ifornia's UNIX implementation, known as 4.2BSD (Berkeley Software Distribution) UNIX. Extension of the original ARPANET continued. In 1986, the National Science Foundation (NSF) built a backbone network to interconnect four NSF supercomputing centers and the National Center for Atmospheric Research. This network, known as NSFNET, was originally intended to serve as a backbone for other networks, not as a stand-alone intercon- nection mechanism. Additionally, the NSF's Appropriate Use Policy lim- ited transported traffic to noncommercial traffic only. NSFNET continued to expand, and eventually became what we know today as the Internet. And while the original NSFNET applications were multi- protocol implementations, TCP/IP was used for overall interconnectivity. In 1994, a structure was put in place to reduce the NSF's overall role in the Internet. The new structure consists of three principal components. The first of these was a small number of network access points (NAPs), where ISPs would interconnect to the Internet backbone. The NSF orig- inally funded four NAPs in Chicago (operated by Ameritech, now part of SBC), New York (really Pensauken, NJ, operated by Sprint), San Fran- cisco (operated by Pacific Bell, now part of SBC), and Washington, D.C. (MAE-East, operated by MFS, now a division of MCI). The second component was the very High-Speed Backbone Network Service, a network that interconnected the NAPs and was operated by MCI. It was installed in 1995 and originally operated at OC-3 (155.52 Mbps) but was upgraded to OC-12 (622.08 Mbps) in 1997. The third component was the routing arbiter, designed to ensure that appropriate routing protocols for the Internet were available and prop- erly deployed. ISPs were given 5 years of diminishing funding to become commer- cially self-sustaining. The funding ended in 1998, and starting at roughly the same time, a significant number of additional NAPs have been launched. As a matter of control and management, three tiers of ISPs have been identified. Tier 1 refers to na