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NSFNET (National Science Foundation NETwork) was founded in 1985 by the National Science Foundation to link its supercomputer centers, and to provide access to the Internet. NSFNET is a high-speed backbone network consisting of point-to-point links in a mesh configuration. The network was fully deployed in 1988, initially at 56 Kbps. In 1986, NSFNET partially funded a number of regional networks, tying into the backbone. In 1992 the backbone was upgraded to T3, operating at 45 Mbps. More recently, major portions were upgraded to OC-3 (155 Mbps) and beyond.
The physical topology of the Internet, ultimately, is not really all that important. However, and for those of you (like the author) who absolutely must know at some level, it consists of leased-lines that connect various major computing center in a partially-meshes network for purposes of redundancy and network resiliency. Initially, ARPANET consisted of approximately 50 BBN Packet Switching Nodes (PSNs), that were custom-built and scattered around the United States and Western Europe. NSFNET (1985) consisted of 56-Kbps leased-line circuits connecting the SFC supercomputer centers in San Diego; Boulder, CO; Champaign, IL; Pittsburgh; Ithaca, NY; and Princeton, NJ.
The original NSFNET was replaced (1988) by an expanded version through a partnership of MERIT (statewide network run by the University of Michigan), IBM, and MCI. Sites were added at San Francisco; Seattle, Houston, and Ann Arbor, MI and other cities where there resided large computer centers. The third version of the NSFNET backbone was deployed in 1989, increasing backbone speed, and adding some circuits while deleting others. In 1996, NSFNET was officially retired and replaced with the MERIT Network (Figure 13.2). That network consists of NAPs (Network Access Points) in San Francisco, (Pacific Bell), Chicago (Ameritech) and New Jersey (Sprint), as well as Merit Access Exchanges in San Francisco (MAE West) and Washington, D.C. (MAE East) provided by MFS Datanet.
Figure 13.2 MERIT backbone network.
Aside from the backbone network, NSFNET funded a number of mid-level networks at the state and regional levels. Access networks also have been funded in various networks to support backbone connections for specific organizations or consortia. Campus networks also connect to the backbone through dedicated lines leased from various carriers [13-2]. In an interesting recent development, universities have become distressed over the degradation in Internet performance as traffic levels have increased. In fact, a number of them have petitioned the National Science Foundation to build a new, separate NSFNET intranet (private Internet) just for themseems as though success does come at a price [13-3]. Figure 13.3 shows a view of CERFnet, one of numerous backbone networks providing commercially available access to the NAPs and MAEs.
Figure 13.3 CERFnet National T3 Topology Map of August 1, 1996. (Reprinted with permission of CERFnet.)
The Internet is a most unusual network. Virtually any entity can connect to the Internet to offer resources or to access them. Virtually any type of information can transverse the Net, and without interference. There is no central authority that regulates the Internet, although there are organizations that set certain fundamental standards and guide its operation. The Internet, by design, is autonomous and even anarchistic. That fact is both a strength and a weakness of the Net.
There do exist a number of organizations which are involved in various Internet administrative and support activities. These organizations include the GSI, IAB, IETF, IESG, IRTF, and The Internet Society (also known as ISOC).
The Internet Architecture Board (IAB) (nee Internet Activities Board) is a voluntary board comprising 12 expert individuals who use the resources of their sponsoring companies to further the interests of the Internet [13-4]. The IAB supervises the activities of two task forces, the IETF and the IRTF. In combination, those organizations set policy and direction.
The Internet Engineering Task Force (IETF) identifies, prioritizes and addresses short-term issues and problems, including protocols, architecture and operations. Proposed standards are published on the Internet in the form of RFCs (Requests for Comment). Once the final draft of a standard is prepared, it is submitted to the Internet Engineering Steering Group (IESG) for approval. The IETF recently formed a task force, the IPng (IP next generation) to address the future of the Internet, including expansion of IP addresses and determination of functionality and feature content.
The Internet Research Task Force (IRTF) deals with long-term issues, including addressing schemes and technologies [13-5].
The Internet Assigned Numbers Authority (IANA) assigns IP addresses to organizations desiring to place computers on the Internet, with the number of addresses depending on the size of the organization. Class C addresses support up to 256 (28) individual machines, Class B addresses support up to 65,536 (216) machines, and Class A address support as many as 16,777,216 (217) machines.
The organization assigned the numbers then can reassign them on the basis of either static or dynamic addressing. Static addressing involves the permanent association of an IP address with a specific machine. Dynamic addressing assigns an available IP address to the machine each time a connection is established. For instance, an Internet Service Provider (ISP) will assign an IP address to a user machine each time the user accesses the ISP to seek connection to the Net. Once the connection is terminated, that IP address becomes available to other users [13-6].
Interestingly, Sprint has blocked Internet traffic to users of Class C ISPs with assigned IP addresses longer than 18 bits. Sprint claims that the lengthy addresses have caused router tables to overflow, affecting its capability to handle Net traffic in general. As one might imagine, the Class C ISPs have protested Sprints action, as it has the same effect of blocking access to a telephone if the authorized telephone number is too long. At the time of this writing, other carriers have declined to take such action, preferring to consider backbone router upgrade options.
The Internet Society (ISOC) is a voluntary organization that acts to lend some formal structure to the administration of the Net. The Internet Society has granted the IESG formal authority to make decisions on standards.
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