What effect does a network bottleneck have on data transfer?

A network bottleneck occurs when the flow of data is restricted at a particular point in the network, which typically leads to congestion and reduced transmission capacity. When a bottleneck happens, it results in data traffic exceeding the available capacity for transmission through that constrained point. This means that not all data can flow freely, causing delays in data transfer and potentially leading to packet loss or retransmission.

The other options do not accurately describe the effect of a bottleneck. Increasing data transfer speed, improving redundancy, or enhancing security measures are not outcomes of a bottleneck; rather, these factors are generally independent of the issues created by congestion in network traffic. Thus, identifying the correct impact of a bottleneck helps in understanding the importance of managing network capacity and performance effectively.