Although IP addressing is not especially complex, it is easier for users to work with host names rather than with the IPv4 or IPv6 addresses of hosts, such as websites, to which they want to connect. When an application, such as Microsoft Edge, references a website name, the name in the URL is converted into the underlying IPv4 or IPv6 address using a process known as name resolution. Windows 10 and Windows Server 2016 computers can use two types of names. These are:
- Host names: Up to 255 characters in length, contains only alphanumeric characters, periods, and hyphens. A host name is an alias combined with a DNS domain name.For example, the alias computer1, is prefixed to the domain name, Contoso.com, to create the host name, or Fully Qualified Domain Name (FQDN), omputer1.contoso.com.
- NetBIOS name: NetBIOS names use a non hierarchical structure based on a 16-character name. The sixteenth character identifies a particular service running on the computer named by the preceding 15 characters. Thus, LON-SVR1[20h] is the NetBIOS server service on the computer named LON-SVR1.
The method in which a Windows 10 or Windows Server 2016 computer resolves names varies based on its configuration, but it typically works as shown in Figure below.
The following process identifies the typical stages of name resolution for a Windows 10 or Windows Server 2016 computer.
- Determine whether the queried host name is the same as the local host name.
- Search the local DNS resolver cache for the queried host name. The cache is updated when records are successfully resolved. In addition, the content of the local Hosts file is added to the resolver cache.
- Petition a DNS server for the required host name.
Of course, name resolution in Windows Server 2016 does more than just provide for simple name to IP mapping. The DNS server role is also used by computers to locate services within the network infrastructure.
For example, when a computer starts up, the user must sign-in to the Active Directory Domain Services (ADDS) domain and perhaps open Microsoft Office Outlook. This means that the client computer must locate a server that can provide authentication services in the local ADDS site, and furthermore, locate the appropriate Microsoft Exchange mailbox server for the user. These processes require DNS.