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Network Working Group R. Droms
INTERNET DRAFT Bucknell University
Obsoletes: draft-ietf-dhc-options-opt127-01.txt April 1996
Expires October 1996
An Extension to the DHCP Option Codes
<draft-ietf-dhc-options-opt127-02.txt>
Status of this memo
This document is an Internet-Draft. 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
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as ``work in progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
ftp.isi.edu (US West Coast).
Abstract
The Dynamic Host Configuration Protocol (DHCP) provides a framework
for passing configuration information to hosts on a TCP/IP network.
This document defines a new option to extend the available option
codes.
Introduction
The Dynamic Host Configuration Protocol (DHCP) [1] provides a
framework for passing configuration information to hosts on a TCP/IP
network. Configuration parameters and other control information are
carried in tagged data items that are stored in the 'options' field
of the DHCP message. The data items themselves are also called
"options."
Each option is assigned a one-octet option code. Options 128-254 are
reserved for local use and at this time over half of the available
options in the range 0-127 and option 255 have been assigned. This
document defines a new option to extend the available option codes
and new option to request the parameters represented by those new
Droms [Page 1]
DRAFT An extension to the DHCP Option Codes April 1996
option codes.
Definition of option 127
Option code 127 indicates that the DHCP option has a two-octet
extended option code. The format of these options is:
Extended
Code Len option code Data...
+-----+-----+-----+-----+-----+-----+----
| 127 | XXX | oh | ol | d1 | d2 | ...
+-----+-----+-----+-----+-----+-----+----
Other than the two-octet extended option code, these options are
encoded and carried in DHCP messages identically to the options
defined in RFC 1533 [2]. The high-order and low-order octets of the
extended option code are stored in 'oh' and 'ol', respectively. The
number of octets given in the 'len' field includes the two-octet
extended option code.
The two-octet extended option codes will be assigned through the
mechanisms defined for the assignment of new options [3] after the
current one-octet option codes have been exhausted.
Definition of option 126
This option is used by a DHCP client to request values for specified
configuration paramaters that are identified by extended option codes
as defined above. The list of n requested parameters is specified as
2n octets, where each pair of octets is a valid extended option code.
The client MAY list the options in order of preference. The DHCP
server is not required to return the options in the requested order,
but MUST try to insert the requested options in the order requested
by the client.
The code for this option is 126. Its minimum length is 2.
Extended
Code Len option codes
+-----+-----+-----+-----+-----+-----+----
| 126 | XXX | c1h | c1l | c2h | c2l | ...
+-----+-----+-----+-----+-----+-----+----
Droms [Page 2]
DRAFT An extension to the DHCP Option Codes April 1996
References
[1] Droms, R., "Dynamic Host Configuration Protocol", RFC 1531,
Bucknell University, October 1993.
[2] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 1533, Lachman Associates, October 1993.
[3] Droms, R., "Procedure for Defining New DHCP Options", Work in
progress, February, 1996.
Security Considerations
Security issues are not discussed in this document.
Author's Address
Ralph Droms
Computer Science Department
323 Dana Engineering
Bucknell University
Lewisburg, PA 17837
Phone: (717) 524-1145
EMail: droms@bucknell.edu
Droms [Page 3]
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