< draft-ietf-lpwan-schc-over-lorawan-04.txt		draft-ietf-lpwan-schc-over-lorawan-05.txt >
	lpwan Working Group O. Gimenez, Ed.		lpwan Working Group O. Gimenez, Ed.
	Internet-Draft Semtech		Internet-Draft Semtech
	Intended status: Informational I. Petrov, Ed.		Intended status: Informational I. Petrov, Ed.
	Expires: May 7, 2020 Acklio		Expires: June 22, 2020 Acklio
	November 04, 2019		December 20, 2019
	Static Context Header Compression (SCHC) over LoRaWAN		Static Context Header Compression (SCHC) over LoRaWAN
	draft-ietf-lpwan-schc-over-lorawan-04		draft-ietf-lpwan-schc-over-lorawan-05
	Abstract		Abstract
	The Static Context Header Compression (SCHC) specification describes		The Static Context Header Compression (SCHC) specification describes
	generic header compression and fragmentation techniques for LPWAN		generic header compression and fragmentation techniques for LPWAN
	(Low Power Wide Area Networks) technologies. SCHC is a generic		(Low Power Wide Area Networks) technologies. SCHC is a generic
	mechanism designed for great flexibility so that it can be adapted		mechanism designed for great flexibility so that it can be adapted
	for any of the LPWAN technologies.		for any of the LPWAN technologies.
	This document provides the adaptation of SCHC for use in LoRaWAN		This document provides the adaptation of SCHC for use in LoRaWAN
	skipping to change at page 1, line 39 ¶		skipping to change at page 1, line 39 ¶
	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 22, 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
	skipping to change at page 2, line 25 ¶		skipping to change at page 2, line 25 ¶
	4. LoRaWAN Architecture . . . . . . . . . . . . . . . . . . . . 5		4. LoRaWAN Architecture . . . . . . . . . . . . . . . . . . . . 5
	4.1. End-Device classes (A, B, C) and interactions . . . . . . 6		4.1. End-Device classes (A, B, C) and interactions . . . . . . 6
	4.2. End-Device addressing . . . . . . . . . . . . . . . . . . 7		4.2. End-Device addressing . . . . . . . . . . . . . . . . . . 7
	4.3. General Message Types . . . . . . . . . . . . . . . . . . 7		4.3. General Message Types . . . . . . . . . . . . . . . . . . 7
	4.4. LoRaWAN MAC Frames . . . . . . . . . . . . . . . . . . . 8		4.4. LoRaWAN MAC Frames . . . . . . . . . . . . . . . . . . . 8
	4.5. Unicast and multicast technology . . . . . . . . . . . . 8		4.5. Unicast and multicast technology . . . . . . . . . . . . 8
	5. SCHC-over-LoRaWAN . . . . . . . . . . . . . . . . . . . . . . 8		5. SCHC-over-LoRaWAN . . . . . . . . . . . . . . . . . . . . . . 8
	5.1. LoRaWAN FPort . . . . . . . . . . . . . . . . . . . . . . 8		5.1. LoRaWAN FPort . . . . . . . . . . . . . . . . . . . . . . 8
	5.2. Rule ID management . . . . . . . . . . . . . . . . . . . 9		5.2. Rule ID management . . . . . . . . . . . . . . . . . . . 9
	5.3. IID computation . . . . . . . . . . . . . . . . . . . . . 10		5.3. IID computation . . . . . . . . . . . . . . . . . . . . . 10
	5.4. Padding . . . . . . . . . . . . . . . . . . . . . . . . . 10		5.4. Padding . . . . . . . . . . . . . . . . . . . . . . . . . 11
	5.5. Compression . . . . . . . . . . . . . . . . . . . . . . . 10		5.5. Decompression . . . . . . . . . . . . . . . . . . . . . . 11
	5.6. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 10		5.6. Fragmentation . . . . . . . . . . . . . . . . . . . . . . 11
	5.6.1. DTag . . . . . . . . . . . . . . . . . . . . . . . . 11		5.6.1. DTag . . . . . . . . . . . . . . . . . . . . . . . . 11
	5.6.2. Uplink fragmentation: From device to SCHC gateway . . 11		5.6.2. Uplink fragmentation: From device to SCHC gateway . . 11
	5.6.3. Downlink fragmentation: From SCHC gateway to a device 13		5.6.3. Downlink fragmentation: From SCHC gateway to a device 14
	6. Security considerations . . . . . . . . . . . . . . . . . . . 17		6. Security considerations . . . . . . . . . . . . . . . . . . . 17
	Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 17		Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 18
	Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 17		Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 18
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
	9.1. Normative References . . . . . . . . . . . . . . . . . . 18		9.1. Normative References . . . . . . . . . . . . . . . . . . 18
	9.2. Informative References . . . . . . . . . . . . . . . . . 19		9.2. Informative References . . . . . . . . . . . . . . . . . 20
	Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 19		Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 20
	A.1. Uplink - Compression example - No fragmentation . . . . . 19		A.1. Uplink - Compression example - No fragmentation . . . . . 20
	A.2. Uplink - Compression and fragmentation example . . . . . 20		A.2. Uplink - Compression and fragmentation example . . . . . 21
	A.3. Downlink . . . . . . . . . . . . . . . . . . . . . . . . 22		A.3. Downlink . . . . . . . . . . . . . . . . . . . . . . . . 22
	Appendix B. Note . . . . . . . . . . . . . . . . . . . . . . . . 23		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
	1. Introduction		1. Introduction
	The Static Context Header Compression (SCHC) specification		The Static Context Header Compression (SCHC) specification
	[I-D.ietf-lpwan-ipv6-static-context-hc] describes generic header		[I-D.ietf-lpwan-ipv6-static-context-hc] describes generic header
	compression and fragmentation techniques that can be used on all		compression and fragmentation techniques that can be used on all
	LPWAN (Low Power Wide Area Networks) technologies defined in		LPWAN (Low Power Wide Area Networks) technologies defined in
	[RFC8376]. Even though those technologies share a great number of		[RFC8376]. Even though those technologies share a great number of
	common features like star-oriented topologies, network architecture,		common features like star-oriented topologies, network architecture,
	devices with mostly quite predictable communications, etc; they do		devices with mostly quite predictable communications, etc; they do
	skipping to change at page 3, line 40 ¶		skipping to change at page 3, line 39 ¶
	o DevAddr: a 32-bit non-unique identifier assigned to an end-device		o DevAddr: a 32-bit non-unique identifier assigned to an end-device
	statically or dynamically after a Join Procedure (depending on the		statically or dynamically after a Join Procedure (depending on the
	activation mode)		activation mode)
	o RCS: Reassembly Check Sequence. Used to verify the integrity of		o RCS: Reassembly Check Sequence. Used to verify the integrity of
	the fragmentation-reassembly process		the fragmentation-reassembly process
	o TBD: all significant LoRaWAN-related terms.		o TBD: all significant LoRaWAN-related terms.
			o OUI: Organisation Unique Identifier. IEEE assigned prefix for EUI
	3. Static Context Header Compression Overview		3. Static Context Header Compression Overview
	This section contains a short overview of Static Context Header		This section contains a short overview of Static Context Header
	Compression (SCHC). For a detailed description, refer to the full		Compression (SCHC). For a detailed description, refer to the full
	specification [I-D.ietf-lpwan-ipv6-static-context-hc].		specification [I-D.ietf-lpwan-ipv6-static-context-hc].
	Static Context Header Compression (SCHC) avoids context		It defines:
	synchronization, based on the fact that the nature of data flows is
	highly predictable in LPWAN networks, some static contexts may be		1. Compression mechanisms to avoid transport of known data by both
	stored on the Device (Dev). The context MUST be stored in both ends,		sender and receiver over the air. Known data are part of the
	and it can either be learned by a provisioning protocol or by out-of-		"context"
	band means or it can be pre-provisioned, etc. The way the context is
	learned on both sides is outside the scope of this document.		2. Fragmentation mechanisms to allow SCHC Packet transportation on
			small, and potentially variable, MTU
			Context exchange or pre-provisioning is out of scope of this
			document.
	Dev App		Dev App
	+----------------+ +----+ +----+ +----+		+----------------+ +----+ +----+ +----+
	| App1 App2 App3 | |App1| |App2| |App3|		| App1 App2 App3 | |App1| |App2| |App3|
	| | | | | | | |		| | | | | | | |
	| UDP | |UDP | |UDP | |UDP |		| UDP | |UDP | |UDP | |UDP |
	| IPv6 | |IPv6| |IPv6| |IPv6|		| IPv6 | |IPv6| |IPv6| |IPv6|
	| | | | | | | |		| | | | | | | |
	|SCHC C/D and F/R| | | | | | |		|SCHC C/D and F/R| | | | | | |
	+--------+-------+ +----+ +----+ +----+		+--------+-------+ +----+ +----+ +----+
	skipping to change at page 5, line 42 ¶		skipping to change at page 5, line 42 ¶
	radio gateway (LoRaWAN gateway). This entity maps to the LoRaWAN		radio gateway (LoRaWAN gateway). This entity maps to the LoRaWAN
	End-Device.		End-Device.
	o The Radio Gateway (RGW), which is the endpoint of the constrained		o The Radio Gateway (RGW), which is the endpoint of the constrained
	link. This entity maps to the LoRaWAN Gateway.		link. This entity maps to the LoRaWAN Gateway.
	o The Network Gateway (NGW) is the interconnection node between the		o The Network Gateway (NGW) is the interconnection node between the
	Radio Gateway and the Internet. This entity maps to the LoRaWAN		Radio Gateway and the Internet. This entity maps to the LoRaWAN
	Network Server.		Network Server.
	o LPWAN-AAA Server, which controls the user authentication and the
	applications. This entity maps to the LoRaWAN Join Server.
	o Application Server (App). The same terminology is used in LoRaWAN.		o Application Server (App). The same terminology is used in LoRaWAN.
	In that case, the application server will be the SCHC gateway, doing		In that case, the application server will be the SCHC gateway, doing
	C/D and F/R.		C/D and F/R.
	() () () | +------+		() () () | +------+
	() () () () / \ +---------+ | Join |		() () () () / \ +---------+ | Join |
	() () () () () / \======| ^ |===|Server| +-----------+		() () () () () / \======| ^ |===|Server| +-----------+
	() () () | | <--|--> | +------+ |Application|		() () () | | <--|--> | +------+ |Application|
	() () () () / \==========| v |=============| Server |		() () () () / \==========| v |=============| Server |
	() () () / \ +---------+ +-----------+		() () () / \ +---------+ +-----------+
	skipping to change at page 7, line 14 ¶		skipping to change at page 7, line 14 ¶
	are not transmitting. Class C end-devices can receive downlinks		are not transmitting. Class C end-devices can receive downlinks
	at any time at the expense of a higher power consumption.		at any time at the expense of a higher power consumption.
	Battery-powered end-devices can only operate in Class C for a		Battery-powered end-devices can only operate in Class C for a
	limited amount of time (for example for a firmware upgrade over-		limited amount of time (for example for a firmware upgrade over-
	the-air). Most of the Class C end-devices are grid powered (for		the-air). Most of the Class C end-devices are grid powered (for
	example Smart Plugs).		example Smart Plugs).
	4.2. End-Device addressing		4.2. End-Device addressing
	LoRaWAN end-devices use a 32-bit network address (devAddr) to		LoRaWAN end-devices use a 32-bit network address (devAddr) to
	communicate with the network over-the-air. However, that address		communicate with the network over-the-air, this address might not be
	might be reused several times on the same network at the same time		unique in a LoRaWAN network; end-devices using the same devAddr are
	for different end-devices. End-devices using the same devAddr are
	distinguished by the Network Server based on the cryptographic		distinguished by the Network Server based on the cryptographic
	signature appended to every single LoRaWAN MAC frame, as all end-		signature appended to every LoRaWAN frame.
	devices use different security keys. To communicate with the SCHC
	gateway the Network Server MUST identify the end-devices by a unique		To communicate with the SCHC gateway the Network Server MUST identify
	64-bit device identifier called the devEUI. Unlike devAddr, devEUI		the end-devices by a unique 64-bit device identifier called the
	is guaranteed to be unique for every single end-device across all		devEUI.
	networks. The devEUI is assigned to the end-device during the
	manufacturing process by the end-device's manufacturer. It is built		The devEUI is assigned to the end-device during the manufacturing
	like an Ethernet MAC address by concatenating the manufacturer's IEEE		process by the end-device's manufacturer. It is built like an
	OUI field with a vendor unique number. e.g.: 24-bit OUI is		Ethernet MAC address by concatenating the manufacturer's IEEE OUI
	concatenated with a 40-bit serial number. The Network Server		field with a vendor unique number. e.g.: 24-bit OUI is concatenated
	translates the devAddr into a devEUI in the uplink direction and		with a 40-bit serial number. The Network Server translates the
	reciprocally on the downlink direction.		devAddr into a devEUI in the uplink direction and reciprocally on the
			downlink direction.
	+--------+ +----------+ +---------+ +----------+		+--------+ +----------+ +---------+ +----------+
	| End- | <=====> | Network | <====> | SCHC | <========> | Internet |		| End- | <=====> | Network | <====> | SCHC | <========> | Internet |
	| Device | devAddr | Server | devEUI | Gateway | IPv6/UDP | |		| Device | devAddr | Server | devEUI | Gateway | IPv6/UDP | |
	+--------+ +----------+ +---------+ +----------+		+--------+ +----------+ +---------+ +----------+
	Figure 4: LoRaWAN addresses		Figure 4: LoRaWAN addresses
	4.3. General Message Types		4.3. General Message Types
	skipping to change at page 8, line 17 ¶		skipping to change at page 8, line 17 ¶
	o JoinRequest: This message is used by an end-device to join a		o JoinRequest: This message is used by an end-device to join a
	network. It contains the end-device's unique identifier devEUI		network. It contains the end-device's unique identifier devEUI
	and a random nonce that will be used for session key derivation.		and a random nonce that will be used for session key derivation.
	o JoinAccept: To on-board an end-device, the Network Server responds		o JoinAccept: To on-board an end-device, the Network Server responds
	to the JoinRequest end-device's message with a JoinAccept message.		to the JoinRequest end-device's message with a JoinAccept message.
	That message is encrypted with the end-device's AppKey and		That message is encrypted with the end-device's AppKey and
	contains (amongst other fields) the major network's settings and a		contains (amongst other fields) the major network's settings and a
	network random nonce used to derive the session keys.		network random nonce used to derive the session keys.
	o Data		o Data: MAC and application data. Application data are protected
			with AES-128 encryption, MAC related data are AES-128 encrypted
			with another key.
	4.5. Unicast and multicast technology		4.5. Unicast and multicast technology
	LoRaWAN technology supports unicast downlinks, but also multicast: a		LoRaWAN technology supports unicast downlinks, but also multicast: a
	packet send over LoRaWAN radio link can be received by several		packet send over LoRaWAN radio link can be received by several
	devices. It is useful to address many end-devices with same content,		devices. It is useful to address many end-devices with same content,
	either a large binary file (firmware upgrade), or same command (e.g:		either a large binary file (firmware upgrade), or same command (e.g:
	lighting control). As IPv6 is also a multicast technology this		lighting control). As IPv6 is also a multicast technology this
	feature MAY be used to address a group of devices.		feature can be used to address a group of devices.
	_Note 1_: IPv6 multicast addresses must be defined as per [RFC4291].		_Note 1_: IPv6 multicast addresses must be defined as per [RFC4291].
	LoRaWAN multicast group definition in a network server and the		LoRaWAN multicast group definition in a network server and the
	relation between those groups and IPv6 groupID are out of scope of		relation between those groups and IPv6 groupID are out of scope of
	this document.		this document.
	_Note 2_: LoRa Alliance defined [lora-alliance-remote-multicast-set]		_Note 2_: LoRa Alliance defined [lora-alliance-remote-multicast-set]
	as RECOMMENDED way to setup multicast groups on devices and create a		as RECOMMENDED way to setup multicast groups on devices and create a
	synchronized reception window.		synchronized reception window.
	5. SCHC-over-LoRaWAN		5. SCHC-over-LoRaWAN
	5.1. LoRaWAN FPort		5.1. LoRaWAN FPort
	The LoRaWAN MAC layer features a frame port field in all frames.		The LoRaWAN MAC layer features a frame port field in all frames.
	This field (FPort) is 8 bits long and the values from 1 to 223 can be		This field (FPort) is 8 bits long and the values from 1 to 223 can be
	used. It allows LoRaWAN networks and applications to identify data.		used. It allows LoRaWAN networks and applications to identify data.
	The FPort field is part of the SCHC Packet or the SCHC Fragment, as		The FPort field is part of the SCHC Message, as shown in Figure 5.
	shown in Figure 5. The SCHC C/D and the SCHC F/R SHALL concatenate		The SCHC C/D and the SCHC F/R SHALL concatenate the FPort field with
	the FPort field with the LoRaWAN payload to retrieve their payload as		the LoRaWAN payload to retrieve their payload as it is used as a part
	it is used as a part of the ruleId field.		of the RuleID field.
	| FPort | LoRaWAN payload |		| FPort | LoRaWAN payload |
	+ ------------------------ +		+ ------------------------ +
	| SCHC payload |		| SCHC payload |
	Figure 5: SCHC payload in LoRaWAN		Figure 5: SCHC Message in LoRaWAN
	A fragmentation session with application payload transferred from		A fragmentation session with application payload transferred from
	device to server, is called uplink fragmentation session. It uses an		device to server, is called uplink fragmentation session. It uses an
	FPort for data uplink and its associated SCHC control downlinks,		FPort for data uplink and its associated SCHC control downlinks,
	named FPortUp in this document. The other way, a fragmentation		named FPortUp in this document. The other way, a fragmentation
	session with application payload transferred from server to device,		session with application payload transferred from server to device,
	is called downlink fragmentation session. It uses another FPort for		is called downlink fragmentation session. It uses another FPort for
	data downlink and its associated SCHC control uplinks, named		data downlink and its associated SCHC control uplinks, named
	FPortDown in this document.		FPortDown in this document.
	FPorts can use arbitrary values inside the allowed FPort range and		All ruleId can use arbitrary values inside the FPort range allowed by
	MUST be shared by the end-device, the Network Server and SCHC gateway		LoRaWAN specification and MUST be shared by the end-device and SCHC
	prior to the communication. The uplink and downlink fragmentation		gateway prior to the communication with the selected rule. The
	FPorts MUST be different.		uplink and downlink fragmentation FPorts MUST be different.
	5.2. Rule ID management		5.2. Rule ID management
	RuleID MUST be 8 bits, encoded in the LoRaWAN FPort as described in		RuleID MUST be 8 bits, encoded in the LoRaWAN FPort as described in
	Section 5.1. LoRaWAN supports up to 223 application FPorts in the		Section 5.1. LoRaWAN supports up to 223 application FPorts in the
	range [1;223] as defined in section 4.3.2 of [lora-alliance-spec], it		range [1;223] as defined in section 4.3.2 of [lora-alliance-spec], it
	implies that RuleID MSB SHOULD be inside this range. An application		implies that RuleID MSB SHOULD be inside this range. An application
	MAY reserve some FPort values for other needs as long as they don't		can send non SCHC traffic by using FPort values differents from the
	conflict with FPorts used for SCHC C/D and SCHC F/R.		ones used for SCHC.
	In order to improve interoperability RECOMMENDED fragmentation RuleID		In order to improve interoperability RECOMMENDED fragmentation RuleID
	values are:		values are:
	o RuleID = 20 (8-bit) for uplink fragmentation, named FPortUp		o RuleID = 20 (8-bit) for uplink fragmentation, named FPortUp
	o RuleID = 21 (8-bit) for downlink fragmentation, named FPortDown		o RuleID = 21 (8-bit) for downlink fragmentation, named FPortDown
	o RuleID = 22 (8-bit) for which SCHC compression was not possible		o RuleID = 22 (8-bit) for which SCHC compression was not possible
	(no matching rule was found)		(no matching rule was found)
	The remaining RuleIDs are available for compression. RuleIDs are		The remaining RuleIDs are available for compression. RuleIDs are
	shared between uplink and downlink sessions. A RuleID different from		shared between uplink and downlink sessions. A RuleID not in the
	FPortUp or FPortDown means that the fragmentation is not used, thus		set(s) of FPortUp or FPortDown means that the fragmentation is not
	the packet SHOULD be sent to C/D layer.		used, thus, on reception, the SCHC Message MUST be sent to the C/D
			layer.
	The only uplink messages using the FPortDown port are the		The only uplink messages using the FPortDown port are the
	fragmentation SCHC control messages of a downlink fragmentation		fragmentation SCHC control messages of a downlink fragmentation
	session (ex ACKs). Similarly, the only downlink messages using the		session (for example, SCHC ACKs). Similarly, the only downlink
	FPortUp port are the fragmentation SCHC control messages of an uplink		messages using the FPortUp port are the fragmentation SCHC control
	fragmentation session.		messages of an uplink fragmentation session.
	An application can have multiple fragmentation sessions between a		An application can have multiple fragmentation sessions between a
	device and one or several SCHC gateways. A set of FPort values is		device and one or several SCHC gateways. A set of FPort values is
	REQUIRED for each SCHC gateway instance the device is required to		REQUIRED for each SCHC gateway instance the device is required to
	communicate with.		communicate with.
	The mechanism for sharing those RuleID values is outside the scope of		The mechanism for sharing those RuleID values is outside the scope of
	this document.		this document.
	5.3. IID computation		5.3. IID computation
	As LoRaWAN network uses unique EUI-64 per end-device, the Interface		In order to mitigate risks described in [RFC8064] and [RFC8065] IID
	IDentifier is the LoRaWAN DevEUI. It is compliant with [RFC4291] and		MUST be created regarding the following algorithm:
	IID starting with binary 000 must enforce the 64-bit rule.
	TODO: Derive IID from DevEUI with privacy constraints ? Ask working		1. key = LoRaWAN AppSKey
	group ?
			2. cmac = aes128_cmac(key, devEui)
			3. IID = cmac[0..7]
			aes128_cmac algorithm is described in [RFC4493]. It has been chosen
			as it is already used by devices for LoRaWAN procotol.
			As AppSKey is renewed each time a device joins or rejoins a network,
			the IID will change over time; this mitigates privacy, location
			tracking and correlation over time risks. Rejoin periodicity is
			defined at the application level.
			Address scan risk is mitigated thanks to AES-128, which provides
			enough entropy bits of the IID.
			Using this algorithm will also ensure that there is not correlation
			between the hardware identifier (IEEE-64 devEUI) and the IID, so an
			attacker can not use manufacturer OUI to target devices.
			Exemple with:
			o devEui: 0x1122334455667788
			o appSKey: 0x00AABBCCDDEEFF00AABBCCDDEEFFAABB
			1. key: 0x00AABBCCDDEEFF00AABBCCDDEEFFAABB
			2. cmac: 0x4E822D9775B2649928F82066AF804FEC
			3. IID: 0x28F82066AF804FEC
	5.4. Padding		5.4. Padding
	All padding bits MUST be 0.		All padding bits MUST be 0.
	5.5. Compression		5.5. Decompression
	SCHC C/D MUST concatenate FPort and LoRaWAN payload to retrieve the		SCHC C/D MUST concatenate FPort and LoRaWAN payload to retrieve the
	SCHC packet as per Section 5.1.		SCHC Packet as per Section 5.1.
	RuleIDs matching FPortUp and FPortDown are reserved for SCHC		RuleIDs matching FPortUp and FPortDown are reserved for SCHC
	Fragmentation.		Fragmentation.
	5.6. Fragmentation		5.6. Fragmentation
	The L2 word size used by LoRaWAN is 1 byte (8 bits). The SCHC		The L2 Word Size used by LoRaWAN is 1 byte (8 bits). The SCHC
	fragmentation over LoRaWAN uses the ACK-on-Error for uplink		fragmentation over LoRaWAN uses the ACK-on-Error mode for uplink
	fragmentation and Ack-Always for downlink fragmentation. A LoRaWAN		fragmentation and Ack-Always mode for downlink fragmentation. A
	end-device cannot support simultaneous interleaved fragmentation		LoRaWAN end-device cannot support simultaneous interleaved
	sessions in the same direction (uplink or downlink). This means that		fragmentation sessions in the same direction (uplink or downlink).
	only a single fragmented IPv6 datagram may be transmitted and/or
	received by the end-device at a given moment.
	The fragmentation parameters are different for uplink and downlink		The fragmentation parameters are different for uplink and downlink
	fragmentation sessions and are successively described in the next		fragmentation sessions and are successively described in the next
	sections.		sections.
	5.6.1. DTag		5.6.1. DTag
	A LoRaWAN device cannot interleave several fragmented SCHC datagrams		A LoRaWAN device cannot interleave several fragmented SCHC datagrams
	on the same FPort. This field is not used and its size is 0.		on the same FPort. This field is not used and its size is 0.
	Note: The device can still have several parallel fragmentation		Note: The device can still have several parallel fragmentation
	sessions with one or more SCHC gateway(s) thanks to distinct sets of		sessions with one or more SCHC gateway(s) thanks to distinct sets of
	FPorts, cf Section 5.2		FPorts, cf Section 5.2
	5.6.2. Uplink fragmentation: From device to SCHC gateway		5.6.2. Uplink fragmentation: From device to SCHC gateway
	In that case the device is the fragmentation transmitter, and the		In that case the device is the fragmentation transmitter, and the
	SCHC gateway the fragmentation receiver. A single fragmentation rule		SCHC gateway the fragmentation receiver. A single fragmentation rule
	is defined. SCHC F/R MUST concatenate FPort and LoRaWAN payload to		is defined. SCHC F/R MUST concatenate FPort and LoRaWAN payload to
	retrieve the SCHC fragment as per Section 5.1.		retrieve the SCHC Packet, as per Section 5.1.
	o SCHC header size is two bytes (the FPort byte + 1 additional		o SCHC header size is two bytes (the FPort byte + 1 additional
	byte).		byte).
	o RuleID: 8 bits stored in LoRaWAN FPort.		o RuleID: 8 bits stored in LoRaWAN FPort.
	o SCHC fragmentation reliability mode: "ACK-on-Error"		o SCHC fragmentation reliability mode: "ACK-on-Error"
	o DTag: Size is 0 bit, not used		o DTag: Size is 0 bit, not used
	o FCN: The FCN field is encoded on N = 6 bits, so WINDOW_SIZE = 63		o FCN: The FCN field is encoded on N = 6 bits, so WINDOW_SIZE = 63
	tiles are allowed in a window		tiles are allowed in a window
	o Window index: encoded on W = 2 bits. So 4 windows are available.		o Window index: encoded on W = 2 bits. So 4 windows are available.
	o RCS calculation algorithm: CRC32 using 0xEDB88320 (i.e. the		o RCS: Use recommended calculation algorithm in
	reverse representation of the polynomial used e.g. in the Ethernet
	standard [RFC3385]) as suggested in
	[I-D.ietf-lpwan-ipv6-static-context-hc].		[I-D.ietf-lpwan-ipv6-static-context-hc].
	o MAX_ACK_REQUESTS: 8		o MAX_ACK_REQUESTS: 8
	o Tile: size is 10 bytes		o Tile: size is 10 bytes
	o Retransmission and inactivity timers: LoRaWAN end-devices do not		o Retransmission timer: LoRaWAN end-devices MUST NOT implement a
	implement a "retransmission timer". At the end of a window or a		"retransmission timer", this changes the specification of
	fragmentation session, corresponding ACK(s) is (are) transmitted		[I-D.ietf-lpwan-ipv6-static-context-hc], see Section 5.6.3.5. It
	by the network gateway (LoRaWAN application server) in the RX1 or		must transmit MAX_ACK_REQUESTS time the SCHC ACK REQ at it own
	RX2 receive slot of end-device. If this ACK is not received by		timing; ie the periodicity between retransmission of SCHC ACK REQs
	the end-device at the end of its RX windows, it sends an all-0 (or		is device specific and can vary depending on other application
	an all-1) fragment with no payload to request an SCHC ACK		uplinks and regulations.
	retransmission. The periodicity between retransmission of the
	all-0/all-1 fragments is device/application specific and MAY be
	different for each device (not specified). The SCHC gateway
	implements an "inactivity timer". The default RECOMMENDED
	duration of this timer is 12 hours. This value is mainly driven
	by application requirements and MAY be changed by the application.
	o Last tile: The last tile can be carried in the All-1 fragment.		o Inactivity timer: The SCHC gateway implements an "inactivity
			timer". The default RECOMMENDED duration of this timer is 12
			hours; this value is mainly driven by application requirements and
			MAY be changed by the application.
			o Last tile: The last tile MUST NOT be carried in the All-1
			fragment.
			o Penultimate tile MUST be equal to the regular size.
	With this set of parameters, the SCHC fragment header is 16 bits,		With this set of parameters, the SCHC fragment header is 16 bits,
	including FPort; payload overhead will be 8 bits as FPort is already		including FPort; payload overhead will be 8 bits as FPort is already
	a part of LoRaWAN payload. MTU is: _4 windows * 63 tiles * 10 bytes		a part of LoRaWAN payload. MTU is: _4 windows * 63 tiles * 10 bytes
	per tile = 2520 bytes_		per tile = 2520 bytes_
			_Note_: As LoRaWAN is a radio communication, it is RECOMMENDED for an
			implementation to use ACK mechanism at the end of each window:
			o SCHC receiver sends an SCHC ACK after every window even if there
			is no missing tiles.
			o SCHC sender waits for the SCHC ACK from the SCHC receiver before
			sending tiles from next window. If the SCHC ACK is not received
			it should send an SCHC ACK REQ up to MAX_ACK_REQUESTS time as
			described previously.
			This OPTIONAL feature will prevent a device to transmit full payload
			if the network can not be reach, thus save battery life.
	5.6.2.1. Regular fragments		5.6.2.1. Regular fragments
	| FPort | LoRaWAN payload |		| FPort | LoRaWAN payload |
	+ ------ + ------------------------- +		+ ------ + ------------------------- +
	| RuleID | W | FCN | Payload |		| RuleID | W | FCN | Payload |
	+ ------ + ------ + ------ + ------- +		+ ------ + ------ + ------ + ------- +
	| 8 bits | 2 bits | 6 bits | |		| 8 bits | 2 bits | 6 bits | |
	Figure 6: All fragments except the last one. SCHC header size is 16		Figure 6: All fragments except the last one. SCHC header size is 16
	bits, including LoRaWAN FPort.		bits, including LoRaWAN FPort.
	5.6.2.2. Last fragment (All-1)		5.6.2.2. Last fragment (All-1)
	| FPort | LoRaWAN payload |		| FPort | LoRaWAN payload |
	+ ------ + ------------------------------------------------ +		+ ------ + ---------------------------- +
	| RuleID | W | FCN=All-1 | RCS | Payload |		| RuleID | W | FCN=All-1 | RCS |
	+ ------ + ------ + --------- + ------- + ----------------- +		+ ------ + ------ + --------- + ------- +
	| 8 bits | 2 bits | 6 bits | 32 bits | Last tile, if any |		| 8 bits | 2 bits | 6 bits | 32 bits |
	Figure 7: All-1 fragment detailed format for the last fragment.		Figure 7: All-1 fragment detailed format for the last fragment.
	5.6.2.3. SCHC ACK		5.6.2.3. SCHC ACK
	| FPort | LoRaWAN payload |		| FPort | LoRaWAN payload |
	+ ------ + ----------------------------------------- +		+ ------ + ----------------------------------------- +
	| RuleID | W | C | Encoded bitmap (if C = 0) |		| RuleID | W | C | Encoded bitmap (if C = 0) |
	+ ------ + ----- + ----- + ------------------------- +		+ ------ + ----- + ----- + ------------------------- +
	| 8 bits | 2 bit | 1 bit | 0 to 127 bits |		| 8 bits | 2 bit | 1 bit | 0 to 63 bits |
	Figure 8: SCHC formats, failed RCS check.		Figure 8: SCHC ACK format, failed RCS check.
	5.6.2.4. Receiver-Abort		5.6.2.4. Receiver-Abort
	| FPort | LoRaWAN payload |		| FPort | LoRaWAN payload |
	+ ------ + -------------------------------------------- +		+ ------ + -------------------------------------------- +
	| RuleID | W = b'11 | C = 1 | b'11111 | 0xFF (all 1's) |		| RuleID | W = b'11 | C = 1 | b'11111 | 0xFF (all 1's) |
	+ ------ + -------- + ------+-------- + ----------------+		+ ------ + -------- + ------+-------- + ----------------+
	| 8 bits | 2 bits | 1 bit | 5 bits | 8 bits |		| 8 bits | 2 bits | 1 bit | 5 bits | 8 bits |
	next L2 Word boundary ->| <-- L2 Word --> |		next L2 Word boundary ->| <-- L2 Word --> |
	skipping to change at page 13, line 31 ¶		skipping to change at page 14, line 20 ¶
	+ ------ + ------ + --------------- +		+ ------ + ------ + --------------- +
	| 8 bits | 2 bits | 6 bits |		| 8 bits | 2 bits | 6 bits |
	Figure 10: SCHC ACK REQ format.		Figure 10: SCHC ACK REQ format.
	5.6.3. Downlink fragmentation: From SCHC gateway to a device		5.6.3. Downlink fragmentation: From SCHC gateway to a device
	In that case the device is the fragmentation receiver, and the SCHC		In that case the device is the fragmentation receiver, and the SCHC
	gateway the fragmentation transmitter. The following fields are		gateway the fragmentation transmitter. The following fields are
	common to all devices. SCHC F/R MUST concatenate FPort and LoRaWAN		common to all devices. SCHC F/R MUST concatenate FPort and LoRaWAN
	payload to retrieve the SCHC fragment as described in Section 5.1.		payload to retrieve the SCHC Packet as described in Section 5.1.
	o SCHC fragmentation reliability mode:		o SCHC fragmentation reliability mode:
	* Unicast downlinks: ACK-Always.		* Unicast downlinks: ACK-Always.
	* Multicast downlinks: No-ACK, reliability has be be ensured by		* Multicast downlinks: No-ACK, reliability has to be ensured by
	the upper layer. This feature is OPTIONAL and may not be		the upper layer. This feature is OPTIONAL and may not be
	implemented by SCHC gateway.		implemented by SCHC gateway.
	o RuleID: 8 bits stored in LoRaWAN FPort.		o RuleID: 8 bits stored in LoRaWAN FPort.
	o Window index (unicast only): encoded on W=1 bit, as per		o Window index (unicast only): encoded on W=1 bit, as per
	[I-D.ietf-lpwan-ipv6-static-context-hc].		[I-D.ietf-lpwan-ipv6-static-context-hc].
	o DTag: Size is 0 bit, not used		o DTag: Size is 0 bit, not used
	o FCN: The FCN field is encoded on N=1 bit, so WINDOW_SIZE = 1 tile		o FCN: The FCN field is encoded on N=1 bit, so WINDOW_SIZE = 1 tile
	(FCN=All-1 is reserved for SCHC).		(FCN=All-1 is reserved for SCHC).
	o RCS calculation algorithm: CRC32 using 0xEDB88320 (i.e. the		o RCS: Use recommended calculation algorithm in
	reverse representation of the polynomial used e.g. in the Ethernet
	standard [RFC3385]), as per
	[I-D.ietf-lpwan-ipv6-static-context-hc].		[I-D.ietf-lpwan-ipv6-static-context-hc].
	o MAX_ACK_REQUESTS: 8		o MAX_ACK_REQUESTS: 8
	As only 1 tile is used, its size can change for each downlink, and		As only 1 tile is used, its size can change for each downlink, and
	will be maximum available MTU.		will be maximum available MTU.
	_Note_: The Fpending bit included in LoRaWAN protocol SHOULD NOT be		_Note_: The Fpending bit included in LoRaWAN protocol SHOULD NOT be
	used for SCHC-over-LoRaWAN protocol. It might be set by the Network		used for SCHC-over-LoRaWAN protocol. It might be set by the Network
	Server for other purposes but not SCHC needs.		Server for other purposes but not SCHC needs.
	5.6.3.1. Regular fragments		5.6.3.1. Regular fragments
	| FPort | LoRaWAN payload |		| FPort | LoRaWAN payload |
	+ ------ + ----------------------------------- +		+ ------ + ------------------------------------ +
	| RuleID | W | FCN = b'0 | Payload |		| RuleID | W | FCN = b'0 | Payload |
	+ ------ + ----- + --------- + --------------- +		+ ------ + ----- + --------- + ---------------- +
	| 8 bits | 1 bit | 1 bit | X bytes |		| 8 bits | 1 bit | 1 bit | X bytes + 6 bits |
	Figure 11: All fragments but the last one. Header size 10 bits,		Figure 11: All fragments but the last one. Header size 10 bits,
	including LoraWAN FPort.		including LoraWAN FPort.
	5.6.3.2. Last fragment (All-1)		5.6.3.2. Last fragment (All-1)
	| FPort | LoRaWAN payload |		| FPort | LoRaWAN payload |
	+ ------ + ----------------------------------------------- +		+ ------ + --------------------------- +
	| RuleID | W | FCN = b'1 | RCS | Payload |		| RuleID | W | FCN = b'1 | RCS |
	+ ------ + ----- + --------- + ------- + ----------------- +		+ ------ + ----- + --------- + ------- +
	| 8 bits | 1 bit | 1 bit | 32 bits | Last tile, if any |		| 8 bits | 1 bit | 1 bit | 32 bits |
	Figure 12: All-1 SCHC ACK detailed format for the last fragment.		Figure 12: All-1 SCHC Message: the last fragment.
	5.6.3.3. SCHC acknowledge		5.6.3.3. SCHC acknowledge
	| FPort | LoRaWAN payload |		| FPort | LoRaWAN payload |
	+ ------ + ---------------------------------- +		+ ------ + ---------------------------------- +
	| RuleID | W | C = b'1 | Padding b'000000 |		| RuleID | W | C = b'1 | Padding b'000000 |
	+ ------ + ----- + ------- + ---------------- +		+ ------ + ----- + ------- + ---------------- +
	| 8 bits | 1 bit | 1 bit | 6 bits |		| 8 bits | 1 bit | 1 bit | 6 bits |
	Figure 13: SCHC ACK format, RCS is correct.		Figure 13: SCHC ACK format, RCS is correct.
	5.6.3.4. Receiver-Abort		5.6.3.4. Receiver-Abort
	| FPort | LoRaWAN payload |		| FPort | LoRaWAN payload |
	+ ------ + ---------------------------------------------- +		+ ------ + ---------------------------------------------- +
	| RuleID | W = b'1 | C = b'1 | b'111111 | 0xFF (all 1's) |		| RuleID | W = b'1 | C = b'1 | b'111111 | 0xFF (all 1's) |
	+ ------ + ------- + ------- + -------- + --------------- +		+ ------ + ------- + ------- + -------- + --------------- +
	| 8 bits | 1 bit | 1 bits | 6 bits | 8 bits |		| 8 bits | 1 bit | 1 bits | 6 bits | 8 bits |
	next L2 Word boundary ->| <-- L2 Word --> |		next L2 Word boundary ->| <-- L2 Word --> |
	Figure 14: Receiver-Abort packet (following an all-1 packet with		Figure 14: Receiver-Abort packet (following an All-1 SCHC Fragment
	incorrect RCS).		with incorrect RCS).
	Class A and Class B or Class C end-devices do not manage		Class A and Class B or Class C end-devices do not manage
	retransmissions and timers in the same way.		retransmissions and timers in the same way.
	5.6.3.5. Class A end-devices		5.6.3.5. Class A end-devices
	Class A end-devices can only receive in an RX slot following the		Class A end-devices can only receive in an RX slot following the
	transmission of an uplink. Therefore there cannot be a concept of		transmission of an uplink. Therefore there cannot be a concept of
	"retransmission timer" for an SCHC gateway. The SCHC gateway cannot		"retransmission timer" for an SCHC gateway. The SCHC gateway cannot
	initiate communication to a Class A end-device.		initiate communication to a Class A end-device.
	The device replies with an ACK message to every single fragment		The device replies with an ACK message to every single fragment
	received from the SCHC gateway (because the window size is 1).		received from the SCHC gateway (because the window size is 1).
	Following the reception of a FCN=0 fragment (fragment that is not the		Following the reception of a FCN=0 fragment (fragment that is not the
	last fragment of the packet or ACK-request, but the end of a window),		last fragment of the packet or SCHC ACK REQ, but the end of a
	the device MUST transmit the SCHC ACK fragment until it receives the		window), the device MUST transmit the SCHC ACK fragment until it
	fragment of the next window. The device SHALL transmit up to		receives the fragment of the next window. The device SHALL transmit
	MAX_ACK_REQUESTS ACK messages before aborting. The device should		up to MAX_ACK_REQUESTS ACK messages before aborting. The device
	transmit those ACK as soon as possible while taking into		should transmit those ACK as soon as possible while taking into
	consideration potential local radio regulation on duty-cycle, to		consideration potential local radio regulation on duty-cycle, to
	progress the fragmentation session as quickly as possible. The ACK		progress the fragmentation session as quickly as possible. The ACK
	bitmap is 1 bit long and is always 1.		bitmap is 1 bit long and is always 1.
	Following the reception of an FCN=All-1 fragment (the last fragment		Following the reception of an FCN=All-1 fragment (the last fragment
	of a datagram) and if the RCS is correct, the device SHALL transmit		of a datagram) and if the RCS is correct, the device SHALL transmit
	the ACK with the "RCS is correct" indicator bit set (C=1). This		the ACK with the "RCS is correct" indicator bit set (C=1). This
	message might be lost therefore the SCHC gateway MAY request a		message might be lost therefore the SCHC gateway MAY request a
	retransmission of this ACK in the next downlink. The device SHALL		retransmission of this ACK in the next downlink. The device SHALL
	keep this ACK message in memory until it receives a downlink, on SCHC		keep this ACK message in memory until it receives a downlink, on SCHC
	FPortDown from the SCHC gateway different from an ACK-request: it		FPortDown from the SCHC gateway different from an SCHC ACK REQ: it
	indicates that the SCHC gateway has received the ACK message.		indicates that the SCHC gateway has received the ACK message.
	Following the reception of a FCN=All-1 fragment (the last fragment of
	a datagram), if all fragments have been received and the RCS is not
	correct, the device SHALL transmit a Receiver-Abort fragment. The
	device SHALL keep this Abort message in memory until it receives a
	downlink, on SCHC FPortDown, from the SCHC gateway different from an
	ACK-request indicating that the SCHC gateway has received the Abort
	message. The fragmentation receiver (device) does not implement
	retransmission timer and inactivity timer.
	The fragmentation sender (the SCHC gateway) implements an inactivity		The fragmentation sender (the SCHC gateway) implements an inactivity
	timer with a default duration of 12 hours. Once a fragmentation		timer with a default duration of 12 hours. Once a fragmentation
	session is started, if the SCHC gateway has not received any ACK or		session is started, if the SCHC gateway has not received any ACK or
	Receiver-Abort message 12 hours after the last message from the		Receiver-Abort message 12 hours after the last message from the
	device was received, the SCHC gateway MAY flush the fragmentation		device was received, the SCHC gateway MAY flush the fragmentation
	context. For devices with very low transmission rates (example 1		context. For devices with very low transmission rates (example 1
	packet a day in normal operation) , that duration may be extended,		packet a day in normal operation) , that duration may be extended,
	but this is application specific.		but this is application specific.
	5.6.3.6. Class B or Class C end-devices		5.6.3.6. Class B or Class C end-devices
	Class B and Class C end-devices can receive in scheduled RX slots or		Class B and Class C end-devices can receive in scheduled RX slots or
	in RX slots following the transmission of an uplink. The device		in RX slots following the transmission of an uplink. The device
	replies with an ACK message to every single fragment received from		replies with an ACK message to every single fragment received from
	the SCHC gateway (because the window size is 1). Following the		the SCHC gateway (because the window size is 1). Following the
	reception of an FCN=0 fragment (fragment that is not the last		reception of an FCN=0 fragment (fragment that is not the last
	fragment of the packet or ACK-request), the device MUST always		fragment of the packet or SCHC ACK REQ), the device MUST always
	transmit the corresponding SCHC ACK message even if that fragment has		transmit the corresponding SCHC ACK message even if that fragment has
	already been received. The ACK bitmap is 1 bit long and is always 1.		already been received. The ACK bitmap is 1 bit long and is always 1.
	If the SCHC gateway receives this ACK, it proceeds to send the next		If the SCHC gateway receives this ACK, it proceeds to send the next
	window fragment. If the retransmission timer elapses and the SCHC		window fragment. If the retransmission timer elapses and the SCHC
	gateway has not received the ACK of the current window it retransmits		gateway has not received the ACK of the current window it retransmits
	the last fragment. The SCHC gateway tries retransmitting up to		the last fragment. The SCHC gateway tries retransmitting up to
	MAX_ACK_REQUESTS times before aborting.		MAX_ACK_REQUESTS times before aborting.
	Following the reception of an FCN=All-1 fragment (the last fragment		Following the reception of an FCN=All-1 fragment (the last fragment
	of a datagram) and if the RCS is correct, the device SHALL transmit		of a datagram) and if the RCS is correct, the device SHALL transmit
	the ACK with the "RCS is correct" indicator bit set. If the SCHC		the ACK with the "RCS is correct" indicator bit set. If the SCHC
	gateway receives this ACK, the current fragmentation session has		gateway receives this ACK, the current fragmentation session has
	succeeded and its context can be cleared.		succeeded and its context can be cleared.
	If the retransmission timer elapses and the SCHC gateway has not		If the retransmission timer elapses and the SCHC gateway has not
	received the SCHC ACK it retransmits the last fragment with the		received the SCHC ACK it retransmits the last fragment with the
	payload (not an ACK-request without payload). The SCHC gateway tries		payload (not an SCHC ACK REQ without payload). The SCHC gateway
	retransmitting up to MAX_ACK_REQUESTS times before aborting.		tries retransmitting up to MAX_ACK_REQUESTS times before aborting.
	Following the reception of an FCN=All-1 fragment (the last fragment		Following the reception of an FCN=All-1 fragment (the last fragment
	of a datagram), if all fragments have been received and if the RCS is		of a datagram), if all fragments have been received and if the RCS is
	NOT correct, the device SHALL transmit a Receiver-Abort fragment.		NOT correct, the device SHALL transmit a Receiver-Abort fragment.
	The retransmission timer is used by the SCHC gateway (the sender),		The retransmission timer is used by the SCHC gateway (the sender),
	the optimal value is very much application specific but here are some		the optimal value is very much application specific but here are some
	recommended default values. For Class B end-devices, this timer		recommended default values. For Class B end-devices, this timer
	trigger is a function of the periodicity of the Class B ping slots.		trigger is a function of the periodicity of the Class B ping slots.
	The RECOMMENDED value is equal to 3 times the Class B ping slot		The RECOMMENDED value is equal to 3 times the Class B ping slot
	periodicity. For Class C end-devices which are nearly constantly		periodicity. For Class C end-devices which are nearly constantly
	receiving, the RECOMMENDED value is 30 seconds. This means that the		receiving, the RECOMMENDED value is 30 seconds. This means that the
	end-device shall try to transmit the ACK within 30 seconds of the		end-device shall try to transmit the ACK within 30 seconds of the
	reception of each fragment. The inactivity timer is implemented by		reception of each fragment. The inactivity timer is implemented by
	the end-device to flush the context in-case it receives nothing from		the end-device to flush the context in case it receives nothing from
	the SCHC gateway over an extended period of time. The RECOMMENDED		the SCHC gateway over an extended period of time. The RECOMMENDED
	value is 12 hours for both Class B and Class C end-devices.		value is 12 hours for both Class B and Class C end-devices.
	6. Security considerations		6. Security considerations
	This document is only providing parameters that are expected to be		This document is only providing parameters that are expected to be
	better suited for LoRaWAN networks for		better suited for LoRaWAN networks for
	[I-D.ietf-lpwan-ipv6-static-context-hc]. As such, this document does		[I-D.ietf-lpwan-ipv6-static-context-hc]. IID security is discussed
	not contribute to any new security issues in addition to those		in Section 5.3.As such, this document does not contribute to any new
	identified in [I-D.ietf-lpwan-ipv6-static-context-hc].		security issues in addition to those identified in
			[I-D.ietf-lpwan-ipv6-static-context-hc].
	Acknowledgements		Acknowledgements
	Thanks to all those listed in the Contributors section for the		Thanks to all those listed in the Contributors section for the
	excellent text, insightful discussions, reviews and suggestions.		excellent text, insightful discussions, reviews and suggestions, and
			also to (in alphabetical order) Dominique Barthel, Arunprabhu
			Kandasamy, Rodrigo Munoz, Alexander Pelov, Pascal Thubert, Laurent
			Toutain for useful design considerations, reviews and comments.
	Contributors		Contributors
	Contributors ordered by family name.		Contributors ordered by family name.
	o ins: V. Audebert name: Vincent AUDEBERT org: EDF R&D street: 7 bd		Vincent Audebert
	Gaspard Monge city: 91120 PALAISEAU country: FRANCE email:		EDF R&D
	vincent.audebert@edf.fr		Email: vincent.audebert@edf.fr
	o ins: J. Catalano name: Julien Catalano org: Kerlink street: 1 rue		Julien Catalano
	Jacqueline Auriol city: 35235 Thorigne-Fouillard country: France		Kerlink
	email: j.catalano@kerlink.fr		Email: j.catalano@kerlink.fr
	o ins: M. Coracin name: Michael Coracin org: Semtech street: 14		Michael Coracin
	Chemin des Clos city: Meylan country: France email:		Semtech
	mcoracin@semtech.com		Email: mcoracin@semtech.com
	o ins: M. Le Gourrierec name: Marc Le Gourrierec org: SagemCom		Marc Le Gourrierec
	street: 250 Route de l'Empereur city: 92500 Rueil Malmaison		Sagemcom
	country: FRANCE email: marc.legourrierec@sagemcom.com		Email: marc.legourrierec@sagemcom.com
	o ins: N. Sornin name: Nicolas Sornin org: Semtech street: 14		Nicolas Sornin
	Chemin des Clos city: Meylan country: France email:		Semtech
	nsornin@semtech.com		Email: nsornin@semtech.com
	o ins: A. Yegin name: Alper Yegin org: Actility street: . city:		Alper Yegin
	Paris, Paris country: France email: alper.yegin@actility.com		Actility
			Email: alper.yegin@actility.com
	9. References		9. References
	9.1. Normative References		9.1. Normative References
			[I-D.ietf-lpwan-ipv6-static-context-hc]
			Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and J.
			Zuniga, "Static Context Header Compression (SCHC) and
			fragmentation for LPWAN, application to UDP/IPv6", draft-
			ietf-lpwan-ipv6-static-context-hc-24 (work in progress),
			December 2019.
	[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>.
	[RFC3385] Sheinwald, D., Satran, J., Thaler, P., and V. Cavanna,		[RFC3385] Sheinwald, D., Satran, J., Thaler, P., and V. Cavanna,
	"Internet Protocol Small Computer System Interface (iSCSI)		"Internet Protocol Small Computer System Interface (iSCSI)
	Cyclic Redundancy Check (CRC)/Checksum Considerations",		Cyclic Redundancy Check (CRC)/Checksum Considerations",
	RFC 3385, DOI 10.17487/RFC3385, September 2002,		RFC 3385, DOI 10.17487/RFC3385, September 2002,
	<https://www.rfc-editor.org/info/rfc3385>.		<https://www.rfc-editor.org/info/rfc3385>.
	[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing		[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
	Architecture", RFC 4291, DOI 10.17487/RFC4291, February		Architecture", RFC 4291, DOI 10.17487/RFC4291, February
	2006, <https://www.rfc-editor.org/info/rfc4291>.		2006, <https://www.rfc-editor.org/info/rfc4291>.
			[RFC4493] Song, JH., Poovendran, R., Lee, J., and T. Iwata, "The
			AES-CMAC Algorithm", RFC 4493, DOI 10.17487/RFC4493, June
			2006, <https://www.rfc-editor.org/info/rfc4493>.
	[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,		[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
	"Transmission of IPv6 Packets over IEEE 802.15.4		"Transmission of IPv6 Packets over IEEE 802.15.4
	Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,		Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
	<https://www.rfc-editor.org/info/rfc4944>.		<https://www.rfc-editor.org/info/rfc4944>.
	[RFC5795] Sandlund, K., Pelletier, G., and L-E. Jonsson, "The RObust		[RFC5795] Sandlund, K., Pelletier, G., and L-E. Jonsson, "The RObust
	Header Compression (ROHC) Framework", RFC 5795,		Header Compression (ROHC) Framework", RFC 5795,
	DOI 10.17487/RFC5795, March 2010,		DOI 10.17487/RFC5795, March 2010,
	<https://www.rfc-editor.org/info/rfc5795>.		<https://www.rfc-editor.org/info/rfc5795>.
	[RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6		[RFC7136] Carpenter, B. and S. Jiang, "Significance of IPv6
	Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136,		Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136,
	February 2014, <https://www.rfc-editor.org/info/rfc7136>.		February 2014, <https://www.rfc-editor.org/info/rfc7136>.
			[RFC8064] Gont, F., Cooper, A., Thaler, D., and W. Liu,
			"Recommendation on Stable IPv6 Interface Identifiers",
			RFC 8064, DOI 10.17487/RFC8064, February 2017,
			<https://www.rfc-editor.org/info/rfc8064>.
			[RFC8065] Thaler, D., "Privacy Considerations for IPv6 Adaptation-
			Layer Mechanisms", RFC 8065, DOI 10.17487/RFC8065,
			February 2017, <https://www.rfc-editor.org/info/rfc8065>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[RFC8376] Farrell, S., Ed., "Low-Power Wide Area Network (LPWAN)		[RFC8376] Farrell, S., Ed., "Low-Power Wide Area Network (LPWAN)
	Overview", RFC 8376, DOI 10.17487/RFC8376, May 2018,		Overview", RFC 8376, DOI 10.17487/RFC8376, May 2018,
	<https://www.rfc-editor.org/info/rfc8376>.		<https://www.rfc-editor.org/info/rfc8376>.
	9.2. Informative References		9.2. Informative References
	[I-D.ietf-lpwan-ipv6-static-context-hc]
	Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and J.
	Zuniga, "Static Context Header Compression (SCHC) and
	fragmentation for LPWAN, application to UDP/IPv6", draft-
	ietf-lpwan-ipv6-static-context-hc-22 (work in progress),
	October 2019.
	[lora-alliance-remote-multicast-set]		[lora-alliance-remote-multicast-set]
	Alliance, L., "LoRaWAN Remote Multicast Setup		Alliance, L., "LoRaWAN Remote Multicast Setup
	Specification Version 1.0.0", <https://lora-		Specification Version 1.0.0", <https://lora-
	alliance.org/sites/default/files/2018-09/		alliance.org/sites/default/files/2018-09/
	remote_multicast_setup_v1.0.0.pdf>.		remote_multicast_setup_v1.0.0.pdf>.
	[lora-alliance-spec]		[lora-alliance-spec]
	Alliance, L., "LoRaWAN Specification Version V1.0.3",		Alliance, L., "LoRaWAN Specification Version V1.0.3",
	<https://lora-alliance.org/sites/default/files/2018-07/		<https://lora-alliance.org/sites/default/files/2018-07/
	lorawan1.0.3.pdf>.		lorawan1.0.3.pdf>.
	Appendix A. Examples		Appendix A. Examples
	A.1. Uplink - Compression example - No fragmentation		A.1. Uplink - Compression example - No fragmentation
	Figure 15 is representing an applicative payload going through SCHC,		This example represents an applicative payload going through SCHC
	no fragmentation required		over LoRaWAN, no fragmentation required
	An applicative payload of 78 bytes is passed to SCHC compression layer		An applicative payload of 78 bytes is passed to SCHC compression
	using rule 1, allowing to compress it to 40 bytes and 5 bits: 1 byte		layer. Rule 1 is used by C/D layer, allowing to compress it to 40
	ruleID, 21 bits residue + 37 bytes payload.		bytes and 5 bits: 1 byte RuleID, 21 bits residue + 37 bytes payload.
	| RuleID | Compression residue | Payload | Padding=b'000 |		| RuleID | Compression residue | Payload | Padding=b'000 |
	+ ------ + ------------------- + --------- + ------------- +		+ ------ + ------------------- + --------- + ------------- +
	| 1 | 21 bits | 38 bytes | 3 bits |		| 1 | 21 bits | 37 bytes | 3 bits |
	The current LoRaWAN MTU is 51 bytes, although 2 bytes FOpts are used by		Figure 15: Uplink example: SCHC Message
	LoRaWAN protocol: 49 bytes are available for SCHC payload; no need for
	fragmentation. The payload will be transmitted through FPort = 1		The current LoRaWAN MTU is 51 bytes, although 2 bytes FOpts are used
			by LoRaWAN protocol: 49 bytes are available for SCHC payload; no need
			for fragmentation. The payload will be transmitted through FPort =
			1.
	| LoRaWAN Header | LoRaWAN payload (40 bytes) |		| LoRaWAN Header | LoRaWAN payload (40 bytes) |
	+ ------------------------- + --------------------------------------- +		+ ------------------------- + --------------------------------------- +
	| | FOpts | RuleID=1 | Compression | Payload | Padding=b'000 |		| | FOpts | RuleID=1 | Compression | Payload | Padding=b'000 |
	| | | | residue | | |		| | | | residue | | |
	+ ---- + ------- + -------- + ----------- + --------- + ------------- +		+ ---- + ------- + -------- + ----------- + --------- + ------------- +
	| XXXX | 2 bytes | 1 byte | 21 bits | 37 bytes | 3 bits |		| XXXX | 2 bytes | 1 byte | 21 bits | 37 bytes | 3 bits |
	Figure 15: Uplink example: compression without fragmentation		Figure 16: Uplink example: LoRaWAN packet
	A.2. Uplink - Compression and fragmentation example		A.2. Uplink - Compression and fragmentation example
	Figure 16 is representing an applicative payload going through SCHC,		This example represents an applicative payload going through SCHC,
	with fragmentation.		with fragmentation.
	An applicative payload of 478 bytes is passed to SCHC compression layer		An applicative payload of 478 bytes is passed to SCHC compression
	using rule 1, allowing to compress it to 282 bytes and 5 bits: 1 byte		layer. Rule 1 is used by C/D layer, allowing to compress it to 282
	ruleID, 21 bits residue + 279 bytes payload.		bytes and 5 bits: 1 byte RuleID, 21 bits residue + 279 bytes payload.
	| RuleID | Compression residue | Payload |		| RuleID | Compression residue | Payload |
	+ ------ + ------------------- + --------- +		+ ------ + ------------------- + --------- +
	| 1 | 21 bits | 279 bytes |		| 1 | 21 bits | 279 bytes |
	The current LoRaWAN MTU is 11 bytes, 0 bytes FOpts are used by LoRaWAN		Figure 17: Uplink example: SCHC Message
	protocol: 11 bytes are available for SCHC payload + 1 byte FPort field.
	SCHC header is 2 bytes (including FPort) so 1 tile is sent in first
	fragment.
	| LoRaWAN Header | LoRaWAN payload (11 bytes) |		The current LoRaWAN MTU is 11 bytes, 0 bytes FOpts are used by
	+ -------------------------- + -------------------------- +		LoRaWAN protocol: 11 bytes are available for SCHC payload + 1 byte
	| | RuleID=20 | W | FCN | 1 tile |		FPort field. SCHC header is 2 bytes (including FPort) so 1 tile is
	+ -------------- + --------- + ----- + ------ + --------- +		sent in first fragment.
	| XXXX | 1 byte | 0 0 | 62 | 10 bytes |
	Content of the tile is:		| LoRaWAN Header | LoRaWAN payload (11 bytes) |
	| RuleID | Compression residue | Payload |		+ -------------------------- + -------------------------- +
	+ ------ + ------------------- + ----------------- +		| | RuleID=20 | W | FCN | 1 tile |
	| 1 | 21 bits | 6 byte + 3 bits |		+ -------------- + --------- + ----- + ------ + --------- +
			| XXXX | 1 byte | 0 0 | 62 | 10 bytes |
	Next transmission MTU is 11 bytes, although 2 bytes FOpts are used by		Figure 18: Uplink example: LoRaWAN packet 1
	LoRaWAN protocol: 9 bytes are available for SCHC payload + 1 byte FPort
	field, a tile does not fit inside so LoRaWAN stack will send only FOpts.
	Next transmission MTU is 242 bytes, 4 bytes FOpts. 23 tiles are transmitted:		Content of the tile is:
			| RuleID | Compression residue | Payload |
			+ ------ + ------------------- + ----------------- +
			| 1 | 21 bits | 6 byte + 3 bits |
	| LoRaWAN Header | LoRaWAN payload (231 bytes) |		Figure 19: Uplink example: LoRaWAN packet 1 - Tile content
	+ --------------------------------------+ --------------------------- +
	| | FOpts | RuleID=20 | W | FCN | 23 tiles |
	+ -------------- + ------- + ---------- + ----- + ----- + ----------- +
	| XXXX | 4 bytes | 1 byte | 0 0 | 61 | 230 bytes |
	Next transmission MTU is 242 bytes, no FOpts. All 5 remaining tiles are		Next transmission MTU is 11 bytes, although 2 bytes FOpts are used by
	transmitted, the last tile is only 2 bytes + 5 bits. Padding is added for		LoRaWAN protocol: 9 bytes are available for SCHC payload + 1 byte
	the remaining 3 bits.		FPort field, a tile does not fit inside so LoRaWAN stack will send
			only FOpts.
	| LoRaWAN Header | LoRaWAN payload (44 bytes) |		Next transmission MTU is 242 bytes, 4 bytes FOpts. 23 tiles are
	+ ---- + -----------+ ----------------------------------------------- +		transmitted:
	| | RuleID=20 | W | FCN | 5 tiles | Padding=b'000 |
			| LoRaWAN Header | LoRaWAN payload (231 bytes) |
			+ --------------------------------------+ --------------------------- +
			| | FOpts | RuleID=20 | W | FCN | 23 tiles |
			+ -------------- + ------- + ---------- + ----- + ----- + ----------- +
			| XXXX | 4 bytes | 1 byte | 0 0 | 61 | 230 bytes |
			Figure 20: Uplink example: LoRaWAN packet 2
			Next transmission MTU is 242 bytes, no FOpts. All 5 remaining tiles
			are transmitted, the last tile is only 2 bytes + 5 bits. Padding is
			added for the remaining 3 bits.
			| LoRaWAN Header | LoRaWAN payload (44 bytes) |
			+ ---- + -----------+ ------------------------------------------------- +
			| | RuleID=20 | W | FCN | 5 tiles | Padding=b'000 |
	+ ---- + ---------- + ----- + ----- + ----------------- + ------------- +		+ ---- + ---------- + ----- + ----- + ----------------- + ------------- +
	| XXXX | 1 byte | 0 0 | 38 | 42 bytes + 5 bits | 3 bits |		| XXXX | 1 byte | 0 0 | 38 | 42 bytes + 5 bits | 3 bits |
	All packets have been received by the SCHC gateway, computed RCS is		Figure 21: Uplink example: LoRaWAN packet 3
	correct so the following ACK is sent to the device:
	| LoRaWAN Header | LoRaWAN payload |		Then All-1 message can be transmitted:
	+ -------------- + --------- + ------------------- +
	| | RuleID=20 | W | C | Padding |
	+ -------------- + --------- + ----- + - + ------- +
	| XXXX | 1 byte | 0 0 | 1 | 5 bits |
	Figure 16: Uplink example: compression and fragmentation		| LoRaWAN Header | LoRaWAN payload (44 bytes) |
			+ ---- + -----------+ -------------------------- +
			| | RuleID=20 | W | FCN | RCS |
			+ ---- + ---------- + ----- + ----- + ---------- +
			| XXXX | 1 byte | 0 0 | 63 | 4 bytes |
			Figure 22: Uplink example: LoRaWAN packet 4 - All-1 message
			All packets have been received by the SCHC gateway, computed RCS is
			correct so the following ACK is sent to the device by the SCHC
			receiver:
			| LoRaWAN Header | LoRaWAN payload |
			+ -------------- + --------- + ------------------- +
			| | RuleID=20 | W | C | Padding |
			+ -------------- + --------- + ----- + - + ------- +
			| XXXX | 1 byte | 0 0 | 1 | 5 bits |
			Figure 23: Uplink example: LoRaWAN packet 5 - SCHC ACK
	A.3. Downlink		A.3. Downlink
	An applicative payload of 443 bytes is passed to SCHC compression layer		An applicative payload of 443 bytes is passed to SCHC compression
	using rule 1, allowing to compress it to 130 bytes and 5 bits: 1 byte		layer. Rule 1 is used by C/D layer, allowing to compress it to 130
	ruleId, 21 bits residue + 127 bytes payload.		bytes and 5 bits: 1 byte RuleID, 21 bits residue + 127 bytes payload.
	| RuleID | Compression residue | Payload |		| RuleID | Compression residue | Payload |
	+ ------ + ------------------- + --------- +		+ ------ + ------------------- + --------- +
	| 1 | 21 bits | 127 bytes |		| 1 | 21 bits | 127 bytes |
	The current LoRaWAN MTU is 51 bytes, no FOpts are used by LoRaWAN		Figure 24: Downlink example: SCHC Message
	protocol: 48 bytes are available for SCHC payload + FPort field => it
	has to be fragmented.
	| LoRaWAN Header | LoRaWAN payload (51 bytes) |		The current LoRaWAN MTU is 51 bytes, no FOpts are used by LoRaWAN
	+ ---- + ---------- + --------------------------------------------- +		protocol: 51 bytes are available for SCHC payload + FPort field => it
	| | RuleID=21 | W | FCN | 1 tile | Padding=b'000000 |		has to be fragmented.
	+ ---- + ---------- + --- + --- + -------------- + ---------------- +
	| XXXX | 1 byte | 0 | 0 | 50 bytes | 6 bits |
	Content of the tile is:		| LoRaWAN Header | LoRaWAN payload (51 bytes) |
	| RuleID | Compression residue | Payload |		+ ---- + ---------- + -------------------------------------- +
	+ ------ + ------------------- + ------------------ +		| | RuleID=21 | W = 0 | FCN = 0 | 1 tile |
	| 1 | 21 bits | 46 bytes + 3 bits |		+ ---- + ---------- + ------ + ------- + ------------------- +
			| XXXX | 1 byte | 1 bit | 1 bit | 50 bytes and 6 bits |
	The receiver answers with an SCHC ACK		Figure 25: Downlink example: LoRaWAN packet 1 - SCHC Fragment 1
	| FPortDown | LoRaWAN payload |		Content of the tile is:
	+ --------- + ---------------------------------- +
	| RuleID | W = 0 | C = b'1 | Padding=b'000000 |
	+ --------- + ----- + ------- + ---------------- +
	| 1 byte | 1 bit | 1 bit | 6 bits |
	The second downlink is sent, two FOpts:		| RuleID | Compression residue | Payload |
			+ ------ + ------------------- + ------------------ +
			| 1 | 21 bits | 48 bytes and 1 bit |
	| LoRaWAN Header | LoRaWAN payload (49 bytes) |		Figure 26: Downlink example: LoRaWAN packet 1: Tile content
	+ --------------------------- + ------------------ + ---------------- +
	| | FOpts | RuleID=21 | W | FCN | 1 tile | Padding=b'000000 |
	+ ---- + ------- + ---------- + - + --- + -------- + ---------------- +
	| XXXX | 2 bytes | 1 byte | 1 | 0 | 48 bytes | 6 bits |
	The receiver answers with an SCHC ACK
	| FPortDown | LoRaWAN payload |		The receiver answers with a SCHC ACK:
	+ --------- + ---------------------------------- +
	| RuleID | W = 1 | C = b'1 | Padding=b'000000 |
	+ --------- + ----- + ------- + ---------------- +
	| 1 byte | 1 bit | 1 bit | 6 bits |
	The last downlink is sent, no FOpts:		| LoRaWAN Header | LoRaWAN payload |
			+ ---- + --------- + -------------------------------- +
			| | RuleID=21 | W = 0 | C = 1 | Padding=b'000000 |
			+ ---- + --------- + ----- + ----- + ---------------- +
			| XXXX | 1 byte | 1 bit | 1 bit | 6 bits |
	| LoRaWAN Header | LoRaWAN payload (33 bytes) |		Figure 27: Downlink example: LoRaWAN packet 2 - SCHC ACK
	+ ---- + ---------- + ----------------------------------------------- +
	| | RuleID=21 | W | FCN | 1 tile | Padding=b'0 |
	+ ---- + ---------- + --- + --- + --------------------- + ----------- +
	| XXXX | 1 byte | 0 | 1 | 32 bytes + 5 bits | 1 bit |
	The receiver answers with an SCHC ACK		The second downlink is sent, two FOpts:
	| FPortDown | LoRaWAN payload |		| LoRaWAN Header | LoRaWAN payload (49 bytes) |
	+ --------- + ---------------------------------- +		+ --------------------------- + ------------------------------------- +
	| RuleID | W = 0 | C = b'1 | Padding=b'000000 |		| | FOpts | RuleID=21 | W = 1 | FCN = 0 | 1 tile |
	+ --------- + ----- + ------- + ---------------- +		+ ---- + ------- + ---------- + ----- + ------- + ------------------- +
	| 1 byte | 1 bit | 1 bit | 6 bits |		| XXXX | 2 bytes | 1 byte | 1 bit | 1 bit | 48 bytes and 6 bits |
	Figure 17: Downlink example: compression and fragmentation		Figure 28: Downlink example: LoRaWAN packet 3 - SCHC Fragment 2
	Appendix B. Note		The receiver answers with an SCHC ACK:
			| LoRaWAN Header | LoRaWAN payload |
			+ ---- + --------- + -------------------------------- +
			| | RuleID=21 | W = 1 | C = 1 | Padding=b'000000 |
			+ ---- + --------- + ----- + ----- + ---------------- +
			| XXXX | 1 byte | 1 bit | 1 bit | 6 bits |
			Figure 29: Downlink example: LoRaWAN packet 4 - SCHC ACK
			The last downlink is sent, no FOpts:
			| LoRaWAN Header | LoRaWAN payload (37 bytes) |
			+ ---- + --------- + ----------------------------------------------------------------- +
			| | RuleID=21 | W = 0 | FCN = 1 | RCS | 1 tile | Padding=b'00000 |
			+ ---- + --------- + ------- + ------- + ------- + ----------------- + --------------- +
			| XXXX | 1 byte | 1 bit | 1 bit | 4 bytes | 31 bytes + 1 bits | 5 bits |
			Figure 30: Uplink example: LoRaWAN packet 5 - All-1 message
			The receiver answers to the sender with an SCHC ACK:
			| LoRaWAN Header | LoRaWAN payload |
			+ ---- + --------- + -------------------------------- +
			| | RuleID=21 | W = 0 | C = 1 | Padding=b'000000 |
			+ ---- + --------- + ----- + ----- + ---------------- +
			| XXXX | 1 byte | 1 bit | 1 bit | 6 bits |
			Figure 31: Uplink example: LoRaWAN packet 6 - SCHC ACK
	Authors' Addresses		Authors' Addresses
	Olivier Gimenez (editor)		Olivier Gimenez (editor)
	Semtech		Semtech
	14 Chemin des Clos		14 Chemin des Clos
	Meylan		Meylan
	France		France
	Email: ogimenez@semtech.com		Email: ogimenez@semtech.com
End of changes. 95 change blocks.
	270 lines changed or deleted		360 lines changed or added
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