< draft-ietf-roll-useofrplinfo-32.txt		draft-ietf-roll-useofrplinfo-33.txt >
	ROLL Working Group M. Robles		ROLL Working Group M. Robles
	Internet-Draft Aalto/UTN-FRM		Internet-Draft Aalto
	Updates: 6553, 6550, 8138 (if approved) M. Richardson		Updates: 6553, 6550, 8138 (if approved) M. Richardson
	Intended status: Standards Track SSW		Intended status: Standards Track SSW
	Expires: May 7, 2020 P. Thubert		Expires: June 15, 2020 P. Thubert
	Cisco		Cisco
	November 4, 2019		December 13, 2019
	Using RPL Option Type, Routing Header for Source Routes and IPv6-in-IPv6		Using RPI Option Type, Routing Header for Source Routes and IPv6-in-IPv6
	encapsulation in the RPL Data Plane		encapsulation in the RPL Data Plane
	draft-ietf-roll-useofrplinfo-32		draft-ietf-roll-useofrplinfo-33
	Abstract		Abstract
	This document looks at different data flows through LLN (Low-Power		This document looks at different data flows through LLN (Low-Power
	and Lossy Networks) where RPL (IPv6 Routing Protocol for Low-Power		and Lossy Networks) where RPL (IPv6 Routing Protocol for Low-Power
	and Lossy Networks) is used to establish routing. The document		and Lossy Networks) is used to establish routing. The document
	enumerates the cases where RFC6553 (RPL Option Type), RFC6554		enumerates the cases where RFC6553 (RPI Option Type), RFC6554
	(Routing Header for Source Routes) and IPv6-in-IPv6 encapsulation is		(Routing Header for Source Routes) and IPv6-in-IPv6 encapsulation is
	required in data plane. This analysis provides the basis on which to		required in data plane. This analysis provides the basis on which to
	design efficient compression of these headers. This document updates		design efficient compression of these headers. This document updates
	RFC6553 adding a change to the RPL Option Type. Additionally, this		RFC6553 adding a change to the RPI Option Type. Additionally, this
	document updates RFC6550 defining a flag in the DIO Configuration		document updates RFC6550 defining a flag in the DIO Configuration
	Option to indicate about this change and updates RFC8138 as well to		Option to indicate about this change and updates RFC8138 as well to
	consider the new Option Type when the RPL Option is decompressed.		consider the new Option Type when the RPL Option is decompressed.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at 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 May 7, 2020.		This Internet-Draft will expire on June 15, 2020.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2019 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4		1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4
	2. Terminology and Requirements Language . . . . . . . . . . . . 4		2. Terminology and Requirements Language . . . . . . . . . . . . 5
	3. RPL Overview . . . . . . . . . . . . . . . . . . . . . . . . 6		3. RPL Overview . . . . . . . . . . . . . . . . . . . . . . . . 6
	4. Updates to RFC6553, RFC6550 and RFC8138 . . . . . . . . . . . 7		4. Updates to RFC6553, RFC6550 and RFC8138 . . . . . . . . . . . 7
	4.1. Updates to RFC6550: Advertise External Routes with Non-		4.1. Updates to RFC6550: Advertising External Routes with Non-
	Storing Mode Signaling. . . . . . . . . . . . . . . . . . 7		Storing Mode Signaling. . . . . . . . . . . . . . . . . . 7
	4.2. Updates to RFC6553: Indicating the new RPI value. . . . . 8		4.2. Updates to RFC6553: Indicating the new RPI Option Type. . 8
	4.3. Updates to RFC6550: Indicating the new RPI in the		4.3. Updates to RFC6550: Indicating the new RPI in the
	DODAG Configuration Option Flag. . . . . . . . . . . . . 11		DODAG Configuration Option Flag. . . . . . . . . . . . . 11
	4.4. Updates to RFC8138: Indicating the way to decompress with		4.4. Updates to RFC8138: Indicating the way to decompress with
	the new RPI value. . . . . . . . . . . . . . . . . . . . 12		the new RPI Option Type. . . . . . . . . . . . . . . . . 12
	5. Sample/reference topology . . . . . . . . . . . . . . . . . . 14		5. Sample/reference topology . . . . . . . . . . . . . . . . . . 14
	6. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 16		6. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 16
	7. Storing mode . . . . . . . . . . . . . . . . . . . . . . . . 19		7. Storing mode . . . . . . . . . . . . . . . . . . . . . . . . 19
	7.1. Storing Mode: Interaction between Leaf and Root . . . . . 20		7.1. Storing Mode: Interaction between Leaf and Root . . . . . 20
	7.1.1. SM: Example of Flow from RAL to root . . . . . . . . 21		7.1.1. SM: Example of Flow from RAL to root . . . . . . . . 21
	7.1.2. SM: Example of Flow from root to RAL . . . . . . . . 21		7.1.2. SM: Example of Flow from root to RAL . . . . . . . . 21
	7.1.3. SM: Example of Flow from root to RUL . . . . . . . . 22		7.1.3. SM: Example of Flow from root to RUL . . . . . . . . 22
	7.1.4. SM: Example of Flow from RUL to root . . . . . . . . 23		7.1.4. SM: Example of Flow from RUL to root . . . . . . . . 23
	7.2. SM: Interaction between Leaf and Internet. . . . . . . . 23		7.2. SM: Interaction between Leaf and Internet. . . . . . . . 23
	7.2.1. SM: Example of Flow from RAL to Internet . . . . . . 24		7.2.1. SM: Example of Flow from RAL to Internet . . . . . . 24
	skipping to change at page 3, line 33 ¶		skipping to change at page 3, line 33 ¶
	12. Security Considerations . . . . . . . . . . . . . . . . . . . 49		12. Security Considerations . . . . . . . . . . . . . . . . . . . 49
	13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 52		13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 52
	14. References . . . . . . . . . . . . . . . . . . . . . . . . . 52		14. References . . . . . . . . . . . . . . . . . . . . . . . . . 52
	14.1. Normative References . . . . . . . . . . . . . . . . . . 52		14.1. Normative References . . . . . . . . . . . . . . . . . . 52
	14.2. Informative References . . . . . . . . . . . . . . . . . 54		14.2. Informative References . . . . . . . . . . . . . . . . . 54
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 56		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 56
	1. Introduction		1. Introduction
	RPL (IPv6 Routing Protocol for Low-Power and Lossy Networks)		RPL (IPv6 Routing Protocol for Low-Power and Lossy Networks)
	[RFC6550] is a routing protocol for constrained networks. RFC6553		[RFC6550] is a routing protocol for constrained networks. [RFC6553]
	[RFC6553] defines the "RPL option" (RPL Packet Information or RPI),		defines the RPL Option carried within the IPv6 Hop-by-Hop Header to
	carried within the IPv6 Hop-by-Hop header to quickly identify		carry the RPLInstanceID and quickly identify inconsistencies (loops)
	inconsistencies (loops) in the routing topology. RFC6554 [RFC6554]		in the routing topology. The RPL Option is commonly referred to as
	defines the "RPL Source Route Header" (RH3), an IPv6 Extension Header		the RPL Packet Information (RPI) though the RPI is really the
	to deliver datagrams within a RPL routing domain, particularly in		abstract information that is defined in [RFC6550] and transported in
	non-storing mode.		the RPL Option. RFC6554 [RFC6554] defines the "RPL Source Route
			Header" (RH3), an IPv6 Extension Header to deliver datagrams within a
			RPL routing domain, particularly in non-storing mode.
	These various items are referred to as RPL artifacts, and they are		These various items are referred to as RPL artifacts, and they are
	seen on all of the data-plane traffic that occurs in RPL routed		seen on all of the data-plane traffic that occurs in RPL routed
	networks; they do not in general appear on the RPL control plane		networks; they do not in general appear on the RPL control plane
	traffic at all which is mostly hop-by-hop traffic (one exception		traffic at all which is mostly hop-by-hop traffic (one exception
	being DAO messages in non-storing mode).		being DAO messages in non-storing mode).
	It has become clear from attempts to do multi-vendor		It has become clear from attempts to do multi-vendor
	interoperability, and from a desire to compress as many of the above		interoperability, and from a desire to compress as many of the above
	artifacts as possible that not all implementers agree when artifacts		artifacts as possible that not all implementers agree when artifacts
	are necessary, or when they can be safely omitted, or removed.		are necessary, or when they can be safely omitted, or removed.
	The ROLL WG analysized how [RFC2460] rules apply to storing and non-		The ROLL WG analysized how [RFC2460] rules apply to storing and non-
	storing use of RPL. The result was 24 data plane use cases. They		storing use of RPL. The result was 24 data plane use cases. They
	are exhaustively outlined here in order to be completely unambiguous.		are exhaustively outlined here in order to be completely unambiguous.
	During the processing of this document, new rules were published as		During the processing of this document, new rules were published as
	[RFC8200], and this document was updated to reflect the normative		[RFC8200], and this document was updated to reflect the normative
	changes in that document.		changes in that document.
	This document updates RFC6553, changing the RPI option value to make		This document updates RFC6553, changing the value of the Option Type
	RFC8200 routers ignore this option by default.		of the RPL Option to make RFC8200 routers ignore this option when not
			recognized.
	A Routing Header Dispatch for 6LoWPAN (6LoRH)([RFC8138]) defines a		A Routing Header Dispatch for 6LoWPAN (6LoRH)([RFC8138]) defines a
	mechanism for compressing RPL Option information and Routing Header		mechanism for compressing RPL Option information and Routing Header
	type 3 (RH3) [RFC6554], as well as an efficient IPv6-in-IPv6		type 3 (RH3) [RFC6554], as well as an efficient IPv6-in-IPv6
	technique.		technique.
	Since some of the uses cases here described, use IPv6-in-IPv6		Since some of the uses cases here described, use IPv6-in-IPv6
	encapsulation. It MUST take in consideration, when encapsulation is		encapsulation. It MUST take in consideration, when encapsulation is
	applied, the RFC6040 [RFC6040], which defines how the explicit		applied, the RFC6040 [RFC6040], which defines how the explicit
	congestion notification (ECN) field of the IP header should be		congestion notification (ECN) field of the IP header should be
	skipping to change at page 4, line 44 ¶		skipping to change at page 4, line 47 ¶
	1.1. Overview		1.1. Overview
	The rest of the document is organized as follows: Section 2 describes		The rest of the document is organized as follows: Section 2 describes
	the used terminology. Section 3 provides a RPL Overview. Section 4		the used terminology. Section 3 provides a RPL Overview. Section 4
	describes the updates to RFC6553, RFC6550 and RFC 8138. Section 5		describes the updates to RFC6553, RFC6550 and RFC 8138. Section 5
	provides the reference topology used for the uses cases. Section 6		provides the reference topology used for the uses cases. Section 6
	describes the uses cases included. Section 7 describes the storing		describes the uses cases included. Section 7 describes the storing
	mode cases and section 8 the non-storing mode cases. Section 9		mode cases and section 8 the non-storing mode cases. Section 9
	describes the operational considerations of supporting RPL-unaware-		describes the operational considerations of supporting RPL-unaware-
	leaves. Section 10 depicts operational considerations for the		leaves. Section 10 depicts operational considerations for the
	proposed change on RPL Option type, section 11 the IANA		proposed change on RPI Option Type, section 11 the IANA
	considerations and then section 12 describes the security aspects.		considerations and then section 12 describes the security aspects.
	2. Terminology and Requirements Language		2. Terminology and Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in BCP		"OPTIONAL" in this document are to be interpreted as described in BCP
	14 [RFC2119] [RFC8174] when, and only when, they appear in all		14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	skipping to change at page 5, line 20 ¶		skipping to change at page 5, line 26 ¶
	RPL Leaf: An IPv6 host that is attached to a RPL router and obtains		RPL Leaf: An IPv6 host that is attached to a RPL router and obtains
	connectivity through a RPL Destination Oriented Directed Acyclic		connectivity through a RPL Destination Oriented Directed Acyclic
	Graph (DODAG). As an IPv6 node, a RPL Leaf is expected to ignore a		Graph (DODAG). As an IPv6 node, a RPL Leaf is expected to ignore a
	consumed Routing Header and as an IPv6 host, it is expected to ignore		consumed Routing Header and as an IPv6 host, it is expected to ignore
	a Hop-by-Hop header. It results that a RPL Leaf can correctly		a Hop-by-Hop header. It results that a RPL Leaf can correctly
	receive a packet with RPL artifacts. On the other hand, a RPL Leaf		receive a packet with RPL artifacts. On the other hand, a RPL Leaf
	is not expected to generate RPL artifacts or to support IP-in-IP		is not expected to generate RPL artifacts or to support IP-in-IP
	encapsulation. For simplification, this document uses the standalone		encapsulation. For simplification, this document uses the standalone
	term leaf to mean a RPL leaf.		term leaf to mean a RPL leaf.
			RPL Packet Information (RPI): The abstract information that [RFC6550]
			places in IP packets. The term is commonly used, including in this
			document, to refer to the RPL Option [RFC6553] that transports that
			abstract information in an IPv6 Hob-by-Hop Header.
	RPL-aware-node (RAN): A device which implements RPL. Please note		RPL-aware-node (RAN): A device which implements RPL. Please note
	that the device can be found inside the LLN or outside LLN.		that the device can be found inside the LLN or outside LLN.
	RPL-Aware-Leaf(RAL): A RPL-aware-node that is also a RPL Leaf.		RPL-Aware-Leaf(RAL): A RPL-aware-node that is also a RPL Leaf.
	RPL-unaware-node: A device which does not implement RPL, thus the		RPL-unaware-node: A device which does not implement RPL, thus the
	device is not-RPL-aware. Please note that the device can be found		device is not-RPL-aware. Please note that the device can be found
	inside the LLN.		inside the LLN.
	RPL-Unaware-Leaf(RUL): A RPL-unaware-node that is also a RPL Leaf.		RPL-Unaware-Leaf(RUL): A RPL-unaware-node that is also a RPL Leaf.
	skipping to change at page 5, line 41 ¶		skipping to change at page 6, line 4 ¶
	6LoWPAN Node (6LN): [RFC6775] defines it as: "A 6LoWPAN node is any		6LoWPAN Node (6LN): [RFC6775] defines it as: "A 6LoWPAN node is any
	host or router participating in a LoWPAN. This term is used when		host or router participating in a LoWPAN. This term is used when
	referring to situations in which either a host or router can play the		referring to situations in which either a host or router can play the
	role described.". In this document, a 6LN acts as a leaf.		role described.". In this document, a 6LN acts as a leaf.
	6LoWPAN Router (6LR): [RFC6775] defines it as:" An intermediate		6LoWPAN Router (6LR): [RFC6775] defines it as:" An intermediate
	router in the LoWPAN that is able to send and receive Router		router in the LoWPAN that is able to send and receive Router
	Advertisements (RAs) and Router Solicitations (RSs) as well as		Advertisements (RAs) and Router Solicitations (RSs) as well as
	forward and route IPv6 packets. 6LoWPAN routers are present only in		forward and route IPv6 packets. 6LoWPAN routers are present only in
	route-over topologies."		route-over topologies."
	6LoWPAN Border Router (6LBR): [RFC6775] defines it as:"A border		6LoWPAN Border Router (6LBR): [RFC6775] defines it as:"A border
	router located at the junction of separate 6LoWPAN networks or		router located at the junction of separate 6LoWPAN networks or
	between a 6LoWPAN network and another IP network. There may be one		between a 6LoWPAN network and another IP network. There may be one
	or more 6LBRs at the 6LoWPAN network boundary. A 6LBR is the		or more 6LBRs at the 6LoWPAN network boundary. A 6LBR is the
	responsible authority for IPv6 prefix propagation for the 6LoWPAN		responsible authority for IPv6 prefix propagation for the 6LoWPAN
	network it is serving. An isolated LoWPAN also contains a 6LBR in		network it is serving. An isolated LoWPAN also contains a 6LBR in
	the network, which provides the prefix(es) for the isolated network."		the network, which provides the prefix(es) for the isolated network."
	Flag Day: A transition that involves having a network with different		Flag Day: A transition that involves having a network with different
	values of RPL Option Type. Thus the network does not work correctly		values of RPI Option Type. Thus the network does not work correctly
	(Lack of interoperation).		(Lack of interoperation).
	Hop-by-hop re-encapsulation: The term "hop-by-hop re-encapsulation"		Hop-by-hop re-encapsulation: The term "hop-by-hop re-encapsulation"
	header refers to adding a header that originates from a node to an		header refers to adding a header that originates from a node to an
	adjacent node, using the addresses (usually the GUA or ULA, but could		adjacent node, using the addresses (usually the GUA or ULA, but could
	use the link-local addresses) of each node. If the packet must		use the link-local addresses) of each node. If the packet must
	traverse multiple hops, then it must be decapsulated at each hop, and		traverse multiple hops, then it must be decapsulated at each hop, and
	then re-encapsulated again in a similar fashion.		then re-encapsulated again in a similar fashion.
	Non-Storing Mode (Non-SM): RPL mode of operation in which the RPL-		Non-Storing Mode (Non-SM): RPL mode of operation in which the RPL-
	skipping to change at page 7, line 36 ¶		skipping to change at page 7, line 36 ¶
	RPL supports two modes of Downward traffic: in storing mode (SM), it		RPL supports two modes of Downward traffic: in storing mode (SM), it
	is fully stateful; in non-storing mode (Non-SM), it is fully source		is fully stateful; in non-storing mode (Non-SM), it is fully source
	routed. A RPL Instance is either fully storing or fully non-storing,		routed. A RPL Instance is either fully storing or fully non-storing,
	i.e. a RPL Instance with a combination of storing and non-storing		i.e. a RPL Instance with a combination of storing and non-storing
	nodes is not supported with the current specifications at the time of		nodes is not supported with the current specifications at the time of
	writing this document.		writing this document.
	4. Updates to RFC6553, RFC6550 and RFC8138		4. Updates to RFC6553, RFC6550 and RFC8138
	4.1. Updates to RFC6550: Advertise External Routes with Non-Storing		4.1. Updates to RFC6550: Advertising External Routes with Non-Storing
	Mode Signaling.		Mode Signaling.
	Section 6.7.8. of [RFC6550] introduces the 'E' flag that is set to		Section 6.7.8. of [RFC6550] introduces the 'E' flag that is set to
	indicate that the 6LR that generates the DAO redistributes external		indicate that the 6LR that generates the DAO redistributes external
	targets into the RPL network. An external Target is a Target that		targets into the RPL network. An external Target is a Target that
	has been learned through an alternate protocol, for instance a route		has been learned through an alternate protocol, for instance a route
	to a prefix that is outside the RPL domain but reachable via a 6LR.		to a prefix that is outside the RPL domain but reachable via a 6LR.
	Being outside of the RPL domain, a node that is reached via an		Being outside of the RPL domain, a node that is reached via an
	external target cannot be guaranteed to ignore the RPL artifacts and		external target cannot be guaranteed to ignore the RPL artifacts and
	cannot be expected to process the [RFC8138] compression correctly.		cannot be expected to process the [RFC8138] compression correctly.
	skipping to change at page 8, line 39 ¶		skipping to change at page 8, line 39 ¶
	by [RFC8504]. If the 6LN is a RUL, the Root that encapsulates a		by [RFC8504]. If the 6LN is a RUL, the Root that encapsulates a
	packet SHOULD terminate the tunnel at a parent 6LR unless it is aware		packet SHOULD terminate the tunnel at a parent 6LR unless it is aware
	that the RUL supports IP-in-IP decapsulation.		that the RUL supports IP-in-IP decapsulation.
	A node that is reachable over an external route is not expected to		A node that is reachable over an external route is not expected to
	support [RFC8138]. Whether a decapsulation took place or not and		support [RFC8138]. Whether a decapsulation took place or not and
	even when the 6LR is delivering the packet to a RUL, the 6LR that		even when the 6LR is delivering the packet to a RUL, the 6LR that
	injected an external route MUST uncompress the packet before		injected an external route MUST uncompress the packet before
	forwarding over that external route.		forwarding over that external route.
	4.2. Updates to RFC6553: Indicating the new RPI value.		4.2. Updates to RFC6553: Indicating the new RPI Option Type.
	This modification is required to be able to send, for example, IPv6		This modification is required to be able to send, for example, IPv6
	packets from a RPL-Aware-Leaf to a RPL-unaware node through Internet		packets from a RPL-Aware-Leaf to a RPL-unaware node through Internet
	(see Section 7.2.1), without requiring IPv6-in-IPv6 encapsulation.		(see Section 7.2.1), without requiring IPv6-in-IPv6 encapsulation.
	[RFC6553] (Section 6, Page 7) states as shown in Figure 2, that in		[RFC6553] (Section 6, Page 7) states as shown in Figure 2, that in
	the Option Type field of the RPL Option header, the two high order		the Option Type field of the RPL Option, the two high order bits must
	bits must be set to '01' and the third bit is equal to '1'. The		be set to '01' and the third bit is equal to '1'. The first two bits
	first two bits indicate that the IPv6 node must discard the packet if		indicate that the IPv6 node must discard the packet if it doesn't
	it doesn't recognize the option type, and the third bit indicates		recognize the Option Type, and the third bit indicates that the
	that the Option Data may change in route. The remaining bits serve		Option Data may change in route. The remaining bits serve as the
	as the option type.		Option Type.
	+-------+-------------------+----------------+-----------+		+-------+-------------------+----------------+-----------+
	| Hex | Binary Value | Description | Reference |		| Hex | Binary Value | Description | Reference |
	+ Value +-------------------+ + +		+ Value +-------------------+ + +
	| | act | chg | rest | | |		| | act | chg | rest | | |
	+-------+-----+-----+-------+----------------+-----------+		+-------+-----+-----+-------+----------------+-----------+
	| 0x63 | 01 | 1 | 00011 | RPL Option | [RFC6553] |		| 0x63 | 01 | 1 | 00011 | RPL Option | [RFC6553] |
	+-------+-----+-----+-------+----------------+-----------+		+-------+-----+-----+-------+----------------+-----------+
	Figure 2: Option Type in RPL Option.		Figure 2: Option Type in RPL Option.
	This document illustrates that is is not always possible to know for		This document illustrates that is is not always possible to know for
	sure at the source that a packet will only travel within the RPL		sure at the source that a packet will only travel within the RPL
	domain or may leave it.		domain or may leave it.
	At the time [RFC6553] was published, leaking a Hop-by-Hop header in		At the time [RFC6553] was published, leaking a Hop-by-Hop header in
	the outer IPv6 header chain could potentially impact core routers in		the outer IPv6 header chain could potentially impact core routers in
	the internet. So at that time, it was decided to encapsulate any		the internet. So at that time, it was decided to encapsulate any
	packet with a RPL option using IPv6-in-IPv6 in all cases where it was		packet with a RPL Option using IPv6-in-IPv6 in all cases where it was
	unclear whether the packet would remain within the RPL domain. In		unclear whether the packet would remain within the RPL domain. In
	the exception case where a packet would still leak, the Option Type		the exception case where a packet would still leak, the Option Type
	would ensure that the first router in the Internet that does not		would ensure that the first router in the Internet that does not
	recognize the option would drop the packet and protect the rest of		recognize the option would drop the packet and protect the rest of
	the network.		the network.
	Even with [RFC8138] that compresses the IPv6-in-IPv6 header, this		Even with [RFC8138] that compresses the IPv6-in-IPv6 header, this
	approach yields extra bytes in a packet which means consuming more		approach yields extra bytes in a packet which means consuming more
	energy, more bandwidth, incurring higher chances of loss and possibly		energy, more bandwidth, incurring higher chances of loss and possibly
	causing a fragmentation at the 6LoWPAN level. This impacts the daily		causing a fragmentation at the 6LoWPAN level. This impacts the daily
	operation of constrained devices for a case that generally does not		operation of constrained devices for a case that generally does not
	happen and would not heavily impact the core anyway.		happen and would not heavily impact the core anyway.
	While intention was and remains that the Hop-by-Hop header with a RPL		While intention was and remains that the Hop-by-Hop header with a RPL
	option should be confined within the RPL domain, this specification		Option should be confined within the RPL domain, this specification
	modifies this behavior in order to reduce the dependency on IPv6-in-		modifies this behavior in order to reduce the dependency on IPv6-in-
	IPv6 and protect the constrained devices. Section 4 of [RFC8200]		IPv6 and protect the constrained devices. Section 4 of [RFC8200]
	clarifies the behaviour of routers in the Internet as follows: "it is		clarifies the behaviour of routers in the Internet as follows: "it is
	now expected that nodes along a packet's delivery path only examine		now expected that nodes along a packet's delivery path only examine
	and process the Hop-by-Hop Options header if explicitly configured to		and process the Hop-by-Hop Options header if explicitly configured to
	do so".		do so".
	When unclear about the travel of a packet, it becomes preferable for		When unclear about the travel of a packet, it becomes preferable for
	a source not to encapsulate, accepting the fact that the packet may		a source not to encapsulate, accepting the fact that the packet may
	leave the RPL domain on its way to its destination. In that event,		leave the RPL domain on its way to its destination. In that event,
	the packet should reach its destination and should not be discarded		the packet should reach its destination and should not be discarded
	by the first node that does not recognize the RPL option. But with		by the first node that does not recognize the RPL Option. But with
	the current value of the Option Type, if a node in the Internet is		the current value of the Option Type, if a node in the Internet is
	configured to process the Hop-by-Hop header, and if such node		configured to process the Hop-by-Hop header, and if such node
	encounters an option with the first two bits set to 01 and conforms		encounters an option with the first two bits set to 01 and conforms
	to [RFC8200], it will drop the packet. Host systems should do the		to [RFC8200], it will drop the packet. Host systems should do the
	same, irrespective of the configuration.		same, irrespective of the configuration.
	Thus, this document updates the Option Type field to (Figure 3): the		Thus, this document updates the Option Type of the RPL Option
	two high order bits MUST be set to '00' and the third bit is equal to		[RFC6553], abusively naming it RPI Option Type for simplicity, to
	'1'. The first two bits indicate that the IPv6 node MUST skip over		(Figure 3): the two high order bits MUST be set to '00' and the third
	this option and continue processing the header ([RFC8200]		bit is equal to '1'. The first two bits indicate that the IPv6 node
	Section 4.2) if it doesn't recognize the option type, and the third		MUST skip over this option and continue processing the header
	bit continues to be set to indicate that the Option Data may change		([RFC8200] Section 4.2) if it doesn't recognize the Option Type, and
	en route. The remaining bits serve as the option type and remain as		the third bit continues to be set to indicate that the Option Data
	0x3. This ensures that a packet that leaves the RPL domain of an LLN		may change en route. The five rightmost bits remain at 0x3. This
	(or that leaves the LLN entirely) will not be discarded when it		ensures that a packet that leaves the RPL domain of an LLN (or that
	contains the [RFC6553] RPL Hop-by-Hop option known as RPI.		leaves the LLN entirely) will not be discarded when it contains the
			RPL Option.
	With the new Option Type, if an IPv6 (intermediate) node (RPL-not-		With the new Option Type, if an IPv6 (intermediate) node (RPL-not-
	capable) receives a packet with an RPL Option, it should ignore the		capable) receives a packet with an RPL Option, it should ignore the
	Hop-by-Hop RPL option (skip over this option and continue processing		Hop-by-Hop RPL Option (skip over this option and continue processing
	the header). This is relevant, as it was mentioned previously, in		the header). This is relevant, as it was mentioned previously, in
	the case that there is a flow from RAL to Internet (see		the case that there is a flow from RAL to Internet (see
	Section 7.2.1).		Section 7.2.1).
	This is a significant update to [RFC6553].		This is a significant update to [RFC6553].
	+-------+-------------------+-------------+------------+		+-------+-------------------+-------------+------------+
	| Hex | Binary Value | Description | Reference |		| Hex | Binary Value | Description | Reference |
	+ Value +-------------------+ + +		+ Value +-------------------+ + +
	| | act | chg | rest | | |		| | act | chg | rest | | |
	+-------+-----+-----+-------+-------------+------------+		+-------+-----+-----+-------+-------------+------------+
	| 0x23 | 00 | 1 | 00011 | RPL Option |[RFCXXXX](*)|		| 0x23 | 00 | 1 | 00011 | RPL Option |[RFCXXXX](*)|
	+-------+-----+-----+-------+-------------+------------+		+-------+-----+-----+-------+-------------+------------+
	Figure 3: Revised Option Type in RPL Option. (*)represents this		Figure 3: Revised Option Type in RPL Option. (*)represents this
	document		document
	Without the signaling described below, this change would otherwise		Without the signaling described below, this change would otherwise
	create a lack of interoperation (flag day) for existing networks		create a lack of interoperation (flag day) for existing networks
	which are currently using 0x63 as the RPI value. A move to 0x23 will		which are currently using 0x63 as the RPI Option Type value. A move
	not be understood by those networks. It is suggested that RPL		to 0x23 will not be understood by those networks. It is suggested
	implementations accept both 0x63 and 0x23 when processing the header.		that RPL implementations accept both 0x63 and 0x23 when processing
			the header.
	When forwarding packets, implementations SHOULD use the same value as		When forwarding packets, implementations SHOULD use the same value as
	it was received (This is required because, RPI type code can not be		it was received. This is required because, RPI Option Type can not
	changed by [RFC8200] - Section 4.2). It allows to the network to be		be changed by [RFC8200] - Section 4.2. It allows to the network to
	incrementally upgraded, and for the DODAG root to know which parts of		be incrementally upgraded, and for the DODAG root to know which parts
	the network are upgraded.		of the network are upgraded.
	When originating new packets, implementations SHOULD have an option		When originating new packets, implementations SHOULD have an option
	to determine which value to originate with, this option is controlled		to determine which value to originate with, this option is controlled
	by the DIO option described below.		by the DIO option described below.
	A network which is switching from straight 6LoWPAN compression		The change of RPI Option Type from 0x63 to 0x23, makes all [RFC8200]
	mechanism to those described in [RFC8138] will experience a flag day
	in the data compression anyway, and if possible this change can be
	deployed at the same time.
	The change of RPI option type from 0x63 to 0x23, makes all [RFC8200]
	Section 4.2 compliant nodes tolerant of the RPL artifacts. There is		Section 4.2 compliant nodes tolerant of the RPL artifacts. There is
	therefore no longer a necessity to remove the artifacts when sending		therefore no longer a necessity to remove the artifacts when sending
	traffic to the Internet. This change clarifies when to use an IPv6-		traffic to the Internet. This change clarifies when to use an IPv6-
	in-IPv6 header, and how to address them: The Hop-by-Hop Options		in-IPv6 header, and how to address them: The Hop-by-Hop Options
	Header containing the RPI option MUST always be added when 6LRs		Header containing the RPI MUST always be added when 6LRs originate
	originate packets (without IPv6-in-IPv6 headers), and IPv6-in-IPv6		packets (without IPv6-in-IPv6 headers), and IPv6-in-IPv6 headers MUST
	headers MUST always be added when a 6LR find that it needs to insert		always be added when a 6LR find that it needs to insert a Hop-by-Hop
	a Hop-by-Hop Options Header containing the RPI option. The IPv6-in-		Options Header containing the RPL Option. The IPv6-in-IPv6 header is
	IPv6 header is to be addressed to the RPL root when on the way up,		to be addressed to the RPL root when on the way up, and to the end-
	and to the end-host when on the way down.		host when on the way down.
	In the non-storing case, dealing with not-RPL aware leaf nodes is		In the non-storing case, dealing with not-RPL aware leaf nodes is
	much easier as the 6LBR (DODAG root) has complete knowledge about the		much easier as the 6LBR (DODAG root) has complete knowledge about the
	connectivity of all DODAG nodes, and all traffic flows through the		connectivity of all DODAG nodes, and all traffic flows through the
	root node.		root node.
	The 6LBR can recognize not-RPL aware leaf nodes because it will		The 6LBR can recognize not-RPL aware leaf nodes because it will
	receive a DAO about that node from the 6LR immediately above that		receive a DAO about that node from the 6LR immediately above that
	not-RPL aware node. This means that the non-storing mode case can		not-RPL aware node. This means that the non-storing mode case can
	avoid ever using hop-by-hop re-encapsulation headers for traffic		avoid ever using hop-by-hop re-encapsulation headers for traffic
	originating from the root to the leafs.		originating from the root to the leafs.
	The non-storing mode case does not require the type change from 0x63		The non-storing mode case does not require the type change from 0x63
	to 0x23, as the root can always create the right packet. The type		to 0x23, as the root can always create the right packet. The type
	change does not adversely affect the non-storing case.		change does not adversely affect the non-storing case.
	4.3. Updates to RFC6550: Indicating the new RPI in the DODAG		4.3. Updates to RFC6550: Indicating the new RPI in the DODAG
	Configuration Option Flag.		Configuration Option Flag.
	In order to avoid a Flag Day caused by lack of interoperation between		In order to avoid a Flag Day caused by lack of interoperation between
	new RPI (0x23) and old RPI (0x63) nodes, this section defines a flag		new RPI Option Type (0x23) and old RPI Option Type (0x63) nodes, this
	in the DIO Configuration Option, to indicate when then new RPI value		section defines a flag in the DIO Configuration Option, to indicate
	can be safely used. This means, the flag is going to indicate the		when then new RPI Option Type can be safely used. This means, the
	type of RPI that the network is using. Thus, when a node join to a		flag is going to indicate the value of Option Type that the network
	network will know which value to use. With this, RPL-capable nodes		is using for the RPL Option. Thus, when a node join to a network
	know if it is safe to use 0x23 when creating a new RPI. A node that		will know which value to use. With this, RPL-capable nodes know if
	forwards a packet with an RPI MUST NOT modify the option type of the		it is safe to use 0x23 when creating a new RPL Option. A node that
	RPI.		forwards a packet with an RPI MUST NOT modify the Option Type of the
			RPL Option.
	This is done via a DODAG Configuration Option flag which will		This is done using a DODAG Configuration Option flag which will
	propagate through the network. If the flag is received with a value		signal "RPI 0x23 enable" and propagate through the network.
	zero (which is the default), then new nodes will remain in RFC6553		Section 6.3.1. of [RFC6550] defines a 3-bit Mode of Operation (MOP)
	Compatible Mode; originating traffic with the old-RPI (0x63) value.		in the DIO Base Object. The flag is defined only for MOP value
			between 0 to 6. For a MOP value of 7 or above, the flag MAY indicate
			something different and MUST NOT be interpreted as "RPI 0x23 enable"
			unless the specification of the MOP indicates to do so.
	As stated in [RFC6550] the DODAG Configuration option is present in		As stated in [RFC6550] the DODAG Configuration option is present in
	DIO messages. The DODAG Configuration option distributes		DIO messages. The DODAG Configuration option distributes
	configuration information. It is generally static, and does not		configuration information. It is generally static, and does not
	change within the DODAG. This information is configured at the DODAG		change within the DODAG. This information is configured at the DODAG
	root and distributed throughout the DODAG with the DODAG		root and distributed throughout the DODAG with the DODAG
	Configuration option. Nodes other than the DODAG root do not modify		Configuration option. Nodes other than the DODAG root do not modify
	this information when propagating the DODAG Configuration option.		this information when propagating the DODAG Configuration option.
	The DODAG Configuration Option has a Flag field which is modified by		Currently, the DODAG Configuration Option in [RFC6550] states: "the
	this document. Currently, the DODAG Configuration Option in		unused bits MUST be initialize to zero by the sender and MUST be
	[RFC6550] states: "the unused bits MUST be initialize to zero by the		ignored by the receiver". If the flag is received with a value zero
	sender and MUST be ignored by the receiver".		(which is the default), then new nodes will remain in RFC6553
			Compatible Mode; originating traffic with the old-RPI Option Type
			(0x63) value. If the flag is received with a value of 1, then the
			option value for the RPL Option MUST be set to 0x23.
	Bit number three of the flag field in the DODAG Configuration option		Bit number three of the flag field in the DODAG Configuration option
	is to be used as shown in Figure 4 :		is to be used as shown in Figure 4 :
	+------------+-----------------+---------------+		+------------+-----------------+---------------+
	| Bit number | Description | Reference |		| Bit number | Description | Reference |
	+------------+-----------------+---------------+		+------------+-----------------+---------------+
	| 3 | RPI 0x23 enable | This document |		| 3 | RPI 0x23 enable | This document |
	+------------+-----------------+---------------+		+------------+-----------------+---------------+
	Figure 4: DODAG Configuration Option Flag to indicate the RPI-flag-		Figure 4: DODAG Configuration Option Flag to indicate the RPI-flag-
	day.		day.
	In case of rebooting, the node (6LN or 6LR) does not remember the RPL		In case of rebooting, the node (6LN or 6LR) does not remember the RPI
	Option Type, that is if the flag is set, so DIO messages sent by the		Option Type, that is if the flag is set, so DIO messages sent by the
	node would be set with the flag unset until a DIO message is received		node would be set with the flag unset until a DIO message is received
	with the flag set indicating the new RPI value. The node sets to		with the flag set indicating the new RPI Option Type. The node sets
	0x23 if the node supports this feature.		to 0x23 if the node supports this feature.
	4.4. Updates to RFC8138: Indicating the way to decompress with the new		4.4. Updates to RFC8138: Indicating the way to decompress with the new
	RPI value.		RPI Option Type.
	This modification is required to be able to decompress the RPL RPI		This modification is required to be able to decompress the RPL Option
	option with the new value (0x23).		with the new Option Type of 0x23.
	RPI-6LoRH header provides a compressed form for the RPL RPI [RFC8138]		RPI-6LoRH header provides a compressed form for the RPL RPI [RFC8138]
	in section 6. A node that is decompressing this header MUST		in section 6. A node that is decompressing this header MUST
	decompress using the RPL RPI option type that is currently active:		decompress using the RPI Option Type that is currently active: that
	that is, a choice between 0x23 (new) and 0x63 (old). The node will		is, a choice between 0x23 (new) and 0x63 (old). The node will know
	know which to use based upon the presence of the flag in the DODAG		which to use based upon the presence of the flag in the DODAG
	Configuration Option defined in Section 4.3. E.g. If the network is		Configuration Option defined in Section 4.3. E.g. If the network is
	in 0x23 mode (by DIO option), then it should be decompressed to 0x23.		in 0x23 mode (by DIO option), then it should be decompressed to 0x23.
	[RFC8138] section 7 documents how to compress the IPv6-in-IPv6		[RFC8138] section 7 documents how to compress the IPv6-in-IPv6
	header.		header.
	There are potential significant advantages to having a single code		There are potential significant advantages to having a single code
	path that always processes IPv6-in-IPv6 headers with no conditional		path that always processes IPv6-in-IPv6 headers with no conditional
	branches.		branches.
	In Storing Mode, for the examples of Flow from RAL to RUL and RUL to		In Storing Mode, for the examples of Flow from RAL to RUL and RUL to
	RUL comprise an IPv6-in-IPv6 and RPI compression headers. The use of		RUL comprise an IPv6-in-IPv6 and RPI compressed headers. The use of
	the IPv6-in-IPv6 header is MANDATORY in this case, and it SHOULD be		the IPv6-in-IPv6 header is MANDATORY in this case, and it SHOULD be
	compressed with [RFC8138] section 7. Figure 5 illustrates the case		compressed with [RFC8138] section 7. Figure 5 illustrates the case
	in Storing mode where the packet is received from the Internet, then		in Storing mode where the packet is received from the Internet, then
	the root encapsulates the packet to insert the RPI. In that example,		the root encapsulates the packet to insert the RPI. In that example,
	the leaf is not known to support RFC 8138, and the packet is		the leaf is not known to support RFC 8138, and the packet is
	encapsulated to the 6LR that is the parent and last hop to the final		encapsulated to the 6LR that is the parent and last hop to the final
	destination.		destination.
	+-+ ... -+-+ ... +-+- ... -+-+- +-+-+-+ ... +-+-+ ... -+++ ... +-...		+-+ ... -+-+ ... +-+- ... -+-+- +-+-+-+ ... +-+-+ ... -+++ ... +-...
	|11110001|SRH-6LoRH| RPI- |IP-in-IP| NH=1 |11110CPP| UDP | UDP		|11110001|SRH-6LoRH| RPI- |IP-in-IP| NH=1 |11110CPP| UDP | UDP
	skipping to change at page 16, line 11 ¶		skipping to change at page 16, line 11 ¶
	+-------+ +-------+ +------+ +-------+ +-------+		+-------+ +-------+ +------+ +-------+ +-------+
	Figure 6: A reference RPL Topology.		Figure 6: A reference RPL Topology.
	6. Use cases		6. Use cases
	In the data plane a combination of RFC6553, RFC6554 and IPv6-in-IPv6		In the data plane a combination of RFC6553, RFC6554 and IPv6-in-IPv6
	encapsulation are going to be analyzed for a number of representative		encapsulation are going to be analyzed for a number of representative
	traffic flows.		traffic flows.
	This document assumes that the LLN is using the no-drop RPI option		This document assumes that the LLN is using the no-drop RPI Option
	(0x23).		Type of 0x23.
	The use cases describe the communication in the following cases: -		The use cases describe the communication in the following cases: -
	Between RPL-aware-nodes with the root (6LBR) - Between RPL-aware-		Between RPL-aware-nodes with the root (6LBR) - Between RPL-aware-
	nodes with the Internet - Between RUL nodes within the LLN (e.g. see		nodes with the Internet - Between RUL nodes within the LLN (e.g. see
	Section 7.1.4) - Inside of the LLN when the final destination address		Section 7.1.4) - Inside of the LLN when the final destination address
	resides outside of the LLN (e.g. see Section 7.2.3).		resides outside of the LLN (e.g. see Section 7.2.3).
	The uses cases are as follows:		The uses cases are as follows:
	Interaction between Leaf and Root:		Interaction between Leaf and Root:
	skipping to change at page 17, line 18 ¶		skipping to change at page 17, line 18 ¶
	outlined in [RFC8200].		outlined in [RFC8200].
	As the rank information in the RPI artifact is changed at each hop,		As the rank information in the RPI artifact is changed at each hop,
	it will typically be zero when it arrives at the DODAG root. The		it will typically be zero when it arrives at the DODAG root. The
	DODAG root MUST force it to zero when passing the packet out to the		DODAG root MUST force it to zero when passing the packet out to the
	Internet. The Internet will therefore not see any SenderRank		Internet. The Internet will therefore not see any SenderRank
	information.		information.
	Despite being legal to leave the RPI artifact in place, an		Despite being legal to leave the RPI artifact in place, an
	intermediate router that needs to add an extension header (e.g. RH3		intermediate router that needs to add an extension header (e.g. RH3
	or RPI Option) MUST still encapsulate the packet in an (additional)		or RPL Option) MUST still encapsulate the packet in an (additional)
	outer IP header. The new header is placed after this new outer IP		outer IP header. The new header is placed after this new outer IP
	header.		header.
	A corollary is that an RH3 or RPI Option can only be removed by an		A corollary is that an RH3 or RPL Option can only be removed by an
	intermediate router if it is placed in an encapsulating IPv6 Header,		intermediate router if it is placed in an encapsulating IPv6 Header,
	which is addressed TO the intermediate router. When it does so, the		which is addressed TO the intermediate router. When it does so, the
	whole encapsulating header must be removed. (A replacement may be		whole encapsulating header must be removed. (A replacement may be
	added). This sometimes can result in outer IP headers being		added). This sometimes can result in outer IP headers being
	addressed to the next hop router using link-local address.		addressed to the next hop router using link-local address.
	Both RPI and RH3 headers may be modified in very specific ways by		Both the RPL Option and the RH3 headers may be modified in very
	routers on the path of the packet without the need to add and remove		specific ways by routers on the path of the packet without the need
	an encapsulating header. Both headers were designed with this		to add and remove an encapsulating header. Both headers were
	modification in mind, and both the RPL RH3 and the RPL option are		designed with this modification in mind, and both the RPL RH3 and the
	marked mutable but recoverable: so an IPsec AH security header can be		RPL Option are marked mutable but recoverable: so an IPsec AH
	applied across these headers, but it can not secure the values which		security header can be applied across these headers, but it can not
	mutate.		secure the values which mutate.
	RPI MUST be present in every single RPL data packet.		The RPI MUST be present in every single RPL data packet.
	Prior to [RFC8138], there was significant interest in removing the		Prior to [RFC8138], there was significant interest in removing the
	RPI for downward flows in non-storing mode. The exception covered a		RPI for downward flows in non-storing mode. The exception covered a
	very small number of cases, and causes significant interoperability		very small number of cases, and causes significant interoperability
	challenges, yet costed significant code and testing complexity. The		challenges, yet costed significant code and testing complexity. The
	ability to compress the RPI down to three bytes or less removes much		ability to compress the RPI down to three bytes or less removes much
	of the pressure to optimize this any further		of the pressure to optimize this any further
	[I-D.ietf-anima-autonomic-control-plane].		[I-D.ietf-anima-autonomic-control-plane].
	The earlier examples are more extensive to make sure that the process		The earlier examples are more extensive to make sure that the process
	is clear, while later examples are more concise.		is clear, while later examples are more concise.
	The uses cases are delineated based on the following requirements:		The uses cases are delineated based on the following requirements:
	The RPI option has to be in every packet that traverses the LLN.		The RPIhas to be in every packet that traverses the LLN.
	- Because of the previous requirement, packets from the Internet		- Because of the previous requirement, packets from the Internet
	have to be encapsulated.		have to be encapsulated.
	- A Header cannot be inserted or removed on the fly inside an IPv6		- A Header cannot be inserted or removed on the fly inside an IPv6
	packet that is being routed.		packet that is being routed.
	- Extension headers may not be added or removed except by the		- Extension headers may not be added or removed except by the
	sender or the receiver.		sender or the receiver.
	- RPI and RH3 headers may be modified by routers on the path of		- RPI and RH3 headers may be modified by routers on the path of
	the packet without the need to add and remove an encapsulating		the packet without the need to add and remove an encapsulating
	header.		header.
	- An RH3 or RPI Option can only be removed by an intermediate		- An RH3 or RPL Option can only be removed by an intermediate
	router if it is placed in an encapsulating IPv6 Header, which is		router if it is placed in an encapsulating IPv6 Header, which is
	addressed to the intermediate router.		addressed to the intermediate router.
	- Non-storing mode requires downstream encapsulation by root for		- Non-storing mode requires downstream encapsulation by root for
	RH3.		RH3.
	The uses cases are delineated based on the following assumptions:		The uses cases are delineated based on the following assumptions:
	This document assumes that the LLN is using the no-drop RPI option		This document assumes that the LLN is using the no-drop RPI Option
	(0x23).		Type (0x23).
	- Each IPv6 node (including Internet routers) obeys [RFC8200] RFC		- Each IPv6 node (including Internet routers) obeys [RFC8200] RFC
	8200, so that 0x23 RPI can be safely inserted.		8200, so that 0x23 RPI Option type can be safely inserted.
	- All 6LRs obey RFC 8200 [RFC8200].		- All 6LRs obey RFC 8200 [RFC8200].
	- The RPI is ignored at the IPv6 dst node (RUL).		- The RPI is ignored at the IPv6 dst node (RUL).
	- In the uses cases, we assume that the RAL supports IP-in-IP		- In the uses cases, we assume that the RAL supports IP-in-IP
	encapsulation.		encapsulation.
	- In the uses cases, we dont assume that the RUL supports IP-in-IP		- In the uses cases, we dont assume that the RUL supports IP-in-IP
	encapsulation.		encapsulation.
	skipping to change at page 19, line 23 ¶		skipping to change at page 19, line 23 ¶
	each of the following scenarios. It indicates if the IPv6-in-IPv6		each of the following scenarios. It indicates if the IPv6-in-IPv6
	header that is added, must be addressed to the final destination (the		header that is added, must be addressed to the final destination (the
	RAL node that is the target(tgt)), to the "root" or if a hop-by-hop		RAL node that is the target(tgt)), to the "root" or if a hop-by-hop
	header must be added (indicated by "hop"). In the hop-by-hop basis,		header must be added (indicated by "hop"). In the hop-by-hop basis,
	the destination address for the next hop is the link-layer address of		the destination address for the next hop is the link-layer address of
	the next hop.		the next hop.
	In cases where no IPv6-in-IPv6 header is needed, the column states as		In cases where no IPv6-in-IPv6 header is needed, the column states as
	"No". If the IPv6-in-IPv6 header is needed is a "must".		"No". If the IPv6-in-IPv6 header is needed is a "must".
	In all cases the RPI headers are needed, since it identifies		In all cases the RPI is needed, since it identifies inconsistencies
	inconsistencies (loops) in the routing topology. In all cases the		(loops) in the routing topology. In all cases the RH3 is not needed
	RH3 is not needed because it is not used in storing mode.		because it is not used in storing mode.
	In each case, 6LR_i are the intermediate routers from source to		In each case, 6LR_i are the intermediate routers from source to
	destination. "1 <= i <= n", n is the number of routers (6LR) that		destination. "1 <= i <= n", n is the number of routers (6LR) that
	the packet goes through from source (6LN) to destination.		the packet goes through from source (6LN) to destination.
	The leaf can be a router 6LR or a host, both indicated as 6LN. The		The leaf can be a router 6LR or a host, both indicated as 6LN. The
	root refers to the 6LBR (see Figure 6).		root refers to the 6LBR (see Figure 6).
	+---------------------+--------------+------------+------------------+		+---------------------+--------------+------------+------------------+
	| Interaction between | Use Case |IPv6-in-IPv6| IPv6-in-IPv6 dst |		| Interaction between | Use Case |IPv6-in-IPv6| IPv6-in-IPv6 dst |
	skipping to change at page 21, line 17 ¶		skipping to change at page 21, line 17 ¶
	In storing mode, RFC 6553 (RPI) is used to send RPL Information		In storing mode, RFC 6553 (RPI) is used to send RPL Information
	instanceID and rank information.		instanceID and rank information.
	In this case the flow comprises:		In this case the flow comprises:
	RAL (6LN) --> 6LR_i --> root(6LBR)		RAL (6LN) --> 6LR_i --> root(6LBR)
	For example, a communication flow could be: Node F --> Node D -->		For example, a communication flow could be: Node F --> Node D -->
	Node B --> Node A root(6LBR)		Node B --> Node A root(6LBR)
	The RAL (Node F) inserts the RPI header, and sends the packet to 6LR		The RAL (Node F) inserts the RPI, and sends the packet to 6LR (Node
	(Node D) which decrements the rank in RPI and sends the packet up.		D) which decrements the rank in the RPI and sends the packet up.
	When the packet arrives at 6LBR (Node A), the RPI is removed and the		When the packet arrives at 6LBR (Node A), the RPI is removed and the
	packet is processed.		packet is processed.
	No IPv6-in-IPv6 header is required.		No IPv6-in-IPv6 header is required.
	The RPI header can be removed by the 6LBR because the packet is		The RPI can be removed by the 6LBR because the packet is addressed to
	addressed to the 6LBR. The RAL must know that it is communicating		the 6LBR. The RAL must know that it is communicating with the 6LBR
	with the 6LBR to make use of this scenario. The RAL can know the		to make use of this scenario. The RAL can know the address of the
	address of the 6LBR because it knows the address of the root via the		6LBR because it knows the address of the root via the DODAGID in the
	DODAGID in the DIO messages.		DIO messages.
	The Table 1 summarizes what headers are needed for this use case.		The Table 1 summarizes what headers are needed for this use case.
	+-------------------+---------+-------+----------+		+-------------------+---------+-------+----------+
	| Header | RAL src | 6LR_i | 6LBR dst |		| Header | RAL src | 6LR_i | 6LBR dst |
	+-------------------+---------+-------+----------+		+-------------------+---------+-------+----------+
	| Inserted headers | RPI | -- | -- |		| Inserted headers | RPI | -- | -- |
	| Removed headers | -- | -- | RPI |		| Removed headers | -- | -- | RPI |
	| Re-added headers | -- | -- | -- |		| Re-added headers | -- | -- | -- |
	| Modified headers | -- | RPI | -- |		| Modified headers | -- | RPI | -- |
	skipping to change at page 22, line 4 ¶		skipping to change at page 22, line 4 ¶
	Table 1: SM: Summary of the use of headers from RAL to root		Table 1: SM: Summary of the use of headers from RAL to root
	7.1.2. SM: Example of Flow from root to RAL		7.1.2. SM: Example of Flow from root to RAL
	In this case the flow comprises:		In this case the flow comprises:
	root (6LBR) --> 6LR_i --> RAL (6LN)		root (6LBR) --> 6LR_i --> RAL (6LN)
	For example, a communication flow could be: Node A root(6LBR) -->		For example, a communication flow could be: Node A root(6LBR) -->
	Node B --> Node D --> Node F		Node B --> Node D --> Node F
	In this case the 6LBR inserts RPI header and sends the packet down,		In this case the 6LBR inserts RPI and sends the packet down, the 6LR
	the 6LR is going to increment the rank in RPI (it examines the		is going to increment the rank in RPI (it examines the instanceID to
	instanceID to identify the right forwarding table), the packet is		identify the right forwarding table), the packet is processed in the
	processed in the RAL and the RPI removed.		RAL and the RPI removed.
	No IPv6-in-IPv6 header is required.		No IPv6-in-IPv6 header is required.
	The Table 2 summarizes what headers are needed for this use case.		The Table 2 summarizes what headers are needed for this use case.
	+-------------------+----------+-------+---------+		+-------------------+----------+-------+---------+
	| Header | 6LBR src | 6LR_i | RAL dst |		| Header | 6LBR src | 6LR_i | RAL dst |
	+-------------------+----------+-------+---------+		+-------------------+----------+-------+---------+
	| Inserted headers | RPI | -- | -- |		| Inserted headers | RPI | -- | -- |
	| Removed headers | -- | -- | RPI |		| Removed headers | -- | -- | RPI |
	skipping to change at page 23, line 15 ¶		skipping to change at page 23, line 15 ¶
	7.1.4. SM: Example of Flow from RUL to root		7.1.4. SM: Example of Flow from RUL to root
	In this case the flow comprises:		In this case the flow comprises:
	RUL (IPv6 src node) --> 6LR_1 --> 6LR_i --> root (6LBR)		RUL (IPv6 src node) --> 6LR_1 --> 6LR_i --> root (6LBR)
	For example, a communication flow could be: Node G --> Node E -->		For example, a communication flow could be: Node G --> Node E -->
	Node B --> Node A root(6LBR)		Node B --> Node A root(6LBR)
	When the packet arrives from IPv6 node (Node G) to 6LR_1 (Node E),		When the packet arrives from IPv6 node (Node G) to 6LR_1 (Node E),
	the 6LR_1 will insert a RPI header, encapsulated in a IPv6-in-IPv6		the 6LR_1 will insert a RPI, encapsulated in a IPv6-in-IPv6 header.
	header. The IPv6-in-IPv6 header can be addressed to the next hop		The IPv6-in-IPv6 header can be addressed to the next hop (Node B), or
	(Node B), or to the root (Node A). The root removes the header and		to the root (Node A). The root removes the header and processes the
	processes the packet.		packet.
	The Figure 8 shows the table that summarizes what headers are needed		The Figure 8 shows the table that summarizes what headers are needed
	for this use case. [1] refers the case where the IPv6-in-IPv6 header		for this use case. [1] refers the case where the IPv6-in-IPv6 header
	is addressed to the next hop (Node B). [2] refers the case where the		is addressed to the next hop (Node B). [2] refers the case where the
	IPv6-in-IPv6 header is addressed to the root (Node A).		IPv6-in-IPv6 header is addressed to the root (Node A).
	+-----------+------+--------------+-----------------+------------------+		+-----------+------+--------------+-----------------+------------------+
	| Header | RUL | 6LR_1 | 6LR_i | 6LBR dst |		| Header | RUL | 6LR_1 | 6LR_i | 6LBR dst |
	| | src | | | |		| | src | | | |
	| | node | | | |		| | node | | | |
	skipping to change at page 25, line 4 ¶		skipping to change at page 25, line 4 ¶
	Table 4: SM: Summary of the use of headers from RAL to Internet		Table 4: SM: Summary of the use of headers from RAL to Internet
	7.2.2. SM: Example of Flow from Internet to RAL		7.2.2. SM: Example of Flow from Internet to RAL
	In this case the flow comprises:		In this case the flow comprises:
	Internet --> root (6LBR) --> 6LR_i --> RAL (6LN)		Internet --> root (6LBR) --> 6LR_i --> RAL (6LN)
	For example, a communication flow could be: Internet --> Node A		For example, a communication flow could be: Internet --> Node A
	root(6LBR) --> Node B --> Node D --> Node F		root(6LBR) --> Node B --> Node D --> Node F
	When the packet arrives from Internet to 6LBR the RPI header is added		When the packet arrives from Internet to 6LBR the RPI is added in a
	in a outer IPv6-in-IPv6 header (with the IPv6-in-IPv6 destination		outer IPv6-in-IPv6 header (with the IPv6-in-IPv6 destination address
	address set to the RAL) and sent to 6LR, which modifies the rank in		set to the RAL) and sent to 6LR, which modifies the rank in the RPI.
	the RPI. When the packet arrives at the RAL the RPI header is		When the packet arrives at the RAL the RPI is removed and the packet
	removed and the packet processed.		processed.
	The Figure 9 shows the table that summarizes what headers are needed		The Figure 9 shows the table that summarizes what headers are needed
	for this use case.		for this use case.
	+-----------+----------+--------------+--------------+--------------+		+-----------+----------+--------------+--------------+--------------+
	| Header | Internet | 6LBR | 6LR_i | RAL dst |		| Header | Internet | 6LBR | 6LR_i | RAL dst |
	| | src | | | |		| | src | | | |
	+-----------+----------+--------------+--------------+--------------+		+-----------+----------+--------------+--------------+--------------+
	| Inserted | -- | IP6-IP6(RPI) | -- | -- |		| Inserted | -- | IP6-IP6(RPI) | -- | -- |
	| headers | | | | |		| headers | | | | |
	skipping to change at page 25, line 46 ¶		skipping to change at page 25, line 46 ¶
	In this case the flow comprises:		In this case the flow comprises:
	RUL (IPv6 src node) --> 6LR_1 --> 6LR_i -->root (6LBR) --> Internet		RUL (IPv6 src node) --> 6LR_1 --> 6LR_i -->root (6LBR) --> Internet
	For example, a communication flow could be: Node G --> Node E -->		For example, a communication flow could be: Node G --> Node E -->
	Node B --> Node A root(6LBR) --> Internet		Node B --> Node A root(6LBR) --> Internet
	The 6LR_1 (i=1) node will add an IPv6-in-IPv6(RPI) header addressed		The 6LR_1 (i=1) node will add an IPv6-in-IPv6(RPI) header addressed
	either to the root, or hop-by-hop such that the root can remove the		either to the root, or hop-by-hop such that the root can remove the
	RPI header before passing upwards. The IPv6-in-IPv6 addressed to the		RPI before passing upwards. The IPv6-in-IPv6 addressed to the root
	root cause less processing overhead. On the other hand, with hop-by-		cause less processing overhead. On the other hand, with hop-by-hop
	hop the intermediate routers can check the routing tables for a		the intermediate routers can check the routing tables for a better
	better routing path, thus it could be more efficient and faster.		routing path, thus it could be more efficient and faster.
	Implementation should decide which approach to take.		Implementation should decide which approach to take.
	The originating node will ideally leave the IPv6 flow label as zero		The originating node will ideally leave the IPv6 flow label as zero
	so that the packet can be better compressed through the LLN. The		so that the packet can be better compressed through the LLN. The
	6LBR will set the flow label of the packet to a non-zero value when		6LBR will set the flow label of the packet to a non-zero value when
	sending to the Internet, for details check [RFC6437].		sending to the Internet, for details check [RFC6437].
	The Figure 10 shows the table that summarizes what headers are needed		The Figure 10 shows the table that summarizes what headers are needed
	for this use case. In the table, [1] shows the case when packet is		for this use case. In the table, [1] shows the case when packet is
	addressed to the root. [2] shows the case when the packet is		addressed to the root. [2] shows the case when the packet is
	skipping to change at page 26, line 48 ¶		skipping to change at page 26, line 48 ¶
	7.2.4. SM: Example of Flow from Internet to RUL.		7.2.4. SM: Example of Flow from Internet to RUL.
	In this case the flow comprises:		In this case the flow comprises:
	Internet --> root (6LBR) --> 6LR_i --> RUL (IPv6 dst node)		Internet --> root (6LBR) --> 6LR_i --> RUL (IPv6 dst node)
	For example, a communication flow could be: Internet --> Node A		For example, a communication flow could be: Internet --> Node A
	root(6LBR) --> Node B --> Node E --> Node G		root(6LBR) --> Node B --> Node E --> Node G
	The 6LBR will have to add an RPI header within an IPv6-in-IPv6		The 6LBR will have to add an RPI within an IPv6-in-IPv6 header. The
	header. The IPv6-in-IPv6 is addressed to the 6LR parent of the		IPv6-in-IPv6 is addressed to the 6LR parent of the 6lR_i.
	6lR_i.
	Further details about this are mentioned in		Further details about this are mentioned in
	[I-D.ietf-roll-unaware-leaves], which specifies RPL routing for a 6LN		[I-D.ietf-roll-unaware-leaves], which specifies RPL routing for a 6LN
	acting as a plain host and not being aware of RPL.		acting as a plain host and not being aware of RPL.
	The 6LBR may set the flow label on the inner IPv6-in-IPv6 header to		The 6LBR may set the flow label on the inner IPv6-in-IPv6 header to
	zero in order to aid in compression [RFC8138][RFC6437].		zero in order to aid in compression [RFC8138][RFC6437].
	The Figure 11 shows the table that summarizes what headers are needed		The Figure 11 shows the table that summarizes what headers are needed
	for this use case.		for this use case.
	skipping to change at page 30, line 44 ¶		skipping to change at page 30, line 44 ¶
	G) to the common parent (6LR_x) (Node B). In this case, 1 <= ia <=		G) to the common parent (6LR_x) (Node B). In this case, 1 <= ia <=
	n, n is the number of routers (6LR) that the packet goes through from		n, n is the number of routers (6LR) that the packet goes through from
	source to the common parent.		source to the common parent.
	6LR_id (Node D) are the intermediate routers from the common parent		6LR_id (Node D) are the intermediate routers from the common parent
	(6LR_x) (Node B) to destination RAL (Node F). In this case, 1 <= id		(6LR_x) (Node B) to destination RAL (Node F). In this case, 1 <= id
	<= m, m is the number of routers (6LR) that the packet goes through		<= m, m is the number of routers (6LR) that the packet goes through
	from the common parent (6LR_x) to the destination RAL.		from the common parent (6LR_x) to the destination RAL.
	The 6LR_ia (ia=1) (Node E) receives the packet from the RUL (Node G)		The 6LR_ia (ia=1) (Node E) receives the packet from the RUL (Node G)
	and inserts the RPI header encapsulated in a IPv6-in-IPv6 header.		and inserts the RPI encapsulated in a IPv6-in-IPv6 header. The IPv6-
	The IPv6-in-IPv6 header is addressed to the destination RAL (Node F).		in-IPv6 header is addressed to the destination RAL (Node F).
	The Figure 12 shows the table that summarizes what headers are needed		The Figure 12 shows the table that summarizes what headers are needed
	for this use case.		for this use case.
	+---------+-----+------------+-------------+-------------+------------+		+---------+-----+------------+-------------+-------------+------------+
	| Header |RUL | 6LR_ia | Common | 6LR_id | RAL |		| Header |RUL | 6LR_ia | Common | 6LR_id | RAL |
	| |src | | Parent | | dst |		| |src | | Parent | | dst |
	| |node | | (6LRx) | | |		| |node | | (6LRx) | | |
	+---------+-----+------------+-------------+-------------+------------+		+---------+-----+------------+-------------+-------------+------------+
	| Inserted| -- |IP6-IP6(RPI)| -- | -- | -- |		| Inserted| -- |IP6-IP6(RPI)| -- | -- | -- |
	skipping to change at page 31, line 51 ¶		skipping to change at page 31, line 51 ¶
	packet goes through from the RUL to the root.		packet goes through from the RUL to the root.
	6LR_id (Node C) are the intermediate routers from the root (Node A)		6LR_id (Node C) are the intermediate routers from the root (Node A)
	to the destination RUL dst node (Node J). In this case, 1 <= id <=		to the destination RUL dst node (Node J). In this case, 1 <= id <=
	m, m is the number of routers (6LR) that the packet goes through from		m, m is the number of routers (6LR) that the packet goes through from
	the root to destination RUL.		the root to destination RUL.
	The RPI is ignored at the RUL dst node.		The RPI is ignored at the RUL dst node.
	The 6LR_1 (Node E) receives the packet from the RUL (Node G) and		The 6LR_1 (Node E) receives the packet from the RUL (Node G) and
	inserts the RPI header (RPI), encapsulated in an IPv6-in-IPv6 header		inserts the RPI (RPI), encapsulated in an IPv6-in-IPv6 header
	directed to the root. The root removes the RPI and inserts a new RPI		directed to the root. The root removes the RPI and inserts a new RPI
	header addressed to the 6LR father of the RUL.		addressed to the 6LR father of the RUL.
	The Figure 13 shows the table that summarizes what headers are needed		The Figure 13 shows the table that summarizes what headers are needed
	for this use case.		for this use case.
	+---------+------+-------+-------+---------+-------+-------+		+---------+------+-------+-------+---------+-------+-------+
	| Header | RUL | 6LR_1 | 6LR_ia| 6LBR |6LR_id | RUL |		| Header | RUL | 6LR_1 | 6LR_ia| 6LBR |6LR_id | RUL |
	| | src | | | | | dst |		| | src | | | | | dst |
	| | node | | | | | node |		| | node | | | | | node |
	+---------+------+-------+-------+---------+-------+-------+		+---------+------+-------+-------+---------+-------+-------+
	| Inserted| -- |IP6-IP6|IP6-IP6| IP6-IP6 |IP6-IP6| -- |		| Inserted| -- |IP6-IP6|IP6-IP6| IP6-IP6 |IP6-IP6| -- |
	skipping to change at page 33, line 10 ¶		skipping to change at page 33, line 10 ¶
	header are to be inserted. It depicts the target destination address		header are to be inserted. It depicts the target destination address
	possible to a 6LN (indicated by "RAL"), to a 6LR (parent of a 6LN) or		possible to a 6LN (indicated by "RAL"), to a 6LR (parent of a 6LN) or
	to the root. In cases where no IPv6-in-IPv6 header is needed, the		to the root. In cases where no IPv6-in-IPv6 header is needed, the
	column states as "No". There is no expectation on RPL that RPI can		column states as "No". There is no expectation on RPL that RPI can
	be omitted, because it is needed for routing, quality of service and		be omitted, because it is needed for routing, quality of service and
	compression. This specification expects that is always a RPI		compression. This specification expects that is always a RPI
	Present.		Present.
	The leaf can be a router 6LR or a host, both indicated as 6LN		The leaf can be a router 6LR or a host, both indicated as 6LN
	(Figure 6). In the table (Figure 14) the (1) indicates a 6tisch case		(Figure 6). In the table (Figure 14) the (1) indicates a 6tisch case
	[RFC8180], where the RPI header may still be needed for the		[RFC8180], where the RPI may still be needed for the instanceID to be
	instanceID to be available for priority/channel selection at each		available for priority/channel selection at each hop.
	hop.
	+-----------------+--------------+-----+-----+------------+------------+		+-----------------+--------------+-----+-----+------------+------------+
	| Interaction | Use Case | RPI | RH3 |IPv6-in-IPv6|IPv6-in-IPv6|		| Interaction | Use Case | RPI | RH3 |IPv6-in-IPv6|IPv6-in-IPv6|
	| between | | | | | dst |		| between | | | | | dst |
	+-----------------+--------------+-----+-----+------------+------------+		+-----------------+--------------+-----+-----+------------+------------+
	| | RAL to root | Yes | No | No | No |		| | RAL to root | Yes | No | No | No |
	+ +--------------+-----+-----+------------+------------+		+ +--------------+-----+-----+------------+------------+
	| Leaf - Root | root to RAL | Yes | Yes | No | No |		| Leaf - Root | root to RAL | Yes | Yes | No | No |
	+ +--------------+-----+-----+------------+------------+		+ +--------------+-----+-----+------------+------------+
	| | root to RUL | Yes | Yes | must | 6LR |		| | root to RUL | Yes | Yes | must | 6LR |
	skipping to change at page 34, line 4 ¶		skipping to change at page 33, line 50 ¶
	| | RUL to RUL | Yes | Yes | must | root/6LR |		| | RUL to RUL | Yes | Yes | must | root/6LR |
	+-----------------+--------------+-----+-----+------------+------------+		+-----------------+--------------+-----+-----+------------+------------+
	Figure 14: Table that shows headers needed in Non-Storing mode: RPI,		Figure 14: Table that shows headers needed in Non-Storing mode: RPI,
	RH3, IPv6-in-IPv6 encapsulation.		RH3, IPv6-in-IPv6 encapsulation.
	8.1. Non-Storing Mode: Interaction between Leaf and Root		8.1. Non-Storing Mode: Interaction between Leaf and Root
	In this section is described the communication flow in Non Storing		In this section is described the communication flow in Non Storing
	Mode (Non-SM) between,		Mode (Non-SM) between,
	RAL to root
			RAL to root
	root to RAL		root to RAL
	RUL to root		RUL to root
	root to RUL		root to RUL
	8.1.1. Non-SM: Example of Flow from RAL to root		8.1.1. Non-SM: Example of Flow from RAL to root
	In non-storing mode the leaf node uses default routing to send		In non-storing mode the leaf node uses default routing to send
	traffic to the root. The RPI header must be included since it		traffic to the root. The RPI must be included since it contains the
	contains the rank information, which is used to avoid/detect loops.		rank information, which is used to avoid/detect loops.
	RAL (6LN) --> 6LR_i --> root(6LBR)		RAL (6LN) --> 6LR_i --> root(6LBR)
	For example, a communication flow could be: Node F --> Node D -->		For example, a communication flow could be: Node F --> Node D -->
	Node B --> Node A (root)		Node B --> Node A (root)
	6LR_i are the intermediate routers from source to destination. In		6LR_i are the intermediate routers from source to destination. In
	this case, "1 <= i <= n", n is the number of routers (6LR) that the		this case, "1 <= i <= n", n is the number of routers (6LR) that the
	packet goes through from source (RAL) to destination (6LBR).		packet goes through from source (RAL) to destination (6LBR).
	skipping to change at page 35, line 8 ¶		skipping to change at page 35, line 8 ¶
	In this case the flow comprises:		In this case the flow comprises:
	root (6LBR) --> 6LR_i --> RAL (6LN)		root (6LBR) --> 6LR_i --> RAL (6LN)
	For example, a communication flow could be: Node A (root) --> Node B		For example, a communication flow could be: Node A (root) --> Node B
	--> Node D --> Node F		--> Node D --> Node F
	6LR_i are the intermediate routers from source to destination. In		6LR_i are the intermediate routers from source to destination. In
	this case, "1 <= i <= n", n is the number of routers (6LR) that the		this case, "1 <= i <= n", n is the number of routers (6LR) that the
	packet goes through from source (6LBR) to destination (RAL).		packet goes through from source (6LBR) to destination (RAL).
	The 6LBR inserts an RH3, and a RPI header. No IPv6-in-IPv6 header is		The 6LBR inserts an RH3, and a RPI. No IPv6-in-IPv6 header is
	necessary as the traffic originates with an RPL aware node, the 6LBR.		necessary as the traffic originates with an RPL aware node, the 6LBR.
	The destination is known to be RPL-aware because the root knows the		The destination is known to be RPL-aware because the root knows the
	whole topology in non-storing mode.		whole topology in non-storing mode.
	The Table 8 summarizes what headers are needed for this use case.		The Table 8 summarizes what headers are needed for this use case.
	+-------------------+----------+-----------+-----------+		+-------------------+----------+-----------+-----------+
	| Header | 6LBR src | 6LR_i | RAL dst |		| Header | 6LBR src | 6LR_i | RAL dst |
	+-------------------+----------+-----------+-----------+		+-------------------+----------+-----------+-----------+
	| Inserted headers | RPI, RH3 | -- | -- |		| Inserted headers | RPI, RH3 | -- | -- |
	skipping to change at page 39, line 39 ¶		skipping to change at page 39, line 39 ¶
	For example, a communication flow could be: Node G --> Node E -->		For example, a communication flow could be: Node G --> Node E -->
	Node B --> Node A --> Internet		Node B --> Node A --> Internet
	6LR_i are the intermediate routers from source to destination. In		6LR_i are the intermediate routers from source to destination. In
	this case, "1 <= i <= n", n is the number of routers (6LR) that the		this case, "1 <= i <= n", n is the number of routers (6LR) that the
	packet goes through from source (RUL) to 6LBR, e.g. 6LR_1 (i=1).		packet goes through from source (RUL) to 6LBR, e.g. 6LR_1 (i=1).
	In this case the flow label is recommended to be zero in the IPv6		In this case the flow label is recommended to be zero in the IPv6
	node. As RPL headers are added in the IPv6 node packet, the first		node. As RPL headers are added in the IPv6 node packet, the first
	6LR (6LR_1) will add a RPI header inside a new IPv6-in-IPv6 header.		6LR (6LR_1) will add a RPI inside a new IPv6-in-IPv6 header. The
	The IPv6-in-IPv6 header will be addressed to the root. This case is		IPv6-in-IPv6 header will be addressed to the root. This case is
	identical to the storing-mode case (see Section 7.2.3).		identical to the storing-mode case (see Section 7.2.3).
	The Figure 17 shows the table that summarizes what headers are needed		The Figure 17 shows the table that summarizes what headers are needed
	for this use case.		for this use case.
	+---------+----+-------------+--------------+--------------+--------+		+---------+----+-------------+--------------+--------------+--------+
	| Header |RUL | 6LR_1 | 6LR_i | 6LBR |Internet|		| Header |RUL | 6LR_1 | 6LR_i | 6LBR |Internet|
	| |src | | [i=2,..,n] | | dst |		| |src | | [i=2,..,n] | | dst |
	| |node| | | | |		| |node| | | | |
	+---------+----+-------------+--------------+--------------+--------+		+---------+----+-------------+--------------+--------------+--------+
	skipping to change at page 42, line 13 ¶		skipping to change at page 42, line 13 ¶
	Node B --> Node A (root) --> Node B --> Node E --> Node H		Node B --> Node A (root) --> Node B --> Node E --> Node H
	6LR_ia are the intermediate routers from source to the root In this		6LR_ia are the intermediate routers from source to the root In this
	case, 1 <= ia <= n, n is the number of routers (6LR) that the packet		case, 1 <= ia <= n, n is the number of routers (6LR) that the packet
	goes through from RAL to the root.		goes through from RAL to the root.
	6LR_id are the intermediate routers from the root to the destination.		6LR_id are the intermediate routers from the root to the destination.
	In this case, "1 <= ia <= m", m is the number of the intermediate		In this case, "1 <= ia <= m", m is the number of the intermediate
	routers (6LR).		routers (6LR).
	This case involves only nodes in same RPL Domain. The originating		This case involves only nodes in same RPL Domain. The originating
	node will add a RPI header to the original packet, and send the		node will add a RPI to the original packet, and send the packet
	packet upwards.		upwards.
	The originating node must put the RPI (RPI1) into an IPv6-in-IPv6		The originating node must put the RPI (RPI1) into an IPv6-in-IPv6
	header addressed to the root, so that the 6LBR can remove that		header addressed to the root, so that the 6LBR can remove that
	header. If it does not, then additional resources are wasted on the		header. If it does not, then additional resources are wasted on the
	way down to carry the useless RPI option.		way down to carry the useless RPI.
	The 6LBR will need to insert an RH3 header, which requires that it		The 6LBR will need to insert an RH3 header, which requires that it
	add an IPv6-in-IPv6 header. It should be able to remove the		add an IPv6-in-IPv6 header. It should be able to remove the
	RPI(RPI1), as it was contained in an IPv6-in-IPv6 header addressed to		RPI(RPI1), as it was contained in an IPv6-in-IPv6 header addressed to
	it. Otherwise, there may be a RPI header buried inside the inner IP		it. Otherwise, there may be a RPI buried inside the inner IP header,
	header, which should get ignored. The root inserts a RPI (RPI2)		which should get ignored. The root inserts a RPI (RPI2) alongside
	alongside the RH3.		the RH3.
	Networks that use the RPL P2P extension [RFC6997] are essentially		Networks that use the RPL P2P extension [RFC6997] are essentially
	non-storing DODAGs and fall into this scenario or scenario		non-storing DODAGs and fall into this scenario or scenario
	Section 8.1.2, with the originating node acting as 6LBR.		Section 8.1.2, with the originating node acting as 6LBR.
	The Figure 19 shows the table that summarizes what headers are needed		The Figure 19 shows the table that summarizes what headers are needed
	for this use case.		for this use case.
	+---------+------------+----------+------------+----------+------------+		+---------+------------+----------+------------+----------+------------+
	| Header | RAL | 6LR_ia | 6LBR | 6LR_id | RAL |		| Header | RAL | 6LR_ia | 6LBR | 6LR_id | RAL |
	skipping to change at page 47, line 43 ¶		skipping to change at page 47, line 43 ¶
	could otherwise omit this unnecessary header if it was certain of the		could otherwise omit this unnecessary header if it was certain of the
	properties of the leaf.		properties of the leaf.
	As storing mode can not know the final path of the traffic,		As storing mode can not know the final path of the traffic,
	intolerant (that drop packets with RPL artifacts) leaf nodes can not		intolerant (that drop packets with RPL artifacts) leaf nodes can not
	be supported.		be supported.
	10. Operational considerations of introducing 0x23		10. Operational considerations of introducing 0x23
	This section describes the operational considerations of introducing		This section describes the operational considerations of introducing
	the new RPI value of 0x23.		the new RPI Option Type of 0x23.
	During bootstrapping the node gets the DIO with the information of		During bootstrapping the node gets the DIO with the information of
	RPL Option Type, indicating the new RPI in the DODAG Configuration		RPI Option Type, indicating the new RPI in the DODAG Configuration
	Option Flag. The DODAG root is in charge to configure the current		Option Flag. The DODAG root is in charge to configure the current
	network to the new value, through DIO messages and when all the nodes		network to the new value, through DIO messages and when all the nodes
	are set with the new value. The DODAG should change to a new DODAG		are set with the new value. The DODAG should change to a new DODAG
	version. In case of rebooting, the node does not remember the RPL		version. In case of rebooting, the node does not remember the RPI
	Option Type. Thus, the DIO is sent with a flag indicating the new		Option Type. Thus, the DIO is sent with a flag indicating the new
	RPI value.		RPI Option Type.
	The DODAG Configuration option is contained in a RPL DIO message,		The DODAG Configuration option is contained in a RPL DIO message,
	which contains a unique DTSN counter. The leaf nodes respond to this		which contains a unique DTSN counter. The leaf nodes respond to this
	message with DAO messages containing the same DTSN. This is a normal		message with DAO messages containing the same DTSN. This is a normal
	part of RPL routing; the RPL root therefore knows when the updated		part of RPL routing; the RPL root therefore knows when the updated
	DODAG Configuration Option has been seen by all nodes.		DODAG Configuration Option has been seen by all nodes.
	Before the migration happens, all the RPL-aware nodes should support		Before the migration happens, all the RPL-aware nodes should support
	both values . The migration procedure it is triggered when the DIO		both values . The migration procedure it is triggered when the DIO
	is sent with the flag indicating the new RPI value. Namely, it		is sent with the flag indicating the new RPI Option Type. Namely, it
	remains at 0x63 until it is sure that the network is capable of 0x23,		remains at 0x63 until it is sure that the network is capable of 0x23,
	then it abruptly change to 0x23. This options allows to send packets		then it abruptly change to 0x23. This options allows to send packets
	to not-RPL nodes, which should ignore the option and continue		to not-RPL nodes, which should ignore the option and continue
	processing the packets.		processing the packets.
	In case that a node join to a network that only process 0x63, it		In case that a node join to a network that only process 0x63, it
	would produce a flag day as was mentioned previously. Indicating the		would produce a flag day as was mentioned previously. Indicating the
	new RPI in the DODAG Configuration Option Flag is a way to avoid the		new RPI in the DODAG Configuration Option Flag is a way to avoid the
	flag day in a network. It is recommended that a network process both		flag day in a network. It is recommended that a network process both
	options to enable interoperability.		options to enable interoperability.
	skipping to change at page 51, line 14 ¶		skipping to change at page 51, line 14 ¶
	if the RH3 header has not been completely consumed. A consumed		if the RH3 header has not been completely consumed. A consumed
	(inert) RH3 header could be present in a packet that flows from one		(inert) RH3 header could be present in a packet that flows from one
	LLN, crosses the Internet, and enters another LLN. As per the		LLN, crosses the Internet, and enters another LLN. As per the
	discussion in this document, such headers do not need to be removed.		discussion in this document, such headers do not need to be removed.
	However, there is no case described in this document where an RH3 is		However, there is no case described in this document where an RH3 is
	inserted in a non-storing network on traffic that is leaving the LLN,		inserted in a non-storing network on traffic that is leaving the LLN,
	but this document should not preclude such a future innovation. It		but this document should not preclude such a future innovation. It
	should just be noted that an incoming RH3 must be fully consumed, or		should just be noted that an incoming RH3 must be fully consumed, or
	very carefully inspected.		very carefully inspected.
	The RPI header, if permitted to enter the LLN, could be used by an		The RPI, if permitted to enter the LLN, could be used by an attacker
	attacker to change the priority of a packet by selecting a different		to change the priority of a packet by selecting a different
	RPLInstanceID, perhaps one with a higher energy cost, for instance.		RPLInstanceID, perhaps one with a higher energy cost, for instance.
	It could also be that not all nodes are reachable in an LLN using the		It could also be that not all nodes are reachable in an LLN using the
	default instanceID, but a change of instanceID would permit an		default instanceID, but a change of instanceID would permit an
	attacker to bypass such filtering. Like the RH3, a RPI header is to		attacker to bypass such filtering. Like the RH3, a RPI is to be
	be inserted by the RPL root on traffic entering the LLN by first		inserted by the RPL root on traffic entering the LLN by first
	inserting an IPv6-in-IPv6 header. The attacker's RPI header		inserting an IPv6-in-IPv6 header. The attacker's RPI therefore will
	therefore will not be seen by the network. Upon reaching the		not be seen by the network. Upon reaching the destination node the
	destination node the RPI header has no further meaning and is just		RPI has no further meaning and is just skipped; the presence of a
	skipped; the presence of a second RPI header will have no meaning to		second RPI will have no meaning to the end node as the packet has
	the end node as the packet has already been identified as being at		already been identified as being at it's final destination.
	it's final destination.
	The RH3 and RPI headers could be abused by an attacker inside of the		The RH3 and RPIs could be abused by an attacker inside of the network
	network to route packets on non-obvious ways, perhaps eluding		to route packets on non-obvious ways, perhaps eluding observation.
	observation. This usage is in fact part of [RFC6997] and can not be		This usage is in fact part of [RFC6997] and can not be restricted at
	restricted at all. This is a feature, not a bug.		all. This is a feature, not a bug.
	[RFC7416] deals with many other threats to LLNs not directly related		[RFC7416] deals with many other threats to LLNs not directly related
	to the use of IPv6-in-IPv6 headers, and this document does not change		to the use of IPv6-in-IPv6 headers, and this document does not change
	that analysis.		that analysis.
	Nodes within the LLN can use the IPv6-in-IPv6 mechanism to mount an		Nodes within the LLN can use the IPv6-in-IPv6 mechanism to mount an
	attack on another part of the LLN, while disguising the origin of the		attack on another part of the LLN, while disguising the origin of the
	attack. The mechanism can even be abused to make it appear that the		attack. The mechanism can even be abused to make it appear that the
	attack is coming from outside the LLN, and unless countered, this		attack is coming from outside the LLN, and unless countered, this
	could be used to mount a Distributed Denial Of Service attack upon		could be used to mount a Distributed Denial Of Service attack upon
	skipping to change at page 54, line 45 ¶		skipping to change at page 54, line 41 ¶
	in progress), September 2019.		in progress), September 2019.
	[I-D.ietf-6tisch-dtsecurity-secure-join]		[I-D.ietf-6tisch-dtsecurity-secure-join]
	Richardson, M., "6tisch Secure Join protocol", draft-ietf-		Richardson, M., "6tisch Secure Join protocol", draft-ietf-
	6tisch-dtsecurity-secure-join-01 (work in progress),		6tisch-dtsecurity-secure-join-01 (work in progress),
	February 2017.		February 2017.
	[I-D.ietf-anima-autonomic-control-plane]		[I-D.ietf-anima-autonomic-control-plane]
	Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic		Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic
	Control Plane (ACP)", draft-ietf-anima-autonomic-control-		Control Plane (ACP)", draft-ietf-anima-autonomic-control-
	plane-20 (work in progress), July 2019.		plane-21 (work in progress), November 2019.
	[I-D.ietf-anima-bootstrapping-keyinfra]		[I-D.ietf-anima-bootstrapping-keyinfra]
	Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,		Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
	and K. Watsen, "Bootstrapping Remote Secure Key		and K. Watsen, "Bootstrapping Remote Secure Key
	Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-		Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
	keyinfra-29 (work in progress), October 2019.		keyinfra-30 (work in progress), November 2019.
	[I-D.ietf-intarea-tunnels]		[I-D.ietf-intarea-tunnels]
	Touch, J. and M. Townsley, "IP Tunnels in the Internet		Touch, J. and M. Townsley, "IP Tunnels in the Internet
	Architecture", draft-ietf-intarea-tunnels-10 (work in		Architecture", draft-ietf-intarea-tunnels-10 (work in
	progress), September 2019.		progress), September 2019.
	[I-D.ietf-roll-unaware-leaves]		[I-D.ietf-roll-unaware-leaves]
	Thubert, P. and M. Richardson, "Routing for RPL Leaves",		Thubert, P. and M. Richardson, "Routing for RPL Leaves",
	draft-ietf-roll-unaware-leaves-06 (work in progress),		draft-ietf-roll-unaware-leaves-07 (work in progress),
	November 2019.		November 2019.
	[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6		[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
	(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,		(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
	December 1998, <https://www.rfc-editor.org/info/rfc2460>.		December 1998, <https://www.rfc-editor.org/info/rfc2460>.
	[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in		[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
	IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,		IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
	December 1998, <https://www.rfc-editor.org/info/rfc2473>.		December 1998, <https://www.rfc-editor.org/info/rfc2473>.
	skipping to change at page 56, line 24 ¶		skipping to change at page 56, line 24 ¶
	May 2017, <https://www.rfc-editor.org/info/rfc8180>.		May 2017, <https://www.rfc-editor.org/info/rfc8180>.
	[RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.		[RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
	Perkins, "Registration Extensions for IPv6 over Low-Power		Perkins, "Registration Extensions for IPv6 over Low-Power
	Wireless Personal Area Network (6LoWPAN) Neighbor		Wireless Personal Area Network (6LoWPAN) Neighbor
	Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,		Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
	<https://www.rfc-editor.org/info/rfc8505>.		<https://www.rfc-editor.org/info/rfc8505>.
	Authors' Addresses		Authors' Addresses
	Maria Ines Robles		Maria Ines Robles
	Aalto University, Finland - / - Universidad Tecnologica Nacional - Facultad Regional Mendoza, Argentina		Aalto University, Finland
	Email: mariainesrobles@gmail.com		Email: mariainesrobles@gmail.com
	Michael C. Richardson		Michael C. Richardson
	Sandelman Software Works		Sandelman Software Works
	470 Dawson Avenue		470 Dawson Avenue
	Ottawa, ON K1Z 5V7		Ottawa, ON K1Z 5V7
	CA		CA
	Email: mcr+ietf@sandelman.ca		Email: mcr+ietf@sandelman.ca
	URI: http://www.sandelman.ca/mcr/		URI: http://www.sandelman.ca/mcr/
End of changes. 82 change blocks.
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