ITG provides master user domains (first-tier) that are used by a specific set of sites. The name and size of these master user domains are determined by geographic limitations, network topology, and the number of accounts to be supported. The PDC for the master user domains for Redmond, NorthAmerica, and SouthAmerica, are located in Redmond. Others are located near the constituent user population where local data centers provide administrator resources. A BDC for the master user domain is located at each respective remote site for authentication of accounts at that site.
The European master user domain PDCs are physically located in England, with a BDC for the appropriate European master user domain located in each respective European site.
A BDC for the global master user domain is also physically located at each network hub site worldwide.
Microsoft maintains two domains that, due to business security reasons, have restricted access to or from the other domains.
On the Microsoft corporate network, TCP/IP is used by Windows NT Server to forward authentication requests between domain controllers across a WAN. Every server in the master user domain can process logon requests from the domain's user accounts.
Every server in the corporate domain model runs TCP/IP. Adding DHCP to Microsoft's network has significantly reduced administrative overhead for WAN management because individual machine TCP/IP addresses are configured automatically by DHCP.