< draft-ietf-mpls-bfd-directed-04.txt		draft-ietf-mpls-bfd-directed-05.txt >
	MPLS Working Group G. Mirsky		MPLS Working Group G. Mirsky
	Internet-Draft Ericsson		Internet-Draft ZTE
	Intended status: Standards Track J. Tantsura		Intended status: Standards Track J. Tantsura
	Expires: March 18, 2017 Individual		Expires: August 10, 2017 Individual
	I. Varlashkin		I. Varlashkin
	Google		Google
	M. Chen		M. Chen
	Huawei		Huawei
	September 14, 2016		February 6, 2017
	Bidirectional Forwarding Detection (BFD) Directed Return Path		Bidirectional Forwarding Detection (BFD) Directed Return Path
	draft-ietf-mpls-bfd-directed-04		draft-ietf-mpls-bfd-directed-05
	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 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
	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 March 18, 2017.		This Internet-Draft will expire on August 10, 2017.
	Copyright Notice		Copyright Notice
	Copyright (c) 2016 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
	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. Direct Reverse BFD Path . . . . . . . . . . . . . . . . . . . 3		3. Direct Reverse BFD Path . . . . . . . . . . . . . . . . . . . 3
	3.1. Case of MPLS Data Plane . . . . . . . . . . . . . . . . . 3		3.1. Case of MPLS Data Plane . . . . . . . . . . . . . . . . . 3
	3.1.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . 4		3.1.1. BFD Reverse Path TLV . . . . . . . . . . . . . . . . 3
	3.1.2. Static and RSVP-TE sub-TLVs . . . . . . . . . . . . . 5		3.1.2. Static and RSVP-TE sub-TLVs . . . . . . . . . . . . . 4
	3.1.3. Segment Routing: MPLS Data Plane Case . . . . . . . . 5		3.2. Return Codes . . . . . . . . . . . . . . . . . . . . . . 5
	3.2. Bootstrapping BFD session with BFD Reverse Path over		4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 5
	Segment Routed tunnel . . . . . . . . . . . . . . . . . . 5		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
	3.3. Return Codes . . . . . . . . . . . . . . . . . . . . . . 6		5.1. TLV . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
	4. Use Case Scenario . . . . . . . . . . . . . . . . . . . . . . 6		5.2. Return Codes . . . . . . . . . . . . . . . . . . . . . . 6
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7		6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	5.1. TLV . . . . . . . . . . . . . . . . . . . . . . . . . . . 7		7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
	5.2. Sub-TLV . . . . . . . . . . . . . . . . . . . . . . . . . 7		8. Normative References . . . . . . . . . . . . . . . . . . . . 6
	5.3. Return Codes . . . . . . . . . . . . . . . . . . . . . . 8		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
	8.1. Normative References . . . . . . . . . . . . . . . . . . 9
	8.2. Informative References . . . . . . . . . . . . . . . . . 10
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
	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 and RFC 5884 [RFC5884]
	set rules of using BFD asynchronous mode over IP/MPLS LSPs. These		set rules of using BFD asynchronous mode over IP/MPLS LSPs. These
	standards implicitly assume that the egress BFD peer will use the		standards implicitly assume that the egress BFD peer will use the
	shortest path route regardless of route being used to send BFD		shortest path route regardless of route being used to send BFD
	control packets towards it.		control packets towards it.
	skipping to change at page 4, line 44 ¶		skipping to change at page 4, line 35 ¶
	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 Target FEC sub-TLV
	(already defined, or to be defined in the future) for TLV Types 1,		(already defined, or to be defined in the future) for TLV Types 1,
	16, and 21 of MPLS LSP Ping Parameters registry MAY be used in this		16, and 21 of MPLS LSP Ping Parameters registry MAY be used in this
	field. Exactly one sub-TLV MUST be included in the Reverse Path TLV.		field. Exactly one sub-TLV MUST be included in the Reverse Path TLV.
	If more than one sub-TLV is present in the Reverse Path TLV, then, in		If more than one sub-TLV is present in the Reverse Path TLV, then, in
	order to avoid ambiguity of which of TLVs to use, the egress BFD peer		order to avoid ambiguity of which of TLVs to use, the egress BFD peer
	MUST send Echo Reply with the received Reverse Path TLVs and set the		MUST send Echo Reply with the received Reverse Path TLVs and set the
	Return Code to "Too Many TLVs Detected" Section 3.3.		Return Code to "Too Many TLVs Detected" Section 3.2.
	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 Reverse Path TLV and
	set the Return Code to "Failed to establish the BFD session. The		set the Return Code to "Failed to establish the BFD session. The
	specified reverse path was not found" Section 3.3. The egress BFD		specified reverse path was not found" Section 3.2. The egress BFD
	peer MAY establish the BFD session over IP network as defined in		peer MAY establish the BFD session over IP network as defined in
	[RFC5884].		[RFC5884].
	3.1.2. Static and RSVP-TE sub-TLVs		3.1.2. 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.
	3.1.3. Segment Routing: MPLS Data Plane Case		3.2. Return Codes
	In addition to Static and RSVP-TE, Segment Routing with MPLS data
	plane can be used to set an explicit path. In this case a new sub-
	TLV is defined in this document as presented in Figure 2.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| SegRouting MPLS sub-TLV Type | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Label Entry 1 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Label Entry 2 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	~ ~
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Label Entry N |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 2: Segment Routing MPLS Tunnel sub-TLV
	The Segment Routing Tunnel sub-TLV Type is two octets in length, and
	has a value of TBD2 (to be assigned by IANA as requested in
	Section 5).
	The egress LSR MUST use the Value field as label stack for BFD
	control packets for the BFD session identified by the source IP
	address of the MPLS LSP Ping packet and the value in the BFD
	Discriminator TLV. Label Entries MUST be in network order.
	The Segment Routing Tunnel sub-TLV MAY be used in Reply Path TLV
	defined in [RFC7110]
	3.2. Bootstrapping BFD session with BFD Reverse Path over Segment
	Routed tunnel
	As discussed in [I-D.ietf-mpls-spring-lsp-ping] introduction of
	Segment Routing network domains with an MPLS data plane adds three
	new sub-TLVs that MAY be used with Target FEC TLV. Section 6.1
	addresses use of the new sub-TLVs in Target FEC TLV in LSP ping and
	LSP traceroute. For the case of LSP ping the
	[I-D.ietf-mpls-spring-lsp-ping] states that:
	"Initiator MUST include FEC(s) corresponding to the destination
	segment. "
	"Initiator, i.e. ingress LSR, MAY include FECs corresponding to some
	or all of segments imposed in the label stack by the ingress LSR to
	communicate the segments traversed. "
	When LSP ping is used to bootstrap BFD session this document updates
	the statement and defines that LSP Ping MUST include the FEC
	corresponding to the destination segment and SHOULD NOT include FECs
	corresponding to some or all of other segments imposed by the ingress
	LSR. Operationally such restriction would not cause any problem or
	uncertainty as LSP ping with FECs corresponding to some or all
	segments or traceroute that validate the segment route MAY precede
	the LSP ping that bootstraps the BFD session.
	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 "Too Many TLVs Detected", (TBD3). When more than one Reverse Path		o "Too Many TLVs Detected", (TBD3). When more than one Reverse Path
	TLV found in the received Echo Request by the egress BFD peer, an		TLV found in the received Echo Request by the egress BFD peer, an
	Echo Reply with the return code set to "Too Many TLVs Detected"		Echo Reply with the return code set to "Too Many TLVs Detected"
	MUST be sent to the ingress BFD peer Section 3.1.1.		MUST be sent to the ingress BFD peer Section 3.1.1.
	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 3.1.1.		peer Section 3.1.1.
	4. Use Case Scenario		4. Use Case Scenario
	In the network presented in Figure 3 node A monitors two tunnels to		In the network presented in Figure 2 node A monitors two tunnels to
	node H: A-B-C-D-G-H and A-B-E-F-G-H. To bootstrap a BFD session to		node H: A-B-C-D-G-H and A-B-E-F-G-H. To bootstrap a BFD session to
	monitor the first tunnel, node A MUST include a BFD Discriminator TLV		monitor the first tunnel, node A MUST include a BFD Discriminator TLV
	with Discriminator value (e.g. foobar-1) and MAY include a BFD		with Discriminator value (e.g. foobar-1) and MAY include a BFD
	Reverse Path TLV that references H-G-D-C-B-A tunnel. To bootstrap a		Reverse Path TLV that references H-G-D-C-B-A tunnel. To bootstrap a
	BFD session to monitor the second tunnel, node A MUST include a BFD		BFD session to monitor the second tunnel, node A MUST include a BFD
	Discriminator TLV with a different Discriminator value (e.g. foobar-		Discriminator TLV with a different Discriminator value (e.g. foobar-
	2) [RFC7726] and MAY include a BFD Reverse Path TLV that references		2) [RFC7726] and MAY include a BFD Reverse Path TLV that references
	H-G-F-E-B-A tunnel.		H-G-F-E-B-A tunnel.
	C---------D		C---------D
	| |		| |
	A-------B G-----H		A-------B G-----H
	| |		| |
	E---------F		E---------F
	Figure 3: Use Case for BFD Reverse Path TLV		Figure 2: Use Case for BFD Reverse Path TLV
	If an operator needs node H to monitor a path to node A, e.g.		If an operator needs node H to monitor a path to node A, e.g.
	H-G-D-C-B-A tunnel, then by looking up list of known Reverse Paths it		H-G-D-C-B-A tunnel, then by looking up list of known Reverse Paths it
	MAY find and use the existing BFD session.		MAY find and use the existing BFD session.
	5. IANA Considerations		5. IANA Considerations
	5.1. TLV		5.1. 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
	skipping to change at page 7, line 34 ¶		skipping to change at page 6, line 15 ¶
	sub-TLVs" sub-registry.		sub-TLVs" sub-registry.
	+----------+----------------------+---------------+		+----------+----------------------+---------------+
	| Value | Description | Reference |		| Value | Description | Reference |
	+----------+----------------------+---------------+		+----------+----------------------+---------------+
	| X (TBD1) | BFD Reverse Path TLV | This document |		| X (TBD1) | BFD Reverse Path TLV | This document |
	+----------+----------------------+---------------+		+----------+----------------------+---------------+
	Table 1: New BFD Reverse Type TLV		Table 1: New BFD Reverse Type TLV
	5.2. Sub-TLV		5.2. Return Codes
	The IANA is requested to create new sub-registry for sub-TLV types of
	TLV TBD. All code points in the ranges 0 through 16383 and 32768
	through 49161 in this registry shall be allocated according to the
	"IETF Review" procedure as specified in [RFC5226] . Code points in
	the ranges 16384 through 31743 and 49162 through 64511 in this
	registry shall be allocated according to the "First Come First
	Served" procedure as specified in [RFC5226]. Values in the range
	31744 through 32767 and 64512 through 65534 are for Vendor or Private
	Use, and MUST NOT be allocated. This document defines the following
	new values of new sub-TLV type:
	+-------------+-------------------------------------+---------------+
	| Value | Description | Reference |
	+-------------+-------------------------------------+---------------+
	| 0 | Reserved | This document |
	| X (TBD2) | Segment Routing MPLS Tunnel sub-TLV | This document |
	| 2-31743 | Unassigned | |
	| 31744-32767 | Reserved for Vendor or Private Use | |
	| 32768-64511 | Unassigned | |
	| 64512-65534 | Reserved for Vendor or Private Use | |
	| 65535 | Reserved | This document |
	+-------------+-------------------------------------+---------------+
	Table 2: New Segment Routing Tunnel sub-TLV
	5.3. Return Codes
	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 (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 3: 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], and
	[RFC4379], apply to this document.		[RFC4379], apply to this document.
	7. Acknowledgements		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. References		8. Normative References
	8.1. Normative References
	[I-D.ietf-mpls-spring-lsp-ping]
	Kumar, N., Swallow, G., Pignataro, C., Akiya, N., Kini,
	S., Gredler, H., and M. Chen, "Label Switched Path (LSP)
	Ping/Trace for Segment Routing Networks Using MPLS
	Dataplane", draft-ietf-mpls-spring-lsp-ping-00 (work in
	progress), May 2016.
	[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		[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
	Label Switched (MPLS) Data Plane Failures", RFC 4379,		Label Switched (MPLS) Data Plane Failures", RFC 4379,
	DOI 10.17487/RFC4379, February 2006,		DOI 10.17487/RFC4379, February 2006,
	<http://www.rfc-editor.org/info/rfc4379>.		<http://www.rfc-editor.org/info/rfc4379>.
	skipping to change at page 10, line 16 ¶		skipping to change at page 8, line 5 ¶
	"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>.
	8.2. Informative References
	[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
	IANA Considerations Section in RFCs", BCP 26, RFC 5226,
	DOI 10.17487/RFC5226, May 2008,
	<http://www.rfc-editor.org/info/rfc5226>.
	Authors' Addresses		Authors' Addresses
	Greg Mirsky		Greg Mirsky
	Ericsson		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
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