draft-ietf-roll-turnon-rfc8138-10.txt		draft-ietf-roll-turnon-rfc8138-11.txt
	ROLL P. Thubert, Ed.		ROLL P. Thubert, Ed.
	Internet-Draft L. Zhao		Internet-Draft L. Zhao
	Updates: 8138 (if approved) Cisco Systems		Updates: 8138 (if approved) Cisco Systems
	Intended status: Standards Track 5 August 2020		Intended status: Standards Track 27 August 2020
	Expires: 6 February 2021		Expires: 28 February 2021
	A RPL DODAG Configuration Option for the 6LoWPAN Routing Header		A RPL DODAG Configuration Option for the 6LoWPAN Routing Header
	draft-ietf-roll-turnon-rfc8138-10		draft-ietf-roll-turnon-rfc8138-11
	Abstract		Abstract
	This document updates RFC 8138 by defining a bit in the RPL DODAG		This document updates RFC 8138 by defining a bit in the RPL DODAG
	Configuration Option to indicate whether compression is used within		Configuration Option to indicate whether compression is used within
	the RPL Instance, and specify the behavior of RFC 8138-capable nodes		the RPL Instance, and specify the behavior of RFC 8138-capable nodes
	when the bit is set and reset.		when the bit is set and reset.
	Status of This Memo		Status of This Memo
	skipping to change at page 1, line 34 ¶		skipping to change at page 1, line 34 ¶
	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 6 February 2021.		This Internet-Draft will expire on 28 February 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2020 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 29 ¶		skipping to change at page 2, line 29 ¶
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 7		7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8		8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
	9. Normative References . . . . . . . . . . . . . . . . . . . . 8		9. Normative References . . . . . . . . . . . . . . . . . . . . 8
	10. Informative References . . . . . . . . . . . . . . . . . . . 9		10. Informative References . . . . . . . . . . . . . . . . . . . 9
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
	1. Introduction		1. Introduction
	The packet compression technique defined in [RFC8138] can only be		The packet compression technique defined in [RFC8138] can only be
	activated in a RPL [RFC6550] network when all the nodes support it.		activated in a RPL [RFC6550] network when all the nodes support it.
	Otherwise, a non-capable node acting as leaf-only would fail to		Otherwise, if acting as a leaf, a node that does not support the
	communicate, and acting as a router it would drop the compressed		compression would fail to communicate; if acting as a router it would
	packets and black-hole a portion of the network.		drop the compressed packets and black-hole a portion of the network.
	The original idea was to use a flag day but that proved impractical		The original idea was to use a flag day but that proved impractical
	in a number of situations such as a large metering network that is		in a number of situations such as a large metering network that is
	used in production and incurs financial losses when interrupted.		used in production and incurs financial losses when interrupted.
	This specification is designed for the scenario where a live network		This specification is designed for the scenario where a live network
	is upgraded to support [RFC8138]. During the migration, the		is upgraded to support [RFC8138]. During the migration, the
	compression should remain inactive, until all nodes are upgraded.		compression should remain inactive, until all nodes are upgraded.
	This document complements [RFC8138] and dedicates a flag in the RPL		This document complements [RFC8138] and dedicates a flag in the RPL
	DODAG Configuration Option to indicate whether the [RFC8138]		DODAG Configuration Option to indicate whether the [RFC8138]
	compression should be used within the RPL DODAG.		compression should be used within the RPL DODAG.
	The setting of this new flag is controlled by the Root and propagates		The setting of this new flag is controlled by the Root and propagates
	as is in the whole network as part of the normal RPL signaling.		as is in the whole network as part of the normal RPL signaling.
	The idea is to use the flag to maintain the compression inactive		The flag is cleared to maintain the compression inactive during the
	during the migration phase. When the migration is complete (e.g., as		migration phase. When the migration is complete (e.g., as known by
	known by network management and/or inventory), the flag is set and		network management and/or inventory), the flag is set and the
	the compression is globally activated in the whole DODAG.		compression is globally activated in the whole DODAG.
	2. Terminology		2. Terminology
	2.1. References		2.1. References
	The terminology used in this document is consistent with and		The terminology used in this document is consistent with and
	incorporates that described in "Terms Used in Routing for Low-Power		incorporates that described in "Terms Used in Routing for Low-Power
	and Lossy Networks (LLNs)" [RFC7102]. Other terms in use in LLNs are		and Lossy Networks (LLNs)" [RFC7102]. Other terms in use in LLNs are
	found in "Terminology for Constrained-Node Networks" [RFC7228].		found in "Terminology for Constrained-Node Networks" [RFC7228].
	skipping to change at page 4, line 29 ¶		skipping to change at page 4, line 29 ¶
	Information Object (DIO) message. The DIO message propagates down		Information Object (DIO) message. The DIO message propagates down
	the DODAG to form and then maintain its structure. The DODAG		the DODAG to form and then maintain its structure. The DODAG
	Configuration Option is copied unmodified from parents to children.		Configuration Option is copied unmodified from parents to children.
	As shown in Figure 1, the DODAG Configuration Option was designed		As shown in Figure 1, the DODAG Configuration Option was designed
	with 4 bit positions reserved for future use as Flags.		with 4 bit positions reserved for future use as Flags.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type = 0x04 |Opt Length = 14| Flags |A| ... |		| Type = 0x04 |Opt Length = 14| | |T| |A| ... |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
	| ... |		| <- Flags -> ... |
	Figure 1: DODAG Configuration Option (Partial View)		Figure 1: DODAG Configuration Option (Partial View)
	This specification defines a new flag "Enable RFC8138 Compression"		This specification defines a new flag "Enable RFC8138 Compression"
	(T). The "T" flag is set to turn-on the use of the compression of		(T). The "T" flag is set to turn-on the use of the compression of
	RPL artifacts with [RFC8138] within the DODAG. The new "T" flag is		RPL artifacts with [RFC8138] within the DODAG. The new "T" flag is
	encoded in the Flags field in the RPL DODAG Configuration Option.		encoded in position 2 of the reserved Flags field in the RPL DODAG
	The suggested bit position of the "T" flag is indicated in Section 6.		Configuration Option, and set to 0 in legacy implementations as
			specified in Section 6.7.6 of [RFC6550].
	[RFC6550] states, when referring to the DODAG Configuration Option,		[RFC6550] states, when referring to the DODAG Configuration Option,
	that "Nodes other than the DODAG Root MUST NOT modify this		that "Nodes other than the DODAG Root MUST NOT modify this
	information when propagating the DODAG Configuration option".		information when propagating the DODAG Configuration option".
	Therefore, a legacy parent propagates the "T" flag as set by the Root		Therefore, a legacy parent propagates the "T" flag as set by the Root
	whether it supports this specification or not. So when the "T" flag		whether it supports this specification or not. So when the "T" flag
	is set, it is transparently flooded to all the nodes in the DODAG.		is set, it is transparently flooded to all the nodes in the DODAG.
	Section 6.3.1 of [RFC6550] defines a 3-bit Mode of Operation (MOP) in		Section 6.3.1 of [RFC6550] defines a 3-bit Mode of Operation (MOP) in
	the DIO Base Object. This specification applies to MOP values 0 to		the DIO Base Object. This specification applies to MOP values 0 to
	6. For a MOP value of 7, the compression MUST be used by default		6. For a MOP value of 7, the compression MUST be used by default
	regardless of the setting of the "T" flag.		regardless of the setting of the "T" flag.
	4. Updating RFC 8138		4. Updating RFC 8138
	A node SHOULD source packets in the compressed form using [RFC8138]		A node SHOULD generate packets in the compressed form using [RFC8138]
	if and only if the "T" flag is set. This behaviour can be overridden		if and only if the "T" flag is set. This behavior can be overridden
	by e.g., configuration or network management. Overriding may be		by configuration or network management. Overriding may be needed
	needed e.g., to cope with a legacy implementation of the Root that		e.g., to turn on the compression in a network where all nodes support
	supports [RFC8138] but not this specification and cannot set the "T"		[RFC8138] but the Root does not support this specification and cannot
	flag.		set the "T" flag, or to disable it locally in case of a problem.
	The decision of using [RFC8138] is made by the originator of the		The decision to use [RFC8138] is made by the originator of the packet
	packet depending on its capabilities and its knowledge of the state		depending on its capabilities and its knowledge of the state of the
	of the "T" flag. A router that encapsulates a packet is the		"T" flag. A router encapsulating a packet is the originator of the
	originator of the resulting packet and is responsible to compress the		resulting packet and is responsible for compressing the outer headers
	outer headers with [RFC8138], but it MUST leave the encapsulated		with [RFC8138], but it MUST leave the encapsulated packet as is.
	packet as is.
	An external target [USEofRPLinfo] is not expected to support		An external target [USEofRPLinfo] is not expected to support
	[RFC8138]. In most cases, packets from and to an external target are		[RFC8138]. In most cases, packets to and from an external target are
	tunneled back and forth between the border router (referred to as		tunneled back and forth between the border router (referred to as
	6LR) that serves the external target and the Root, regardless of the		6LR) that serves the external target and the Root, regardless of the
	MOP used in the RPL DODAG. The inner packet is typically not		MOP used in the RPL DODAG. The inner packet is typically not
	compressed with [RFC8138], so for outgoing packets, the border router		compressed with [RFC8138], so for outgoing packets, the border router
	just needs to decapsulate the (compressed) outer header and forward		just needs to decapsulate the (compressed) outer header and forward
	the (uncompressed) inner packet towards the external target.		the (uncompressed) inner packet towards the external target.
	A router MUST uncompress a packet that is to be forwarded to an		A router MUST uncompress a packet that is to be forwarded to an
	external target. Otherwise, the router MUST forward the packet in		external target. Otherwise, the router MUST forward the packet in
	the form that the source used, either compressed or uncompressed.		the form that the source used, either compressed or uncompressed.
	A RUL [UNAWARE-LEAVES] is both a leaf and an external target. A RUL		A RUL [UNAWARE-LEAVES] is both a leaf and an external target. A RUL
	does not participate in RPL and depends on the parent router to		does not participate in RPL and depends on the parent router to
	obtain connectivity. In the case of a RUL, forwarding towards an		obtain connectivity. In the case of a RUL, forwarding towards an
	external target actually means delivering the packet.		external target actually means delivering the packet.
	5. Transition Scenarios		5. Transition Scenarios
	A node that supports [RFC8138] but not this specification can only be		A node that supports [RFC8138] but not this specification can only be
	used in an homogeneous network. Enabling the [RFC8138] compression		used in an homogeneous network. Enabling the [RFC8138] compression
	without a turn-on signaling requires a "flag day"; all nodes must be		without a turn-on signaling method requires a "flag day"; by which
	upgraded, and then the network can be rebooted with the [RFC8138]		time all nodes must be upgraded, and at which point the network can
	compression turned on.		be rebooted with the [RFC8138] compression turned on.
	The intent for this specification is to perform a migration once and		The intent for this specification is to perform a migration once and
	for all without the need for a flag day. In particular it is not the		for all without the need for a flag day. In particular it is not the
	intention to undo the setting of the "T" flag. Though it is possible		intention to undo the setting of the "T" flag. Though it is possible
	to roll back (see Section 5.3), adding nodes that do not support		to roll back (see Section 5.3), adding nodes that do not support
	[RFC8138] after a roll back may be problematic if the roll back did		[RFC8138] after a roll back may be problematic if the roll back did
	not fully complete.		not fully complete.
	5.1. Coexistence		5.1. Coexistence
	A node that supports this specification can operate in a network with		A node that supports this specification can operate in a network with
	the [RFC8138] compression turned on or off with the "T" flag set		the [RFC8138] compression turned on or off with the "T" flag set
	accordingly and in a network in transition from off to on or on to		accordingly and in a network in transition from off to on or on to
	off (see Section 5.2).		off (see Section 5.2).
	A node that does not support [RFC8138] can interoperate with nodes		A node that does not support [RFC8138] can interoperate with nodes
	that do in a network with [RFC8138] compression turned off. If the		that do in a network with [RFC8138] compression turned off. If the
	compression is turned on, all the RPL-Aware Nodes are expected to be		compression is turned on, all the RPL-Aware Nodes are expected to be
	able to handle compressed packets in the compressed form. A node		able to handle compressed packets in the compressed form. A node
	that cannot do so may remain connected to the network as a RUL, but		that cannot do so may remain connected to the network as a RUL as
	how the node is modified to turn into a RUL is out of scope.		described in [UNAWARE-LEAVES].
	5.2. Inconsistent State While Migrating		5.2. Inconsistent State While Migrating
	When the "T" flag is turned on by the Root, the information slowly		When the "T" flag is turned on by the Root, the information slowly
	percolates through the DODAG as the DIO gets propagated. Some nodes		percolates through the DODAG as the DIO gets propagated. Some nodes
	will see the flag and start sourcing packets in the compressed form		will see the flag and start sourcing packets in the compressed form
	while other nodes in the same RPL DODAG are still not aware of it.		while other nodes in the same RPL DODAG are still not aware of it.
	In non-storing mode, the Root will start using [RFC8138] with a		In non-storing mode, the Root will start using [RFC8138] with a
	Source Routing Header 6LoRH (SRH-6LoRH) that routes all the way to		Source Routing Header 6LoRH (SRH-6LoRH) that routes all the way to
	the parent router or to the leaf.		the parent router or to the leaf.
	skipping to change at page 6, line 47 ¶		skipping to change at page 6, line 47 ¶
	of a RPL instance with multiple Roots, all nodes that participate to		of a RPL instance with multiple Roots, all nodes that participate to
	the RPL Instance may potentially join any DODAG. The network MUST be		the RPL Instance may potentially join any DODAG. The network MUST be
	operated with the "T" flag reset until all nodes in the RPL Instance		operated with the "T" flag reset until all nodes in the RPL Instance
	are upgraded to support this specification.		are upgraded to support this specification.
	5.3. Rolling Back		5.3. Rolling Back
	When turning [RFC8138] compression off in the network, the Network		When turning [RFC8138] compression off in the network, the Network
	Administrator MUST wait until all nodes have converged to the "T"		Administrator MUST wait until all nodes have converged to the "T"
	flag reset before allowing nodes that do not support the compression		flag reset before allowing nodes that do not support the compression
	in the network.		in the network. To that effect, whether the compression is active in
			a node SHOULD be exposed the node's management interface.
	It is RECOMMENDED to only deploy nodes that support [RFC8138] in a		It is RECOMMENDED to only deploy nodes that support [RFC8138] in a
	network where the compression is turned on. A node that does not		network where the compression is turned on. A node that does not
	support [RFC8138] MUST only be used as a RUL.		support [RFC8138] MUST only be used as a RUL.
	6. IANA Considerations		6. IANA Considerations
	IANA is requested to assign a new option flag from the Registry for		IANA is requested to assign a new option flag from the Registry for
	the "DODAG Configuration Option Flags" that was created for [RFC6550]		the "DODAG Configuration Option Flags" that was created for [RFC6550]
	as follows:		as follows:
	skipping to change at page 7, line 23 ¶		skipping to change at page 7, line 23 ¶
	+---------------+---------------------------------+-----------+		+---------------+---------------------------------+-----------+
	| 2 (suggested) | Turn on RFC8138 Compression (T) | THIS RFC |		| 2 (suggested) | Turn on RFC8138 Compression (T) | THIS RFC |
	+---------------+---------------------------------+-----------+		+---------------+---------------------------------+-----------+
	Table 1: New DODAG Configuration Option Flag		Table 1: New DODAG Configuration Option Flag
	7. Security Considerations		7. Security Considerations
	First of all, it is worth noting that with [RFC6550], every node in		First of all, it is worth noting that with [RFC6550], every node in
	the LLN that is RPL-aware can inject any RPL-based attack in the		the LLN that is RPL-aware can inject any RPL-based attack in the
	network. A trust model has to be put in place in an effort to		network. A trust model is REQUIRED in an effort to exclude rogue
	exclude rogue nodes from participating to the RPL and the 6LoWPAN		nodes from participating to the RPL and the 6LoWPAN signaling, as
	signaling, as well as from the data packet exchange. This trust		well as from the data packet exchange. This trust model could at a
	model could be at a minimum based on a Layer-2 Secure joining and the		minimum be based on a Layer-2 Secure joining and the Link-Layer
	Link-Layer security. This is a generic RPL and 6LoWPAN requirement,		security. This is a generic RPL and 6LoWPAN requirement, see Req5.1
	see Req5.1 in Appendix of [RFC8505].		in Appendix of [RFC8505].
	Setting the "T" flag before all routers are upgraded may cause a loss		Setting the "T" flag before all routers are upgraded may cause a loss
	of packets. The new bit is protected as the rest of the		of packets. The new bit is protected as the rest of the
	configuration so this is just one of the many attacks that can happen		configuration so this is just one of the many attacks that can happen
	if an attacker manages to inject a corrupted configuration.		if an attacker manages to inject a corrupted configuration.
	Setting and resetting the "T" flag may create inconsistencies in the		Setting and resetting the "T" flag may create inconsistencies in the
	network but as long as all nodes are upgraded to [RFC8138] support		network but as long as all nodes are upgraded to [RFC8138] support
	they will be able to forward both forms. The source is responsible		they will be able to forward both forms. The source is responsible
	for selecting whether the packet is compressed or not, and all		for selecting whether the packet is compressed or not, and all
	skipping to change at page 8, line 7 ¶		skipping to change at page 8, line 7 ¶
	"T" flag, so that nodes located downstream would compress when that		"T" flag, so that nodes located downstream would compress when that
	it is not desired, potentially resulting in the loss of packets. In		it is not desired, potentially resulting in the loss of packets. In
	a tree structure, the attacker would be in position to drop the		a tree structure, the attacker would be in position to drop the
	packets from and to the attacked nodes. So the attacks above would		packets from and to the attacked nodes. So the attacks above would
	be more complex and more visible than simply dropping selected		be more complex and more visible than simply dropping selected
	packets. The downstream node may have other parents and see both		packets. The downstream node may have other parents and see both
	settings, which could raise attention.		settings, which could raise attention.
	8. Acknowledgments		8. Acknowledgments
	The authors wish to thank Carles Gomez, Alvaro Retana, Dominique		The authors wish to thank Meral Shirazipour, Nagendra Kumar Nainar,
	Barthel and Rahul Jadhav for their in-depth reviews and constructive		Stewart Bryant, Carles Gomez, Alvaro Retana, Dominique Barthel and
	suggestions.		Rahul Jadhav for their in-depth reviews and constructive suggestions.
	Also many thanks to Michael Richardson for being always helpful and		Also many thanks to Michael Richardson for being always helpful and
	responsive when need comes.		responsive when need comes.
	9. Normative References		9. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
End of changes. 16 change blocks.
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