draft-ietf-dhc-client-id-02.txt   draft-ietf-dhc-client-id-03.txt 
DHC Working Group N. Swamy DHC Working Group N. Swamy
Internet-Draft Nokia Internet-Draft Nokia
Updates: 2131 (if approved) G. Halwasia Updates: 2131 (if approved) G. Halwasia
Intended status: Standards Track P. Jhingran Intended status: Standards Track P. Jhingran
Expires: September 13, 2012 Cisco Systems Expires: January 11, 2013 Cisco Systems
March 12, 2012 July 10, 2012
Client Identifier Option in DHCP Server Replies Client Identifier Option in DHCP Server Replies
draft-ietf-dhc-client-id-02 draft-ietf-dhc-client-id-03
Abstract Abstract
This document updates RFC2131 [RFC2131]. The changes to [RFC2131] This document updates RFC2131 [RFC2131]. The changes to [RFC2131]
defined in this draft clarifies the use of 'client identifier' option defined in this draft clarifies the use of 'client identifier' option
by the DHCP servers. The clarification addresses the issues arising by the DHCP servers. The clarification addresses the issues arising
out of the point specified by [RFC2131] that the server 'MUST NOT' out of the point specified by [RFC2131] that the server 'MUST NOT'
return client identifier' option to the client. return client identifier' option to the client.
Requirements Requirements
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 13, 2012. This Internet-Draft will expire on January 11, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 3
3. Proposed Modification To [RFC2131] . . . . . . . . . . . . . . 4 3. Proposed Modification To [RFC2131] . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . . 5 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1. Introduction
The Dynamic Host Configuration Protocol (DHCP) defined in [RFC2131] The Dynamic Host Configuration Protocol (DHCP) defined in [RFC2131]
provides configuration parameters to hosts on a TCP/IP based network. provides configuration parameters to hosts on a TCP/IP based network.
DHCP is built on a client-server model, where designated DHCP server DHCP is built on a client-server model, where designated DHCP server
allocate network addresses and deliver configuration parameters to allocate network addresses and deliver configuration parameters to
dynamically configured hosts. dynamically configured hosts.
The changes to [RFC2131] defined in this document clarifies the use The changes to [RFC2131] defined in this document clarifies the use
of 'client identifier' option by the DHCP servers. The clarification of 'client identifier' option by the DHCP servers. The clarification
addresses the issues arising out of the point specified by [RFC2131] addresses the issues (as mentioned in Problem Statement) arising out
that the server 'MUST NOT' return client identifier' option to the of the point specified by [RFC2131] that the server 'MUST NOT' return
client and thus facilitates DHCP relay agents and hosts to process client identifier' option to the client.
downstream DHCP messages (DHCPOFFER,DHCPACK and DHCPNAK) when a DHCP
client sets the 'chaddr' field as zero in DHCP request messages.
2. Problem Statement 2. Problem Statement
[RFC2131] specifies that a combination of 'client identifier' or [RFC2131] specifies that a combination of 'client identifier' or
'chaddr' and assigned network address constitute a unique identifier 'chaddr' and assigned network address constitute a unique identifier
for the client's lease and are used by both the client and server to for the client's lease and are used by both the client and server to
identify a lease referred in any DHCP messages. [RFC2131] also identify a lease referred in any DHCP messages. [RFC2131] also
specifies that the server "MUST NOT" return 'client identifier' in specifies that the server "MUST NOT" return 'client identifier' in
DHCPOFFER and DHCPACK messages. DHCP relay agents and servers, DHCPOFFER and DHCPACK messages. DHCP relay agents and servers,
following these recommendations MAY drop the DHCP packets in the following these recommendations MAY drop the DHCP packets in the
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'client identifier' option when 'chaddr' field is set as zero. 'client identifier' option when 'chaddr' field is set as zero.
The problem may get aggravated when a client receives a response from The problem may get aggravated when a client receives a response from
the server without 'client identifier' and with 'chaddr' value set to the server without 'client identifier' and with 'chaddr' value set to
zero, as it cannot guarantee that the response is intended for it. zero, as it cannot guarantee that the response is intended for it.
This is because even though the 'xid' field is present to map This is because even though the 'xid' field is present to map
responses with requests, this field alone cannot guarantee that a responses with requests, this field alone cannot guarantee that a
particular response is for a particular client, as 'xid' values particular response is for a particular client, as 'xid' values
generated by multiple clients within a subnet need not be unique. generated by multiple clients within a subnet need not be unique.
Lack of 'client identifier' option in DHCP reply messages also
affects the scenario where multiple DHCP clients may be running on
the same host sharing the same 'chaddr'.
This document attempts to address these problems faced by DHCP relay This document attempts to address these problems faced by DHCP relay
agent and client by proposing modification to DHCP server behavior. agent and client by proposing modification to DHCP server behavior.
The proposed solution is in line with DHCPv6 [RFC3315] where the The proposed solution is in line with DHCPv6 [RFC3315] where the
server always includes the Client Identifier option in the Reply server always includes the Client Identifier option in the Reply
messages. messages.
3. Proposed Modification To [RFC2131] 3. Proposed Modification To [RFC2131]
If the 'client identifier' option is set in a message received from a If the 'client identifier' option is set in a message received from a
client, the server MUST return the 'client identifier' option, client, the server MUST return the 'client identifier' option,
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relevant fields are modified accordingly to overcome the problems relevant fields are modified accordingly to overcome the problems
mentioned in this document. mentioned in this document.
Option DHCPOFFER DHCPACK DHCPNAK Option DHCPOFFER DHCPACK DHCPNAK
------ --------- ------- ------- ------ --------- ------- -------
Client identifier (if MUST MUST MUST Client identifier (if MUST MUST MUST
sent by client) sent by client)
Client identifier (if MUST NOT MUST NOT MUST NOT Client identifier (if MUST NOT MUST NOT MUST NOT
not sent by client) not sent by client)
Client MAY use 'client identifier' or 'chaddr' received from server
along with 'xid' to map the response to request. This will guarantee
that a particular response from the server is meant for the
particular client.
4. IANA Considerations 4. IANA Considerations
This memo asks the IANA for no new parameters. This memo asks the IANA for no new parameters.
5. Security Considerations 5. Security Considerations
No known security considerations. No known security considerations.
6. Acknowledgements 6. Acknowledgements
 End of changes. 7 change blocks. 
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