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SampleA1

HW06a

1. IP Basics
   • only the values 255, 254, 252, 248, 240, 224, 192, 128, and 0 can be used in any octet in a netmask in dotted decimal representation
   • see Lava's CIDR Reference for an example (with more info than I requested)
2. Troubleshooting
   • stolen IP address
   • DNS breaks, "the Internet is broken" user reports but actually you just can't get to anything by name (and who remembers numbers?)
3. A Sense of History
   • Elisha Gray filed a patent for the telephone 3 hours after AGB. And why would any person want to use this ungainly and impractical device when he can send a messenger to the telegraph office and have a clear written message sent to any large city in the United States?
   • 75% of phone lines in 1950 were party lines!
4. A Sense of Global Cabling Issues
   • capacitance slows and distorts a signal, so timing is off as well as signal levels for 1s and 0s; picture a ballon inline on a hose
   • resistance weakens a signal; picture an obstacle course ... the longer (longer distance) or the harder (higher resistance), the more the signal weakens
5. Route Once, Switch Many
   • routers add latency
   • switches are fast, routers are slow; so for performance, use switches when you can! (or to put it another way: route once, switch many)