ICMP Types and Codes
| TYPE | CODE | FUNCTION |
| 0/8 | 0 | Echo Response / Request (Ping) |
| 3 | 0-15 | Destination Unreachable |
| 4 | 0 | Source Quench |
| 5 | 0-3 | Redirect |
| 11 | 0-1 | Time Exceeded |
| 12 | 0 | Parameter Fault |
| 13/14 | 0 | Time stamp request / reponse |
| 17/18 | 0 | Subnet mask request / response |