What is a Top-Level Domain

The modern internet originated from the military and scientific ARPA-Net, where various institutions from both sectors joined forces. Initially, individual computers within this network could only communicate with each other through their numerical IP addresses, until the first Top-Level-Domain (TLD) .com went live on 15th March 1985.

Since then, it has been possible to use a simple combination of name.TLD instead of direct IP addresses to access a website. Over the years, the structure has been expanded to include numerous Top-Level-Domains like the .de Domain, which are assigned to different purposes or regions.

How do Top-Level-Domains and name resolution work on the internet?

In the original ARPA-Net, names had to be locally stored and assigned to specific IP addresses. As the global network expanded, this approach proved to be too complicated and storage-intensive, leading to the introduction of Nameservers (DNS) in the mid-80s to take over this task. Each Top-Level-Domain is now managed by a multitude of DNS servers, each typically responsible for a single TLD extension like the .de Domain.

To resolve an address, a computer contacts a global DNS server, which informs it of the relevant instance - in this case, the one for the .de Domain. The browser then queries the underlying DNS for the IP address corresponding to the name of the .de Domain. Information about name resolution is exchanged and updated at specific intervals by the servers involved, and is always stored in multiple locations to provide an alternative route in case of a node failure.

What are the different types of Top-Level-Domains?

Originally, the top-level domain registry ICANN only established a few purpose-specific TLDs like .com for businesses, .org for organisations, .gov for US government entities, .mil for military institutions, or .net for general purposes. Due to the increasing demand for unique addresses, alongside these TLDs, country-code top-level domains such as .fr (France) or the .de domain were set up a few years later. Currently, there are 200 of these different ccTLDs, for which each country can establish its own registration requirements. Some are therefore used for completely different purposes unrelated to the region - for example, the island nation of Tuvalu markets its .tv top-level domain worldwide for broadcasting services.

After even country-specific extensions like the .de domain proved insufficient to meet the ever-growing demand for unique domain names, the responsible body ICANN liberalised its guidelines for Sponsored Top-Level Domains (sTLD) in 2008. Since then, providers can utilise a variety of new TLDs, including for example:

• .mobi - for mobile content on various devices
• .shop - online stores
• .movie - film industry and TV productions
• .delivery - shipping providers, courier services, and restaurants
• .restaurant - eateries, restaurants, and delivery services
• .energy - companies in the energy sector
• .marketing - agencies for advertising or PR campaigns
• .online - general content
• .berlin - businesses and content in and around the capital city

Overall, there are several hundred of these Sponsored Top-Level Domains. They are managed under license by independent institutions or bodies for about a decade, provided the applicant meets all necessary criteria and pays a fee. The licensee is then responsible for allocating domain names and can establish their own criteria and prices for this purpose.

Do individual top-level domains have specific requirements or restrictions?

The top registration authority ICANN only manages a few top-level domains such as .org, .com, or .net itself. All other TLDs, including the .de domain, are managed by independent entities that either pursue commercial or public interests. Each can set its own rules and fees for registration and is largely independent in its criteria. Therefore, there is no uniform and binding regulation or pricing structure, and it is up to the user to inform themselves about any restrictions. They can be broadly classified into different categories:

• Few restrictions: Free use for commercial or private purposes and low fees. Examples: .com, .net, .info, .online
• Country code top-level domain: TLDs like the .ch or .de domain can be used universally but are subject to the regulations of the respective country. Many of them - including the .de domain - require a residence (or legal representative) within the country. However, some providers offer a trustee service for this purpose.
• Industry-specific domain: Some domains like .aero are reserved for companies in a specific industry and require proof of a company's activity.
• Commercial TLD: Certain countries like Montenegro (.me), the Kingdom of Tonga (.to), or Tuvalu (.tv) market their ccTLDs. They are universally usable and offer high discretion, but come with corresponding costs.
• Regional top-level domain: Local TLDs like .berlin are usually in a mid-range cost field. They are often reserved for companies and information from a region, positioned in the mid-price range, and may refuse registrations without a local connection.

Are new top-level domains being made available?

The Sponsored TLDs are added at irregular intervals when a competitor applies for a new sTLD and can demonstrate the necessary requirements such as managing a suitable IT infrastructure. They can be registered from the date of their release, with the exact process and conditions depending on the managing institution. The number of available TLDs is steadily increasing, and is now so extensive that most interested parties can be assigned their desired domain name with one or more new TLDs.

Photo: JanBaby