Latency Budget
Define the hops (speed and distance) and packet size and I compute the latency budget: serialization, propagation and processing delay, end to end.
One-way breakdown
How it is computed · serialization, propagation and processing
Serialization = time to put the bits on the
wire. packet_bits / speed_bps. E.g.:
1500 B at 1 Gbps = 1500×8 / 1e9 = 12 µs.
Propagation = signal travel time.
distance / v, with v ≈ 2×10⁸ m/s. E.g.:
100 km / 2e8 = 500 µs.
Processing = queue + switching per hop, a fixed value multiplied by the number of hops.
Total one-way =
Σ(serialization + propagation + processing) per link.
The RTT ≈ 2× the one-way latency.
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How it works
The calculator builds the latency budget of a network path by adding its three per-link components: serialization (the time to put the bits on the medium), propagation (the physical travel of the signal) and processing (queuing and switching at each hop). You can describe the path in simple mode (N identical hops with a total distance) or link by link with its own speed, distance and processing, and you get the one-way latency, the RTT (≈ 2 × one-way) and which component dominates.
The formulas are the classic traffic-engineering ones: serialization = packet bits ÷ link speed (1500 B at 1 Gbps is 12 µs), propagation = distance ÷ v with v ≈ 2×10⁸ m/s in copper and fiber (two thirds of the speed of light, about 5 µs per km), and processing is a fixed value per hop, typically 10 to 50 µs per device. The one-way total is the sum of the three components across all links.
Example: 5-hop WAN at 1 Gbps spanning 100 km
- Serialization: each hop re-sends the 1500 B packet,
5 × 12 µs = 60 µs. - Propagation:
100 km ÷ 2×10⁸ m/s = 500 µs; processing:5 × 30 µs = 150 µs. - One-way:
60 + 500 + 150 = 710 µsand RTT ≈ 1.42 ms; propagation dominates with 70% of the total.