< draft-ietf-lpwan-coap-static-context-hc-10.txt		draft-ietf-lpwan-coap-static-context-hc-11.txt >
	lpwan Working Group A. Minaburo		lpwan Working Group A. Minaburo
	Internet-Draft Acklio		Internet-Draft Acklio
	Intended status: Standards Track L. Toutain		Intended status: Standards Track L. Toutain
	Expires: April 10, 2020 Institut MINES TELECOM; IMT Atlantique		Expires: April 11, 2020 Institut MINES TELECOM; IMT Atlantique
	R. Andreasen		R. Andreasen
	Universidad de Buenos Aires		Universidad de Buenos Aires
	October 08, 2019		October 09, 2019
	LPWAN Static Context Header Compression (SCHC) for CoAP		LPWAN Static Context Header Compression (SCHC) for CoAP
	draft-ietf-lpwan-coap-static-context-hc-10		draft-ietf-lpwan-coap-static-context-hc-11
	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. The CoAP header structure differs from IPv6 and UDP		CoAP headers. The CoAP header structure differs from IPv6 and UDP
	protocols since CoAP uses a flexible header with a variable number of		protocols since CoAP uses a flexible header with a variable number of
	options, themselves of variable length. The CoAP protocol messages		options, themselves of variable length. The CoAP protocol messages
	format is asymmetric: the request messages have a header format		format is asymmetric: the request messages have a header format
	different from the one in the response messages. This document		different from the one in the response messages. This document
	explains how to use the SCHC compression mechanism described in		explains how to use the SCHC compression mechanism for CoAP.
	[I-D.ietf-lpwan-ipv6-static-context-hc] for CoAP.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on April 10, 2020.		This Internet-Draft will expire on April 11, 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
	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
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
			1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
	2. SCHC Compression Process . . . . . . . . . . . . . . . . . . 3		2. SCHC Compression Process . . . . . . . . . . . . . . . . . . 3
	3. CoAP Compression with SCHC . . . . . . . . . . . . . . . . . 4		3. CoAP Compression with SCHC . . . . . . . . . . . . . . . . . 4
	4. Compression of CoAP header fields . . . . . . . . . . . . . . 6		4. Compression of CoAP header fields . . . . . . . . . . . . . . 6
	4.1. CoAP version field . . . . . . . . . . . . . . . . . . . 6		4.1. CoAP version field . . . . . . . . . . . . . . . . . . . 6
	4.2. CoAP type field . . . . . . . . . . . . . . . . . . . . . 6		4.2. CoAP type field . . . . . . . . . . . . . . . . . . . . . 6
	4.3. CoAP code field . . . . . . . . . . . . . . . . . . . . . 6		4.3. CoAP code field . . . . . . . . . . . . . . . . . . . . . 6
	4.4. CoAP Message ID field . . . . . . . . . . . . . . . . . . 6		4.4. CoAP Message ID field . . . . . . . . . . . . . . . . . . 6
	4.5. CoAP Token fields . . . . . . . . . . . . . . . . . . . . 7		4.5. CoAP Token fields . . . . . . . . . . . . . . . . . . . . 7
	5. CoAP options . . . . . . . . . . . . . . . . . . . . . . . . 7		5. CoAP options . . . . . . . . . . . . . . . . . . . . . . . . 7
	5.1. CoAP Content and Accept options. . . . . . . . . . . . . 7		5.1. CoAP Content and Accept options. . . . . . . . . . . . . 7
	5.2. CoAP option Max-Age, Uri-Host and Uri-Port fields . . . . 8		5.2. CoAP option Max-Age, Uri-Host and Uri-Port fields . . . . 8
	5.3. CoAP option Uri-Path and Uri-Query fields . . . . . . . . 8		5.3. CoAP option Uri-Path and Uri-Query fields . . . . . . . . 8
	5.3.1. Variable length Uri-Path and Uri-Query . . . . . . . 8		5.3.1. Variable length Uri-Path and Uri-Query . . . . . . . 9
	5.3.2. Variable number of path or query elements . . . . . . 9		5.3.2. Variable number of path or query elements . . . . . . 9
	5.4. CoAP option Size1, Size2, Proxy-URI and Proxy-Scheme		5.4. CoAP option Size1, Size2, Proxy-URI and Proxy-Scheme
	fields . . . . . . . . . . . . . . . . . . . . . . . . . 9		fields . . . . . . . . . . . . . . . . . . . . . . . . . 9
	5.5. CoAP option ETag, If-Match, If-None-Match, Location-Path		5.5. CoAP option ETag, If-Match, If-None-Match, Location-Path
	and Location-Query fields . . . . . . . . . . . . . . . . 9		and Location-Query fields . . . . . . . . . . . . . . . . 10
	6. Other RFCs . . . . . . . . . . . . . . . . . . . . . . . . . 10		6. Other RFCs . . . . . . . . . . . . . . . . . . . . . . . . . 10
	6.1. Block . . . . . . . . . . . . . . . . . . . . . . . . . . 10		6.1. Block . . . . . . . . . . . . . . . . . . . . . . . . . . 10
	6.2. Observe . . . . . . . . . . . . . . . . . . . . . . . . . 10		6.2. Observe . . . . . . . . . . . . . . . . . . . . . . . . . 10
	6.3. No-Response . . . . . . . . . . . . . . . . . . . . . . . 10		6.3. No-Response . . . . . . . . . . . . . . . . . . . . . . . 10
	6.4. OSCORE . . . . . . . . . . . . . . . . . . . . . . . . . 10		6.4. OSCORE . . . . . . . . . . . . . . . . . . . . . . . . . 10
	7. Examples of CoAP header compression . . . . . . . . . . . . . 12		7. Examples of CoAP header compression . . . . . . . . . . . . . 12
	7.1. Mandatory header with CON message . . . . . . . . . . . . 12		7.1. Mandatory header with CON message . . . . . . . . . . . . 12
	7.2. OSCORE Compression . . . . . . . . . . . . . . . . . . . 13		7.2. OSCORE Compression . . . . . . . . . . . . . . . . . . . 13
	7.3. Example OSCORE Compression . . . . . . . . . . . . . . . 16		7.3. Example OSCORE Compression . . . . . . . . . . . . . . . 16
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
	skipping to change at page 3, line 37 ¶		skipping to change at page 3, line 37 ¶
	compression there may be some bits to be sent, these values are		compression there may be some bits to be sent, these values are
	called Compression Residues and are transmitted after the Rule ID in		called Compression Residues and are transmitted after the Rule ID in
	the compressed messages.		the compressed messages.
	The compression rules define a generic way to compress and decompress		The compression rules define a generic way to compress and decompress
	the fields. If the device is modified, for example, to introduce new		the fields. If the device is modified, for example, to introduce new
	functionalities or new CoAP options, the rules must be updated to		functionalities or new CoAP options, the rules must be updated to
	reflect the evolution. There is no risk to lock a device in a		reflect the evolution. There is no risk to lock a device in a
	particular version of CoAP.		particular version of CoAP.
			1.1. Terminology
			The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
			"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
			"OPTIONAL" in this document are to be interpreted as described in BCP
			14 [rfc2119][rfc8174] when, and only when, they appear in all
			capitals, as shown here.
	2. SCHC Compression Process		2. SCHC Compression Process
	The SCHC Compression rules can be applied to CoAP flows. SCHC		The SCHC Compression rules can be applied to CoAP flows. SCHC
	Compression of the CoAP header MAY be done in conjunction with the		Compression of the CoAP header MAY be done in conjunction with the
	lower layers (IPv6/UDP) or independently. The SCHC adaptation layers		lower layers (IPv6/UDP) or independently. The SCHC adaptation layers
	as described in [I-D.ietf-lpwan-ipv6-static-context-hc] may be used		as described in [I-D.ietf-lpwan-ipv6-static-context-hc] may be used
	as shown in Figure 1.		as shown in Figure 1.
	^ +------------+ ^ +------------+ ^ +------------+		^ +------------+ ^ +------------+ ^ +------------+
	| | CoAP | | | CoAP | inner | | CoAP |		| | CoAP | | | CoAP | inner | | CoAP |
	skipping to change at page 8, line 33 ¶		skipping to change at page 8, line 33 ¶
	specific resource and are never found in server responses.		specific resource and are never found in server responses.
	Uri-Path and Uri-Query elements are a repeatable options, the Field		Uri-Path and Uri-Query elements are a repeatable options, the Field
	Position (FP) gives the position in the path.		Position (FP) gives the position in the path.
	A Mapping list can be used to reduce the size of variable Paths or		A Mapping list can be used to reduce the 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 FL FP DI TV MO CDA		+-------------+--+--+--+--------+---------+-------------+
	URI-Path 1 up ["/a/b", equal not-sent		| Field |FL|FP|DI| Target | Match | CDA |
	"/c/d"]		| | | | | Value | Opera. | |
	URI-Path 3 up ignore value-sent		+-------------+--+--+--+--------+---------+-------------+
			|URI-Path | | 1|up|["/a/b",|equal |not-sent |
			| | | | |"/c/d"] | | |
			|URI-Path | | 3|up| |ignore |value-sent |
			+-------------+--+--+--+--------+---------+-------------+
	Figure 2: complex path example		Figure 2: complex path example
	In Figure 2 a single bit residue can be used to code one of the 2		In Figure 2 a single bit residue can be used to code one of the 2
	paths. If regrouping were not allowed, a 2 bits residue would be		paths. If regrouping were not allowed, a 2 bits residue would be
	needed.		needed.
	5.3.1. Variable length Uri-Path and Uri-Query		5.3.1. Variable length Uri-Path and Uri-Query
	When the length is not known at the rule creation, the Field Length		When the length is not known at the rule creation, the Field Length
	skipping to change at page 9, line 11 ¶		skipping to change at page 9, line 20 ¶
	The MSB MO can be applied to a Uri-Path or Uri-Query element. Since		The MSB MO can be applied to a Uri-Path or Uri-Query element. Since
	MSB value is given in bit, the size MUST always be a multiple of 8		MSB value is given in bit, the size MUST always be a multiple of 8
	bits.		bits.
	The length sent at the beginning of a variable length residue		The length sent at the beginning of a variable length residue
	indicates the size of the LSB in bytes.		indicates the size of the LSB in bytes.
	For instance for a CORECONF path /c/X6?k="eth0" the rule can be set		For instance for a CORECONF path /c/X6?k="eth0" the rule can be set
	to:		to:
	FID FL FP DI TV MO CDA		+-------------+---+--+--+--------+---------+-------------+
	URI-Path 1 up "c" equal not-sent		| Field |FL |FP|DI| Target | Match | CDA |
	URI-Path 2 up ignore value-sent		| | | | | Value | Opera. | |
	URI-Query 1 up "k=" MSB (16) LSB		+-------------+---+--+--+--------+---------+-------------+
			|URI-Path | 8| 1|up|"c" |equal |not-sent |
			|URI-Path |var| 2|up| |ignore |value-sent |
			|URI-Query |var| 1|up|"k=" |MSB(16) |LSB |
			+-------------+---+--+--+--------+---------+-------------+
	Figure 3: CORECONF URI compression		Figure 3: CORECONF 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").
	5.3.2. Variable number of path or query elements		5.3.2. Variable number of path or query elements
	The number of Uri-path or Uri-Query elements in a rule is fixed at		The number of Uri-path or Uri-Query elements in a rule is fixed at
	skipping to change at page 26, line 47 ¶		skipping to change at page 26, line 47 ¶
	11. Normative References		11. Normative References
	[I-D.ietf-lpwan-ipv6-static-context-hc]		[I-D.ietf-lpwan-ipv6-static-context-hc]
	Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and J.		Minaburo, A., Toutain, L., Gomez, C., Barthel, D., and J.
	Zuniga, "Static Context Header Compression (SCHC) and		Zuniga, "Static Context Header Compression (SCHC) and
	fragmentation for LPWAN, application to UDP/IPv6", draft-		fragmentation for LPWAN, application to UDP/IPv6", draft-
	ietf-lpwan-ipv6-static-context-hc-21 (work in progress),		ietf-lpwan-ipv6-static-context-hc-21 (work in progress),
	July 2019.		July 2019.
			[rfc2119] Bradner, S., "Key words for use in RFCs to Indicate
			Requirement Levels", BCP 14, RFC 2119,
			DOI 10.17487/RFC2119, March 1997,
			<https://www.rfc-editor.org/info/rfc2119>.
	[rfc7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained		[rfc7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
	Application Protocol (CoAP)", RFC 7252,		Application Protocol (CoAP)", RFC 7252,
	DOI 10.17487/RFC7252, June 2014,		DOI 10.17487/RFC7252, June 2014,
	<https://www.rfc-editor.org/info/rfc7252>.		<https://www.rfc-editor.org/info/rfc7252>.
	[rfc7641] Hartke, K., "Observing Resources in the Constrained		[rfc7641] Hartke, K., "Observing Resources in the Constrained
	Application Protocol (CoAP)", RFC 7641,		Application Protocol (CoAP)", RFC 7641,
	DOI 10.17487/RFC7641, September 2015,		DOI 10.17487/RFC7641, September 2015,
	<https://www.rfc-editor.org/info/rfc7641>.		<https://www.rfc-editor.org/info/rfc7641>.
	[rfc7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in		[rfc7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
	the Constrained Application Protocol (CoAP)", RFC 7959,		the Constrained Application Protocol (CoAP)", RFC 7959,
	DOI 10.17487/RFC7959, August 2016,		DOI 10.17487/RFC7959, August 2016,
	<https://www.rfc-editor.org/info/rfc7959>.		<https://www.rfc-editor.org/info/rfc7959>.
	[rfc7967] Bhattacharyya, A., Bandyopadhyay, S., Pal, A., and T.		[rfc7967] Bhattacharyya, A., Bandyopadhyay, S., Pal, A., and T.
	Bose, "Constrained Application Protocol (CoAP) Option for		Bose, "Constrained Application Protocol (CoAP) Option for
	No Server Response", RFC 7967, DOI 10.17487/RFC7967,		No Server Response", RFC 7967, DOI 10.17487/RFC7967,
	August 2016, <https://www.rfc-editor.org/info/rfc7967>.		August 2016, <https://www.rfc-editor.org/info/rfc7967>.
			[rfc8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
			2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
			May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[rfc8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz,		[rfc8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
	"Object Security for Constrained RESTful Environments		"Object Security for Constrained RESTful Environments
	(OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,		(OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,
	<https://www.rfc-editor.org/info/rfc8613>.		<https://www.rfc-editor.org/info/rfc8613>.
	Authors' Addresses		Authors' Addresses
	Ana Minaburo		Ana Minaburo
	Acklio		Acklio
	1137A avenue des Champs Blancs		1137A avenue des Champs Blancs
End of changes. 13 change blocks.
	16 lines changed or deleted		41 lines changed or added
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