draft-ietf-dhc-nsso-02.txt   draft-ietf-dhc-nsso-03.txt 
Network Working Group C. Smith Network Working Group C. Smith
Internet Draft Sun Microsystems, Inc. Internet Draft Sun Microsystems, Inc.
December 1999 February 2000
Expires June 2000 Expires August 2000
The Name Service Search Option for DHCP The Name Service Search Option for DHCP
<draft-ietf-dhc-nsso-02.txt> <draft-ietf-dhc-nsso-03.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. Internet-Drafts are working all provisions of Section 10 of RFC2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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This document defines a new DHCP option which is passed from the DHCP This document defines a new DHCP option which is passed from the DHCP
Server to the DHCP Client to specify the order in which name services Server to the DHCP Client to specify the order in which name services
should be consulted when resolving hostnames and other information. should be consulted when resolving hostnames and other information.
Introduction Introduction
The Dynamic Host Configuration Protocol (DHCP)[1] provides a The Dynamic Host Configuration Protocol (DHCP)[1] provides a
framework for passing configuration information to hosts on a TCP/IP framework for passing configuration information to hosts on a TCP/IP
network. RFC 2132 [2] allows DHCP servers to specify configuration network. RFC 2132 [2] allows DHCP servers to specify configuration
information for various kinds of name servers to be passed to DHCP information for various kinds of name services to be passed to DHCP
clients. Many clients use multiple name services and have crafted clients. Many clients use multiple name services and have crafted
their own conventions that allow an individual host to express the their own conventions that allow an individual host to express the
order among the various name services with which lookups are done. order among the various name services with which lookups are done.
However, no search order can be specified via DHCP. The purpose of 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 this document is to allow DHCP servers to specify the search order to
be used by DHCP clients. be used by DHCP clients. To avoid the need for inventing and
maintaining a separate name space for this option, we rely on the
existence of previously-defined DHCP options that specify the IP
address(es) of servers which provide name services whose order we
wish to express.
Definitions Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [3]. This document are to be interpreted as described in RFC 2119 [3]. This
document also uses the following terms: document also uses the following terms:
"DHCP client" "DHCP client"
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"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.
Name Service Search Option Format Name Service 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.
A DHCP server SHOULD return, in its preferred order, the 16-bit, A DHCP server SHOULD return, in its preferred order, the 16-bit,
network order (big-endian [4]) integer option code for the name network byte order (big-endian [4]) integer option code for the name
services (the earlier in the list, the more preferred the name services (the earlier in the list, the more preferred the name
service). service).
Code Length Name Service Search Order in Sequence Code Length Name Service Search Order in Sequence
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD | Len | ns1 | | TBD | Len | ns1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ns2 | ... | | ns2 | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In the above example, ns1 & ns2 are 16-bit integers corresponding to In the above diagram, ns1 and ns2 are 16-bit integers corresponding
the name service servers option (this allows for evolution without to two DHCP options which specify the IP addresses of two different
the need for a separate table translating between these integers and types of name server. The current list of name services and their
the name services they represent). For example, the current list, DHCP option codes, taken from RFC 2132, includes
taken from RFC 2132, includes
Name Service Value Name Service Value
Domain Name Server Option 6 Domain Name Server Option 6
Network Information Servers Option 41 Network Information Servers Option 41
NetBIOS over TCP/IP Name Server Option 44 NetBIOS over TCP/IP Name Server Option 44
Network Information Service+ Servers Option 65 Network Information Service+ Servers Option 65
A DHCP server wishing to express that a client should first search A DHCP server wishing to express that a client should first search
DNS, then NIS+, would send DNS, then NIS+, would send
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD | 4 | 6 | | TBD | 4 | 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 65 | | 65 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD | 4 | 6 | | TBD | 4 | 6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 65 | | 65 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
A name service option code of 0 is used to indicate that the client A name service option code of 0 is used to indicate that the client
should refer to local configuration information. should refer to local naming information (e.g. an /etc/hosts file on
a UNIX machine).
DHCP Client Behavior DHCP Client Behavior
The DHCP client will use this option to create a search list for name The DHCP client will use this option to create a search list for name
resolution. The client SHOULD ignore any name services appearing in resolution. The client SHOULD ignore any name services appearing in
this option that it does not support or has not been configured to this option that it does not support or has not been configured to
access. Clients will interpret this option in a system-specific access. Clients will interpret this option in a system-specific
manner whose specification is outside the scope of this document. manner whose specification is outside the scope of this document.
Security Considerations Security Considerations
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Author Information Author Information
Carl Smith Carl Smith
Sun Microsystems, Inc. Sun Microsystems, Inc.
901 San Antonio Road 901 San Antonio Road
Palo Alto, CA 94043 Palo Alto, CA 94043
email: cs@Eng.Sun.COM email: cs@Eng.Sun.COM
Expiration Expiration
This document will expire on June 30, 2000. This document will expire on August 31, 2000.
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved. Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
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