====== The Domain Name System ======

The Domain Name System, or DNS for short, is something like the telephone directory for the Internet: if you type in a domain name such as www.posadis.org in, for example, your browser, it will be looked up and converted to an Internet IP number, the Internet equivalent of a telephone number, which is used by your computer to make a connection. See the following diagram:

{{ dns-diagram.png }}

Apart from converting domain names to IP numbers, DNS also plays an important role in delivering e-mail and blocking spam. A DNS server is a program that answers DNS requests from clients. Whether you need a DNS server depends on your particular situation.

  * You //need// a Domain Name Server if you want to serve information about an Internet domain name (this task is called [[dns:authoritative DNS]]). You can, for a small or bigger fee, let somebody else do DNS, but you can do it yourself by running your own DNS server as well.
  * You //can use// a Domain Name Server if you want to connect a local network to the Internet. Setting up a DNS server will speed up the domain name lookup process for your local network ([[dns:caching]] DNS). Additionally, you can give names to computers on your local network. The latter goal van also be achieved by using a file called [[dns:hosts]] on your client PCs. Using hosts instead of DNS can safe you time if you have a relatively small and static network, though it is not as scalable and doesn't have as much applications as setting up a local DNS zone.

===== Basic DNS =====

There is a [[dns:DNS overview]] that provides, well, an overview of what makes the Domain Name System tick. You can also learn [[dns:Using DNS for naming hosts|how to use DNS for naming hosts]], [[dns:Using DNS for e-mail|how to use DNS for e-mail]], and [[dns:Reverse mapping|how to map IP numbers to domain names]].

For [[dns:Authoritative DNS]]: DNS data is stored in zones; you can see [[dns:What makes up a zone]]. The fundamental pieces of data in the Domain Name System are [[dns:Resource records]], which are stored by [[dns:authoritative DNS]] servers in [[dns:Master files]].

For caching DNS, refer to the article about [[dns:Caching]]. If you run a caching DNS server, you'll also want to know about [[dns:Setting the DNS server on workstations]].

Communicating to DNS servers happens with the standard [[dns:DNS ports]]. A technical overview of the lower-level operation of DNS is provided in the article about [[dns:DNS Messages]].

Also, check out the [[dns:links]] to other websites about the Domain Name System, and the [[dns:news|DNS in the News]] section to find out what's happening in the DNS world.

===== Advanced topics =====

  * [[dns:news:20050202-bright-ip-spoofing|Article about DNS cache spoofing]]
  * [[dns:news:20050308-wildcard-phishing|Article about using DNS for phishing]]
  * [[dns:DNS cache snooping]]
  * [[dns:Custom root nameservers]]