Domain name

A domain ( from English- domain [ də ( ʊ ) meɪn ] area ',' domain ') is a contiguous portion of the hierarchical Domain Name System (DNS). In the domain allocation method, it is an on the internet globally unique and unambiguous and under certain rules freely selectable name below a top-level domain. The exact rules for naming sets, the contracting authority (NIC = Network Information Center ) of each top-level domain fixed. A domain can be divided up into separate subdomains by dots. Each thus formed fully qualified domain name (FQDN = Fully Qualified Domain Name ) any physical or virtual object can be uniquely addressed worldwide. The connection between the FQDN and the actual location of the object is established via entries in name servers, which ultimately point to the IP address of a server.

• 3.1 Structure and function
• 3.2 Advantages of subdomains 3.2.1 Logical Structure
• 3.2.2 Distributed management with subdomains

The DNS namespace

Structure and rules

The representation of the DNS name space is done as " root tree". Each node of this tree has a name that is not unique without specifying a full name. Thus, for example, the node example not uniquely determined, because this name could be associated with the one under example.com and example.net to the other under.

Every domain name thus consists of several parts of names (labels ) separated by periods.

The name rightmost is at its highest in the hierarchy of the rooted tree, the leftmost node name the lowest. The highest level in the DNS hierarchy has thereby called the root domain (or zero or root label called ). She has, by definition, an empty node names consisting of a single octet with zeros.

Topologically below, and thus left image of the root domain, followed by the name of a top-level domain ( TLD). Below or on behalf left of the top-level domain follow the names of second- level domains, followed by third-level domains or subdomains simple.

Example

(root) label the 0th level, zero - Label           / \          / \        com org labels of the first level, top level domains (TLD )        / \       / \   example example labels the second level, second- level domains      | / | \ And host names directly under a TLD     www en www labels of the 3rd level, third-level domains              / \ And host names under second- level domains           foo bar ( expandable ) Fully Qualified Domain Name ( FQDN)

The full name of a domain is referred to as its Fully Qualified Domain Name ( FQDN). The domain name is an absolute address in this case.

The FQDN www.example.com. is given by:

3rd-level label. 2nd-level label. Top -level domain. root label and is thus

Www. example. com. Since the root label is always empty ( it only consists of an empty string), will in most user applications (eg browsers) usually on the input of the point between the label of the top-level domain and the root label omitted. Strictly speaking, at this writing no longer an absolute, but a relative address and therefore no longer an FQDN. When specifying in resource records on name servers, the full name must be specified with point compelling.

As a generic term for FQDN and IP address of the term fully-qualified host name ( FQHN ) is used in some RFCs.

Subdomain

Design and function

As a subdomain is called a domain, which is located in the hierarchy below the other. In common parlance, are therefore usually meant Domains in the third or another level. A domain that is located directly below the top- level domain, is colloquially referred to not as a subdomain, but as a second- level domain, or only as a domain.

For example, consider the "top level domains " com and org. Among these domains are the sub - or second- level domains example.com and example.org settled. Each subdomain is again independent domain, may lie in the different domains and host names. For example, example.org is a subdomain of the top -level domain org or de.example.org a subdomain of example.org.

In some top -level domains, there is a restriction of second- level domains: for example, is under uk only a handful of domains such as ac.uk, gov.uk, co.uk settled. Universities receive third-level domains under ac.uk, authorities gov.uk, commercial companies under co.uk. In Austria, a mixed system is used: second -level domains under at be freely assigned, under ac.at receive only universities and authorities gv.at only a third-level domain.

For logical and physical separation of services within the domain of an organization are traditionally sub-domains, eg www.beispiel.at for the Web server or mail.beispiel.at for the mail server. But this is just a convention; a web server might as well web.beispiel.at on a computer with the domain name or operated beispiel.at.

Conventional names for various services:

• Web: www.
• Web server specifically for mobile devices: m.
• FTP server: ftp.

Benefits of subdomains

Logical structure

The logical structure is used for example for distributed branches or departments of a company to conduct for independent web appearances, languages ​​or by e-mail to branches with their own mail server.

On the other hand, one can also create subdomains in order to forward to specific departments and divisions within a company or organization. Examples of a subdomain for forwarding to individual areas or locations of a company and / or organization:

Bremen.example.com hamburg.example.com personal.example.com lieferanten.example.com Since you can specify redirections, you can with the subdomain to or forward and to specific areas of the existing domain. The additional setting of subdomains you can increase so under certain circumstances, the number of visitors to the page.

Distributed management with subdomains

A subdomain can be managed like any domain to any name servers. Thus, for example de.example.com on a name server in Germany are managed, while example.com is located in the USA (see DNS delegation ).

Some service providers use this opportunity and provide third-level subdomains with forwarding to a longer URI. This has the advantage that unlike second- level domains themselves can set up these and arise only minimal costs for the provider. Popular subdomains for German sites are subdomain.de.TLD with different top- level domains.

Special cases

Some countries, such as Turkey, Australia or the UK, exclusively awarded Third - level domains. Thus, a registry of [example ]. Uk or [ example]. Tr not possible, instead domains such as [ example] co.uk offered. . See also: Top- level domain

The domain name example.com, example.net and example.org are reserved by IANA, so you can use them in their own documentation and test environments. The purpose of this book is to avoid conflicts with real existing domain names. To this end, localhost were also the top - level domains. Tested. Example. Disabled and. Reserved. All reserved names are defined in RFC 2606.

Legal nature of domain names

The legal nature of. De domains has been strengthened over the years, including through the judgments of the Federal Constitutional Court, the Bundesgerichtshof ( domain seizure ) and the Federal Fiscal ( Tax Deduction ). It is assumed that a. De domain is not an absolute right but a contractual claim against the registry, DENIC, focused on the use of the domain. This is a. De domain, a legally protected asset, similar to " legitimate possession of a thing," and therefore " property -like". When a seizure. De domain DENIC eG is by the competent Regional Court Frankfurt am Main considers proper garnishee.

The European Court of Human Rights (ECHR ) ruled in a judgment of 18 September 2007:

This is clarified for Europe that at one domain ownership pursuant to Article 17, Section 1 of GRC, the Charter of Fundamental Rights of the European Union, there is.