In telecommunications, data rate units are commonly multiples of bits per second (bit/s) and bytes per second (B/s). For example, the data rates of modern residential high-speed Internet connections are commonly expressed in megabits per second (Mbit/s). They are used as units of measurement for expressing data transfer rate, the average number of bits, characters or symbols, or data blocks per unit time passing through a communication link in a data-transmission system.