Bandwidth
Bandwidth is the maximum rate of data transfer across a network path, measured in bits per second (Mbps, Gbps). High bandwidth allows large files to transfer quickly. Bandwidth is often confused with latency – a high-bandwidth connection can still have high latency.
Definition
Bandwidth is the capacity of a network link – how much data it can carry per second. A 1 Gbps Ethernet link has 1,000 Mbps of bandwidth. Bandwidth determines how quickly large payloads transfer but does not affect the latency of the first byte. A satellite connection might have 100 Mbps bandwidth but 600ms latency – files eventually transfer quickly but interactive operations feel slow. For web performance, bandwidth typically becomes the bottleneck only for large assets (video, large file downloads). For APIs and web pages, latency is usually the primary constraint.
Related Protocols
Related Terms
Latency
Latency is the time delay between a request being sent and the first byte of a response being received. Measured in milliseconds. Network latency is dominated by the speed of light over physical distance (1ms per 100km), plus queuing and processing delays.
Congestion
Network congestion occurs when traffic exceeds link or buffer capacity, causing packet loss and increased latency. TCP congestion control algorithms (Cubic, BBR, Reno) dynamically adjust sending rate to avoid overwhelming the network. Persistent congestion degrades all traffic on the shared path.
Throughput
Throughput is the actual data transfer rate achieved on a network connection, measured in bits per second. Throughput is always less than bandwidth due to protocol overhead, congestion, packet loss, and retransmissions. TCP throughput is bounded by: min(rwnd, cwnd) / RTT.