rfc9952v1.txt		rfc9952.txt
	skipping to change at line 12 ¶		skipping to change at line 12 ¶
	Internet Engineering Task Force (IETF) M. S. Lenders		Internet Engineering Task Force (IETF) M. S. Lenders
	Request for Comments: 9952 TU Dresden		Request for Comments: 9952 TU Dresden
	Category: Informational C. Amsüss		Category: Informational C. Amsüss
	ISSN: 2070-1721		ISSN: 2070-1721
	T. C. Schmidt		T. C. Schmidt
	HAW Hamburg		HAW Hamburg
	M. Wählisch		M. Wählisch
	TU Dresden & Barkhausen Institut		TU Dresden & Barkhausen Institut
	March 2026		March 2026
	The Application-Layer Protocol Negotiation (ALPN) ID Specification for		Application-Layer Protocol Negotiation (ALPN) ID for CoAP over DTLS
	the Constrained Application Protocol (CoAP) over DTLS
	Abstract		Abstract
	This document specifies an Application-Layer Protocol Negotiation		This document specifies an Application-Layer Protocol Negotiation
	(ALPN) ID for transport-layer-secured Constrained Application		(ALPN) ID for Constrained Application Protocol (CoAP) services that
	Protocol (CoAP) services.		are secured by DTLS.
	Status of This Memo		Status of This Memo
	This document is not an Internet Standards Track specification; it is		This document is not an Internet Standards Track specification; it is
	published for informational purposes.		published for informational purposes.
	This document is a product of the Internet Engineering Task Force		This document is a product of the Internet Engineering Task Force
	(IETF). It represents the consensus of the IETF community. It has		(IETF). It represents the consensus of the IETF community. It has
	received public review and has been approved for publication by the		received public review and has been approved for publication by the
	Internet Engineering Steering Group (IESG). Not all documents		Internet Engineering Steering Group (IESG). Not all documents
	skipping to change at line 77 ¶		skipping to change at line 76 ¶
	parties to agree on an application-layer protocol during a Transport		parties to agree on an application-layer protocol during a Transport
	Layer Security (TLS) handshake using an ALPN ID [RFC7301]. This ALPN		Layer Security (TLS) handshake using an ALPN ID [RFC7301]. This ALPN
	ID can be discovered for services as part of Service Bindings (SVCBs)		ID can be discovered for services as part of Service Bindings (SVCBs)
	via the DNS, using SVCB resource records with the "alpn" Service		via the DNS, using SVCB resource records with the "alpn" Service
	Parameter Keys [RFC9460]. As an example, applications that use the		Parameter Keys [RFC9460]. As an example, applications that use the
	Constrained Application Protocol (CoAP) [RFC7252] can obtain this		Constrained Application Protocol (CoAP) [RFC7252] can obtain this
	information as part of the discovery of DNS over CoAP (DoC) servers		information as part of the discovery of DNS over CoAP (DoC) servers
	(see Section 3.2 of [PRE-RFC9953]) that deploy TLS 1.3 [RFC8446] as		(see Section 3.2 of [PRE-RFC9953]) that deploy TLS 1.3 [RFC8446] as
	well as Datagram Transport Layer Security (DTLS) 1.2 or 1.3 [RFC6347]		well as Datagram Transport Layer Security (DTLS) 1.2 or 1.3 [RFC6347]
	[RFC9147] to secure their messages. This document specifies an ALPN		[RFC9147] to secure their messages. This document specifies an ALPN
	ID for CoAP services that are secured by TLS using DTLS. An ALPN ID		ID for CoAP services that are secured by DTLS. An ALPN ID for CoAP
	for CoAP services secured by TLS has already been specified in		services secured by TLS has already been specified in [RFC8323].
	[RFC8323].
	2. Application-Layer Protocol Negotiation (ALPN) IDs		2. Application-Layer Protocol Negotiation (ALPN) IDs
	For CoAP over TLS, an ALPN ID is defined as "coap" in [RFC8323]. As		For CoAP over TLS, an ALPN ID is defined as "coap" in [RFC8323]. As
	it is not advisable to reuse the same ALPN ID for a different		it is not advisable to reuse the same ALPN ID for a different
	transport layer, an ALPN for CoAP over DTLS is registered in		transport layer, an ALPN for CoAP over DTLS is registered in
	Section 4.		Section 4.
	ALPN ID values have variable length. For CoAP over DTLS, a short		ALPN ID values have variable length. For CoAP over DTLS, a short
	value ("co") is allocated, as this can avoid fragmentation of Client		value ("co") is allocated, as this can avoid fragmentation of Client
	skipping to change at line 183 ¶		skipping to change at line 181 ¶
	<https://www.rfc-editor.org/info/rfc8446>.		<https://www.rfc-editor.org/info/rfc8446>.
	Acknowledgments		Acknowledgments
	We would like to thank Rich Salz for the expert review on the "co"		We would like to thank Rich Salz for the expert review on the "co"
	ALPN ID allocation. We would also like to thank Mohamed Boucadair		ALPN ID allocation. We would also like to thank Mohamed Boucadair
	and Ben Schwartz for their early reviews before WG adoption of this		and Ben Schwartz for their early reviews before WG adoption of this
	specification and Esko Dijk, Thomas Fossati, and Marco Tiloca for		specification and Esko Dijk, Thomas Fossati, and Marco Tiloca for
	their feedback and comments.		their feedback and comments.
			This work was supported in parts by the German Federal Ministry of
			Research, Technology, 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.
	Authors' Addresses		Authors' Addresses
	Martine Sophie Lenders		Martine Sophie Lenders
	TUD Dresden University of Technology		TUD Dresden University of Technology
	Helmholtzstr. 10		Helmholtzstr. 10
	D-01069 Dresden		D-01069 Dresden
	Germany		Germany
	Email: martine.lenders@tu-dresden.de		Email: martine.lenders@tu-dresden.de
	Christian Amsüss		Christian Amsüss
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