Diff: rfc9952v1.txt - rfc9952.txt

	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

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	1. Introduction	1. Introduction

	Application-Layer Protocol Negotiation (ALPN) enables communicating	Application-Layer Protocol Negotiation (ALPN) enables communicating
	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 [RFC9953]) that deploy TLS 1.3 [RFC8446] as well
	well as Datagram Transport Layer Security (DTLS) 1.2 or 1.3 [RFC6347]	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 154 ¶	skipping to change at line 152 ¶
	1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,	1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
	<https://www.rfc-editor.org/info/rfc9147>.	<https://www.rfc-editor.org/info/rfc9147>.

	[RFC9460] Schwartz, B., Bishop, M., and E. Nygren, "Service Binding	[RFC9460] Schwartz, B., Bishop, M., and E. Nygren, "Service Binding
	and Parameter Specification via the DNS (SVCB and HTTPS	and Parameter Specification via the DNS (SVCB and HTTPS
	Resource Records)", RFC 9460, DOI 10.17487/RFC9460,	Resource Records)", RFC 9460, DOI 10.17487/RFC9460,
	November 2023, <https://www.rfc-editor.org/info/rfc9460>.	November 2023, <https://www.rfc-editor.org/info/rfc9460>.

	5.2. Informative References	5.2. Informative References


	[PRE-RFC9953]
	Lenders, M. S., Amsüss, C., Gündoğan, C., Schmidt, T. C.,
	and M. Wählisch, "DNS over the Constrained Application
	Protocol (DoC)", RFC PRE-9953, DOI 10.17487/PRE-RFC9953,
	March 2026, <https://www.rfc-editor.org/info/rfc9953>.

	[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,	[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
	"Transmission of IPv6 Packets over IEEE 802.15.4	"Transmission of IPv6 Packets over IEEE 802.15.4
	Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,	Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
	<https://www.rfc-editor.org/info/rfc4944>.	<https://www.rfc-editor.org/info/rfc4944>.

	[RFC8323] Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,	[RFC8323] Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
	Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained	Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained
	Application Protocol) over TCP, TLS, and WebSockets",	Application Protocol) over TCP, TLS, and WebSockets",
	RFC 8323, DOI 10.17487/RFC8323, February 2018,	RFC 8323, DOI 10.17487/RFC8323, February 2018,
	<https://www.rfc-editor.org/info/rfc8323>.	<https://www.rfc-editor.org/info/rfc8323>.

	[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol	[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
	Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,	Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
	<https://www.rfc-editor.org/info/rfc8446>.	<https://www.rfc-editor.org/info/rfc8446>.


		[RFC9953] Lenders, M. S., Amsüss, C., Gündoğan, C., Schmidt, T. C.,
		and M. Wählisch, "DNS over the Constrained Application
		Protocol (DoC)", RFC 9953, DOI 10.17487/RFC9953, March
		2026, <https://www.rfc-editor.org/info/rfc9953>.

	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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