Network Working Group K. Fujiwara Internet-Draft JPRS Intended status: Best Current Practice 1 March 2024 Expires: 2 September 2024 Unrelated name server name requirement draft-fujiwara-dnsop-unrelated-name-server-00 Abstract Unrelated(out-of-bailiwick) name server names are required for DNS hosting services. However, using unrelated name server names increases the name resolution costs. This document proposes using in-domain name servers as much as possible for name resolution of unrelated name server names to reduce the name resolution costs. 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/. 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Fujiwara Expires 2 September 2024 [Page 1] Internet-Draft unrelated-name-server March 2024 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 4. Recommendations for unrelated name server names . . . . . . . 3 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 6. Security Considerations . . . . . . . . . . . . . . . . . . . 3 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 3 7.1. Normative References . . . . . . . . . . . . . . . . . . 3 7.2. Informative References . . . . . . . . . . . . . . . . . 4 Appendix A. Examples of complex unrelated delegations . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction [RFC9471] states that all in-domain glue records are attached to the delegation response. Therefore, using in-domain name server names for DNS delegation minimizes name resolution costs. Unrelated (or, rarely sibling) name server names are used/required for DNS hosting services. However, using unrelated name server names increases the name resolution costs and may increase the likelihood of name resolution errors. This document proposes to use in-domain name servers as much as possible for name resolution of unrelated name server names in order to reduce the name resolution costs. 2. Terminology 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 BCP14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. Many of the specialized terms used in this document are defined in DNS Terminology [RFC8499]. Fujiwara Expires 2 September 2024 [Page 2] Internet-Draft unrelated-name-server March 2024 3. Problem Statement Unrelated(out-of-bailiwick) name server names are required for DNS hosting services. However, using unrelated name server names increases the name resolution costs. For some domain names, there are multiple layers of dependence on unrelated name server names when resolving the name. Furthermore, there are cases where cyclic dependencies in delegation occur, settings that depend on sibling glue, and cases where the sibling glue disappears or some name servers stop responding, making it impossible to resolve names. [Tsuname2021] pointed out attacks and countermeasures that use increased load due to cyclic dependencies. Many cyclic delegations are likely due to misconfigurations. To avoid complex name resolution and misconfigurations, the recommendation to prevent unrelated name server names whenever possible is needed. 4. Recommendations for unrelated name server names Although it is acceptable to use unrelated name server names for DNS delegation, the domain names that host the name server names MUST be resolvable by delegations using one or more in-domain name server names. It is desirable for DNS hosting services that use unrelated name server names in their services to be able to resolve their name server names using only in-domain name server names. 5. IANA Considerations This document requests no IANA actions. 6. Security Considerations 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Fujiwara Expires 2 September 2024 [Page 3] Internet-Draft unrelated-name-server March 2024 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499, January 2019, . [RFC9471] Andrews, M., Huque, S., Wouters, P., and D. Wessels, "DNS Glue Requirements in Referral Responses", RFC 9471, DOI 10.17487/RFC9471, September 2023, . 7.2. Informative References [Tsuname2021] Moura, G. M., Sebastian Castro, John S Heidemann, and Wes Hardaker, "TsuNAME: exploiting misconfiguration and vulnerability to DDoS DNS", IMC '21: Proceedings of the 21st ACM Internet Measurement Conference , 2021. Appendix A. Examples of complex unrelated delegations "com" TLD depends on "[a-m].gtld-servers.net" (sibling name server names) "gtld-servers.net" depends on "av[1-4].nsdlt.com.". (unrelated name server names) Finally, "nstld.com" depends on "av[1-4].nstld.com.". (in-domain) Author's Address Kazunori Fujiwara Japan Registry Services Co., Ltd. Email: fujiwara@jprs.co.jp Fujiwara Expires 2 September 2024 [Page 4]