NetWare/IP DHCP Options: NetWare/IP Domain Name and Information
Two DHCP options that hand NetWare/IP clients their domain name and startup settings.
Droms, R. and K. Fong, "NetWare/IP Domain Name and Information", RFC 2242, DOI 10.17487/RFC2242, November 1997, <https://www.rfc-editor.org/info/rfc2242>.
@misc{rfc2242,
series = {Request for Comments},
number = 2242,
howpublished = {RFC 2242},
publisher = {RFC Editor},
doi = {10.17487/RFC2242},
url = {https://www.rfc-editor.org/info/rfc2242},
author = {R. Droms and K. Fong},
title = {{NetWare/IP Domain Name and Information}},
pagetotal = 6,
year = 1997,
month = nov,
} RFC text
Contents
Network Working Group R. Droms
Request for Comments: 2242 Bucknell University
Category: Standards Track K. Fong
Novell
November 1997
NetWare/IP Domain Name and Information
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1997). All Rights Reserved.
1.0 Abstract
The Dynamic Host Configuration Protocol (DHCP) [RFC 2131] provides a
framework for passing configuration information to hosts on a TCP/IP
network. DHCP includes options for specific configuration parameters
[RFC 2132]. This document defines options that carry NetWare/IP
domain name and NetWare/IP sub-options to DHCP clients.
1.1 Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC 2119].
1.2 Terminology
This document uses the following terms:
o "DHCP client"
A DHCP client is an Internet host using DHCP to obtain
configuration parameters such as a network address.
o "DHCP server"
A DHCP server is an Internet host that returns configuration
parameters to DHCP clients.
2. The NetWare/IP Domain Name option
This option code is used to convey the NetWare/IP domain name used by
the NetWare/IP product. The NetWare/IP Domain in the option is an NVT
ASCII [RFC 854] string whose length is inferred from the option 'len'
field.
The code for this option is 62, and its maximum length is 255.
Code Len NetWare/IP Domain Name
+-----+-----+------+------+------+-----
| 62 | n | c1 | c2 | c3 | ...
+-----+-----+------+------+------+-----
The 'len' field gives the length of the NetWare/IP Domain Name.
3. The NetWare/IP Information option
The NetWare/IP option code will be used to convey all the NetWare/IP
related information except for the NetWare/IP domain name.
The code for this option is 63, and its maximum length is 255. A
number of NetWare/IP sub-options will be conveyed using this option
code. The 'len' field for this option gives the length of the option
data, which includes the sub-option code, length and data fields.
Each sub-option contains in sequential order, a one byte sub-option
code, a one byte length, and an optional multiple byte value field.
The sub-option length gives the length of the value field for the
sub-option. The example below illustrates the use of the 'len' and
sub-option length fields in this option.
One and only one of the following four sub-options must be the first
sub-option to be present in option 63 encoding. Each of them is
simply a type length pair with length set to zero.
Sub-options:
NWIP_DOES_NOT_EXIST (code 1)
The responding DHCP server does not have any NetWare/IP
information configured.
NWIP_EXIST_IN_OPTIONS_AREA (code 2)
All NetWare/IP information is present in the 'options' area of the
DHCP response packet.
NWIP_EXIST_IN_SNAME_FILE (code 3)
All NetWare/IP information is present in the 'sname' and, if
necessary, 'file' fields of the DHCP response packet. If used, the
following DHCP server behavior is required: within the 'options'
area, option 63 is present with its length field set to 2. The
first byte of the value field is set to NWIP_EXIST_IN_SNAME_FILE
tag and the second byte is set to zero. Both option 62 and option
63 will be placed in the area covered by the sname and file
fields. Option 62 is encoded normally. Option 63 is encoded with
its tag, length and value. The value field does not contain any of
the first four sub-options described herein.
NWIP_EXIST_BUT_TOO_BIG (code 4)
Neither 'options' area nor 'sname' field can accommodate the
NetWare/IP information.
If either NWIP_EXIST_IN_OPTIONS_AREA or NWIP_EXIST_IN_SNAME_FILE
sub-options is set, one or more of the following sub-options may be
present.
NSQ_BROADCAST (code 5)
Length is 1 and a value of 1 or 0. If the value is 1, the client
SHOULD perform a NetWare Nearest Server Query to find out its
nearest NetWare/IP server.
PREFERRED_DSS (code 6)
Length is (n * 4) and the value is an array of n IP addresses,
each four bytes in length. The maximum number of addresses is 5
and therefore the maximum length value is 20. The list contains
the addresses of n NetWare Domain SAP/RIP Server (DSS).
NEAREST_NWIP_SERVER (code 7)
Length is (n * 4) and the value is an array of n IP addresses,
each four bytes in length. The maximum number of addresses is 5
and therefore the maximum length value is 20. The list contains
the addresses of n Nearest NetWare/IP servers.
AUTORETRIES (code 8)
Length is 1 and the value is a one byte integer value indicating
the number of times a NetWare/IP client should attempt to
communicate with a given DSS server at startup.
AUTORETRY_SECS (code 9)
Length is 1 and the value is a one byte integer value indicating
the amount of delay in seconds in between each NetWare/IP client
attempt to communicate with a given DSS server at startup.
NWIP_1_1 (code 10)
Length is 1 and the value is 1 or 0. If the value is 1, the
NetWare/IP client SHOULD support NetWare/IP Version 1.1
compatibility. A NetWare/IP client only needs this compatibility
if it will contact a NetWare/IP version 1.1 server.
PRIMARY_DSS (code 11)
Length of 4, and the value is a single IP address. This field
identifies the Primary Domain SAP/RIP Service server (DSS) for
this NetWare/IP domain. NetWare/IP administration utility uses
this value as Primary DSS server when configuring a secondary DSS
server.
An example of option 63 encoding is provided below.
Code Len NetWare/IP General Info
+-----+-----+----+----+
| 63 | 11 | 2 | 0 |
+-----+-----+----+----+
NWIP_EXIST_IN_OPTIONS_AREA (length 0)
+----+----+----+
| 5 | 1 | 1 |
+----+----+----+
NSQ_BROADCAST_SERVER (length 1)
value is YES
+----+----+------------+
| 7 | 4 | IP address |
+----+----+------------+
NEAREST_NWIP_SERVER (length 4)
value is IP address of server
4. References
[RFC 854] Postel, J. and J. Reynolds, "Telnet Protocol
Specification", RFC 854, May 1983.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC 2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, March 1997.
[RFC 2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
5. Security considerations
DHCP currently provides no authentication or security mechanisms.
Potential exposures to attack are discussed in section 7 of the DHCP
protocol specification [RFC 2131].
The NetWare/IP options can be used by unauthorized DHCP servers to
misconfigure NetWare/IP clients with potentially disruptive
information.
6. Authors' addresses
Ralph Droms
Computer Science Department
323 Dana Engineering
Bucknell University
Lewisburg, PA 17837
Phone: (717) 524-1145
EMail: droms@bucknell.edu
Kester Fong
Information Access Division
Novell Inc.
SJF-8-265
2010 Fortune Dr,
San Jose, CA95131
Phone:(408)-577-8959
EMail: kfong@novell.com
7. Full Copyright Statement
Copyright (C) The Internet Society (1997). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
AI ELI5
On this page
§1What the RFC Adds to DHCP
The Dynamic Host Configuration Protocol (DHCP, RFC 2131) passes configuration information to hosts on a TCP/IP network, and RFC 2132 defines options for specific parameters. RFC 2242 defines two more options that carry the NetWare/IP domain name and NetWare/IP sub-options to DHCP clients.
The key words MUST, SHOULD and the like are used as described in RFC 2119.
DHCP is how a computer gets its settings when it joins a network. This RFC adds two new kinds of setting for one particular system.
§2DHCP Clients and Servers
The RFC uses two terms. A DHCP client is an Internet host using DHCP to obtain configuration parameters such as a network address. A DHCP server is an Internet host that returns configuration parameters to DHCP clients.
The options described here travel from the server to the client in the DHCP response.
The client is the computer asking for settings. The server is the one that answers with them.
§3Option 62: The Domain Name
Option code 62 conveys the NetWare/IP domain name used by the NetWare/IP product. The name is an NVT ASCII (RFC 854) string, and its length is inferred from the option's len field. The maximum length is 255.
The layout is a code byte (62), a length byte n, and then the characters c1, c2, c3 and so on.
Option 62 is a label that says which NetWare/IP network name the computer belongs to, written as plain letters.
§4Option 63: Sub-options
Option code 63 carries all other NetWare/IP information. Its maximum length is 255, and its len field covers all the sub-options inside it. Each sub-option has a one-byte code, a one-byte length and an optional value. The sub-option length counts only the value field.
Exactly one of the first four sub-options (codes 1 to 4) must come first. Each is just a code with length zero. They say where the information lives: NWIP_DOES_NOT_EXIST (the server has none configured), NWIP_EXIST_IN_OPTIONS_AREA (it is all in the options area), NWIP_EXIST_IN_SNAME_FILE (it is in the sname and, if needed, file fields) and NWIP_EXIST_BUT_TOO_BIG (neither place can hold it).
With code 3, the server must still put option 63 in the options area with length 2, the first byte set to the code 3 tag and the second byte zero. Options 62 and 63 then go in the sname and file area, where option 63 carries no first-four sub-option.
If code 2 or 3 is used, sub-options 5 to 11 may follow. They set whether to run a Nearest Server Query, which Domain SAP/RIP Servers (DSS) to prefer, nearest servers, retry count and delay, version 1.1 compatibility, and the primary DSS.
Option 63 is a box with smaller labelled slots inside. The first slot says where to find the answers, and the other slots hold things like server addresses and how many times to retry.
- 1NWIP_DOES_NOT_EXIST — Server has no NetWare/IP information configured.
- 2NWIP_EXIST_IN_OPTIONS_AREA — All information is in the options area.
- 3NWIP_EXIST_IN_SNAME_FILE — All information is in the sname and, if needed, file fields.
- 4NWIP_EXIST_BUT_TOO_BIG — Information fits in neither place.
- 5NSQ_BROADCAST — Value 1 or 0; if 1 the client SHOULD do a Nearest Server Query.
- 6PREFERRED_DSS — Up to 5 four-byte addresses of Domain SAP/RIP Servers.
- 7NEAREST_NWIP_SERVER — Up to 5 four-byte addresses of nearest NetWare/IP servers.
- 8AUTORETRIES — Times to try a given DSS at startup.
- 9AUTORETRY_SECS — Seconds of delay between attempts to reach a given DSS.
- 10NWIP_1_1 — Value 1 or 0; if 1 the client SHOULD support version 1.1 compatibility.
- 11PRIMARY_DSS — Single address of the Primary DSS for the domain.
§5An Option 63 Example
The RFC's example is an option 63 of length 11 with three sub-options. First, code 2 (NWIP_EXIST_IN_OPTIONS_AREA) with length 0. Second, code 5 (NSQ_BROADCAST) with length 1 and value 1, meaning yes. Third, code 7 (NEAREST_NWIP_SERVER) with length 4 and one IP address.
The totals match: 2 bytes, then 3 bytes, then 6 bytes, which is 11.
It is a small packing list: where to find things, a yes to looking for a nearby server, and the address of one such server.
§6Security Considerations
DHCP currently provides no authentication or security mechanisms. Possible attacks are discussed in section 7 of RFC 2131.
The NetWare/IP options can be used by unauthorized DHCP servers to misconfigure NetWare/IP clients with potentially disruptive information.
The computer believes whoever answers first. A fake helper could hand it wrong settings and cause trouble.