hysical connection of the lines in a network-or, the "view from the top"-which is the shape of the network, the configuration in which lines are connected to one another. traffic shaping A way for carriers to manage traffic to control congestion. Techniques include providing better QoS for particular types of traffic such as video, prioritizing traffic for higher fees, and throttling traffic (decreasing speeds) for subscribers who exceed allotted amounts. transponder Fiber-optic transponders receive, amplify, and retransmit optical signals on different wavelength channels on fiber cabling. They also convert electrical signals to optical signals and optical signals back to electrical signals where they connect to twisted-pair copper or coaxial cabling. trunking gateway Converts packet network circuits (such as T1/E1 and T3/E3), to those compatible with the Public Switched Telephone Network (PSTN), and vice versa, SO that voice traffic can be transferred between IP networks and traditional, circuit-switched networks. trunks The circuits (electrical or fiber paths) between telephone companies and enterprise telephone systems and between central office switches. A T1 is a trunk. tuner Used in televisions, radios, and set-top boxes to filter out all channels (frequencies) except the particular one at the www.TechnicalPDF.com frequency the tuner is designed to accept. The tuner then adapts the frequency to ones compatible with the TV or radio. Newer set-top boxes are equipped with multiple tuners SO that one channel can be recorded while another is being viewed. tunneling A method of securely transferring data between sites connected by networks such as a VPN, the Internet, an intranet, or an extranet. Tunneling puts a new header in front of the data. This is a way of separating data from multiple companies using the same network. UDP (User Datagram Protocol) Part of the TCP/IP suite of protocols. UDP has less overhead because it does not have bits with packet numbers and acknowledgments. UDP is considered a connection