Internet Engineering Task Force D. Yuyama Internet-Draft Keio University / WIDE Project Intended status: Standards Track H. Asai Expires: 25 April 2024 Preferred Networks / WIDE Project 23 October 2023 Next Header Option in UDP Options draft-daiya-tsvwg-udp-options-next-header-00 Abstract This document defines the next header option in UDP options. The next header option specifies the protocol immediately following the UDP header. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 25 April 2024. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Yuyama & Asai Expires 25 April 2024 [Page 1] Internet-Draft Proto Num Opt in UDP Options October 2023 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions used in this document . . . . . . . . . . . . . . 3 3. Transport Protocols based on UDP . . . . . . . . . . . . . . 3 4. UDP-based Protocols Extensibility . . . . . . . . . . . . . . 3 4.1. Spread of applications using UDP-based transport protocols . . . . . . . . . . . . . . . . . . . . . . . . 3 4.2. Concerns about limited UDP-based transport extensibility . . . . . . . . . . . . . . . . . . . . . . 4 5. Value of Next Header Option . . . . . . . . . . . . . . . . . 4 6. Option Format . . . . . . . . . . . . . . . . . . . . . . . . 4 7. Recommendation . . . . . . . . . . . . . . . . . . . . . . . 4 7.1. Next Header Options is for Transport Ends . . . . . . . . 5 7.2. TBD . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 9. Security Considerations . . . . . . . . . . . . . . . . . . . 5 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 10.1. Normative References . . . . . . . . . . . . . . . . . . 5 10.2. Informative References . . . . . . . . . . . . . . . . . 5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction The User Datagram Protocol [RFC0768] provides only a port number and a checksum as a minimum functional transport protocol. Because of its simplicity and interoperability in the Internet, new transport protocols such as QUIC [RFC9000] and SCTP [RFC6951] are implemented over UDP. However, UDP has no field in the header that identifies the encapsulated protocol. Typically, the IANA port number [IANA_service_names_port_numbers] is used for that purpose, but the port number corresponds to the service of the communication. We argue that it is a clear misuse of the port number to indicate the protocol on UDP. Currently, it is not possible to provide the UDP layer with information about the transport protocols implemented on top of UDP. Transport Options for UDP [I-D.ietf-tsvwg-udp-options] is a proposal for extending UDP to have an options area. This creates an options area behind the UDP payload to allow TLV(Type-Length-Value) format options to be added. This document describes the next header option. This option allows information about the protocol following the UDP header. This option is provided as one of the UDP options. Yuyama & Asai Expires 25 April 2024 [Page 2] Internet-Draft Proto Num Opt in UDP Options October 2023 2. Conventions used in this document 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. 3. Transport Protocols based on UDP Using new IP-based transport protocols on the Internet is difficult bacause of ossified middle boxes. Therefore, in order to maintain affinity with the Internet, it is often used to encapsulate the transport protocol with UDP. The following are transport protocols used for UDP-based. Registered in IP Protocol Numbers * DCCP [RFC6773] - DCCP-UDP: A Datagram Congestion Control Protocol UDP Encapsulation for NAT Traversal * SCTP [RFC6951] - UDP Encapsulation of Stream Control Transmission Protocol (SCTP) Packets for End-Host to End-Host Communication Not registered in IP Protocol Numbers * QUIC [RFC9000] - QUIC: A UDP-Based Multiplexed and Secure Transport 4. UDP-based Protocols Extensibility 4.1. Spread of applications using UDP-based transport protocols Transport protocols implemented based on UDP such as QUIC often are used as transport protocols for existing applications. The following are examples of applications that operate using UDP- based transport protocols. HTTP * HTTP/3 [RFC9114] - HTTP over QUIC, uses UDP port 443. DNS * DNS over Datagram Transport Layer Security [RFC8094] - uses UDP port 853. Yuyama & Asai Expires 25 April 2024 [Page 3] Internet-Draft Proto Num Opt in UDP Options October 2023 * DNS over Dedicated QUIC Connections [RFC9250] - uses UDP port 853, same as DNS over DTLS. 4.2. Concerns about limited UDP-based transport extensibility The UDP header does not have any information to identify the encapsulated protocol. Without this information, problems may arise when there are applications that can communicate with multiple transport protocols using the same port number. In the case of client-server communication, the server cannot instantly determine which transport protocol was used to send the packet sent by the client. For instance, when a new transport protocol other than QUIC is developed and used that is based on UDP and works as a transport for HTTP, the server will not be able to instantly identify whether QUIC is used as the transport protocol or the new one is used. Therefore, if the next protocol after the UDP header is a transport protocol, it should be possible to have a field in the UDP layer information that identifies the protocol that follows the UDP header. 5. Value of Next Header Option The next header option is a number to identify the protocol immediately following the UDP header. This number used be the same as IP Protocol Numbers[IANA_protocol_numbers] In many cases, the protocol number is available, but a new protocol number is needed for protocols that do not have a protocol number, such as QUIC. 6. Option Format The UDP option is provided in the form of a TLV. The value of next header option is represented by 8 bits. It is shown in Figure 1. +---------+---------+---------+---------+ | Kind=10 | Len=4 | Nxt Hdr | Padding | +---------+---------+---------+---------+ 1 byte 1 byte 1 byte 1 byte Figure 1: Option format 7. Recommendation Yuyama & Asai Expires 25 April 2024 [Page 4] Internet-Draft Proto Num Opt in UDP Options October 2023 7.1. Next Header Options is for Transport Ends The next header option is intended to be interpreted by transport ends. As with the original UDP Options, not intended to be interpreted in-transit. 7.2. TBD TBD 8. IANA Considerations On publication, request IANA to assign one number from the Safe Options range of the UDP Option Kind Number as Next Header (NXTHDR). 9. Security Considerations This document should not affect the security of the Internet. 10. References 10.1. Normative References [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI 10.17487/RFC0768, August 1980, . [I-D.ietf-tsvwg-udp-options] Touch, J. D., "Transport Options for UDP", Work in Progress, Internet-Draft, draft-ietf-tsvwg-udp-options-23, 15 September 2023, . 10.2. Informative References [IANA_service_names_port_numbers] IANA, "Service Name and Transport Protocol Port Number Registry", . Yuyama & Asai Expires 25 April 2024 [Page 5] Internet-Draft Proto Num Opt in UDP Options October 2023 [IANA_protocol_numbers] IANA, "Protocol Numbers", . [RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, May 2021, . [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A Datagram Congestion Control Protocol UDP Encapsulation for NAT Traversal", RFC 6773, DOI 10.17487/RFC6773, November 2012, . [RFC6951] Tuexen, M. and R. Stewart, "UDP Encapsulation of Stream Control Transmission Protocol (SCTP) Packets for End-Host to End-Host Communication", RFC 6951, DOI 10.17487/RFC6951, May 2013, . [RFC9114] Bishop, M., Ed., "HTTP/3", RFC 9114, DOI 10.17487/RFC9114, June 2022, . [RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram Transport Layer Security (DTLS)", RFC 8094, DOI 10.17487/RFC8094, February 2017, . [RFC9250] Huitema, C., Dickinson, S., and A. Mankin, "DNS over Dedicated QUIC Connections", RFC 9250, DOI 10.17487/RFC9250, May 2022, . Acknowledgements TBD Authors' Addresses Daiya Yuyama Keio University / WIDE Project 5322 Endo Fujisawa, Kanagawa 252-0882 Japan Email: daiya@sfc.wide.ad.jp Yuyama & Asai Expires 25 April 2024 [Page 6] Internet-Draft Proto Num Opt in UDP Options October 2023 Hirochika Asai Preferred Networks / WIDE Project 1-6-1 Otemachi Chiyoda, Tokyo 100-0004 Japan Email: panda@wide.ad.jp Yuyama & Asai Expires 25 April 2024 [Page 7]