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Network Working Group                                           P. Gupta
Internet Draft                                           IBM Corporation
Obsoletes: draft-ietf-dhc-domsrch-01.txt                   November 1998
                                                        Expires May 1999


                   The Domain Search Option for DHCP
                    <draft-ietf-dhc-domsrch-02.txt>

Status of this Memo

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
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Abstract

   This document defines a new DHCP option which is passed form the DHCP
   Server to the DHCP Client to configure the domain search list which
   is used by the clients to resolve hostnames in the Domain Name
   System[3].

Introduction

   The Dynamic Host Configuration Protocol (DHCP)[1] provides a
   framework for passing configuration information to hosts on a TCP/IP
   network. RFC 2132 allows the Domain Name (option 15) and the Domain
   Name Server (option 6) to be passed to the DHCP client. This
   information is used to resolve names in the Domain Name System. These
   options are usually placed in the resolv.conf file on most operating
   systems. The name resolution routines on the client are also capable
   of using a domain search list that allows name resolution to be
   attempted in a number of domains in sequence. The Domain Search
   Option allows a list of domain names, in order of preference, to be
   passed to the DHCP client such that the search directive can be
   specified for name resolution.



Gupta                                                           [Page 1]


Internet Draft                                               August 1998


Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [4].

   This document also uses the following terms:

      "DHCP client"

           DHCP client or "client" is an Internet host using DHCP to
           obtain configuration parameters such as a network address.

      "DHCP server"

           A DHCP server or "server" is an Internet host that returns
           configuration parameters to DHCP clients.

Domain Search Option Format

   The code for this option is TBD, and its minimum length is 2 bytes.
   This option can contain multiple domain names separated by the ASCII
   space character.

             Code     Len       Domain Names in Sequence
           +-------+-------+-------+--------+---------+-
           |  TBD  |   n   |  d1   | 0x20   |   d2    |
           +-------+-------+-------+--------+---------+-

   In the above example, d1 & d2 are domain names specified as NVT ASCII
   strings. An ASCII space character (0x20) is used as a separator
   between the domain names.

DHCP Client Behavior

   The DHCP client will use this option to create a domain search list
   for name resolution. If a DHCP client is given both a Domain Name
   Option and a Domain Search Option, the Domain Search Option  will
   take precedence.

Security Considerations

   DHCP currently provides no authentication or security mechanisms.
   Potential exposures to attack are discussed in section 7 of the DHCP
   protocol specification [1]. The Domain Search Option can be used to
   misdirect domain name resolution on a client and thus misdirect
   network traffic based on DNS names.




Gupta                                                           [Page 2]


Internet Draft                                               August 1998


References

   [1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March
        1997.
   [2] Alexander, S. and Droms, R., "DHCP Options and BOOTP Vendor
        Extensions", RFC 2132, March 1997.
   [3] Mockapetris, P. V., "Domain names - implementation and
        specification", RFC 1035, November 1987.
   [4] Bradner, S., "Key words for use in RFCs to indicate requirement
        levels", RFC 2119, March 1997.

Author Information

Pratik Gupta
IBM Corporation
4205 S.Miami Blvd
Research Triangle Park, NC 27709
Phone: (919)254-5654
email: pratikg@us.ibm.com

Expiration

   This document will expire on May 31, 1999.


Full Copyright Statement

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   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING



Gupta                                                           [Page 3]


Internet Draft                                               August 1998


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Gupta                                                           [Page 4]


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