Sample Triggering Policies
Threshold based (relative change)
- Updates are generated when difference between new and old values exceeds given percentage of old value
- Avoids unnecessary updates when little or no change, but responsive to large changes
- Potential for wide range of bandwidth values
- Impact on number of equal cost paths
Class based (absolute change)
- Link capacity is split into classes and updates are triggered when class boundaries are crossed
- Class size allows tuning of trade-off between accuracy and LSA load
- Hysteresis (or timer) mechanism needed to avoid oscillations
- Choice of class values can substantially affect path selection
- Quantized values maximize likelihood of multiple equal cost paths
- Large values can yield non-pruning policies (all links are always feasible)