By Whom Served. Process shall be served
by the sheriff of the county where the
defendant is found, or by his deputy, or by
any citizen of the United States over eighteen
years of age, except that a subpoena may be
served as provided in Rule 45; where the
service of process is made outside of the
United States, after an order of publication,
it may be served either by any citizen of the
United States over eighteen years of age or
by any resident of the country, territory,
colony or province, who is over eighteen
years of age.