As per Relevance of the word copyright, we have this rfc below:
Network Working Group G.
Request for Comments: 3004
Category: Standards Track R.
Cisco
Y.
R.
A.
B.
Pacific Broadband
J.
Northstream
November 2000
The User Class Option for
Status of this
This document specifies an Internet standards track protocol for
Internet community, and requests discussion and suggestions
improvements. Please refer to the current edition of the "
Official Protocol Standards" (STD 1) for the standardization
and status of this protocol. Distribution of this memo is unlimited
Copyright
Copyright (C) The Internet Society (2000). All Rights Reserved
This option is used by a Dynamic Host Configuration Protocol (DHCP
client to optionally identify the type or category of user
applications it represents. The information contained in this
is an opaque field that represents the user class of which the
is a member. Based on this class, a DHCP server selects
appropriate address pool to assign an address to the client and
appropriate configuration parameters. This option should
configurable by a user
1.
DHCP administrators may define specific user class identifiers
convey information about a client's software configuration or
its user's preferences. For example, the User Class option can
used to configure all clients of people in the accounting
with a different printer than clients of people in the
department
Stump, et al. Standards Track [Page 1]
RFC 3004 The User Class Option for DHCP November 2000
2. Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in
document are to be interpreted as described in RFC 2119 [3].
3. DHCP
o "DHCP client
A DHCP client or "client" is an Internet host using DHCP to
configuration parameters such as a network address
o "DHCP server
A DHCP server or "server" is an Internet host that
configuration parameters to DHCP clients
o "binding
A binding is a collection of configuration parameters, including
least an IP address, associated with or "bound to" a DHCP client
Bindings are managed by DHCP servers
4. User Class
This option is used by a DHCP client to optionally identify the
or category of user or applications it represents. A DHCP
uses the User Class option to choose the address pool it allocates
address from and/or to select any other configuration option
This option is a DHCP option [1, 2].
This option MAY carry multiple User Classes. Servers may
the meanings of multiple class specifications in an
dependent or configuration dependent manner, and so the use
multiple classes by a DHCP client should be based on the
server implementation and configuration which will be used to
that User class option
The format of this option is as follows
Code Len
+-----+-----+--------------------- . . . --+
| 77 | N | User Class Data ('Len' octets) |
+-----+-----+--------------------- . . . --+
where Value consists of one or more instances of User Class Data
Each instance of User Class Data is formatted as follows
Stump, et al. Standards Track [Page 2]
RFC 3004 The User Class Option for DHCP November 2000
UC_Len_i User_Class_Data_
+--------+------------------------ . . . --+
| L_i | Opaque-Data ('UC_Len_i' octets) |
+--------+------------------------ . . . --+
Each User Class value (User_Class_Data_i) is indicated as an
field. The value in UC_Len_i does not include the length
itself and MUST be non-zero. Let m be the number of User
carried in the option. The length of the option as specified in
must be the sum of the lengths of each of the class names plus m
Len= UC_Len_1 + UC_Len_2 + ... + UC_Len_m + m. If any instances
User Class Data are present, the minimum value of Len is two (Len =
UC_Len_1 + 1 = 1 + 1 = 2).
The Code for this option is 77.
A server that is not equipped to interpret any given user
specified by a client MUST ignore it (although it may be reported).
If a server recognizes one or more user classes specified by
client, but does not recognize one or more other user
specified by the client, the server MAY use the user classes
recognizes
DHCP clients implementing this option SHOULD allow users to enter
or more user class values
5. IANA
Option 77, which IANA has already assigned for this purpose,
be used as the User Class Option for DHCP
6. Security
DHCP currently provides no authentication or security mechanisms
Potential exposures to attack are discussed is section 7 of
protocol specification [1].
This lack of authentication mechanism means that a DHCP server
check if a client or user is authorized to use a given User Class
This introduces an obvious vulnerability when using the User
option. For example, if the User Class is used to give out a
parameter (e.g., a particular database server), there is no way
authenticate a client and it is therefore impossible to check if
client is authorized to use this parameter
Stump, et al. Standards Track [Page 3]
RFC 3004 The User Class Option for DHCP November 2000
7.
[1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
1997.
[2] Alexander, S. and R. Droms, "DHCP Options and BOOTP
Extensions", RFC 2132, March 1997.
[3] Bradner, S., "Key words for use in RFCs to Indicate
Levels", BCP 14, RFC 2119, March 1997.
8.
This document is based on earlier drafts by Glenn Stump, Ralph Droms
Ye Gu, Ramesh Vyaghrapuri and Burcak Beser. Thanks to Ted Lemon
Steve Gonczi, Kim Kinnear, Bernie Volz, Richard Jones, Barr Hibbs
Thomas Narten for their comments and suggestions
9. Authors'
Glenn
IBM Networking
P.O. Box 12195
RTP, NC 27709
Phone: 919 301 4277
EMail: stumpga@us.ibm.
Ralph
Cisco
300 Apollo
Chelmsford, MA 01824
Phone: 978 244 4733
EMail: rdroms@cisco.
Ye
Microsoft
One Microsoft
Redmond, WA 98052
Phone: 425 936 8601
EMail: yegu@microsoft.
Stump, et al. Standards Track [Page 4]
RFC 3004 The User Class Option for DHCP November 2000
Ramesh
Microsoft
One Microsoft
Redmond, WA 98052
Phone: 425 703 9581
EMail: rameshv@microsoft.
Burcak
Pacific Broadband
3103 North 1st
San Jose, CA 95134
Phone: 408 468 6265
Email: Burcak@pacband.
Ann
Microsoft
One Microsoft
Redmond WA 98052
Phone: 425 705 2254
EMail: annd@microsoft.
Jerome
Northstream
Espace Beethoven 1
1200 Route des
BP 302
06906 Sophia Antipolis
Phone: +33 4 97 23 40 45
Fax: +33 4 97 23 24 51
Mobile: +33 6 13 81 76 71
Email: jerome.privat@northstream.
Stump, et al. Standards Track [Page 5]
RFC 3004 The User Class Option for DHCP November 2000
Full Copyright
Copyright (C) The Internet Society (2000). All Rights Reserved
This document and translations of it may be copied and furnished
others, and derivative works that comment on or otherwise explain
or assist in its implementation may be prepared, copied,
and distributed, in whole or in part, without restriction of
kind, provided that the above copyright notice and this paragraph
included on all such copies and derivative works. However,
document itself may not be modified in any way, such as by
the copyright notice or references to the Internet Society or
Internet organizations, except as needed for the purpose
developing Internet standards in which case the procedures
copyrights defined in the Internet Standards process must
followed, or as required to translate it into languages other
English
The limited permissions granted above are perpetual and will not
revoked by the Internet Society or its successors or assigns
This document and the information contained herein is provided on
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE
Funding for the RFC Editor function is currently provided by
Internet Society
Stump, et al. Standards Track [Page 6]
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