Skip to main content

A Yang Data Model for IGMP/MLD Proxy
draft-zhao-pim-igmp-mld-proxy-yang-00

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Authors Hongji Zhao , Xufeng Liu , Yisong Liu , Mahesh Sivakumar , Anish Peter
Last updated 2018-09-03
Replaced by draft-ietf-pim-igmp-mld-proxy-yang, draft-ietf-pim-igmp-mld-proxy-yang, RFC 9398
RFC stream (None)
Formats
Additional resources
Stream Stream state (No stream defined)
Consensus boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date (None)
Responsible AD (None)
Send notices to (None)
draft-zhao-pim-igmp-mld-proxy-yang-00
PIM Working Group                                               H. Zhao
Internet Draft                                                 Ericsson
Intended status: Standards Track                                 X. Liu
Expires: March 2, 2019                                            Jabil
                                                                 Y. Liu
                                                                 Huawei
                                                           M. Sivakumar
                                                                Juniper
                                                               A. Peter
                                                              Individual

                                                       September 3, 2018

                   A Yang Data Model for IGMP/MLD Proxy
                 draft-zhao-pim-igmp-mld-proxy-yang-00.txt

Abstract

   This document defines a YANG data model that can be used to
configure and manage Internet Group Management Protocol (IGMP) or
Multicast Listener Discovery (MLD) proxy devices. The YANG module in
this document conforms to Network Management Datastore Architecture
(NMDA).

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), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

Zhao & Liu, etc         Expires March 2, 2019                  [Page 1]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

   This Internet-Draft will expire on March 2, 2019.

Copyright Notice

   Copyright (c) 2018 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...................................................3
      1.1. Terminology...............................................3
      1.2. Tree Diagrams.............................................3
   2. Design of Data Model...........................................3
      2.1. Overview..................................................4
      2.2. Augment /if:interfaces/if:interface.......................4
      2.3. Augment /rt:routing/rt:control-plane-protocols/rt:control-
      plane-protocol/igmp-mld:igmp...................................5
      2.4. Augment /rt:routing/rt:control-plane-protocols/rt:control-
      plane-protocol/igmp-mld:mld....................................5
   3. IGMP/MLD Proxy YANG Module.....................................6
   4. Security Considerations.......................................13
   5. IANA Considerations...........................................14
   6. Normative References..........................................15
   Authors' Addresses...............................................17

Zhao & Liu, etc         Expires March 2, 2019                  [Page 2]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

1. Introduction

This document defines a YANG [RFC6020] data model for the management of
Internet Group Management Protocol (IGMP) or Multicast Listener
Discovery (MLD) proxy devices.

The YANG module in this document conforms to the Network Management
Datastore Architecture defined in [RFC8342]. The "Network Management
Datastore Architecture" (NMDA) adds the ability to inspect the current
operational values for configuration, allowing clients to use identical
paths for retrieving the configured values and the operational values.

1.1. 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].

The terminology for describing YANG data models is found in [RFC6020].

1.2. Tree Diagrams

A simplified graphical representation of the data model is used in this
document.  The meaning of the symbols in these diagrams is as follows:

   o Brackets "[" and "]" enclose list keys.

   o Abbreviations before data node names: "rw" means configuration
   (read-write), and "ro" means state data (read-only).

   o Symbols after data node names: "?" means an optional node, "!"
   means a presence container, and "*" denotes a list and leaf-list.

   o Parentheses enclose choice and case nodes, and case nodes are also
   marked with a colon (":").

   o Ellipsis ("...") stands for contents of subtrees that are not
   shown.

2. Design of Data Model

The model covers Considerations for Internet Group Management Protocol
(IGMP) / Multicast Listener Discovery (MLD) - Based Multicast Forwarding
("IGMP/MLD Proxying") [RFC4605].

Zhao & Liu, etc         Expires March 2, 2019                  [Page 3]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

The goal of this document is to define a data model that provides a
common user interface to IGMP/MLD proxy.  This document provides freedom
for vendors to adapt this data model to their product implementations.

2.1. Overview

The IGMP/MLD proxy YANG module defined in this document has all the
common building blocks for the IGMP/MLD proxy protocol.

The YANG module augments /if:interfaces/if:interface to enable IGMP/MLD
proxy and configure other related parameters. It also augments
/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/igmp-
mld:igmp and /rt:routing/rt:control-plane-protocols/rt:control-plane-
protocol/igmp-mld:mld to configure the global parameters and retrieve
the IGMP/MLD proxy group information.

This YANG module follows the Guidelines for YANG Module Authors (NMDA)
[draft-dsdt-nmda-guidelines-01]. This NMDA ("Network Management
Datastore Architecture") architecture provides an architectural
framework for datastores as they are used by network management
protocols such as NETCONF [RFC6241], RESTCONF [RFC8040] and the YANG
[RFC7950] data modeling language.

2.2. Augment /if:interfaces/if:interface

A proxy device performing IGMP/MLD-based forwarding has a single
upstream interface and one or more downstream interfaces [RFC4605]. The
YANG module augments /if:interfaces/if:interface and you can enable
IGMP/MLD proxy on the upstream interface.

module: ietf-igmp-mld-proxy
  augment /if:interfaces/if:interface:
    +--rw igmp-proxy
    |  +--rw enable?                 boolean
    |  +--rw require-router-alert?   boolean {require-router-alert}?
    |  +--rw query-interval?         uint16
    |  +--rw robustness-variable?    uint8
    |  +--rw version?                uint8
    +--rw mld-proxy
       +--rw enable?                 boolean
       +--rw require-router-alert?   boolean {require-router-alert}?
       +--rw query-interval?         uint16
       +--rw robustness-variable?    uint8
       +--rw version?                uint8

Zhao & Liu, etc         Expires March 2, 2019                  [Page 4]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

2.3. Augment /rt:routing/rt:control-plane-protocols/rt:control-plane-
   protocol/igmp-mld:igmp

The YANG module augments /rt:routing/rt:control-plane-
protocols/rt:control-plane-protocol/igmp-mld:igmp to configure source
lifetime globally and retrieve the IGMP proxy group information for
(S,G) or (*,G).

module: ietf-igmp-mld-proxy
  augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol
      /igmp-mld:igmp:
    +--rw proxy
       +--rw source-lifetime?   uint32
       +--ro group* [group-address]
          +--ro group-address    inet:ipv4-address
          +--ro up-time?         uint32
          +--ro filter-mode?     enumeration
          +--ro source* [source-address]
             +--ro source-address          inet:ipv4-address
             +--ro up-time?                uint32
             +--ro upstream-interface?     if:interface-ref
             +--ro downstream-interface*   if:interface-ref

2.4. Augment /rt:routing/rt:control-plane-protocols/rt:control-plane-
   protocol/igmp-mld:mld

The YANG module augments /rt:routing/rt:control-plane-
protocols/rt:control-plane-protocol/igmp-mld:mld to configure source
lifetime globally and retrieve the MLD proxy group information for
(S,G) or (*,G).

module: ietf-igmp-mld-proxy
  augment /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/
       igmp-mld:mld:
    +--rw proxy
       +--rw source-lifetime?   uint32
       +--ro group* [group-address]
          +--ro group-address    inet:ipv6-address
          +--ro up-time?         uint32
          +--ro filter-mode?     enumeration
          +--ro source* [source-address]
             +--ro source-address          inet:ipv6-address
             +--ro up-time?                uint32
             +--ro upstream-interface?     if:interface-ref
             +--ro downstream-interface*   if:interface-ref

Zhao & Liu, etc         Expires March 2, 2019                  [Page 5]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

3. IGMP/MLD Proxy YANG Module

<CODE BEGINS> file ietf-igmp-mld-proxy@2018-08-29.yang
module ietf-igmp-mld-proxy {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-igmp-mld-proxy";
  // replace with IANA namespace when assigned
  prefix imp;

  import ietf-inet-types {
    prefix inet;
  }

  import ietf-interfaces {
    prefix if;
  }

  import ietf-routing {
    prefix rt;
  }

  import ietf-igmp-mld {
    prefix igmp-mld;
  }

  organization
    "IETF PIM Working Group";

  contact
    "WG Web:   <http://tools.ietf.org/wg/pim/>
     WG List:  <mailto:pim@ietf.org>

     Editors:  Hongji Zhao
               <mailto:hongji.zhao@ericsson.com>

               Xufeng Liu
               <mailto:xufeng.liu.ietf@gmail.com>

               Yisong Liu
               <mailto:liuyisong@huawei.com>

               Anish Peter
               <mailto:anish.ietf@gmail.com>

               Mahesh Sivakumar
               <mailto:sivakumar.mahesh@gmail.com>

    ";

  description
    "The module defines a collection of YANG definitions common for

Zhao & Liu, etc         Expires March 2, 2019                  [Page 6]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

     all Internet Group Management Protocol (IGMP) and Multicast
     Listener Discovery (MLD) Proxy devices.

     Copyright (c) 2018 IETF Trust and the persons identified as
     authors of the code.  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.";

  revision 2018-08-29 {
    description
      "Initial revision.";
    reference
      "RFC XXXX: A YANG Data Model for IGMP and MLD Proxy";
  }

  /*
   * Features
   */
  feature require-router-alert {
    description
      "Support configuration of require-router-alert.";
  }

  /*
   * Groupings
   */
  grouping per-interface-config-attributes {

    description "Config attributes under interface view";

    leaf enable {
      type boolean;
      default false;
      description
        "Set the value to true to enable IGMP/MLD proxy";
    }

    leaf require-router-alert {
      if-feature require-router-alert;

Zhao & Liu, etc         Expires March 2, 2019                  [Page 7]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

      type boolean;
     default false;
      description
        "When the value is true, router alert should exist
       in the IP head of IGMP or MLD packet.";
    }

    leaf query-interval {
      type uint16;
      units seconds;
      default 125;
      description
        "The Query Interval is the interval between General Queries
         sent by the Querier.";
      reference "RFC3376. Sec. 4.1.7, 8.2, 8.14.2.";
    }

    leaf robustness-variable {
      type uint8 {
        range "1..7";
      }
      default 2;
      description
        "Querier's Robustness Variable allows tuning for the
       expected packet loss on a network.";
      reference "RFC3376. Sec. 4.1.6, 8.1, 8.14.1.";
    }

  } // per-interface-config-attributes

  grouping global-config-attributes {

    description "Config attributes globally";

   leaf source-lifetime {
      type uint32;
      units seconds;
      description
        "The life time for (S,G).";
    }

  } // global-config-attributes

  grouping state-group-attributes {
    description
      "State group attributes";

   leaf up-time {
      type uint32;
      units seconds;
      description

Zhao & Liu, etc         Expires March 2, 2019                  [Page 8]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

        "The elapsed time for (S,G) or (*,G).";
    }

    leaf filter-mode {
      type enumeration {
        enum "include" {
          description
            "In include mode, reception of packets sent
             to the specified multicast address is requested
             only from those IP source addresses listed in the
             source-list parameter";
        }
        enum "exclude" {
          description
            "In exclude mode, reception of packets sent
             to the given multicast address is requested
             from all IP source addresses except those
             listed in the source-list parameter.";
        }
      }
      description
        "Filter mode for a multicast group,
         may be either include or exclude.";
    }
  } // state-group-attributes

  grouping up-down-stream-interfaces {
    description
      "upstream and downstream interfaces";

   leaf upstream-interface {
      type if:interface-ref;
      description
        "Upstream interface";
    }

    leaf-list downstream-interface {
      type if:interface-ref;
      description
       "Downstream interfaces for each upstream-interface";
    }

  } // up-down-stream-interfaces

 /* augments */

  augment "/if:interfaces/if:interface" {
    description
     "Augment interface for enable IGMP/MLD proxy
      which only fit for interface view.";

Zhao & Liu, etc         Expires March 2, 2019                  [Page 9]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

    container igmp-proxy {
      description
        "Configure igmp proxy under the upstream interface";

      uses per-interface-config-attributes;

     leaf version {
        type uint8 {
          range "1..3";
        }
       default 2;
        description "IGMP version.";
      }
    } // igmp-proxy

   container mld-proxy {
      description
        "Configure MLD proxy under the upstream interface";

      uses per-interface-config-attributes;

     leaf version {
          type uint8 {
            range "1..2";
          }
        default 1;
          description "MLD version.";
        }
    } // mld-proxy
  }

  augment "/rt:routing/rt:control-plane-protocols/"
    +"rt:control-plane-protocol/igmp-mld:igmp" {

   description
     "Augment IGMP to configure IGMP/MLD proxy globally";

   container proxy {
     description "IGMP proxy";

     uses global-config-attributes;

     list group {
        key "group-address";
        config false;
        description
          "Multicast group membership information
          that joined on the interface.";

        leaf group-address {
          type inet:ipv4-address;

Zhao & Liu, etc         Expires March 2, 2019                 [Page 10]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

          description
            "Multicast group address.";
        }

        uses state-group-attributes;

        list source {
          key "source-address";
          description
            "List of multicast source information
             of the multicast group.";

          leaf source-address {
            type inet:ipv4-address;
            description
              "Multicast source address";
          }

         leaf up-time {
            type uint32;
            units seconds;
            description
              "The elapsed time for (S,G) or (*,G).";
          }

        uses up-down-stream-interfaces;

        } // list source
      } // list group
    }
  }

  augment "/rt:routing/rt:control-plane-protocols/"
    +"rt:control-plane-protocol/igmp-mld:mld" {

   description
     "Augment MLD to configure IGMP/MLD proxy globally";

   container proxy {
     description "MLD proxy";

     uses global-config-attributes;

     list group {
        key "group-address";
        config false;
        description
          "Multicast group membership information
          that joined on the interface.";

        leaf group-address {

Zhao & Liu, etc         Expires March 2, 2019                 [Page 11]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

          type inet:ipv6-address;
          description
            "Multicast group address.";
        }

        uses state-group-attributes;

        list source {
          key "source-address";
          description
            "List of multicast source information
             of the multicast group.";

          leaf source-address {
            type inet:ipv6-address;
            description
              "Multicast source address";
          }

         leaf up-time {
            type uint32;
            units seconds;
            description
              "The elapsed time for (S,G) or (*,G).";
          }

        uses up-down-stream-interfaces;

        } // list source
      } // list group
    }
  }

}
<CODE ENDS>

Zhao & Liu, etc         Expires March 2, 2019                 [Page 12]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

4. Security Considerations

   The YANG module specified in this document defines a schema for data
   that is designed to be accessed via network management protocols 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
   [RFC5246].

   The NETCONF access control model [RFC6536] 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.

   There are a number of data nodes defined in this YANG module 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:

   /if:interfaces/if:interface/imp:igmp-proxy

   /if:interfaces/if:interface/imp:mld-proxy

   /rt:routing/rt:control-plane-protocols/rt:control-plane-
   protocol/igmp-mld:igmp/imp:proxy

   /rt:routing/rt:control-plane-protocols/rt:control-plane-
   protocol/igmp-mld:mld/imp:proxy

   Unauthorized access to any data node of these subtrees can adversely
   affect the IGMP/MLD proxy subsystem of both the local device and the
   network. This may lead to network malfunctions, delivery of packets
   to inappropriate destinations, and other problems.

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments. It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes. These are the subtrees and data
   nodes and their sensitivity/vulnerability:

   /if:interfaces/if:interface/imp:igmp-proxy

   /if:interfaces/if:interface/imp:mld-proxy

Zhao & Liu, etc         Expires March 2, 2019                 [Page 13]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

   /rt:routing/rt:control-plane-protocols/rt:control-plane-
   protocol/igmp-mld:igmp/imp:proxy

   /rt:routing/rt:control-plane-protocols/rt:control-plane-
   protocol/igmp-mld:mld/imp:proxy

   Unauthorized access to any data node of these subtrees can disclose
   the operational state information of IGMP/MLD proxy on this device.

5. IANA Considerations

   RFC Ed.: In this section, replace all occurrences of 'XXXX' with the
   actual RFC number (and remove this note).

   This document registers the following namespace URIs in the IETF XML

   registry [RFC3688]:

   --------------------------------------------------------------------

   URI: urn:ietf:params:xml:ns:yang:ietf-igmp-mld-proxy

   Registrant Contact: The IESG.

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

   --------------------------------------------------------------------

   This document registers the following YANG modules in the YANG
   Module Names registry [RFC7950]:

   --------------------------------------------------------------------

   name:         ietf-igmp-mld-proxy

   namespace:    urn:ietf:params:xml:ns:yang:ietf-igmp-mld-proxy

   prefix:       imp

   reference:    RFC XXXX

   --------------------------------------------------------------------

Zhao & Liu, etc         Expires March 2, 2019                 [Page 14]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

6. Normative References

   [RFC2236] Fenner, W., "Internet Group Management Protocol, Version
             2", RFC 2236, November 1997.

   [RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast
             Listener Discovery (MLD) for IPv6", RFC 2710, October 1999.

   [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
             Thyagarajan, "Internet Group Management Protocol, Version
             3", RFC 3376, October 2002.

   [RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery
             Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

   [RFC4604] Holbrook, H., Cain, B., and B. Haberman, "Using Internet
             Group Management Protocol Version 3 (IGMPv3) and Multicast
             Listener Discovery Protocol Version 2 (MLDv2) for Source-
             Specific Multicast", RFC 4604, August 2006.

   [RFC4605] B. Fenner, H. He, B. Haberman and H. Sandick, "Internet
             Group Management Protocol (IGMP) / Multicast Listener
             Discovery (MLD) - Based Multicast Forwarding ("IGMP/MLD
             Proxying")", RFC 4605, August 2006.

   [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
             IP", RFC 4607, August 2006.

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

   [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991,
             July 2013.

   [RFC8342] M. Bjorklund and J. Schoenwaelder, "Network Management
             Datastore Architecture (NMDA)", RFC 8342, March 2018.

   [RFC8343] M. Bjorklund, "A YANG Data Model for Interface Management",
             RFC 8343, March 2018.

   [draft-ietf-pim-igmp-mld-yang-06] X. Liu, F. Guo, M. Sivakumar, P.
             McAllister, A. Peter, "A YANG data model for Internet Group
             Management Protocol (IGMP) and Multicast Listener Discovery
             (MLD)", draft-ietf-pim-igmp-mld-yang-06, Oct 20, 2017.

   [draft-dsdt-nmda-guidelines-01] M. Bjorklund, J. Schoenwaelder, P.
             Shafer, K. Watsen, R. Wilton, "Guidelines for YANG Module
             Authors (NMDA)", draft-dsdt-nmda-guidelines-01, May 2017

Zhao & Liu, etc         Expires March 2, 2019                 [Page 15]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

   [draft-ietf-netmod-revised-datastores-03] M. Bjorklund, J.
             Schoenwaelder, P. Shafer, K. Watsen, R. Wilton, "Network
             Management Datastore Architecture", draft-ietf-netmod-
             revised-datastores-03, July 3, 2017

Zhao & Liu, etc         Expires March 2, 2019                 [Page 16]
Internet-Draft        IGMP/MLD Proxy Yang Module      September 3, 2018

Authors' Addresses

   Hongji Zhao
   Ericsson (China) Communications Company Ltd.
   Ericsson Tower, No. 5 Lize East Street,
   Chaoyang District Beijing 100102, P.R. China

   Email: hongji.zhao@ericsson.com

   Xufeng Liu
   Jabil
   8281 Greensboro Drive, Suite 200
   McLean VA 22102
   USA

   EMail: Xufeng.liu.ietf@gmail.com

   Yisong Liu
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing 100095
   China

   Email: liuyisong@huawei.com

   Anish Peter
   Individual

   EMail: anish.ietf@gmail.com

   Mahesh Sivakumar
   Cisco Systems
   510 McCarthy Boulevard
   Milpitas, California
   USA

   EMail: sivakumar.mahesh@gmail.com

Zhao & Liu, etc         Expires March 2, 2019                 [Page 17]