CertiGuide to A+ (Core Hardware)  9  Chapter 1011:  Networking       9  VIII  Protocols

TCP/IP 1 IX  Networking Devices

With the explosion of the Internet, suddenly everybody wanted an IP number. And why not? You can't be on the Internet without one. When they designed TCP/IP it was for the military to have a way to communicate. Having many millions of IP numbers seemed like more than enough for that need. Almost 50 years and a few billion PCs later, it turns out to not be enough numbers. Well the Internet engineers came up with a great idea. Why not let a PC (or other device) borrow an IP number, to be returned when it isn't being used, so it can be handed out again?

That is where the Dynamic Host Configuration Protocol (DHCP) came from. If you are wondering what the word HOST has to do with a PC, in TCP/IP, not everything is a PC. Some printers attach to the network with an IP number. Printers sure are not PCs. To TCP/IP anything that is attached to a network that isn't a network name and gets an IP number is known in TCP/IP lingo as a Host. DHCP is setup by a device to loan out an IP address, and check with the host to see if it still needs it. When it isn't in use, it is taken back and reused, effectively re-cycling IP numbers, and making them more available. Some devices, say the one that is dishing out IP numbers, like a librarian, cannot have a dynamic IP number. How would a host know where to contact the holder of the borrowed IP numbers? These devices are said to have Static IP numbers (the number never changes).

One more thought before moving on to network hardware. Remember we said that everything is number based? Yet, you probably know that you enter human talk, like TotalRecallPress.com, to see what is going on there. The Internet has a big database in the sky that makes the conversion from names to numbers. This conversion is done by Domain Name Servers (DNS). DNS servers have static IP addresses so everything knows where to get the conversion from so the binary devices can talk.

TCP/IP 1 IX  Networking Devices