Company XYZ provides cable television service to several regional areas. They are currently installing fiber-to-the-home in many areas with hopes of also providing telephone and Internet services. The telephone and Internet services portions of the company will each be separate subsidiaries of the parent company. The board of directors wishes to keep the subsidiaries separate from the parent company.

However all three companies must share customer data for the purposes of accounting, billing, and customer authentication. The solution must use open standards, and be simple and seamless for customers, while only sharing minimal data between the companies.

Which of the following solutions is BEST suited for this scenario?