Domain Name Service (DNS) resolution is a mechanism that resolves the symbolic names of networked devices to their corresponding Internet Protocol (IP) address. With the emergence of the document that describes an extension to a DNS service definition, it was becoming apparent that DNS implementations will need to comply with some modified DNS behaviour. One such modification is that DNS continues to use the User Datagram Protocol (UDP) to transmit DNS payloads that are longer than 512 bytes. Until the emergence of the Extension DNS (EDNS) specification, DNS servers would switch over from UDP to Transmission Control Protocol (TCP) if the response payload was larger than 512 bytes. With the new EDNS capability, it was required that DNS replies would continue to provide responses as UDP datagrams even though the response was larger than 512 bytes. To the author's best knowledge, there are no academic articles dealing with the assessment of the DNS servers against EDNS specification. This paper examines the level of compatibility for a number of public DNS servers for some popular internet domains. It also explores behaviour of some contemporary DNS implementations such as Microsoft Windows 2012, 2016 and 2019 as well as Linux-based BIND in regards to the EDNS.

中文翻译：

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扩展动态名称服务分析——关于 DNS 与 RFC 6891 合规性的讨论

域名服务 (DNS) 解析是一种将联网设备的符号名称解析为其相应 Internet 协议 (IP) 地址的机制。随着描述 DNS 服务定义扩展的文档的出现，很明显 DNS 实施将需要遵守某些修改后的 DNS 行为。其中一项修改是 DNS 继续使用用户数据报协议 (UDP) 来传输长度超过 512 字节的 DNS 有效负载。在扩展 DNS (EDNS) 规范出现之前，如果响应负载大于 512 字节，DNS 服务器将从 UDP 切换到传输控制协议 (TCP)。使用新的 EDNS 功能，即使响应大于 512 字节，也要求 DNS 回复将继续以 UDP 数据报的形式提供响应。据作者所知，没有学术文章涉及根据 EDNS 规范评估 DNS 服务器。本文研究了一些流行的 Internet 域的许多公共 DNS 服务器的兼容性级别。它还探讨了一些当代 DNS 实现的行为，例如 Microsoft Windows 2012、2016 和 2019 以及与 EDNS 相关的基于 Linux 的 BIND。