Internet Engineering Task Force D. Yuyama Internet-Draft Keio University / WIDE Project Intended status: Standards Track H. Asai Expires: 11 January 2024 Preferred Networks / WIDE Project 10 July 2023 Protocol Number Option in UDP Options draft-daiya-tsvwg-udp-options-protocol-number-00 Abstract This document defines the protocol number option in UDP options. The protocol number 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 11 January 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 11 January 2024 [Page 1] Internet-Draft Proto Num Opt in UDP Options July 2023 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions used in this document . . . . . . . . . . . . . . 3 3. UDP-based Protocol Extensibility . . . . . . . . . . . . . . 3 3.1. Spread of applications using UDP-based transport protocols . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2. Concerns about limited UDP-based transport extensibility . . . . . . . . . . . . . . . . . . . . . . 3 4. Protocol Number in UDP Options . . . . . . . . . . . . . . . 4 5. Option Format . . . . . . . . . . . . . . . . . . . . . . . . 4 6. Recommendation . . . . . . . . . . . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 8. Security Considerations . . . . . . . . . . . . . . . . . . . 4 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 9.1. Normative References . . . . . . . . . . . . . . . . . . 4 9.2. 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 that maps UDP to 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, using the difference between the total length field in the IP header and the length field in the UDP field. It allows options to be added in TLV(Type-Length- Value) format. This document describes the protocol number option, which allows information about the protocol following the UDP header to be provided in the UDP options area. Yuyama & Asai Expires 11 January 2024 [Page 2] Internet-Draft Proto Num Opt in UDP Options July 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. UDP-based Protocol Extensibility 3.1. Spread of applications using UDP-based transport protocols Frequently, new transport protocols are implemented based on UDP, such as QUIC, and 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. * DNS over Dedicated QUIC Connections [RFC9250] - uses UDP port 853, same as DNS over DTLS. 3.2. 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. Yuyama & Asai Expires 11 January 2024 [Page 3] Internet-Draft Proto Num Opt in UDP Options July 2023 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. 4. Protocol Number in UDP Options The protocol number is a number to identify the protocol immediately following the UDP header. In many cases, the port number of the transport layer is available for this number, but a new protocol number is needed for protocols that do not have a port number, such as QUIC. 5. Option Format The UDP option is provided in the form of a TLV. The protocol number is represented by 16 bits. It is shown in Figure 1. +---------+---------+---------+---------+ | Kind=10 | Len=4 | Next Header Num | +---------+---------+---------+---------+ 1 byte 1 byte 2 bytes Figure 1: Option format 6. Recommendation TBD 7. IANA Considerations On publication, request IANA to create a new registry for protocol numbers. The details of the number will be described in a later revision. Also, request IANA to assign one number from the Safe Options range of the UDP Option Kind Number as Protocol Number (PROTONUM). 8. Security Considerations This document should not affect the security of the Internet. 9. References 9.1. 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, . Yuyama & Asai Expires 11 January 2024 [Page 4] Internet-Draft Proto Num Opt in UDP Options July 2023 [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-22, 9 June 2023, . 9.2. Informative References [IANA_service_names_port_numbers] IANA, "Service Name and Transport Protocol Port Number Registry", . [RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, May 2021, . [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, . Yuyama & Asai Expires 11 January 2024 [Page 5] Internet-Draft Proto Num Opt in UDP Options July 2023 Acknowledgements TBD Authors' Addresses Daiya Yuyama Keio University / WIDE Project Endo 5322 Fujisawa, Kanagawa 252-0882 Japan Email: daiya@sfc.wide.ad.jp Hirochika Asai Preferred Networks / WIDE Project 1-6-1 Otemachi Chiyoda, Tokyo 100-0004 Japan Email: panda@wide.ad.jp Yuyama & Asai Expires 11 January 2024 [Page 6]