< draft-ietf-lpwan-coap-static-context-hc-02.txt		draft-ietf-lpwan-coap-static-context-hc-03.txt >
	lpwan Working Group A. Minaburo		lpwan Working Group A. Minaburo
	Internet-Draft Acklio		Internet-Draft Acklio
	Intended status: Informational L. Toutain		Intended status: Informational L. Toutain
	Expires: March 10, 2018 Institut MINES TELECOM ; IMT Atlantique		Expires: September 5, 2018 Institut MINES TELECOM; IMT Atlantique
	September 06, 2017		March 04, 2018
	LPWAN Static Context Header Compression (SCHC) for CoAP		LPWAN Static Context Header Compression (SCHC) for CoAP
	draft-ietf-lpwan-coap-static-context-hc-02		draft-ietf-lpwan-coap-static-context-hc-03
	Abstract		Abstract
	This draft defines the way SCHC header compression can be applied to		This draft defines the way SCHC header compression can be applied to
	CoAP headers. CoAP header structure differs from IPv6 and UDP		CoAP headers. CoAP header structure differs from IPv6 and UDP
	protocols since the CoAP Header is flexible header with a variable		protocols since the CoAP Header is flexible header with a variable
	number of options themself of a variable length. Another important		number of options themself of a variable length. Another important
	difference is the asymmetry in the header information used for		difference is the asymmetry in the header information used for
	request and response messages. This draft takes into account the		request and response messages. This draft takes into account the
	fact that a thing can play the role of a CoAP client, a CoAP client		fact that a thing can play the role of a CoAP client, a CoAP client
	skipping to change at page 1, line 38 ¶		skipping to change at page 1, line 38 ¶
	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 March 10, 2018.		This Internet-Draft will expire on September 5, 2018.
	Copyright Notice		Copyright Notice
	Copyright (c) 2017 IETF Trust and the persons identified as the		Copyright (c) 2018 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 43 ¶		skipping to change at page 2, line 43 ¶
	7. Protocol analysis . . . . . . . . . . . . . . . . . . . . . . 13		7. Protocol analysis . . . . . . . . . . . . . . . . . . . . . . 13
	8. Examples of CoAP header compression . . . . . . . . . . . . . 14		8. Examples of CoAP header compression . . . . . . . . . . . . . 14
	8.1. Mandatory header with CON message . . . . . . . . . . . . 14		8.1. Mandatory header with CON message . . . . . . . . . . . . 14
	8.2. Complete exchange . . . . . . . . . . . . . . . . . . . . 16		8.2. Complete exchange . . . . . . . . . . . . . . . . . . . . 16
	9. Normative References . . . . . . . . . . . . . . . . . . . . 17		9. Normative References . . . . . . . . . . . . . . . . . . . . 17
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
	1. Introduction		1. Introduction
	CoAP [rfc7252] is an implementation of the REST architecture for		CoAP [rfc7252] is an implementation of the REST architecture for
	constrained devices. Gateway between CoAP and HTTP can be easily		constrained devices. A Gateway between CoAP and HTTP can be easily
	built since both protocols uses the same address space (URL), caching		built since both protocols uses the same address space (URL), caching
	mechanisms and methods.		mechanisms and methods.
	Nevertheless, if limited, the size of a CoAP header may be too large		Nevertheless, if limited, the size of a CoAP header may be too large
	for LPWAN constraints and some compression may be needed to reduce		for LPWAN constraints and some compression may be needed to reduce
	the header size.		the header size.
	[I-D.toutain-lpwan-ipv6-static-context-hc] defines a header		[I-D.toutain-lpwan-ipv6-static-context-hc] defines a header
	compression mechanism for LPWAN network based on a static context.		compression mechanism for LPWAN network based on a static context.
	The context is said static since the element values composing the		The context is said static since the field description composing the
	context are not learned during the packet exchanges but are		Rules and the context are not learned during the packet exchanges but
	previously defined. The context(s) is(are) known by both ends before		are previously defined. The context(s) is(are) known by both ends
	transmission.		before transmission.
	A context is composed of a set of rules (contexts) that are		A context is composed of a set of rules that are referenced by Rule
	referenced by Rule IDs (identifiers). A rule contains an ordered		IDs (identifiers). A rule contains an ordered list of the fields
	list of the header fields containing a field ID (FID) and its		descriptions containing a field ID (FID) and its position when
	position when repeated, a direction indicator (DI) (upstream,		repeated, a direction indicator (DI) (upstream, downstream and
	downstream and bidirectional) and some associated Target Values (TV)		bidirectional) and some associated Target Values (TV) which are
	which are expected in the message header. A Matching Operator (MO)		expected in the message header. A Matching Operator (MO) is
	is associated to each header field description. The rule is selected		associated to each header field description. The rule is selected if
	if all the MOs fit the TVs. In that case, a Compression		all the MOs fit the TVs. In that case, a Compression/Decompression
	Decompression Function (CDF) associated to each field defines the		Action (CDA) associated to each field defines the link between the
	link between the compressed and decompressed value for each of the		compressed and decompressed value for each of the header fields.
	header fields.
	This document describes how the rules can be applied to CoAP flows. Compression of the		This document describes how the rules can be applied to CoAP flows.
	CoAP header may be done in conjunction with the above layers or independantly.		Compression of the CoAP header may be done in conjunction with the
			above layers or independantly.
	2. CoAP Compressing		2. CoAP Compressing
	CoAP differs from IPv6 and UDP protocols on the following		CoAP differs from IPv6 and UDP protocols on the following aspects:
	aspects:
	o IPv6 and UDP are symmetrical protocols. The same fields are found		o IPv6 and UDP are symmetrical protocols. The same fields are found
	in the request and in the response, only location in the header		in the request and in the response, only the location in the
	may vary (e.g. source and destination fields). A CoAP request is		header may vary (e.g. source and destination fields). A CoAP
	different from an response. For example, the URI-path option is		request is different from a response. For example, the URI-path
	mandatory in the request and is not found in the response, request		option is mandatory in the request and is not found in the
	may contain an Accept option and the response a Content-format		response, a request may contain an Accept option and the response
	option.		a Content-format option.
	Even when a field is "symmetric" (i.e. found in both directions)		Even when a field is "symmetric" (i.e. found in both directions)
	the values carried are different. For instance the Type field		the values carried are different. For instance the Type field
	will contain a CON value in the request and a ACK or RST value in		will contain a CON value in the request and a ACK or RST value in
	the response. Exploiting the asymmetry in compression will allow		the response. Exploiting the asymmetry in compression will allow
	to send no bit in the compressed request and a single bit in the		to send no bit in the compressed request and a single bit in the
	answer. Same behavior can be applied to the CoAP Code field (O.OX		answer. Same behavior can be applied to the CoAP Code field (O.OX
	code are present in the request and Y.ZZ in the answer).		code are present in the request and Y.ZZ in the answer).
	o CoAP also obeys to the client/server paradigm and the compression		o CoAP also obeys to the client/server paradigm and the compression
	rate can be different if the request is issued from a LPWAN node		rate can be different if the request is issued from an LPWAN node
	or from an non LPWAN device. For instance a Thing (ES) aware of		or from an non LPWAN device. For instance a Thing (ES) aware of
	LPWAN constraints can generate a 1 byte token, but a regular CoAP		LPWAN constraints can generate a 1 byte token, but a regular CoAP
	client will certainly send a larger token to the Thing. SCHC		client will certainly send a larger token to the Thing. SCHC
	compression will not modify the values to offer a better		compression will not modify the values to offer a better
	compression rate. Nevertheless a proxy placed before the		compression rate. Nevertheless a proxy placed before the
	compressor may change some field values to offer a better		compressor may change some field values to offer a better
	compression rate and maintain the necessary context for		compression rate and maintain the necessary context for
	interoperability with existing CoAP implementations.		interoperability with existing CoAP implementations.
	o In IPv6 and UDP header fields have a fixed size. In CoAP, Token		o In IPv6 and UDP header fields have a fixed size. In CoAP, Token
	size may vary from 0 to 8 bytes, length is given by a field in the		size may vary from 0 to 8 bytes, length is given by a field in the
	header. More systematically, the CoAP options are described using		header. More systematically, the CoAP options are described using
	the Type-Length-Value. When applying SCHC header compression.		the Type-Length-Value. When applying SCHC header compression.
	By sending compressed field information following the rule order,		By sending compressed field information following the rule order,
	SCHC offers a serialization/deserialization mechanism. Since a		SCHC offers a serialization/deserialization mechanism. Since a
	field exists to indicate the token length there is no ambiguity.		field exists to indicate the token length there is no ambiguity.
	For options, the rule indicates also the expected options found		For options, the rule indicates also the expected options found
	the int CoAP header. Therefore only the length is needed to		the int CoAP header. Therefore only the length is needed to
	recognise an option. The length will be send using the same CoAP		recognize an option. The length will be sent using the same CoAP
	encoding (size less than 12 are directly sent, higher values uses		encoding (size less than 12 are directly sent, higher values use
	the escape mechanisms defined by [rfc7252]). Delta Type is		the escape mechanisms defined by [rfc7252]). Delta Type is
	omitted, the value will be recovered by the decompressor. This		omitted, the value will be recovered by the decompressor. This
	reduce the option length of 4, 12 or 20 bits regarding the		reduces the option length of 4, 12 or 20 bits regarding the
	orignial size of the delta type encoding in the option.		original size of the delta type encoding in the option.
	o In CoAP headers a field can be duplicated several times, for		o In CoAP headers a field can be duplicated several times, for
	instances, elements of an URI (path or queries) or accepted		instances, elements of an URI (path or queries) or accepted
	formats. The position defined in a rule, associated to a Field		formats. The position defined in a rule, associated to a Field
	ID, can be used to identify the proper element.		ID, can be used to identify the proper element.
	3. Compression of CoAP header fields		3. Compression of CoAP header fields
	This section discusses of the compression of the different CoAP		This section discusses of the compression of the different CoAP
	header fields. These are just examples. The compression should take		header fields. These are just examples. The compression should take
	into account the nature of the traffic and not only the field values.		into account the nature of the traffic and not only the field values.
	Next chapter will define some compression rules for some common		Next chapter will define some compression rules for some common
	exchanges.		exchanges.
	3.1. CoAP version field (2 bits)		3.1. CoAP version field (2 bits)
	This field is bidirectional and can be elided during the SCHC		This field is bidirectional and can be elided during the SCHC
	compression, since it always contains the same value. It appears		compression, since it always contains the same value. It appears
	only in first position.		only in first position.
	FID Pos DI TV MO CDF		FID FL FP DI Value MO CDA Sent
	ver 1 bi 1 equal not-sent		ver 2 1 bi 1 equal not-sent
	3.2. CoAP type field		3.2. CoAP type field
	This field can be managed bidirectionally or unidirectionally.Several		This field can be managed bidirectionally or unidirectionally.Several
	strategies can be applied to this field regarding the values used:		strategies can be applied to this field regarding the values used:
	o If the ES is a client or a Server and non confirmable message are		o If the ES is a client or a Server and non confirmable message are
	used, the transmission of the Type field can be avoided:		used, the transmission of the Type field can be avoided:
	* Pos is always 1,		* Pos is always 1,
	* DI can either be "uplink" if the ES is a CoAP client or		* DI can either be "uplink" if the ES is a CoAP client or
	"downlink" if the ES is a CoAP server, or "bidirectional"		"downlink" if the ES is a CoAP server, or "bidirectional"
	* TV is set to the value,		* TV is set to the value,
	* MO is set to "equal"		* MO is set to "equal"
	* CDF is set to "not-sent".		* CDA is set to "not-sent".
	FID Pos DI TV MO CDF		FID FL FP DI Target Value MO CDA Sent
	type 1 bi NON equal not-sent		type 2 1 bi NON equal not-sent
	o If the ES is either a client or a Server and confirmable message		o If the ES is either a client or a Server and confirmable message
	are used, the DI can be used to elide the type on the request and		are used, the DI can be used to elide the type on the request and
	compress it to 1 bit on the response. The example above shows the		compress it to 1 bit on the response. The example above shows the
	rule for a ES acting as a client, directions need to be reversed		rule for a ES acting as a client, directions need to be reversed
	for a ES acting as a server.		for a ES acting as a server.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	type 1 up CON equal not-sent		type 2 1 up CON equal not-sent
	type 1 dw {0:ACK, 1:RST} match-mapping mapping-sent		type 2 1 dw [ACK,RST] match-mapping mapping-sent [1]
	o Otherwise if the ES is acting simultaneously as a client and a		o Otherwise if the ES is acting simultaneously as a client and a
	server and the rule handle these two traffics, Type field must be		server and the rule handle these two traffics, Type field must be
	sent uncompressed.		sent uncompressed.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	type 1 bi ignore send-value		type 2 1 bi ignore send-value [2]
	3.3. CoAP token length field		3.3. CoAP token length field
	This field is bi-directional.		This field is bi-directional.
	Several strategies can be applied to this field regarding the values:		Several strategies can be applied to this field regarding the values:
	o no token or a wellknown length, the transmission can be avoided.		o no token or a wellknown length, the transmission can be avoided.
	A special care must be taken, if CON messages are acknowledged		A special care must be taken, if CON messages are acknowledged
	with an empty ACK message. In that case the token is not always		with an empty ACK message. In that case the token is not always
	present.		present.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	TKL 1 bi value ignore send-value		TKL 4 1 bi value ignore send-value [4]
	o If the length is changing from one message to an other, the Token		o If the length is changing from one message to an other, the Token
	Length field must be sent. If the Token length can be limited,		Length field must be sent. If the Token length can be limited,
	then only the least significant bits have to be sent. The example		then only the least significant bits have to be sent. The example
	below allows values between 0 and 3.		below allows values between 0 and 3.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	TKL 1 bi 0x0 MSB(2) LSB(2)		TKL 4 1 bi 0x0 MSB(2) LSB(2) [2]
	o otherwise the field value has to be sent.		o otherwise the field value has to be sent.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	TKL 1 bi ignore value-sent		TKL 4 1 bi ignore value-sent [4]
	3.4. CoAP code field		3.4. CoAP code field
	This field is bidirectional, but compression can be enhanced using		This field is bidirectional, but compression can be enhanced using
	DI.		DI.
	The CoAP Code field defines a tricky way to ensure compatibility with		The CoAP Code field defines a tricky way to ensure compatibility with
	HTTP values. Nevertheless only 21 values are defined by [rfc7252]		HTTP values. Nevertheless only 21 values are defined by [rfc7252]
	compared to the 255 possible values.		compared to the 255 possible values.
	+------+------------------------------+-----------+		+------+------------------------------+-----------+
	| Code | Description | Mapping |		| Code | Description | Mapping |
	+------+------------------------------+-----------+		+------+------------------------------+-----------+
	| 0.00 | | 0x00 |		| 0.00 | | 0x00 |
	| 0.01 | GET | 0x01 |		| 0.01 | GET | 0x01 |
	| 0.02 | POST | 0x02 |		| 0.02 | POST | 0x02 |
	| 0.03 | PUT | 0x03 |		| 0.03 | PUT | 0x03 |
	| 0.04 | DELETE | 0x04 |		| 0.04 | DELETE | 0x04 |
	| 0.05 | FETCH | 0x05 |		| 0.05 | FETCH | 0x05 |
	| 0.06 | PATCH | 0x06 |		| 0.06 | PATCH | 0x06 |
	| 0.07 | iPATCH | 0x07 |		| 0.07 | iPATCH | 0x07 |
	| 2.01 | Created | 0x08 |		| 2.01 | Created | 0x08 |
	| 2.02 | Deleted | 0x09 |		| 2.02 | Deleted | 0x09 |
	| 2.03 | Valid | 0x0A |		| 2.03 | Valid | 0x0A |
	| 2.04 | Changed | 0x0B |		| 2.04 | Changed | 0x0B |
	| 2.05 | Content | 0x0C |		| 2.05 | Content | 0x0C |
	| 4.00 | Bad Request | 0x0D |		| 4.00 | Bad Request | 0x0D |
	| 4.01 | Unauthorized | 0x0E |		| 4.01 | Unauthorized | 0x0E |
	| 4.02 | Bad Option | 0x0F |		| 4.02 | Bad Option | 0x0F |
	| 4.03 | Forbidden | 0x10 |		| 4.03 | Forbidden | 0x10 |
	| 4.04 | Not Found | 0x11 |		| 4.04 | Not Found | 0x11 |
	| 4.05 | Method Not Allowed | 0x12 |		| 4.05 | Method Not Allowed | 0x12 |
	| 4.06 | Not Acceptable | 0x13 |		| 4.06 | Not Acceptable | 0x13 |
	| 4.12 | Precondition Failed | 0x14 |		| 4.12 | Precondition Failed | 0x14 |
	| 4.13 | Request Entity Too Large | 0x15 |		| 4.13 | Request Entity Too Large | 0x15 |
	| 4.15 | Unsupported Content-Format | 0x16 |		| 4.15 | Unsupported Content-Format | 0x16 |
	| 5.00 | Internal Server Error | 0x17 |		| 5.00 | Internal Server Error | 0x17 |
	| 5.01 | Not Implemented | 0x18 |		| 5.01 | Not Implemented | 0x18 |
	| 5.02 | Bad Gateway | 0x19 |		| 5.02 | Bad Gateway | 0x19 |
	| 5.03 | Service Unavailable | 0x1A |		| 5.03 | Service Unavailable | 0x1A |
	| 5.04 | Gateway Timeout | 0x1B |		| 5.04 | Gateway Timeout | 0x1B |
	| 5.05 | Proxying Not Supported | 0x1C |		| 5.05 | Proxying Not Supported | 0x1C |
	+------+------------------------------+-----------+		+------+------------------------------+-----------+
	Figure 1: Example of CoAP code mapping		Figure 1: Example of CoAP code mapping
	Figure 1 gives a possible mapping, it can be changed to add new codes		Figure 1 gives a possible mapping, it can be changed to add new codes
	or reduced if some values are never used by both ends. It could		or reduced if some values are never used by both ends. It could
	efficiently be coded on 5 bits.		efficiently be coded on 5 bits.
	Even if the number of code can be increase with other RFC,		Even if the number of code can be increase with other RFC,
	implementations may use a limited number of values, which can help to		implementations may use a limited number of values, which can help to
	reduce the number of bits sent on the LPWAN.		reduce the number of bits sent on the LPWAN.
	skipping to change at page 8, line 17 ¶		skipping to change at page 8, line 17 ¶
	The field can be treated differently in upstream than in downstream.		The field can be treated differently in upstream than in downstream.
	If the Thing is a client an entry can be set on the uplink message		If the Thing is a client an entry can be set on the uplink message
	with a code matching for 0.0X values and another for downlink values		with a code matching for 0.0X values and another for downlink values
	for Y.ZZ codes. It is the opposite if the thing is a server.		for Y.ZZ codes. It is the opposite if the thing is a server.
	If the ES always sends or receives requests with the same method, the		If the ES always sends or receives requests with the same method, the
	Code field can be elided. The entry below shows a rule for a client		Code field can be elided. The entry below shows a rule for a client
	sending only GET request.		sending only GET request.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	code 1 up GET equal not-sent		code 8 1 up GET equal not-sent
	If the client may send different methods, a matching-list can be		If the client may send different methods, a matching-list can be
	applied. For table Figure 1, 3 bits are necessary, but it could be		applied. For table Figure 1, 3 bits are necessary, but it could be
	less if fewer methods are used. Example below gives an example where		less if fewer methods are used. Example below gives an example where
	the ES is a server and receives only GET and POST requests.		the ES is a server and receives only GET and POST requests.
	FID Pos DI TV MO CDF		FID FL FP DI Target Value MO CDA Sent
	code 1 dw {0:0.01, 1:0.02}match-mapping mapping-sent		code 8 1 dw [0.01, 0.02] match-mapping mapping-sent [1]
	The same approach can be applied to responses.		The same approach can be applied to responses.
	3.5. CoAP Message ID field		3.5. CoAP Message ID field
	This field is bidirectional.		This field is bidirectional.
	Message ID is used for two purposes:		Message ID is used for two purposes:
	o To acknowledge a CON message with an ACK.		o To acknowledge a CON message with an ACK.
	o To avoid duplicate messages.		o To avoid duplicate messages.
	In LPWAN, since a message can be received by several radio gateway,		In LPWAN, since a message can be received by several radio gateway,
	some LPWAN technologies include a sequence number in L2 to avoid		some LPWAN technologies include a sequence number in L2 to avoid
	duplicate frames. Therefore if the message does not need to be		duplicate frames. Therefore if the message does not need to be
	acknowledged (NON or RST message), the Message ID field can be		acknowledged (NON or RST message), the Message ID field can be
	avoided.		avoided.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	Mid 1 bi ignore not-sent		Mid 8 1 bi ignore not-sent
	The decompressor must generate a value.		The decompressor must generate a value.
	[[Note; check id this field is not used by OSCOAP .]]		[[Note; check id this field is not used by OSCOAP .]]
	To optimize information sent on the LPWAN, shorter values may be used		To optimize information sent on the LPWAN, shorter values may be used
	during the exchange, but Message ID values generated a common CoAP		during the exchange, but Message ID values generated a common CoAP
	implementation will not take into account this limitation. Before		implementation will not take into account this limitation. Before
	the compression, a proxy may be needed to reduce the size.		the compression, a proxy may be needed to reduce the size.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	Mid 1 bi 0x0000 MSB(12) LSB(4)		Mid 8 1 bi 0x0000 MSB(12) LSB(4) [4]
	Otherwise if no compression is possible, the field has to be sent		Otherwise if no compression is possible, the field has to be sent
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	Mid 1 bi ignore value-sent		Mid 8 1 bi ignore value-sent [8]
	3.6. CoAP Token field		3.6. CoAP Token field
	This field is bi-directional.		This field is bi-directional.
	Token is used to identify transactions and varies from one		Token is used to identify transactions and varies from one
	transaction to another. Therefore, it is usually necessary to send		transaction to another. Therefore, it is usually necessary to send
	the value of the token field on the LPWAN network. The optimization		the value of the token field on the LPWAN network. The optimization
	will occur by using small values.		will occur by using small values.
	Common CoAP implementations may generate large tokens, even if		Common CoAP implementations may generate large tokens, even if
	shorter tokens could be used regarding the LPWAN characteristics. A		shorter tokens could be used regarding the LPWAN characteristics. A
	proxy may be needed to reduce the size of the token before		proxy may be needed to reduce the size of the token before
	compression.		compression.
	The size of the compress token sent is known by a combination of the		The size of the compress token sent is known by a combination of the
	Token Length field and the rule entry. For instance, with the entry		Token Length field and the rule entry. For instance, with the entry
	below:		below:
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	tkl 1 bi 2 equal not-sent		tkl 4 1 bi 2 equal not-sent
	token 1 bi 0x00 MSB(12) LSB(4)		token 8 1 bi 0x00 MSB(12) LSB(4) [4]
	The uncompressed token is 2 bytes long, but the compressed size will		The uncompressed token is 2 bytes long, but the compressed size will
	be 4 bits.		be 4 bits.
	4. CoAP options		4. CoAP options
	4.1. CoAP option Content-format field.		4.1. CoAP option Content-format field.
	This field is unidirectional and must not be set to bidirectional in		This field is unidirectional and must not be set to bidirectional in
	a rule entry. It is used only by the server to inform the client		a rule entry. It is used only by the server to inform the client
	about of the payload type and is never found in client requests.		about of the payload type and is never found in client requests.
	If single value is expected by the client, the TV contains that value		If single value is expected by the client, the TV contains that value
	and MO is set to "equal" and the CDF is set to "not-sent". The		and MO is set to "equal" and the CDF is set to "not-sent". The
	examples below describe the rules for an ES acting as a server.		examples below describe the rules for an ES acting as a server.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	content 1 up value equal not-sent		content 16 1 up value equal not-sent
	If several possible value are expected by the client, a matching-list		If several possible value are expected by the client, a matching-list
	can be used.		can be used.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	content 1 up {0:50,1:41} match-mapping mapping-sent		content 16 1 up [50, 41] match-mapping mapping-sent [1]
	Otherwise the value can be sent.The value-sent CDF in the compressor		Otherwise the value can be sent.The value-sent CDF in the compressor
	do not send the option type and the decompressor reconstruct it		do not send the option type and the decompressor reconstruct it
	regarding the position in the rule.		regarding the position in the rule.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	content 1 up ignore value-sent		content 16 1 up ignore value-sent [0-16]
	4.2. CoAP option Accept field		4.2. CoAP option Accept field
	This field is unidirectional and must not be set to bidirectional in		This field is unidirectional and must not be set to bidirectional in
	a rule entry. It is used only by the client to inform of the		a rule entry. It is used only by the client to inform of the
	possible payload type and is never found in server response.		possible payload type and is never found in server response.
	The number of accept options is not limited and can vary regarding		The number of accept options is not limited and can vary regarding
	the usage. To be selected a rule must contain the exact number about		the usage. To be selected a rule must contain the exact number about
	accept options with their positions. Since the order in which the		accept options with their positions. Since the order in which the
	Accept value are sent, the position order can be modified. The rule		Accept value are sent, the position order can be modified. The rule
	below		below
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	accept 1 up 41 egal not-sent		accept 16 1 up 41 egal not-sent
	accept 2 up 50 egal not-sent		accept 16 2 up 50 egal not-sent
	will be selected only if two accept options are in the CoAP header if		will be selected only if two accept options are in the CoAP header if
	this order.		this order.
	The rule below:		The rule below:
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	accept 0 up 41 egal not-sent		accept 16 0 up 41 egal not-sent
	accept 0 up 50 egal not-sent		accept 16 0 up 50 egal not-sent
	will accept a-only CoAP messages with 2 accept options, but the order		will accept a-only CoAP messages with 2 accept options, but the order
	will not influence the rule selection. The decompression will		will not influence the rule selection. The decompression will
	reconstruct the header regarding the rule order.		reconstruct the header regarding the rule order.
	Otherwise a matching-list can be applied to the different values, in		Otherwise a matching-list can be applied to the different values, in
	that case the order is important to recover the appropriate value and		that case the order is important to recover the appropriate value and
	the position must be clearly indicate.		the position must be clearly indicate.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	accept 1 up {0:50,1:41} match-mapping mapping-sent		accept 16 1 up [50,41] match-mapping mapping-sent [1]
	accept 2 up {0:50,1:61} match-mapping mapping-sent		accept 16 2 up [50,61] match-mapping mapping-sent [1]
	accept 3 up {0:61,1:71} match-mapping mapping-sent		accept 16 3 up [61,71] match-mapping mapping-sent [1]
	Finally, the option can be explicitly sent.		Finally, the option can be explicitly sent.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	accept 1 up ignore value-sent		accept 1 up ignore value-sent
	4.3. CoAP option Max-Age field, CoAP option Uri-Host and Uri-Port		4.3. CoAP option Max-Age field, CoAP option Uri-Host and Uri-Port
	fields		fields
	This field is unidirectional and must not be set to bidirectional in		This field is unidirectional and must not be set to bidirectional in
	a rule entry. It is used only by the server to inform of the caching		a rule entry. It is used only by the server to inform of the caching
	duration and is never found in client requests.		duration and is never found in client requests.
	If the duration is known by both ends, value can be elided on the		If the duration is known by both ends, value can be elided on the
	LPWAN.		LPWAN.
	skipping to change at page 11, line 45 ¶		skipping to change at page 11, line 45 ¶
	5. CoAP option Uri-Path and Uri-Query fields		5. CoAP option Uri-Path and Uri-Query fields
	This fields are unidirectional and must not be set to bidirectional		This fields are unidirectional and must not be set to bidirectional
	in a rule entry. They are used only by the client to access to a		in a rule entry. They are used only by the client to access to a
	specific resource and are never found in server response.		specific resource and are never found in server response.
	The Matching Operator behavior has not changed, but the value must		The Matching Operator behavior has not changed, but the value must
	take a position value, if the entry is repeated :		take a position value, if the entry is repeated :
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	URI-Path 1 up foo equal not-sent		URI-Path 1 up foo equal not-sent
	URI-Path 2 up bar equal not-sent		URI-Path 2 up bar equal not-sent
	Figure 2: Position entry.		Figure 2: Position entry.
	For instance, the rule Figure 2 matches with /foo/bar, but not /bar/		For instance, the rule Figure 2 matches with /foo/bar, but not /bar/
	foo.		foo.
	When the length is not clearly indicated in the rule, the value		When the length is not clearly indicated in the rule, the value
	length must be sent with the field data, which means for CoAP to send		length must be sent with the field data, which means for CoAP to send
	directly the CoAP option with length and value.		directly the CoAP option with length and value.
	For instance for a CoMi path /c/X6?k="eth0" the rule can be set to:		For instance for a CoMi path /c/X6?k="eth0" the rule can be set to:
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	URI-Path 1 up c equal not-sent		URI-Path 1 up c equal not-sent
	URI-Path 2 up ignore value-sent		URI-Path 2 up ignore value-sent
	URI-Query 1 up k= MSB (16) LSB		URI-Query 1 up k= MSB (16) LSB
	Figure 3: CoMi URI compression		Figure 3: CoMi URI compression
	Figure 3 shows the parsing and the compression of the URI. where c is		Figure 3 shows the parsing and the compression of the URI. where c is
	not sent. The second element is sent with the length (i.e. 0x2 X 6)		not sent. The second element is sent with the length (i.e. 0x2 X 6)
	followed by the query option (i.e. 0x05 "eth0").		followed by the query option (i.e. 0x05 "eth0").
	A Mapping list can be used to reduce size of variable Paths or		A Mapping list can be used to reduce size of variable Paths or
	Queries. In that case, to optimize the compression, several elements		Queries. In that case, to optimize the compression, several elements
	can be regrouped into a single entry. Numbering of elements do not		can be regrouped into a single entry. Numbering of elements do not
	change, MO comparison is set with the first element of the matching.		change, MO comparison is set with the first element of the matching.
	FID Pos DI TV MO CDF		FID FL FP DI TV MO CDA Sent
	URI-Path 1 up {0:"/c/c", equal not-sent		URI-Path 1 up {0:"/c/c", equal not-sent
	1:"/c/d"		1:"/c/d"
	URI-Path 3 up ignore value-sent		URI-Path 3 up ignore value-sent
	URI-Query 1 up k= MSB (16) LSB		URI-Query 1 up k= MSB (16) LSB
	Figure 4: complex path example		Figure 4: complex path example
	For instance, the following Path /foo/bar/variable/stable can leads		For instance, the following Path /foo/bar/variable/stable can leads
	to the rule defined Figure 4.		to the rule defined Figure 4.
	5.1. CoAP option Proxy-URI and Proxy-Scheme fields		5.1. CoAP option Proxy-URI and Proxy-Scheme fields
	These fields are unidirectional and must not be set to bidirectional		These fields are unidirectional and must not be set to bidirectional
	in a rule entry. They are used only by the client to access to a		in a rule entry. They are used only by the client to access to a
	skipping to change at page 14, line 12 ¶		skipping to change at page 14, line 12 ¶
	7. Protocol analysis		7. Protocol analysis
	8. Examples of CoAP header compression		8. Examples of CoAP header compression
	8.1. Mandatory header with CON message		8.1. Mandatory header with CON message
	In this first scenario, the LPWAN compressor receives from outside		In this first scenario, the LPWAN compressor receives from outside
	client a POST message, which is immediately acknowledged by the		client a POST message, which is immediately acknowledged by the
	Thing. For this simple scenario, the rules are described Figure 5.		Thing. For this simple scenario, the rules are described Figure 5.
	rule id 1		Rule ID 1
	+-------------+------+---------+-------------+-----+----------------+		+-------------+--+--+--+------+---------+-------------++------------+
	| Field |TV |MO |CDF |dir | Sent |		| Field |FL|FP|DI|Target| Match | CDA || Sent |
	+=============+======+=========+=============+=====+================+		| | | | |Value | Opera. | || [bits] |
	|CoAP version | 01 |equal |not-sent |bi | |		+-------------+--+--+--+------+---------+-------------++------------+
	|CoAP Type | |ignore |value-sent |bi |TT |		|CoAP version | | |bi| 01 |equal |not-sent || |
	|CoAP TKL | 0 |equal |not-sent |bi | |		|CoAP version | | |bi| 01 |equal |not-sent || |
	|CoAP Code | ML1 |match-map|matching-sent|bi | CC CCC |		|CoAP Type | | |bi| |ignore |value-sent ||TT |
	|CoAP MID | 0000 |MSB(7 ) |LSB(9) |bi | M-ID |		|CoAP TKL | | |bi| 0 |equal |not-sent || |
	|CoAP Uri-Path| path |equal 1 |not-sent |down | |		|CoAP Code | | |bi| ML1 |match-map|matching-sent|| CC CCC |
	+-------------+------+---------+-------------+-----+----------------+		|CoAP MID | | |bi| 0000 |MSB(7 ) |LSB(9) || M-ID|
			|CoAP Uri-Path| | |dw| path |equal 1 |not-sent || |
			+-------------+--+--+--+------+---------+-------------++------------+
	Figure 5: CoAP Context to compress header without token		Figure 5: CoAP Context to compress header without token
	The version and Token Length fields are elided. Code has shrunk to 5		The version and Token Length fields are elided. Code has shrunk to 5
	bits using the matching list (as the one given Figure 1: 0.01 is		bits using the matching list (as the one given Figure 1: 0.01 is
	value 0x01 and 2.05 is value 0x0c) Message-ID has shrunk to 9 bits to		value 0x01 and 2.05 is value 0x0c) Message-ID has shrunk to 9 bits to
	preserve alignment on byte boundary. The most significant bit must		preserve alignment on byte boundary. The most significant bit must
	be set to 0 through a CoAP proxy. Uri-Path contains a single element		be set to 0 through a CoAP proxy. Uri-Path contains a single element
	indicated in the matching operator.		indicated in the matching operator.
	skipping to change at page 15, line 5 ¶		skipping to change at page 15, line 5 ¶
	only the Type, a mapped code and the least 9 significant bits of		only the Type, a mapped code and the least 9 significant bits of
	Message ID. The receiver decompresses the header. .		Message ID. The receiver decompresses the header. .
	The CON message is a request, therefore the LC process to a dynamic		The CON message is a request, therefore the LC process to a dynamic
	mapping. When the ES receives the ACK message, this will not		mapping. When the ES receives the ACK message, this will not
	initiate locally a message ID mapping since it is a response. The LC		initiate locally a message ID mapping since it is a response. The LC
	receives the ACK and uncompressed it to restore the original value.		receives the ACK and uncompressed it to restore the original value.
	Dynamic Mapping context lifetime follows the same rules as message ID		Dynamic Mapping context lifetime follows the same rules as message ID
	duration.		duration.
	End System LPWA LC		End System LPWA LC
	| |		| |
	| rule id=1 |<----------------------		| rule id=1 |<--------------------
	|<--------------------| +-+-+--+----+--------+		|<-------------------| +-+-+--+----+------+
	<-------------------- | TTCC CCCM MMMM MMMM| |1|0| 4|0.01| 0x0034 |		<------------------- | TTCC CCCM MMMM MMMM| |1|0| 4|0.01|0x0034|
	+-+-+--+----+--------+ | 0000 0010 0011 0100| | 0xb4 p a t |		+-+-+--+----+-------+ | 0000 0010 0011 0100| | 0xb4 p a t|
	|1|0| 1|0.01| 0x0034 | | | | h |		|1|0| 1|0.01|0x0034 | | | | h |
	| 0xb4 p a t | | | +------+		| 0xb4 p a t | | | +------+
	| h | | |		| h | | |
	+------+ | |		+------+ | |
	| |		| |
	| |		| |
	+-+-+--+----+--------+ |-------------------->|		---------------------->| rule id=1 |
	|1|2| 0|2.05| 0x0034 | | TTCC CCCM MMMM MMMM|------------------------>		+-+-+--+----+--------+ |------------------->|
	+-+-+--+----+--------+ | 1001 1000 0011 0100| +-+-+--+----+--------+		|1|2| 0|2.05| 0x0034 | | TTCC CCCM MMMM MMMM|--------------------->
	| | |1|2| 0|2.05| 0x0034 |		+-+-+--+----+--------+ | 1001 1000 0011 0100| +-+-+--+----+------+
	v v +-+-+--+----+--------+		| | |1|2| 0|2.05|0x0034|
			v v +-+-+--+----+------+
	Figure 6: Compression with global addresses		Figure 6: Compression with global addresses
	The message can be further optimized by setting some fields		The message can be further optimized by setting some fields
	unidirectional, as described in Figure 7. Note that Type is no more		unidirectional, as described in Figure 7. Note that Type is no more
	sent in the compressed format, Compressed Code size in not changed in		sent in the compressed format, Compressed Code size in not changed in
	that example (8 values are needed to code all the requests and 21 to		that example (8 values are needed to code all the requests and 21 to
	code all the responses in the matching list Figure 1)		code all the responses in the matching list Figure 1)
	rule id 1		Rule ID 2
	+-------------+------+---------+-------------+---+----------------+		+-------------+--+--+--+------+---------+------------++------------+
	| Field |TV |MO |CDF |dir| Sent |		| Field |FL|FP|DI|Target| MO | CDA || Sent |
	+=============+======+=========+=============+===+================+		| | | | |Value | | || [bits] |
	|CoAP version | 01 |equal |not-sent |bi | |		+-------------+--+--+--+------+---------+------------++------------+
	|CoAP Type | CON |equal |not-sent |dw | |		|CoAP version | | |bi|01 |equal |not-sent || |
	|CoAP Type | ACK |equal |not-sent |up | |		|CoAP Type | | |dw|CON |equal |not-sent || |
	|CoAP TKL | 0 |equal |not-sent |bi | |		|CoAP Type | | |up| ACK |equal |not-sent || |
	|CoAP Code | ML2 |match-map|mapping-sent |dw |CCCC C |		|CoAP TKL | | |bi|0 |equal |not-sent || |
	|CoAP Code | ML3 |match-map|mapping-sent |up |CCCC C |		|CoAP Code | | |dw|ML2 |match-map|mapping-sent||CCCC C |
	|CoAP MID | 0000 |MSB(5) |LSB(11) |bi | M-ID |		|CoAP Code | | |up|ML3 |match-map|mapping-sent||CCCC C |
	|CoAP Uri-Path| path |equal 1 |not-sent |dw | |		|CoAP MID | | |bi|0000 |MSB(5) |LSB(11) || M-ID |
	+-------------+------+---------+-------------+---+----------------+		|CoAP Uri-Path| | |dw|path |equal 1 |not-sent || |
			+-------------+--+--+--+------+---------+------------++------------+
	ML1 = {CON : 0, ACK:1} ML2 = {POST:0, 2.04:1, 0.00:3}		ML1 = {CON : 0, ACK:1} ML2 = {POST:0, 2.04:1, 0.00:3}
	Figure 7: CoAP Context to compress header without token		Figure 7: CoAP Context to compress header without token
	8.2. Complete exchange		8.2. Complete exchange
	In that example, the Thing is using CoMi and sends queries for 2 SID.		In that example, the Thing is using CoMi and sends queries for 2 SID.
	CON		CON
	skipping to change at page 16, line 26 ¶		skipping to change at page 16, line 26 ¶
	|<------------------------| ACK MID=0x0012		|<------------------------| ACK MID=0x0012
	| | 0.00		| | 0.00
	| |		| |
	| |		| |
	|<------------------------| CON		|<------------------------| CON
	| | MID=0X0034		| | MID=0X0034
	| | Content-Format X		| | Content-Format X
	ACK MID=0x0034 |------------------------>|		ACK MID=0x0034 |------------------------>|
	0.00		0.00
	rule id 3		Rule ID 3
	+-------------+------+---------+-------------+---+----------------+		+--------------+--+--+--+------+--------+-----------++------------+
	| Field |TV |MO |CDF |dir| Sent |		| Field |FL|FP|DI|Target| MO | CDA || Sent |
	+=============+======+=========+=============+===+================+		| | | | |Value | | || [bits] |
	|CoAP version | 01 |equal |not-sent |bi | |		+--------------+--+--+--+------+--------+-----------++------------+
	|CoAP Type | CON |equal |not-sent |up | |		|CoAP version | | |bi| 01 |equal |not-sent || |
	|CoAP Type | ACK |equal |not-sent |dw | |		|CoAP Type | | |up| CON |equal |not-sent || |
	|CoAP TKL | 1 |equal |not-sent |bi | |		|CoAP Type | | |dw| ACK |equal |not-sent || |
	|CoAP Code | POST |equal |not-sent |up | |		|CoAP TKL | | |bi| 1 |equal |not-sent || |
	|CoAP Code | 0.00 |equal |not-sent |dw | |		|CoAP Code | | |up| POST |equal |not-sent || |
	|CoAP MID | 0000 |MSB(8) |LSB |bi |MMMMMMMM |		|CoAP Code | | |dw| 0.00 |equal |not-sent || |
	|CoAP Token | |ignore |send-value |up |TTTTTTTT |		|CoAP MID | | |bi| 0000 |MSB(8) |LSB ||MMMMMMMM |
	|CoAP Uri-Path| /c |equal 1 |not-sent |dw | |		|CoAP Token | | |up| |ignore |send-value ||TTTTTTTT |
	|CoAP Uri-query ML4 |equal 1 |not-sent |dw |P |		|CoAP Uri-Path | | |dw| /c |equal 1 |not-sent || |
	|CoAP Content | X |equal |not-sent |up | |		|CoAP Uri-query| | |dw| ML4 |equal 1 |not-sent ||P |
	+-------------+------+---------+-------------+---+----------------+		|CoAP Content | | |up| X |equal |not-sent || |
			+--------------+--+--+--+------+--------+-----------++------------+
	rule id 4		Rule ID 4
	+-------------+------+---------+-------------+---+----------------+		+--------------+--+--+--+------+--------+-----------++------------+
	| Field |TV |MO |CDF |dir| Sent |		| Field |FL|FP|DI|Target| MO | CDA || Sent |
	+=============+======+=========+=============+===+================+		| | | | |Value | | || [bits] |
	|CoAP version | 01 |equal |not-sent |bi | |		+--------------+--+--+--+------+--------+-----------++------------+
	|CoAP Type | CON |equal |not-sent |dw | |		|CoAP version | | |bi| 01 |equal |not-sent || |
	|CoAP Type | ACK |equal |not-sent |up | |		|CoAP Type | | |dw| CON |equal |not-sent || |
	|CoAP TKL | 1 |equal |not-sent |bi | |		|CoAP Type | | |up| ACK |equal |not-sent || |
	|CoAP Code | 2.05 |equal |not-sent |dw | |		|CoAP TKL | | |bi| 1 |equal |not-sent || |
	|CoAP Code | 0.00 |equal |not-sent |up | |		|CoAP Code | | |dw| 2.05 |equal |not-sent || |
	|CoAP MID | 0000 |MSB(8) |LSB |bi |MMMMMMMM |		|CoAP Code | | |up| 0.00 |equal |not-sent || |
	|CoAP Token | |ignore |send-value |dw |TTTTTTTT |		|CoAP MID | | |bi| 0000 |MSB(8) |LSB ||MMMMMMMM |
	|COAP Accept | X |equal |not-sent |dw | |		|CoAP Token | | |dw| |ignore |send-value||TTTTTTTT |
	+-------------+------+---------+-------------+---+----------------+		|COAP Accept | | |dw| X |equal |not-sent || |
			+--------------+--+--+--+------+---------+----------++------------+
	alternative rule:		alternative rule:
	rule id 4		Rule ID 4
	+-------------+------+---------+-------------+---+----------------+		+--------------+--+--+--+------+---------+-----------++------------+
	| Field |TV |MO |CDF |dir| Sent |		| Field |FL|FP|DI|Target| MO | CDA || Sent |
	+=============+======+=========+=============+===+================+		| | | | |Value | | || [bits] |
	|CoAP version | 01 |equal |not-sent |bi | |		+--------------+--+--+--+------+---------+-----------++------------+
	|CoAP Type | ML1 |match-map|match-sent |bi |t |		|CoAP version | | |bi| 01 |equal |not-sent || |
	|CoAP TKL | 1 |equal |not-sent |bi | |		|CoAP Type | | |bi| ML1 |match-map|match-sent ||t |
	|CoAP Code | ML2 |match-map|match-sent |up | cc |		|CoAP TKL | | |bi| 1 |equal |not-sent || |
	|CoAP Code | ML3 |match-map|match-sent |dw | cc |		|CoAP Code | | |up| ML2 |match-map|match-sent || cc |
	|CoAP MID | 0000 |MSB(8) |LSB |bi |MMMMMMMM |		|CoAP Code | | |dw| ML3 |match-map|match-sent || cc |
	|CoAP Token | |ignore |send-value |dw |TTTTTTTT |		|CoAP MID | | |bi| 0000 |MSB(8) |LSB ||MMMMMMMM |
	|CoAP Uri-Path| /c |equal 1 |not-sent |dw | |		|CoAP Token | | |dw| |ignore |send-value ||TTTTTTTT |
	|CoAP Uri-query ML4 |equal 1 |not-sent |dw |P |		|CoAP Uri-Path | | |dw| /c |equal 1 |not-sent || |
	|CoAP Content | X |equal |not-sent |up | |		|CoAP Uri-query| | |dw| ML4 |equal 1 |not-sent ||P |
	|COAP Accept | x |equal |not-sent |dw | |		|CoAP Content | | |up| X |equal |not-sent || |
	+-------------+------+---------+-------------+---+----------------+		|COAP Accept | | |dw| x |equal |not-sent || |
			+--------------+--+--+--+------+---------+-----------++------------+
	ML1 {CON:0, ACK:1} ML2 {POST:0, 0.00: 1} ML3 {2.05:0, 0.00:1}		ML1 {CON:0, ACK:1} ML2 {POST:0, 0.00: 1} ML3 {2.05:0, 0.00:1}
	ML4 {NULL:0, k=AS:1, K=AZE:2}		ML4 {NULL:0, k=AS:1, K=AZE:2}
	9. Normative References		9. Normative References
	[I-D.toutain-lpwan-ipv6-static-context-hc]		[I-D.toutain-lpwan-ipv6-static-context-hc]
	Minaburo, A. and L. Toutain, "LPWAN Static Context Header		Minaburo, A. and L. Toutain, "LPWAN Static Context Header
	Compression (SCHC) for IPv6 and UDP", draft-toutain-lpwan-		Compression (SCHC) for IPv6 and UDP", draft-toutain-lpwan-
	ipv6-static-context-hc-00 (work in progress), September		ipv6-static-context-hc-00 (work in progress), September
	skipping to change at page 18, line 21 ¶		skipping to change at page 18, line 26 ¶
	Ana Minaburo		Ana Minaburo
	Acklio		Acklio
	2bis rue de la Chataigneraie		2bis rue de la Chataigneraie
	35510 Cesson-Sevigne Cedex		35510 Cesson-Sevigne Cedex
	France		France
	Email: ana@ackl.io		Email: ana@ackl.io
	Laurent Toutain		Laurent Toutain
	Institut MINES TELECOM ; IMT Atlantique		Institut MINES TELECOM; IMT Atlantique
	2 rue de la Chataigneraie		2 rue de la Chataigneraie
	CS 17607		CS 17607
	35576 Cesson-Sevigne Cedex		35576 Cesson-Sevigne Cedex
	France		France
	Email: Laurent.Toutain@imt-atlantique.fr		Email: Laurent.Toutain@imt-atlantique.fr
End of changes. 45 change blocks.
	216 lines changed or deleted		222 lines changed or added
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