Bandwidth and Latency

Part of: Computer Systems & Networks

Two Different Measures of Speed People say a connection is "fast," but speed has two distinct meanings: - Bandwidth is the rate of data transfer, measured in bits per second (for example, megabits per second, Mbps). It is how much data can flow per unit time, like the width of a pipe. - Latency is the delay before data starts arriving, measured in time (for example, milliseconds). It is how long the first bit takes to make the trip, like the length of the pipe. A satellite link can have high bandwidth but high latency , while a short cable can have low latency but limited bandwidth. They are independent. Estimating Transfer Time A simple model of how long a transfer takes adds the startup delay to the streaming time: Watch the units . Bandwidth is in bits per second, but file sizes are often in bytes . Since 1 byte = 8 bits, you must convert: Why Both Matter - For large downloads , bandwidth dominates: a bigger pipe finishes sooner. - For quick back-and-forth (clicking a link, a game input), latency dominates, because each tiny message still pays the delay. - Throughput , the actual delivered rate, is usually lower than the rated bandwidth because of overhead and congestion. The Bi

Challenge: Estimate Transfer Time