The simple model on which the Internet has operated, with allpackets treated equally, and charges only for access links to thenetwork, has contributed to its explosive growth. However, there iswide dissatisfaction with the delays and losses in currenttransmission. Further, new services, such as packet telephony,require assurance of considerably better service. These factors havestimulated the development of methods for providing Quality ofService (QoS), and this will make the Internet more complicated.Differential quality will also force differential pricing, and thiswill further increase the complexity of the system. The solution ofsimply putting in more capacity is widely regarded as impractical.However, it appears that we are about to enter a period of rapidlydeclining transmission costs. The implications of such an environmentaxe explored by considering models with two types of demands for datatransport, differing in sensitivity to congestion. Three networkconfigurations are considered f (1) with separate networks for thetwo types of traffic, (2) with a single network that providesuniformly high QoS, and (3) with a single physical network thatprovides differential QoS. The best solution depends on theassumptions made about demand and technological progress. However, weshow that the provision of uniformly high QoS to all traffic may wellbe best in the long run. Even when it is not the least expensive, theadditional costs it imposes are usually not large. In a dynamicenvironment of rapid growth in traffic and decreasing prices, thesecosts may well be worth paying to attain the simplicity of a singlenetwork that treats all packets equally and has a simple chargingmechanism.
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