headeroverhead

Header overhead refers to the bytes added to user data by protocol headers and related metadata in a data transmission. This overhead is separate from the actual payload and is necessary to enable routing, reliability, integrity checks, and proper delivery across networks and systems. In practice, header overhead is produced at multiple layers and can accumulate quickly when several encapsulations are used.

Across a typical network stack, the main contributors are the link layer, the network layer, and the transport layer. Link-layer headers (for example, Ethernet) frame the packet, while network-layer headers (IPv4 or IPv6) provide addressing and routing information. Transport-layer headers (TCP or UDP) support connection management and data integrity. In addition, encapsulation headers from VPNs, VLANs, or tunneling add further overhead, and application-layer headers such as HTTP request headers may be counted as overhead for end-to-end transfers.

Calculation examples are approximate but illustrative. A common Ethernet network carrying IPv4 with TCP has a minimum of about 40 bytes of IP+TCP headers per packet, plus roughly 14 bytes of Ethernet header and 4 bytes of trailer, totaling around 58 bytes of overhead per frame. With a typical MTU of 1500 bytes, the maximum application data per frame is about 1460 bytes, yielding an efficiency near 96% for that scenario.

Impact and optimization touch on throughput, latency, and energy use. Higher overhead reduces effective throughput and can increase latency, especially in wireless and mobile environments. Mitigation strategies include increasing MTU and using jumbo frames where supported, applying header compression (for example in wireless links), minimizing optional headers, and adopting protocols designed to reduce per-connection overhead, such as QUIC.