Network Fabric Latency Calculator
Add switch, serialisation, cable propagation and queueing delay to get end-to-end fabric latency.
About Network Fabric Latency Calculator
Cut-through switches contribute a fixed sub-microsecond delay per hop, propagation adds 5 ns per metre of fibre, and serialisation is the packet clocking out at line rate. Faster ports shrink serialisation dramatically — a 1500-byte frame takes 12 µs at 1G but only 0.12 µs at 100G. Storage, RDMA and distributed databases quote latency budgets in microseconds, and this breakdown shows whether hops, cable runs or queueing is the part worth engineering.
Formula
Network Fabric Latency
latency = hops × switch latency + hops × cable metres × 5 ns/m + hops × serialisation + queueing, where serialisation = packet bits ÷ port speed.
- 5 ns/m
- Propagation delay of light in glass, about 200 000 km/s
- serialisation
- Time to clock a full packet onto the wire at port speed
Worked example
With the default values below, Network Fabric Latency Calculator returns One-way Fabric Latency of 5.210. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Switch hopsaccepts 1–20 hops
- 3 hops
- Latency per switchaccepts 0.05–100 µs
- 0.8 µs
- Cable length per hopaccepts 0.5–40,000 m
- 30 m
- Packet sizeaccepts 64–9,216 bytes
- 1,500 bytes
- Port speedaccepts 1–800 Gbps
- 100 Gbps
- Queueing delay budgetaccepts 0–10,000 µs
- 2 µs
Results
- One-way Fabric Latency
- 5.210 µs
- Round-trip Latency
- 10.420 µs
- Switching Delay
- 2.400 µs
- Cable Propagation
- 0.450 µs
- Serialisation per Hop
- 0.1200 µs
Step by step
- 1Values used
- 2Network Fabric Latency
- 3One-way Fabric Latency= 5.210 µs
- 4Round-trip Latency= 10.420 µs
- 5Switching Delay= 2.400 µs
- 6Cable Propagation= 0.450 µs
- 7Serialisation per Hop= 0.1200 µs
Assumptions and limits
- The result is derived only from the 6 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 4 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 Network Fabric Latency calculated?
latency = hops × switch latency + hops × cable metres × 5 ns/m + hops × serialisation + queueing, where serialisation = packet bits ÷ port speed. Cut-through switches contribute a fixed sub-microsecond delay per hop, propagation adds 5 ns per metre of fibre, and serialisation is the packet clocking out at line rate. Faster ports shrink serialisation dramatically — a 1500-byte frame takes 12 µs at 1G but only 0.12 µs at 100G.
Why does Network Fabric Latency matter?
Storage, RDMA and distributed databases quote latency budgets in microseconds, and this breakdown shows whether hops, cable runs or queueing is the part worth engineering.
What values do I need to enter?
This calculator takes 6 inputs: Switch hops, Latency per switch, Cable length per hop, Packet size, Port speed, Queueing delay budget. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.