draft-ietf-6man-enhanced-dad-04.txt		draft-ietf-6man-enhanced-dad-05.txt
	Network Working Group R. Asati		Network Working Group R. Asati
	Internet-Draft H. Singh		Internet-Draft H. Singh
	Updates: 4862, 4861 (if approved) W. Beebee		Updates: 4862, 4861, 3971 (if approved) W. Beebee
	Intended status: Standards Track Cisco Systems, Inc.		Intended status: Standards Track Cisco Systems, Inc.
	Expires: May 08, 2014 E. Dart		Expires: November 3, 2014 E. Dart
	Lawrence Berkeley National Laboratory		Lawrence Berkeley National Laboratory
	W. George		W. George
	Time Warner Cable		Time Warner Cable
	C. Pignataro		C. Pignataro
	Cisco Systems, Inc.		Cisco Systems, Inc.
	November 04, 2013		May 2, 2014
	Enhanced Duplicate Address Detection		Enhanced Duplicate Address Detection
	draft-ietf-6man-enhanced-dad-04		draft-ietf-6man-enhanced-dad-05
	Abstract		Abstract
	Appendix A of the IPv6 Duplicate Address Detection (DAD) document in		Appendix A of the IPv6 Duplicate Address Detection (DAD) document in
	RFC 4862 discusses Loopback Suppression and DAD. However, RFC 4862		RFC 4862 discusses Loopback Suppression and DAD. However, RFC 4862
	does not settle on one specific automated means to detect loopback of		does not settle on one specific automated means to detect loopback of
	Neighbor Discovery (ND of RFC 4861) messages used by DAD. Several		Neighbor Discovery (ND of RFC 4861) messages used by DAD. Several
	service provider communities have expressed a need for automated		service provider communities have expressed a need for automated
	detection of looped backed ND messages used by DAD. This document		detection of looped backed ND messages used by DAD. This document
	includes mitigation techniques and then outlines the Enhanced DAD		includes mitigation techniques and then outlines the Enhanced DAD
	skipping to change at page 1, line 48		skipping to change at page 1, line 48
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on May 08, 2014.		This Internet-Draft will expire on November 3, 2014.
	Copyright Notice		Copyright Notice
	Copyright (c) 2013 IETF Trust and the persons identified as the		Copyright (c) 2014 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
			1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
	2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Operational Mitigation Options . . . . . . . . . . . . . . . 4		3. Operational Mitigation Options . . . . . . . . . . . . . . . 4
	3.1. Disable DAD on Interface . . . . . . . . . . . . . . . . 4		3.1. Disable DAD on Interface . . . . . . . . . . . . . . . . 5
	3.2. Dynamic Disable/Enable of DAD Using Layer 2 Protocol . . 5		3.2. Dynamic Disable/Enable of DAD Using Layer 2 Protocol . . 5
	3.3. Operational Considerations . . . . . . . . . . . . . . . 5		3.3. Operational Considerations . . . . . . . . . . . . . . . 6
	4. The Enhanced DAD Algorithm . . . . . . . . . . . . . . . . . 6		4. The Enhanced DAD Algorithm . . . . . . . . . . . . . . . . . 6
	4.1. General Rules . . . . . . . . . . . . . . . . . . . . . . 7		4.1. General Rules . . . . . . . . . . . . . . . . . . . . . . 7
	4.2. Processing Rules for Senders . . . . . . . . . . . . . . 7		4.2. Processing Rules for Senders . . . . . . . . . . . . . . 7
	4.3. Processing Rules for Receivers . . . . . . . . . . . . . 8		4.3. Processing Rules for Receivers . . . . . . . . . . . . . 7
	4.4. Impact on SEND . . . . . . . . . . . . . . . . . . . . . 8		4.4. Impact on SEND . . . . . . . . . . . . . . . . . . . . . 8
	4.5. Changes to RFC 4862 . . . . . . . . . . . . . . . . . . . 8		4.5. Changes to RFC 4862 . . . . . . . . . . . . . . . . . . . 8
	4.6. Changes to RFC 4861 . . . . . . . . . . . . . . . . . . . 9		4.6. Changes to RFC 4861 . . . . . . . . . . . . . . . . . . . 9
			4.7. Changes to RFC 3971 . . . . . . . . . . . . . . . . . . . 9
	5. Actions to Perform on Detecting a Genuine Duplicate . . . . . 9		5. Actions to Perform on Detecting a Genuine Duplicate . . . . . 9
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 10		6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
	8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10		8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
	9. Normative References . . . . . . . . . . . . . . . . . . . . 10		9. Normative References . . . . . . . . . . . . . . . . . . . . 10
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
	1. Terminology		1. Terminology
	o DAD-failed state - Duplication Address Detection failure as		o DAD-failed state - Duplication Address Detection failure as
	specified in [RFC4862]. Failure also includes if the Target		specified in [RFC4862]. Note even Optimistic DAD as specified in
	Address is optimistic. Optimistic DAD is specified in [RFC4429].		[RFC4429] can fail due to a looped back DAD probe. This document
			covers looped back detection for Optimistic DAD as well.
	o Looped back message - also referred to as a reflected message.		o Looped back message - also referred to as a reflected message.
	The message sent by the sender is received by the sender due to		The message sent by the sender is received by the sender due to
	the network or a Upper Layer Protocol on the sender looping the		the network or a Upper Layer Protocol on the sender looping the
	message back.		message back.
	o Loopback - A function in which the router's interface (or the		o Loopback - A function in which the router's interface (or the
	circuit to which the router's interface is connected) is looped		circuit to which the router's interface is connected) is looped
	back or connected to itself. Loopback causes packets sent by the		back or connected to itself. Loopback causes packets sent by the
	interface to be received by the interface, and results in		interface to be received by the interface, and results in
	interface unavailability for regular data traffic forwarding. See		interface unavailability for regular data traffic forwarding. See
	more details in section 9.1 of [RFC1247]. The Loopback function		more details in section 9.1 of [RFC1583]. The Loopback function
	is commonly used in an interface context to gain information on		is commonly used in an interface context to gain information on
	the quality of the interface, by employing mechanisms such as		the quality of the interface, by employing mechanisms such as
	ICMPv6 pings, bit-error tests, etc. In a circuit context, it is		ICMPv6 pings, bit-error tests, etc. In a circuit context, it is
	used in wide area environments including optical dense wave		used in wide area environments including optical dense wave
	division multiplexing (DWDM) and SONET/SDH for fault isolation		division multiplexing (DWDM) and SONET/SDH for fault isolation
	(e.g. by placing a loopback at different geographic locations		(e.g. by placing a loopback at different geographic locations
	along the path of a wide area circuit to help locate a circuit		along the path of a wide area circuit to help locate a circuit
	fault). The Loopback function may be employed locally or		fault). The Loopback function may be employed locally or
	remotely.		remotely.
	o NS(DAD) - shorthand notation to denote an Neighbor Solicitation		o NS(DAD) - shorthand notation to denote an Neighbor Solicitation
	(NS) with unspecified IPv6 source-address issued during DAD.		(NS) with unspecified IPv6 source-address issued during DAD.
			1.1. Requirements Language
			The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
			"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
			document are to be interpreted as described in RFC 2119 [RFC2119].
	2. Introduction		2. Introduction
	Appendix A of [RFC4862] discusses Loopback Suppression and Duplicate		Appendix A of [RFC4862] discusses Loopback Suppression and Duplicate
	Address Detection (DAD). However, [RFC4862] does not settle on one		Address Detection (DAD). However, [RFC4862] does not settle on one
	specific automated means to detect loopback of ND messages used by		specific automated means to detect loopback of ND messages used by
	DAD. One specific DAD message is a Neighbor Solicitation (NS),		DAD. One specific DAD message is a Neighbor Solicitation (NS),
	specified in [RFC4861]. The NS is issued by the network interface of		specified in [RFC4861]. The NS is issued by the network interface of
	an IPv6 node for DAD. Another message involved in DAD is a Neighbor		an IPv6 node for DAD. Another message involved in DAD is a Neighbor
	Advertisement (NA). The Enhanced DAD algorithm proposed in this		Advertisement (NA). The Enhanced DAD algorithm proposed in this
	document focuses on detecting an NS looped back to the transmitting		document focuses on detecting an NS looped back to the transmitting
	skipping to change at page 5, line 23		skipping to change at page 5, line 35
	PPP uses magic number (section 6.4 of [RFC1661]) to detect a loopback		PPP uses magic number (section 6.4 of [RFC1661]) to detect a loopback
	on an interface.		on an interface.
	When a layer 2 protocol detects that a loopback is present on an		When a layer 2 protocol detects that a loopback is present on an
	interface circuit, the device MUST temporarily disable DAD on the		interface circuit, the device MUST temporarily disable DAD on the
	interface, and when the protocol detects that a loopback is no longer		interface, and when the protocol detects that a loopback is no longer
	present (or the interface state has changed), the device MUST		present (or the interface state has changed), the device MUST
	(re-)enable DAD on that interface.		(re-)enable DAD on that interface.
	This solution requires no protocol changes. This solution SHOULD be		This solution requires no protocol changes. This solution SHOULD be
	enabled by default, and MUST be a configurable option.		enabled by default, and MUST be a configurable option if the layer 2
			technology provides means for detecting loopback messages on an
			interface circuit.
	This mitigation has several benefits. They are		This mitigation has several benefits. They are
	1. It leverages layer 2 protocol's built-in loopback detection		1. It leverages layer 2 protocol's built-in loopback detection
	capability, if available.		capability, if available.
	2. It scales better since it relies on an event-driven model which		2. It scales better since it relies on an event-driven model which
	requires no additional state or timer. This may be a significant		requires no additional state or timer. This may be a significant
	scaling consideration on devices with hundreds or thousands of		scaling consideration on devices with hundreds or thousands of
	interfaces that may be in loopback for long periods of time (such		interfaces that may be in loopback for long periods of time (such
	skipping to change at page 6, line 19		skipping to change at page 6, line 36
	as usual.		as usual.
	4. The Enhanced DAD Algorithm		4. The Enhanced DAD Algorithm
	The Enhanced DAD algorithm covers detection of a looped back NS(DAD)		The Enhanced DAD algorithm covers detection of a looped back NS(DAD)
	message. The document proposes use of the Nonce Option specified in		message. The document proposes use of the Nonce Option specified in
	the SEND document of [RFC3971]. The nonce is a random number as		the SEND document of [RFC3971]. The nonce is a random number as
	specified in [RFC3971]. If SEND is enabled on the router and the		specified in [RFC3971]. If SEND is enabled on the router and the
	router also supports the Enhanced DAD algorithm (specified in this		router also supports the Enhanced DAD algorithm (specified in this
	document), there is integration with the Enhanced DAD algorithm and		document), there is integration with the Enhanced DAD algorithm and
	SEND. See more details in the Impact on SEND section. Since a nonce		SEND. See more details in the Impact on SEND section in section 4.4.
	is used only once, DAD for each IPv6 address of an interface uses a		Since a nonce is used only once, DAD for each IPv6 address of an
	different nonce.		interface uses a different nonce. Additional details of the
			algorithm are included in section 4.2.
	The interface follows [RFC4862] behavior by issuing
	DupAddrDetectTransmits (see [RFC4862]) probes spaced RetransTimer
	(see [RFC4861]) apart. When the IPv6 network interface issues a
	NS(DAD) message, the interface includes the Nonce Option in the
	NS(DAD) message and saves the nonce in local store. Subsequently if
	the interface receives an identical NS(DAD) message, the interface
	logs a system management message, updates any statistics counter,
	drops the looped back NS(DAD). If any probe is looped back within
	RetransTimer milliseconds after having sent DupAddrDetectTransmits
	NS(DAD) messages, the interface continues with another
	MAX_MULTICAST_SOLICIT number of NS(DAD) messages spaced RetransTimer
	apart. If no probe is looped back within RetransTimer milliseconds
	after MAX_MULTICAST_SOLICIT NS(DAD) messages are sent, the probing
	stops else a new MAX_MULTICAST_SOLICIT number of NS(DAD) messages
	sequence is initiated. The MAX_MULTICAST_SOLICIT number of NS(DAD)
	messages sequence continues until the stop condition is reached. The
	RetransTimer may be overidden by a link-specific document if a node
	supports the Enhanced DAD algorithm. Note
	[I-D.ietf-6man-impatient-nud] has intentions to change probe behavior
	of [RFC4861].
	If the interface receives a NS(DAD) message with a different nonce
	but the Target Address matches a tentative or optimistic address on
	the interface, the interface logs a DAD-failed system management
	message, updates any statistics, and behaves identical to the
	behavior specified in [RFC4862] for DAD failure.
	Six bytes of random nonce is sufficiently large for nonce collisions.		Six bytes of random nonce is sufficiently large for nonce collisions.
	However if there is a collision because two nodes that are using the		However if there is a collision because two nodes that are using the
	same Target Address in their NS(DAD) generated the same random nonce,		same Target Address in their NS(DAD) generated the same random nonce,
	then the algorithm will incorrectly detect a looped back NS(DAD) when		then the algorithm will incorrectly detect a looped back NS(DAD) when
	a genuine address collision has occurred. Since each looped back		a genuine address collision has occurred. Since each looped back
	NS(DAD) event is logged to system management, the administrator of		NS(DAD) event is logged to system management, the administrator of
	the network will have access to the information necessary to		the network will have access to the information necessary to
	intervene manually. Also, because the nodes will have detected what		intervene manually. Also, because the nodes will have detected what
	appear to be looped back NS(DAD) messages, they will continue to		appear to be looped back NS(DAD) messages, they will continue to
	skipping to change at page 7, line 45		skipping to change at page 7, line 37
	having sent DupAddrDetectTransmits Neighbor Solicitations, the		having sent DupAddrDetectTransmits Neighbor Solicitations, the
	interface moves the Target Address to assigned state. If any probe		interface moves the Target Address to assigned state. If any probe
	is looped back within RetransTimer milliseconds after having sent		is looped back within RetransTimer milliseconds after having sent
	DupAddrDetectTransmits NS(DAD) messages, the interface continues with		DupAddrDetectTransmits NS(DAD) messages, the interface continues with
	another MAX_MULTICAST_SOLICIT number of NS(DAD) messages spaced		another MAX_MULTICAST_SOLICIT number of NS(DAD) messages spaced
	RetransTimer apart. If no probe is looped back within RetransTimer		RetransTimer apart. If no probe is looped back within RetransTimer
	milliseconds after MAX_MULTICAST_SOLICIT NS(DAD) messages are sent,		milliseconds after MAX_MULTICAST_SOLICIT NS(DAD) messages are sent,
	the probing stops else a new MAX_MULTICAST_SOLICIT number of NS(DAD)		the probing stops else a new MAX_MULTICAST_SOLICIT number of NS(DAD)
	messages sequence is initiated. The MAX_MULTICAST_SOLICIT number of		messages sequence is initiated. The MAX_MULTICAST_SOLICIT number of
	NS(DAD) messages sequence continues until the stop condition is		NS(DAD) messages sequence continues until the stop condition is
	reached.		reached or manual intervention is undertaken. The interface moves
			the Target Address to assigned state.
	4.3. Processing Rules for Receivers		4.3. Processing Rules for Receivers
	If the node has been configured to use the Enhanced DAD algorithm and		If the node has been configured to use the Enhanced DAD algorithm and
	an interface on the node receives any NS(DAD) message where the		an interface on the node receives any NS(DAD) message where the
	Target Address matches the interface address (in tentative or		Target Address matches the interface address (in tentative or
	optimistic state), the receiver compares the nonce, if any, is		optimistic state), the receiver compares the nonce, if any, is
	included in the message with any saved nonce on the receiving		included in the message with any saved nonce on the receiving
	interface. If a match is found, the node SHOULD log a system		interface. If a match is found, the node SHOULD log a system
	management message, SHOULD update any statistics counter, MUST drop		management message, SHOULD update any statistics counter, MUST drop
	skipping to change at page 8, line 36		skipping to change at page 8, line 22
	detecting looped back ND messages. If this document updates		detecting looped back ND messages. If this document updates
	[RFC4862], SEND should be updated to integrate with the Enhanced DAD		[RFC4862], SEND should be updated to integrate with the Enhanced DAD
	algorithm. A minor update to SEND would be to explicitly mention		algorithm. A minor update to SEND would be to explicitly mention
	that the nonce in SEND is also used by SEND to detect looped back NS		that the nonce in SEND is also used by SEND to detect looped back NS
	messages during DAD operations by the node. In a mixed SEND		messages during DAD operations by the node. In a mixed SEND
	environment with SEND and unsecured nodes, the lengths of the nonce		environment with SEND and unsecured nodes, the lengths of the nonce
	used by SEND and unsecured nodes MUST be identical.		used by SEND and unsecured nodes MUST be identical.
	4.5. Changes to RFC 4862		4.5. Changes to RFC 4862
	The following text is added to [RFC4862].		The following text is added to the end of the Introduction section of
			[RFC4862].
	A network interface of an IPv6 node SHOULD implement the Enhanced DAD		A network interface of an IPv6 node SHOULD implement the Enhanced DAD
	algorithm. For example, if the interface on an IPv6 node is		algorithm. For example, if the interface on an IPv6 node is
	connected to a circuit that supports loopback testing, then the node		connected to a circuit that supports loopback testing, then the node
	should implement the Enhanced DAD algorithm that allows the IPv6		should implement the Enhanced DAD algorithm that allows the IPv6
	interface to self-heal after loopback testing is ended on the		interface to self-heal after loopback testing is ended on the
	circuit. Another example is when the IPv6 interface resides on an		circuit. Another example is when the IPv6 interface resides on an
	access concentrator running DAD Proxy. The interface supports up to		access concentrator running DAD Proxy. The interface supports up to
	100 thousand IPv6 clients (broadband modems) connected to the		100 thousand IPv6 clients (broadband modems) connected to the
	interface. If the interface performs DAD for its IPv6 link-local		interface. If the interface performs DAD for its IPv6 link-local
	address and if the DAD probe is reflected back to the interface, the		address and if the DAD probe is reflected back to the interface, the
	interface is stuck in DAD failed state and IPv6 services to the 100		interface is stuck in DAD failed state and IPv6 services to the 100
	thousand clients is denied. Disabling DAD for such an IPv6 interface		thousand clients is denied. Disabling DAD for such an IPv6 interface
	on an access concentrator is not an option because the network also		on an access concentrator is not an option because the network also
	needs to detect genuine duplicates in the interface downstream		needs to detect genuine duplicates in the interface downstream
	network. The Enhanced DAD algorithm also facilitates detecting a		network. The Enhanced DAD algorithm also facilitates detecting a
	genuine duplicate for the interface on the access concentrator. See		genuine duplicate for the interface on the access concentrator. See
	the Actions to Perform on Detecting a Genuine Duplicate section of		the Actions to Perform on Detecting a Genuine Duplicate section of
	the Enhanced DAD document.		the Enhanced DAD document.
			The following text is added to the end of Appendix A of [RFC4862].
			The Enhanced DAD algorithm from TBD RFC is designed to detect looped
			back DAD probes. A network interface of an IPv6 node SHOULD
			implement the Enhanced DAD algorithm.
	4.6. Changes to RFC 4861		4.6. Changes to RFC 4861
	1. The RetransTimer may be overridden by a link-specific document if		The following text is appended to the RetransTimer variable
	a node supports the Enhanced DAD algorithm.		description in section 6.3.2 of [RFC4861].
	2. If a node has been configured to use the Enhanced DAD algorithm,		The RetransTimer may be overridden by a link-specific document if a
	an NS with an unspecified source address adds the Nonce option to		node supports the Enhanced DAD algorithm.
	the message and implements the state machine of the Enhanced DAD
	algorithm.		The following text is appended to the Source Address definition in
			section 4.3 of [RFC4861].
			If a node has been configured to use the Enhanced DAD algorithm, an
			NS with an unspecified source address adds the Nonce option to the
			message and implements the state machine of the Enhanced DAD
			algorithm.
			4.7. Changes to RFC 3971
			The following text is changed in section 5.3.2 of [RFC3971].
			The purpose of the Nonce option is to make sure that an advertisement
			is a fresh response to a solicitation sent earlier by the node.
			New text is included below.
			The purpose of the Nonce option is to make sure that an advertisement
			is a fresh response to a solicitation sent earlier by the node. The
			nonce is also used to detect looped back NS messages when the network
			interface performs DAD [RFC4862]. Detecting looped back DAD messages
			is covered by the Enhanced DAD algorithm as specified in TBD RFC. In
			a mixed SEND environment with SEND and unsecured nodes, the lengths
			of the nonce used by SEND and unsecured nodes MUST be identical.
	5. Actions to Perform on Detecting a Genuine Duplicate		5. Actions to Perform on Detecting a Genuine Duplicate
	As described in paragraphs above the nonce can also serve to detect		As described in paragraphs above the nonce can also serve to detect
	genuine duplicates even when the network has potential for looping		genuine duplicates even when the network has potential for looping
	back ND messages. When a genuine duplicate is detected, the node		back ND messages. When a genuine duplicate is detected, the node
	follows the manual intervention specified in section 5.4.5 of		follows the manual intervention specified in section 5.4.5 of
	[RFC4862]. However, in certain networks such as an access network if		[RFC4862]. However, in certain networks such as an access network if
	the genuine duplicate matches the tentative or optimistic IPv6		the genuine duplicate matches the tentative or optimistic IPv6
	address of a network interface of the access concentrator, automated		address of a network interface of the access concentrator, automated
	skipping to change at page 10, line 9		skipping to change at page 10, line 22
	have a desire to take automated action if a network interface of the		have a desire to take automated action if a network interface of the
	trusted router has a tentative or optimistic address duplicate with a		trusted router has a tentative or optimistic address duplicate with a
	host served by trusted router interface. Any other network that		host served by trusted router interface. Any other network that
	follows the same trust model MAY use the automated actions proposed		follows the same trust model MAY use the automated actions proposed
	in this section.		in this section.
	6. Security Considerations		6. Security Considerations
	The nonce can be exploited by a rogue deliberately changing the nonce		The nonce can be exploited by a rogue deliberately changing the nonce
	to fail the looped back detection specified by the Enhanced DAD		to fail the looped back detection specified by the Enhanced DAD
	algorithm. SEND is recommended for this exploit. For any mitigation		algorithm. SEND is recommended to circumvent this exploit. For any
	suggested in the document such as disabling DAD has an obvious		mitigation suggested in the document such as disabling DAD has an
	security issue before a remote node on the link can issue reflected		obvious security issue before a remote node on the link can issue
	NS(DAD) messages. Again, SEND is recommended for this exploit.		reflected NS(DAD) messages. Again, SEND is recommended for this
			exploit.
	7. IANA Considerations		7. IANA Considerations
	None.		None.
	8. Acknowledgements		8. Acknowledgements
	Thanks (in alphabetical order by first name) to Dmitry Anipko, Eric		Thanks (in alphabetical order by first name) to Dmitry Anipko, Eric
	Levy-Abegnoli, Erik Nordmark, Fred Templin, Michael Sinatra, Ole		Levy-Abegnoli, Erik Nordmark, Fred Templin, Jouni Korhonen, Michael
	Troan, Ray Hunter, Suresh Krishnan, and Tassos Chatzithomaoglou for		Sinatra, Ole Troan, Ray Hunter, Suresh Krishnan, and Tassos
	their guidance and review of the document. Thanks to Thomas Narten		Chatzithomaoglou for their guidance and review of the document.
	for encouraging this work. Thanks to Steinar Haug and Scott Beuker		Thanks to Thomas Narten for encouraging this work. Thanks to Steinar
	for describing the use cases.		Haug and Scott Beuker for describing the use cases.
	9. Normative References		9. Normative References
	[I-D.ietf-6man-impatient-nud]		[RFC1583] Moy, J., "OSPF Version 2", RFC 1583, March 1994.
	Nordmark, E. and I. Gashinsky, "Neighbor Unreachability
	Detection is too impatient", draft-ietf-6man-impatient-
	nud-07 (work in progress), October 2013.
	[RFC1247] Moy, J., "OSPF Version 2", RFC 1247, July 1991.
	[RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,		[RFC1661] Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
	RFC 1661, July 1994.		RFC 1661, July 1994.
	[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.
	[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure		[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
	Neighbor Discovery (SEND)", RFC 3971, March 2005.		Neighbor Discovery (SEND)", RFC 3971, March 2005.
End of changes. 24 change blocks.
	66 lines changed or deleted		78 lines changed or added
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