draft-ietf-dhc-slp-05.txt		draft-ietf-dhc-slp-06.txt
	Internet Engineering Task Force C. Perkins		Internet Engineering Task Force C. Perkins
	INTERNET DRAFT E. Guttman		INTERNET DRAFT E. Guttman
	Sun Microsystems		Sun Microsystems
	14 October 1998		16 December 1998
	DHCP Options for Service Location Protocol		DHCP Options for Service Location Protocol
	draft-ietf-dhc-slp-05.txt		draft-ietf-dhc-slp-06.txt
	Status of This Memo		Status of This Memo
	This document is a submission by the Dynamic Host Configuration		This document is a submission by the Dynamic Host Configuration
	Working Group of the Internet Engineering Task Force (IETF).		Working Group of the Internet Engineering Task Force (IETF).
	Comments should be submitted to the dhcp-v4@bucknell.edu mailing		Comments should be submitted to the dhcp-v4@bucknell.edu mailing
	list.		list.
	Distribution of this memo is unlimited.		Distribution of this memo is unlimited.
	skipping to change at page 1, line 47		skipping to change at page 1, line 47
	The Dynamic Host Configuration Protocol provides a framework for		The Dynamic Host Configuration Protocol provides a framework for
	passing configuration information to hosts on a TCP/IP network.		passing configuration information to hosts on a TCP/IP network.
	Entities using the Service Location Protocol need to find out the		Entities using the Service Location Protocol need to find out the
	address of Directory Agents in order to transact messages. Another		address of Directory Agents in order to transact messages. Another
	option provides an assignment of scope for configuration of SLP User		option provides an assignment of scope for configuration of SLP User
	and Service Agents.		and Service Agents.
	1. Introduction		1. Introduction
	The Dynamic Host Configuration Protocol [4] provides a framework		The Dynamic Host Configuration Protocol [2] provides a framework
	for passing configuration information to hosts on a TCP/IP network.		for passing configuration information to hosts on a TCP/IP network.
	Entities using the Service Location Protocol, Version 2 [6] need to		Entities using the Service Location Protocol, Version 2 [3] need to
	obtain the address of Directory Agents and Scope configuration. The		obtain the address of Directory Agents and Scope configuration. The
	Service Location Protocol (SLP) provides a default configuration		Service Location Protocol (SLP) provides a default configuration
	for Scopes and Directory Agents may be discovered using multicast		for Scopes and Directory Agents may be discovered using multicast
	or broadcast. It is useful in a larger deployment to be able		or broadcast. It is useful in a larger deployment to be able
	to configure SLP Agents using DHCP, so as to centralize the		to configure SLP Agents using DHCP, so as to centralize the
	administration and to deploy SLP in networks where multicast routing		administration and to deploy SLP in networks where multicast routing
	is not available.		is not available.
	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 [2].		document are to be interpreted as described in [1].
	2. Introduction		2. Introduction
	The DHCP options described below are used to configure Agents using		The DHCP options described below are used to configure Agents using
	the Service Location Protocol, Version 2 [6].		the Service Location Protocol, Version 2 [3].
	The SLP Directory Agent option is used to configure User Agents and		The SLP Directory Agent option is used to configure User Agents and
	Service Agents with the location of Directory Agents in the network.		Service Agents with the location of Directory Agents in the network.
	The SLP Scope Option takes precedence over both default and static		The SLP Scope Option takes precedence over both default and static
	scope configuration of SLP agents.		scope configuration of SLP agents.
	3. SLP Directory Agent Option		3. SLP Directory Agent Option
	This option specifies the location of one or more SLP Directory		This option specifies the location of one or more SLP Directory
	skipping to change at page 2, line 13		skipping to change at page 2, line 13
	preference, if there is an order of preference.		preference, if there is an order of preference.
	The address of the Directory Agent is given in network byte order.		The address of the Directory Agent is given in network byte order.
	The length of the option MUST always be divisible by 4 and has a		The length of the option MUST always be divisible by 4 and has a
	minimum length of 4.		minimum length of 4.
	The Directory Agents listed in this option MUST be configured with		The Directory Agents listed in this option MUST be configured with
	the a non-empty subset of the scope list that the Agent receiving the		the a non-empty subset of the scope list that the Agent receiving the
	Directory Agent Option is configured with. See the notes below.		Directory Agent Option is configured with. See the notes below.
	The SLPv2 specification [6] defines how to use this option.		The SLPv2 specification [3] defines how to use this option.
	4. SLP Service Scope Option		4. SLP Service Scope Option
	The scope list is a comma delimited list which indicates the scopes		The scope list is a comma delimited list which indicates the scopes
	that a SLP Agent is configured to use.		that a SLP Agent is configured to use.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Code = 79 | Length | <Scope List> String ...		| Code = 79 | Length | MANDATORY | <Scope List>...
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The Length indicates the number of bytes which follow. Since the		The Length indicates the number of bytes which follow. Since the
	Scope-List String is encoded using UTF8 characters, it may be the		Scope-List String is encoded using UTF-8 [4] characters, it may be
	cast that the Length is not the same as the number of characters in		the cast that the Length is not the same as the number of characters
	the Scope-List String.		in the Scope-List String. The Length value must include one for the
			'MANDATORY' byte.
	The minimum length is 0, and the maximum length is 256. This imposes		The 'MANDATORY' byte determines whether SLP Agents override their
	a limit on the size of the Scope-List String which can be delivered		static configuration for scopes with the <Scope List> string
	which does not exist in SLP. DHCP administrators will therefore have		provided by the option. This allows DHCP administrators to
	to be careful to not configure very long scope names or very long		implement a policy of assigning a set of scopes to Agents for service
	lists of scopes for any Agents in their network.		provision. If the MANDATORY byte is zero, static configuration takes
			precedence over the DHCP provided scope list. If the MANDATORY byte
			is nonzero, the <Scope List> provided in this option MUST be used by
			the SLP Agent.
	The Scope List String syntax and usage are defined in the SLPv2		The Scope List String syntax and usage are defined in the SLPv2
	specification [6].		specification [3].
	4.1. Zero Length Scope-List String Configuration		4.1. Zero Length Scope-List String Configuration
	A SLP Service Scope Option which indicates a Length of 0 configures		A SLP Service Scope Option which indicates a Length of 1 (in other
	the SLP Agent to use "User Selectable Scopes".		words, omitting the <Scope List> string entirely) validly configures
			the SLP User Agent to use "User Selectable Scopes."
	The SLP Agent will use the aggregated list of scopes of all known		The SLP Agent will use the aggregated list of scopes of all known
	DAs. If no DAs are known, the UA will use SA discovery to determine		DAs. If no DAs are known, the UA will use SA discovery to determine
	the list of scopes on the network, as defined in [6].		the list of scopes on the network, as defined in [3].
	Note that this configuration is tantamount to removing all		Note that this configuration is tantamount to removing all
	centralized control of the scope configuration of hosts on the		centralized control of the scope configuration of hosts on the
	network. This makes it possible for every User Agent to see every		network. This makes it possible for every User Agent to see every
	service. This may not be desirable as users may not be able to or		service. This may not be desirable as users may not be able to or
	desire to decide which services are appropriate for them.		desire to decide which services are appropriate for them.
	5. Security Considerations		5. Security Considerations
	If a malicious host is able to insert fraudulent information in		If a malicious host is able to insert fraudulent information in
	skipping to change at page 4, line 5		skipping to change at page 4, line 5
	could find that it might rely on fraudulent or otherwise malicious		could find that it might rely on fraudulent or otherwise malicious
	directory agents to advertise its services. DHCPOFFERs could prevent		directory agents to advertise its services. DHCPOFFERs could prevent
	the regular SLP framework from functioning by directing clients to		the regular SLP framework from functioning by directing clients to
	not use multicast, to use nonexistent directory agents and so on.		not use multicast, to use nonexistent directory agents and so on.
	These difficulties are inherited from the much larger and more		These difficulties are inherited from the much larger and more
	serious problem, viz. securing or authenticating any information		serious problem, viz. securing or authenticating any information
	whatsoever from a DHCP server (or client!) is not possible in common		whatsoever from a DHCP server (or client!) is not possible in common
	DHCP deployments.		DHCP deployments.
	References		6. Full Copyright Statement
	[1] T. Berners-Lee, R. Fielding, and L. Masinter. Uniform Resource		Copyright (C) The Internet Society (1997). All Rights Reserved.
	Identifiers (URI): Generic Syntax. RFC 2396, August 1998.
	[2] S. Bradner. Key words for use in RFCs to Indicate Requirement		This document and translations of it may be copied and furnished to
	Levels. RFC 2119, March 1997.		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.
	[3] B. Carpenter and Y. Rekhter. Renumbering needs work. RFC 1900,		The limited permissions granted above are perpetual and will not be
	February 1996.		revoked by the Internet Society or its successors or assigns.
	[4] R. Droms. Dynamic Host Configuration Protocol. RFC 2131, March		This document and the information contained herein is provided on an
	1997.		"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."
	[5] E. Guttman, C. Perkins, and J. Kempf. Service Templates and		References
	service: Schemes. draft-ietf-svrloc-service-scheme-11.txt,
	October 1998. (work in progress).
	[6] E. Guttman, C. Perkins, J. Veizades, and M. Day. Service		[1] S. Bradner. Key words for use in RFCs to Indicate Requirement
	Location Protocol version 2. draft-ietf-svrloc-protocol-v2-09.txT,		Levels. RFC 2119, March 1997.
	October 1998. (work in progress).
	[7] J. Veizades, E. Guttman, C. Perkins, and S. Kaplan. Service		[2] R. Droms. Dynamic Host Configuration Protocol. RFC 2131, March
	Location Protocol. RFC 2165, July 1997.		1997.
	[8] F. Yergeau. UTF-8, a transformation format of unicode and ISO		[3] E. Guttman, C. Perkins, J. Veizades, and M. Day. Service
	10646. RFC 2279, October 1998.		Location Protocol version 2. draft-ietf-svrloc-protocol-v2-11.txt,
			October 1998. (work in progress).
	[9] D. Crocker and P. Overell. Augmented BNF for Syntax		[4] F. Yergeau. UTF-8, a transformation format of unicode and ISO
	Specifications: ABNF. RFC 2234, November 1997.		10646. RFC 2279, October 1998.
	Author's Address		Author's Address
	Questions about this memo can be directed to:		Questions about this memo can be directed to:
	Charles E. Perkins Erik Guttman		Charles E. Perkins Erik Guttman
	Technology Development Group Technology Development Group		Technology Development Group Technology Development Group
	Mail Stop MPK15-214 Mail Stop UFRA02		Mail Stop MPK15-214 Mail Stop UFRA02
	Sun Microsystems, Inc. Sun Microsystems, Inc..		Sun Microsystems, Inc. Sun Microsystems, Inc.
	15 Network Circle Bahnstr. 2		15 Network Circle Bahnstr. 2
	Menlo Park, CA 94025 74915 Waibstadt, Germany		Menlo Park, CA 94025 74915 Waibstadt, Germany
	phone: +1 650-786-6464 phone: +49 7263 911 701		phone: +1 650-786-6464 phone: +49 7263 911 701
	fax: +1 650-786-6445 or: +1 650 786 5992		fax: +1 650-786-6445 or: +1 650 786 5992
	email: Charles.Perkins@Sun.Com Erik.Guttman@Sun.Com		email: Charles.Perkins@Sun.Com Erik.Guttman@Sun.Com
	Web: http://www.svrloc.org/~charliep		Web: http://www.svrloc.org/~charliep
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