Working on Networking

By Jerry Pournelle

June 23, 2003

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Column 275 (Continued from the Previous Week)

Enter the Hawking

Chaos Manor already has a network complete with DHCP service. This is all provided by Imperator, a fairly old and slow Pentium III running Windows Server 2000, and Creon, a somewhat newer and faster Pentium III also running Windows Server 2000. Unlike NT 4, which has a Primary Domain Controller and one or more Backup Domain Controllers, under Windows 2000 Server you can have several Domain Controllers in operation. Imperator and Creon are peers, although Imperator is slightly more equal than Creon in that in the current configuration all the printers go through him. Anyway, we have a network already.

The Chaos Manor network is set up to look to Imperator at 192.168.1.2 for DHCP service, as well as for DNS service. DNS = Domain Name Service, and translates computer names such as Yahoo.com and Earthlink.net into net addresses such as 66.218.70.49 and 207.217.114.220. Internally it's more complicated because a thing called WINS (Windows Internet Name Service) gets in the act of translating computer names like Imperator to 192.168.1.2, but it's the same process.

Our system is set up to ask Imperator for name service (so that we can refer to our computers by their names rather than by their IP addresses) and if Imperator can't provide this because the name—like Yahoo or Earthlink—isn't part of our local domain, he goes to a DNS server out on the Internet. And every computer at Chaos Manor looks to 192.168.1.1 as its primary gateway to the outside world.

Before Cable Modem, 192.168.1.1 was the address of the Rebel Netwinder, a Linux box that connected Chaos Manor to the iDSL modem. This made it very easy to change over to connection through the satellite: Mercury, the PC that connects to the satellite modem also has the address 192.168.1.1. Clearly both Mercury and the Netwinder can't be on the net at the same time, but by connecting one and disconnecting the other I can switch from satellite to iDSL connection in seconds, and the other machines in the net never know the difference.

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