SD-WAN Path Selection Calculator
Score two SD-WAN paths on latency, jitter and loss to see which one the policy engine should prefer.
Inputs
Preferred Path
Path A
Path A Score
78.7/100
Path B Score
19.0/100
Score Margin
59.7
Quality of the Winner
B — Good
Step by step
Values used
Path A latency = 18 ms; Path A jitter = 3 ms; Path A packet loss = 0.1000 %; Path B latency = 45 ms; Path B jitter = 12 ms; Path B packet loss = 0.8000 %
SD-WAN Path Selection
score = 100 − (0.6 × latency ms + 2.5 × jitter ms + 30 × loss %), clamped to 0–100; the higher score wins.
Preferred Path
= Path A
Path A Score
= 78.7 /100
Path B Score
= 19.0 /100
Score Margin
= 59.7
Quality of the Winner
= B — Good
How it works
Each impairment is weighted by how badly it damages interactive traffic, then subtracted from a perfect 100. Loss carries the heaviest weight because a single lost packet triggers a retransmit and a TCP window collapse, while a few extra milliseconds of latency are usually invisible. SD-WAN policies steer on thresholds, and a scoring model makes it obvious whether a brownout on the primary path is bad enough to justify moving voice onto the broadband circuit.
Formula
SD-WAN Path Selection
score = 100 − (0.6 × latency ms + 2.5 × jitter ms + 30 × loss %), clamped to 0–100; the higher score wins.
- 30
- Penalty per percent of packet loss — loss hurts far more than delay
- 0.6
- Penalty per millisecond of one-way latency
Frequently Asked Questions
How is SD-WAN Path Selection calculated?
score = 100 − (0.6 × latency ms + 2.5 × jitter ms + 30 × loss %), clamped to 0–100; the higher score wins. Each impairment is weighted by how badly it damages interactive traffic, then subtracted from a perfect 100. Loss carries the heaviest weight because a single lost packet triggers a retransmit and a TCP window collapse, while a few extra milliseconds of latency are usually invisible.
Why does SD-WAN Path Selection matter?
SD-WAN policies steer on thresholds, and a scoring model makes it obvious whether a brownout on the primary path is bad enough to justify moving voice onto the broadband circuit.
What values do I need to enter?
This calculator takes 6 inputs: Path A latency, Path A jitter, Path A packet loss, Path B latency, Path B jitter, Path B packet loss. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.