< draft-ietf-lpwan-coap-static-context-hc-07.txt		draft-ietf-lpwan-coap-static-context-hc-08.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: November 25, 2019 Institut MINES TELECOM; IMT Atlantique		Expires: November 30, 2019 Institut MINES TELECOM; IMT Atlantique
	R. Andreasen		R. Andreasen
	Universidad de Buenos Aires		Universidad de Buenos Aires
	May 24, 2019		May 29, 2019
	LPWAN Static Context Header Compression (SCHC) for CoAP		LPWAN Static Context Header Compression (SCHC) for CoAP
	draft-ietf-lpwan-coap-static-context-hc-07		draft-ietf-lpwan-coap-static-context-hc-08
	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		protocols since CoAP
	uses a flexible header with a variable number of options themselves		uses a flexible header with a variable number of options themselves
	of variable length. The CoAP protocol is asymmetric in its message		of variable length. The CoAP protocol is asymmetric in its message
	format, the format of the header packet in the request messages is		format, the format of the header packet in the request messages is
	different from that in the response messages. Most of the		different from that in the response messages. Most of the
	skipping to change at page 1, line 42 ¶		skipping to change at page 1, line 42 ¶
	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 November 25, 2019.		This Internet-Draft will expire on November 30, 2019.
	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 47 ¶		skipping to change at page 2, line 47 ¶
	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. Time Scale . . . . . . . . . . . . . . . . . . . . . . . 10		6.4. Time Scale . . . . . . . . . . . . . . . . . . . . . . . 10
	6.5. OSCORE . . . . . . . . . . . . . . . . . . . . . . . . . 11		6.5. OSCORE . . . . . . . . . . . . . . . . . . . . . . . . . 11
	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 . . . . . . . . . . . . . . . 17		7.3. Example OSCORE Compression . . . . . . . . . . . . . . . 17
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
	9. Security considerations . . . . . . . . . . . . . . . . . . . 28		9. Security considerations . . . . . . . . . . . . . . . . . . . 27
	10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28		10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 27
	11. Normative References . . . . . . . . . . . . . . . . . . . . 29		11. Normative References . . . . . . . . . . . . . . . . . . . . 27
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
	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. Although CoAP was designed for constrained		constrained devices. Although CoAP was designed for constrained
	devices, the size of a CoAP header may still be too large for LPWAN		devices, the size of a CoAP header may still be too large for LPWAN
	constraints and some compression may be needed to reduce the header		constraints and some compression may be needed to reduce the header
	size.		size.
	[I-D.ietf-lpwan-ipv6-static-context-hc] defines a header compression		[I-D.ietf-lpwan-ipv6-static-context-hc] defines a header compression
	skipping to change at page 19, line 5 ¶		skipping to change at page 18, line 32 ¶
	Original msg length: 10		Original msg length: 10
	Figure 11: CoAP CONTENT Response		Figure 11: CoAP CONTENT Response
	The SCHC Rules for the Inner Compression include all fields that are		The SCHC Rules for the Inner Compression include all fields that are
	already present in a regular CoAP message, what is important is the		already present in a regular CoAP message, what is important is the
	order of appearance and inclusion of only those CoAP fields that go		order of appearance and inclusion of only those CoAP fields that go
	into the Plaintext, Figure 12.		into the Plaintext, Figure 12.
	Rule ID 0		Rule ID 0
	<<<<<<< Updated upstream		+---------------+--+--+-----------+-----------+-----------++------+
	+---------------+--+--+-----------+-----------+-----------++------+		| Field |FP|DI| Target | MO | CDA || Sent |
	| Field |FP|DI| Target | MO | CDA || Sent |		| | | | Value | | ||[bits]|
	| | | | Value | | ||[bits]|		+---------------+--+--+-----------+-----------+-----------++------+
	+---------------+--+--+-----------+-----------+-----------++------+		|CoAP Code | |up| 1 | equal |not-sent || |
	|CoAP Code | |up| 1 | equal |not-sent || |		|CoAP Code | |dw|[69,132] | match-map |match-sent || c |
	|CoAP Code | |dw|[69,132] | match-map |match-sent || c |		|CoAP Uri-Path | |up|temperature| equal |not-sent || |
	|CoAP Uri-Path | |up|temperature| equal |not-sent || |		|COAP Option-End| |dw| 0xFF | equal |not-sent || |
	|COAP Option-End| |dw| 0xFF | equal |not-sent || |		+---------------+--+--+-----------+-----------+-----------++------+
	+---------------+--+--+-----------+-----------+-----------++------+
	=======
	+----------------+--+--+-----------+-----------+-----------++--------+
	| Field |FP|DI| Target | MO | CDA || Sent |
	| | | | Value | | || [bits] |
	+----------------+--+--+-----------+-----------+-----------++--------+
	|CoAP Code | |up| 1 | equal |not-sent || |
	|CoAP Code | |dw|[69,132] | match-map |match-sent || c |
	|CoAP Uri-Path | |up|temperature| equal |not-sent || |
	|COAP Option-End | |dw| 0xFF | equal |not-sent || |
	+----------------+--+--+-----------+-----------+-----------++--------+
	>>>>>>> Stashed changes
	Figure 12: Inner SCHC Rules		Figure 12: Inner SCHC Rules
	Figure 13 shows the Plaintext obtained for our example GET Request		Figure 13 shows the Plaintext obtained for our example GET Request
	and follows the process of Inner Compression and Encryption until we		and follows the process of Inner Compression and Encryption until we
	end up with the Payload to be added in the outer OSCORE Message.		end up with the Payload to be added in the outer OSCORE Message.
	In this case the original message has no payload and its resulting		In this case the original message has no payload and its resulting
	Plaintext can be compressed up to only 1 byte (size of the Rule ID).		Plaintext can be compressed up to only 1 byte (size of the Rule ID).
	The AEAD algorithm preserves this length in its first output, but		The AEAD algorithm preserves this length in its first output, but
	skipping to change at page 25, line 5 ¶		skipping to change at page 24, line 13 ¶
	to be re-established.		to be re-established.
	The size s included in the kid context field MAY be masked off with		The size s included in the kid context field MAY be masked off with
	CDA MSB. The rest of the field could have additional bits masked		CDA MSB. The rest of the field could have additional bits masked
	off, or have the whole field be fixed with MO equal and CDA not-sent.		off, or have the whole field be fixed with MO equal and CDA not-sent.
	The same holds for the kid field.		The same holds for the kid field.
	Figure 17 shows a possible set of Outer Rules to compress the Outer		Figure 17 shows a possible set of Outer Rules to compress the Outer
	Header.		Header.
	Rule ID 0		Rule ID 0
	<<<<<<< Updated upstream		+-------------------+--+--+--------------+--------+---------++------+
	+-------------------+--+--+--------------+--------+---------++------+		| Field |FP|DI| Target | MO | CDA || Sent |
	| Field |FP|DI| Target | MO | CDA || Sent |		| | | | Value | | ||[bits]|
	| | | | Value | | ||[bits]|		+-------------------+--+--+--------------+--------+---------++------+
	+-------------------+--+--+--------------+--------+---------++------+		|CoAP version | |bi| 01 |equal |not-sent || |
	|CoAP version | |bi| 01 |equal |not-sent || |		|CoAP Type | |up| 0 |equal |not-sent || |
	|CoAP Type | |up| 0 |equal |not-sent || |		|CoAP Type | |dw| 2 |equal |not-sent || |
	|CoAP Type | |dw| 2 |equal |not-sent || |		|CoAP TKL | |bi| 1 |equal |not-sent || |
	|CoAP TKL | |bi| 1 |equal |not-sent || |		|CoAP Code | |up| 2 |equal |not-sent || |
	|CoAP Code | |up| 2 |equal |not-sent || |		|CoAP Code | |dw| 68 |equal |not-sent || |
	|CoAP Code | |dw| 68 |equal |not-sent || |		|CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM |
	|CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM |		|CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT |
	|CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT |		|CoAP OSCORE_flags | |up| 0x09 |equal |not-sent || |
	|CoAP OSCORE_flags | |up| 0x09 |equal |not-sent || |		|CoAP OSCORE_piv | |up| 0x00 |MSB(4) |LSB ||PPPP |
	|CoAP OSCORE_piv | |up| 0x00 |MSB(4) |LSB ||PPPP |		|COAP OSCORE_kid | |up|0x636c69656e70|MSB(52) |LSB ||KKKK |
	|COAP OSCORE_kid | |up|0x636c69656e70|MSB(52) |LSB ||KKKK |		|COAP OSCORE_kidctxt| |bi| b'' |equal |not-sent || |
	|COAP OSCORE_kidctxt| |bi| b'' |equal |not-sent || |		|CoAP OSCORE_flags | |dw| b'' |equal |not-sent || |
	|CoAP OSCORE_flags | |dw| b'' |equal |not-sent || |		|CoAP OSCORE_piv | |dw| b'' |equal |not-sent || |
	|CoAP OSCORE_piv | |dw| b'' |equal |not-sent || |		|CoAP OSCORE_kid | |dw| b'' |equal |not-sent || |
	|CoAP OSCORE_kid | |dw| b'' |equal |not-sent || |		|COAP Option-End | |dw| 0xFF |equal |not-sent || |
	|COAP Option-End | |dw| 0xFF |equal |not-sent || |		+-------------------+--+--+--------------+--------+---------++------+
	+-------------------+--+--+--------------+--------+---------++------+
	=======
	+-------------------+--+--+--------------+---------+-----------++--------+
	| Field |FP|DI| Target | MO | CDA || Sent |
	| | | | Value | | || [bits] |
	+-------------------+--+--+--------------+---------+-----------++--------+
	|CoAP version | |bi| 01 |equal |not-sent || |
	|CoAP Type | |up| 0 |equal |not-sent || |
	|CoAP Type | |dw| 2 |equal |not-sent || |
	|CoAP TKL | |bi| 1 |equal |not-sent || |
	|CoAP Code | |up| 2 |equal |not-sent || |
	|CoAP Code | |dw| 68 |equal |not-sent || |
	|CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM |
	|CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT |
	|CoAP OSCORE_flags | |up| 0x09 |equal |not-sent || |
	|CoAP OSCORE_piv | |up| 0x00 |MSB(4) |LSB ||PPPP |
	|COAP OSCORE_kid | |up|0x636c69656e70|MSB(52) |LSB ||KKKK |
	|COAP OSCORE_kidctxt| |bi| b'' |equal |not-sent || |
	|CoAP OSCORE_flags | |dw| b'' |equal |not-sent || |
	|CoAP OSCORE_piv | |dw| b'' |equal |not-sent || |
	|CoAP OSCORE_kid | |dw| b'' |equal |not-sent || |
	|COAP Option-End | |dw| 0xFF |equal |not-sent || |
	+-------------------+--+--+--------------+---------+-----------++--------+
	>>>>>>> Stashed changes
	Figure 17: Outer SCHC Rules		Figure 17: Outer SCHC Rules
	These Outer Rules are applied to the example GET Request and CONTENT		These Outer Rules are applied to the example GET Request and CONTENT
	Response. The resulting messages are shown in Figure 18 and		Response. The resulting messages are shown in Figure 18 and
	Figure 19.		Figure 19.
	Compressed message:		Compressed message:
	==================		==================
	0x001489458a9fc3686852f6c4 (12 bytes)		0x001489458a9fc3686852f6c4 (12 bytes)
	skipping to change at page 27, line 5 ¶		skipping to change at page 26, line 5 ¶
	Compressed msg length: 16 bytes		Compressed msg length: 16 bytes
	Figure 19: SCHC-OSCORE Compressed CONTENT Response		Figure 19: SCHC-OSCORE Compressed CONTENT Response
	For contrast, we compare these results with what would be obtained by		For contrast, we compare these results with what would be obtained by
	SCHC compressing the original CoAP messages without protecting them		SCHC compressing the original CoAP messages without protecting them
	with OSCORE. To do this, we compress the CoAP messages according to		with OSCORE. To do this, we compress the CoAP messages according to
	the SCHC rules in Figure 20.		the SCHC rules in Figure 20.
	Rule ID 1		Rule ID 1
	<<<<<<< Updated upstream		+---------------+--+--+-----------+---------+-----------++--------+
	+---------------+--+--+-----------+---------+-----------++--------+		| Field |FP|DI| Target | MO | CDA || Sent |
	| Field |FP|DI| Target | MO | CDA || Sent |		| | | | Value | | || [bits] |
	| | | | Value | | || [bits] |		+---------------+--+--+-----------+---------+-----------++--------+
	+---------------+--+--+-----------+---------+-----------++--------+		|CoAP version | |bi| 01 |equal |not-sent || |
	|CoAP version | |bi| 01 |equal |not-sent || |		|CoAP Type | |up| 0 |equal |not-sent || |
	|CoAP Type | |up| 0 |equal |not-sent || |		|CoAP Type | |dw| 2 |equal |not-sent || |
	|CoAP Type | |dw| 2 |equal |not-sent || |		|CoAP TKL | |bi| 1 |equal |not-sent || |
	|CoAP TKL | |bi| 1 |equal |not-sent || |		|CoAP Code | |up| 2 |equal |not-sent || |
	|CoAP Code | |up| 2 |equal |not-sent || |		|CoAP Code | |dw| [69,132] |equal |not-sent || |
	|CoAP Code | |dw| [69,132] |equal |not-sent || |		|CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM |
	|CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM |		|CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT |
	|CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT |		|CoAP Uri-Path | |up|temperature|equal |not-sent || |
	|CoAP Uri-Path | |up|temperature|equal |not-sent || |		|COAP Option-End| |dw| 0xFF |equal |not-sent || |
	|COAP Option-End| |dw| 0xFF |equal |not-sent || |		+---------------+--+--+-----------+---------+-----------++--------+
	+---------------+--+--+-----------+---------+-----------++--------+
	=======
	+---------------+--+--+-----------+---------+-----------++------------+
	| Field |FP|DI| Target | MO | CDA || Sent |
	| | | | Value | | || [bits] |
	+---------------+--+--+-----------+---------+-----------++------------+
	|CoAP version | |bi| 01 |equal |not-sent || |
	|CoAP Type | |up| 0 |equal |not-sent || |
	|CoAP Type | |dw| 2 |equal |not-sent || |
	|CoAP TKL | |bi| 1 |equal |not-sent || |
	|CoAP Code | |up| 2 |equal |not-sent || |
	|CoAP Code | |dw| [69,132] |equal |not-sent || |
	|CoAP MID | |bi| 0000 |MSB(12) |LSB ||MMMM |
	|CoAP Token | |bi| 0x80 |MSB(5) |LSB ||TTT |
	|CoAP Uri-Path | |up|temperature|equal |not-sent || |
	|COAP Option-End| |dw| 0xFF |equal |not-sent || |
	+---------------+--+--+-----------+---------+-----------++------------+
	>>>>>>> Stashed changes
	Figure 20: SCHC-CoAP Rules (No OSCORE)		Figure 20: SCHC-CoAP Rules (No OSCORE)
	This yields the results in Figure 21 for the Request, and Figure 22		This yields the results in Figure 21 for the Request, and Figure 22
	for the Response.		for the Response.
	Compressed message:		Compressed message:
	==================		==================
	0x0114		0x0114
	0x01 = Rule ID		0x01 = Rule ID
End of changes. 8 change blocks.
	111 lines changed or deleted		57 lines changed or added
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