Intro to networking

The parts have started to arrive for the North Star computer we're building. So far, we've only gotten the wireless card, but I expect the rest of the parts to arrive soon. The first thing the students want to work on is the connectivity in the building, so Step 1 will be to set up our own wireless access-point/NAT Gateway. So today we did an intro to networking.

We mainly looked at the output of ifconfig. We talked about packets and their structure (with a header containing address information and a payload) and about the differences between TCP and UDP and what an MTU is . We looked at hexidecimal digits and talked about translating between hex and base-10 and binary. We looked at the IP address, broadcast, and netmask and briefly discussed what they do. We talked about NAT and DHCP and why the 192.x.x.x address space is used inside and why you sometimes see 169.x.x.x addresses. We did some thought puzzles: why would adding one to the last octet still work and adding one to the first octet not work?

One bit I didn't think to talk about was to close the circle in terms of how processors load and manipulate data in registers and why netmasks work the way they do. That's not something I actually understand all that well myself -- just enough to wave my hand at it and say XOR or something. We can take that up next week, if we're not too busy actually putting parts together.