ere invented, many corporations and organizations had already pushed the state-of-the-art connectivity toward VPNs. The need stemmed originally from a traditional precaution and demand for solid business privacy. However, it has evolved since the 1990s with the arrival of 58. Uyless Black, Multiprotocol Label Switching (Upper-Saddle River, New Jersey: Prentice-Hall, 2000). 59. Bruce Davie and Yakov Rekhter, MPLS: Technology and Applications (San Francisco: Morgan Kaufmann Publishers, 2000). 60. Peter Tomsu and Gerhard Wieser, MPLS-Based VPNs: Designing Advanced Virtual Networks (Upper Saddle River, New Jersey: Prentice-Hall, 2002). 61. Peter Tomsu and Christian Schmutzer, Next Generation Optical Networks: The Convergence of IP Intelligence and Optical Technologies (Upper-Saddle River, New Jersey: Prentice-Hall, 2002). 62. Uyless D. Black, Optical Networks: Third Generation Transport Systems (Upper-Saddle River, New Jersey: Prentice-Hall, 2002). Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. THE EVOLUTION OF NETWORK TECHNOLOGY: DISTRIBUTED COMPUTING AND THE CONVERGENCE OF NETWORKS 26 NETWORK PROCESSORS sophisticated hacking techniques and well-publicized cyberattacks employed by malicious intruders or eavesdroppers. Today intranets refer to closed-access private networks or networks designed to be inaccessible to unauthorized outsiders. In the 1980s, when corporations would lease X.25 lines from carriers, it was widely believed that these lines ensured that no other traffic could run on those lines simultaneously. Numerous cases (not in the United States, but almost invariably overseas) proved the contrary. Other people's traffic could run on the same physical lines and bandwidth slots that some- one else was paying for. In the mid-1990s, secure communications companies designed layer 2 frame encryptors, which ensured that secure tunnels wer