draft-ietf-dhc-domsrch-01.txt   draft-ietf-dhc-domsrch-02.txt 
Network Working Group P. Gupta Network Working Group P. Gupta
Internet Draft IBM Corporation Internet Draft IBM Corporation
Obsoletes: draft-ietf-dhc-domsrch-00.txt November 1998 Obsoletes: draft-ietf-dhc-domsrch-01.txt November 1998
Expires May 1999 Expires May 1999
The Domain Search Option for DHCP The Domain Search Option for DHCP
<draft-ietf-dhc-domsrch-01.txt> <draft-ietf-dhc-domsrch-02.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
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Abstract Abstract
The Dynamic Host Configuration Protocol (DHCP)[1] provides a This document defines a new DHCP option which is passed form the DHCP
framework for passing configuration information to hosts on a TCP/IP Server to the DHCP Client to configure the domain search list which
network. This document defines a new option which is passed form the is used by the clients to resolve hostnames in the Domain Name
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]. System[3].
Introduction Introduction
RFC 2132 allows the Domain Name (option 15) and the Domain Name The Dynamic Host Configuration Protocol (DHCP)[1] provides a
Server (option 6) to be passed to the DHCP client. This information framework for passing configuration information to hosts on a TCP/IP
is used to resolve names in the Domain Name System. These options are network. RFC 2132 allows the Domain Name (option 15) and the Domain
usually placed in the resolv.conf file on most operating systems. The Name Server (option 6) to be passed to the DHCP client. This
name resolution routines on the client are also capable of using a information is used to resolve names in the Domain Name System. These
domain search list that allows name resolution to be attempted in a options are usually placed in the resolv.conf file on most operating
number of domains in sequence. The Domain Search Option allows a list systems. The name resolution routines on the client are also capable
of domain names, in order of preference, to be passed to the DHCP of using a domain search list that allows name resolution to be
client such that the search directive can be specified for name attempted in a number of domains in sequence. The Domain Search
resolution. 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.
Definitions Definitions
Throughout this document, the words that are used to define the The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
significance of the particular requirements are capitalized. These "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
words are: document are to be interpreted as described in RFC 2119 [4].
"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: This document also uses the following terms:
"DHCP client" "DHCP client"
DHCP client or "client" is an Internet host using DHCP to DHCP client or "client" is an Internet host using DHCP to
obtain configuration parameters such as a network address. obtain configuration parameters such as a network address.
"DHCP server" "DHCP server"
A DHCP server or "server" is an Internet host that returns A DHCP server or "server" is an Internet host that returns
configuration parameters to DHCP clients. configuration parameters to DHCP clients.
Domain Search Option Format Domain Search Option Format
The code for this option is TBD, and its minimum length is 2 bytes. 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 Code Len Domain Names in Sequence
+-------+-------+-------+--------+---------+- +-------+-------+-------+--------+---------+-
| TBD | n | d1 | 0x20 | d2 | | TBD | n | d1 | 0x20 | d2 |
+-------+-------+-------+--------+---------+- +-------+-------+-------+--------+---------+-
Where d1 & d2 are domain names specified as NVT ASCII strings. An In the above example, d1 & d2 are domain names specified as NVT ASCII
ASCII space character (0x20) is used as a separator between the strings. An ASCII space character (0x20) is used as a separator
domain names. between the domain names.
DHCP Client Behavior DHCP Client Behavior
The DHCP client will use this option to create a domain search list 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 for name resolution. If a DHCP client is given both a Domain Name
Option and a Domain Search Option, the Domain Search Option will Option and a Domain Search Option, the Domain Search Option will
take precedence. take precedence.
Security Considerations Security Considerations
DHCP currently provides no authentication or security mechanisms. DHCP currently provides no authentication or security mechanisms.
Potential exposures to attack are discussed in section 7 of the DHCP Potential exposures to attack are discussed in section 7 of the DHCP
protocol specification [1]. 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.
References References
[1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March [1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March
1997. 1997.
[2] Alexander, S. and Droms, R., "DHCP Options and BOOTP Vendor [2] Alexander, S. and Droms, R., "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997. Extensions", RFC 2132, March 1997.
[3] Mockapetris, P. V., "Domain names - implementation and [3] Mockapetris, P. V., "Domain names - implementation and
specification", RFC 1035, November 1987. specification", RFC 1035, November 1987.
[4] Bradner, S., "Key words for use in RFCs to indicate requirement
levels", RFC 2119, March 1997.
Author Information Author Information
Pratik Gupta Pratik Gupta
IBM Corporation IBM Corporation
4205 S.Miami Blvd 4205 S.Miami Blvd
Research Triangle Park, NC 27709 Research Triangle Park, NC 27709
Phone: (919)254-5654 Phone: (919)254-5654
email: pratikg@us.ibm.com email: pratikg@us.ibm.com
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