draft-ietf-dhc-userclass-09.txt		rfc3004.txt
	Internet Engineering Task Force G. Stump		Network Working Group G. Stump
	Dynamic Host Configuration Working Group IBM		Request for Comments: 3004 IBM
	Internet Draft R. Droms		Category: Standards Track R. Droms
	Expires: December 2000 Bucknell University		Cisco Systems
	draft-ietf-dhc-userclass-09.txt Y. Gu		Y. Gu
	R. Vyaghrapuri		R. Vyaghrapuri
	A. Demirtjis		A. Demirtjis
	Microsoft		Microsoft
	B. Beser		B. Beser
	3Com		Pacific Broadband Communications
	J. Privat		J. Privat
	BT		Northstream AB
	July 2000		November 2000
	The User Class Option for DHCP		The User Class Option for DHCP
	<draft-ietf-dhc-userclass-09.txt>
	Status of this Memo		Status of this Memo
	This document is an Internet-Draft and is in full conformance with		This document specifies an Internet standards track protocol for the
	all provisions of Section 10 of RFC2026.		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.
	Internet-Drafts are working documents of the Internet Engineering		Copyright Notice
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	Abstract		Abstract
	This option is used by a DHCP client to optionally identify the type		This option is used by a Dynamic Host Configuration Protocol (DHCP)
	or category of user or applications it represents.		client to optionally identify the type or category of user or
	The information contained in this option is an opaque field that		applications it represents. The information contained in this option
	represents the user class of which the client is a member.		is an opaque field that represents the user class of which the client
	Based on this class, a DHCP server selects the appropriate address		is a member. Based on this class, a DHCP server selects the
	pool to assign an address to the client and the appropriate		appropriate address pool to assign an address to the client and the
	configuration parameters.		appropriate configuration parameters. This option should be
	This option should be configurable by a user.		configurable by a user.
	1. Introduction		1. Introduction
	It is often desirable to provide different levels of service to		DHCP administrators may define specific user class identifiers to
	different users of an IP network.		convey information about a client's software configuration or about
	In order for an IP network to implement this service		its user's preferences. For example, the User Class option can be
	differentiation, it needs a way to classify users. A simple solution		used to configure all clients of people in the accounting department
	to this is to use source IP addresses for classification. Under this		with a different printer than clients of people in the marketing
	scheme, network administrators first configure network devices such		department.
	as routers to recognize traffic from a particular source IP address
	(or address range) and handle it specially to meet the desired level
	of service. Next, they assign the IP addresses to the hosts of the
	intended users so that the user will receive the appropriate level
	of service. They can configure the hosts manually with these
	addresses. However, they cannot use DHCP for address assignment,
	even if they are already running a DHCP server in their network. A
	current RFC-compliant DHCP server assigns IP addresses based on the
	location of the DHCP Client in the network topology, not the type of
	user it supports.
	This document describes a simple extension of the DHCP protocol that
	enables a DHCP server to assign IP addresses from different address
	pools depending on the type of users from which it receives DHCP
	requests. With this new extension, network administrators will be
	able to use DHCP to hand out the appropriate addresses to clients.
	An example intended usage is a corporate network subnet consisting
	of different departments of users, such as Accounting, Legal, Staff,
	etc. It may be desirable to allocate logical address pools to each
	of the departments so that network policies may be implemented
	easily on IP address ranges; and this would facilitate providing
	differential services, such as network reachability.
	A DHCP server can also use the information contained in the User
	Class to allocate other configuration parameters than the IP
	address. For example, a DHCP server receiving a request from a
	client with the User Class set to "accounting auditors" may return
	an option with the address of a particular database server. Indeed a
	DHCP server may have a single pool of addresses and only use the
	user class to select parameters other than IP addresses.
	2. Requirements Terminology		2. Requirements Terminology
	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].		document are to be interpreted as described in RFC 2119 [3].
	3. DHCP Terminology		3. DHCP Terminology
	o "DHCP client"		o "DHCP client"
	A DHCP client or "client" is an Internet host using DHCP to obtain		A DHCP client or "client" is an Internet host using DHCP to obtain
	configuration parameters such as a network address.		configuration parameters such as a network address.
	o "DHCP server"		o "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.
	o "binding"		o "binding"
	A binding is a collection of configuration parameters, including at		A binding is a collection of configuration parameters, including at
	least an IP address, associated with or "bound to" a DHCP client.		least an IP address, associated with or "bound to" a DHCP client.
	Bindings are managed by DHCP servers.		Bindings are managed by DHCP servers.
	4. User Class option		4. User Class option
	This option is used by a DHCP client to optionally identify the type		This option is used by a DHCP client to optionally identify the type
	or category of user or applications it represents.		or category of user or applications it represents. A DHCP server
	A DHCP server uses the User Class option to choose the address pool		uses the User Class option to choose the address pool it allocates an
	it allocates an address from and/or to select any other		address from and/or to select any other configuration option.
	configuration option.
	This option is a DHCP option [1, 2].		This option is a DHCP option [1, 2].
	This option MAY carry multiple User Classes.		This option MAY carry multiple User Classes. Servers may interpret
	Servers may interpret the meanings of multiple class specifications		the meanings of multiple class specifications in an implementation
	in an implementation dependent or configuration dependent manner,		dependent or configuration dependent manner, and so the use of
	and so the use of multiple classes by a DHCP client should be based		multiple classes by a DHCP client should be based on the specific
	on the specific server implementation and configuration which will		server implementation and configuration which will be used to process
	be used to process that User class option.		that User class option.
	The format of this option is as follows:		The format of this option is as follows:
	Code Len Value		Code Len Value
	+-----+-----+--------------------- . . . --+		+-----+-----+--------------------- . . . --+
	| 77 | N | User Class Data ('Len' octets) |		| 77 | N | User Class Data ('Len' octets) |
	+-----+-----+--------------------- . . . --+		+-----+-----+--------------------- . . . --+
	where Value consists of one or more instances of User Class Data.		where Value consists of one or more instances of User Class Data.
	Each instance of User Class Data is formatted as follows:		Each instance of User Class Data is formatted as follows:
	UC_Len_i User_Class_Data_i		UC_Len_i User_Class_Data_i
	+--------+------------------------ . . . --+		+--------+------------------------ . . . --+
	| L_i | Opaque-Data ('UC_Len_i' octets) |		| L_i | Opaque-Data ('UC_Len_i' octets) |
	+--------+------------------------ . . . --+		+--------+------------------------ . . . --+
	Each User Class value (User_Class_Data_i) is indicated as an opaque		Each User Class value (User_Class_Data_i) is indicated as an opaque
	field.		field. The value in UC_Len_i does not include the length field
	The value in UC_Len_i does not include the length field itself and		itself and MUST be non-zero. Let m be the number of User Classes
	MUST be non-zero.		carried in the option. The length of the option as specified in Len
	Let m be the number of User Classes carried in the option. The		must be the sum of the lengths of each of the class names plus m:
	length of the option as specified in Len must be the sum of the		Len= UC_Len_1 + UC_Len_2 + ... + UC_Len_m + m. If any instances of
	lengths of each of the class names plus m:		User Class Data are present, the minimum value of Len is two (Len =
	Len= UC_Len_1 + UC_Len_2 + ... + UC_Len_m + m.		UC_Len_1 + 1 = 1 + 1 = 2).
	If any instances of 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.		The Code for this option is 77.
	A server that is not equipped to interpret any given user class		A server that is not equipped to interpret any given user class
	specified by a client MUST ignore it (although it may be reported).		specified by a client MUST ignore it (although it may be reported).
	If a server recognizes one or more user classes specified by the		If a server recognizes one or more user classes specified by the
	client, but does not recognize one or more other user classes		client, but does not recognize one or more other user classes
	specified by the client, the server MAY use the user classes it		specified by the client, the server MAY use the user classes it
	recognizes.		recognizes.
	DHCP clients implementing this option SHOULD allow users to enter		DHCP clients implementing this option SHOULD allow users to enter one
	one or more user class values.		or more user class values.
	5. IANA Considerations		5. IANA Considerations
	Option 77, which IANA has already assigned for this purpose, should		Option 77, which IANA has already assigned for this purpose, should
	be used as the User Class Option for DHCP.		be used as the User Class Option for DHCP.
	6. Security Considerations		6. Security Considerations
	DHCP currently provides no authentication or security mechanisms.		DHCP currently provides no authentication or security mechanisms.
	Potential exposures to attack are discussed is section 7 of the		Potential exposures to attack are discussed is section 7 of the
	protocol specification [1].		protocol specification [1].
	This lack of authentication mechanism means that a DHCP server
	cannot check if a client or user is authorised to use a given User		This lack of authentication mechanism means that a DHCP server cannot
	Class.		check if a client or user is authorized to use a given User Class.
	This introduces an obvious vulnerability when using the User Class		This introduces an obvious vulnerability when using the User Class
	option. For example, if the User Class is used to give out special		option. For example, if the User Class is used to give out a special
	IP addresses that have better QoS associated with them (as described		parameter (e.g., a particular database server), there is no way to
	in section 1), there is no way to authenticate a client and it is		authenticate a client and it is therefore impossible to check if a
	therefore impossible to check if a client is authorised to use such		client is authorized to use this parameter.
	an IP address.
	7. References		7. References
	[1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,		[1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March
	March 1997.		1997.
	[2] Alexander, S., and Droms R., "DHCP Options and BOOTP Vendor		[2] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
	Extensions", RFC 2132, March 1997.		Extensions", RFC 2132, March 1997.
	[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement		[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
	Levels," RFC 2119, March 1997.		Levels", BCP 14, RFC 2119, March 1997.
	8. Acknowledgments		8. Acknowledgments
	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 and Thomas Narten for their comments and
	suggestions.
	9. Author Information		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 and
			Thomas Narten for their comments and suggestions.
			9. Authors' Addresses
	Glenn Stump		Glenn Stump
	IBM Networking Software		IBM Networking Software
	P.O. Box 12195		P.O. Box 12195
	RTP, NC 27709		RTP, NC 27709
	Phone: (919) 301-4277
	Email: stumpga@us.ibm.com		Phone: 919 301 4277
			EMail: stumpga@us.ibm.com
	Ralph Droms		Ralph Droms
	Computer Science Department		Cisco Systems
	323 Dana Engineering		300 Apollo Drive
	Bucknell University		Chelmsford, MA 01824
	Lewisburg, PA 17837
	Phone: (717) 524-1145		Phone: 978 244 4733
	Email: droms@bucknell.edu		EMail: rdroms@cisco.com
	Ye Gu		Ye Gu
	Microsoft Corporation		Microsoft Corporation
	One Microsoft Way		One Microsoft Way
	Redmond, WA 98052		Redmond, WA 98052
	Phone: 425 936 8601
	Email: yegu@microsoft.com
			Phone: 425 936 8601
			EMail: yegu@microsoft.com
	Ramesh Vyaghrapuri		Ramesh Vyaghrapuri
	Microsoft Corporation		Microsoft Corporation
	One Microsoft Way		One Microsoft Way
	Redmond, WA 98052		Redmond, WA 98052
	Phone: 425 703 9581		Phone: 425 703 9581
	Email: rameshv@microsoft.com		EMail: rameshv@microsoft.com
	Burcak Beser		Burcak Beser
	3Com Corporation		Pacific Broadband Communications
	3800 Golf Road		3103 North 1st Street
	Rolling Meadows, IL		San Jose, CA 95134
	Phone: 847 262 2195
	Email: Burcak_Beser@3com.com		Phone: 408 468 6265
			Email: Burcak@pacband.com
	Ann Demirtjis		Ann Demirtjis
	Microsoft Corporation		Microsoft Corporation
	One Microsoft Way		One Microsoft Way
	Redmond WA 98052		Redmond WA 98052
	Phone: 425-705-2254
	Email: annd@microsoft.com		Phone: 425 705 2254
			EMail: annd@microsoft.com
	Jerome Privat		Jerome Privat
	BT Advanced Communications Technology Centre		Northstream AB
	Adastral Park, Martlesham Heath, IP5 3RE		Espace Beethoven 1
	UK		1200 Route des Lucioles
	Phone: +44 1473 606304		BP 302
	Email: jerome.privat@bt.com		06906 Sophia Antipolis Cedex
			France
			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.se
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