< draft-ietf-dhc-l2ra-05.txt		draft-ietf-dhc-l2ra-06.txt >
	DHC Working Group B. Joshi		DHC B. Joshi
	Internet-Draft Infosys Technologies Ltd.		Internet-Draft Infosys Ltd.
	Intended status: Informational P. Kurapati		Intended status: Informational P. Kurapati
	Expires: October 9, 2011 Juniper Networks		Expires: July 28, 2012 Juniper Networks
	April 7, 2011		January 25, 2012
	Layer 2 Relay Agent Information		Layer 2 Relay Agent Information
	draft-ietf-dhc-l2ra-05.txt		draft-ietf-dhc-l2ra-06.txt
	Abstract		Abstract
	In some networks, DHCP servers rely on Relay Agent Information option		In some networks, DHCP servers rely on Relay Agent Information option
	appended by Relay Agents for IP address and other parameter		appended by Relay Agents for IP address and other parameter
	assignment policies. This works fine when end hosts are directly		assignment policies. This works fine when end hosts are directly
	connected to Relay Agents. In some network configurations, one or		connected to Relay Agents. In some network configurations, one or
	more Layer 2 devices may reside between DHCP clients and Relay agent.		more Layer 2 devices may reside between DHCP clients and Relay agent.
	In these network scenarios, it is difficult to use the Relay Agent		In these network scenarios, it is difficult to use the Relay Agent
	Information option for IP address and other parameter assignment		Information option for IP address and other parameter assignment
	skipping to change at page 1, line 44 ¶		skipping to change at page 1, line 44 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
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	This Internet-Draft will expire on October 9, 2011.		This Internet-Draft will expire on July 28, 2012.
	Copyright Notice		Copyright Notice
	Copyright (c) 2011 IETF Trust and the persons identified as the		Copyright (c) 2012 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Need of Layer 2 Relay Agent . . . . . . . . . . . . . . . . . 5		3. Need of Layer 2 Relay Agent . . . . . . . . . . . . . . . . . 4
	4. Layer 2 Relay Agent in various network scenarios . . . . . . . 6		4. Layer 2 Relay Agent in various network scenarios . . . . . . . 5
	4.1. DHCP server and client on same subnet . . . . . . . . . . 6		4.1. DHCP server and client on same subnet . . . . . . . . . . 5
	4.1.1. Client-server interaction . . . . . . . . . . . . . . 6		4.1.1. Client-server interaction . . . . . . . . . . . . . . 5
	4.1.2. Issues due to introduction of Layer 2 Relay Agent . . 8		4.1.2. Issues due to introduction of Layer 2 Relay Agent . . 7
	4.2. Multiple DHCP server and Client on same subnet . . . . . . 8		4.2. Multiple DHCP server and Client on same subnet . . . . . . 7
	4.2.1. Client-server interaction . . . . . . . . . . . . . . 9		4.2.1. Client-server interaction . . . . . . . . . . . . . . 8
	4.2.2. Issues due to introduction of Layer 2 Relay Agent . . 9		4.2.2. Issues due to introduction of Layer 2 Relay Agent . . 8
	4.3. DHCP server on another subnet with one Layer 3 Relay		4.3. DHCP server on another subnet with one Layer 3 Relay
	Agent . . . . . . . . . . . . . . . . . . . . . . . . . . 10		Agent . . . . . . . . . . . . . . . . . . . . . . . . . . 9
	4.3.1. Client-server interaction . . . . . . . . . . . . . . 10		4.3.1. Client-server interaction . . . . . . . . . . . . . . 9
	4.3.2. Issues due to introduction of Layer 2 Relay Agent . . 12		4.3.2. Issues due to introduction of Layer 2 Relay Agent . . 11
	5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13		5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 14		6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16		8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
	8.1. Normative Reference . . . . . . . . . . . . . . . . . . . 16		8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
	8.2. Informative Reference . . . . . . . . . . . . . . . . . . 16		8.2. Informative Reference . . . . . . . . . . . . . . . . . . 12
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
	1. Introduction		1. Introduction
	DHCP Relay Agents eliminate the necessity of having a DHCP server on		DHCP Relay Agents eliminate the necessity of having a DHCP server on
	each physical network. Relay Agents populate the 'giaddr' field and		each physical network. Relay Agents populate the 'giaddr' field and
	also append the 'Relay Agent Information' option to the DHCP		also append the 'Relay Agent Information' option to the DHCP
	messages. DHCP servers use this option for IP address and other		messages. DHCP servers use this option for IP address and other
	parameter assignment policies. These DHCP Relay Agents are typically		parameter assignment policies. These DHCP Relay Agents are typically
	an IP routing aware device and are referred as Layer 3 Relay Agents.		an IP routing aware device and are referred as Layer 3 Relay Agents.
	skipping to change at page 4, line 22 ¶		skipping to change at page 3, line 46 ¶
	o "DHCP client"		o "DHCP client"
	A DHCP client is an Internet host using DHCP to obtain configuration		A DHCP client is an Internet host using DHCP to obtain configuration
	parameters such as a network address.		parameters such as a network address.
	o "Layer 3 Relay Agent"		o "Layer 3 Relay Agent"
	A Layer 3 Relay Agent is a third-party agent that transfers Bootstrap		A Layer 3 Relay Agent is a third-party agent that transfers Bootstrap
	Protocol (BOOTP) and DHCP messages between clients and servers		Protocol (BOOTP) and DHCP messages between clients and servers
	residing on different subnets, per [RFC951] and [RFC1542].		residing on different subnets, per [RFC0951] and [RFC1542].
	o "BRAS"		o "BRAS"
	BRAS or Broadband Remote Access Server is a network element which		BRAS or Broadband Remote Access Server is a network element which
	acts as an aggregation device terminating end user sessions. BRAS is		acts as an aggregation device terminating end user sessions. BRAS is
	usually the first IP edge device in a Layer 2 Access Network		usually the first IP edge device in a Layer 2 Access Network
	architecture.		architecture.
	o "DHCP server"		o "DHCP server"
	skipping to change at page 6, line 20 ¶		skipping to change at page 5, line 20 ¶
	4.1. DHCP server and client on same subnet		4.1. DHCP server and client on same subnet
	In certain network configurations, a DHCP server may reside on the		In certain network configurations, a DHCP server may reside on the
	same subnet as the DHCP clients. A Layer 2 aggregation device		same subnet as the DHCP clients. A Layer 2 aggregation device
	resides between the DHCP clients and DHCP server. The following		resides between the DHCP clients and DHCP server. The following
	points describe how this Layer 2 device handles various DHCP messages		points describe how this Layer 2 device handles various DHCP messages
	if it acts as a Layer 2 Relay Agent. Figure 1 shows a typical		if it acts as a Layer 2 Relay Agent. Figure 1 shows a typical
	network setup.		network setup.
	+--------+		+--------+
	| End | +--------+ |		| End | +--------+ |
	| Host#1 +-----------| | | +-----------+		| Host#1 +-----------| | | +-----------+
	+--------+ | Layer +-----| | |		+--------+ | Layer +-----| | |
	| 2 | +-----| DHCP |		| 2 | +-----| DHCP |
	+--------+ | device | | | Server#1 |		+--------+ | device | | | Server#1 |
	| End +-----------| #1 | | +-----------+		| End +-----------| #1 | | +-----------+
	| Host#2 | +--------+ |		| Host#2 | +--------+ |
	+--------+ |		+--------+ |
	|		|
	+--------+ |		+--------+ |
	| End | +--------+ |		| End | +--------+ |
	| Host#3 +-----------| | |		| Host#3 +-----------| | |
	+--------+ | Layer +-----|		+--------+ | Layer +-----|
	| 2 | |		| 2 | |
	+--------+ | device | |		+--------+ | device | |
	| End +-----------| #2 |		| End +-----------| #2 |
	| Host#n | +--------+		| Host#n | +--------+
	+--------+		+--------+
	Figure 1		Figure 1
	4.1.1. Client-server interaction		4.1.1. Client-server interaction
	The following summary of protocol message exchanges between clients		The following summary of protocol message exchanges between clients
	and DHCP servers describes how they are handled in a Layer 2 Relay		and DHCP servers describes how they are handled in a Layer 2 Relay
	Agent.		Agent.
	1. The client (End Host #1) broadcasts a DHCPDISCOVER message on its		1. The client (End Host #1) broadcasts a DHCPDISCOVER message on its
	skipping to change at page 9, line 5 ¶		skipping to change at page 8, line 5 ¶
	3. A DHCP server should be able to handle a unicast DHCP message		3. A DHCP server should be able to handle a unicast DHCP message
	containing a Relay Agent Information option. Some existing DHCP		containing a Relay Agent Information option. Some existing DHCP
	server implementations do not echo back the Relay Agent		server implementations do not echo back the Relay Agent
	Information option in responses to unicast messages.		Information option in responses to unicast messages.
	4.2. Multiple DHCP server and Client on same subnet		4.2. Multiple DHCP server and Client on same subnet
	In certain network scenarios, there could be multiple DHCP servers on		In certain network scenarios, there could be multiple DHCP servers on
	the same subnet. Figure 2 shows a typical network setup.		the same subnet. Figure 2 shows a typical network setup.
	+--------+		+--------+
	| End | +--------+ |		| End | +--------+ |
	| Host#1 +-----------| | | +-----------+		| Host#1 +-----------| | | +-----------+
	+--------+ | Layer +-----| | |		+--------+ | Layer +-----| | |
	| 2 | +-----| DHCP |		| 2 | +-----| DHCP |
	+--------+ | device | | | Server#1 |		+--------+ | device | | | Server#1 |
	| End +-----------| #1 | | +-----------+		| End +-----------| #1 | | +-----------+
	| Host#2 | +--------+ |		| Host#2 | +--------+ |
	+--------+ |		+--------+ |
	| +-----------+		| +-----------+
	+--------+ | | DHCP |		+--------+ | | DHCP |
	| End | +--------+ |-----| Server #2 |		| End | +--------+ |-----| Server #2 |
	| Host#3 +-----------| | | | |		| Host#3 +-----------| | | | |
	+--------+ | Layer +-----| +-----------+		+--------+ | Layer +-----| +-----------+
	| 2 | |		| 2 | |
	+--------+ | device |		+--------+ | device |
	| End +-----------| #2 |		| End +-----------| #2 |
	| Host#n | +--------+		| Host#n | +--------+
	+--------+		+--------+
	Figure 2		Figure 2
	4.2.1. Client-server interaction		4.2.1. Client-server interaction
	The message exchanges are the same as explained in 4.1.1. However,		The message exchanges are the same as explained in 4.1.1. However,
	due to the introduction of multiple DHCP servers the below additional		due to the introduction of multiple DHCP servers the below additional
	message exchange may happen.		message exchange may happen.
	1. When Host #1 sends DHCPDISCOVER, it will be received by both DHCP		1. When Host #1 sends DHCPDISCOVER, it will be received by both DHCP
	skipping to change at page 10, line 19 ¶		skipping to change at page 9, line 19 ¶
	2. Other issues are the same as described in section 4.1.2.		2. Other issues are the same as described in section 4.1.2.
	4.3. DHCP server on another subnet with one Layer 3 Relay Agent		4.3. DHCP server on another subnet with one Layer 3 Relay Agent
	In certain network scenarios, there could be a Layer 3 Relay Agent		In certain network scenarios, there could be a Layer 3 Relay Agent
	which relays the DHCP messages from one subnet to a DHCP server on		which relays the DHCP messages from one subnet to a DHCP server on
	another subnet and vice versa. In typical deployments, the Access		another subnet and vice versa. In typical deployments, the Access
	Concentrator acts as Layer 2 Relay Agent and the IP edge device (BRAS		Concentrator acts as Layer 2 Relay Agent and the IP edge device (BRAS
	or IP Services Switch) acts as Layer 3 Relay Agent.		or IP Services Switch) acts as Layer 3 Relay Agent.
	+--------+		+--------+
	| End | +--------+ | |		| End | +--------+ | |
	| Host#1 +--------| | | +-----------+ |		| Host#1 +--------| | | +-----------+ |
	+--------+ | Layer +-----| | | |		+--------+ | Layer +-----| | | |
	| 2 | +--| Layer 3 |----|		| 2 | +--| Layer 3 |----|
	+--------+ | device | | | Relay | |		+--------+ | device | | | Relay | |
	| End +--------| #1 | | | Agent #1 | |		| End +--------| #1 | | | Agent #1 | |
	| Host#2 | +--------+ | +-----------+ | +---------+		| Host#2 | +--------+ | +-----------+ | +---------+
	+--------+ | | | |		+--------+ | | | |
	| +--| DHCP |		| +--| DHCP |
	+--------+ | | | Server |		+--------+ | | | Server |
	| End | +--------+ | | | #1 |		| End | +--------+ | | | #1 |
	| Host#3 +--------| | | +---------+		| Host#3 +--------| | | +---------+
	+--------+ | Layer +-----|		+--------+ | Layer +-----|
	| 2 | |		| 2 | |
	+--------+ | device | |		+--------+ | device | |
	| End +--------| #2 +		| End +--------| #2 +
	| Host#n | +--------+		| Host#n | +--------+
	+--------+		+--------+
	Figure 3		Figure 3
	4.3.1. Client-server interaction		4.3.1. Client-server interaction
	As far as DHCP message processing is concerned, the presence of Layer		As far as DHCP message processing is concerned, the presence of Layer
	3 Relay Agents is transparent to Layer 2 Relay Agents. So all the		3 Relay Agents is transparent to Layer 2 Relay Agents. So all the
	messages are handled in the same way as defined in section 4.1.1 for		messages are handled in the same way as defined in section 4.1.1 for
	the Layer 2 Relay Agent.		the Layer 2 Relay Agent.
	skipping to change at page 16, line 7 ¶		skipping to change at page 12, line 25 ¶
	new security issues. Security issues pertaining to Relay Agents		new security issues. Security issues pertaining to Relay Agents
	in general apply to Layer 2 Relay Agents as well.		in general apply to Layer 2 Relay Agents as well.
	7. IANA Considerations		7. IANA Considerations
	This document does not introduce any new namespaces for the IANA to		This document does not introduce any new namespaces for the IANA to
	manage and does not request any new code point assignments.		manage and does not request any new code point assignments.
	8. References		8. References
	8.1. Normative Reference		8.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",		[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
	RFC 2131, March 1997.		RFC 2131, March 1997.
	[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",		[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
	RFC 3046, January 2001.		RFC 3046, January 2001.
	[RFC3118] Droms, R. and B. Arbaugh, "Authentication for DHCP
	Messages", RFC 3118, June 2001.
	[RFC3232] Reynolds, J., "Assigned Numbers", RFC 3232, January 2002.
	8.2. Informative Reference		8.2. Informative Reference
	[RFC951] Croft, B. and J. Gilmore, "Bootstrap Protocol (BOOTP)",		[RFC0951] Croft, B. and J. Gilmore, "Bootstrap Protocol", RFC 951,
	RFC 951, September 1985.		September 1985.
	[RFC1542] Wimer, W., "Clarifications and Extensions for the		[RFC1542] Wimer, W., "Clarifications and Extensions for the
	Bootstrap Protocol", RFC 1542, October 1993.		Bootstrap Protocol", RFC 1542, October 1993.
	[RFC2132] Droms, R. and S. Alexander, "DHCP Options and BOOTP Vendor
	Extensions", RFC 2132, March 1997.
	Authors' Addresses		Authors' Addresses
	Bharat Joshi		Bharat Joshi
	Infosys Technologies Ltd.		Infosys Ltd.
	44 Electronics City, Hosur Road		44 Electronics City, Hosur Road
	Bangalore 560 100		Bangalore 560 100
	India		India
	Email: bharat_joshi@infosys.com		Email: bharat_joshi@infosys.com
	URI: http://www.infosys.com/		URI: http://www.infosys.com/
	Pavan Kurapati		Pavan Kurapati
	Juniper Networks		Juniper Networks
	Embassy Prime Buildings, C.V. Raman Nagar		Embassy Prime Buildings, C.V. Raman Nagar
End of changes. 16 change blocks.
	96 lines changed or deleted		88 lines changed or added
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