Before WCF 4.0 the default values were
- Concurrent Calls: 16
- Concurrent Sessions: 10
- Concurrent Instances: Concurrent Calls + Concurrent Sessions (26)
From WCF 4.0 onwards they are
- Concurrent Calls: 16 * processor count
- Concurrent Sessions: 100 * processor count
- Concurrent Instances: Concurrent Calls + Concurrent Sessions