Network Fabric Latency Calculator
Add switch, serialisation, cable propagation and queueing delay to get end-to-end fabric latency.
Inputs
One-way Fabric Latency
5.210µs
Round-trip Latency
10.420µs
Switching Delay
2.400µs
Cable Propagation
0.450µs
Serialisation per Hop
0.1200µs
Step by step
Values used
Switch hops = 3 hops; Latency per switch = 0.8000 µs; Cable length per hop = 30 m; Packet size = 1,500 bytes; Port speed = 100 Gbps; Queueing delay budget = 2 µs
Network Fabric Latency
latency = hops × switch latency + hops × cable metres × 5 ns/m + hops × serialisation + queueing, where serialisation = packet bits ÷ port speed.
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
How it works
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
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.