Analysis of an Extension Dynamic Name Service – A discussion on DNS compliance with RFC 6891
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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.
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