< draft-ietf-roll-mopex-02.txt		draft-ietf-roll-mopex-03.txt >
	ROLL R. Jadhav, Ed.		ROLL R. Jadhav, Ed.
	Internet-Draft Huawei Tech		Internet-Draft Huawei Tech
	Intended status: Standards Track P. Thubert		Intended status: Standards Track P. Thubert
	Expires: April 2, 2021 Cisco		Expires: October 2, 2021 Cisco
	M. Richardson		M. Richardson
	Sandelman Software Works		Sandelman Software Works
	September 29, 2020		March 31, 2021
	Mode of Operation extension		Mode of Operation extension
	draft-ietf-roll-mopex-02		draft-ietf-roll-mopex-03
	Abstract		Abstract
	RPL allows different mode of operations which allows nodes to have a		RPL allows different mode of operations which allows nodes to have a
	consensus on the basic primitives that must be supported to join the		consensus on the basic primitives that must be supported to join the
	network. The MOP field in [RFC6550] is of 3 bits and is fast		network. The MOP field in [RFC6550] is of 3 bits and is fast
	depleting. This document extends the MOP for future use.		depleting. This document extends the MOP for future use.
	Status of This Memo		Status of This Memo
	skipping to change at page 1, line 36 ¶		skipping to change at page 1, line 36 ¶
	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 April 2, 2021.		This Internet-Draft will expire on October 2, 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2021 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		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
	skipping to change at page 2, line 32 ¶		skipping to change at page 2, line 32 ¶
	7.4. Change in RPL Control Option field . . . . . . . . . . . 7		7.4. Change in RPL Control Option field . . . . . . . . . . . 7
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 7		8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
	9.1. Normative References . . . . . . . . . . . . . . . . . . 8		9.1. Normative References . . . . . . . . . . . . . . . . . . 8
	9.2. Informative References . . . . . . . . . . . . . . . . . 8		9.2. Informative References . . . . . . . . . . . . . . . . . 8
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	RPL [RFC6550] specifies a proactive distance-vector based routing		RPL [RFC6550] specifies a proactive distance-vector based routing
	scheme. The protocol creates a DAG-like structure which operates		scheme. The protocol creates a DAG-like structure that operates with
	with a given "Mode of Operation" (MOP) determining the minimal and		a given "Mode of Operation" (MOP) determining the minimum and
	mandatory set of primitives to be supported by all the participating		mandatory set of primitives to be supported by all the participating
	nodes.		nodes.
	MOP as per [RFC6550] is a 3-bit value carried in DIO messages and is		MOP as per [RFC6550] is a 3-bit value carried in DIO messages and is
	specific to the RPL Instance. The recipient of the DIO message can		specific to the RPL Instance. The recipient of the DIO message can
	join the specified network as a router only when it can support the		join the specified network as a router only when it can support the
	primitives as required by the mode of operation value. For example,		primitives as required by the mode of operation value. For example,
	in case of MOP=3 (Storing MOP with multicast support) the nodes can		in the case of MOP=3 (Storing MOP with multicast support), the nodes
	join the network as routers only when they can handle the DAO		can join the network as routers only when they can handle the DAO
	advertisements from the peers and manage routing tables. The 3-bit		advertisements from the peers and manage routing tables. The 3-bit
	value is already exhausted and requires replenishment. This document		value is already exhausted and requires replenishment. This document
	introduces a mechanism to extend mode of operation values.		introduces a mechanism to extend the mode of operation values.
	This document further extends the RPL Control Option syntax to handle		This document further extends the RPL Control Option syntax to handle
	generic flags. The primary aim of these flags is to define the		generic flags. The primary aim of these flags is to define the
	behaviour of a node not supporting the given control type. If a node		behavior of a node not supporting the given control type. If a node
	does not support a given RPL Control Option, there are following		does not support a given RPL Control Option, there are following
	possibilities:		possibilities:
	Strip off the option		Strip off the option
	Copy the option as-is		Copy the option as-is
	Ignore the message containing this option		Ignore the message containing this option
	Let the node join in only as a 6LN to this parent		Let the node join in only as a 6LN to this parent
	skipping to change at page 3, line 27 ¶		skipping to change at page 3, line 27 ¶
	document are to be interpreted as described in RFC 2119 [RFC2119].		document are to be interpreted as described in RFC 2119 [RFC2119].
	MOP: Mode of Operation. Identifies the mode of operation of the RPL		MOP: Mode of Operation. Identifies the mode of operation of the RPL
	Instance as administratively provisioned at and distributed by the		Instance as administratively provisioned at and distributed by the
	DODAG root.		DODAG root.
	MOPex: Extended MOP: This document extends the MOP values over a		MOPex: Extended MOP: This document extends the MOP values over a
	bigger range. This extension of MOP is called MOPex.		bigger range. This extension of MOP is called MOPex.
	DAO: DODAG Advertisement Object. An RPL message used to advertise		DAO: DODAG Advertisement Object. An RPL message used to advertise
	the target information in order to establish routing adjacencies.		the target information to establish routing adjacencies.
	DIO: DODAG Information Object. An RPL message initiated by the root		DIO: DODAG Information Object. An RPL message initiated by the root
	and used to advertise the network configuration information.		and used to advertise the network configuration information.
	Current parent: Parent 6LR node before switching to the new path.		Current parent: Parent 6LR node before switching to the new path.
	This document uses terminology described in [RFC6550]. For the sake		This document uses the terminology described in [RFC6550]. For the
	of readability all the known relevant terms are repeated in this		sake of readability, all the known relevant terms are repeated in
	section.		this section.
	2. Requirements for this document		2. Requirements for this document
	Following are the requirements considered for this documents:		Following are the requirements considered for this documents:
	REQ1: MOP extension. Current MOP of 3-bit is fast depleting. An		REQ1: MOP extension. The 3-bits MOP as defined in [RFC6550] is fast
	MOP extension needs to extend the possibility of adding new		depleting. An MOP extension needs to extend the possibility
	MOPs in the future.		of adding new MOPs in the future.
	REQ2: Backwards compatibility. The new options and new fields in		REQ2: Backwards compatibility. The new options and new fields in
	the DIO message should be backward compatible i.e. if there		the DIO message should be backward compatible i.e. if there
	are nodes which support old MOPs they could still operate in		are nodes that support old MOPs they could still operate in
	their own RPL Instances.		their RPL Instances.
	3. Extended MOP Control Message Option		3. Extended MOP Control Message Option
	This document reserves existing MOP value 7 to be used as an		This document reserves the existing MOP value 7 to be used as an
	extender. DIO messages with MOP value of 7 may refer to the Extended		extender. DIO messages with an MOP value of 7 MUST refer to the
	MOP (MOPex) option in the DIO message.		Extended MOP (MOPex) option in the DIO message.
	0 1 2		0 1 2
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------
	| Type = TODO | Opt Length | OP-value		| Type = TODO | Opt Length | OP-value
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+---------------
	Figure 1: Extended MOP Option		Figure 1: Extended MOP Option
	The option length value MUST be less than or equal to 2. An option		The option length value MUST be less than or equal to 2. An option
	skipping to change at page 4, line 34 ¶		skipping to change at page 4, line 34 ¶
	The MOPex option MUST be used only if the base DIO MOP is 7. If the		The MOPex option MUST be used only if the base DIO MOP is 7. If the
	base DIO MOP is 7 and if the MOPex option is not present then the DIO		base DIO MOP is 7 and if the MOPex option is not present then the DIO
	MUST be silently ignored. If the base DIO MOP is less than 7 then		MUST be silently ignored. If the base DIO MOP is less than 7 then
	MOPex MUST NOT be used. In case the base MOP is 7 and if the MOPex		MOPex MUST NOT be used. In case the base MOP is 7 and if the MOPex
	option is present, then the implementation MUST use the final MOP		option is present, then the implementation MUST use the final MOP
	value from the MOPex.		value from the MOPex.
	Note that [RFC6550] allows a node that does not support the received		Note that [RFC6550] allows a node that does not support the received
	MOP to still join the network as a leaf node. This semantics		MOP to still join the network as a leaf node. This semantics
	continues to be true even in case of MOPex.		continues to be true even in the case of MOPex.
	3.2. Use of values 0-6 in the MOPex option		3.2. Use of values 0-6 in the MOPex option
	The MOPex option could also be allowed to re-use the values 0-6,		The MOPex option could also be allowed to re-use the values 0-6,
	which have been used for MOP so far. The use of current MOPs in		which have been used for MOP so far. The use of current MOPs in
	MOPex indicates that the MOP is supported with extended set of		MOPex indicates that the MOP is supported with an extended set of
	semantics for e.g., the capability options		semantics e.g., the capability options [I-D.ietf-roll-capabilities].
	[I-D.ietf-roll-capabilities].
	4. Extending RPL Control Options		4. Extending RPL Control Options
	Section 6.7.1 of RFC6550 explains the RPL Control Message Option		Section 6.7.1 of RFC6550 explains the RPL Control Message Option
	Generic Format. This document extends this format to following:		Generic Format. This document extends this format to following:
	0 1 2		0 1 2
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-----------		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-----------
	|X| OptionType| Option Length |Opt Flags|J|I|C| Option Data		|X| OptionType| Option Length |Opt Flags|J|I|C| Option Data
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-----------		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-----------
	Figure 2: Extended RPL Option Format		Figure 2: Extended RPL Option Format
	New fields in extended RPL Control Message Option Format:		New fields in extended RPL Control Message Option Format:
	'X' bit in Option Type: Value 1 indicates that this is an extended		'X' bit in Option Type: Value 1 indicates that this is an extended
	option. If the 'X' flag is set, a 1 byte Option Flags follows the		option. If the 'X' flag is set, a 1-byte Option Flags follows the
	Option Length field.		Option Length field.
	Option Length: 8-bit unsigned integer, representing the length in		Option Length: 8-bit unsigned integer, representing the length in
	octets of the option, not including the Option Type and Length		octets of the option, not including the Option Type and Length
	fields. Option Flags and variable length Option Data fields are		fields. Option Flags and variable length Option Data fields are
	included in the length.		included in the length.
	'J' (Join) bit in Option Flags: A node MUST join only as a 6LN if		'J' (Join) bit in Option Flags: A node MUST join only as a 6LN if
	the Option Type is not understood.		the Option Type is not understood.
	'C' (Copy) bit in Option Flags: A node that does not understand		'C' (Copy) bit in Option Flags: A node that does not understand
	the Option Type MUST copy the Option while generating the		the Option Type MUST copy the Option while generating the
	corresponding message. For e.g., if a 6LR receives a DIO message		corresponding message. E.g., if a 6LR receives a DIO message with
	with an unknown Option with 'C' bit set and if the 6LR choses to		an unknown Option with 'C' bit set and if the 6LR chooses to
	accept this node as the preferred parent then the node MUST copy		accept this node as the preferred parent then the node MUST copy
	this option in the subsequent DIO message it generates.		this option in the subsequent DIO message it generates.
	Alternatively, if the 'C' flag is unset the node MUST strip off		Alternatively, if the 'C' flag is unset the node MUST strip off
	the option and process the message.		the option and process the message.
	'I' (Ignore) bit in Option Flags: A node that does not understand		'I' (Ignore) bit in Option Flags: A node that does not understand
	the Option Type MUST ignore this whole message if the 'I' bit is		the Option Type MUST ignore this whole message if the 'I' bit is
	set. If 'I' bit is set than the value of 'J' and 'C' bits are		set. If the 'I' bit is set then the value of 'J' and 'C' bits are
	irrelevant and the message MUST be ignored.		irrelevant and the message MUST be ignored.
	Note that this format does not deprecate the previous format, it		Note that this format does not deprecate the previous format, it
	simply extends it and the new format is applicable only when 2nd bit		simply extends it and the new format is applicable only when 2nd bit
	('X' flag) of the Option Type is set. Option Type 0x80 to 0xFF are		('X' flag) of the Option Type is set. Option Type 0x80 to 0xFF are
	thus applicable only as extended options.		thus applicable only as extended options.
	+---------+---------+-----------------------------------------------+		+---------+---------+-----------------------------------------------+
	| 'J' bit | 'C' bit | Handling |		| 'J' bit | 'C' bit | Handling |
	+---------+---------+-----------------------------------------------+		+---------+---------+-----------------------------------------------+
End of changes. 19 change blocks.
	31 lines changed or deleted		30 lines changed or added
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