23 Facts About DNS

The DNS can be quickly and transparently updated, allowing a service's location on the network to change without affecting the end users, who continue to use the same hostname.

An important and ubiquitous function of the DNS is its central role in distributed Internet services such as cloud services and content delivery networks.

The key functionality of the DNS exploited here is that different users can simultaneously receive different translations for the same domain name, a key point of divergence from a traditional phone-book view of the DNS.

DNS reflects the structure of administrative responsibility in the Internet.

DNS can be partitioned according to class where the separate classes can be thought of as an array of parallel namespace trees.

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Limited set of ASCII characters permitted in the DNS prevented the representation of names and words of many languages in their native alphabets or scripts.

Typically, such caching DNS servers implement the recursive algorithm necessary to resolve a given name starting with the DNS root through to the authoritative name servers of the queried domain.

DNS resolvers are classified by a variety of query methods, such as recursive, non-recursive, and iterative.

The resolver, or another DNS server acting recursively on behalf of the resolver, negotiates use of recursive service using bits in the query headers.

Results obtained from a DNS request are always associated with the time to live, an expiration time after which the results must be discarded or refreshed.

Reverse DNS lookup is a query of the DNS for domain names when the IP address is known.

DNS serves other purposes in addition to translating names to IP addresses.

For instance, mail transfer agents use DNS to find the best mail server to deliver e-mail: An MX record provides a mapping between a domain and a mail exchanger; this can provide an additional layer of fault tolerance and load distribution.

DNS is used for efficient storage and distribution of IP addresses of blacklisted email hosts.

DNS protocol uses two types of DNS messages, queries and replies; both have the same format.

Use of DNS-over-UDP is limited by, among other things, its lack of transport-layer encryption, authentication, reliable delivery, and message length.

An IETF standard for encrypted DNS emerged in 2016, utilizing standard Transport Layer Security to protect the entire connection, rather than just the DNS payload.

Oblivious DNS was invented and implemented by researchers at Princeton University and the University of Chicago as an extension to unencrypted DNS, before DoH itself was standardized and widely deployed.

The privacy gains of Oblivious DNS can be garnered through the use of the preexisting Tor network of ingress and egress nodes, paired with the transport-layer encryption provided by TLS.

CLASS of a record is set to IN for common DNS records involving Internet hostnames, servers, or IP addresses.

DNS records belonging to wildcard domain names specify rules for generating resource records within a single DNS zone by substituting whole labels with matching components of the query name, including any specified descendants.

Original DNS protocol had limited provisions for extension with new features.

In 1999, Paul Vixie published in RFC 2671 an extension mechanism, called Extension Mechanisms for DNS that introduced optional protocol elements without increasing overhead when not in use.