TCP/IP Tutorial and Technical Overview - IBM Redbooks

1.2.2 NSFNET
NSFNET, the National Science Foundation (NSF) Network, is a three-level
internetwork in the United States consisting of:
► The backbone: A network that connects separately administered and
operated mid-level networks and NSF-funded supercomputer centers. The
backbone also has transcontinental links to other networks such as EBONE,
the European IP backbone network.
► Mid-level networks: Three kinds of networks (regional, discipline-based, and
supercomputer consortium networks).
► Campus networks: Whether academic or commercial, connected to the
mid-level networks.
Over the years, the NSF upgraded its backbone to meet the increasing demands
of its clients:
► First backbone: Originally established by the NSF as a communications
network for researchers and scientists to access the NSF supercomputers,
the first NSFNET backbone used six DEC LSI/11 microcomputers as packet
switches, interconnected by 56 Kbps leased lines. A primary interconnection
between the NSFNET backbone and the ARPANET existed at Carnegie
Mellon, which allowed routing of datagrams between users connected to each
of those networks.
► Second backbone: The need for a new backbone appeared in 1987, when the
first one became overloaded within a few months (estimated growth at that
time was 100% per year). The NSF and MERIT, Inc., a computer network
consortium of eight state-supported universities in Michigan, agreed to
develop and manage a new, higher-speed backbone with greater
transmission and switching capacities. To manage it, they defined the
Information Services (IS), which is comprised of an Information Center and a
Technical Support Group. The Information Center is responsible for
information dissemination, information resource management, and electronic
communication. The Technical Support Group provides support directly to the
field. The purpose of this is to provide an integrated information system with
easy-to-use-and-manage interfaces accessible from any point in the network
supported by a full set of training services.
Merit and NSF conducted this project in partnership with IBM and MCI. IBM
provided the software, packet-switching, and network-management
equipment, while MCI provided the long-distance transport facilities. Installed
in 1988, the new network initially used 448 Kbps leased circuits to
interconnect 13 nodal switching systems (NSSs), supplied by IBM. Each NSS
was composed of nine IBM RISC systems (running an IBM version of 4.3BSD
UNIX) loosely coupled by two IBM token-ring networks (for redundancy). One
Chapter 1. Architecture, history, standards, and trends 15