draft-ietf-v6ops-ra-guard-implementation-02.txt		draft-ietf-v6ops-ra-guard-implementation-03.txt
	IPv6 Operations Working Group (v6ops) F. Gont		IPv6 Operations Working Group (v6ops) F. Gont
	Internet-Draft UK CPNI		Internet-Draft UK CPNI
	Intended status: BCP March 8, 2012		Intended status: BCP May 11, 2012
	Expires: September 9, 2012		Expires: November 12, 2012
	Implementation Advice for IPv6 Router Advertisement Guard (RA-Guard)		Implementation Advice for IPv6 Router Advertisement Guard (RA-Guard)
	draft-ietf-v6ops-ra-guard-implementation-02		draft-ietf-v6ops-ra-guard-implementation-03
	Abstract		Abstract
	The IPv6 Router Advertisement Guard (RA-Guard) mechanism is commonly		The IPv6 Router Advertisement Guard (RA-Guard) mechanism is commonly
	employed to mitigate attack vectors based on forged ICMPv6 Router		employed to mitigate attack vectors based on forged ICMPv6 Router
	Advertisement messages. Many existing IPv6 deployments rely on RA-		Advertisement messages. Many existing IPv6 deployments rely on RA-
	Guard as the first line of defense against the aforementioned attack		Guard as the first line of defense against the aforementioned attack
	vectors. However, some implementations of RA-Guard have been found		vectors. However, some implementations of RA-Guard have been found
	to be prone to circumvention by employing IPv6 Extension Headers.		to be prone to circumvention by employing IPv6 Extension Headers.
	This document describes the evasion techniques that affect the		This document describes the evasion techniques that affect the
	skipping to change at page 1, line 39		skipping to change at page 1, line 39
	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 September 9, 2012.		This Internet-Draft will expire on November 12, 2012.
	Copyright Notice		Copyright Notice
	Copyright (c) 2012 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
	skipping to change at page 2, line 18		skipping to change at page 2, line 18
	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. Evasion techniques for some Router Advertisement Guard (RA		2. Evasion techniques for some Router Advertisement Guard (RA
	Guard) implementations . . . . . . . . . . . . . . . . . . . . 4		Guard) implementations . . . . . . . . . . . . . . . . . . . . 4
	2.1. Attack Vector based on IPv6 Extension Headers . . . . . . 4		2.1. Attack Vector based on IPv6 Extension Headers . . . . . . 4
	2.2. Attack vector based on IPv6 fragmentation . . . . . . . . 4		2.2. Attack vector based on IPv6 fragmentation . . . . . . . . 4
	3. RA-Guard implementation advice . . . . . . . . . . . . . . . . 8		3. RA-Guard implementation advice . . . . . . . . . . . . . . . . 8
	4. Other Implications . . . . . . . . . . . . . . . . . . . . . . 10		4. Other Implications . . . . . . . . . . . . . . . . . . . . . . 11
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 11		5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
	6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12		6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13		7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
	7.1. Normative References . . . . . . . . . . . . . . . . . . . 13		7.1. Normative References . . . . . . . . . . . . . . . . . . . 14
	7.2. Informative References . . . . . . . . . . . . . . . . . . 13		7.2. Informative References . . . . . . . . . . . . . . . . . . 14
	Appendix A. Changes from previous versions of the draft (to		Appendix A. Assessment tools . . . . . . . . . . . . . . . . . . 16
	be removed by the RFC Editor before publication		Appendix B. Advice and guidance to vendors . . . . . . . . . . . 17
	of this document as a RFC . . . . . . . . . . . . . . 15
	A.1. Changes from
	draft-ietf-v6ops-ra-guard-implementation-00 . . . . . . . 15
	A.2. Changes from
	draft-gont-v6ops-ra-guard-implementation-01 . . . . . . . 15
	A.3. Changes from
	draft-gont-v6ops-ra-guard-implementation-00 . . . . . . . 15
	A.4. Changes from draft-gont-v6ops-ra-guard-evasion-01 . . . . 15
	Appendix B. Assessment tools . . . . . . . . . . . . . . . . . . 16
	Appendix C. Advice and guidance to vendors . . . . . . . . . . . 17
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18
	1. Introduction		1. Introduction
	IPv6 Router Advertisement Guard (RA-Guard) is a mitigation technique		IPv6 Router Advertisement Guard (RA-Guard) is a mitigation technique
	for attack vectors based on ICMPv6 Router Advertisement messages.		for attack vectors based on ICMPv6 Router Advertisement messages.
	[RFC6104] describes the problem statement of "Rogue IPv6 Router		[RFC6104] describes the problem statement of "Rogue IPv6 Router
	Advertisements", and [RFC6105] specifies the "IPv6 Router		Advertisements", and [RFC6105] specifies the "IPv6 Router
	Advertisement Guard" functionality.		Advertisement Guard" functionality.
	The basic concept behind RA-Guard is that a layer-2 device filters		The concept behind RA-Guard is that a layer-2 device filters ICMPv6
	ICMPv6 Router Advertisement messages, according to a number of		Router Advertisement messages, according to a number of different
	different criteria. The most basic filtering criterion is that		criteria. The most basic filtering criterion is that Router
	Router Advertisement messages are discarded by the layer-2 device		Advertisement messages are discarded by the layer-2 device unless
	unless they are received on a specified port of the layer-2 device.		they are received on a specified port of the layer-2 device.
	Clearly, the effectiveness of the RA Guard mitigation relies on the		Clearly, the effectiveness of the RA Guard mitigation relies on the
	ability of the layer-2 device to identify ICMPv6 Router Advertisement		ability of the layer-2 device to identify ICMPv6 Router Advertisement
	messages.		messages.
	Some popular RA-Guard implementations have been found to be easy to		Some popular RA-Guard implementations have been found to be easy to
	circumvent by employing IPv6 extension headers [CPNI-IPv6]. This		circumvent by employing IPv6 extension headers [CPNI-IPv6]. This
	document describes such evasion techniques, and provides advice to		document describes such evasion techniques, and provides advice to
	RA-Guard implementers such that the aforementioned evasion vectors		RA-Guard implementers such that the aforementioned evasion vectors
	can be eliminated.		can be eliminated.
	skipping to change at page 8, line 12		skipping to change at page 8, line 12
	"Hdr Ext Len" field of the first Destination Options header is		"Hdr Ext Len" field of the first Destination Options header is
	present in the first fragment (rather than the second).		present in the first fragment (rather than the second).
	3. RA-Guard implementation advice		3. RA-Guard implementation advice
	The following filtering rules MUST be implemented as part of an "RA-		The following filtering rules MUST be implemented as part of an "RA-
	Guard" implementation on those ports that are not allowed to send		Guard" implementation on those ports that are not allowed to send
	ICMPv6 Router Advertisement messages, such that the vulnerabilities		ICMPv6 Router Advertisement messages, such that the vulnerabilities
	discussed in this document are eliminated:		discussed in this document are eliminated:
	1. When trying to identify an ICMPv6 Router Advertisement message,		1. If the IPv6 Source Address of the packet is not a link-local
	follow the IPv6 header chain, enforcing a limit on the maximum		address (fe80::/10), pass the packet.
	number of Extension Headers that is allowed for each packet. If
	such limit is hit before the upper-layer protocol is identified,
	silently drop the packet.
	2. If the packet is identified to be an ICMPv6 Router Advertisement		Section 6.1.2 of [RFC4861] requires nodes to discard Router
	message, silently drop the packet.		Advertisement messages if their IPv6 Source Address is not a
			link-local address.
	3. If the layer-2 device is unable to identify whether the packet is		2. If the Hop Limit is not 255, pass the packet.
			Section 6.1.2 of [RFC4861] requires nodes to discard Router
			Advertisement messages if their Hop Limit is not 255.
			3. Try to identify whether the packet is an ICMPv6 Router
			Advertisement message, by parsing the IPv6 header chain. When
			doing so, enforce a limit on the maximum number of Extension
			Headers that is allowed for each packet, and if such limit is hit
			before the upper-layer protocol is identified, drop the packet.
			[RFC6564] specifies a uniform format for IPv6 Extension
			Header, thus meaning that an IPv6 node should be able to parse
			an IPv6 header chain even if it contains Extension Headers
			that are not currently supported by that node.
			4. If the layer-2 device is unable to identify whether the packet is
	an ICMPv6 Router Advertisement message or not (i.e., the packet		an ICMPv6 Router Advertisement message or not (i.e., the packet
	is a first-fragment, and the necessary information is missing),		is a first-fragment, and the necessary information is missing),
	the IPv6 Source Address of the packet is a link-local address or
	the unspecified address (::), and the Hop Limit is 255, silently
	drop the packet.		drop the packet.
	Note: This rule should only be applied to non-fragmented IPv6		Note: This rule should only be applied to non-fragmented IPv6
	datagrams and IPv6 fragments with a Fragment Offset of 0 (non-		datagrams and IPv6 fragments with a Fragment Offset of 0 (non-
	first fragments can be safely passed, since they will never		first fragments can be safely passed, since they will never
	reassemble into a complete datagram if they are part of a		reassemble into a complete datagram if they are part of a
	Router Advertisement received on a port where such packets are		Router Advertisement received on a port where such packets are
	not allowed).		not allowed).
	4. In all other cases, pass the packet as usual.		5. If the packet is identified to be an ICMPv6 Router Advertisement
			message, drop the packet.
			6. In all other cases, pass the packet as usual.
	Note: For the purpose of enforcing the RA-Guard filtering policy,		Note: For the purpose of enforcing the RA-Guard filtering policy,
	an ESP header [RFC4303] should be considered to be an "upper-layer		an ESP header [RFC4303] should be considered to be an "upper-layer
	protocol" (that is, it should be considered the last header in the		protocol" (that is, it should be considered the last header in the
	IPv6 header chain). This means that packets employing ESP would		IPv6 header chain). This means that packets employing ESP would
	be passed by the RA-Guard device to the intended destination. If		be passed by the RA-Guard device to the intended destination. If
	the destination host does not have a security association with the		the destination host does not have a security association with the
	sender of the aforementioned IPv6 packet, the packet would be		sender of the aforementioned IPv6 packet, the packet would be
	dropped. Otherwise, if the packet is considered valid by the		dropped. Otherwise, if the packet is considered valid by the
	IPsec implementation at the receiving host and encapsulates a		IPsec implementation at the receiving host and encapsulates a
	Router Advertisement message, it is up to the receiving host what		Router Advertisement message, it is up to the receiving host what
	to do with such packet.		to do with such packet.
	In order to protect current end-node IPv6 implementations, Rule #3		If a packet is dropped due to this filtering policy, then the packet
			drop event SHOULD be logged. The logging mechanism SHOULD include a
			drop counter dedicated to RA-Guard packet drops.
			In order to protect current end-node IPv6 implementations, Rule #4
	has been defined as a default rule to drop packets that cannot be		has been defined as a default rule to drop packets that cannot be
	positively identified as RA packets or not (perhaps due to the fact		positively identified as not being Router Advertisement (RA) messages
	that it contains fragments that do not contain the entire IPv6 header		(possibly because the packet contains fragments that do not contain
	chain). This means that, at least in theory, RA-Guard could result		the entire IPv6 header chain). This means that, at least in theory,
	in false-positive blocking of some legitimate non-RA packets that		RA-Guard could result in false-positive blocking of some legitimate
	could not be positively identified as being non-RA. In order to		non-RA packets that could not be positively identified as being
	reduce the likelihood of false positives, Rule #3 also requires that		non-RA. In order to reduce the likelihood of false positives, Rule
	an RA-Guard implementation check, before dropping an unidentifiable		#1 and Rule #2 require that packets that would not pass the required
	packet, that it has an IPv6 Source Address that is a link-local		validation checks for RA messages (Section 6.1.2 of [RFC4861]) be
	address or the unspecified address (::), and that the Hop Limit is		passed without further inspection. In any case, as noted in
	255. In any case, as noted in
	[I-D.gont-6man-oversized-header-chain], IPv6 packets that fail to		[I-D.gont-6man-oversized-header-chain], IPv6 packets that fail to
	include the entire IPv6 header chain are anyway unlikely to survive		include the entire IPv6 header chain are anyway unlikely to survive
	in real networks. Whilst currently legitimate from a specifications		in real networks. Whilst currently legitimate from a specifications
	standpoint, they are virtually impossible to police with state-less		standpoint, they are virtually impossible to police with state-less
	filters and firewalls, and are hence likely to be blocked by such		filters and firewalls, and are hence likely to be blocked by such
	filters and firewalls.		filters and firewalls.
	This filtering policy assumes that host implementations require that		This filtering policy assumes that host implementations require that
	the IPv6 Source Address of ICMPv6 Router Advertisement messages be a		the IPv6 Source Address of ICMPv6 Router Advertisement messages be a
	link-local address, and that they discard the packet if this check		link-local address, and that they discard the packet if this check
	fails, as required by the current IETF specifications [RFC4861].		fails, as required by the current IETF specifications [RFC4861].
	Additionally, it assumes that hosts require the Hop Limit of Neighbor		Additionally, it assumes that hosts require the Hop Limit of Neighbor
	Discovery messages to be 255, and discard those packets otherwise.		Discovery messages to be 255, and discard those packets otherwise.
	Finally, note that the aforementioned filtering rules implicitly		The aforementioned filtering rules implicitly handle the case of
	handle the case of fragmented packets: if the RA-Guard device fails		fragmented packets: if the RA-Guard device fails to identify the
	to identify the upper-layer protocol as a result of the use of		upper-layer protocol as a result of the use of fragmentation, the
	fragmentation, the corresponding packets would be silently dropped.		corresponding packets would be dropped.
			Finally, we note that IPv6 implementations that allow overlapping
			fragments (i.e. that do not comply with [RFC5722]) might still be
			subject of RA-based attacks. However, a recent assessment of IPv6
			implementations [SI6-FRAG] with respect to their fragment reassembly
			policy seems to indicate that most current implementations comply
			with [RFC5722].
	4. Other Implications		4. Other Implications
	A similar concept to that of "RA-Guard" has been implemented for		A similar concept to that of "RA-Guard" has been implemented for
	protecting against forged DHCPv6 messages. Such protection can be		protecting against forged DHCPv6 messages. Such protection can be
	circumvented with the same techniques discussed in this document, and		circumvented with the same techniques discussed in this document, and
	the counter-measures for such evasion attack are analogous to those		the counter-measures for such evasion attack are analogous to those
	described in Section 3 of this document.		described in Section 3 of this document.
	5. Security Considerations		5. Security Considerations
	This document describes a number of techniques that have been found		This document describes a number of techniques that have been found
	to be effective to circumvent popular RA-Guard implementations, and		to be effective to circumvent popular RA-Guard implementations, and
	provides advice to RA-Guard implementations such that those evasion		provides advice to RA-Guard implementations such that those evasion
	vulnerabilities are eliminated.		vulnerabilities are eliminated.
			As noted in Section 3, IPv6 implementations that allow overlapping
			fragments (i.e. that do not comply with [RFC5722]) might still be
			subject of RA-based attacks. However, most current
			implementations seem to comply with [RFC5722].
	We note that if an attacker sends a fragmented Router Advertisement		We note that if an attacker sends a fragmented Router Advertisement
	message on a port not allowed to send such packets, the first-		message on a port not allowed to send such packets, the first-
	fragment would be dropped, and the rest of the fragments would be		fragment would be dropped, and the rest of the fragments would be
	passed. This means that the victim node would tie memory buffers for		passed. This means that the victim node would tie memory buffers for
	the aforementioned fragments, which would never reassemble into a		the aforementioned fragments, which would never reassemble into a
	complete datagram. If a large number of such packets were sent by an		complete datagram. If a large number of such packets were sent by an
	attacker, and the victim node failed to implement proper resource		attacker, and the victim node failed to implement proper resource
	management for the fragment reassembly buffer, this could lead to a		management for the fragment reassembly buffer, this could lead to a
	Denial of Service (DoS). However, this does not really introduce a		Denial of Service (DoS). However, this does not really introduce a
	new attack vector, since an attacker could always perform the same		new attack vector, since an attacker could always perform the same
	skipping to change at page 12, line 8		skipping to change at page 13, line 8
	these attacks would be to prohibit the use of IPv6 fragmentation with		these attacks would be to prohibit the use of IPv6 fragmentation with
	Router Advertisement messages (as proposed by		Router Advertisement messages (as proposed by
	[I-D.gont-6man-nd-extension-headers]), such that the RA-Guard		[I-D.gont-6man-nd-extension-headers]), such that the RA-Guard
	functionality is easier to implement. However, since such mitigation		functionality is easier to implement. However, since such mitigation
	would require an update to existing implementations, it cannot be		would require an update to existing implementations, it cannot be
	relied upon in the short or near term.		relied upon in the short or near term.
	6. Acknowledgements		6. Acknowledgements
	The author would like to thank Ran Atkinson, Karl Auer, Robert		The author would like to thank Ran Atkinson, Karl Auer, Robert
	Downie, Washam Fan, David Farmer, Marc Heuse, Ray Hunter, Simon		Downie, Washam Fan, David Farmer, Marc Heuse, Nick Hilliard, Ray
	Perreault, Arturo Servin, and Gunter van de Velde, for providing		Hunter, Simon Perreault, Arturo Servin, Gunter van de Velde, James
	valuable comments on earlier versions of this document.		Woodyatt, and Bjoern A. Zeeb, for providing valuable comments on
			earlier versions of this document.
	The author would like to thank Arturo Servin, who presented this		The author would like to thank Arturo Servin, who presented this
	document at IETF 81.		document at IETF 81.
	This document resulted from the project "Security Assessment of the		This document resulted from the project "Security Assessment of the
	Internet Protocol version 6 (IPv6)" [CPNI-IPv6], carried out by		Internet Protocol version 6 (IPv6)" [CPNI-IPv6], carried out by
	Fernando Gont on behalf of the UK Centre for the Protection of		Fernando Gont on behalf of the UK Centre for the Protection of
	National Infrastructure (CPNI). The author would like to thank the		National Infrastructure (CPNI). The author would like to thank the
	UK CPNI, for their continued support.		UK CPNI, for their continued support.
	skipping to change at page 13, line 19		skipping to change at page 14, line 19
	[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.
	[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",		[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
	RFC 4303, December 2005.		RFC 4303, December 2005.
	[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,		[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
	"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,		"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
	September 2007.		September 2007.
			[RFC5722] Krishnan, S., "Handling of Overlapping IPv6 Fragments",
			RFC 5722, December 2009.
			[RFC6564] Krishnan, S., Woodyatt, J., Kline, E., Hoagland, J., and
			M. Bhatia, "A Uniform Format for IPv6 Extension Headers",
			RFC 6564, April 2012.
	7.2. Informative References		7.2. Informative References
	[RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement		[RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement
	Problem Statement", RFC 6104, February 2011.		Problem Statement", RFC 6104, February 2011.
	[RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.		[RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.
	Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,		Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
	February 2011.		February 2011.
	[I-D.gont-6man-oversized-header-chain]		[I-D.gont-6man-oversized-header-chain]
	Gont, F. and V. Manral, "Security and Interoperability		Gont, F. and V. Manral, "Security and Interoperability
	Implications of Oversized IPv6 Header Chains",		Implications of Oversized IPv6 Header Chains",
	draft-gont-6man-oversized-header-chain-00 (work in		draft-gont-6man-oversized-header-chain-01 (work in
	progress), February 2012.		progress), April 2012.
	[I-D.gont-6man-nd-extension-headers]		[I-D.gont-6man-nd-extension-headers]
	Gont, F., "Security Implications of the Use of IPv6		Gont, F., "Security Implications of the Use of IPv6
	Extension Headers with IPv6 Neighbor Discovery",		Extension Headers with IPv6 Neighbor Discovery",
	draft-gont-6man-nd-extension-headers-02 (work in		draft-gont-6man-nd-extension-headers-02 (work in
	progress), January 2012.		progress), January 2012.
	[CPNI-IPv6]		[CPNI-IPv6]
	Gont, F., "Security Assessment of the Internet Protocol		Gont, F., "Security Assessment of the Internet Protocol
	version 6 (IPv6)", UK Centre for the Protection of		version 6 (IPv6)", UK Centre for the Protection of
	National Infrastructure, (available on request).		National Infrastructure, (available on request).
	[NDPMon] "NDPMon - IPv6 Neighbor Discovery Protocol Monitor",		[NDPMon] "NDPMon - IPv6 Neighbor Discovery Protocol Monitor",
	<http://ndpmon.sourceforge.net/>.		<http://ndpmon.sourceforge.net/>.
	[rafixd] "rafixd", <http://www.kame.net/dev/cvsweb2.cgi/kame/kame/		[rafixd] "rafixd", <http://www.kame.net/dev/cvsweb2.cgi/kame/kame/
	kame/rafixd/>.		kame/rafixd/>.
	[ramond] "ramond", <http://ramond.sourceforge.net/>.		[ramond] "ramond", <http://ramond.sourceforge.net/>.
	[THC-IPV6]		[SI6-FRAG]
	"THC-IPV6", <http://www.thc.org/thc-ipv6/>.		SI6 Networks, "IPv6 NIDS evasion and improvements in IPv6
			fragmentation/reassembly", 2012, <http://
	Appendix A. Changes from previous versions of the draft (to be removed		blog.si6networks.com/2012/02/
	by the RFC Editor before publication of this document as a		ipv6-nids-evasion-and-improvements-in.html>.
	RFC
	A.1. Changes from draft-ietf-v6ops-ra-guard-implementation-00
	o The filtering rules in Section 3 have been further clarified.
	A.2. Changes from draft-gont-v6ops-ra-guard-implementation-01
	o Document resubmitted as draft-ietf to reflect wg adoption.
	A.3. Changes from draft-gont-v6ops-ra-guard-implementation-00
	o Miscellaneous (minor) editorial changes.
	o The filtering rules in Section 3 have been polished.
	A.4. Changes from draft-gont-v6ops-ra-guard-evasion-01
	o The contents were updated to reflect that the evasion
	vulnerabilities are based on implementation flaws, rather than on
	the RA-Guard "concept" itself.
	o The I-D now focuses on providing advice to RA-Guard implementers.		[THC-IPV6]
			"The Hacker's Choice IPv6 Attack Toolkit",
			<http://www.thc.org/thc-ipv6/>.
	Appendix B. Assessment tools		Appendix A. Assessment tools
	CPNI has produced assessment tools (which have not yet been made		CPNI has produced assessment tools (which have not yet been made
	publicly available) to assess RA-Guard implementations with respect		publicly available) to assess RA-Guard implementations with respect
	to the issues described in this document. If you think that you		to the issues described in this document. If you think that you
	would benefit from these tools, we might be able to provide a copy of		would benefit from these tools, we might be able to provide a copy of
	the tools (please contact Fernando Gont at fernando@gont.com.ar).		the tools (please contact Fernando Gont at fernando@gont.com.ar).
	[THC-IPV6] is a publicly-available set of tools that implements some		[THC-IPV6] is a publicly-available set of tools that implements some
	of the techniques described in this document.		of the techniques described in this document.
	Appendix C. Advice and guidance to vendors		Appendix B. Advice and guidance to vendors
	Vendors are urged to contact CSIRTUK (csirt@cpni.gsi.gov.uk) if they		Vendors are urged to contact CSIRTUK (csirt@cpni.gsi.gov.uk) if they
	think they may be affected by the issues described in this document.		think they may be affected by the issues described in this document.
	As the lead coordination centre for these issues, CPNI is well placed		As the lead coordination centre for these issues, CPNI is well placed
	to give advice and guidance as required.		to give advice and guidance as required.
	CPNI works extensively with government departments and agencies,		CPNI works extensively with government departments and agencies,
	commercial organisations and the academic community to research		commercial organisations and the academic community to research
	vulnerabilities and potential threats to IT systems especially where		vulnerabilities and potential threats to IT systems especially where
	they may have an impact on Critical National Infrastructure's (CNI).		they may have an impact on Critical National Infrastructure's (CNI).
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