East-West Traffic Calculator
Estimate server-to-server traffic inside a data centre and how much of it actually crosses the fabric.
About East-West Traffic Calculator
Modern application tiers, storage replication and container overlays push 70–80% of data-centre traffic east-west. Only the part that leaves its own rack loads the spine layer, so rack-affinity in workload placement directly reduces fabric utilisation. Fabric upgrades are triggered by east-west growth, not internet growth, and this shows how much headroom the spine layer really has.
Formula
East-West Traffic
east-west = servers × per-server rate × east-west share; fabric load = east-west × share that leaves the rack.
- east-west share
- Fraction of traffic that stays inside the data centre
- leaving its own rack
- Portion that must traverse leaf and spine rather than staying on one ToR
Worked example
With the default values below, East-West Traffic Calculator returns East-West Traffic of 1,200.0. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Servers in the fabricaccepts 1–100,000 servers
- 400 servers
- Busy-hour traffic per serveraccepts 0.01–800 Gbps
- 4 Gbps
- Share that is east-westaccepts 0–100 %
- 75 %
- East-west share leaving its own rackaccepts 0–100 %
- 60 %
- Fabric bandwidth availableaccepts 1–4,000,000 Gbps
- 6,400 Gbps
Results
- East-West Traffic
- 1,200.0 Gbps
- Traffic Crossing the Fabric
- 720.0 Gbps
- North-South Traffic
- 400.0 Gbps
- Fabric Utilisation
- 11.25%
- Total Traffic
- 1,600.0 Gbps
Step by step
- 1Values used
- 2East-West Traffic
- 3East-West Traffic= 1,200.0 Gbps
- 4Traffic Crossing the Fabric= 720.0 Gbps
- 5North-South Traffic= 400.0 Gbps
- 6Fabric Utilisation= 11.25
- 7Total Traffic= 1,600.0 Gbps
Assumptions and limits
- The result is derived only from the 5 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
How is East-West Traffic calculated?
east-west = servers × per-server rate × east-west share; fabric load = east-west × share that leaves the rack. Modern application tiers, storage replication and container overlays push 70–80% of data-centre traffic east-west. Only the part that leaves its own rack loads the spine layer, so rack-affinity in workload placement directly reduces fabric utilisation.
Why does East-West Traffic matter?
Fabric upgrades are triggered by east-west growth, not internet growth, and this shows how much headroom the spine layer really has.
What values do I need to enter?
This calculator takes 5 inputs: Servers in the fabric, Busy-hour traffic per server, Share that is east-west, East-west share leaving its own rack, Fabric bandwidth available. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.