower-port and upper-port with both the lower-port and
   upper-port are included.  When only a new
   choice, protocol-payload-choice.  The protocol-payload-choice uses lower-port presents, it
   represents a
   grouping single port.

   With the follow XML snippet:

                        <source-port-range>
                          <lower-port>16384</lower-port>
                          <upper-port>16387</upper-port>
                        </source-port-range>

   This represents source ports 16384,16385, 16386, and 16387.

   With the follow XML snippet:

                         <source-port-range>
                           <lower-port>16384</lower-port>
                           <upper-port>65535</upper-port>
                         </source-port-range>

   This represents source ports greater than/equal to 16384.

   With the follow XML snippet:

                         <source-port-range>
                           <lower-port>21</lower-port>
                         </source-port-range>

   This represents port 21.

5.  Linux nftables

   As Linux platform is becoming more popular as networking platform,
   the Linux data model is changing.  Previously ACLs in Linux were
   highly protocol specific and different utilities were used for it
   (iptables, ip6tables, arptables, ebtables).  Recently, this has
   changed and a single utility, nftables, has been provided.  This
   utility follows very similarly the same base model as proposed in
   this draft.  The nftables support input and output ACEs and each ACE
   can be defined with an enumeration match and action.

6.  Security Considerations

   The YANG module defined in this memo is designed to be accessed via
   the NETCONF protocol [RFC6241] [RFC6241].  The lowest NETCONF layer
   is the secure transport layer and the mandatory-to-implement secure
   transport is SSH [RFC6242] [RFC6242].  The NETCONF access control
   model [RFC6536] [RFC6536] provides the means to restrict access for
   particular NETCONF users to a pre-configured subset of all supported available
   NETCONF protocol values.  In
   other example, /ietf-acl:access-list/ietf-acl:access-list-entries/
   ietf-acl:actions operations and content.

   There are augmented with new choice of actions.  Here is
   an inclusive list of cases listed within a choice statement.

    module newco-acl {
      yang-version 1;

      namespace "urn:newco:params:xml:ns:yang:newco-acl";

      prefix newco-acl;

      import ietf-acl {
        prefix "ietf-acl";
      }

      revision 2014-05-21{
        description "creating newo proprietary extensions number of data nodes defined in the YANG module which 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 ietf-acl model";
      }
      augment "/ietf-acl:access-lists/ietf-acl:access-list
      /ietf-acl:access-list-entries/ietf-acl:access-list-entry/ietf-acl:matches" {
        description "Newco proprietry simple filter matches";
        choice protocol-payload-choice { 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:

   /ietf-acl:access-lists/access-list/access-list-entries: This list protocol-payload {
            key value-keyword;
            ordered-by user;
            description "Match protocol payload";
            uses match-simple-payload-protocol-value;
          }
        }
      }

      augment "/ietf-acl:access-lists/ietf-acl:access-list
      /ietf-acl:access-list-entries/ietf-acl:access-list-entry/ietf-acl:actions" {
        description "Newco proprietary simple filter actions";
        choice action {
          case count {
            description "Count
   specifies all the packet in configured access list entries on the named counter";
              leaf count {
                type string;
              }
            }
          case policer {
            description "Name of policer device.
   Unauthorized write access to use this list can allow intruders to rate-limit traffic";
            leaf policer {
              type string;
            }
          }
          case hiearchical-policer {
            description "Name of hierarchical policer access
   and control the system.  Unauthorized read access to use this list can
   allow intruders to rate-limit traffic";
            leaf hierarchitacl-policer{ spoof packets with authorized addresses thereby
   compromising the system.

7.  IANA Considerations

   This document registers a URI in the IETF XML registry [RFC3688]
   [RFC3688].  Following the format in RFC 3688, the following
   registration is requested to be made:

   URI: urn:ietf:params:xml:ns:yang:ietf-acl

   URI: urn:ietf:params:xml:ns:yang:ietf-packet-fields

   Registrant Contact: The IESG.

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

   This document registers a YANG module in the YANG Module Names
   registry [RFC6020].

   name: ietf-acl namespace: urn:ietf:params:xml:ns:yang:ietf-acl
   prefix: ietf-acl reference: RFC XXXX
   name: ietf-packet-fields namespace: urn:ietf:params:xml:ns:yang:ietf-
   packet-fields prefix: ietf-packet-fields reference: RFC XXXX

8.  Acknowledgements

   Alex Clemm, Andy Bierman and Lisa Huang started it by sketching out
   an initial IETF draft in several past IETF meetings.  That draft
   included an ACL YANG model structure and a rich set of match filters,
   and 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
   drafts that made the draft went into IETF charter.

   Dean Bogdanovic, Kiran Agrahara Sreenivasa, Lisa Huang, and Dana
   Blair each evaluated the YANG model in previous draft separately and
   then work together, to created a new ACL draft that can be supported
   by different vendors.  The new draft removes vendor specific
   features, and gives examples to allow vendors to extend in their own
   proprietary ACL.  The earlier draft was superseded with the new one
   that received more participation from many vendors.

9.  References

9.1.  Normative References

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", RFC 6020,
              October 2010.

   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)", RFC
              6241, June 2011.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, June 2011.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536, March
              2012.

9.2.  Informative References

   [RFC5101]  Claise, B., "Specification of the IP Flow Information
              Export (IPFIX) Protocol for the Exchange of IP Traffic
              Flow Information", RFC 5101, January 2008.

Appendix A.  Extending ACL model examples

A.1.  Example of extending existing model for route filtering

   With proposed modular design, it is easy to extend the model with
   other features.  Those features can be standard features, like route
   filters.  Route filters match on specific IP addresses or ranges of
   prefixes.  Much like ACLs, they include some match criteria and
   corresponding match action(s).  For that reason, it is very simple to
   extend existing ACL model with route filtering.  The combination of a
   route prefix and prefix length along with the type string;
            }
          }
        }
      }

      augment "/ietf-acl:access-lists/ietf-acl:access-list" {
        container default-actions {
          description "Actions of match
   determines how route filters are evaluated against incoming routes.
   Different vendors have different match types and in this model we are
   using only ones that occur if no access-list entry is matched.";
          leaf deny {
            type empty;
          }
        }
      }

      grouping match-simple-payload-protocol-value {
         leaf value-keyword {
           description "(null)";
           type enumeration are common across all vendors participating in
   this draft.  As in this example, the base ACL model can be extended
   with company proprietary extensions, described in the next section.

<CODE BEGINS> file "std-ext-route-filter@2015-02-14.yang"

module std-ext-route-filter {
             enum icmp
  yang-version 1;

  namespace "urn:ietf:params:xml:ns:yang:ietf-route-filter";

  prefix std-ext-route-filter;

  import ietf-inet-types {
               description "Internet Control Message Protocol";
    prefix "inet";
  }
             enum icmp6

  import ietf-acl {
               description "Internet Control Message Protocol Version 6";
    prefix "ietf-acl";
  }
             enum range {
  organization
  "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

  contact
  "WG Web: http://tools.ietf.org/wg/netmod/
  WG List: netmod@ietf.org

  WG Chair: Juergen Schoenwaelder
  j.schoenwaelder@jacobs-university.de

  WG Chair: Tom Nadeau
  tnadeau@lucidvision.com

  Editor: Dean Bogdanovic
  deanb@juniper.net
  Editor: Kiran Agrahara Sreenivasa
  kkoushik@brocade.com

  Editor: Lisa Huang
  yihuan@cisco.com

  Editor: Dana Blair
  dblair@cisco.com";

  description "Range of values";
             }
           }
         }
       }
    }

   Dratf authors expect that different vendors will provide their own
   yang models "
    This module describes route filter as in the example above, which is the extension a collection of the
   base model

4.4.  An ACL Example

   Requirement: Deny All traffic from 1.1.1.1 bound for host 2.2.2.2
   from leaving.

   In order
    match prefixes. When specifying a match prefix, you
    can specify an exact match with a particular route or
    a less precise match. You can configure either a
    common action that applies to achieve the requirement, an name access control entire list is
   needed.  The acl and aces can be described in CLI as or an
    action associated with each prefix.
    ";

  revision 2015-02-14 {
    description "creating Route-Filter extension model based on ietf-acl model";
    reference " ";
  }

  augment "/ietf-acl:access-lists/ietf-acl:access-list
    /ietf-acl:access-list-entries/
    ietf-acl:access-list-entry/ietf-acl:matches"{
    description "
      This module augments the following:

           access-list ip iacl
           deny tcp host 1.1.1.1 host 2.2.2.2

                                 Figure 1

   Here is matches container in the example acl configuration xml:

   <rpc message-id="101" xmlns:nc="urn:cisco:params:xml:ns:yang:ietf-acl:1.0">
 // replace ietf-acl
      module with IANA namespace when assigned
   <edit-config>
 <target>
   <running/>
 </target>
 <config>
   <top xmlns="http://example.com/schema/1.2/config">
    <access-lists>
      <access-list>
        <acl-name>sample-ip-acl</acl-name>
        <access-list-entries>
           <access-list-entry>
            <rule-name>telnet-block-rule</rule-name>
            <matches>
              <destination-ipv4-address>2.2.2.2/32</destination-ipv4-address>
              <source-ipv4-address>1.1.1.1/32</source-ipv4-address>
            </matches>
            <actions>
              <deny/>
            </actions>
          </access-list-entry>
        </access-list-entries>
       </access-list>
     </access-lists>
   </top>
 </config>
   </edit-config>
 </rpc>

                                 Figure 2

4.5.  Port Range Usage Example

   When a lower-port and an upper-port are both present, it represents a route filter specific actions
      ";
    choice route-prefix{
      description "Define route filter match criteria";
      case range {
        description "
        Route falls between lower-port and upper-port with both the lower-port lower prefix/prefix-length and
   upper-port are included.  When only a lower-port presents, it
   represents a single port.

   With the follow XML snippet:

   <source-port-range>
       <lower-port>16384</lower-port>
       <upper-port>16387</upper-port>
   </source-port-range>

   This represents source ports 16384,16385, 16386, and 16387.

   With upper
        prefix/prefix-length.
        ";
        choice ipv4-range {
          description "Defines the follow XML snippet:

   <source-port-range>
       <lower-port>16384</lower-port>
       <upper-port>65535</upper-port>
   </source-port-range>

   This represents source ports greater than/equal to 16384.

   With lower IPv4 prefix/prefix range";
          leaf v4-lower-bound {
            type inet:ipv4-prefix;
            description "Defines the lower IPv4 prefix/prefix length";
          }
          leaf v4-upper-bound {
            type inet:ipv4-prefix;
            description "Defines the upper IPv4 prefix/prefix length";
          }
        }
        choice ipv6-range {
          description "Defines the IPv6 prefix/prefix range";
          leaf v6-lower-bound {
            type inet:ipv6-prefix;
            description "Defines the lower IPv6 prefix/prefix length";
          }
          leaf v6-upper-bound {
            type inet:ipv6-prefix;
            description "Defines the follow XML snippet:

   <source-port-range>
       <lower-port>21</lower-port>
   </source-port-range>

   This represents port 21.

5.  Example upper IPv6 prefix/prefix length";
          }
        }
      }
    }
  }
}
<CODE ENDS>

A.2.  A company proprietary module example

   Module "newco-acl" is an example of extending existing company proprietary model for route filtering

   With proposed modular design, it is easy that
   augments "ietf-acl" module.  It shows how to extend the model use 'augment' with
   other features.  Those features can be standard features, like route
   filters.  Route filters an
   XPath expression to add additional match on specific IP addresses criteria, action criteria,
   and default actions when no ACE matches found.  All these are company
   proprietary extensions or ranges of
   prefixes.  Much like ACLs, they include some match criteria system feature extensions. "newco-acl" is
   just an example and
   corresponding match action(s).  For that reason, it is very simple expected from vendors to
   extend existing ACL model with route filtering. create their own
   proprietary models.

   The combination of a
   route prefix and prefix length along with following figure is the type tree structure of match
   determines how route filters are evaluated against incoming routes.
   Different vendors have different match types and in newco-acl.  In this model we are
   using only ones that
   example, ietf-acl:access-lists/ietf-acl:access-list/ietf-acl:access-
   list-entries/ietf-acl:access-list-entry/ietf-acl:matches: are common across
   augmented with a new choice, protocol-payload-choice.  The protocol-
   payload-choice uses a grouping with an enumeration of all vendors participating in
   this draft.  As in this supported
   protocol values.  In other example, the base ACL model can be extended ietf-acl:access-lists/ietf-acl
   :access-list/ietf-acl:access-list-entries/ietf-acl:access-list-entry/
   ietf-acl:actions are augmented with company proprietary extensions, described in the next section. new choice of actions.

   module: newco-acl
   augment /ietf-acl:access-lists/ietf-acl:access-list
     /ietf-acl:access-list-entries/
     ietf-acl:access-list-entry/ietf-acl:matches:
       +--rw (protocol-payload-choice)?
         +--:(protocol-payload)
           +--rw protocol-payload* [value-keyword]
             +--rw value-keyword    enumeration
   augment /ietf-acl:access-lists/ietf-acl:access-list
     /ietf-acl:access-list-entries/
     ietf-acl:access-list-entry/ietf-acl:actions:
       +--rw (action)?
         +--:(count)
         |  +--rw count?                   string
         +--:(policer)
         |  +--rw policer?                 string
         +--:(hiearchical-policer)
           +--rw hierarchitacl-policer?   string
   augment /ietf-acl:access-lists/ietf-acl:access-list:
     +--rw default-actions
       +--rw deny?   empty

<CODE BEGINS> file "newco-acl@2015-03-04.yang"

module ietf-route-filter newco-acl {
  yang-version 1;

  namespace "urn:ietf:params:xml:ns:yang:ietf-route-filter";

      prefix ietf-route-filter;

      import ietf-inet-types { "urn:newco:params:xml:ns:yang:newco-acl";

  prefix "ietf-types";
      } newco-acl;

  import ietf-acl {
    prefix "ietf-acl";
  }
      organization
        "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

      contact
        "WG Web: http://tools.ietf.org/wg/netmod/
        WG List: netmod@ietf.org

        WG Chair: Juergen Schoenwaelder
        j.schoenwaelder@jacobs-university.de

        WG Chair: Tom Nadeau
        tnadeau@lucidvision.com

        Editor: Dean Bogdanovic
        deanb@juniper.net

        Editor: Kiran Agrahara Sreenivasa
        kkoushik@brocade.com

        Editor: Lisa Huang
        yihuan@cisco.com

        Editor: Dana Blair
        dblair@cisco.com";

      description "
              This module describes route filter as a collection of
              match prefixes. When specifying a match prefix, you
              can specify an exact match with a particular route or
              a less precise match. You can configure either a
              common action that applies to the entire list or an
              action associated with each prefix.
              ";

  revision 2014-08-15 { 2015-03-04{
    description "creating Route-Filter NewCo proprietary extensions to ietf-acl model";
        reference " ";
  }

  augment "/ietf-acl:access-list/ietf-acl:access-list-entries/ietf-acl:matches"{ "/ietf-acl:access-lists/ietf-acl:access-list
    /ietf-acl:access-list-entries/
      ietf-acl:access-list-entry/ietf-acl:matches" {
    description "
                This module augments the matches container in the ietf-acl
                module with route "Newco proprietary simple filter specific actions
            "; matches";
    choice route-prefix{ protocol-payload-choice {
      list protocol-payload {
        key value-keyword;
        ordered-by user;
        description "Define route filter match criteria";
          case range "Match protocol payload";
        uses match-simple-payload-protocol-value;
      }
    }
  }

  augment "/ietf-acl:access-lists/ietf-acl:access-list/ietf-acl:access-list-entries/ietf-acl:access-list-entry/ietf-acl:actions" {
    description "

          Route falls between the lower prefix/prefix-length and the upper
          prefix/prefix-length.
          "; "Newco proprietary simple filter actions";
    choice ipv4-range action {
      case count {
        description "Defines "Count the lower IPv4 prefix/prefix range"; packet in the named counter";
        leaf v4-lower-bound count {
          type ietf-types:ipv4-prefix;
                description "Defines the lower IPv4 prefix/prefix length"; string;
        }
      }
      case policer {
        description "Name of policer to use to rate-limit traffic";
        leaf v4-upper-bound policer {
          type ietf-types:ipv4-prefix; string;
        }
      }
      case hiearchical-policer {
        description "Defines the upper IPv4 prefix/prefix length"; "Name of hierarchical policer to use to
        rate-limit traffic";
        leaf hierarchitacl-policer{
          type string;
        }
      }
        choice ipv6-range
    }
  }

  augment "/ietf-acl:access-lists/ietf-acl:access-list" {
              description "Defines the IPv6 prefix/prefix range";
          leaf v6-lower-bound
    container default-actions {
            type ietf-types:ipv6-prefix;
      description "Defines the lower IPv6 prefix/prefix length";
          } "Actions that occur if no access-list entry is matched.";
      leaf v6-upper-bound deny {
        type ietf-types:ipv6-prefix;
            description "Defines the upper IPv6 prefix/prefix length";
          }
        }
          } empty;
      }
    }
  }

6.  Linux nftables

   As Linux platform is becoming more popular as networking platform,
   the Linux data model is changing.  Previously ACLs in Linux were
   highly protocol specific and different utilities were used for it
   (iptables, ip6tables, arptables, ebtables).  Recently, this has
   changed and a single utility, nftables, has been provided.  This
   utility follows very similarly the same base model as proposed in
   this draft.  The nftables support input and output ACEs and each ACE
   can be defined with match and action.

7.  Security Considerations

   The YANG module defined in this memo is designed to be accessed via
   the NETCONF protocol [RFC6241] [RFC6241].  The lowest NETCONF layer
   is the secure transport layer and the mandatory-to-implement secure
   transport is SSH [RFC6242] [RFC6242].  The NETCONF access control
   model [RFC6536] [RFC6536] provides the means to restrict access for
   particular NETCONF users to a pre-configured subset of all available
   NETCONF protocol operations and content.

   There are a number of data nodes defined in the YANG module which 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.

   TBD: List specific Subtrees and data nodes and

  grouping match-simple-payload-protocol-value {
    leaf value-keyword {
      description "(null)";
      type enumeration {
        enum icmp {
          description "Internet Control Message Protocol";
        }
        enum icmp6 {
          description "Internet Control Message Protocol Version 6";

        }
        enum range {
          description "Range of values";
        }
      }
    }
  }
}

    <CODE ENDS>

   Draft authors expect that different vendors will provide their sensitivity/
   vulnerability.

8.  IANA Considerations

   This document registers a URI in the IETF XML registry [RFC3688]
   [RFC3688].  Following the format own
   yang models as in RFC 3688, the following
   registration is requested to be made:

   URI: urn:ietf:params:xml:ns:yang:ietf-acl

   Registrant Contact: The IESG.

   XML: N/A, the requested URI example above, which is an XML namespace.

   This document registers a YANG module in the YANG Module Names
   registry [RFC6020].

   name: ietf-acl namespace: urn:ietf:params:xml:ns:yang:ietf-acl
   prefix: ietf-acl reference: RFC XXXX

9.  Acknowledgements

   Alex Clemm, Andy Bierman and Lisa Huang started it by sketching out
   an initial IETF draft in several past IETF meetings.  That draft
   included an ACL YANG model structure and a rich set extension of match filters,
   and 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
   drafts that made the draft went into IETF charter.

   Dean Bogdanovic, Kiran Agrahara Sreenivasa, Lisa Huang, and Dana
   Blair each evaluated the YANG
   base model in previous draft separately and
   then work together,

A.3.  Attaching Access Control List to created interfaces

   Access control list typically does not exist in isolation.  Instead,
   they are associated with a new ACL draft that can be supported
   by different vendors.  The new draft removes vendor specific
   features, and gives examples certain scope in which they are applied,
   for example, an interface of a set of interfaces.  How to allow vendors attach an
   SPF to extend in their own
   proprietary ACL.  The earlier draft was superseded with an interface (or other system artifact) is outside the new one
   that received more participation from many vendors.

10.  Change log [RFC Editor: Please remove]

11.  References

11.1.  Normative References

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for scope
   of this model, as it depends on the
              Network Configuration Protocol (NETCONF)", RFC 6020,
              October 2010.

   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)", RFC
              6241, June 2011.

   [RFC6242]  Wasserman, M., "Using specifics of the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, June 2011.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536, March
              2012.

11.2.  Informative References

   [RFC5101]  Claise, B., "Specification system model
   that is being applied.  However, in general, the general design
   pattern will involved adding a dada node with a reference, or set of
   references, to ACLs that are to be applied to the IP Flow Information
              Export (IPFIX) Protocol for interface.  For
   this purpose, the Exchange type definition "access-control-list-ref" can be
   used.

   This is an example of IP Traffic
              Flow Information", RFC 5101, January 2008. attaching an access control list to an
   interface.

                        <CODE BEGINS> file "interface model augmentation with ACL
                            @2015-03-04.yang"
  import ietf-acl {
    prefix "ietf-acl";
  }
  import ietf-interface {
    prefix "ietf-if";
  }
  import ietf-yang-types {
    prefix "yang";
  }

  augment "/ietf-if:interfaces/ietf-if:interface" {
    description "Apply acl to interfaces";
    container acl{
      description "ACL related properties.";
      leaf acl-name {
        type ietf-acl:access-control-list-ref;
        mandatory true;
        description "Access Control List name.";
      }
      leaf match-counter {
        type yang:counter64;
        config false;
        description "Total match count for access control list ";
      }
      choice direction {
        leaf in { type empty;}
        leaf out { type empty;}
      }
    }
  }
    <CODE ENDS>

Authors' Addresses

   Dean Bogdanovic
   Juniper Networks

   Email: deanb@juniper.net

   Kiran Agrahara Sreenivasa
   Brocade Communications System

   Email: kkoushik@brocade.com
   Lisa Huang
   Cisco Systems

   Email: yihuan@cisco.com

   Dana Blair
   Cisco Systems

   Email: dblair@cisco.com