East-West Traffic Calculator
Estimate server-to-server traffic inside a data centre and how much of it actually crosses the fabric.
Inputs
East-West Traffic
1,200.0Gbps
Traffic Crossing the Fabric
720.0Gbps
North-South Traffic
400.0Gbps
Fabric Utilisation
11.25%
Total Traffic
1,600.0Gbps
Step by step
Values used
Servers in the fabric = 400 servers; Busy-hour traffic per server = 4 Gbps; Share that is east-west = 75 %; East-west share leaving its own rack = 60 %; Fabric bandwidth available = 6,400 Gbps
East-West Traffic
east-west = servers × per-server rate × east-west share; fabric load = east-west × share that leaves the rack.
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
How it works
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
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.