Congress adopted a functional approach in defining a fiduciary. Fiduciary duties apply to any person who acts or has the authority to act in the manner or as to the matters described in ERISA. A person is a fiduciary of any employee benefit plan to the extent that the person exercises discretionary authority or control respecting management of such plan or management or disposition of its assets, renders or has authority or responsibility to render investment advice for a fee, or has discretionary authority or responsibility in the administration of such plan. Neither title nor office controls the legal designation of fiduciary. But, some positions, such as plan administrator or trustee, may require any person who holds them to perform defined fiduciary functions and thereby undertake fiduciary status.