The domain name system (DNS) is an internet service that is required because the Internet does not recognize the text-based web address or e-mail address that you type into your Web browser or e-mail application. All or part of a web address or an e-mail address is a domain name, and DNS translates this domain name into an IP address that is recognized by the Internet. Dynamic DNS server – If you are using dynamic IP addressing, Inmarsat recommends that you use a dynamic DNS server. A dynamic DNS server updates the IP address information in the DNS database each time your IP address changes. A dynamic DNS server also enables a computer using a dynamic IP address to use network applications that normally require a static IP address, for example FTP servers. This service requires subscription with a Dynamic DNS provider. Static DNS Server – If you are using static IP addressing, Inmarsat recommends that you use a static DNS server. If you select this option, you must enter the IP address of the primary DNS server. This is supplied by your internet service provider. Optionally, you can enter the IP address of a secondary DNS server, also supplied by your ISP. This is used in the event of failure of the primary DNS server.