Network And Internet Connections

The Internet is a network of networks that interconnects computers around the
world, supporting both business and residential users. In 1994, a multimedia
Internet application known as the World Wide Web became popular. The higher
bandwidth needs of this application have highlighted the limited Internet access
speeds available to residential users. Even at 28.8 Kilobits per second
(Kbps)the fastest residential access commonly available at the time of this
writingthe transfer of graphical images can be frustratingly slow. This
report examines two enhancements to existing residential communications
infrastructure: Integrated Services Digital Network (ISDN), and cable television
networks upgraded to pass bi-directional digital traffic (Cable Modems). It
analyzes the potential of each enhancement to deliver Internet access to
residential users. It validates the hypothesis that upgraded cable networks can
deliver residential Internet access more cost-effectively, while offering a
broader range of services. The research for this report consisted of case
studies of two commercial deployments of residential Internet access, each
introduced in the spring of 1994: Continental Cablevision and Performance
Systems International (PSI) jointly developed PSICable, an Internet access
service deployed over upgraded cable plant in Cambridge, Massachusetts;
Internex, Inc. began selling Internet access over ISDN telephone circuits
available from Pacific Bell. Internex’s customers are residences and small
businesses in the “Silicon Valley” area south of San Francisco,
California. 2.0 The Internet When a home is connected to the Internet,
residential communications infrastructure serves as the “last mile” of
the connection between the home computer and the rest of the computers on the
Internet. This section describes the Internet technology involved in that
connection. This section does not discuss other aspects of Internet technology
in detail; that is well done elsewhere. Rather, it focuses on the services that
need to be provided for home computer users to connect to the Internet. 2.1 ISDN
and upgraded cable networks will each provide different functionality (e.g. type
and speed of access) and cost profiles for Internet connections. It might seem
simple enough to figure out which option can provide the needed level of service
for the least cost, and declare that option “better.” A key problem
with this approach is that it is difficult to define exactly the needed level of
service for an Internet connection. The requirements depend on the applications
being run over the connection, but these applications are constantly changing.

As a result, so are the costs of meeting the applications’ requirements. Until
about twenty years ago, human conversation was by far the dominant application
running on the telephone network. The network was consequently optimized to
provide the type and quality of service needed for conversation. Telephone
traffic engineers measured aggregate statistical conversational patterns and
sized telephone networks accordingly. Telephony’s well-defined and stable
service requirements are reflected in the “3-3-3” rule of thumb relied
on by traffic engineers: the average voice call lasts three minutes, the user
makes an average of three call attempts during the peak busy hour, and the call
travels over a bidirectional 3 KHz channel. In contrast, data communications are
far more difficult to characterize. Data transmissions are generated by computer
applications. Not only do existing applications change frequently (e.g. because
of software upgrades), but entirely new categoriessuch as Web browserscome
into being quickly, adding different levels and patterns of load to existing
networks. Researchers can barely measure these patterns as quickly as they are
generated, let alone plan future network capacity based on them. The one
generalization that does emerge from studies of both local and wide- area data
traffic over the years is that computer traffic is bursty. It does not flow in
constant streams; rather, “the level of traffic varies widely over almost
any measurement time scale” (Fowler and Leland, 1991). Dynamic bandwidth
allocations are therefore preferred for data traffic, since static allocations
waste unused resources and limit the flexibility to absorb bursts of traffic.

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This requirement addresses traffic patterns, but it says nothing about the
absolute level of load. How can we evaluate a system when we never know how much
capacity is enough? In the personal computing industry, this problem is solved
by defining “enough” to be “however much I can afford
today,” and relying on continuous price-performance improvements in digital
technology to increase that level in the near future. Since both of the
infrastructure upgrade options rely heavily on digital technology, another
criteria for evaluation is the extent to which rapidly advancing technology can
be immediately reflected in improved service offerings. Cable networks satisfy
these evaluation criteria more effectively than telephone networks because:
Coaxial cable is a higher quality transmission medium than twisted copper wire


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