< draft-huang-dhc-multiple-relay-agents-option-00.txt		draft-huang-dhc-multiple-relay-agents-option-01.txt >
	DHC Lu Huang
	Internet Draft Hui Deng
	Intended status: Informational China Mobile
	Expires: April 18, 2010 October 19, 2009
	DHCP option including Multiple Relay Agents' Information		DHC Working Group L. Huang
			Internet-Draft H. Deng
			Intended status: Informational China Mobile
			Expires: September 5, 2010 March 4, 2010
	draft-huang-dhc-multiple-relay-agents-option-00.txt		DHCP option including Multiple Relay Agents' Information
			draft-huang-dhc-multiple-relay-agents-option-01
			Abstract
			RFC 3046 allows only the first Relay Agent to append Relay Agent
			Information option. In some networks, both Layer 2 Relay Agents and
			Layer 3 Relay Agents are deployed and their information is necessary
			for DHCP packets forwarding and DHCP server's policy designing
			described as [I-D.huang-dhc-relay-ps]. This document defines new
			sub-options for Relay Agent Information option (option 82) and
			describes how multiple relay agents add their information into option
			82.
	Status of this Memo		Status of this Memo
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	Copyright Notice		Copyright Notice
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	document authors. All rights reserved.		document authors. All rights reserved.
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	Abstract		include Simplified BSD License text as described in Section 4.e of
			the Trust Legal Provisions and are provided without warranty as
	RFC 3046 allows only the first Relay Agent to append Relay Agent		described in the BSD License.
	Information option. In some networks, both Layer 2 Relay Agents and
	Layer 3 Relay Agents are deployed and their information is necessary
	for DHCP packets forwarding and DHCP server's policy designing
	described as [4]. This document defines a DHCP option which can
	contain multiple relay agents' information and describes how it works.
	Table of Contents		Table of Contents
	1. Introduction......................................... 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. DHCP option including Multiple Relay Agents' Information .... 3		2. DHCP option including Multiple Relay Agents' Information . . . 4
	2.1. Mechanism....................................... 3		2.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 4
	2.2. Format ......................................... 4		2.2. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . 4
	3. Security Considerations................................ 5		3. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
	4. IANA Considerations................................... 5		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
	5. References.......................................... 5		5. Informative References . . . . . . . . . . . . . . . . . . . . 8
	5.1. Normative References.............................. 5		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
	5.2. Informative References............................ 5
	Author's Addresses...................................... 6
	1. Introduction		1. Introduction
	As defined in RFC 3046, Relay Agent Information option is inserted by		As defined in RFC 3046, Relay Agent Information option is inserted by
	the DHCP relay agent (or downstream network element) when forwarding		the DHCP relay agent (or downstream network element) when forwarding
	client-originated DHCP packets to a DHCP server. Servers recognizing		client-originated DHCP packets to a DHCP server. Servers recognizing
	the Relay Agent Information option may use the information to		the Relay Agent Information option may use the information to
	implement IP address or other parameter assignment policies. The DHCP		implement IP address or other parameter assignment policies. The
	Server echoes the option back verbatim to the relay agent in server-		DHCP Server echoes the option back to the relay agent in server-to-
	to-client replies, and the relay agent strips the option before		client replies, and the relay agent strips the option before
	forwarding the reply to the client.		forwarding the reply to the client.
	RFC 3046 allows only one agent add its information with option 82.		RFC 3046 allows only one agent add its information with option 82.
	But in some scenarios as [4], multiply relay agents need to insert		But in some scenarios as [I-D.huang-dhc-relay-ps], multiply relay
	more information into the same DHCP message. This document defines a		agents need to insert more information into the same DHCP message.
	DHCP option which can contain multiple relay agents' information and		This document defines new sub-options for Relay Agent Information
	describes how it works.		option (option 82) and describes how multiple relay agents add their
			information into option 82.
	2. DHCP option including Multiple Relay Agents' Information		2. DHCP option including Multiple Relay Agents' Information
	2.1. Mechanism		2.1. Format
	This option is organized as a single DHCP option that contains one or		+-------+-----+-----+
	more sub-options. Each relay agent can insert a set of sub-options to		|Code(x)| Len |Value|
	convey its Information.		+-------+-----+-----+
			Sub-option x: Agent ID. Describe a unique identifier for the agent
			who insert this set of sub-options.
			+-------+-------+
			|Code(y)| Len(0)|
			+-------+-------+
			Sub-option y: Identify the end of information of one device.
			2.2. Mechanism
	-------		-------
	+-----------+ +-----------+ /// \\\ +------+		+-----------+ +-----------+ /// \\\ +------+
	+------+ |Layer 2 | |Layer 3 | | | |DHCP |		+------+ |Layer 2 | |Layer 3 | | | |DHCP |
	|Client+--+Relay Agent+--+Relay Agent+--+ Network +--+Server|		|Client+--+Relay Agent+--+Relay Agent+--+ Network +--+Server|
	+------+ +-----------+ +-----------+ | | +------+		+------+ +-----------+ +-----------+ | | +------+
	\\\ ///		\\\ ///
	-------		-------
	Figure 1 Network Scenario
	As shown in figure 1, it's a most popular network scenario where		As shown in above figure, it's a most popular network scenario where
	option including Multiple Relay Agents' Information is necessary.		option including Multiple Relay Agents' Information is necessary.
	Based on the demand of the new Relay Agent Information option as [4],		Based on the demand as [I-D.huang-dhc-relay-ps], agents work as
	this option works as following:		following:
	1. An initiating client sends a DHCP discovery packet.
	2. Layer 2 relay agent receives the discovery packet without any
	options defined in this document. So it inserts a new option in
	which a set of sub-options convey the layer 2 relay agent's
	necessary information. After that, the discovery packet is
	forwarded to the appropriate port.
	3. Layer 3 relay agent receives the discovery packet and check out
	that it already contains a relay agent information option defined
	in this document. So it just insert a set of sub-options into the
	existing option to convey its own necessary information. After
	that, the discovery packet is forwarded and reaches DHCP server
	directly or through a network.
	4. DHCP server handles the discovery packet as normal and could carry
	out flexible IP assigning or other policies based on the
	information of option defined in this document. After that DHCP
	server reply a DHCP response packet containing the original option
	carried in the corresponding discovery packet.
	5. Layer 3 relay agents quickly get the right outgoing interface
	based on the information in the option and forward the response
	packet after deleting its set of sub-options.
	6. Layer 2 relay agents quickly get the right outgoing interface
	based on the information in the option and forward the response
	packet. Because there is no other agent's information left in the
	option, so in this case layer 2 relay agent delete the whole
	option before forwarding the packet.
	2.2. Format
	Option format:
	+-------+-----+-----+
	|Code(x)| Len |Value|
	+-------+-----+-----+
	This option use a new DHCP option code "x".
	Value:
	+-----------+-----------+-----------+-----------+
	|sub-option1|sub-option2|sub-option3|sub-option4|
	+-+--+------+-+--+------+-+--+------+-+--+------+
	|1|N1|value1|2|N2|value2|3|N3|value3|4|N4|value4|->a Set of sub-options
	+-+--+------+-+--+------+-+--+------+-+--+------+
	/ ... \
	| Multiple sets of sub-options |
	\ ... /
	+-+--+------+-+--+------+-+--+------+-+--+------+
	|1|N1|value1|2|N2|value2|3|N3|value3|4|N4|value4|
	+-+--+------+-+--+------+-+--+------+-+--+------+
	Sub-option1		(1) An initiating client sends a DHCP discovery packet.
	Agent level. Describe the order of agent who insert this set of		(2) Layer 2 relay agent receives the discovery packet without option
	sub-options. For example, in the case of figure 1, layer 2 relay		82. So it inserts an option 82 as [RFC3046]. After that, the
	agent's level is 1 because it is the closest agent to the client		discovery packet is forwarded to the appropriate port.
	and it will be the first agent who insert relay agent information.
	Sub-option2		(3) Layer 3 relay agent receives the discovery packet and check out
			that it already contains an option 82. Firstly it adds an sub-option
			y defined in section 2.2 into the existing option 82 following sub-
			options added by layer 2 agent. And then it adds its agent ID sub-
			option(x), circuit ID sub-option and end ID sub-option(y) into the
			existing option 82. After that, the discovery packet is forwarded
			and reaches DHCP server directly or through a network.
	Agent ID. Describe a unique identifier for the agent who insert		(4) DHCP server handles the discovery packet and could carry out
	this set of sub-options.		flexible IP assigning or other policies based on the information of
			option 82 described in this document. After that DHCP server reply a
			DHCP response packet containing the original option 82 carried in the
			corresponding discovery packet.
	Sub-option3		(5) Layer 3 relay agents quickly get the right outgoing interface
	IP address. Describe IP address of the agent who insert this set		based on the information in the option 82 and forward the response
	of sub-options. For a pure layer 2 agent, this field could be		packet after deleting sub-options it added before.
	0.0.0.0.
	Sub-option4		(6) Layer 2 relay agents quickly get the right outgoing interface
			based on the information in the option 82 and forward the response
			packet. Layer 2 relay agent deletes the whole option 82 before
			forwarding the packet.
	Downstream interface. Describe the receiving interface of the		If there are more relay agents between Layer 2 and Layer 3 relay
	DHCP packet of the agent who insert this set of sub-options.		agent or between Layer 3 relay agent and DHCP server, the third and
			the following relay agents could only add their agent ID sub-
			option(x), circuit ID sub-option and end ID sub-option(y) into the
			existing option 82 before forwarding the discovery packet upward.
			The processing of replay packet from DHCP server to client is similar
			as above.
	3. Security Considerations		3. Security Considerations
	This document doesn't propose any new protocol.		This document doesn't propose any new protocol.
	4. IANA Considerations		4. IANA Considerations
	This document requires a new number for DHCP option code x described
	in section 2.2.
	5. References
	5.1. Normative References		This document requires new numbers for sub-option code x and y
			described in section 2.1.
	[1] R. Droms, Bucknell University, "Dynamic Host Configuration		5. Informative References
	Protocol", RFC 2131, March 1997.
	[2] S. Alexander, Silicon Graphics, Inc., and R. Droms, "DHCP Options		[I-D.huang-dhc-relay-ps]
	and BOOTP Vendor Extensions", RFC 2132, March 1997.		Huang, L., Deng, H., Kurapati, P., and B. Joshi, "Problem
			Statement for DHCP Relay Agent",
			draft-huang-dhc-relay-ps-00 (work in progress), July 2009.
	[3] M. Patrick, Motorola BCS, "DHCP Relay Agent Information Option",		[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
	RFC 3046, January 2001.		RFC 2131, March 1997.
	5.2. Informative References		[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
			Extensions", RFC 2132, March 1997.
	[4] L. Huang, H. Deng, China Mobile, "Problem Statement for DHCP Relay		[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
	Agent", draft-huang-dhc-relay-ps-00, July 2009.		RFC 3046, January 2001.
	Author's Addresses		Authors' Addresses
	Lu Huang		Lu Huang
	China Mobile		China Mobile
	53A,Xibianmennei Ave.,		Unit2, 28 Xuanwumenxi Ave,Xuanwu District
	Xuanwu District,
	Beijing 100053		Beijing 100053
	China		China
	Email: huanglu@chinamobile.com		Email: huanglu@chinamobile.com
	Hui Deng		Hui Deng
	China Mobile		China Mobile
	53A,Xibianmennei Ave.,		Unit2, 28 Xuanwumenxi Ave,Xuanwu District
	Xuanwu District,		Beijing 100053
	Beijing 100053
	China		China
	Email: denghui02@gmail.com
			Email: denghui@chinamobile.com
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