Advanced Network Technology Page: 52
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52 1 Advanced Network Technology
ing five testbeds; a sixth testbed, funded by
ARPA alone, was announced in June of 1992.
The testbeds are investigating gigabit net-
works, very high-speed broadband networks that
represent the limit of what can be achieved today.
Most current work on broadband networks is
looking at lower bandwidths, such as the 155
Mb/s rate that will be used for the telephone
companies' B-ISDN service. Because of the focus
on gigabit rates, some aspects of the testbeds'
research agenda are unique. In other respects,
however, the testbeds are one of a number of
research programs whose work will impact the
NREN-fast packet switching technologies, for
example, are being studied as part of many
industry research projects.
RESEARCH OBJECTIVES
In general, the objective of the testbeds is to
speed the deployment of advanced network tech-
nology, in the NREN and elsewhere. The net-
works are designed to provide a realistic test
environment for the technologies outlined in the
previous chapter. The switches and transmission
equipment conform to emerging industry stand-
ards wherever possible. More speculative con-
cepts such as optical switching are not being
investigated by the testbeds-the focus is on the
network technologies that are central to near-term
industry planning. One purpose of the testbeds is
to look at unresolved research questions. How-
ever, the most valuable aspect of the testbeds will
be to demonstrate the feasibility of these networks
and provide experience with their construction.
While much of the research is related to
near-term industry plans, the testbeds are also
looking into the future. The testbed networks
achieve the highest bandwidths possible, given
the constraints of emerging industry standards,
current technology, and the time horizon of the
program. The equipment used in the testbeds had
to be such that it could reasonably be expected to
be working in time to integrate the components
and begin testing the networks by the end of theproject. The applications are the most bandwidth-
intensive possible, "gigabit applications" that
require a full gigabit of bandwidth for each user.
For the most part, these are distributed supercom-
puting applications that use the network to
combine the processing power of multiple super-
computers.
The research is also related to the expected use
of the network technology in the NREN environ-
ment. This emphasizes the use of Internet proto-
cols with the new fast packet switching technolo-
gies, because the NREN program is linked to the
evolution of the Internet. In addition, supercom-
puter-based applications of the type being investi-
gated by the testbeds will play an important role
in the gigabit NREN. However, not all issues
relevant to the future development of the NREN
are addressed by the testbeds: because of the
emphasis on high-speed applications there is little
work being done on applications that will be used
outside the supercomputer community. Nor is
there significant work being done on topics
related to the growing size and complexity of the
Internet (see ch. 2, p. 26, and ch. 5, p. 70).
Given the objective of demonstrating the feasi-
bility of the emerging network design concepts,
the testbeds are emphasizing the construction of
working networks-much of the prior network
research used modeling or simulation in "paper
studies. Because there is little real experience
with broadband networks, these models and
simulations are based on assumed traffic patterns
that may not be accurate. The testbeds are
addressing this problem by building test networks
and investigating both network and applications
research simultaneously. The applications will
provide a source of traffic with which to test the
network components and protocols.
In addition, there is a focus on overall systems
performance. The overall performance of a net-
work depends on how well the individual compo-
nents work together, not solely on the perform-
ance of any single component. In the past,
researchers have tended to focus on the design of
individual components; for example, some have
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United States. Congress. Office of Technology Assessment. Advanced Network Technology, report, June 1993; [Washington D.C.]. (https://digital.library.unt.edu/ark:/67531/metadc40038/m1/56/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.