sFlow and NetFlow both analyze traffic but use different approaches.
NetFlow tracks every flow. Accurate but requires router CPU. High-speed links can overwhelm routers.
sFlow samples packets. It captures in every packets and extrapolates totals. Less accurate but scales to any speed.
When to use NetFlow:
- You need accurate per-flow accounting
- Traffic volumes are manageable
When to use sFlow:
- G+ links where full tracking is impractical
- Switch-based monitoring
- Real-time visibility over precision
sFlow also samples counter data, giving you interface statistics.