# Hostname

A hostname is a unique name for a computer or network node in a network. Hostnames are specific names or character strings that refer to a host and make it usable for the network and people. They can describe both physical addresses and network nodes, which have multiple domains under one host. The same gets applies to the world wide web, where hostnames are resolved into IP addresses via the domain name system, so that each network user gets a one-to-one description, regardless of whether it is a computer, a network node at the Internet provider or a web server.

This makes the administration of network services possible, as well as the use of the network by end users. The host name or name of a host is used by the system administrator for administrative purposes. It can utilize different system services with the hostnames. If the hostname is resolved via the domain name system, end users can also access it without knowing the hostname.

http://www.example.com
http:// in the URL corresponds to the network protocol used. This is followed by
http://www.example.com
which is called hostname. The domain name example.com consists of the domain and the top-level domain and should be distinguished from the hostname, even if both versions direct to the same address.

## General information

Hostnames are between IP addresses and domain names in the Internet architecture and had a relay function which was partially replaced by DNS. Historically, hostnames were a name resolution for IP addresses. The IP address of the system (for example, 127.0.0.1) and the hostname for the local address can usually still be found in the root directory of a computer. If the domain server is not reachable, the name resolution can nevertheless be handled with the host name. In this context, the hostname is a virtual network interface that receives and transmits data. If the hostname is complete, it is also referred to as a Fully-Qualified Hostname (FQHN).

However, with the development of the global Internet, the possibilities of this assignment quickly became impractical, since IP addresses are not memorable and new websites, web servers, and computers are constantly being added. For this reason, the Domain Name System (DNS) was introduced which handles the name resolution of domain names to IP addresses. Hostnames are often confused with domains.[1] However, different hosts can be grouped under one domain, similar to subdomains. Hostnames can also coincide with domain names, but don’t have to. In the network architecture, hostnames are still often used to distinguish clients from each other. For example, when creating content for domains, because content is simulated to be on the web, even though it is only stored locally.[2]

• Hostnames assign names for computers, web servers, or interfaces to the respective IP addresses so that the hosts can be addressed without knowledge of IP addresses.
• The domain name system resolves IP addresses (and thus also hostnames) in such a way that human users can find these computers, network nodes or interfaces.

## How it works

The domain name system is intended to simplify the use of the Internet for humans. However, the computers involved communicate in different ways by exchanging data between IP addresses. However, the role of a network interface in a system is not accessible through an IP address. Therefore, hostnames are assigned to be able to find the interface and this is usually specified in the host file or the localhost.

Different services in a network, such as a mail server or data transfer protocols such as FTP, use hostnames to assign the roles in a network, thereby enabling the communication of network users. The participating computers or interfaces know their roles in the system through hostnames and can be addressed.

## Guidelines on hostnames

Depending on the network protocol and network type used, hostnames must meet different requirements to meet international standards.

• Private networks: The hostnames can be assigned relatively freely in an intranet, VPN or LAN. You merely have to observe the restrictions of the protocol used. The same protocols are often used, as is the case with the WWW, i.e. TCP / IP and HTTP, for example. Depending on the network, other protocols may be relevant. For example, RC 5321 is used when transferring emails and the RFC 5966 protocol is used for data transport via TCP. Domain names can usually be omitted in private networks.
• Public networks: In the world wide web, hostnames are also restricted to Internet protocols. Protocol RFC1123, which replaced the document RFC 953 as early as 1989, should be mentioned here. For publicly accessible computers on a network, hostnames are usually listed as fully qualified domain names (FQDNs), which allows direct resolution to an IP address.[3]

Hostnames may use characters from the ASCII character set and start with a letter or number. This means that all characters between a to z, A to Z, 0 - 9 and the hyphen symbol can be used. Hostnames are separated by periods. Whatever is between the periods is called a label. Each label must contain at least 1 character and a maximum of up to 63 characters. No label can start or stop with a hypen. In general, a hostname can be a maximum of 255 characters.[4] The hostname usually indicates the use of the network instance if it does not coincide with or is part of a domain name.

## Examples of hostnames

Hostnames can represent physical or virtual addresses. Some examples:

• The domain name mydomain.com gets assigned the hostname server1.mydomain.com, so that the server is reachable.
• The hostname x3e4585ed.dyn.telefonica.de denotes a network node with an Internet service provider, which has a completely different domain name.
• The hostname mail. can be selected as the name for an internal e-mail server in a private network. The same applies to FTP services and virtual networks.

## Relevance to online marketing

Hostnames are relevant to online marketing, since they are usually part of a domain name. For example, many sites on the Internet can be accessed with or without the www. prefix, since both hosts direct to the same page or domain. A catchy hostname can be an advantage for end users as well. From the point of view of internal technical infrastructure, differentiated hostnames are recommended, for example, if different services are to communicate with one another, as is the case with email servers or FTP transfers of files.

## References

1. What is the difference between a hostname and a domain name support.suso.com. Accessed on 05/30/2016
2. Reserved Top Level DNS Names tools.ietf.org. Accessed on 05/30/2016
3. HTTP State Management Mechanism tools.ietf.org. Accessed on 05/30/2016
4. Requirements for Internet Hosts -- Application and Support tools.ietf.org. Accessed on 05/30/2016