This is how the domain name system works: the big domain glossary part 2
Although the majority of us in Europe use the internet at least once a day, we hardly stop to think how it works. For example, once you have entered the domain name in your browser do you know why a website then appears? Where is the information about the domain and the website stored and how are they related? This article is the second instalment of our big domain glossary series and aims to shed a little more light on the domain name system (DNS), root server and IP address.
Domain name system (DNS):
The DNS is a decentralized naming system for computers or devices connected to the internet. Similar to an individual with multiple telephone numbers in a phone directory, each computer or device has multiple IP addresses associated with its name. These IP addresses are necessary to contact the internet. A computer uses the DNS when trying to access a website via typing in its internet address (URL) or when sending an e-mail to a certain receiver. If you type in a URL in your web browser such as www.1and1.co.uk, the URL is converted into the respective IP address (e.g.: 192.0.2.42) via the DNS and thereby leads your computer to the correct content.
The DNS is also a registry for further information about services that are connected to a particular domain. Through this information it can be determined if a computer works as an e-mail server or what the domain´s respective name servers are called.
The root name server or simply known as the root server can be imagined as the brain of the domain name system. Every device that is connected to the internet gets assigned a certain name server which translates domain names like blog.1and1.co.uk into IP addresses. If a name server has no information about a queried TLD, it forwards this request to a superior root server. According to this work flow the responsible name server for the TLD is eventually determined. This workflow system is the centerpiece of internet communication and contains the domain names and IP addresses of all name servers of the various TLD’s. In total, there are 13 root servers with different operators which are centrally coordinated by the ICANN.
The root zone is the top-level DNS zone in the hierarchical namespace of the Domain Name System. This zone is essential for the function of the internet and defines the address area of the domain tree in the domain name system for which a name server (NS) is responsible. The root zone contains more than 1500 gTLDs, ccTLDs and IDNs, that are transmitted to the root server database.
The “uniform resource locator” is mainly used to access websites. By typing in the URL the browser knows which site to search for and then open. Apart from just bringing up websites (http) a URL can also call data servers (ftp), emails (mailto) or files (file).
When accessing the internet every computer gets an IP address that is completely unique. This 32 bit number is built in a certain pattern and can have a value range between 0 and 255. There are two different IP addresses, static and dynamic. An IP address that is fixed to a certain domain is called a static IP address. When a computer gets a new IP address every time it enters the internet this is called a dynamic IP address. Every domain gets a unique IP, because as well as a domain name, an IP address must not occur twice. In order to avoid two or more IP addresses conflicting through repetition, all IP assignments are coordinated by the ICANN.
For a domain to always be available a lot of DNS entries are required. These entries are divided into four sections. The first one contains the domain name and the second one the protocol type (e.g. IN = internet). The third section the entry type is defined and the last section contains the value of the entry, e.g. the IP address. Next, we will show you the single entry types which are referred to as ‘records’.
The A record deposits the IPv4 address under which the domain is located. They are the most important forms of the DNS entries and are used for assigning a webserver to a domain in order for the domain to be reachable via a web browser.
Similar to the A record, the major difference being that the domain is assigned to an IPv6 address.
With a CNAME record (Canonical Name Resource Records) a domain can refer to another domain. It therefore contains an alias for a domain if other names are assigned.
MX stands for “mail exchange” which means the MX entries define the mail server that is responsible for the domain. Usually two mail servers are entered for one domain. If the first server is not reachable it is automatically rerouted to deliver the e-mail to the second server. The mail servers don´t have to be identical to the server where the respective web space is located. However, MX entries have to directly refer to A or AAAA entries because CNAME entries are not always reliable.
An NS record (Name Server Resource Record) is a DNS server´s data set. Firstly, it defines which name server is responsible for which zone. Secondly, it connects the single zones to the workflow delegation zone tree.
Pointer Resource Records assign one or more host names to a certain IP address in the DNS. Host names are explicit terms for a single computer in a network.
Service Resource Records it can be defined via the DNS which IP-based services can be offered under the domain or subdomain help to define via the DNS which IP-based services can be offered under the domain or subdomain. They are often used for XMPP, SIP or LDAP protocols as well as Microsoft Office 365.
The Text Resource Record enables the server to file definable text in a DNS zone.
The section TTL (Time To Live) is part of the DNS record types and shows how long (in seconds) the specific information is valid. If the time is up, a fresh query is required. With this the providers´ DNS servers decide how long data sets are kept in the cache.
Take a look at this article to find out more about Top Level Domain, Second Level Domain and co.
In part 3 you will get to know what is behind the terms Domain Name Registry, Registrar and Whois.