Diff: rfc9952.original.md

	rfc9952.original.md	rfc9952.md
	---	---

	title: "ALPN ID Specification for CoAP over DTLS "	title: "Application-Layer Protocol Negotiation (ALPN) ID for CoAP over DTLS"
	abbrev: "CoRE ALPN"	abbrev: "ALPN ID for CoAP over DTLS"
	category: info	category: info

	docname: draft-ietf-core-coap-dtls-alpn-05	docname: draft-ietf-core-coap-dtls-alpn-05

	submissiontype: IETF # also: "independent", "editorial", "IAB", or "IRTF"	submissiontype: IETF
	number:	number: 9952
	date:	updates:
		obsoletes:
	consensus: true	consensus: true

		ipr: trust200902
		pi: [toc, symrefs, sortrefs]
		date: 2026-03
	v: 3	v: 3

	area: "Web and Internet Transport"	area: WIT
	workgroup: "Constrained RESTful Environments"	workgroup: core
	keyword:	keyword:
	- CoRE	- CoRE
	- CoAP	- CoAP
	- SVCB	- SVCB
	- DTLS	- DTLS
	- ALPN	- ALPN

	venue:
	group: "Constrained RESTful Environments"
	type: "Working Group"
	mail: "core@ietf.org"
	arch: "https://mailarchive.ietf.org/arch/browse/core/"
	github: "core-wg/coap-dtls-alpn"
	latest: "https://core-wg.github.io/coap-dtls-alpn/draft-ietf-core-coap-dtls-alpn.
	html"

	author:	author:
	- fullname: Martine Sophie Lenders	- fullname: Martine Sophie Lenders
	org: TUD Dresden University of Technology	org: TUD Dresden University of Technology
	abbrev: TU Dresden	abbrev: TU Dresden
	street: Helmholtzstr. 10	street: Helmholtzstr. 10
	city: Dresden	city: Dresden
	code: D-01069	code: D-01069
	country: Germany	country: Germany
	email: martine.lenders@tu-dresden.de	email: martine.lenders@tu-dresden.de

	skipping to change at line 65 ¶	skipping to change at line 62 ¶
	normative:	normative:
	RFC6347: dtls12	RFC6347: dtls12
	RFC7252: coap	RFC7252: coap
	RFC7301: alpn	RFC7301: alpn
	RFC9147: dtls13	RFC9147: dtls13
	RFC9460: svcb	RFC9460: svcb

	informative:	informative:
	RFC8323: coap-tcp	RFC8323: coap-tcp
	RFC8446: tls13	RFC8446: tls13

	I-D.ietf-core-dns-over-coap: doc	# I-D.ietf-core-dns-over-coap: doc
		PRE-RFC9953:
		-: doc
		title: >
		DNS over the Constrained Application Protocol (DoC)
		target: https://www.rfc-editor.org/info/rfc9953
		seriesinfo:
		RFC: PRE-9953
		DOI: 10.17487/PRE-RFC9953
		date: March 2026
		author:
		-
		fullname: Martine Sophie Lenders
		-
		fullname: Christian Amsüss
		-
		fullname: Cenk Gündoğan
		-
		fullname: Thomas C. Schmidt
		-
		fullname: Matthias Wählisch
	RFC4944: 6lo	RFC4944: 6lo

	--- abstract	--- abstract


		<!-- [rfced] FYI - We updated [I-D.ietf-core-dns-over-coap] to [PRE-RFC9953]
		for now. We will make the final updates in RFCXML (i.e., remove "PRE-").
		-->

		<!-- [I-D.ietf-core-dns-over-coap] - RFC 9953
		draft-ietf-core-dns-over-coap-20
		Companion document (C554)
		-->

		<!--[rfced] Document Title

		a) Please note that the document title has been updated as follows.
		Abbreviations have been expanded per Section 3.6 of RFC 7322 ("RFC Style
		Guide").

		In addition, is "Specification" essential to the title or may it be removed
		for conciseness?

		Original (document title):
		ALPN ID Specification for CoAP over DTLS

		Current:
		The Application-Layer Protocol Negotiation (ALPN) ID Specification for
		the Constrained Application Protocol (CoAP) over DTLS

		Perhaps:
		Application-Layer Protocol Negotiation (ALPN) ID for
		the Constrained Application Protocol (CoAP) over DTLS
		-->

	This document specifies an Application-Layer Protocol Negotiation (ALPN) ID for	This document specifies an Application-Layer Protocol Negotiation (ALPN) ID for

	transport-layer-secured Constrained Application Protocol (CoAP) services.	Constrained Application Protocol (CoAP) services that are secured by DTLS.

	--- middle	--- middle

	# Introduction	# Introduction

	Application-Layer Protocol Negotiation (ALPN) enables communicating parties to agree on an application-layer protocol during a Transport Layer Security (TLS) handshake us ing an ALPN ID {{-alpn}}.	Application-Layer Protocol Negotiation (ALPN) enables communicating parties to agree on an application-layer protocol during a Transport Layer Security (TLS) handshake us ing an ALPN ID {{-alpn}}.

	This ALPN ID can be discovered for services as part of Service Bindings (SVCB) via th e DNS, using SVCB resource records with the "alpn" Service Parameter Keys {{-svcb}}.	This ALPN ID can be discovered for services as part of Service Bindings (SVCBs) via t he DNS, using SVCB resource records with the "alpn" Service Parameter Keys {{-svcb}}.
	As an example, applications that use the Constrained Application Protocol (CoAP) {{-c oap}} can obtain this information as part of the discovery of DNS over CoAP (DoC) ser vers (see {{Section 3.2 of -doc}}) that deploy TLS 1.3 {{-tls13}} as well as Datagram Transport Layer Security (DTLS) 1.2 or 1.3 {{-dtls12}} {{-dtls13}} to secure their m essages.	As an example, applications that use the Constrained Application Protocol (CoAP) {{-c oap}} can obtain this information as part of the discovery of DNS over CoAP (DoC) ser vers (see {{Section 3.2 of -doc}}) that deploy TLS 1.3 {{-tls13}} as well as Datagram Transport Layer Security (DTLS) 1.2 or 1.3 {{-dtls12}} {{-dtls13}} to secure their m essages.

	This document specifies an ALPN ID for CoAP services that are secured by transport la yer security using DTLS.	This document specifies an ALPN ID for CoAP services that are secured by DTLS.
	An ALPN ID for CoAP services secured by TLS has already been specified in {{-coap-tcp }}.	An ALPN ID for CoAP services secured by TLS has already been specified in {{-coap-tcp }}.

	# Application-Layer Protocol Negotiation (ALPN) IDs	# Application-Layer Protocol Negotiation (ALPN) IDs


	For CoAP over TLS, an ALPN ID was defined as "coap" in {{-coap-tcp}}.	For CoAP over TLS, an ALPN ID is defined as "coap" in {{-coap-tcp}}.
	As it is not advisable to re-use the same ALPN ID for a different transport layer, an	As it is not advisable to reuse the same ALPN ID for a different transport layer, an
	ALPN for	ALPN for
	CoAP over DTLS is registered in {{iana-coap-alpn}}.	CoAP over DTLS is registered in {{iana}}.

	ALPN ID values have variable length.	ALPN ID values have variable length.
	For CoAP over DTLS, a short value ("co") is allocated, as this can avoid fragmentatio n of Client Hello and Server Hello messages in constrained networks with link-layer f ragmentation, such as 6LoWPAN {{-6lo}}.	For CoAP over DTLS, a short value ("co") is allocated, as this can avoid fragmentatio n of Client Hello and Server Hello messages in constrained networks with link-layer f ragmentation, such as 6LoWPAN {{-6lo}}.

	To discover CoAP services that secure their messages with TLS or DTLS, the ALPN IDs " coap" and "co" can be used, respectively, in	To discover CoAP services that secure their messages with TLS or DTLS, the ALPN IDs " coap" and "co" can be used, respectively, in

	the same manner as for any other service secured with transport layer security, as	the same manner as for any other service secured with TLS, as
	described in {{-svcb}}.	described in {{-svcb}}.
	The discovery of CoAP services that rely on other security mechanisms is out of the s cope of this document.	The discovery of CoAP services that rely on other security mechanisms is out of the s cope of this document.

	# Security Considerations	# Security Considerations


	Any security considerations on ALPN (see {{-alpn}}) and SVCB resource records (see {{ -svcb}}) also apply to this document.	Any security considerations for ALPN (see {{-alpn}}) and SVCB resource records (see { {-svcb}}) also apply to this document.

	# IANA Considerations {#iana}	# IANA Considerations {#iana}


	[^replace-xxxx]	IANA has added the following entry to the "TLS Application-Layer Protocol Negotiation
		(ALPN) Protocol IDs" registry in the "Transport Layer Security (TLS) Extensions" reg
	[^replace-xxxx]: RFC Ed.: throughout this section, please replace	istry group.
	RFC-XXXX with the RFC number of this specification and remove this
	note.

	This document has the following actions for IANA.

	## TLS ALPN for CoAP {#iana-coap-alpn}

	The following entry has been added to the "TLS Application-Layer Protocol Negotiation
	(ALPN) Protocol IDs" registry, which is part of the "Transport Layer Security (TLS)
	Extensions" registry group.


	* Protocol: CoAP (over DTLS)	\| Protocol \| Identification Sequence \| Reference \|
	* Identification sequence: 0x63 0x6f ("co")	\| CoAP (over DTLS) \| 0x63 0x6f ("co") \| {{-coap}}, RFC 9952 \|
	* Reference: {{-coap}} and \[RFC-XXXX\]	{: title="TLS Application-Layer Protocol Negotiation (ALPN) Protocol IDs Registry" #t
		able1}

	Note that {{-coap}} does not define the use of the ALPN TLS extension during the DTLS connection handshake.	Note that {{-coap}} does not define the use of the ALPN TLS extension during the DTLS connection handshake.

	This document does not change this behavior, and thus does not establish any rules li ke those in {{Section 8.2 of -coap-tcp}}.	This document does not change this behavior and thus does not establish any rules lik e those in {{Section 8.2 of -coap-tcp}}.

	--- back	--- back


	# Change Log

	## Since [draft-ietf-core-coap-dtls-alpn-04]

	- Address Deb Cooley's IESG ballot COMMENT

	## Since [draft-ietf-core-coap-dtls-alpn-03]

	- Make DTLS references normative

	## Since [draft-ietf-core-coap-dtls-alpn-02]

	- Address shepherd review

	## Since [draft-ietf-core-coap-dtls-alpn-01]

	- Address review by Esko Dijk
	- Address review by Marco Tiloca

	## Since [draft-ietf-core-coap-dtls-alpn-00]

	- Fix ALPN ID for CoAP over TLS
	- Change intended status to Informational

	[draft-ietf-core-coap-dtls-alpn-04]: https://datatracker.ietf.org/doc/draft-ietf-core
	-coap-dtls-alpn/04/
	[draft-ietf-core-coap-dtls-alpn-03]: https://datatracker.ietf.org/doc/draft-ietf-core
	-coap-dtls-alpn/03/
	[draft-ietf-core-coap-dtls-alpn-02]: https://datatracker.ietf.org/doc/draft-ietf-core
	-coap-dtls-alpn/02/
	[draft-ietf-core-coap-dtls-alpn-01]: https://datatracker.ietf.org/doc/draft-ietf-core
	-coap-dtls-alpn/01/
	[draft-ietf-core-coap-dtls-alpn-00]: https://datatracker.ietf.org/doc/draft-ietf-core
	-coap-dtls-alpn/00/

	# Acknowledgments	# Acknowledgments
	{:unnumbered}	{:unnumbered}


	We like to thank Rich Salz for the expert review on the "co" ALPN ID allocation.	We would like to thank {{{Rich Salz}}} for the expert review on the "co" ALPN ID allo
	We also like to thank Mohamed Boucadair and Ben Schwartz for their early review befor	cation.
	e WG adoption	We would also like to thank {{{Mohamed Boucadair}}} and {{{Ben Schwartz}}} for their
	of this draft and Esko Dijk, Thomas Fossati, and Marco Tiloca for their feedback and	early reviews before WG adoption
	comments.	of this specification and {{{Esko Dijk}}}, {{{Thomas Fossati}}}, and {{{Marco Tiloca}
		}} for their feedback and comments.

		This work was supported in parts by the German Federal Ministry of Research, Technolo
		gy, and Space (BMFTR) under the grant numbers 16KIS1386K (TU Dresden) and 16KIS1387 (
		HAW Hamburg) within the research project PIVOT and under the grant numbers 16KIS1694K
		(TU Dresden) and 16KIS1695 (HAW Hamburg) within the research project C-ray4edge.

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