User Datagram Protocol. A connectionless protocol for use on IP networks. Unlike TCP, it has few error-correction features. This shortcoming reserves it mostly to broadcasting tasks, where accurate transmission is not as important.


A non-graphical operating system designed to be small, powerful, and flexible. It was first developed by Bell Labs in the 1970’s, and has since undergone many changes. It is the basis for Linux, and is still the most popular operating system for high-demand web servers.

A port on hubs/switches that crosses over the circuits of any cable plugged into it.

Uplink ports were originally designed for the purpose of daisy-chaining hubs together, but they can also be used to connect a cable modem directly to a LAN.

Note: a regular cable connected to an uplink port serves the same function as a crossover cable connected to a normal port.


Refers to the transmission of data from your comptuter to the Internet. It is usually seen as upstream speed---the upload speed of your Internet connection.


Universal Serial Bus. A standardized interface for connecting peripherals to computers.

USB 1.1 can transmit data at 12 Mbps, and does not require the user to reboot to install new devices. In theory, up to 127 devices can be daisy-chained to operate at the same time on a single USB port. Due to this simplicity, there are now thousands of devices available for USB, including external NICs.

USB 2.0 was recently released, offering speeds of up to 480 Mbps while maintaing backward compatibility with all USB 1.1 devices.


Unshielded Twisted-pair. A type of twisted-pair cabling that has no electromagnetic shielding. Due to the high cost and low benefit of shielded cabling, most category 5 cable made today is UTP.