Work out protocol overhead instantly with clear inputs, formula shown and shareable results.
Every frame carries an Ethernet header and trailer, preamble and inter-frame gap totalling 38 bytes, plus IP and transport headers. With a 1460-byte payload that is about 95 percent efficiency, but small packets are far worse — a 20-byte voice payload spends more than three quarters of the wire on headers, which is why voice bandwidth per call is many times its codec rate.
Protocol efficiency
headers = 38 Ethernet + IP header + transport header (+ RTP); efficiency = payload / (payload + headers); wire rate = goodput / efficiency
Because they occupy time on the wire even though they are not part of the frame. Ignoring them understates the required link rate by about 1.3 percent at full-size frames and far more at small ones.
At 9000 bytes efficiency rises above 99 percent and per-packet CPU cost falls sharply. The catch is that every device in the path must agree on the larger MTU.