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Docker Overlay Network Calculator

Calculate overlay network overhead and capacity across a Docker Swarm cluster.

About Docker Overlay Network Calculator

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)

Worked example

With the default values below, Docker Overlay Network Calculator returns Effective Cross-Node Bandwidth of 9.67. Change any input above and every figure here is recalculated in your browser.

Inputs used

Swarm Nodesaccepts 2–10,000 nodes
5 nodes
Containers per Nodeaccepts 1–5,000 containers
30 containers
Host Bandwidthaccepts 0.1–400 Gbps
10 Gbps
VXLAN Overheadaccepts 30–100 bytes
50 bytes

Results

Effective Cross-Node Bandwidth
9.67 Gbps
VXLAN Overhead
3.3%
Total Containers on Overlay
150
Node Mesh Connections
10

Step by step

  1. 1Total containers on overlay= 150
  2. 2VXLAN overhead percentage= 3.3%
  3. 3Effective cross-node bandwidth= 9.67Gbps

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

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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