< draft-ietf-roll-dao-projection-15.txt		draft-ietf-roll-dao-projection-16.txt >
	ROLL P. Thubert, Ed.		ROLL P. Thubert, Ed.
	Internet-Draft Cisco Systems		Internet-Draft Cisco Systems
	Intended status: Standards Track R.A. Jadhav		Updates: 6554 (if approved) R.A. Jadhav
	Expires: 31 May 2021 Huawei Tech		Intended status: Standards Track Huawei Tech
	M. Gillmore		Expires: 19 July 2021 M. Gillmore
	Itron		Itron
	27 November 2020		15 January 2021
	Root initiated routing state in RPL		Root initiated routing state in RPL
	draft-ietf-roll-dao-projection-15		draft-ietf-roll-dao-projection-16
	Abstract		Abstract
	This document extends RFC 6550 and RFC 6553 to enable a RPL Root to		This document extends RFC 6550 and RFC 6553 to enable a RPL Root to
	install and maintain Projected Routes within its DODAG, along a		install and maintain Projected Routes within its DODAG, along a
	selected set of nodes that may or may not include self, for a chosen		selected set of nodes that may or may not include self, for a chosen
	duration. This potentially enables routes that are more optimized or		duration. This potentially enables routes that are more optimized or
	resilient than those obtained with the classical distributed		resilient than those obtained with the classical distributed
	operation of RPL, either in terms of the size of a Routing Header or		operation of RPL, either in terms of the size of a Routing Header or
	in terms of path length, which impacts both the latency and the		in terms of path length, which impacts both the latency and the
	skipping to change at page 1, line 40 ¶		skipping to change at page 1, line 40 ¶
	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 https://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 31 May 2021.		This Internet-Draft will expire on 19 July 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2021 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 (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	and restrictions with respect to this document. Code Components		and restrictions with respect to this document. Code Components
	extracted from this document must include Simplified BSD License text		extracted from this document must include Simplified BSD License text
	as described in Section 4.e of the Trust Legal Provisions and are		as described in Section 4.e of the Trust Legal Provisions and are
	skipping to change at page 2, line 23 ¶		skipping to change at page 2, line 23 ¶
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
	2.1. Requirements Language . . . . . . . . . . . . . . . . . . 5		2.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
	2.2. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 5		2.2. Glossary . . . . . . . . . . . . . . . . . . . . . . . . 5
	2.3. Other Terms . . . . . . . . . . . . . . . . . . . . . . . 6		2.3. Other Terms . . . . . . . . . . . . . . . . . . . . . . . 6
	2.4. References . . . . . . . . . . . . . . . . . . . . . . . 6		2.4. References . . . . . . . . . . . . . . . . . . . . . . . 6
	3. Extending RFC 6550 . . . . . . . . . . . . . . . . . . . . . 6		3. Extending RFC 6550 . . . . . . . . . . . . . . . . . . . . . 6
	3.1. Projected DAO . . . . . . . . . . . . . . . . . . . . . . 6		3.1. Projected DAO . . . . . . . . . . . . . . . . . . . . . . 6
	3.2. Sibling Information Option . . . . . . . . . . . . . . . 8		3.2. Sibling Information Option . . . . . . . . . . . . . . . 8
	3.3. P-DAO Request . . . . . . . . . . . . . . . . . . . . . . 8		3.3. P-DAO Request . . . . . . . . . . . . . . . . . . . . . . 8
	3.4. Extending the RPI . . . . . . . . . . . . . . . . . . . . 8		3.4. Extending the RPI . . . . . . . . . . . . . . . . . . . . 9
	4. Extending RFC 6553 . . . . . . . . . . . . . . . . . . . . . 8		4. Extending RFC 6553 . . . . . . . . . . . . . . . . . . . . . 9
	5. Extending RFC 8138 . . . . . . . . . . . . . . . . . . . . . 9		5. Extending RFC 8138 . . . . . . . . . . . . . . . . . . . . . 10
	6. New RPL Control Messages and Options . . . . . . . . . . . . 10		6. New RPL Control Messages and Options . . . . . . . . . . . . 10
	6.1. New P-DAO Request Control Message . . . . . . . . . . . . 10		6.1. New P-DAO Request Control Message . . . . . . . . . . . . 10
	6.2. New PDR-ACK Control Message . . . . . . . . . . . . . . . 11		6.2. New PDR-ACK Control Message . . . . . . . . . . . . . . . 11
	6.3. Via Information Options . . . . . . . . . . . . . . . . . 12		6.3. Via Information Options . . . . . . . . . . . . . . . . . 13
	6.4. Sibling Information Option . . . . . . . . . . . . . . . 15		6.4. Sibling Information Option . . . . . . . . . . . . . . . 15
	7. Projected DAO . . . . . . . . . . . . . . . . . . . . . . . . 16		7. Projected DAO . . . . . . . . . . . . . . . . . . . . . . . . 17
	7.1. Requesting a Track . . . . . . . . . . . . . . . . . . . 18		7.1. Requesting a Track . . . . . . . . . . . . . . . . . . . 18
	7.2. Identifying a Track . . . . . . . . . . . . . . . . . . . 18		7.2. Identifying a Track . . . . . . . . . . . . . . . . . . . 19
	7.3. Installing a Track . . . . . . . . . . . . . . . . . . . 19		7.3. Installing a Track . . . . . . . . . . . . . . . . . . . 20
	7.4. Forwarding Along a Track . . . . . . . . . . . . . . . . 20		7.3.1. Storing-Mode P-Route . . . . . . . . . . . . . . . . 21
	7.5. Non-Storing Mode Projected Route . . . . . . . . . . . . 21		7.3.2. Non-Storing-Mode P-Route . . . . . . . . . . . . . . 23
	7.6. Storing Mode Projected Route . . . . . . . . . . . . . . 23		7.4. Forwarding Along a Track . . . . . . . . . . . . . . . . 24
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 25		8. Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . 25
	9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25		9. Example Track Signaling . . . . . . . . . . . . . . . . . . . 26
	9.1. New Elective 6LoWPAN Routing Header Type . . . . . . . . 25		9.1. Using Storing-Mode Segments . . . . . . . . . . . . . . . 27
	9.2. New Critical 6LoWPAN Routing Header Type . . . . . . . . 25		9.1.1. Stitched Segments . . . . . . . . . . . . . . . . . . 27
	9.3. New Subregistry For The RPL Option Flags . . . . . . . . 26		9.1.2. External routes . . . . . . . . . . . . . . . . . . . 29
	9.4. New RPL Control Codes . . . . . . . . . . . . . . . . . . 26		9.1.3. Segment Routing . . . . . . . . . . . . . . . . . . . 30
	9.5. New RPL Control Message Options . . . . . . . . . . . . . 27		9.2. Using Non-Storing-Mode joining Tracks . . . . . . . . . . 32
	9.6. SubRegistry for the Projected DAO Request Flags . . . . . 27		9.2.1. Stitched Tracks . . . . . . . . . . . . . . . . . . . 32
	9.7. SubRegistry for the PDR-ACK Flags . . . . . . . . . . . . 28		9.2.2. External routes . . . . . . . . . . . . . . . . . . . 34
	9.8. Subregistry for the PDR-ACK Acceptance Status Values . . 28		9.2.3. Segment Routing . . . . . . . . . . . . . . . . . . . 36
	9.9. Subregistry for the PDR-ACK Rejection Status Values . . . 28		10. Security Considerations . . . . . . . . . . . . . . . . . . . 39
	9.10. SubRegistry for the Via Information Options Flags . . . . 29		11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
	9.11. SubRegistry for the Sibling Information Option Flags . . 29		11.1. New Elective 6LoWPAN Routing Header Type . . . . . . . . 39
	9.12. Error in Projected Route ICMPv6 Code . . . . . . . . . . 30		11.2. New Critical 6LoWPAN Routing Header Type . . . . . . . . 39
	10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 30		11.3. New Subregistry For The RPL Option Flags . . . . . . . . 40
	11. Normative References . . . . . . . . . . . . . . . . . . . . 30		11.4. New RPL Control Codes . . . . . . . . . . . . . . . . . 40
	12. Informative References . . . . . . . . . . . . . . . . . . . 31		11.5. New RPL Control Message Options . . . . . . . . . . . . 41
	Appendix A. Applications . . . . . . . . . . . . . . . . . . . . 32		11.6. SubRegistry for the Projected DAO Request Flags . . . . 41
	A.1. Loose Source Routing . . . . . . . . . . . . . . . . . . 32		11.7. SubRegistry for the PDR-ACK Flags . . . . . . . . . . . 41
	A.2. Transversal Routes . . . . . . . . . . . . . . . . . . . 34		11.8. Subregistry for the PDR-ACK Acceptance Status Values . . 42
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36		11.9. Subregistry for the PDR-ACK Rejection Status Values . . 42
			11.10. SubRegistry for the Via Information Options Flags . . . 43
			11.11. SubRegistry for the Sibling Information Option Flags . . 43
			11.12. New Destination Advertisement Object Flag . . . . . . . 43
			11.13. Error in Projected Route ICMPv6 Code . . . . . . . . . . 44
			12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 44
			13. Normative References . . . . . . . . . . . . . . . . . . . . 44
			14. Informative References . . . . . . . . . . . . . . . . . . . 45
			Appendix A. Applications . . . . . . . . . . . . . . . . . . . . 46
			A.1. Loose Source Routing . . . . . . . . . . . . . . . . . . 47
			A.2. Transversal Routes . . . . . . . . . . . . . . . . . . . 48
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 50
	1. Introduction		1. Introduction
	RPL, the "Routing Protocol for Low Power and Lossy Networks" [RPL]		RPL, the "Routing Protocol for Low Power and Lossy Networks" [RPL]
	(LLNs), is a generic Distance Vector protocol that is well suited for		(LLNs), is a generic Distance Vector protocol that is well suited for
	application in a variety of low energy Internet of Things (IoT)		application in a variety of low energy Internet of Things (IoT)
	networks. RPL forms Destination Oriented Directed Acyclic Graphs		networks. RPL forms Destination Oriented Directed Acyclic Graphs
	(DODAGs) in which the Root often acts as the Border Router to connect		(DODAGs) in which the Root often acts as the Border Router to connect
	the RPL domain to the Internet. The Root is responsible to select		the RPL domain to the Internet. The Root is responsible to select
	the RPL Instance that is used to forward a packet coming from the		the RPL Instance that is used to forward a packet coming from the
	skipping to change at page 5, line 35 ¶		skipping to change at page 5, line 45 ¶
	2.2. Glossary		2.2. Glossary
	This document often uses the following acronyms:		This document often uses the following acronyms:
	CMO: Control Message Option		CMO: Control Message Option
	DAO: Destination Advertisement Object		DAO: Destination Advertisement Object
	DAG: Directed Acyclic Graph		DAG: Directed Acyclic Graph
	DODAG: Destination-Oriented Directed Acyclic Graph; A DAG with only		DODAG: Destination-Oriented Directed Acyclic Graph; A DAG with only
	one vertex (i.e., node) that has no outgoing edge (i.e., link)		one vertex (i.e., node) that has no outgoing edge (i.e., link)
	LLN: Low-Power and Lossy Network		LLN: Low-Power and Lossy Network
	NMPR: Non-Storing Mode Projected Route
	MOP: RPL Mode of Operation		MOP: RPL Mode of Operation
	P-DAO: Projected DAO		P-DAO: Projected DAO
			P-Route: Projected Route
	PDR: P-DAO Request		PDR: P-DAO Request
	RAN: RPL-Aware Node (either a RPL Router or a RPL-Aware Leaf)		RAN: RPL-Aware Node (either a RPL Router or a RPL-Aware Leaf)
	RAL: RPL-Aware Leaf		RAL: RPL-Aware Leaf
	RH: Routing Header		RH: Routing Header
	RPI: RPL Packet Information		RPI: RPL Packet Information
	RTO: RPL Target Option		RTO: RPL Target Option
	RUL: RPL-Unaware Leaf		RUL: RPL-Unaware Leaf
	SIO: RPL Sibling Information Option		SIO: RPL Sibling Information Option
	SR-VIO: A Source-Routed Via Information Option, used in Non-Storing		SR-VIO: A Source-Routed Via Information Option, used in Non-Storing-
	Mode P-DAO messages.		Mode P-DAO messages.
	SMPR: Storing Mode Projected Route
	TIO: RPL Transit Information Option		TIO: RPL Transit Information Option
	SF-VIO: A Via Information Option, used in Storing Mode P-DAO		SF-VIO: A Via Information Option, used in Storing-Mode P-DAO
	messages.		messages.
	VIO: A Via Information Option; it can be a SF-VIO or an SR-VIO.		VIO: A Via Information Option; it can be a SF-VIO or an SR-VIO.
	2.3. Other Terms		2.3. Other Terms
	Projected Route: A RPL Projected Route is a RPL route that is		Projected Route: A RPL Projected Route is a RPL route that is
	computed remotely by a PCE, and installed and maintained by a RPL		computed remotely by a PCE, and installed and maintained by a RPL
	Root on behalf of the PCE.		Root on behalf of the PCE.
	Projected DAO: A DAO message used to install a Projected Route.		Projected DAO: A DAO message used to install a Projected Route.
	Track: A DODAG that provides a complex path from or to a Root that		Track: A DODAG that provides a complex path from or to a Root that
	skipping to change at page 6, line 45 ¶		skipping to change at page 7, line 11 ¶
	therein. This specification enables to combine one or more Projected		therein. This specification enables to combine one or more Projected
	Routes into a DODAG called a Track, that is traversed to reach the		Routes into a DODAG called a Track, that is traversed to reach the
	Targets.		Targets.
	The Track is assimilated with the DODAG formed for a Local RPL		The Track is assimilated with the DODAG formed for a Local RPL
	Instance. The local RPLInstanceID of the Track is called the		Instance. The local RPLInstanceID of the Track is called the
	TrackID, more in Section 7.2. A P-DAO message for a Track signals		TrackID, more in Section 7.2. A P-DAO message for a Track signals
	the TrackID in the RPLInstanceID field. The Track Ingress is		the TrackID in the RPLInstanceID field. The Track Ingress is
	signaled in the DODAGID field of the Projected DAO Base Object; that		signaled in the DODAGID field of the Projected DAO Base Object; that
	field is elided in the case of the main RPL Instance. The Track		field is elided in the case of the main RPL Instance. The Track
	Ingress is the Root of the Track, as shown in Figure 1. .		Ingress is the Root of the Track, as shown in Figure 1.
			This specification defines the new "Projected DAO" (P) flag. The 'P'
			flag is encoded in bit position 2 (to be confirmed by IANA) of the
			Flags field in the DAO Base Object. The Root MUST set it to 1 in a
			Projected DAO message. Otherwise it MUST be set to 0. It is set to
			0 in legacy implementations as specified respectively in Sections
			20.11 and 6.4 of [RPL]. .
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| TrackID |K|D| Flags | Reserved | DAOSequence |		| TrackID |K|D|P| Flags | Reserved | DAOSequence |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	+ +		+ +
	| |		| |
	+ IPv6 Address of the Track Ingress +		+ IPv6 Address of the Track Ingress +
	| |		| |
	+ +		+ +
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Option(s)...		| Option(s)...
	+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+
	Figure 1: Projected DAO Format for a Track		Figure 1: Projected DAO Base Object
			New fields:
			TrackID: In the case of a P-DAO, the RPLInstanceID field is called
			TrackID. This is a naming convenience but does not change the
			semantics and format of the RPLInstanceID that is used as TrackID.
			P: 1-bit flag (position to be confirmed by IANA).
			The 'P' flag is set to 1 by the Root to signal a Projected DAO,
			and it is set to 0 otherwise.
	In RPL Non-Storing Mode, the TIO and RTO are combined in a DAO		In RPL Non-Storing Mode, the TIO and RTO are combined in a DAO
	message to inform the DODAG Root of all the edges in the DODAG, which		message to inform the DODAG Root of all the edges in the DODAG, which
	are formed by the directed parent-child relationships. Options may		are formed by the directed parent-child relationships. Options may
	be factorized; multiple RTOs may be present to signal a collection of		be factorized; multiple RTOs may be present to signal a collection of
	children that can be reached via the parent(s) indicated in the		children that can be reached via the parent(s) indicated in the
	TIO(s) that follows the RTOs. This specification generalizes the		TIO(s) that follows the RTOs. This specification generalizes the
	case of a parent that can be used to reach a child with that of a		case of a parent that can be used to reach a child with that of a
	whole Track through which both children and siblings of the Track		whole Track through which both children and siblings of the Track
	Egress are reachable.		Egress are reachable.
	New CMOs called the Via Information Options (VIO) are introduced for		New CMOs called the Via Information Options (VIO) are introduced for
	use in P-DAO messages as a multihop alternative to the TIO. One VIO		use in P-DAO messages as a multihop alternative to the TIO. One VIO
	is the Stateful Via Information Option (SF-VIO); the SF-VIO installs		is the Stateful VIO(SF-VIO); the SF-VIO installs Storing-Mode
	Storing Mode Projected Route (SMPR) along a strict segment. The		Projected Route along a strict segment. The other is the Source-
	other is the Source-Routed SF-VIO (SR-VIO); the SR-VIO installs a		Routed VIO (SR-VIO); the SR-VIO installs a Non-Storing-Mode Projected
	Non-Storing Mode Projected Route (NMPR) at the Track Ingress, which		Route at the Track Ingress, which uses that state to encapsulate a
	uses that state to encapsulate a packet with a Routing Header (RH) to		packet with a Routing Header (RH) to the Track Egress.
	the Track Egress.
	Like in a DAO message, the RTOs can be factorized in a P-DAO, but the		Like in a DAO message, the RTOs can be factorized in a P-DAO, but the
	Via Options cannot. A P-DAO contains one or more RTOs that indicate		Via Information Options cannot. A P-DAO contains one or more RTOs
	the destinations that can be reached via the Track, and exactly one		that indicate the destinations that can be reached via the Track, and
	Via Option that signals a sequence of nodes. In Non-Storing Mode,		exactly one VIOthat signals a sequence of nodes. In Non-Storing
	the Root sends the P-DAO to the Track Ingress where the source-		Mode, the Root sends the P-DAO to the Track Ingress where the source-
	routing state is stored. In Storing Mode, the P-DAO is sent to the		routing state is stored. In Storing Mode, the P-DAO is sent to the
	Track Egress and forwarded along the Segment in the reverse		Track Egress and forwarded along the Segment in the reverse
	direction, installing a Storing Mode state to the Track Egress at		direction, installing a Storing Mode state to the Track Egress at
	each hop. In both cases the Track Ingress is the owner of the Track,		each hop. In both cases the Track Ingress is the owner of the Track,
	and it generates the P-DAO-ACK when the installation is successful.		and it generates the P-DAO-ACK when the installation is successful.
	3.2. Sibling Information Option		3.2. Sibling Information Option
	This specification adds another CMO called the Sibling Information		This specification adds another CMO called the Sibling Information
	Option (SIO) that is used by a RPL Aware Node (RAN) to advertise a		Option (SIO) that is used by a RPL Aware Node (RAN) to advertise a
	skipping to change at page 12, line 18 ¶		skipping to change at page 12, line 46 ¶
	+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+
	Figure 6: PDR-ACK status Format		Figure 6: PDR-ACK status Format
	E: 1-bit flag. Set to indicate a rejection. When not set, the		E: 1-bit flag. Set to indicate a rejection. When not set, the
	value of 0 indicates Success/Unqualified acceptance and other		value of 0 indicates Success/Unqualified acceptance and other
	values indicate "not an outright rejection".		values indicate "not an outright rejection".
	R: 1-bit flag. Reserved, MUST be set to 0 by the sender and		R: 1-bit flag. Reserved, MUST be set to 0 by the sender and
	ignored by the receiver.		ignored by the receiver.
	Status Value: 6-bit unsigned integer. Values depending on the		Status Value: 6-bit unsigned integer. Values depending on the
	setting of the 'E' flag, see Table 7 and Table 8.		setting of the 'E' flag, see Table 27 and Table 28.
	Reserved: The Reserved field MUST initialized to zero by the sender		Reserved: The Reserved field MUST initialized to zero by the sender
	and MUST be ignored by the receiver		and MUST be ignored by the receiver
	6.3. Via Information Options		6.3. Via Information Options
	An Via Option signals the ordered list of IPv6 Via Addresses that		An VIOsignals the ordered list of IPv6 Via Addresses that constitutes
	constitutes the hops of either a Serial Track or a Segment of a more		the hops of either a Serial Track or a Segment of a more Complex
	Complex Track. An Via Option MUST contain at least one Via Address,		Track. An VIOMUST contain at least one Via Address, and a Via
	and a Via Address MUST NOT be present more than once, otherwise the		Address MUST NOT be present more than once, otherwise the VIOMUST be
	Via Option MUST be ignored. The format of the Via Options is as		ignored. The format of the Via Information Options is as follows:
	follows:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Option Length | Flags | SegmentID |		| Type | Option Length | Flags | SegmentID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|Segm. Sequence | Seg. Lifetime | SRH-6LoRH header |		|Segm. Sequence | Seg. Lifetime | SRH-6LoRH header |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	+ +		+ +
	skipping to change at page 13, line 33 ¶		skipping to change at page 13, line 41 ¶
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| |		| |
	+ +		+ +
	. .		. .
	. Via Address n .		. Via Address n .
	. .		. .
	+ +		+ +
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 7: Via Information Option format (uncompressed form)		Figure 7: VIOformat (uncompressed form)
	Option Type: 0x0B for SF-VIO, 0x0C for SR-VIO (to be confirmed by		Option Type: 0x0B for SF-VIO, 0x0C for SR-VIO (to be confirmed by
	IANA)		IANA)
	Option Length: In bytes; variable, depending on the number of Via		Option Length: In bytes; variable, depending on the number of Via
	Addresses and the compression.		Addresses and the compression.
	SegmentID: 8-bit field that identifies a Segment within a Track or		SegmentID: 8-bit field that identifies a Segment within a Track or
	the main DODAG as indicated by the TrackID field. The value of 0		the main DODAG as indicated by the TrackID field. The value of 0
	is used to signal a Serial Track, i.e., made of a single segment.		is used to signal a Serial Track, i.e., made of a single segment.
	Segment Sequence: 8-bit unsigned integer. The Segment Sequence		Segment Sequence: 8-bit unsigned integer. The Segment Sequence
	obeys the operation in section 7.2 of [RPL] and the lollipop		obeys the operation in section 7.2 of [RPL] and the lollipop
	starts at 255.		starts at 255.
	When the Root of the DODAG needs to refresh or update a Segment in		When the Root of the DODAG needs to refresh or update a Segment in
	a Track, it increments the Segment Sequence individually for that		a Track, it increments the Segment Sequence individually for that
	Segment.		Segment.
	The Segment information indicated in the Via Option deprecates any		The Segment information indicated in the VIOdeprecates any state
	state for the Segment indicated by the SegmentID within the		for the Segment indicated by the SegmentID within the indicated
	indicated Track and sets up the new information.		Track and sets up the new information.
	An Via Option with a Segment Sequence that is not as fresh as the		An VIOwith a Segment Sequence that is not as fresh as the current
	current one is ignored.		one is ignored.
	A VIO for a given DODAGID with the same (TrackID, SegmentID,		A VIO for a given DODAGID with the same (TrackID, SegmentID,
	Segment Sequence) indicates a retry; it MUST NOT change the		Segment Sequence) indicates a retry; it MUST NOT change the
	Segment and MUST be propagated or answered as the first copy.		Segment and MUST be propagated or answered as the first copy.
	Segment Lifetime: 8-bit unsigned integer. The length of time in		Segment Lifetime: 8-bit unsigned integer. The length of time in
	Lifetime Units (obtained from the Configuration option) that the		Lifetime Units (obtained from the Configuration option) that the
	Segment is usable.		Segment is usable.
	The period starts when a new Segment Sequence is seen. The value		The period starts when a new Segment Sequence is seen. The value
	of 255 (0xFF) represents infinity. The value of zero (0x00)		of 255 (0xFF) represents infinity. The value of zero (0x00)
	indicates a loss of reachability.		indicates a loss of reachability.
	A P-DAO message that contains a Via Information option with a		A P-DAO message that contains a VIOwith a Segment Lifetime of zero
	Segment Lifetime of zero is referred as a No-Path P-DAO in this		is referred as a No-Path P-DAO in this document.
	document.
	SRH-6LoRH header: The first 2 bytes of the (first) SRH-6LoRH as		SRH-6LoRH header: The first 2 bytes of the (first) SRH-6LoRH as
	shown in Figure 6 of [RFC8138]. A 6LoRH Type of 4 means that the		shown in Figure 6 of [RFC8138]. A 6LoRH Type of 4 means that the
	VIA Addresses are provided in full with no compression.		VIA Addresses are provided in full with no compression.
	Via Address: An IPv6 addresse along the Segment.		Via Address: An IPv6 addresse along the Segment.
	In a SF-VIO, the list is a strict path between direct neighbors,		In a SF-VIO, the list is a strict path between direct neighbors,
	from the segment ingress to egress, both included. In an SR-VIO,		from the segment ingress to egress, both included. In an SR-VIO,
	the list starts at the first hop and ends at a Track Egress. The		the list starts at the first hop and ends at a Track Egress. The
	list in an SR-VIO may be loose, provided that each listed node has		list in an SR-VIO may be loose, provided that each listed node has
	a path to the next listed node, e.g., via a segment or another		a path to the next listed node, e.g., via a segment or another
	Track.		Track.
	In the case of a SF-VIO, or if [RFC8138] is not used in the data		In the case of a SF-VIO, or if [RFC8138] is not used in the data
	packets, then the Root MUST use only one SRH-6LoRH per Via Option,		packets, then the Root MUST use only one SRH-6LoRH per Via
	and the compression is the same for all the addresses, as shown in		Information Option, and the compression is the same for all the
	Figure 7.		addresses, as shown in Figure 7.
	In case of an SR-VIO, and if [RFC8138] is in use in the main		In case of an SR-VIO, and if [RFC8138] is in use in the main
	DODAG, then the Root SHOULD optimize the size of the SR-VIO; more		DODAG, then the Root SHOULD optimize the size of the SR-VIO; more
	than one SRH-6LoRH may be present, e.g., if the compression level		than one SRH-6LoRH may be present, e.g., if the compression level
	changes inside the Segment and different SRH-6LoRH Types are		changes inside the Segment and different SRH-6LoRH Types are
	required. The content of the SR-VIO starting at the first SRH-		required. The content of the SR-VIO starting at the first SRH-
	6LoRH header is thus verbatim the one that the Track Ingress		6LoRH header is thus verbatim the one that the Track Ingress
	places in the packet encapsulation to reach the Track Ingress.		places in the packet encapsulation to reach the Track Ingress.
	6.4. Sibling Information Option		6.4. Sibling Information Option
	skipping to change at page 16, line 51 ¶		skipping to change at page 17, line 12 ¶
	that case the DAG Metric Container provides additional metrics for		that case the DAG Metric Container provides additional metrics for
	the hop from the Sibling to this node.		the hop from the Sibling to this node.
	7. Projected DAO		7. Projected DAO
	This draft adds a capability to RPL whereby the Root of a main DODAG		This draft adds a capability to RPL whereby the Root of a main DODAG
	installs a Track as a collection of Projected Routes, using a		installs a Track as a collection of Projected Routes, using a
	Projected-DAO (P-DAO) message to maintain each individual route. The		Projected-DAO (P-DAO) message to maintain each individual route. The
	P-DAO signals a collection of Targets in the RPL Target Option(s)		P-DAO signals a collection of Targets in the RPL Target Option(s)
	(RTO). Those Targets can be reached via a sequence of routers		(RTO). Those Targets can be reached via a sequence of routers
	indicated in a Via Information Option (VIO). A P-DAO message MUST		indicated in a VIO(VIO). A P-DAO message MUST contain exactly one
	contain exactly one VIO, which is either a SF-VIO or an SR-VIO, and		VIO, which is either a SF-VIO or an SR-VIO, and MUST follow one or
	MUST follow one or more RTOs. There can be at most one such sequence		more RTOs. There can be at most one such sequence of RTO(s) and an
	of RTO(s) and an Via Option. A track is indentified by a tupple		Via Information Option. A track is indentified by a tupple DODAGID,
	DODAGID, TrackID and each route within a Track is indexed by a		TrackID and each route within a Track is indexed by a SegmentID.
	SegmentID.
	A P-DAO MUST be sent from the address of the Root that serves as		A P-DAO MUST be sent from the address of the Root that serves as
	DODAGID for the main DODAG. It MUST be sent to a GUA or a ULA of		DODAGID for the main DODAG. It MUST be sent to a GUA or a ULA of
	either the ingress or the egress of the Segment, more below. If the		either the ingress or the egress of the Segment, more below. If the
	'K' Flag is present in the P-DAO, and unless the P-DAO does not reach		'K' Flag is present in the P-DAO, and unless the P-DAO does not reach
	it, the ingress of the Segment is the node that acknowledges the		it, the ingress of the Segment is the node that acknowledges the
	message, using a DAO-ACK that MUST be sent back to the address that		message, using a DAO-ACK that MUST be sent back to the address that
	serves as DODAGID for the main DODAG.		serves as DODAGID for the main DODAG.
	Like a classical DAO message, a P-DAO causes a change of state only		Like a classical DAO message, a P-DAO causes a change of state only
	if it is "new" per section 9.2.2. "Generation of DAO Messages" of		if it is "new" per section 9.2.2. "Generation of DAO Messages" of
	the RPL specification [RPL]; this is determined using the Segment		the RPL specification [RPL]; this is determined using the Segment
	Sequence information from the Via Option as opposed to the Path		Sequence information from the VIOas opposed to the Path Sequence from
	Sequence from a TIO. Also, a Segment Lifetime of 0 in an Via Option		a TIO. Also, a Segment Lifetime of 0 in an VIOindicates that the
	indicates that the projected route associated to the Segment is to be		projected route associated to the Segment is to be removed.
	removed.
	There are two kinds of operation for the Projected Routes, the		There are two kinds of operation for the Projected Routes, the
	Storing Mode and the Non-Storing Mode.		Storing Mode and the Non-Storing Mode.
	* The Non-Storing Mode is discussed in Section 7.5. A Non-Storing		* The Non-Storing Mode is discussed in Section 7.3.2. A Non-Storing
	Mode P-DAO carries an SR-VIO with the loose list of Via Addresses		Mode P-DAO carries an SR-VIO with the loose list of Via Addresses
	that forms a source-routed Segment to the Track Egress. The		that forms a source-routed Segment to the Track Egress. The
	recipient of the P-DAO is the Track Ingress; it MUST install a		recipient of the P-DAO is the Track Ingress; it MUST install a
	source-routed state to the Track Egress and reply to the Root		source-routed state to the Track Egress and reply to the Root
	directly using a DAO-ACK message if requested to.		directly using a DAO-ACK message if requested to.
	* The Storing Mode is discussed in Section 7.6. A Storing Mode		* The Storing Mode is discussed in Section 7.3.1. A Storing Mode
	P-DAO carries a SF-VIO with the strict list of Via Addresses from		P-DAO carries a SF-VIO with the strict list of Via Addresses from
	the ingress to the egress of the Segment in the data path order.		the ingress to the egress of the Segment in the data path order.
	The routers listed in the Via Addresses, except the egress, MUST		The routers listed in the Via Addresses, except the egress, MUST
	install a routing state to the Target(s) via the next Via Address		install a routing state to the Target(s) via the next Via Address
	in the SF-VIO. In normal operations, the P-DAO is propagated		in the SF-VIO. In normal operations, the P-DAO is propagated
	along the chain of Via Routers from the egress router of the path		along the chain of Via Routers from the egress router of the path
	till the ingress one, which confirms the installation to the Root		till the ingress one, which confirms the installation to the Root
	with a DAO-ACK message.		with a DAO-ACK message.
	In case of a forwarding error along a Projected Route, an ICMP error		In case of a forwarding error along a Projected Route, an ICMP error
	is sent to the Root with a new Code "Error in Projected Route" (See		is sent to the Root with a new Code "Error in Projected Route" (See
	Section 9.12). The Root can then modify or remove the Projected		Section 11.13). The Root can then modify or remove the Projected
	Route. The "Error in Projected Route" message has the same format as		Route. The "Error in Projected Route" message has the same format as
	the "Destination Unreachable Message", as specified in RFC 4443		the "Destination Unreachable Message", as specified in RFC 4443
	[RFC4443].		[RFC4443].
	The portion of the invoking packet that is sent back in the ICMP		The portion of the invoking packet that is sent back in the ICMP
	message SHOULD record at least up to the RH if one is present, and		message SHOULD record at least up to the RH if one is present, and
	this hop of the RH SHOULD be consumed by this node so that the		this hop of the RH SHOULD be consumed by this node so that the
	destination in the IPv6 header is the next hop that this node could		destination in the IPv6 header is the next hop that this node could
	not reach. if a 6LoWPAN Routing Header (6LoRH) [RFC8138] is used to		not reach. if a 6LoWPAN Routing Header (6LoRH) [RFC8138] is used to
	carry the IPv6 routing information in the outer header then that		carry the IPv6 routing information in the outer header then that
	whole 6LoRH information SHOULD be present in the ICMP message.		whole 6LoRH information SHOULD be present in the ICMP message.
	The sender and exact operation depend on the Mode and is described in		The sender and exact operation depend on the Mode and is described in
	Section 7.5 and Section 7.6 respectively.		Section 7.3.2 and Section 7.3.1 respectively.
	7.1. Requesting a Track		7.1. Requesting a Track
	A Node is free to ask the Root for a new Track at any time. This is		A Node is free to ask the Root for a new Track at any time. This is
	done with a PDR message, that indicates in the Requested Lifetime		done with a PDR message, that indicates in the Requested Lifetime
	field the duration for which the Track should be established. Upon a		field the duration for which the Track should be established. Upon a
	PDR, the Root MAY install the necessary Segments, in which case it		PDR, the Root MAY install the necessary Segments, in which case it
	answers with a PDR-ACK indicating the granted Track Lifetime. All		answers with a PDR-ACK indicating the granted Track Lifetime. All
	the Segments MUST be of a same mode, either Storing or Non-Storing.		the Segments MUST be of a same mode, either Storing or Non-Storing.
	All the Segments MUST be created with the same TrackID and the same		All the Segments MUST be created with the same TrackID and the same
	skipping to change at page 19, line 9 ¶		skipping to change at page 19, line 17 ¶
	RPL defines the concept of an Instance to signal an individual		RPL defines the concept of an Instance to signal an individual
	routing topology but does not have a concept of an administrative		routing topology but does not have a concept of an administrative
	distance, which exists in certain proprietary implementations to sort		distance, which exists in certain proprietary implementations to sort
	out conflicts between multiple sources of routing information within		out conflicts between multiple sources of routing information within
	one routing topology.		one routing topology.
	This draft leverages the RPL Instance model as follows:		This draft leverages the RPL Instance model as follows:
	* The Root MAY use P-DAO messages to add better routes in the main		* The Root MAY use P-DAO messages to add better routes in the main
	(Global) Instance in conformance with the routing objectives in		(Global) Instance in conformance with the routing objectives in
	that Instance. To achieve this, the Root MAY install an SMPR		that Instance. To achieve this, the Root MAY install an Storing-
	along a path down the main Non-Storing Mode DODAG. This enables a		Mode P-Route along a path down the main Non-Storing Mode DODAG.
	loose source routing and reduces the size of the Routing Header,		This enables a loose source routing and reduces the size of the
	see Appendix A.1.		Routing Header, see Appendix A.1.
	When adding an SMPR to the main RPL Instance, the Root MUST set		When adding an Storing-Mode P-Route to the main RPL Instance, the
	the RPLInstanceID field of the P-DAO message (see section 6.4.1.		Root MUST set the RPLInstanceID field of the P-DAO message (see
	of [RPL]) to the RPLInstanceID of the main DODAG, and MUST NOT use		section 6.4.1. of [RPL]) to the RPLInstanceID of the main DODAG,
	the DODAGID field. A Projected Route provides a longer match to		and MUST NOT use the DODAGID field. A Projected Route provides a
	the Target Address than the default route via the Root, so it is		longer match to the Target Address than the default route via the
	preferred.		Root, so it is preferred.
	Once the Projected Route is installed, the intermediate nodes		Once the Projected Route is installed, the intermediate nodes
	listed in the SF-VIO after first one (i.e. The ingress) can be		listed in the SF-VIO after first one (i.e. The ingress) can be
	elided from the RH in packets sent along the Segment signaled in		elided from the RH in packets sent along the Segment signaled in
	the P-DAO. The resulting loose source routing header indicates		the P-DAO. The resulting loose source routing header indicates
	(one of) the Target(s) as the next entry after the ingress.		(one of) the Target(s) as the next entry after the ingress.
	* The Root MAY also use P-DAO messages to install a specific (say,		* The Root MAY also use P-DAO messages to install a specific (say,
	Traffic Engineered) path as a Serial or as a Complex Track, to a		Traffic Engineered) path as a Serial or as a Complex Track, to a
	particular endpoint that is the Track Egress. In that case, the		particular endpoint that is the Track Egress. In that case, the
	skipping to change at page 19, line 43 ¶		skipping to change at page 20, line 7 ¶
	IPv6 Address (GUA) or Unique-Local Address (ULA) of the Track		IPv6 Address (GUA) or Unique-Local Address (ULA) of the Track
	Ingress that serves as DODAGID for the Track. This way, a Track		Ingress that serves as DODAGID for the Track. This way, a Track
	is uniquely identified by the tuple (DODAGID, TrackID) where the		is uniquely identified by the tuple (DODAGID, TrackID) where the
	TrackID is always represented with the 'D' flag set to 0.		TrackID is always represented with the 'D' flag set to 0.
	The Track Egress Address and the TrackID MUST be signaled in the		The Track Egress Address and the TrackID MUST be signaled in the
	P-DAO message as shown in Figure 1.		P-DAO message as shown in Figure 1.
	7.3. Installing a Track		7.3. Installing a Track
	A Storing Mode P-DAO contains an SF-VIO that signals the strict		A Storing-Mode P-DAO contains an SF-VIO that signals the strict
	sequence of consecutive nodes to form a segment between a segment		sequence of consecutive nodes to form a segment between a segment
	ingress and a segment egress (both included). It installs a route of		ingress and a segment egress (both included). It installs a route of
	a higher precedence along the segment towards the Targets indicated		a higher precedence along the segment towards the Targets indicated
	in the Target Options. The segment is included in a DODAG indicated		in the Target Options. The segment is included in a DODAG indicated
	by the P-DAO Base Object, that may be the one formed by the main RPL		by the P-DAO Base Object, that may be the one formed by the main RPL
	Instance, or a Track associated with a local RPL Instance. A Track		Instance, or a Track associated with a local RPL Instance. A Track
	Egress is signaled as a Target in the P-DAO, and as the last entry is		Egress is signaled as a Target in the P-DAO, and as the last entry is
	an SF-VIO of a last segment towards that Egress.		an SF-VIO of a last segment towards that Egress.
	A Non-Storing Mode P-DAO signals a strict or loose sequence of nodes		A Non-Storing-Mode P-DAO signals a strict or loose sequence of nodes
	between the Track Ingress (excluded) and a Track Egress (included).		between the Track Ingress (excluded) and a Track Egress (included).
	It installs a source-routed path of a higher precedence within the		It installs a source-routed path of a higher precedence within the
	Track indicated by the P-DAO Base Object, towards the Targets		Track indicated by the P-DAO Base Object, towards the Targets
	indicated in the Target Options. The source-routed path requires a		indicated in the Target Options. The source-routed path requires a
	Source-Routing header which implies an encapsulation to add the SRH		Source-Routing header which implies an encapsulation to add the SRH
	to an existing packet.		to an existing packet.
	The next entry in the sequence must be either a neighbor of the		The next entry in the sequence must be either a neighbor of the
	previous entry, or reachable as a Target via another Projected Route,		previous entry, or reachable as a Target via another Projected Route,
	either Storing or Non-Storing. If it is reachable over a Storing		either Storing or Non-Storing. If it is reachable over a Storing
	skipping to change at page 20, line 39 ¶		skipping to change at page 21, line 5 ¶
	A Complex Track can be installed as a collection of Projected Routes		A Complex Track can be installed as a collection of Projected Routes
	with the same DODAGID and Track ID. The Ingress of a Non-Storing		with the same DODAGID and Track ID. The Ingress of a Non-Storing
	Mode Projected Route must be the owner of the DODAGID. The Ingress		Mode Projected Route must be the owner of the DODAGID. The Ingress
	of a Storing Mode Projected Route must be either the owner of the		of a Storing Mode Projected Route must be either the owner of the
	DODAGID, or the egress of a preceding Storing Mode Projected Route in		DODAGID, or the egress of a preceding Storing Mode Projected Route in
	the same Track. In the latter case, the Targets of the Projected		the same Track. In the latter case, the Targets of the Projected
	Route must be Targets of the preceding Projected Route to ensure that		Route must be Targets of the preceding Projected Route to ensure that
	they are visible from the track Ingress.		they are visible from the track Ingress.
	7.4. Forwarding Along a Track		7.3.1. Storing-Mode P-Route
	This draft leverages the RPL Forwarding model follows:		Profile 1 extends RPL opertation in a Non-Storing Mode network with
			Storing-Mode Projected Routes that install segments along the main
			DODAG and enable to loose source routing between the Root and the
			targets.
	* In the data packets, the Track DODAGID and the TrackID MUST be		As illustrated in Figure 9, a P-DAO that carries a SF-VIO enables the
	respectively signaled as the IPv6 Source Address and the		Root to install a stateful route towards a collection of Targets
	RPLInstanceID field of the RPI that MUST be placed in the outer		along a Segment between a Track Ingress and a Track Egress.
	chain of IPv6 Headers.
	The RPI carries a local RPLInstanceID called the TrackID, which,		------+---------
	in association with the DODAGID, indicates the Track along which		| Internet
	the packet is forwarded.		|
			+-----+
			| | Border Router
			| | (RPL Root)
			+-----+ | ^ |
			| | DAO | ACK |
			o o o o | | |
			o o o o o o o o o | ^ | Projected .
			o o o o o o o o o o | | DAO | Route .
			o o o o o o o o o | ^ | .
			o o o o o o o o v | DAO v .
			o o LLN o o o |
			o o o o o Loose Source Route Path |
			o o o o From Root To Destination v
	The 'D' flag in the RPLInstanceID MUST be set to 0 to indicate		Figure 9: Projecting a route
	that the source address in the IPv6 header is set ot the DODAGID,
	more in Section 7.4.
	* This draft conforms the principles of [USEofRPLinfo] with regards		In order to install the relevant routing state along the Segment ,
	to packet forwarding and encapsulation along a Track.		the Root sends a unicast P-DAO message to the Track Egress router of
			the routing Segment that is being installed. The P-DAO message
			contains a SF-VIO with the direct sequence of Via Addresses. The SF-
			VIO follows one or more RTOs indicating the Targets to which the
			Track leads. The SF-VIO contains a Segment Lifetime for which the
			state is to be maintained.
	- In that case, the Track is the DODAG, the Track Ingress is the		The Root sends the P-DAO directly to the egress node of the Segment.
	Root, and the Track Egress is a RAL, and neighbors of the Track		In that P-DAO, the destination IP address matches the last Via
	Egress that can be reached via the Track are RULs. The		Address in the SF-VIO. This is how the egress recognizes its role.
	encapsulation rules in [USEofRPLinfo] apply.		In a similar fashion, the ingress node recognizes its role as it
			matches first Via Address in the SF-VIO.
	- If the Track Ingress is the originator of the packet and the		The Egress node of the Segment is the only node in the path that does
	Track Egress is the destination of the packet, there is no need		not install a route in response to the P-DAO; it is expected to be
	for an encapsulation.		already able to route to the Target(s) on its own. If one of the
			Targets is not known, the node MUST answer to the Root with a
			negative DAO-ACK listing the Target(s) that could not be located
			(suggested status 10 to be confirmed by IANA).
	- So the Track Ingress must encapsulate the traffic that it did		If the egress node can reach all the Targets, then it forwards the
	not originate, and add an RPI in any fashion.		P-DAO with unchanged content to its loose predecessor in the Segment
			as indicated in the list of Via Information options, and recursively
			the message is propagated unchanged along the sequence of routers
			indicated in the P-DAO, but in the reverse order, from egress to
			ingress.
	A packet that is being routed over the RPL Instance associated to		The address of the predecessor to be used as destination of the
	a first Non-Storing Mode Track MAY be placed (encapsulated) in a		propagated DAO message is found in the Via Address the precedes the
	second Track to cover one loose hop of the first Track. On the		one that contain the address of the propagating node, which is used
	other hand, a Storing Mode Track must be strict and a packet that		as source of the message.
	it placed in a Storing Mode Track MUST follow that Track till the
	Track Egress.
	When a Track Egress extracts a packet from a Track (decapsulates		Upon receiving a propagated DAO, all except the Egress Router MUST
	the packet), the Destination of the inner packet MUST be either		install a route towards the DAO Target(s) via their successor in the
	this node or a direct neighbor, or a Target of another Segment of		SF-VIO. The router MAY install additional routes towards the VIA
	the same Track for which this node is ingress, otherwise the		Addresses that are the SF-VIO after the next one, if any, but in case
	packet MUST be dropped.		of a conflict or a lack of resource, the route(s) to the Target(s)
			have precedence.
	All properties of a Track operations are inherited form the main RPL		If a router cannot reach its predecessor in the SF-VIO, the router
	Instance that is used to install the Track. For instance, the use of		MUST answer to the Root with a negative DAO-ACK indicating the
	compression per [RFC8138] is determined by whether it is used in the		successor that is unreachable (suggested status 11 to be confirmed by
	main instance, e.g., by setting the "T" flag [TURN-ON_RFC8138] in the		IANA).
	RPL configuration option.
	7.5. Non-Storing Mode Projected Route		The process continues till the P-DAO is propagated to ingress router
			of the Segment, which answers with a DAO-ACK to the Root.
	As illustrated in Figure 9, a P-DAO that carries an SR-VIO enables		A Segment Lifetime of 0 in a VIOis used to clean up the state. The
	the Root to install a source-routed path towards a Track Egress in		P-DAO is forwarded as described above, but the DAO is interpreted as
	any particular router.		a No-Path DAO and results in cleaning up existing state as opposed to
			refreshing an existing one or installing a new one.
			In case of a forwarding error along an Storing-Mode P-Route, the node
			that fails to forward SHOULD send an ICMP error with a code "Error in
			Projected Route" to the Root. Failure to do so may result in packet
			loss and wasted resources along the Projected Route that is broken.
			7.3.2. Non-Storing-Mode P-Route
			As illustrated in Figure 10, a P-DAO that carries an SR-VIO enables
			the Root to install a source-routed path from a Track Ingress towards
			a Target along the main DODAG.
	------+---------		------+---------
	| Internet		| Internet
	|		|
	+-----+		+-----+
	| | Border Router		| | Border Router
	| | (RPL Root)		| | (RPL Root)
	+-----+ | P ^ ACK		+-----+ | P ^ ACK
	| Track | DAO |		| Track | DAO |
	o o o o Ingress X V | X		o o o o Ingress X V | X
	skipping to change at page 22, line 26 ¶		skipping to change at page 23, line 32 ¶
	o o ° o o o o X o X Segment		o o ° o o o o X o X Segment
	o o o o o o o o X Track X		o o o o o o o o X Track X
	o o o o o Egress		o o o o o Egress
	o o o o		o o o o
	o o o o		o o o o
	destination		destination
	LLN		LLN
	Figure 9: Projecting a Non-Storing Route		Figure 10: Projecting a Non-Storing Route
	A route indicated by an SR-VIO may be loose, meaning that the node
	that owns the next listed Via Address is not necessarily a neighbor.
	Without proper loop avoidance mechanisms, the interaction of loose
	source routing and other mechanisms may effectively cause loops.
	When forwarding a packet to a destination for which the router		When forwarding a packet to a destination for which the router
	determines that routing happens via the Track Egress, the router		determines that routing happens via a Track Target, the router
	inserts the source routing header in the packet with the destination		inserts the Source Routing Header in the packet with the final
	set to the Track Egress.		destination at the Track Egress.
	In order to signal the Segment, the router encapsulates the packet		In order to signal the Segment, the router encapsulates the packet
	with an IP-in-IP header and a Routing Header as follows:		with an IP-in-IP header and a Routing Header as follows:
	* In the uncompressed form the source of the packet is this router,		* In the uncompressed form the source of the packet is this router,
	the destination is the first Via Address in the SR-VIO, and the RH		the destination is the first Via Address in the SR-VIO, and the RH
	is a Source Routing Header (SRH) [RFC6554] that contains the list		is a Source Routing Header (SRH) [RFC6554] that contains the list
	of the remaining Via Addresses terminating by the Track Egress.		of the remaining Via Addresses terminating by the Track Egress.
	* The preferred alternate in a network where 6LoWPAN Header		* The preferred alternate in a network where 6LoWPAN Header
	skipping to change at page 23, line 28 ¶		skipping to change at page 24, line 28 ¶
	In case of a forwarding error along a Source Route path, the node		In case of a forwarding error along a Source Route path, the node
	that fails to forward SHOULD send an ICMP error with a code "Error in		that fails to forward SHOULD send an ICMP error with a code "Error in
	Source Routing Header" back to the source of the packet, as described		Source Routing Header" back to the source of the packet, as described
	in section 11.2.2.3. of [RPL]. Upon this message, the encapsulating		in section 11.2.2.3. of [RPL]. Upon this message, the encapsulating
	node SHOULD stop using the source route path for a period of time and		node SHOULD stop using the source route path for a period of time and
	it SHOULD send an ICMP message with a Code "Error in Projected Route"		it SHOULD send an ICMP message with a Code "Error in Projected Route"
	to the Root. Failure to follow these steps may result in packet loss		to the Root. Failure to follow these steps may result in packet loss
	and wasted resources along the source route path that is broken.		and wasted resources along the source route path that is broken.
	7.6. Storing Mode Projected Route		7.4. Forwarding Along a Track
	As illustrated in Figure 10, a P-DAO that carries a SF-VIO enables		This draft leverages the RPL Forwarding model follows:
	the Root to install a stateful route towards a collection of Targets
	along a Segment between a Track Ingress and a Track Egress.
	------+---------		* In the data packets, the Track DODAGID and the TrackID MUST be
	| Internet		respectively signaled as the IPv6 Source Address and the
	|		RPLInstanceID field of the RPI that MUST be placed in the outer
	+-----+		chain of IPv6 Headers.
	| | Border Router
	| | (RPL Root)
	+-----+ | ^ |
	| | DAO | ACK |
	o o o o | | |
	o o o o o o o o o | ^ | Projected .
	o o o o o o o o o o | | DAO | Route .
	o o o o o o o o o | ^ | .
	o o o o o o o o v | DAO v .
	o o LLN o o o |
	o o o o o Loose Source Route Path |
	o o o o From Root To Destination v
	Figure 10: Projecting a route		The RPI carries a local RPLInstanceID called the TrackID, which,
			in association with the DODAGID, indicates the Track along which
			the packet is forwarded.
	In order to install the relevant routing state along the Segment ,		The 'D' flag in the RPLInstanceID MUST be set to 0 to indicate
	the Root sends a unicast P-DAO message to the Track Egress router of		that the source address in the IPv6 header is set ot the DODAGID,
	the routing Segment that is being installed. The P-DAO message		more in Section 7.4.
	contains a SF-VIO with the direct sequence of Via Addresses. The SF-
	VIO follows one or more RTOs indicating the Targets to which the
	Track leads. The SF-VIO contains a Segment Lifetime for which the
	state is to be maintained.
	The Root sends the P-DAO directly to the egress node of the Segment.		* This draft conforms the principles of [USEofRPLinfo] with regards
	In that P-DAO, the destination IP address matches the last Via		to packet forwarding and encapsulation along a Track.
	Address in the SF-VIO. This is how the egress recognizes its role.
	In a similar fashion, the ingress node recognizes its role as it
	matches first Via Address in the SF-VIO.
	The Egress node of the Segment is the only node in the path that does		- In that case, the Track is the DODAG, the Track Ingress is the
	not install a route in response to the P-DAO; it is expected to be		Root, and the Track Egress is a RAL, and neighbors of the Track
	already able to route to the Target(s) on its own. If one of the		Egress that can be reached via the Track are RULs. The
	Targets is not known, the node MUST answer to the Root with a		encapsulation rules in [USEofRPLinfo] apply.
	negative DAO-ACK listing the Target(s) that could not be located
	(suggested status 10 to be confirmed by IANA).
	If the egress node can reach all the Targets, then it forwards the		- If the Track Ingress is the originator of the packet and the
	P-DAO with unchanged content to its loose predecessor in the Segment		Track Egress is the destination of the packet, there is no need
	as indicated in the list of Via Information options, and recursively		for an encapsulation.
	the message is propagated unchanged along the sequence of routers
	indicated in the P-DAO, but in the reverse order, from egress to
	ingress.
	The address of the predecessor to be used as destination of the		- So the Track Ingress must encapsulate the traffic that it did
	propagated DAO message is found in the Via Address the precedes the		not originate, and add an RPI in any fashion.
	one that contain the address of the propagating node, which is used
	as source of the message.
	Upon receiving a propagated DAO, all except the Egress Router MUST		A packet that is being routed over the RPL Instance associated to
	install a route towards the DAO Target(s) via their successor in the		a first Non-Storing Mode Track MAY be placed (encapsulated) in a
	SF-VIO. The router MAY install additional routes towards the VIA		second Track to cover one loose hop of the first Track. On the
	Addresses that are the SF-VIO after the next one, if any, but in case		other hand, a Storing Mode Track must be strict and a packet that
	of a conflict or a lack of resource, the route(s) to the Target(s)		it placed in a Storing Mode Track MUST follow that Track till the
	have precedence.		Track Egress.
	If a router cannot reach its predecessor in the SF-VIO, the router		When a Track Egress extracts a packet from a Track (decapsulates
	MUST answer to the Root with a negative DAO-ACK indicating the		the packet), the Destination of the inner packet MUST be either
	successor that is unreachable (suggested status 11 to be confirmed by		this node or a direct neighbor, or a Target of another Segment of
	IANA).		the same Track for which this node is ingress, otherwise the
			packet MUST be dropped.
	The process continues till the P-DAO is propagated to ingress router		All properties of a Track operations are inherited form the main RPL
	of the Segment, which answers with a DAO-ACK to the Root.		Instance that is used to install the Track. For instance, the use of
			compression per [RFC8138] is determined by whether it is used in the
			main instance, e.g., by setting the "T" flag [TURN-ON_RFC8138] in the
			RPL configuration option.
	A Segment Lifetime of 0 in a Via Information option is used to clean		8. Profiles
	up the state. The P-DAO is forwarded as described above, but the DAO
	is interpreted as a No-Path DAO and results in cleaning up existing
	state as opposed to refreshing an existing one or installing a new
	one.
	In case of a forwarding error along an SMPR, the node that fails to		This document provides a set of tools that may or may not be needed
	forward SHOULD send an ICMP error with a code "Error in Projected		by an implementation depending on the type of application it serves.
	Route" to the Root. Failure to do so may result in packet loss and		This sections described profiles that can be implemented separately
	wasted resources along the Projected Route that is broken.		and can be used to discriminate what an implementation can and cannot
			do.
	8. Security Considerations		Profile 0 Profile 0 is the legacy support of [RPL] Non-Storing Mode.
			It provides the minimal common functionality that must be
			implemented as a prerequisite to all the Track-supporting
			profiles. The other Profiles extend Profile 0 with selected
			capabilities that this specification introduces on top.
			Profile 1 (Storing-Mode P-Route Segments along the main DODAG) Profi
			le 1 does not create new paths; it combines Storing and Non-
			Storing Modes to balance the size of the routing header in the
			packet and the amount of state in the intermediate routers in a
			Non-Storing Mode RPL DODAG.
			Profile 2 (Non-Storing-Mode P-Route Segments along the main DODAG) P
			rofile 2 extends Profile 0 with Strict Source-Routing Non-Storing-
			Mode Projected Routes along the main DODAG. Profile 2 provides
			the same capability to compress the SRH in packets down the main
			DODAG as Profile 1, but it require an encapsulation, in order to
			insert an additional SRH between the loose source routing hops.
			Profile 3 Profile 3 and above build Tracks that do not necessarily
			follow the main DODAG. In order to form the best path possible,
			those Profiles require the support of Sibling Information Option
			to inform the Root of additional possible hops. Profile 3 extends
			Profile 1 with additional Storing-Mode Projected Routes that
			install segments that do not follow the main DODAG. Segments can
			be associated in a Track rooted at an Ingress node, but there is
			no explicit Egress node, and no source routing operation.
			Profile 4 Profile 4 extends Profile 2 with Strict Source-Routing
			Non-Storing-Mode Projected Routes to form Tracks inside the main
			DODAG. A Track is formed as one or more strict source source
			routed paths between the Root that is the Track Ingress, and the
			Track Egress that is the last node
			Profile 5 Profile 5 Combines Profile 4 with Profile 1 and enables to
			loose source routing between the Ingress and the Egress of the
			Track. As in Profile 1, Storing-Mode Projected Routes connect the
			dots in the loose source route.
			Profile 6 Profile 6 Combines Profile 4 with Profile 2 and also
			enables to loose source routing between the Ingress and the Egress
			of the Track.
			9. Example Track Signaling
			The remainder of the section provides an example of how a Track can
			be signaled
			===> F
			A ===> B ===> C ===> D===> E <
			===> G
			Figure 11: Reference Track
			A is Track ingress, E is track Egress. C is stitching point. F and
			G are E's neighbors, "external" to the Track, and reachable from A
			over the Track A->E.
			In a general manner we want:
			* P-DAO 1 signals C==>B==>E
			* P-DAO 2 signals A==>B==>C
			* P-DAO 3 signals F and G via the A==>E Track
			P-DAO 3 being loose, it can only be non-storing. Note that since the
			Root is always the ingress of a Track, and all SR-VIOs are now Track,
			the Root being signaled in the DAO base object can now be elided in
			the VIA list in SR-VIO. This enables the construction by the main
			root of the RFC 8138 optimized SRH-6LoRH in the SR-VIO, to be placed
			as is in the packet by the Root.
			9.1. Using Storing-Mode Segments
			A==>B==>C and C==>D==>E are segments of a same Track. Note that the
			storing mode signaling imposes strict continuity in a segment. One
			benefit of strict routing is that loops are avoided along the Track.
			9.1.1. Stitched Segments
			Storing-Mode P-DAO 1 and 2 are sent to E and C, as follows:
			+===============+==============+==============+
			| Field | P-DAO 1 to E | P-DAO 2 to C |
			+===============+==============+==============+
			| Mode | Storing | Storing |
			+---------------+--------------+--------------+
			| Track Ingress | A | A |
			+---------------+--------------+--------------+
			| TrackID | (A, 129) | (A, 129) |
			+---------------+--------------+--------------+
			| VIO | C, D, E | A, B, C |
			+---------------+--------------+--------------+
			| Targets | E, F, G | E, F, G |
			+---------------+--------------+--------------+
			Table 1: P-DAO Messages
			As a result the RIBs are set as follows:
			+======+=============+=========+=============+==========+
			| Node | Destination | Origin | Next Hop(s) | TrackID |
			+======+=============+=========+=============+==========+
			| E | F, G | P-DAO 1 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| D | E | P-DAO 1 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| " | F, G | P-DAO 1 | E | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| C | D | P-DAO 1 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| " | E, F, G | P-DAO 1 | D | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| B | C | P-DAO 2 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| " | E, F, G | P-DAO 2 | C | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| A | B | P-DAO 2 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| A | E, F, G | P-DAO 2 | B | (A, 129) |
			+------+-------------+---------+-------------+----------+
			Table 2: RIB setting
			E recognizes that it is the Track Egress because it is both a Target
			and a Segment Endpoint.
			Packets originated by A to E, F, or G, do not require an
			encapsulation. In any fashion, the outer headers of the packets that
			are forwarded along the Track have the following settings:
			+========+===================+===================+================+
			| Header | IPv6 Source Addr. | IPv6 Dest. Addr. | TrackID in RPI |
			+========+===================+===================+================+
			| Outer | A | E, F or G | (A, 129) |
			+--------+-------------------+-------------------+----------------+
			| Inner | X != A | E, F or G | N/A |
			+--------+-------------------+-------------------+----------------+
			Table 3: Packet header settings
			As an example, say that A has a packet for F. Using the RIB above:
			* From P-DAO 2: A forwards to B and B forwards to C.
			* From P-DAO 1: C forwards to D and D forwards to E.
			* From Neighbor Cache Entry: C delivers the packet to F.
			9.1.2. External routes
			Storing-Mode P-DAO 1 and 2, and Non-Storing-Mode P-DAO 3, are sent to
			E, C and A, respectively, as follows:
			+===============+==============+==============+==============+
			| | P-DAO 1 to E | P-DAO 2 to C | P-DAO 3 to A |
			+===============+==============+==============+==============+
			| Mode | Storing | Storing | Non-Storing |
			+---------------+--------------+--------------+--------------+
			| Track Ingress | A | A | A |
			+---------------+--------------+--------------+--------------+
			| TrackID | (A, 129) | (A, 129) | (A, 129) |
			+---------------+--------------+--------------+--------------+
			| VIO | C, D, E | A, B, C | E |
			+---------------+--------------+--------------+--------------+
			| Targets | E | E | F, G |
			+---------------+--------------+--------------+--------------+
			Table 4: P-DAO Messages
			As a result the RIBs are set as follows:
			+======+=============+=========+=============+==========+
			| Node | Destination | Origin | Next Hop(s) | TrackID |
			+======+=============+=========+=============+==========+
			| E | F, G | P-DAO 1 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| D | E | P-DAO 1 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| C | D | P-DAO 1 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| " | E | P-DAO 1 | D | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| B | C | P-DAO 2 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| " | E | P-DAO 2 | C | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| A | B | P-DAO 2 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| A | E | P-DAO 2 | B | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| A | F, G | P-DAO 3 | E | (A, 129) |
			+------+-------------+---------+-------------+----------+
			Table 5: RIB setting
			Packets from A to E do not require an encapsulation. In any fashion,
			the outer headers of the packets that are forwarded along the Track
			have the following settings:
			+========+===================+====================+================+
			| Header | IPv6 Source Addr. | IPv6 Dest. Addr. | TrackID in RPI |
			+========+===================+====================+================+
			| Outer | A | E | (A, 129) |
			+--------+-------------------+--------------------+----------------+
			| Inner | X | E (X != A), F or G | N/A |
			+--------+-------------------+--------------------+----------------+
			Table 6: Packet header settings
			As an example, say that A has a packet for F. Using the RIB above:
			* From P-DAO 3: A encapsulates the packet the Track signaled by
			P-DAO 3, with the outer header above. Now the packet destination
			is E.
			* From P-DAO 2: A forwards to B and B forwards to C.
			* From P-DAO 1: C forwards to D and D forwards to E; E decapsulates
			the packet.
			* From Neighbor Cache Entry: C delivers packets to F or G.
			9.1.3. Segment Routing
			Storing-Mode P-DAO 1 and 2, and Non-Storing-Mode P-DAO 3, are sent to
			E, B and A, respectively, as follows:
			+===============+==============+==============+==============+
			| | P-DAO 1 to E | P-DAO 2 to B | P-DAO 3 to A |
			+===============+==============+==============+==============+
			| Mode | Storing | Storing | Non-Storing |
			+---------------+--------------+--------------+--------------+
			| Track Ingress | A | A | A |
			+---------------+--------------+--------------+--------------+
			| TrackID | (A, 129) | (A, 129) | (A, 129) |
			+---------------+--------------+--------------+--------------+
			| VIO | C, D, E | A, B | C, E |
			+---------------+--------------+--------------+--------------+
			| Targets | E | B, C | F, G |
			+---------------+--------------+--------------+--------------+
			Table 7: P-DAO Messages
			As a result the RIBs are set as follows:
			+======+=============+=========+=============+==========+
			| Node | Destination | Origin | Next Hop(s) | TrackID |
			+======+=============+=========+=============+==========+
			| E | F, G | P-DAO 1 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| D | E | P-DAO 1 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| C | D | P-DAO 1 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| " | E | P-DAO 1 | D | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| B | C | P-DAO 2 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| A | B | P-DAO 2 | Neighbor | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| " | C | P-DAO 2 | B | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| " | E, F, G | P-DAO 3 | C, E | (A, 129) |
			+------+-------------+---------+-------------+----------+
			Table 8: RIB setting
			Packets from A to E do not require an encapsulation, but carry a SRH
			via C. In any fashion, the outer headers of the packets that are
			forwarded along the Track have the following settings:
			+========+===================+====================+================+
			| Header | IPv6 Source Addr. | IPv6 Dest. Addr. | TrackID in RPI |
			+========+===================+====================+================+
			| Outer | A | C till C then E | (A, 129) |
			+--------+-------------------+--------------------+----------------+
			| Inner | X | E (X != A), F or G | N/A |
			+--------+-------------------+--------------------+----------------+
			Table 9: Packet header settings
			As an example, say that A has a packet for F. Using the RIB above:
			* From P-DAO 3: A encapsulates the packet the Track signaled by
			P-DAO 3, with the outer header above. Now the destination in the
			IPv6 Header is C, and a SRH signals the final destination is E.
			* From P-DAO 2: A forwards to B and B forwards to C.
			* From P-DAO 3: C processes the SRH and sets the destination in the
			IPv6 Header to E.
			* From P-DAO 1: C forwards to D and D forwards to E; E decapsulates
			the packet.
			* From the Neighbor Cache Entry: C delivers packets to F or G.
			9.2. Using Non-Storing-Mode joining Tracks
			A==>B==>C and C==>D==>E are Tracks expressed as non-storing P-DAOs.
			9.2.1. Stitched Tracks
			Non-Storing Mode P-DAO 1 and 2 are sent to C and A respectively, as
			follows:
			+===============+==============+==============+
			| | P-DAO 1 to C | P-DAO 2 to A |
			+===============+==============+==============+
			| Mode | Non-Storing | Non-Storing |
			+---------------+--------------+--------------+
			| Track Ingress | C | A |
			+---------------+--------------+--------------+
			| TrackID | (C, 131) | (A, 129) |
			+---------------+--------------+--------------+
			| VIO | D, E | B, C |
			+---------------+--------------+--------------+
			| Targets | F, G | E, F, G |
			+---------------+--------------+--------------+
			Table 10: P-DAO Messages
			As a result the RIBs are set as follows:
			+======+=============+=========+=============+==========+
			| Node | Destination | Origin | Next Hop(s) | TrackID |
			+======+=============+=========+=============+==========+
			| E | F, G | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| D | E | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| C | D | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| " | E, F, G | P-DAO 1 | D, E | (C, 131) |
			+------+-------------+---------+-------------+----------+
			| B | C | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| A | B | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| " | C, E, F, G | P-DAO 2 | B, C | (A, 129) |
			+------+-------------+---------+-------------+----------+
			Table 11: RIB setting
			Packets from A to E, F and G do not require an encapsulation, though
			it is preferred that A encapsulates and C decapsulates. Either way,
			they carry a SRH via B and C, and C needs to encapsulate to E, F, or
			G to add an SRH via D and E. The encapsulating headers of packets
			that are forwarded along the Track between C and E have the following
			settings:
			+========+===================+===================+================+
			| Header | IPv6 Source Addr. | IPv6 Dest. Addr. | TrackID in RPI |
			+========+===================+===================+================+
			| Outer | C | D till D then E | (C, 131) |
			+--------+-------------------+-------------------+----------------+
			| Inner | X | E, F, or G | N/A |
			+--------+-------------------+-------------------+----------------+
			Table 12: Packet header settings
			As an example, say that A has a packet for F. Using the RIB above:
			* From P-DAO 2: A encapsulates the packet with destination of F in
			the Track signaled by P-DAO 2. The outer header has source A,
			destination B, an SRH that indicates C as the next loose hop, and
			a RPI indicating a TrackId of 129 from A's namespace.
			* From the SRH: Packets forwarded by B have source A, destination C
			, a consumed SRH, and a RPI indicating a TrackId of 129 from A's
			namespace. C decapsulates.
			* From P-DAO 1: C encapsulates the packet with destination of F in
			the Track signaled by P-DAO 1. The outer header has source C,
			destination D, an SRH that indicates E as the next loose hop, and
			a RPI indicating a TrackId of 131 from C's namespace. E
			decapsulates.
			9.2.2. External routes
			Non-Storing Mode P-DAO 1 is sent to C and Non-Storing Mode P-DAO 2
			and 3 are sent A, as follows:
			+===============+==============+==============+==============+
			| | P-DAO 1 to C | P-DAO 2 to A | P-DAO 3 to A |
			+===============+==============+==============+==============+
			| Mode | Non-Storing | Non-Storing | Non-Storing |
			+---------------+--------------+--------------+--------------+
			| Track Ingress | C | A | A |
			+---------------+--------------+--------------+--------------+
			| TrackID | (C, 131) | (A, 129) | (A, 141) |
			+---------------+--------------+--------------+--------------+
			| VIO | D, E | B, C | E |
			+---------------+--------------+--------------+--------------+
			| Targets | E | E | F, G |
			+---------------+--------------+--------------+--------------+
			Table 13: P-DAO Messages
			As a result the RIBs are set as follows:
			+======+=============+=========+=============+==========+
			| Node | Destination | Origin | Next Hop(s) | TrackID |
			+======+=============+=========+=============+==========+
			| E | F, G | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| D | E | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| C | D | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| " | E | P-DAO 1 | D, E | (C, 131) |
			+------+-------------+---------+-------------+----------+
			| B | C | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| A | B | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| " | C, E | P-DAO 2 | B, C | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| " | F, G | P-DAO 3 | E | (A, 141) |
			+------+-------------+---------+-------------+----------+
			Table 14: RIB setting
			The encapsulating headers of packets that are forwarded along the
			Track between C and E have the following settings:
			+========+===================+===================+================+
			| Header | IPv6 Source Addr. | IPv6 Dest. Addr. | TrackID in RPI |
			+========+===================+===================+================+
			| Outer | C | D till D then E | (C, 131) |
			+--------+-------------------+-------------------+----------------+
			| Middle | A | E | (A, 141) |
			+--------+-------------------+-------------------+----------------+
			| Inner | X | E, F or G | N/A |
			+--------+-------------------+-------------------+----------------+
			Table 15: Packet header settings
			As an example, say that A has a packet for F. Using the RIB above:
			* From P-DAO 3: A encapsulates the packet with destination of F in
			the Track signaled by P-DAO 3. The outer header has source A,
			destination E, and a RPI indicating a TrackId of 141 from A's
			namespace. This recurses with:
			* From P-DAO 2: A encapsulates the packet with destination of E in
			the Track signaled by P-DAO 2. The outer header has source A,
			destination B, an SRH that indicates C as the next loose hop, and
			a RPI indicating a TrackId of 129 from A's namespace.
			* From the SRH: Packets forwarded by B have source A, destination C
			, a consumed SRH, and a RPI indicating a TrackId of 129 from A's
			namespace. C decapsulates.
			* From P-DAO 1: C encapsulates the packet with destination of E in
			the Track signaled by P-DAO 1. The outer header has source C,
			destination D, an SRH that indicates E as the next loose hop, and
			a RPI indicating a TrackId of 131 from C's namespace. E
			decapsulates.
			9.2.3. Segment Routing
			Non-Storing Mode P-DAO 1 is sent to C and Non-Storing Mode P-DAO 2
			and 3 are sent A, as follows:
			+===============+==============+==============+==============+
			| | P-DAO 1 to C | P-DAO 2 to A | P-DAO 3 to A |
			+===============+==============+==============+==============+
			| Mode | Non-Storing | Non-Storing | Non-Storing |
			+---------------+--------------+--------------+--------------+
			| Track Ingress | C | A | A |
			+---------------+--------------+--------------+--------------+
			| TrackID | (C, 131) | (A, 129) | (A, 141) |
			+---------------+--------------+--------------+--------------+
			| VIO | D, E | B | C, E |
			+---------------+--------------+--------------+--------------+
			| Targets | | C | F, G |
			+---------------+--------------+--------------+--------------+
			Table 16: P-DAO Messages
			As a result the RIBs are set as follows:
			+======+=============+=========+=============+==========+
			| Node | Destination | Origin | Next Hop(s) | TrackID |
			+======+=============+=========+=============+==========+
			| E | F, G | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| D | E | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| C | D | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| " | E | P-DAO 1 | D, E | (C, 131) |
			+------+-------------+---------+-------------+----------+
			| B | C | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| A | B | ND | Neighbor | Any |
			+------+-------------+---------+-------------+----------+
			| " | C | P-DAO 2 | B, C | (A, 129) |
			+------+-------------+---------+-------------+----------+
			| " | E, F, G | P-DAO 3 | C, E | (A, 141) |
			+------+-------------+---------+-------------+----------+
			Table 17: RIB setting
			The encapsulating headers of packets that are forwarded along the
			Track between A and B have the following settings:
			+========+===================+===================+================+
			| Header | IPv6 Source Addr. | IPv6 Dest. Addr. | TrackID in RPI |
			+========+===================+===================+================+
			| Outer | A | B till D then E | (A, 129) |
			+--------+-------------------+-------------------+----------------+
			| Middle | A | C | (A, 141) |
			+--------+-------------------+-------------------+----------------+
			| Inner | X | E, F or G | N/A |
			+--------+-------------------+-------------------+----------------+
			Table 18: Packet header settings
			The encapsulating headers of packets that are forwarded along the
			Track between B and C have the following settings:
			+========+===================+===================+================+
			| Header | IPv6 Source Addr. | IPv6 Dest. Addr. | TrackID in RPI |
			+========+===================+===================+================+
			| Outer | A | C | (A, 141) |
			+--------+-------------------+-------------------+----------------+
			| Inner | X | E, F or G | N/A |
			+--------+-------------------+-------------------+----------------+
			Table 19: Packet header settings
			The encapsulating headers of packets that are forwarded along the
			Track between C and E have the following settings:
			+========+===================+===================+================+
			| Header | IPv6 Source Addr. | IPv6 Dest. Addr. | TrackID in RPI |
			+========+===================+===================+================+
			| Outer | C | D till D then E | (C, 131) |
			+--------+-------------------+-------------------+----------------+
			| Middle | A | E | (A, 141) |
			+--------+-------------------+-------------------+----------------+
			| Inner | X | E, F or G | N/A |
			+--------+-------------------+-------------------+----------------+
			Table 20: Packet header settings
			As an example, say that A has a packet for F. Using the RIB above:
			* From P-DAO 3: A encapsulates the packet with destination of F in
			the Track signaled by P-DAO 3. The outer header has source A,
			destination C, an SRH that indicates E as the next loose hop, and
			a RPI indicating a TrackId of 141 from A's namespace. This
			recurses with:
			* From P-DAO 2: A encapsulates the packet with destination of C in
			the Track signaled by P-DAO 2. The outer header has source A,
			destination B, and a RPI indicating a TrackId of 129 from A's
			namespace. B decapsulates forwards to C based on a sibling
			connected route.
			* From the SRH: C consumes the SRH and makes the destination E.
			* From P-DAO 1: C encapsulates the packet with destination of E in
			the Track signaled by P-DAO 1. The outer header has source C,
			destination D, an SRH that indicates E as the next loose hop, and
			a RPI indicating a TrackId of 131 from C's namespace. E
			decapsulates.
			10. Security Considerations
	This draft uses messages that are already present in RPL [RPL] with		This draft uses messages that are already present in RPL [RPL] with
	optional secured versions. The same secured versions may be used		optional secured versions. The same secured versions may be used
	with this draft, and whatever security is deployed for a given		with this draft, and whatever security is deployed for a given
	network also applies to the flows in this draft.		network also applies to the flows in this draft.
	TODO: should probably consider how P-DAO messages could be abused by		TODO: should probably consider how P-DAO messages could be abused by
	a) rogue nodes b) via replay of messages c) if use of P-DAO messages		a) rogue nodes b) via replay of messages c) if use of P-DAO messages
	could in fact deal with any threats?		could in fact deal with any threats?
	9. IANA Considerations		11. IANA Considerations
	9.1. New Elective 6LoWPAN Routing Header Type		11.1. New Elective 6LoWPAN Routing Header Type
	This document updates the IANA registry titled "Elective 6LoWPAN		This document updates the IANA registry titled "Elective 6LoWPAN
	Routing Header Type" that was created for [RFC8138] and assigns the		Routing Header Type" that was created for [RFC8138] and assigns the
	following value:		following value:
	+=======+=============+===============+		+=======+=============+===============+
	| Value | Description | Reference |		| Value | Description | Reference |
	+=======+=============+===============+		+=======+=============+===============+
	| 7 | P-RPI-6LoRH | This document |		| 7 | P-RPI-6LoRH | This document |
	+-------+-------------+---------------+		+-------+-------------+---------------+
	Table 1: New Elective 6LoWPAN		Table 21: New Elective 6LoWPAN
	Routing Header Type		Routing Header Type
	9.2. New Critical 6LoWPAN Routing Header Type		11.2. New Critical 6LoWPAN Routing Header Type
	This document updates the IANA registry titled "Critical 6LoWPAN		This document updates the IANA registry titled "Critical 6LoWPAN
	Routing Header Type" that was created for [RFC8138] and assigns the		Routing Header Type" that was created for [RFC8138] and assigns the
	following value:		following value:
	+=======+=============+===============+		+=======+=============+===============+
	| Value | Description | Reference |		| Value | Description | Reference |
	+=======+=============+===============+		+=======+=============+===============+
	| 7 | P-RPI-6LoRH | This document |		| 7 | P-RPI-6LoRH | This document |
	+-------+-------------+---------------+		+-------+-------------+---------------+
	Table 2: New Critical 6LoWPAN		Table 22: New Critical 6LoWPAN
	Routing Header Type		Routing Header Type
	9.3. New Subregistry For The RPL Option Flags		11.3. New Subregistry For The RPL Option Flags
	IANA is required to create a subregistry for the 8-bit RPL Option		IANA is required to create a subregistry for the 8-bit RPL Option
	Flags field, as detailed in Figure 2, under the "Routing Protocol for		Flags field, as detailed in Figure 2, under the "Routing Protocol for
	Low Power and Lossy Networks (RPL)" registry. The bits are indexed		Low Power and Lossy Networks (RPL)" registry. The bits are indexed
	from 0 (leftmost) to 7. Each bit is tracked with the following		from 0 (leftmost) to 7. Each bit is tracked with the following
	qualities:		qualities:
	* Bit number (counting from bit 0 as the most significant bit)		* Bit number (counting from bit 0 as the most significant bit)
	* Indication When Set		* Indication When Set
	* Reference		* Reference
	Registration procedure is "Standards Action" [RFC8126]. The initial		Registration procedure is "Standards Action" [RFC8126]. The initial
	allocation is as indicated in Table 6:		allocation is as indicated in Table 26:
	+============+======================+===============+		+============+======================+===============+
	| Bit number | Indication When Set | Reference |		| Bit number | Indication When Set | Reference |
	+============+======================+===============+		+============+======================+===============+
	| 0 | Down 'O' | [RFC6553] |		| 0 | Down 'O' | [RFC6553] |
	+------------+----------------------+---------------+		+------------+----------------------+---------------+
	| 1 | Rank-Error (R) | [RFC6553] |		| 1 | Rank-Error (R) | [RFC6553] |
	+------------+----------------------+---------------+		+------------+----------------------+---------------+
	| 2 | Forwarding-Error (F) | [RFC6553] |		| 2 | Forwarding-Error (F) | [RFC6553] |
	+------------+----------------------+---------------+		+------------+----------------------+---------------+
	| 3 | Projected-Route (P) | This document |		| 3 | Projected-Route (P) | This document |
	+------------+----------------------+---------------+		+------------+----------------------+---------------+
	Table 3: Initial PDR Flags		Table 23: Initial PDR Flags
	9.4. New RPL Control Codes		11.4. New RPL Control Codes
	This document extends the IANA Subregistry created by RFC 6550 for		This document extends the IANA Subregistry created by RFC 6550 for
	RPL Control Codes as indicated in Table 4:		RPL Control Codes as indicated in Table 24:
	+======+=============================+===============+		+======+=============================+===============+
	| Code | Description | Reference |		| Code | Description | Reference |
	+======+=============================+===============+		+======+=============================+===============+
	| 0x09 | Projected DAO Request (PDR) | This document |		| 0x09 | Projected DAO Request (PDR) | This document |
	+------+-----------------------------+---------------+		+------+-----------------------------+---------------+
	| 0x0A | PDR-ACK | This document |		| 0x0A | PDR-ACK | This document |
	+------+-----------------------------+---------------+		+------+-----------------------------+---------------+
	Table 4: New RPL Control Codes		Table 24: New RPL Control Codes
	9.5. New RPL Control Message Options		11.5. New RPL Control Message Options
	This document extends the IANA Subregistry created by RFC 6550 for		This document extends the IANA Subregistry created by RFC 6550 for
	RPL Control Message Options as indicated in Table 5:		RPL Control Message Options as indicated in Table 25:
	+=======+==========================================+===============+		+=======+============================+===============+
	| Value | Meaning | Reference |		| Value | Meaning | Reference |
	+=======+==========================================+===============+		+=======+============================+===============+
	| 0x0B | Stateful Via Information option (SF-VIO) | This document |		| 0x0B | Stateful VIO(SF-VIO) | This document |
	+-------+------------------------------------------+---------------+		+-------+----------------------------+---------------+
	| 0x0C | Source-Routed Via Information option | This document |		| 0x0C | Source-Routed VIO(SR-VIO) | This document |
	| | (SR-VIO) | |		+-------+----------------------------+---------------+
	+-------+------------------------------------------+---------------+		| 0x0D | Sibling Information option | This document |
	| 0x0D | Sibling Information option | This document |		+-------+----------------------------+---------------+
	+-------+------------------------------------------+---------------+
	Table 5: RPL Control Message Options		Table 25: RPL Control Message Options
	9.6. SubRegistry for the Projected DAO Request Flags		11.6. SubRegistry for the Projected DAO Request Flags
	IANA is required to create a registry for the 8-bit Projected DAO		IANA is required to create a registry for the 8-bit Projected DAO
	Request (PDR) Flags field. Each bit is tracked with the following		Request (PDR) Flags field. Each bit is tracked with the following
	qualities:		qualities:
	* Bit number (counting from bit 0 as the most significant bit)		* Bit number (counting from bit 0 as the most significant bit)
	* Capability description		* Capability description
	* Reference		* Reference
	Registration procedure is "Standards Action" [RFC8126]. The initial		Registration procedure is "Standards Action" [RFC8126]. The initial
	allocation is as indicated in Table 6:		allocation is as indicated in Table 26:
	+============+========================+===============+		+============+========================+===============+
	| Bit number | Capability description | Reference |		| Bit number | Capability description | Reference |
	+============+========================+===============+		+============+========================+===============+
	| 0 | PDR-ACK request (K) | This document |		| 0 | PDR-ACK request (K) | This document |
	+------------+------------------------+---------------+		+------------+------------------------+---------------+
	| 1 | Requested path should | This document |		| 1 | Requested path should | This document |
	| | be redundant (R) | |		| | be redundant (R) | |
	+------------+------------------------+---------------+		+------------+------------------------+---------------+
	Table 6: Initial PDR Flags		Table 26: Initial PDR Flags
	9.7. SubRegistry for the PDR-ACK Flags		11.7. SubRegistry for the PDR-ACK Flags
	IANA is required to create an subregistry for the 8-bit PDR-ACK Flags		IANA is required to create an subregistry for the 8-bit PDR-ACK Flags
	field. Each bit is tracked with the following qualities:		field. Each bit is tracked with the following qualities:
	* Bit number (counting from bit 0 as the most significant bit)		* Bit number (counting from bit 0 as the most significant bit)
	* Capability description		* Capability description
	* Reference		* Reference
	Registration procedure is "Standards Action" [RFC8126]. No bit is		Registration procedure is "Standards Action" [RFC8126]. No bit is
	currently defined for the PDR-ACK Flags.		currently defined for the PDR-ACK Flags.
	9.8. Subregistry for the PDR-ACK Acceptance Status Values		11.8. Subregistry for the PDR-ACK Acceptance Status Values
	IANA is requested to create a Subregistry for the PDR-ACK Acceptance		IANA is requested to create a Subregistry for the PDR-ACK Acceptance
	Status values.		Status values.
	* Possible values are 6-bit unsigned integers (0..63).		* Possible values are 6-bit unsigned integers (0..63).
	* Registration procedure is "Standards Action" [RFC8126].		* Registration procedure is "Standards Action" [RFC8126].
	* Initial allocation is as indicated in Table 7:		* Initial allocation is as indicated in Table 27:
	+-------+------------------------+---------------+		+-------+------------------------+---------------+
	| Value | Meaning | Reference |		| Value | Meaning | Reference |
	+-------+------------------------+---------------+		+-------+------------------------+---------------+
	| 0 | Unqualified acceptance | This document |		| 0 | Unqualified acceptance | This document |
	+-------+------------------------+---------------+		+-------+------------------------+---------------+
	Table 7: Acceptance values of the PDR-ACK Status		Table 27: Acceptance values of the PDR-ACK Status
	9.9. Subregistry for the PDR-ACK Rejection Status Values		11.9. Subregistry for the PDR-ACK Rejection Status Values
	IANA is requested to create a Subregistry for the PDR-ACK Rejection		IANA is requested to create a Subregistry for the PDR-ACK Rejection
	Status values.		Status values.
	* Possible values are 6-bit unsigned integers (0..63).		* Possible values are 6-bit unsigned integers (0..63).
	* Registration procedure is "Standards Action" [RFC8126].		* Registration procedure is "Standards Action" [RFC8126].
	* Initial allocation is as indicated in Table 8:		* Initial allocation is as indicated in Table 28:
	+-------+-----------------------+---------------+		+-------+-----------------------+---------------+
	| Value | Meaning | Reference |		| Value | Meaning | Reference |
	+-------+-----------------------+---------------+		+-------+-----------------------+---------------+
	| 0 | Unqualified rejection | This document |		| 0 | Unqualified rejection | This document |
	+-------+-----------------------+---------------+		+-------+-----------------------+---------------+
	Table 8: Rejection values of the PDR-ACK Status		Table 28: Rejection values of the PDR-ACK Status
	9.10. SubRegistry for the Via Information Options Flags		11.10. SubRegistry for the Via Information Options Flags
	IANA is requested to create a Subregistry for the 5-bit Via		IANA is requested to create a Subregistry for the 5-bit Via
	Information Options (Via Option) Flags field. Each bit is tracked		Information Options (Via Information Option) Flags field. Each bit
	with the following qualities:		is tracked with the following qualities:
	* Bit number (counting from bit 0 as the most significant bit)		* Bit number (counting from bit 0 as the most significant bit)
	* Capability description		* Capability description
	* Reference		* Reference
	Registration procedure is "Standards Action" [RFC8126]. No bit is		Registration procedure is "Standards Action" [RFC8126]. No bit is
	currently defined for the Via Information Options (Via Option) Flags.		currently defined for the Via Information Options (Via Information
			Option) Flags.
	9.11. SubRegistry for the Sibling Information Option Flags		11.11. SubRegistry for the Sibling Information Option Flags
	IANA is required to create a registry for the 5-bit Sibling		IANA is required to create a registry for the 5-bit Sibling
	Information Option (SIO) Flags field. Each bit is tracked with the		Information Option (SIO) Flags field. Each bit is tracked with the
	following qualities:		following qualities:
	* Bit number (counting from bit 0 as the most significant bit)		* Bit number (counting from bit 0 as the most significant bit)
	* Capability description		* Capability description
	* Reference		* Reference
	Registration procedure is "Standards Action" [RFC8126]. The initial		Registration procedure is "Standards Action" [RFC8126]. The initial
	allocation is as indicated in Table 9:		allocation is as indicated in Table 29:
	+============+===================================+===============+		+============+===================================+===============+
	| Bit number | Capability description | Reference |		| Bit number | Capability description | Reference |
	+============+===================================+===============+		+============+===================================+===============+
	| 0 | Connectivity is bidirectional (B) | This document |		| 0 | Connectivity is bidirectional (B) | This document |
	+------------+-----------------------------------+---------------+		+------------+-----------------------------------+---------------+
	Table 9: Initial SIO Flags		Table 29: Initial SIO Flags
	9.12. Error in Projected Route ICMPv6 Code		11.12. New Destination Advertisement Object Flag
			This document modifies the "Destination Advertisement Object (DAO)
			Flags" registry initially created in Section 20.11 of [RPL] .
			Section 3.1 also defines one new entry in the Registry as follows:
			+---------------+------------------------+-----------+
			| Bit Number | Capability Description | Reference |
			+---------------+------------------------+-----------+
			| 2 (suggested) | Projected DAO (P) | THIS RFC |
			+---------------+------------------------+-----------+
			Table 30: New Destination Advertisement Object
			(DAO) Flag
			11.13. Error in Projected Route ICMPv6 Code
	In some cases RPL will return an ICMPv6 error message when a message		In some cases RPL will return an ICMPv6 error message when a message
	cannot be forwarded along a Projected Route. This ICMPv6 error		cannot be forwarded along a Projected Route. This ICMPv6 error
	message is "Error in Projected Route".		message is "Error in Projected Route".
	IANA has defined an ICMPv6 "Code" Fields Registry for ICMPv6 Message		IANA has defined an ICMPv6 "Code" Fields Registry for ICMPv6 Message
	Types. ICMPv6 Message Type 1 describes "Destination Unreachable"		Types. ICMPv6 Message Type 1 describes "Destination Unreachable"
	codes. This specification requires that a new code is allocated from		codes. This specification requires that a new code is allocated from
	the ICMPv6 Code Fields Registry for ICMPv6 Message Type 1, for "Error		the ICMPv6 Code Fields Registry for ICMPv6 Message Type 1, for "Error
	in Projected Route", with a suggested code value of 8, to be		in Projected Route", with a suggested code value of 8, to be
	confirmed by IANA.		confirmed by IANA.
	10. Acknowledgments		12. Acknowledgments
	The authors wish to acknowledge JP Vasseur, Remy Liubing, James		The authors wish to acknowledge JP Vasseur, Remy Liubing, James
	Pylakutty and Patrick Wetterwald for their contributions to the ideas		Pylakutty and Patrick Wetterwald for their contributions to the ideas
	developed here.		developed here.
	11. Normative References		13. 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,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet		[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
	Control Message Protocol (ICMPv6) for the Internet		Control Message Protocol (ICMPv6) for the Internet
	Protocol Version 6 (IPv6) Specification", STD 89,		Protocol Version 6 (IPv6) Specification", STD 89,
	RFC 4443, DOI 10.17487/RFC4443, March 2006,		RFC 4443, DOI 10.17487/RFC4443, March 2006,
	skipping to change at page 31, line 29 ¶		skipping to change at page 45, line 33 ¶
	[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, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for		[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
	Writing an IANA Considerations Section in RFCs", BCP 26,		Writing an IANA Considerations Section in RFCs", BCP 26,
	RFC 8126, DOI 10.17487/RFC8126, June 2017,		RFC 8126, DOI 10.17487/RFC8126, June 2017,
	<https://www.rfc-editor.org/info/rfc8126>.		<https://www.rfc-editor.org/info/rfc8126>.
	12. Informative References		14. Informative References
	[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and		[RFC7102] Vasseur, JP., "Terms Used in Routing for Low-Power and
	Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January		Lossy Networks", RFC 7102, DOI 10.17487/RFC7102, January
	2014, <https://www.rfc-editor.org/info/rfc7102>.		2014, <https://www.rfc-editor.org/info/rfc7102>.
	[RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and		[RFC6997] Goyal, M., Ed., Baccelli, E., Philipp, M., Brandt, A., and
	J. Martocci, "Reactive Discovery of Point-to-Point Routes		J. Martocci, "Reactive Discovery of Point-to-Point Routes
	in Low-Power and Lossy Networks", RFC 6997,		in Low-Power and Lossy Networks", RFC 6997,
	DOI 10.17487/RFC6997, August 2013,		DOI 10.17487/RFC6997, August 2013,
	<https://www.rfc-editor.org/info/rfc6997>.		<https://www.rfc-editor.org/info/rfc6997>.
	[6TiSCH-ARCHI]		[6TiSCH-ARCHI]
	Thubert, P., "An Architecture for IPv6 over the TSCH mode		Thubert, P., "An Architecture for IPv6 over the TSCH mode
	of IEEE 802.15.4", Work in Progress, Internet-Draft,		of IEEE 802.15.4", Work in Progress, Internet-Draft,
	draft-ietf-6tisch-architecture-29, 27 August 2020,		draft-ietf-6tisch-architecture-30, 26 November 2020,
	<https://tools.ietf.org/html/draft-ietf-6tisch-		<https://tools.ietf.org/html/draft-ietf-6tisch-
	architecture-29>.		architecture-30>.
	[RAW-ARCHI]		[RAW-ARCHI]
	Thubert, P., Papadopoulos, G., and R. Buddenberg,		Thubert, P., Papadopoulos, G., and R. Buddenberg,
	"Reliable and Available Wireless Architecture/Framework",		"Reliable and Available Wireless Architecture/Framework",
	Work in Progress, Internet-Draft, draft-pthubert-raw-		Work in Progress, Internet-Draft, draft-pthubert-raw-
	architecture-05, 15 November 2020,		architecture-05, 15 November 2020,
	<https://tools.ietf.org/html/draft-pthubert-raw-		<https://tools.ietf.org/html/draft-pthubert-raw-
	architecture-05>.		architecture-05>.
	[TURN-ON_RFC8138]		[TURN-ON_RFC8138]
	Thubert, P. and L. Zhao, "A RPL DODAG Configuration Option		Thubert, P. and L. Zhao, "A RPL DODAG Configuration Option
	for the 6LoWPAN Routing Header", Work in Progress,		for the 6LoWPAN Routing Header", Work in Progress,
	Internet-Draft, draft-ietf-roll-turnon-rfc8138-17, 30		Internet-Draft, draft-ietf-roll-turnon-rfc8138-18, 18
	September 2020, <https://tools.ietf.org/html/draft-ietf-		December 2020, <https://tools.ietf.org/html/draft-ietf-
	roll-turnon-rfc8138-17>.		roll-turnon-rfc8138-18>.
	[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,		[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
	"Deterministic Networking Architecture", RFC 8655,		"Deterministic Networking Architecture", RFC 8655,
	DOI 10.17487/RFC8655, October 2019,		DOI 10.17487/RFC8655, October 2019,
	<https://www.rfc-editor.org/info/rfc8655>.		<https://www.rfc-editor.org/info/rfc8655>.
	[RFC8025] Thubert, P., Ed. and R. Cragie, "IPv6 over Low-Power		[RFC8025] Thubert, P., Ed. and R. Cragie, "IPv6 over Low-Power
	Wireless Personal Area Network (6LoWPAN) Paging Dispatch",		Wireless Personal Area Network (6LoWPAN) Paging Dispatch",
	RFC 8025, DOI 10.17487/RFC8025, November 2016,		RFC 8025, DOI 10.17487/RFC8025, November 2016,
	<https://www.rfc-editor.org/info/rfc8025>.		<https://www.rfc-editor.org/info/rfc8025>.
	[RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie,		[RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie,
	"IPv6 over Low-Power Wireless Personal Area Network		"IPv6 over Low-Power Wireless Personal Area Network
	(6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138,		(6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138,
	April 2017, <https://www.rfc-editor.org/info/rfc8138>.		April 2017, <https://www.rfc-editor.org/info/rfc8138>.
	[USEofRPLinfo]		[USEofRPLinfo]
	Robles, I., Richardson, M., and P. Thubert, "Using RPI		Robles, I., Richardson, M., and P. Thubert, "Using RPI
	Option Type, Routing Header for Source Routes and IPv6-in-		Option Type, Routing Header for Source Routes and IPv6-in-
	IPv6 encapsulation in the RPL Data Plane", Work in		IPv6 encapsulation in the RPL Data Plane", Work in
	Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-42,		Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-43,
	12 November 2020, <https://tools.ietf.org/html/draft-ietf-		10 January 2021, <https://tools.ietf.org/html/draft-ietf-
	roll-useofrplinfo-42>.		roll-useofrplinfo-43>.
	[PCE] IETF, "Path Computation Element",		[PCE] IETF, "Path Computation Element",
	<https://datatracker.ietf.org/doc/charter-ietf-pce/>.		<https://datatracker.ietf.org/doc/charter-ietf-pce/>.
	Appendix A. Applications		Appendix A. Applications
	A.1. Loose Source Routing		A.1. Loose Source Routing
	A RPL implementation operating in a very constrained LLN typically		A RPL implementation operating in a very constrained LLN typically
	uses the Non-Storing Mode of Operation as represented in Figure 11.		uses the Non-Storing Mode of Operation as represented in Figure 12.
	In that mode, a RPL node indicates a parent-child relationship to the		In that mode, a RPL node indicates a parent-child relationship to the
	Root, using a Destination Advertisement Object (DAO) that is unicast		Root, using a Destination Advertisement Object (DAO) that is unicast
	from the node directly to the Root, and the Root typically builds a		from the node directly to the Root, and the Root typically builds a
	source routed path to a destination down the DODAG by recursively		source routed path to a destination down the DODAG by recursively
	concatenating this information.		concatenating this information.
	------+---------		------+---------
	| Internet		| Internet
	|		|
	+-----+		+-----+
	skipping to change at page 33, line 21 ¶		skipping to change at page 47, line 30 ¶
	+-----+ ^ | |		+-----+ ^ | |
	| | DAO | ACK |		| | DAO | ACK |
	o o o o | | | Strict		o o o o | | | Strict
	o o o o o o o o o | | | Source		o o o o o o o o o | | | Source
	o o o o o o o o o o | | | Route		o o o o o o o o o o | | | Route
	o o o o o o o o o | | |		o o o o o o o o o | | |
	o o o o o o o o | v v		o o o o o o o o | v v
	o o o o		o o o o
	LLN		LLN
	Figure 11: RPL Non-Storing Mode of operation		Figure 12: RPL Non-Storing Mode of operation
	Based on the parent-children relationships expressed in the non-		Based on the parent-children relationships expressed in the non-
	storing DAO messages,the Root possesses topological information about		storing DAO messages,the Root possesses topological information about
	the whole network, though this information is limited to the		the whole network, though this information is limited to the
	structure of the DODAG for which it is the destination. A packet		structure of the DODAG for which it is the destination. A packet
	that is generated within the domain will always reach the Root, which		that is generated within the domain will always reach the Root, which
	can then apply a source routing information to reach the destination		can then apply a source routing information to reach the destination
	if the destination is also in the DODAG. Similarly, a packet coming		if the destination is also in the DODAG. Similarly, a packet coming
	from the outside of the domain for a destination that is expected to		from the outside of the domain for a destination that is expected to
	be in a RPL domain reaches the Root.		be in a RPL domain reaches the Root.
	skipping to change at page 34, line 36 ¶		skipping to change at page 48, line 36 ¶
	become loose.		become loose.
	A.2. Transversal Routes		A.2. Transversal Routes
	RPL is optimized for Point-to-Multipoint (P2MP) and Multipoint-to-		RPL is optimized for Point-to-Multipoint (P2MP) and Multipoint-to-
	Point (MP2P), whereby routes are always installed along the RPL DODAG		Point (MP2P), whereby routes are always installed along the RPL DODAG
	respectively from and towards the DODAG Root. Transversal Peer to		respectively from and towards the DODAG Root. Transversal Peer to
	Peer (P2P) routes in a RPL network will generally suffer from some		Peer (P2P) routes in a RPL network will generally suffer from some
	elongated (stretched) path versus the best possible path, since		elongated (stretched) path versus the best possible path, since
	routing between 2 nodes always happens via a common parent, as		routing between 2 nodes always happens via a common parent, as
	illustrated in Figure 12:		illustrated in Figure 13:
	* In Storing Mode, unless the destination is a child of the source,		* In Storing Mode, unless the destination is a child of the source,
	the packets will follow the default route up the DODAG as well.		the packets will follow the default route up the DODAG as well.
	If the destination is in the same DODAG, they will eventually		If the destination is in the same DODAG, they will eventually
	reach a common parent that has a route to the destination; at		reach a common parent that has a route to the destination; at
	worse, the common parent may also be the Root. From that common		worse, the common parent may also be the Root. From that common
	parent, the packet will follow a path down the DODAG that is		parent, the packet will follow a path down the DODAG that is
	optimized for the Objective Function that was used to build the		optimized for the Objective Function that was used to build the
	DODAG.		DODAG.
	skipping to change at page 35, line 21 ¶		skipping to change at page 49, line 21 ¶
	+-----+		+-----+
	X		X
	^ v o o		^ v o o
	^ o o v o o o o o		^ o o v o o o o o
	^ o o o v o o o o o		^ o o o v o o o o o
	^ o o v o o o o o		^ o o v o o o o o
	S o o o D o o o		S o o o D o o o
	o o o o		o o o o
	LLN		LLN
	Figure 12: Routing Stretch between S and D via common parent X		Figure 13: Routing Stretch between S and D via common parent X
	It results that it is often beneficial to enable transversal P2P		It results that it is often beneficial to enable transversal P2P
	routes, either if the RPL route presents a stretch from shortest		routes, either if the RPL route presents a stretch from shortest
	path, or if the new route is engineered with a different objective,		path, or if the new route is engineered with a different objective,
	and that it is even more critical in Non-Storing Mode than it is in		and that it is even more critical in Non-Storing Mode than it is in
	Storing Mode, because the routing stretch is wider. For that reason,		Storing Mode, because the routing stretch is wider. For that reason,
	earlier work at the IETF introduced the "Reactive Discovery of		earlier work at the IETF introduced the "Reactive Discovery of
	Point-to-Point Routes in Low Power and Lossy Networks" [RFC6997],		Point-to-Point Routes in Low Power and Lossy Networks" [RFC6997],
	which specifies a distributed method for establishing optimized P2P		which specifies a distributed method for establishing optimized P2P
	routes. This draft proposes an alternate based on a centralized		routes. This draft proposes an alternate based on a centralized
	skipping to change at page 35, line 50 ¶		skipping to change at page 49, line 50 ¶
	+-----+		+-----+
	|		|
	o o o o		o o o o
	o o o o o o o o o		o o o o o o o o o
	o o o o o o o o o o		o o o o o o o o o o
	o o o o o o o o o		o o o o o o o o o
	S>>A>>>B>>C>>>D o o o		S>>A>>>B>>C>>>D o o o
	o o o o		o o o o
	LLN		LLN
	Figure 13: Projected Transversal Route		Figure 14: Projected Transversal Route
	This specification enables to store source-routed or Storing Mode		This specification enables to store source-routed or Storing Mode
	state in intermediate routers, which enables to limit the stretch of		state in intermediate routers, which enables to limit the stretch of
	a P2P route and maintain the characteristics within a given SLA. An		a P2P route and maintain the characteristics within a given SLA. An
	example of service using this mechanism oculd be a control loop that		example of service using this mechanism oculd be a control loop that
	would be installed in a network that uses classical RPL for		would be installed in a network that uses classical RPL for
	asynchronous data collection. In that case, the P2P path may be		asynchronous data collection. In that case, the P2P path may be
	installed in a different RPL Instance, with a different objective		installed in a different RPL Instance, with a different objective
	function.		function.
End of changes. 112 change blocks.
	282 lines changed or deleted		899 lines changed or added
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