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Versions: 00 01 02 03 04 RFC 2937

Network Working Group                                         C. Smith
Internet Draft                                  Sun Microsystems, Inc.
                                                             June 1999
                                                 Expires December 1999


                The Name Service Search Option for DHCP
                      <draft-ietf-dhc-nsso-00.txt>


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.  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
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Abstract


Introduction

   The Dynamic Host Configuration Protocol (DHCP)[1] provides a
   framework for passing configuration information to hosts on a TCP/IP
   network. RFC 2132 [2] allows DHCP servers to specify configuration
   information for various kinds of name servers to be passed to DHCP
   clients.  Many clients use multiple name services and have crafted
   their own conventions that allow an individual host to express the
   order among the various name services with which lookups are done.
   However, no search order can be specified via DHCP.  The purpose of
   this document is to allow DHCP servers to specify the search order to
   be used by DHCP clients.




Smith                                                           [Page 1]


RFC DRAFT                                                      June 1999


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 [3].  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 1 byte.  A
   DHCP server SHOULD return, in its preferred order, the integer option
   code for the name  services  (the  earlier  in  the  list,  the  more
   preferred the name service).

           Code     Len       Name Service Search Order in Sequence
           +-------+-------+-------+--------+-
           |  TBD  |   n   |  ns1   | ns2   | ...
           +-------+-------+-------+--------+-

In the above example, ns1 & ns2 are integers corresponding to the name
service servers option (this allows for evolution without the need for a
separate table translating between these integers and the name services
they represent).  For example, the current list, taken from RFC 2132,
includes

    Name Service                                  Value

    Domain Name Server Option                       6
    Network Information Servers Option             41
    NetBIOS over TCP/IP Name Server Option         44
    Network Information Service+ Servers Option    65










Smith                                                           [Page 2]


RFC DRAFT                                                      June 1999


A DHCP server wishing to express that a client should first search  DNS,
then NIS+, would send

        +-------+-------+-------+--------+-
        |  TBD  |   2   |   6   |  65    |
        +-------+-------+-------+--------+-

DHCP Client Behavior

   The DHCP client will use this option to create a search list for name
   resolution.  The client SHOULD ignore any name services appearing in
   this option that it does not support or has not been configured to
   access.  Clients will interpret this option in a system-specific
   manner whose specification is outside the scope of this document.

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].

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] Bradner, S., "Key words for use in RFCs to indicate requirement
   levels", RFC 2119, March 1997.

Author  Information

   Carl Smith
   Sun Microsystems, Inc.
   901 San Antonio Road
   Palo Alto, CA 94043
   email:  cs@Eng.Sun.COM

Expiration

   This document will expire on December 31, 1999.

Full Copyright Statement

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it



Smith                                                           [Page 3]


RFC DRAFT                                                      June 1999


   or assist in its implementation may be prepared, copied, published
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Smith                                                           [Page 4]


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