Calculate the ratio of useful data throughput to total bandwidth consumed.
Network efficiency measures what fraction of consumed bandwidth carries useful application data versus protocol overhead and retransmissions. Framing efficiency accounts for headers (Ethernet, IP, TCP), preamble, and inter-frame gap. Retransmissions further reduce efficiency by consuming bandwidth to resend already-sent data.
Overall efficiency
efficiency = (payload / total_frame) * (1 - retransmission_rate)
Small payload sizes (many small packets means proportionally more header overhead per byte of data), high retransmission rates from lossy links, and additional encapsulation layers (VPN, VXLAN) all reduce efficiency below the theoretical maximum.
With 1460-byte TCP payloads in standard 1518-byte Ethernet frames (plus 20 bytes preamble/IFG), framing efficiency is about 95%. Actual efficiency is somewhat lower due to TCP ACKs, retransmissions, and smaller-than-MSS segments.