Now that we understand CONS, we can look at CLNS. IP is a CLNS. The apocryphal story, as is oft repeated, is that IP was designed during the height of the Cold War. The military (funded by ARPANET) wanted a bomb-proof network one in which any of the lines or packet switches could be knocked out at any time and not seriously affect network operation. Therefore, the designers chose a dynamically routed CLNS. The philosophical differences between a CLNS and CONS are large, but each is a valid way to construct a network. The Internet has grown to become a high-volume worldwide network. Even some of the original designers are amazed at its capability to continue to grow yet maintain its robustness. More than a few doubters have been predicting Internet meltdown. Congestion has occurred due to lack of bandwidth connecting routers. Adding more bandwidth has so far alleviated this condition. There was some discussion in the late 1990s that the demand for bandwidth would exceed the supply in the year 2001. The technology breakthrough of dense wave division multiplexing (DWDM discussed in Chapter 31) essentially solved the bandwidth problem. The solution isn't inexpensive per se, but it yields tremendous bandwidth for the price.

It is now easy to draw a comparison between X.25 and IP. Each IP packet (called a datagram) is a stand-alone entity containing all the information needed to be routed from one end of the network to the other. The...