The Internet is a world-wide ``network of networks'' that use the TCP/IP (Transmission Control Protocol/Internet Protocol) protocol suite for communications. The Internet was created initially to help foster communication among government-sponsored researchers. Throughout the 1980's, the Internet grew steadily to include educational institutions, government agencies, commercial organizations, and international organizations. In the 1990's, the Internet has undergone phenomenal growth, with connections increasing faster than any other network ever created (including the telephone network). Many millions of users are now connected to the Internet, with roughly half being business users [Cerf93]. The Internet is being used as the basis for the National Information Infrastructure (NII).