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By the middle of the 1990s, Intel and Microsoft were so profitable that they accounted for nearly half of the entire profits in the worldwide PC industry (which was worth over $100 billion, each year).
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TCP/IP Commands

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This chapter has discussed some of the practical aspects of networking. As someone who has run a network for many years, I have found that the ping and traceroute commands are invaluable for tracing faults. One network that I used to look after was a 10BASE2-based Ethernet network. Unfortunately, as it was based on coaxial cable, whenever someone disconnected their computer, it would bring the whole network segment down, or it would slow it down until it was hardly useable. One method that we used to bring the network back up was to disconnect all the computers from the segment. A node nearest the correctly operating segment would be connected, and the other terminated with a terminator. The node was then tested to see if it could log into the network. The nodes were then put back on-line one a time, until the fault was traced (as illustrated in Figure 1).

      A Digital Voltmeter (DVM) was a useful as it could be used to test for the heartbeat voltage. In these days of network hubs and switches, the best method of determining if a node is operating is to view the green LED on the network card and the hub/switch.

      The great problem that I had was when I looked-after a Token Ring network, which worked well, and was very efficient. Unfortunately, a network fault caused terrible problems, as the whole network would go down. To improve fault detection we disconnected each node in turn, and inserted a by-pass cable. The problem from there was getting the ring back on-line, and for it to generate a new token. As the network grew in size, the more difficult it became to find faults. Thus, Token Ring is an excellent networking topology but, at the time, suffered from too many problems. The way was thus clear for Ethernet to carve a massive niche for LANs.

      One method to reduce the number of nodes which are affected by a fault is to segment the network, using bridges, switches or routers. A router offers the best segmentation as it intelligently routes data in to and out of a network segment. Routers have many advantages over bridges, as they do not forward broadcasts (which are typically used with ARP for nodes to find-out the MAC address for a given IP address), and not to forward traffic with an unknown address (as a router will only forward is they know that the destination is outside the network segment).

Figure 1 Fault-finding on a bus network


W. Buchanan, 2000