In characterizing network performance, Stallings defines a symbol ‘ a’, exactly as in Ref. Third, Abeysundara and Kamal fail to link their choice of the definition of ‘ a’ to any scientific reference. Second and more important, the concept of ‘ a’ fails to reflect the quality of service (QoS) considerations associated with a message communication. While a pioneering work, the effort incurs three limitations. Furthermore, higher the value of ‘ a’, the more high-speed the LAN.
They conclude that as the value of ‘ a’ approaches or even exceeds unity, the LAN may be viewed as operating at high-speeds. They report findings that for a packet size of 200 bits, transmission speed of 2×10 8 m/s, and a link bandwidth of 100 Mb/s, ‘ a’ equals 1.25 and 2.5 for LANs spanning 5000 and 10,000 m, respectively. It is defined as the ratio of the physical propagation delay between a given pair of source and destination points to the packet transmission time, for a representative packet size for LANs.
In characterizing high-speed local area networks (HSLANs), Abeysundara and Kamal compute a quantity, ‘ a’, labeled normalized propagation delay. This, in turn, will help us consider the important issues while designing new network architectures and provide us insight into their ultimate potential.Ī thorough literature search on the fundamental characteristics of high-speed networks revealed sparse results. The exercise will provide valuable understanding of networks, especially the fundamental limitations, if any. Next, utilizing the definition as a reference and recognizing the key functions of a network, one would have to identify the fundamental attributes of networks. Then, for key past and present networks, their high-speed characteristic must be computed to help us trace the evolution in networking from the perspective of their high-speed nature. What has caused this change? In an effort to seek answers, it was reasoned that to identify the inherent, indispensable characteristics of high-speed networks, one must first search for a definition of high-speed networks, one that is mathematical yet simple but, most important, physically intuitive. Of great interest is the fact that although the DoD's Arpanet was heralded as a high-speed network back in the early 1980s, today most users are unhappy with its performance. The most obvious question was, what is a high-speed network? What imparts to a network the label, high-speed? Clearly, a link-optical or twisted pair, that interconnects two ATM nodes at 155.5 Mb/s may not qualify alone as high-speed since one can synthesize it from approximately one hundred T-1 lines, each rated at 1.5 Mb/s and definitely not viewed high-speed. Observations of the enormous complexity of today's networks, their increasing importance and ubiquitous use in the world, the uncontrollable number of diverse dimensions in which networking is expanding, the apparent ad hoc development and deployment of networking techniques, coupled with the intense debate between the superiority of ATM versus IP, had motivated the authors to seek a systematic, logical, and scientific way of understanding the monster that networks have now come to represent. Together with the attributes, the high-speediness promises to serve as a meaningful guide in the design of future high-speed networks, which constitutes the most contribution of this paper. The fundamental attributes represent a holistic view of network, revealing the most important issues and how they are interconnected to each other. The high-speediness factor may also constitute a desirable, target network operating point, which the network provider may choose to sustain during network operation by imposing suitable controls. The paper computes the ‘ s’ values for important past and present networks. In addition to the inherent pedagogical value, high-speediness may be used to classify and compare existing networks. While the definition is mathematical yet physically intuitive, the two observations are due to the laws of physics and imply fundamental limits on networks, and the attributes fall out from a careful analysis of the primary objectives of networks.
This paper represents an effort to develop a simple yet comprehensive understanding of networking through a novel definition-high-speediness, which encapsulates the high-speed nature of networks and is denoted by the symbol ‘ s’, two fundamental observations that underlie every network design, and the identification of the fundamental attributes of networks.
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