Calculate overlay network overhead and capacity across a Docker Swarm cluster.
Docker overlay networks use VXLAN to tunnel container traffic across hosts. Each packet gains ~50 bytes of encapsulation overhead, reducing effective MTU and throughput. Formula: effectiveBandwidth = hostBandwidth × (1 − vxlanOverhead/MTU).
Effective Bandwidth
effective = hostBandwidth × (1 − vxlanOverhead / MTU)
Using jumbo frames (MTU 9000) on the physical network reduces the relative overhead percentage, since the VXLAN header is a fixed ~50 bytes regardless of payload size.
Docker's gossip-based overlay uses a full mesh between nodes — at very large node counts (100+), gossip traffic and convergence time can become significant.