DHC Working Group                                        Narasimha                                               N. Swamy
Internet-Draft                                                     Nokia Networks
Updates: RFC 2131                                           January 2004
                                                       Expires July 2004 (if approved)                                  G. Halwasia
Intended status: Standards Track                             P. Jhingran
Expires: February 17, 2012                                 Cisco Systems
                                                         August 16, 2011

            Client Identifier option Option in DHCP Server Replies


   This document updates RFC2131 [RFC2131].  The changes to [RFC2131]
   defined in this draft clarifies the use of 'client identifier' option
   by the DHCP servers.  The clarification addresses the issues arising
   out of the point specified by [RFC2131] that the server replies
                   <draft-ietf-dhc-client-id-00.txt> 'MUST NOT'
   return client identifier' option to the client.


   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

Status of this Memo

   This document is an Internet-Draft and is submitted in full conformance with
   all the
   provisions of Section 10 of RFC2026. BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html. will expire on February 17, 2012.

Copyright Notice

   Copyright (C) The Internet Society (2003). (c) 2011 IETF Trust and the persons identified as the
   document authors.  All Rights Reserved.

Abstract rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Proposed Modification To [RFC2131]  . . . . . . . . . . . . . . 4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 4
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 5

1.  Introduction

   The Dynamic Host Configuration Protocol (DHCP) defined in [RFC2131]
   provides configuration parameters to hosts on a TCP/IP based network.
   DHCP is built on a client-server model, where designated DHCP server
   allocate network addresses and deliver configuration parameters to
   dynamically configured hosts.

   The changes to [RFC2131] defined in this document clarifies the use
   of 'client identifier' option by the
   clients and servers as mentioned in [RFC2131]. DHCP servers.  The clarification
   addresses the issue issues arising out of the point specified by [RFC2131]
   that the server 'MUST NOT' return client identifier' option to the

1.  Introduction

   In some cases,
   client may not be having valid hardware address value and thus facilitates DHCP relay agents and hosts to be filled in 'chaddr' field of the packet (one such example is process
   downstream DHCP messages (DHCPOFFER,DHCPACK and DHCPNAK) when a DHCP is used to assign IP addresses to Mobile phones). In this
   client sets the 'chaddr' field as zero in DHCP request messages.

2.  Problem Statement

   [RFC2131] specifies that a combination of 'client identifier' option, or
   'chaddr' and assigned network address constitute a unique identifier
   for the client's lease and are used by both the client and server use this field to uniquely
   identify the client with in a subnet. But lease referred in any DHCP messages.  [RFC2131] also
   specifies that the server "MUST NOT" return 'client identifier' in
   DHCPOFFER and DHCPACK messages.  DHCP relay agents and servers,
   following these recommendations MAY drop the DHCP packets in the
   absence of both 'client identifier' and 'chaddr'.

   In some cases, client may not be having valid hardware address value
   to be filled in 'chaddr' field of the packet and hence may set this
   field as zero.  One such example is when DHCP is used to assign IP
   address to a mobile phone or a tablet and where the 'chaddr' field is
   set to zero in DHCP request packets.  In such cases, client usually
   sets the 'client identifier' option field (to a value as permitted in
   [RFC2131]), and both client and server use this case, field to uniquely
   identify the client with in a subnet.

   Note that due to above mentioned recommendations in [RFC2131], valid
   downstream DHCP packets (DHCPOFFER, DHCPACK and DHCPNAK) from the
   server MAY get dropped at the DHCP relay agent in the absence of
   'client identifier' option when 'chaddr' field is set as zero.

   The problem may get aggravated when a client receives a response from server,
   the server without 'client identifier' and with 'chaddr' value set to
   zero, as it can't cannot guarantee that the response is intended for it. Note that
   This is because even though the 'xid' field is present to map
   responses with requests, this field alone can't guar-
   antee cannot guarantee that a
   particular response is for a particular client, as 'xid' values
   generated by multiple clients within a subnet need not be unique.

   This draft proposes modification to server behavior to addr-
   ess this problem.

2.  Terminology

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

   This document uses the following terms:

      o "DHCP client"

        A address these problems faced by DHCP relay
   agent and client is an Internet host using DHCP by proposing modification to obtain confi-
        guration parameters such as a network address.

      o "DHCP server"

        A DHCP server behavior.
   The proposed solution is an Internet host that returns configuration
        parameters to DHCP clients.

3.  Proposed modification to [RFC2131]

   If in line with DHCPv6 [RFC3315] where the
   server always includes the Client Identifier option in the Reply

3.  Proposed Modification To [RFC2131]

   If the 'client identifier' option is set in the a message received from a
   client, the server MUST return the 'client identifier' value option,
   unaltered, in its response message.

   Following table is extracted from section 4.3.1 of [RFC2131] and
   relevant fields are modified accordingly. accordingly to overcome the problems
   mentioned in this document.

   Option                    DHCPOFFER    DHCPACK            DHCPNAK
   ------                    ---------    -------            -------
   Client identifier         MAY          MAY                MAY

           Table 1:  Options used (if     MUST         MUST               MUST
     sent by DHCP servers client)
   Client identifier (if     MUST NOT     MUST NOT           MUST NOT
     not sent by client)

4.  IANA Considerations

   This memo asks the IANA for no new parameters.

5.  Security Considerations

   No known security considerations.

5.  Acknowledgments


6.  Acknowledgements

   The authors would like to thank Umesh Kulkarni, Harish Raghuveer and Hari Mallath Bernie Volz, Ted Lemon, Barr Hibbs
   for their support and feedback.

6.  References

   [RFC 951] Croft, B., Gilmore, J., "Bootstrap Protocol (BOOTP)", RFC
      951, September 1985.

   [RFC 1542] Wimer, W., "Clarifications and Extensions for insightful discussions on the
      Bootstrap Protocol", RFC 1542, October 1993.

   [RFC 2119] previous version of this

7.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC 2131]

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, March 1997.

   [RFC 2132] Alexander, S.,

   [RFC3315]  Droms, R., "DHCP Options Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and BOOTP Vendor
      Extensions", M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 2132, March 1997.

7.  Author's information 3315, July 2003.

Authors' Addresses

   Narasimha Swamy Nelakuditi
   Visiokatu 3
   Tampere,   33720

   Phone: +358 50487 2126
   Email: narasimha.nelakuditi@nokia.com

   Gaurav Halwasia
   Cisco Systems
   SEZ Unit, Cessna Business Park
   Sarjapur Marathalli Outer Ring Road
   Bangalore,   560103
   India Pvt Ltd
	#88, Gandhi Bazaar Main

   Phone: +91 80 4426 1321
   Email: ghalwasi@cisco.com

   Prashant Jhingran
   Cisco Systems
   SEZ Unit, Cessna Business Park
   Sarjapur Marathalli Outer Ring Road
	Bangalore - 560 004
   Bangalore,   560103

   Phone: +91 80 51189628 4426 1800
   Email: narasimha.nelakuditi@nokia.com

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