Docker Overlay Network Calculator
Calculate overlay network overhead and capacity across a Docker Swarm cluster.
Inputs
Number of nodes in the Swarm cluster.
Average containers per node on the overlay.
Physical host-to-host bandwidth.
Per-packet VXLAN encapsulation overhead.
Effective Cross-Node Bandwidth
9.67Gbps
VXLAN Overhead
3.3%
Total Containers on Overlay
150
Node Mesh Connections
10
Step by step
Total containers on overlay
5 × 30
= 150
VXLAN overhead percentage
50B / 1500B
= 3.3%
Effective cross-node bandwidth
10Gbps × (1 − 3.3%)
= 9.67Gbps
How it works
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).
Formula
Effective Bandwidth
effective = hostBandwidth × (1 − vxlanOverhead / MTU)
- hostBandwidth
- Physical host bandwidth
- vxlanOverhead
- VXLAN encapsulation bytes
- MTU
- Maximum transmission unit (typically 1500)
Frequently Asked Questions
Can I reduce VXLAN overhead?
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.
How does gossip protocol scale?
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.
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