Throughput Overhead of Packet Switching - Throughput Overhead of Packet Switching - 2026.1 English - UG1603

The effective throughput of a packet-switched path is reduced by two factors that compound at small packet sizes:

Header overhead

Each packet requires one 32-bit header word before the payload, reducing the effective throughput when the packet size N is small.

Arbitration overhead

The stream switch incurs one additional cycle per packet arbitration. On paths that traverse multiple packet-switching stages, this can reach one cycle per packet per switch.

For small packet sizes N, the two overheads multiply. With N=1, the worst case is one 32-bit data word per packet: 1 header + 1 data + 1 arbitration cycle = 3 stream cycles per data word leads to effective throughput ≈ 33% of peak, not the 50% that header overhead alone would imply.