Most significantly, the landscape changed dramatically as consumers flocked to the Internet in the millions. As a result, today's average trunk utilization is miniscule compared to that for the early Internet. Recall how the carriers built out capacity during the Dot Com era, and the desire for spare capacity to deal with flash crowds and the like spurred carriers to richly trunk their networks. Most tier one ISPs ARE carriers, and the circuits come from another department in the same company. Those circuits were enormously expensive and added a layer of overhead. ISPs like BBN, UUNET, PSINet, and ANS leased circuits from carriers. Remember that the Internet was originally built by organizations that were NOT carriers. Furthermore fewer trunks led to less redundancy. In the early days trunks were unreliable compared to today's fiber circuits. The interstate highway model applied because each institutional user's "driveway" was clear but the highways were often congested. Back then congestion occurred most often in the network core at peering/exchange points, or on trunks when a trunk went down (which happened often). Some even had multiple connections for redundancy. In the old days every Internet user was connected via a company, agency, school, or institution with a "good" dedicated connection. In the highway system most congestion occurs on major arteries, while local streets are usually free and clear-but on today's Internet the opposite is true. The reason is that when it comes to traffic congestion and performance for the average Joe consumer Internet user, today's Internet is actually the inverse of the highway system. Although once apt, it is time to stop comparing the Internet to the interstate highway system.
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