How do bandwidth and throughput differ?

• A. Bandwidth is the actual data rate; throughput is the theoretical maximum
• B. Bandwidth is the theoretical maximum data rate; throughput is the actual data rate achieved
• C. They are the same
• D. Bandwidth is the distance signal travels; throughput is the number of packets per second

Answer: (B)

The main idea here is the difference between a link’s capacity and what you actually get moving data across it. Bandwidth is the maximum data rate a link can carry—the theoretical limit set by the physical medium and signaling. Throughput is the real rate at which useful data is transferred, which you observe in practice.

Throughput is usually lower than bandwidth because of overhead and inefficiencies: protocol headers, framing, error checking, retransmissions from errors, and congestion all eat into the usable data rate. So even if a link can handle, say, 100 Mbps in theory, the actual data you get across it might be less than that due to these factors.

In short, bandwidth = theoretical maximum data rate; throughput = actual data rate achieved. The other descriptions mix up these ideas or point to unrelated concepts like distance.