]> Japan Registry Services Co., Ltd.

fujiwara@jprs.co.jp

operations Internet-Draft 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.

Introduction 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.

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 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 .

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. 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.

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.

IANA Considerations This document requests no IANA actions.

Security Considerations

The DNS uses glue records to allow iterative clients to find the addresses of name servers that are contained within a delegated zone. Authoritative servers are expected to return all available glue records for in-domain name servers in a referral response. If message size constraints prevent the inclusion of all glue records for in-domain name servers, the server must set the TC (Truncated) flag to inform the client that the response is incomplete and that the client should use another transport to retrieve the full response. This document updates RFC 1034 to clarify correct server behavior. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. The Domain Name System (DNS) is defined in literally dozens of different RFCs. The terminology used by implementers and developers of DNS protocols, and by operators of DNS systems, has sometimes changed in the decades since the DNS was first defined. This document gives current definitions for many of the terms used in the DNS in a single document. This document obsoletes RFC 7719 and updates RFC 2308. SIDN Labs InternetNZ USC/ISI USC/ISI

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)