Network Working Group P. Gupta
Internet Draft IBM Corporation
Obsoletes: draft-ietf-dhc-domsrch-00.txt November 1998
Expires May 1999
The Domain Search Option for DHCP
<draft-ietf-dhc-domsrch-01.txt>
Status of this Memo
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Abstract
The Dynamic Host Configuration Protocol (DHCP)[1] provides a
framework for passing configuration information to hosts on a TCP/IP
network. This document defines a new 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
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.
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Definitions
Throughout this document, the words that are used to define the
significance of the particular requirements are capitalized. These
words are:
"MUST"
This word or the adjective "REQUIRED" means that the item is
an absolute requirement of this specification.
"MUST NOT"
This phrase means the item is an absolute prohibition of this
specification.
"SHOULD"
This word or the adjective "RECOMMENDED" means that there may
exist valid reasons in particular circumstances to ignore
this item, but the full implications should be understood and
the case carefully weighed before choosing a different
course.
"SHOULD NOT"
This phrase means that there may exist valid reasons in
particular circumstances when the listed behavior is
acceptable or even useful, but the full implications should
be understood and the case carefully weighted before
implementing any behavior described with this label.
"MAY"
This word or the adjective "OPTIONAL" means that this item is
truly optional. One vendor may choose to include the item
because a particular marketplace requires it or because it
enhances the product, for example, another vendor may omit
the same item.
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"
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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.
Code Len Domain Names in Sequence
+-------+-------+-------+--------+---------+-
| TBD | n | d1 | 0x20 | d2 |
+-------+-------+-------+--------+---------+-
Where 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].
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.
Author Information
Pratik Gupta
IBM Corporation
4205 S.Miami Blvd
Research Triangle Park, NC 27709
Phone: (919)254-5654
email: pratikg@us.ibm.com
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Expiration
This document will expire on May 31, 1999.
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