Unspecified Bit Rate. In ATM QoS, UBR means that packets are delivered on a "best-efforts" basis, with no guarantees of delivery or delay.
User Datagram Protocol. UDP is a non-connection oriented Layer 4 protocol built on top of the IP Network Layer. Because it is not connection oriented, it is not able to verify delivery of packets.
User to Network Interface. In ATM network, UNI specifies the connection point between the first ATM switch at the edge of the ATM network and the device that it connects to. This device may be an end device, or it may be an switch that provides both ATM and LAN interfaces. In many cases, the UNI device connects the ATM network to a port on a LAN router.
A piece of data that is sent from one source to only one destination device.
See UDP.
Unshielded Twisted Pair. A type of cabling in each run of cable contains a bundle of several strands of copper wire. The individual strands are insulated separately and are twisted around one another in pairs to improve the electrical impedance characteristics. See also STP.