• Within a computer network domain, a domain controller (DC) is a server computer that responds to security authentication requests. It authenticates users, saves account information, and enforces a domain's security policy.
• An extra domain controller (ADC) is a domain controller that exists in a given environment (DC, CDC, and GCDC). It functions similarly to a backup Domain Controller in that if the primary Domain Controller fails, the Additional Domain Controller (ADC) will assist in maintaining network stability.
• DC (Domain controller) has the following operational roles:
• Master Schema for Domain Naming Infrastructure Master RID Master PDC Emulator Master RID Master RID Master RID Master RID Master RID Master RID Master
• The ADC (Additional Domain Controller) has the following operational roles:
• RID Master Infrastructure Master PDC Emulator

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