ing them in words that can be used to set performance expectations where money is to be paid in exchange is even wiser. Drawing a diagram and making a list of locations and facility or circuit identifi- cation numbers that the definitions cover is absolutely necessary to ensure services received meet expectations; otherwise, money may be paid for inferior or unsatisfactory services. Here are some generalized statements in layman language to serve as a starting point for definitions in a service contract. Availability is a measure of the time network resources being paid for that are actually available for use. The time period may be as speci- fied as 24 hours a day, 7 days a week, 365 days a year. Reliability is a measure of the time the network is performing in accordance with specifications when it is available. Robustness is a measure of the network's ability to recover from loss of service caused by a malfunction of one or more elements making up the network. Bit error rate, also referred to as bit error ratio, is a measure of bit errors received, compared to the total number of bits received over a given time. Packet networks measure lost packets instead of measuring bit errors. The packet either makes it through the network, or it doesn't. Obviously, if the network doesn't successfully carry a packet, there will be errors in a file. Transmission facilities in communications networks are built on terres- trial and satellite radio wave (wireless), wire, and light wave media. PRACTICAL IP AND TELECOM FOR BROADCAST ENGINEERING AND OPERATIONS In general, wire has significant distance limitations depending on the electrical bandwidth and level of signal it's expected to carry. Radio waves are better than wire in both respects, but not nearly as capable as light waves. Light waves have many times the bandwidth capacity as radio waves. For example, broadcast satellite service (BSS) facilities are designed around an architecture having 32 transponder channels, each with 32MHz occupied bandwidth. Each channel carries