< draft-ietf-roll-turnon-rfc8138-02.txt		draft-ietf-roll-turnon-rfc8138-03.txt >
	ROLL P. Thubert, Ed.		ROLL P. Thubert, Ed.
	Internet-Draft L. Zhao		Internet-Draft L. Zhao
	Updates: 6550, 8138 (if approved) Cisco Systems		Updates: 6550, 8138 (if approved) Cisco Systems
	Intended status: Standards Track 12 December 2019		Intended status: Standards Track 22 January 2020
	Expires: 14 June 2020		Expires: 25 July 2020
	Configuration option for RFC 8138		Configuration option for RFC 8138
	draft-ietf-roll-turnon-rfc8138-02		draft-ietf-roll-turnon-rfc8138-03
	Abstract		Abstract
	This document complements RFC 8138 and dedicates a bit in the RPL		This document complements RFC 8138 and dedicates a bit in the RPL
	configuration option defined in RFC 6550 to indicate whether RFC 8138		configuration option defined in RFC 6550 to indicate whether RFC 8138
	compression is used within the RPL instance.		compression is used within the RPL Instance.
	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 14 June 2020.		This Internet-Draft will expire on 25 July 2020.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 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
	and restrictions with respect to this document. Code Components		and restrictions with respect to this document. Code Components
	extracted from this document must include Simplified BSD License text		extracted from this document must include Simplified BSD License text
	as described in Section 4.e of the Trust Legal Provisions and are		as described in Section 4.e of the Trust Legal Provisions and are
	provided without warranty as described in the Simplified BSD License.		provided without warranty as described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . 2		2. BCP 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
	3. Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . . 2		3. Updating RFC 6550 . . . . . . . . . . . . . . . . . . . . . . 2
	4. Updating RFC 8138 . . . . . . . . . . . . . . . . . . . . . . 3		4. Updating RFC 8138 . . . . . . . . . . . . . . . . . . . . . . 3
	5. Transition Scenarios . . . . . . . . . . . . . . . . . . . . 3		5. Transition Scenarios . . . . . . . . . . . . . . . . . . . . 3
	5.1. Inconsistent State While Migrating . . . . . . . . . . . 4		5.1. Inconsistent State While Migrating . . . . . . . . . . . 5
	5.2. Single Instance Scenario . . . . . . . . . . . . . . . . 5		5.2. Single RPL Instance Scenario . . . . . . . . . . . . . . 5
	5.3. Double Instance Scenario . . . . . . . . . . . . . . . . 6		5.3. Double RPL Instances Scenario . . . . . . . . . . . . . . 6
	5.4. Rolling Back . . . . . . . . . . . . . . . . . . . . . . 6		5.4. Rolling Back . . . . . . . . . . . . . . . . . . . . . . 6
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 7		7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7		8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
	9. Normative References . . . . . . . . . . . . . . . . . . . . 7		9. Normative References . . . . . . . . . . . . . . . . . . . . 7
	10. Informative References . . . . . . . . . . . . . . . . . . . 7		10. Informative References . . . . . . . . . . . . . . . . . . . 8
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	The transition to [RFC8138] in a network can only be done when all		The transition to [RFC8138] in a network can only be done when all
	nodes support the specification. In a mixed case with both		nodes support the specification. In a mixed case with both
	RFC8138-capable and non-capable nodes, the compression should be		RFC8138-capable and non-capable nodes, the compression should be
	turned off.		turned off.
	This document complements RFC 8138 and dedicates a bit in the RPL		This document complements RFC 8138 and dedicates a bit in the RPL
	configuration option to indicate whether RFC 8138 compression should		configuration option to indicate whether RFC 8138 compression should
	be used within the RPL instance. When the bit is not set, source		be used within the RPL Instance. When the bit is not set, source
	nodes that support RFC 8138 should refrain from using the compression		nodes that support RFC 8138 should refrain from using the compression
	unless the information is superseded by configuration.		unless the information is superseded by configuration.
	2. BCP 14		2. BCP 14
	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 3, line 41 ¶		skipping to change at page 3, line 41 ¶
	The decision of using RFC 8138 to compress a packet is made at the		The decision of using RFC 8138 to compress a packet is made at the
	source depending on its capabilities and its knowledge of the state		source depending on its capabilities and its knowledge of the state
	of the "T" flag. A router MUST forward the packet in the form that		of the "T" flag. A router MUST forward the packet in the form that
	the source used, either compressed or uncompressed. A router that		the source used, either compressed or uncompressed. A router that
	encapsulates a packet is the source of the resulting packet and the		encapsulates a packet is the source of the resulting packet and the
	rules above apply to it in that case.		rules above apply to it in that case.
	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 and an upgrade requires a "flag day"		used in a homogeneous network and an upgrade requires a "flag day"
	where all nodes are updated and then the network is rebooted with		where all nodes are updated and then the network is rebooted with
	implicitely RFC 8138 compression turned on with the "T" flag set on.		implicitly RFC 8138 compression turned on with the "T" flag set on.
	A node that supports this specification can work in a network with		A node that supports this specification can work in a network with
	RFC 8138 compression turned on or off with the "T" flag set		RFC 8138 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 5.1).		off (see Section 5.1).
	A node that does not support [RFC8138] can interoperate with a node		A node that does not support [RFC8138] can interoperate with a node
	that supports this specification in a network with RFC 8138		that supports this specification in a network with RFC 8138
	compression turned off. But it cannot forward compressed packets and		compression turned off. But it cannot forward compressed packets and
	therefore it cannot act as a router in a network with RFC 8138		therefore it cannot act as a router in a network with RFC 8138
	compression turned on. It may remain connected to that network as a		compression turned on. It may remain connected to that network as a
	leaf and generate uncompressed packets as long as imcoming packets		leaf and generate uncompressed packets. The leaf can receive packets
	are decapsulated by the parent and delivered in uncompressed form.		if they are delivered by the parent 6LR in the uncompressed form.
			This requires a knowledge by the 6LR that the leaf does not support
			RFC 8138. A RPL-Unaware-Leaf (RUL) [USEofRPLinfo] is an external
			target and by default is not expected to support RFC 8138.
	[RFC6550] states that "Nodes other than the DODAG root MUST NOT		[RFC6550] states that "Nodes other than the DODAG root MUST NOT
	modify this information when propagating the DODAG Configuration		modify this information when propagating the DODAG Configuration
	option". In other words, the configuration option is a way for the		option". In other words, the configuration option is a way for the
	root to configure the LLN nodes but it cannot be used by a parent to		root to configure the LLN nodes but it cannot be used by a parent to
	advertise its capabilities down the DODAG. It results whether a		advertise its capabilities down the DODAG. A parent propagates the
	parent supports RFC 8138 is not known by the child with the current		"T" flag as set whether it supports RFC 8138 or not. The setting of
	level of specifications, and a child cannot favor a parent based on a		the "T" flag can thus not be used as an indication of the support by
	particular support.		the sender, and a child cannot favor a parent based on it.
	Sections 8.5 and 9.2 of [RFC6550] also suggests that a RPL-aware node		Sections 8.5 and 9.2 of [RFC6550] also suggests that a RPL-aware node
	may attach to a DODAG as a leaf node only, e.g., when a node does not		may attach to a DODAG as a leaf node only, e.g., when a node does not
	support the Mode of Operation of a RPL Instance, the Objective		support the Mode of Operation of a RPL Instance, the Objective
	Function (OF) as indicated by the Objective Code Point (OCP) or some		Function (OF) as indicated by the Objective Code Point (OCP) or some
	other parameters in the configuration option. But the node is also		other parameters in the configuration option. [USEofRPLinfo]
	free to refrain from joining an Instance when a parameter is not		indicates that the node may also join as a RUL, in which case it
	suitable. This means that changing the OCP in a DODAG can be used to		refrains from participating to RPL and depends on the 6LR to ensure
	force nodes that do not support a particular feature to join as leaf		connectivity regardless on the way the RPL network is operated.
	only. This specification reiterates that a node that is configured
	to operate in an Instance but does not support a value for a known		This means that changing the OCP in a DODAG can be used to force
			nodes that do not support a particular feature to join as leaf only.
			This specification reiterates that a node that is configured to
			operate in a RPL Instance but does not support a value for a known
	parameter that is mandatory for routing MUST NOT operate as a router		parameter that is mandatory for routing MUST NOT operate as a router
	but MAY still joins as a leaf. Note that a legacy node will not		but MAY still join as a leaf. Note that a legacy node will not
	recognize when a reserved field is now used and will not turn to a		recognize when a reserved field is now used and will not turn to a
	leaf when that happens.		leaf when that happens.
	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, and though it is		intention to undo the setting of the "T" flag, and though it is
	possible to roll back (see Section 5.4), adding nodes that do not		possible to roll back (see Section 5.4), adding nodes that do not
	support [RFC8138] after a roll back may be problematic if the roll		support [RFC8138] after a roll back may be problematic if the roll
	back is not fully complete (see caveats in Section 5.2).		back is not fully complete (see caveats in Section 5.2).
	5.1. Inconsistent State While Migrating		5.1. Inconsistent State While Migrating
	When the "T" flag is turned on in the configuration option by the		When the "T" flag is turned on in the configuration option by the
	root, the information slowly percolates through the DODAG as the DIO		root, the information slowly percolates through the DODAG as the DIO
	gets propagated. Some nodes will see the flag and start sourcing		gets propagated. Some nodes will see the flag and start sourcing
	packets in the compressed form while other nodes in the same instance		packets in the compressed form while other nodes in the same RPL
	are still not aware of it. Conversely, in non-storing mode, the root		Instance are still not aware of it. Conversely, in non-storing mode,
	will start using RFC 8138 with a SRH-6LoRH that routes all the way to		the root will start using RFC 8138 with a SRH-6LoRH that routes all
	the last router or possibly to the leaf, if the leaf supports RFC		the way to the last router or possibly to the leaf, if the leaf
	8138.		supports RFC 8138.
	This is why it is required that all the routers in the Instance		This is why it is required that all the routers in the RPL Instance
	support [RFC8138] at the time of the switch, and all nodes that do		support [RFC8138] at the time of the switch, and all nodes that do
	not support [RFC8138] only operate as leaves.		not support [RFC8138] only operate as leaves.
	Setting the "T" flag is ultimately the responsibility of the network		Setting the "T" flag is ultimately the responsibility of the network
	administrator. In a case of upgrading a network to turn the		administrator. In a case of upgrading a network to turn the
	compression on, the network SHOULD be operated with the "T" flag		compression on, the network SHOULD be operated with the "T" flag
	reset until all targeted nodes are upgraded to support this		reset until all targeted nodes are upgraded to support this
	specification. Section 5.2 and Section 5.3 provide possible		specification. Section 5.2 and Section 5.3 provide possible
	transition scenarios where this can be enforced.		transition scenarios where this can be enforced.
	5.2. Single Instance Scenario		5.2. Single RPL Instance Scenario
	In a single instance scenario, nodes that support RFC 8138 are		In a Single RPL Instance Scenario, nodes that support RFC 8138 are
	configured with a new OCP, that may use the same OF operation or a		configured with a new OCP, that may use the same OF operation or a
	variation of it. when it finally sets the "T" flag, the root also		variation of it. The root sets the "T" flag at the time it migrates
	migrates to the new OCP. As a result, nodes that do not support RFC		to the new OCP. As a result, nodes that do not support RFC 8138 join
	8138 join as leaves and do not forward packets anymore. The leaves		as leaves and do not forward packets anymore. The leaves generate
	generate packets without compression. The parents - which supports		packets without compression. The parents - which supports RFC 8138 -
	RFC 8138 - may encapsulate the packets using RFC 8138 if needed. The		may encapsulate the packets using RFC 8138 if needed. The other way
	other way around, the root encapsulates packets to the leaves all the		around, the root encapsulates packets to the leaves all the way to
	way to the parent, which decapsulates and distribute the uncompresses		the parent, which decapsulates and distribute the uncompressed inner
	inner packet to the leaf.		packet to the leaf.
	This scenario presents a number of caveats:		This scenario presents a number of caveats:
	* The method consumes an extra OCP. It also requires a means to		* The method consumes an extra OCP. It also requires a means to
	signal the capabilities of the leaf, e.g., using "RPL Mode of		signal the capabilities of the leaf, e.g., using "RPL Mode of
	Operation extension" [MOP-EXT].		Operation extension" [MOP-EXT].
	* If an implementation does not move to a leaf mode when the OCP is		* If an implementation does not move to a leaf mode when the OCP is
	changed to an unknown one, then the node may be stalled.		changed to an unknown one, then the node may be stalled.
	* If the only possible parents of a node are nodes that do not		* If the only possible parents of a node are nodes that do not
	support RFC 8138, then that node will loose all its parent at the		support RFC 8138, then that node will loose all its parent at the
	time of the migration and it will be stalled until a parent is		time of the migration and it will be stalled until a parent is
	deployed with the new capability.		deployed with the new capability.
	* Nodes that only support RFC8138 for forwarding may not parse the		* Nodes that only support RFC8138 for forwarding may not parse the
	RPI in native form. If such nodes are present, the parent needs		RPI in native form. If such nodes are present, the parent needs
	to encapsulate with RFC8138.		to encapsulate with RFC8138.
	5.3. Double Instance Scenario		5.3. Double RPL Instances Scenario
	An alternate to the Single Instance Scenario is to deploy an		An alternate to the Single RPL Instance Scenario is to deploy an
	additional Instance for the nodes that support [RFC8138]. The two		additional RPL Instance for the nodes that support [RFC8138]. The
	instances operate as ships-in-the-night as specified in [RFC6550].		two RPL Instances operate independently as specified in [RFC6550].
	The preexisting Instance that does not use [RFC8138], whereas the new		The preexisting RPL Instance that does not use [RFC8138], whereas the
	Instance does. This is signaled by the "T" flag which is only set in		new RPL Instance does. This is signaled by the "T" flag which is
	the configuration option in DIO messages in the new Instance.		only set in the configuration option in DIO messages in the new RPL
			Instance.
	Nodes that support RFC 8138 participate to both Instances but favor		Nodes that support RFC 8138 participate to both Instances but favor
	the new Instance for the traffic that they source. On the other		the new RPL Instance for the traffic that they source. On the other
	hand, nodes that only support the uncompressed format would either		hand, nodes that only support the uncompressed format would either
	not be configured for the new instance, or would be configured to		not be configured for the new RPL Instance, or would be configured to
	join it as leaves only.		join it as leaves only.
	This method eliminates the risks of nodes being stalled that are		This method eliminates the risks of nodes being stalled that are
	described in Section 5.2 but requires implementations to support at		described in Section 5.2 but requires implementations to support at
	least two RPL Instances and demands management capabilities to		least two RPL Instances and demands management capabilities to
	introduce new Instances and deprecate old ones.		introduce new RPL Instances and deprecate old ones.
	5.4. Rolling Back		5.4. Rolling Back
	After downgrading a network to turn the [RFC8138] compression off,		After downgrading a network to turn the [RFC8138] compression off,
	the administrator SHOULD make sure that all nodes have converged to		the administrator SHOULD make sure that all nodes have converged to
	the "T" flag reset before allowing nodes that do not support the		the "T" flag reset before allowing nodes that do not support the
	compression in the network (see caveats in Section 5.2).		compression in the network (see caveats in Section 5.2).
	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
	skipping to change at page 7, line 41 ¶		skipping to change at page 7, line 49 ¶
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,		[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
	Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,		Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
	JP., and R. Alexander, "RPL: IPv6 Routing Protocol for		JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
	Low-Power and Lossy Networks", RFC 6550,		Low-Power and Lossy Networks", RFC 6550,
	DOI 10.17487/RFC6550, March 2012,		DOI 10.17487/RFC6550, March 2012,
	<https://www.rfc-editor.org/info/rfc6550>.		<https://www.rfc-editor.org/info/rfc6550>.
			[USEofRPLinfo]
			Robles, I., Richardson, M., and P. Thubert, "Using RPI
			Option Type, Routing Header for Source Routes and IPv6-in-
			IPv6 encapsulation in the RPL Data Plane", Work in
			Progress, Internet-Draft, draft-ietf-roll-useofrplinfo-34,
			20 January 2020, <https://tools.ietf.org/html/draft-ietf-
			roll-useofrplinfo-34>.
	10. Informative References		10. Informative References
	[RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie,		[RFC8138] Thubert, P., Ed., Bormann, C., Toutain, L., and R. Cragie,
	"IPv6 over Low-Power Wireless Personal Area Network		"IPv6 over Low-Power Wireless Personal Area Network
	(6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138,		(6LoWPAN) Routing Header", RFC 8138, DOI 10.17487/RFC8138,
	April 2017, <https://www.rfc-editor.org/info/rfc8138>.		April 2017, <https://www.rfc-editor.org/info/rfc8138>.
	[MOP-EXT] Jadhav, R., Thubert, P., and M. Richardson, "Mode of		[MOP-EXT] Jadhav, R., Thubert, P., and M. Richardson, "Mode of
	Operation extension and Capabilities", Work in Progress,		Operation extension and Capabilities", Work in Progress,
	Internet-Draft, draft-ietf-roll-mopex-cap-01, 2 November		Internet-Draft, draft-ietf-roll-mopex-cap-01, 2 November
	2019, <https://tools.ietf.org/html/draft-ietf-roll-mopex-		2019, <https://tools.ietf.org/html/draft-ietf-roll-mopex-
	cap-01>.		cap-01>.
	Authors' Addresses		Authors' Addresses
	Pascal Thubert (editor)		Pascal Thubert (editor)
	Cisco Systems, Inc		Cisco Systems, Inc
	Building D, 45 Allee des Ormes - BP1200		Building D
			45 Allee des Ormes - BP1200
	06254 MOUGINS - Sophia Antipolis		06254 MOUGINS - Sophia Antipolis
	France		France
	Phone: +33 497 23 26 34		Phone: +33 497 23 26 34
	Email: pthubert@cisco.com		Email: pthubert@cisco.com
	Li Zhao		Li Zhao
	Cisco Systems, Inc		Cisco Systems, Inc
	Xinsi Building, No. 926 Yi Shan Rd		Xinsi Building
			No. 926 Yi Shan Rd
	SHANGHAI		SHANGHAI
	200233		200233
	China		China
	Email: liz3@cisco.com		Email: liz3@cisco.com
End of changes. 27 change blocks.
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