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Broadband Network Access Techniques

Authors -- Saumitra M Das & Freddy Kharoliwala

Abstract:

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 56 Kilobits per second (Kbps) the fastest residential access commonly available at the time of this writing,the transfer of graphical images can be frustratingly slow. This report examines three enhancements to existing residential communications infrastructure: digital local telephone service (ISDN), and cable television networks upgraded to pass bi-directional digital traffic. It analyzes the potential of each enhancement to deliver network access to users. It validates the hypothesis that upgraded cable networks can deliver residential Internet access more cost-effectively, while offering a broader range of services. 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 categories Ńsuch as Web browsers come 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. Dynamic bandwidth allocations are therefore preferred for data traffic, since static allocations waste unused resources and limit the flexibility to absorb bursts of traffic. 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.

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Last Updated : September 03, 1999 09:46:13 AM -0400

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