2.2.2 Computer accounts
Each computer account that is created in Active Directory has a relative distinguished name (RDN), a pre-Microsoft Windows® 2000 operating system computer name (SAM account name), a primary DNS suffix, a DNS host name, and a service principal name (SPN) in addition to the computer name. The administrator enters the computer name when creating the computer account. The computer name must include the dollar sign ($) character at the end of the name (for example RedmondDc1$).
When the domain functional level has been set to Windows Server® 2003 operating system, Windows Server® 2003 R2 operating system, Windows Server® 2008 operating system, and Windows Server® 2008 R2 operating system, a new lastLogonTimestamp attribute is used to track the last logon time of a user or computer account. This attribute is replicated in the domain and can provide important information regarding the history of a user or a computer.
Every Microsoft Windows® computer that joins a domain has a computer account.<3> Similar to user accounts, computer accounts provide a means for authenticating and auditing computer access to the network and to domain resources. Each computer account must be unique.
When the Netlogon service running on a client computer connects to the Netlogon service on a domain controller (DC) in order to authenticate a user, the Netlogon services challenge each other to determine whether they both have a valid computer account. This allows a secure communication channel to be established for logon purposes.
In order for a Windows computer to join a domain, the computer must have a computer account in Active Directory.<4>
The computer name (for example RedmondDc1$) is used as the Lightweight Directory Access Protocol (LDAP) relative distinguished name (RDN). Active Directory suggests the pre-Windows 2000 name that uses the first 15 bytes of the RDN. The administrator can change the pre-Windows 2000 name at any time.
The DNS name for a host is called a full computer name and is a DNS fully qualified domain name (FQDN). The full computer name is a concatenation of the computer name (the first 15 bytes of the SAM account name of the computer account without the "$" character) and the primary DNS suffix (the DNS domain name of the domain in which the computer account exists). It is listed on the Computer Name tab in the System Properties dialog box in Control Panel.
By default, the primary DNS suffix portion of the FQDN for a computer must be the same as the name of the Active Directory domain where the computer is located. To allow different primary DNS suffixes, a domain administrator may create a restricted list of allowed suffixes by creating the msDS-AllowedDNSSuffixes attribute in the domain object container. This attribute is created and managed by the domain administrator by using Active Directory Service Interfaces (ADSI) or LDAP.
The SPN is a multivalue attribute. It is usually built from the DNS name of the host. The SPN is used in the process of mutual authentication between the client and the server hosting a particular service. The client finds a computer account based on the SPN of the service to which it is trying to connect. The SPN can be modified by members of the Domain Admins group.