92 lines
4.6 KiB
Markdown
92 lines
4.6 KiB
Markdown
<meta charset="utf-8" emacsmode="-*- markdown -*-">
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**A warm welcome to DNS**
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# Hello, and welcome to DNS!
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This series of documents attempts to provide a correct introduction to the
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Domain Name System as of 2018. The original RFCs remain the authoritative
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source of normative text, but this document tries to make this venerable
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protocol more accessible, while maintaining full alignment with all relevant
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and useful RFCs.
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This effort is developed cooperatively on GitHub, the repository can be
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found [https://github.com/ahupowerdns/hello-dns/](here) and help is highly
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welcome! Feedback can also be sent to bert.hubert@powerdns.com or
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[@PowerDNS_Bert](https://twitter.com/PowerDNS_Bert).
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Contributors so far include: Michał Kępień, Jan-Piet Mens, Andrew Babichev,
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Jacob Hoffman-Andrews, Peter van Dijk, Nathan Froyd, Gene McCulley,
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Charles-Henri Bruyand, jose nazario, Warren Kumari, Patrick Cloke, and
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Andrew Tunnell-Jones. Thanks!
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Although we start from relatively basic principles, the reader is expected
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to know what IP addresses are, what a (stub) resolver is and what an
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authoritative server is supposed to do. When in doubt: authoritative
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servers 'host' DNS data, 'resolvers' look up things over at authoritative
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servers and clients run 'stub resolvers' to look things up over at
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resolvers. This document is aimed at developers, but may also be of aid for
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administrators.
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DNS was originally written down in August 1979 in '[IEN
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116](https://www.rfc-editor.org/ien/ien116.txt)', part of a parallel
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series of documents describing the Internet. IEN 116-era DNS is not
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compatible with today's DNS. In 1983, RFC 882 and 883 were released,
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describing a version of the DNS very similar but not quite interoperable
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with the one we have today.
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DNS attained its modern form in 1987 when RFC 1034 and 1035 were published.
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Although much of 1034/1035 remains valid, these standards are not that easy
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to read because they were written in a very different time. There are 100s
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of pages of updates that can only be found in later documents.
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The main goal of this effort is not to contradict the DNS RFCs but to
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provide an easier entrypoint into understanding the Domain Name System.
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If you will, the goal is to be a mini "[TCP/IP
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Illustrated](https://en.wikipedia.org/wiki/TCP/IP_Illustrated)" of DNS. For
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more about the philosophy of these documents, and how to contribute, please read
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[meta.md](meta.md.html).
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Your help & insights are highly welcome!
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I want to thank Ólafur Guðmundsson and Job Snijders for their input and
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enthusiasm for improving the state of DNS.
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## Layout
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The content is spread out over several documents:
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* [The core of DNS](basic.md.html)
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* [Relevant to stub resolvers and applications](stub.md.html)
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* [Relevant to authoritative servers](auth.md.html)
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* [Relevant to resolvers](resolver.md.html)
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* [tdns: a 'from scratch' DNS library](tdns/README.md.html)
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* [tauth: a minimal but feature complete authoritative server](tdns/tauth.md.html)
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* [tres: a minimal but feature complete DNS resolver](tdns/tres.md.html)
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* [C API: a C library for doing DNS queries](tdns/c-api.md.html)
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* Optional elements: [EDNS, TSIG, Dynamic Updates, DNAME, DNS Cookies](optional.md.html)
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* [Privacy related](privacy.md.html): QName minimization, DNS-over-TLS, DNS-over-HTTPS, EDNS Padding
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* [DNSSEC](dnssec.md.html)
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* [non-IETF standards](non-ietf.md.html): RRL and RPZ
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* [Rare parts of DNS](rare.md.html) - not obsolete, but not frequently encountered in production
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We start off with a general introduction of DNS basics: what is a resource
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record, what is an RRSET, what is a zone, what is a zone-cut, how are packets
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laid out. This part is required reading for anyone ever wanting to query a
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nameserver or emit a valid response.
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We then specialize into what applications can expect when they send
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questions to a resolver, or what a stub resolver can expect.
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The next part is about what an authoritative server is supposed to do. On
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top of this, we describe in slightly less detail how a resolver could
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operate. Finally, there is a section on optional elements like EDNS, TSIG,
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Dynamic Updates and DNSSEC.
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RFCs, especially earlier ones, tend to describe servers that perform both
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authoritative and resolver functions. This turns out to make both code and
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troubleshooting harder. Therefore, in these documents, the authoritative and
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caching functions are described separately.
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Next up: [DNS Basics](basic.md.html).
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