A method of managing a domain, a method of extending a domain, and a method of selecting a reference point controller are provided. The method of operating the domain includes: receiving a request for authenticating a reference point controller from a reference point controller candidate; invalidating a membership of the stored reference point controller; generating a unique reference point controller membership for verifying that the reference point controller candidate is a new reference point controller; and transmitting the generated reference point controller membership to the reference point controller candidate. Accordingly, even when an error occurs in the reference point controller, the function of the reference point controller can be rapidly replaced by using the reference point controller candidate.