don provan
INTERNET DRAFT Novell, Inc.
2 July 1997
Expires 2 January 1998
DHCP Options for Novell Directory Services
draft-provan-dhcp-options-dir-serv-01.txt
Status of this Memo
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Abstract
This document defines three new DHCP options for delivering
configuration information to clients of the Novell Directory
Services. The first option carries a list of NDS servers. The
second option carries the name of the client's NDS tree. The third
carries the initial NDS context. These three options provide an NDS
client with enough information to connect to an NDS tree without
manual configuration of the client.
Changes
The original draft of this document called for transmitting NDS's
Unicode text as 16-bit characters in network byte order. The
current version of the document changes this to have Unicode text
transformed into octets using UTF-8.
1. Introduction
Novell Directory Services is a distributed, replicated,
hierarchical database of objects representing network resources
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such as nodes, services, users, and applications. An NDS client
must be able to locate an NDS server in order to authenticate
itself to the network and gain access to the database. In addition,
the node's user is better served if the NDS client's attention is
focused on the area of the NDS database likely to be of the most
interest to the user.
This specification describes DHCP options [1] that carry NDS
information to TCP/IP clients of NDS. The first option, the NDS
Servers Option, carries a list of NDS servers. The other two
options, the NDS Tree Name Option and the NDS Context Option,
provide the client with a default context within the NDS database.
The NDS Tree Name Option and the NDS Context Option carry 16-bit
Unicode text encoded into an octet stream using UTF-8 [3]. A
complete DHCP implementation can represent of the entire Unicode
character set supported by NDS. At the same time, 7-bit ASCII text
is unchanged by the UTF-8 transformation. In environments where the
NDS tree name and context are restricted to the range of 7-bit
ASCII characters, ASCII-only DHCP clients and servers can support
these options by using the ASCII text as the UTF-8 encoded data.
2. NDS Servers Option
This option specifies one or more NDS servers for the client to
contact for access to the NDS database. Servers SHOULD be listed in
order of preference.
The code for this option is 85. The minimum length of this option
is 4 octets, and the length MUST be a multiple of 4.
Code Len Address 1 Address 2
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+--
| 85 | n | a1 | a2 | a3 | a4 | a1 | a2 | a3 | a4 | ...
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+--
3. NDS Tree Name Option
This option specifies the name of the NDS tree the client will be
contacting. NDS tree names are 16-bit Unicode strings. For
transmission in the NDS Tree Name Option, an NDS tree name is
transformed into octets using UTF-8. The string should NOT be zero
terminated.
The code for this option is 86. The maximum possible length for
this option is 255 bytes.
Code Len NDS Tree Name
+----+----+----+----+----+----+--
| 86 | n | c1 | c2 | c3 | c4 | ...
+----+----+----+----+----+----+--
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4. NDS Context Option
This option specifies the initial NDS context the client should
use. NDS contexts are 16-bit Unicode strings. For transmission in
the NDS Context Option, an NDS context is transformed into octets
using UTF-8. The string should NOT be zero terminated.
A single DHCP option can only contain 255 octets. Since an NDS
context name can be longer than that, this option can appear more
than once in the DHCP packet. The contents of all NDS Context
options in the packet should be concatenated as suggested in the
DHCP specification [2, page 24] to get the complete NDS context. Be
aware that a single UTF-8 encoded character could be split between
two NDS Context Options.
The code for this option is 87. The maximum length for each
instance of this option is 255, but, as just described, the option
may appear more than once if the desired NDS context takes up more
than 255 octets. Implementations are discouraged from enforcing any
specific maximum to the final concatenated NDS context.
Code Len Initial NDS Context
+----+----+----+----+----+----+--
| 87 | n | c1 | c2 | c3 | c4 | ...
+----+----+----+----+----+----+--
References
[1] Alexander, S., and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC-2132, March 1997.
[2] Droms, R., "Dynamic Host Configuration Protocol", RFC-2131,
March 1997.
[3] Yergeau, F., "UTF-8, a transformation format of Unicode and
ISO 10646", RFC-2044, October 1996
Author's Address
Don Provan
Novell, Inc.
2180 Fortune Drive
San Jose, California, 95131
Phone: +1 408 577 8440
EMail: donp@Novell.Com
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