< draft-ietf-mpls-bfd-directed-07.txt		draft-ietf-mpls-bfd-directed-08.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: December 15, 2017 Individual		Expires: June 8, 2018 Individual
	I. Varlashkin		I. Varlashkin
	Google		Google
	M. Chen		M. Chen
	Huawei		Huawei
	June 13, 2017		December 5, 2017
	Bidirectional Forwarding Detection (BFD) Directed Return Path		Bidirectional Forwarding Detection (BFD) Directed Return Path
	draft-ietf-mpls-bfd-directed-07		draft-ietf-mpls-bfd-directed-08
	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 a 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 https://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 December 15, 2017.		This Internet-Draft will expire on June 8, 2018.
	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		(https://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 . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Conventions used in this document . . . . . . . . . . . . 3		1.1. Conventions used in this document . . . . . . . . . . . . 3
	1.1.1. Requirements Language . . . . . . . . . . . . . . . . 3		1.1.1. Requirements Language . . . . . . . . . . . . . . . . 3
	2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3		2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
	3. Control of the Reverse BFD Path . . . . . . . . . . . . . . . 3		3. Control of the Reverse BFD Path . . . . . . . . . . . . . . . 3
	3.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . . . 3		3.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . . . 3
	3.2. Static and RSVP-TE sub-TLVs . . . . . . . . . . . . . . . 4		3.2. Static and RSVP-TE sub-TLVs . . . . . . . . . . . . . . . 5
	3.3. Return Codes . . . . . . . . . . . . . . . . . . . . . . 5		3.3. Return Codes . . . . . . . . . . . . . . . . . . . . . . 5
	4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 5		4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 5
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	5.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . . . 5		5.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . . . 6
	5.2. Return Code . . . . . . . . . . . . . . . . . . . . . . . 6		5.2. Return Code . . . . . . . . . . . . . . . . . . . . . . . 6
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 6		6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	7. Normative References . . . . . . . . . . . . . . . . . . . . 6		7. Normative References . . . . . . . . . . . . . . . . . . . . 6
	Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 7		Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 8
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	[RFC5880], [RFC5881], and [RFC5883] established the BFD protocol for		[RFC5880], [RFC5881], and [RFC5883] established the BFD protocol for
	IP networks. [RFC5884] and [RFC7726] set rules of using BFD		IP networks. [RFC5884] and [RFC7726] set rules of using BFD
	asynchronous mode over IP/MPLS LSPs. These standards implicitly		asynchronous mode over IP/MPLS LSPs. These standards implicitly
	assume that the egress BFD peer will use the shortest path route		assume that the egress BFD peer will use the shortest path route
	regardless of route being used to send BFD control packets towards		regardless of route being used to send BFD control packets towards
	it.		it.
	skipping to change at page 4, line 10 ¶		skipping to change at page 4, line 10 ¶
	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 [RFC8029].		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).
	Length field is 2 octets long and defines the length in octets of the		Length field is 2 octets long and defines the length in octets of the
	Reverse Path field.		Reverse Path field.
	Reverse Path field contains a sub-TLV. Any Target FEC sub-TLV		Reverse Path field contains a sub-TLV. Any non-multicast Target FEC
	(already defined, or to be defined in the future) for TLV Types 1,		Stack sub-TLV (already defined, or to be defined in the future) for
	16, and 21 of MPLS LSP Ping Parameters registry MAY be used in this		TLV Types 1, 16, and 21 of MPLS LSP Ping Parameters registry MAY be
	field. None, one or more sub-TLVs MAY be included in the BFD Reverse		used in this field. Multicast Target FEC Stack sub-TLVs, i.e. p2mp
	Path TLV. If none sub-TLVs found in the BFD Reverse Path TLV, the		and mp2mp, SHOULD NOT be included into Reverse Path field. If the
	egress BFD peer MUST revert to using the default, i.e., over IP		egress LSR finds multicast Target Stack sub-TLV it MUST send echo
	network, reverse path.		reply with the received Reverse Path TLV, BFD Discriminator TLV and
			set the Return Code to "Inappropriate Target FEC Stack sub-TLV
			present" Section 3.3. None, one or more sub-TLVs MAY be included in
			the BFD Reverse Path TLV. If none sub-TLVs found in the BFD Reverse
			Path TLV, the egress BFD peer MUST revert to using the local policy
			based decision as described in Section 7 [RFC5884], i.e., routed over
			IP network.
	If the egress LSR cannot find the path specified in the Reverse Path		If the egress LSR cannot find the path specified in the Reverse Path
	TLV it MUST send Echo Reply with the received Reverse Path TLV and		TLV it MUST send Echo Reply with the received BFD Discriminator TLV,
	set the Return Code to "Failed to establish the BFD session. The		Reverse Path TLV and set the Return Code to "Failed to establish the
	specified reverse path was not found" Section 3.3. The egress BFD		BFD session. The specified reverse path was not found" Section 3.3.
	peer MAY establish the BFD session over IP network as defined in		The egress BFD peer MAY establish the BFD session over IP network as
	[RFC5884].		defined in [RFC5884].
	3.2. Static and RSVP-TE sub-TLVs		3.2. Static and RSVP-TE sub-TLVs
	When an explicit path on an MPLS data plane is set either as Static		When an explicit path on an MPLS data plane is set either as Static
	or RSVP-TE LSP respective sub-TLVs defined in [RFC7110] MAY be used		or RSVP-TE LSP respective sub-TLVs defined in [RFC7110] MAY be used
	to identify the explicit reverse path for the BFD session.		to identify the explicit reverse path for the BFD session.
	3.3. Return Codes		3.3. Return Codes
	This document defines the following Return Codes for MPLS LSP Echo		This document defines the following Return Codes for MPLS LSP Echo
	Reply:		Reply:
			o "Inappropriate Target FEC Stack sub-TLV present", (TBD3). When
			multicast Target FEC Stack sub-TLV found in the received Echo
			Request by the egress BFD peer, an Echo Reply with the return code
			set to "Inappropriate Target FEC Stack sub-TLV present" MUST be
			sent to the ingress BFD peer Section 3.1.
	o "Failed to establish the BFD session. The specified reverse path		o "Failed to establish the BFD session. The specified reverse path
	was not found", (TBD4). When a specified reverse path is not		was not found", (TBD4). When a specified reverse path is not
	available at the egress BFD peer, an Echo Reply with the return		available at the egress BFD peer, an Echo Reply with the return
	code set to "Failed to establish the BFD session. The specified		code set to "Failed to establish the BFD session. The specified
	reverse path was not found" MUST be sent back to the ingress BFD		reverse path was not found" MUST be sent back to the ingress BFD
	peer Section 3.1.		peer Section 3.1.
	4. Use Case Scenario		4. Use Case Scenario
	In the network presented in Figure 2 node A monitors two tunnels to		In the network presented in Figure 2 node A monitors two tunnels to
	skipping to change at page 6, line 5 ¶		skipping to change at page 6, line 14 ¶
	5. IANA Considerations		5. IANA Considerations
	5.1. BFD Reverse Path TLV		5.1. BFD Reverse Path TLV
	The IANA is requested to assign a new value for BFD Reverse Path TLV		The IANA is requested to assign a new value for BFD Reverse Path TLV
	from the "Multiprotocol Label Switching Architecture (MPLS) Label		from the "Multiprotocol Label Switching Architecture (MPLS) Label
	Switched Paths (LSPs) Ping Parameters - TLVs" registry, "TLVs and		Switched Paths (LSPs) Ping Parameters - TLVs" registry, "TLVs and
	sub-TLVs" sub-registry.		sub-TLVs" sub-registry.
	+----------+----------------------+---------------+		+--------+----------------------+---------------+
	| Value | Description | Reference |		| Value | Description | Reference |
	+----------+----------------------+---------------+		+--------+----------------------+---------------+
	| X (TBD1) | BFD Reverse Path TLV | This document |		| (TBD1) | BFD Reverse Path TLV | This document |
	+----------+----------------------+---------------+		+--------+----------------------+---------------+
	Table 1: New BFD Reverse Type TLV		Table 1: New BFD Reverse Type TLV
	5.2. Return Code		5.2. Return Code
	The IANA is requested to assign a new Return Code value from the		The IANA is requested to assign a new Return Code value from the
	"Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs)		"Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs)
	Ping Parameters" registry, "Return Codes" sub-registry, as follows		Ping Parameters" registry, "Return Codes" sub-registry, as follows
	using a Standards Action value.		using a Standards Action value.
	+----------+----------------------------------------+---------------+		+--------+------------------------------------------+---------------+
	| Value | Description | Reference |		| Value | Description | Reference |
	+----------+----------------------------------------+---------------+		+--------+------------------------------------------+---------------+
	| X (TBD4) | Failed to establish the BFD session. | This document |		| (TBD3) | Inappropriate Target FEC Stack sub-TLV | This document |
	| | The specified reverse path was not | |		| | present. | |
	| | found. | |		| (TBD4) | Failed to establish the BFD session. The | This document |
	+----------+----------------------------------------+---------------+		| | specified reverse path was not found. | |
			+--------+------------------------------------------+---------------+
	Table 2: New Return Code		Table 2: New Return Code
	6. Security Considerations		6. Security Considerations
	Security considerations discussed in [RFC5880], [RFC5884], [RFC7726],		Security considerations discussed in [RFC5880], [RFC5884], [RFC7726],
	and [RFC8029], apply to this document.		and [RFC8029], apply to this document.
	7. Normative References		7. 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>.		<https://www.rfc-editor.org/info/rfc2119>.
	[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>.		<https://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>.		<https://www.rfc-editor.org/info/rfc5880>.
	[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection		[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
	(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,		(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
	DOI 10.17487/RFC5881, June 2010,		DOI 10.17487/RFC5881, June 2010,
	<http://www.rfc-editor.org/info/rfc5881>.		<https://www.rfc-editor.org/info/rfc5881>.
	[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, <https://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, <https://www.rfc-editor.org/info/rfc5884>.
	[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>.		<https://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>.		<https://www.rfc-editor.org/info/rfc7726>.
	[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,		[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
	Aldrin, S., and M. Chen, "Detecting Multiprotocol Label		Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
	Switched (MPLS) Data-Plane Failures", RFC 8029,		Switched (MPLS) Data-Plane Failures", RFC 8029,
	DOI 10.17487/RFC8029, March 2017,		DOI 10.17487/RFC8029, March 2017,
	<http://www.rfc-editor.org/info/rfc8029>.		<https://www.rfc-editor.org/info/rfc8029>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <http://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	Appendix A. Acknowledgments		Appendix A. 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.
	Authors' Addresses		Authors' Addresses
	Greg Mirsky		Greg Mirsky
	ZTE		ZTE
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