< draft-ietf-mpls-bfd-directed-05.txt		draft-ietf-mpls-bfd-directed-06.txt >
	MPLS Working Group G. Mirsky		MPLS Working Group G. Mirsky
	Internet-Draft ZTE		Internet-Draft ZTE
	Intended status: Standards Track J. Tantsura		Intended status: Standards Track J. Tantsura
	Expires: August 10, 2017 Individual		Expires: October 26, 2017 Individual
	I. Varlashkin		I. Varlashkin
	Google		Google
	M. Chen		M. Chen
	Huawei		Huawei
	February 6, 2017		April 24, 2017
	Bidirectional Forwarding Detection (BFD) Directed Return Path		Bidirectional Forwarding Detection (BFD) Directed Return Path
	draft-ietf-mpls-bfd-directed-05		draft-ietf-mpls-bfd-directed-06
	Abstract		Abstract
	Bidirectional Forwarding Detection (BFD) is expected to be able to		Bidirectional Forwarding Detection (BFD) is expected to be able to
	monitor wide variety of encapsulations of paths between systems.		monitor wide variety of encapsulations of paths between systems.
	When a BFD session monitors an explicitly routed unidirectional path		When a BFD session monitors an explicitly routed unidirectional path
	there may be a need to direct egress BFD peer to use specific path		there may be a need to direct egress BFD peer to use a specific path
	for the reverse direction of the BFD session.		for the reverse direction of the BFD session.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	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 August 10, 2017.		This Internet-Draft will expire on October 26, 2017.
	Copyright Notice		Copyright Notice
	Copyright (c) 2017 IETF Trust and the persons identified as the		Copyright (c) 2017 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 28 ¶		skipping to change at page 2, line 28 ¶
	3.1.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . 3		3.1.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . 3
	3.1.2. Static and RSVP-TE sub-TLVs . . . . . . . . . . . . . 4		3.1.2. Static and RSVP-TE sub-TLVs . . . . . . . . . . . . . 4
	3.2. Return Codes . . . . . . . . . . . . . . . . . . . . . . 5		3.2. Return Codes . . . . . . . . . . . . . . . . . . . . . . 5
	4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 5		4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 5
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
	5.1. TLV . . . . . . . . . . . . . . . . . . . . . . . . . . . 5		5.1. TLV . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
	5.2. Return Codes . . . . . . . . . . . . . . . . . . . . . . 6		5.2. Return Codes . . . . . . . . . . . . . . . . . . . . . . 6
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 6		6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6		7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
	8. Normative References . . . . . . . . . . . . . . . . . . . . 6		8. Normative References . . . . . . . . . . . . . . . . . . . . 6
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
	1. Introduction		1. Introduction
	RFC 5880 [RFC5880], RFC 5881 [RFC5881], and RFC 5883 [RFC5883]		RFC 5880 [RFC5880], RFC 5881 [RFC5881], and RFC 5883 [RFC5883]
	established the BFD protocol for IP networks and RFC 5884 [RFC5884]		established the BFD protocol for IP networks. RFC 5884 [RFC5884] and
	set rules of using BFD asynchronous mode over IP/MPLS LSPs. These		RFC 7726 [RFC7726] set rules of using BFD asynchronous mode over IP/
	standards implicitly assume that the egress BFD peer will use the		MPLS LSPs. These standards implicitly assume that the egress BFD
	shortest path route regardless of route being used to send BFD		peer will use the shortest path route regardless of route being used
	control packets towards it.		to send BFD control packets towards it.
	For the case where a LSP is explicitly routed it is likely that the		For the case where a LSP is explicitly routed it is likely that the
	shortest return path to the ingress BFD peer would not follow the		shortest return path to the ingress BFD peer would not follow the
	same path as the LSP in the forward direction. The fact that BFD		same path as the LSP in the forward direction. The fact that BFD
	control packets are not guaranteed to follow the same links and nodes		control packets are not guaranteed to follow the same links and nodes
	in both forward and reverse directions is a significant factor in		in both forward and reverse directions is a significant factor in
	producing false positive defect notifications, i.e. false alarms, if		producing false positive defect notifications, i.e. false alarms, if
	used by the ingress BFD peer to deduce the state of the forward		used by the ingress BFD peer to deduce the state of the forward
	direction.		direction.
	This document defines the BFD Reverse Path TLV as an extension to LSP		This document defines the BFD Reverse Path TLV as an extension to LSP
	Ping [RFC4379] and proposes that it is to be used to instruct the		Ping [RFC8029] and proposes that it is to be used to instruct the
	egress BFD peer to use explicit path for its BFD control packets		egress BFD peer to use an explicit path for its BFD control packets
	associated with a particular BFD session. The TLV will be allocated		associated with a particular BFD session. The TLV will be allocated
	from the TLV and sub-TLV registry defined by RFC 4379 [RFC4379]. As		from the TLV and sub-TLV registry defined by RFC 8029 [RFC8029]. As
	a special case, forward and reverse directions of the BFD session can		a special case, forward and reverse directions of the BFD session can
	form a bi-directional co-routed associated channel.		form a bi-directional co-routed associated channel.
	1.1. Conventions used in this document		1.1. Conventions used in this document
	1.1.1. Requirements Language		1.1.1. Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	skipping to change at page 3, line 38 ¶		skipping to change at page 3, line 38 ¶
	trigger, for example, protection switchover of the forward		trigger, for example, protection switchover of the forward
	direction without possibility of being a false positive.		direction without possibility of being a false positive.
	To address this scenario the egress BFD peer would be instructed to		To address this scenario the egress BFD peer would be instructed to
	use a specific path for BFD control packets.		use a specific path for BFD control packets.
	3. Direct Reverse BFD Path		3. Direct Reverse BFD Path
	3.1. Case of MPLS Data Plane		3.1. Case of MPLS Data Plane
	LSP ping, defined in [RFC4379], uses BFD Discriminator TLV [RFC5884]		LSP ping, defined in [RFC8029], uses BFD Discriminator TLV [RFC5884]
	to bootstrap a BFD session over an MPLS LSP. This document defines a		to bootstrap a BFD session over an MPLS LSP. This document defines a
	new TLV, BFD Reverse Path TLV, that MUST contain a single sub-TLV		new TLV, BFD Reverse Path TLV, that MUST contain a single sub-TLV
	that can be used to carry information about the reverse path for the		that can be used to carry information about the reverse path for the
	BFD session that is specified by value in BFD Discriminator TLV.		BFD session that is specified by value in BFD Discriminator TLV.
	3.1.1. BFD Reverse Path TLV		3.1.1. BFD Reverse Path TLV
	The BFD Reverse Path TLV is an optional TLV within the LSP ping		The BFD Reverse Path TLV is an optional TLV within the LSP ping
	[RFC4379], [RFC6424]. However, if used, the BFD Discriminator TLV		[RFC8029]. However, if used, the BFD Discriminator TLV MUST be
	MUST be included in an Echo Request message as well. If the BFD		included in an Echo Request message as well. If the BFD
	Discriminator TLV is not present when the BFD Reverse Path TLV is		Discriminator TLV is not present when the BFD Reverse Path TLV is
	included, then it MUST be treated as malformed Echo Request, as		included, then it MUST be treated as malformed Echo Request, as
	described in [RFC4379].		described in [RFC8029].
	The BFD Reverse Path TLV carries information about the path onto		The BFD Reverse Path TLV carries information about the path onto
	which the egress BFD peer of the BFD session referenced by the BFD		which the egress BFD peer of the BFD session referenced by the BFD
	Discriminator TLV MUST transmit BFD control packets. The format of		Discriminator TLV MUST transmit BFD control packets. The format of
	the BFD Reverse Path TLV is as presented in Figure 1.		the BFD Reverse Path TLV is as presented in Figure 1.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| BFD Reverse Path TLV Type | Length |		| BFD Reverse Path TLV Type | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Reverse Path |		| Reverse Path |
	~ ~		~ ~
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 1: BFD Reverse Path TLV		Figure 1: BFD Reverse Path TLV
	BFD Reverse Path TLV Type is 2 octets in length and has a value of		BFD Reverse Path TLV Type is 2 octets in length and has a value of
	TBD1 (to be assigned by IANA as requested in Section 5).		TBD1 (to be assigned by IANA as requested in Section 5).
	skipping to change at page 6, line 35 ¶		skipping to change at page 6, line 35 ¶
	| X (TBD3) | Too Many TLVs Detected. | This document |		| X (TBD3) | Too Many TLVs Detected. | This document |
	| X (TBD4) | Failed to establish the BFD session. | This document |		| X (TBD4) | Failed to establish the BFD session. | This document |
	| | The specified reverse path was not | |		| | The specified reverse path was not | |
	| | found. | |		| | found. | |
	+----------+----------------------------------------+---------------+		+----------+----------------------------------------+---------------+
	Table 2: New Return Code		Table 2: New Return Code
	6. Security Considerations		6. Security Considerations
	Security considerations discussed in [RFC5880], [RFC5884], and		Security considerations discussed in [RFC5880], [RFC5884], [RFC7726],
	[RFC4379], apply to this document.		and [RFC8029], apply to this document.
	7. Acknowledgments		7. Acknowledgments
	Authors greatly appreciate thorough review and the most helpful		Authors greatly appreciate thorough review and the most helpful
	comments from Eric Gray and Carlos Pignataro.		comments from Eric Gray and Carlos Pignataro.
	8. Normative References		8. 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,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
	Label Switched (MPLS) Data Plane Failures", RFC 4379,
	DOI 10.17487/RFC4379, February 2006,
	<http://www.rfc-editor.org/info/rfc4379>.
	[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,		[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
	"MPLS Generic Associated Channel", RFC 5586,		"MPLS Generic Associated Channel", RFC 5586,
	DOI 10.17487/RFC5586, June 2009,		DOI 10.17487/RFC5586, June 2009,
	<http://www.rfc-editor.org/info/rfc5586>.		<http://www.rfc-editor.org/info/rfc5586>.
	[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection		[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
	(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,		(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
	<http://www.rfc-editor.org/info/rfc5880>.		<http://www.rfc-editor.org/info/rfc5880>.
	[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection		[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
	skipping to change at page 7, line 33 ¶		skipping to change at page 7, line 28 ¶
	[RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection		[RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
	(BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,		(BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
	June 2010, <http://www.rfc-editor.org/info/rfc5883>.		June 2010, <http://www.rfc-editor.org/info/rfc5883>.
	[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,		[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
	"Bidirectional Forwarding Detection (BFD) for MPLS Label		"Bidirectional Forwarding Detection (BFD) for MPLS Label
	Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,		Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
	June 2010, <http://www.rfc-editor.org/info/rfc5884>.		June 2010, <http://www.rfc-editor.org/info/rfc5884>.
	[RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for
	Performing Label Switched Path Ping (LSP Ping) over MPLS
	Tunnels", RFC 6424, DOI 10.17487/RFC6424, November 2011,
	<http://www.rfc-editor.org/info/rfc6424>.
	[RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord,		[RFC7110] Chen, M., Cao, W., Ning, S., Jounay, F., and S. Delord,
	"Return Path Specified Label Switched Path (LSP) Ping",		"Return Path Specified Label Switched Path (LSP) Ping",
	RFC 7110, DOI 10.17487/RFC7110, January 2014,		RFC 7110, DOI 10.17487/RFC7110, January 2014,
	<http://www.rfc-editor.org/info/rfc7110>.		<http://www.rfc-editor.org/info/rfc7110>.
	[RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S.		[RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S.
	Aldrin, "Clarifying Procedures for Establishing BFD		Aldrin, "Clarifying Procedures for Establishing BFD
	Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726,		Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726,
	DOI 10.17487/RFC7726, January 2016,		DOI 10.17487/RFC7726, January 2016,
	<http://www.rfc-editor.org/info/rfc7726>.		<http://www.rfc-editor.org/info/rfc7726>.
			[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
			Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
			Switched (MPLS) Data-Plane Failures", RFC 8029,
			DOI 10.17487/RFC8029, March 2017,
			<http://www.rfc-editor.org/info/rfc8029>.
	Authors' Addresses		Authors' Addresses
	Greg Mirsky		Greg Mirsky
	ZTE		ZTE
	Email: gregimirsky@gmail.com		Email: gregimirsky@gmail.com
	Jeff Tantsura		Jeff Tantsura
	Individual		Individual
	Email: jefftant.ietf@gmail.com		Email: jefftant.ietf@gmail.com
	Ilya Varlashkin		Ilya Varlashkin
	Google		Google
	Email: Ilya@nobulus.com		Email: Ilya@nobulus.com
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