(Or "throughput") The ammount of data transferred in one direction over a link divided by the time taken to transfer it, usually expressed in bits or bytes per second.

Where data transfer is not continuous throughout the given time interval, the data transfer rate is thus an average rate that will be lower than the peak rate. The peak or maximum possible rate may itself be lower than the capacity of the communication channel used if the channel is shared, or part of the signal is not considered as data, e.g. checksum or routing information.

The other important characteristic of a channel is its latency.