Internet Control Message Protocol
Các thông báo điều khiển

| Type | Code | Status | Description |
| --- | --- | --- | --- |
| 0 – Echo Reply | 0 |  | Echo reply (used to ping) |
| 1 and 2 |  | unassigned | Reserved |
| 3 – Destination Unreachable | 0 |  | Destination network unreachable |
| 3 – Destination Unreachable | 1 |  | Destination host unreachable |
| 3 – Destination Unreachable | 2 |  | Destination protocol unreachable |
| 3 – Destination Unreachable | 3 |  | Destination port unreachable |
| 3 – Destination Unreachable | 4 |  | Fragmentation required, and DF flag set |
| 3 – Destination Unreachable | 5 |  | Source route failed |
| 3 – Destination Unreachable | 6 |  | Destination network unknown |
| 3 – Destination Unreachable | 7 |  | Destination host unknown |
| 3 – Destination Unreachable | 8 |  | Source host isolated |
| 3 – Destination Unreachable | 9 |  | Network administratively prohibited |
| 3 – Destination Unreachable | 10 |  | Host administratively prohibited |
| 3 – Destination Unreachable | 11 |  | Network unreachable for TOS |
| 3 – Destination Unreachable | 12 |  | Host unreachable for TOS |
| 3 – Destination Unreachable | 13 |  | Communication administratively prohibited |
| 3 – Destination Unreachable | 14 |  | Host Precedence Violation |
| 3 – Destination Unreachable | 15 |  | Precedence cutoff in effect |
| 4 – Source Quench | 0 | deprecated | Source quench (congestion control) |
| 5 – Redirect Message | 0 |  | Redirect Datagram for the Network |
| 5 – Redirect Message | 1 |  | Redirect Datagram for the Host |
| 5 – Redirect Message | 2 |  | Redirect Datagram for the TOS & network |
| 5 – Redirect Message | 3 |  | Redirect Datagram for the TOS & host |
| 6 |  | deprecated | Alternate Host Address |
| 7 |  | unassigned | Reserved |
| 8 – Echo Request | 0 |  | Echo request (used to ping) |
| 9 – Router Advertisement | 0 |  | Router Advertisement |
| 10 – Router Solicitation | 0 |  | Router discovery/selection/solicitation |
| 11 – Time Exceeded | 0 |  | TTL expired in transit |
| 11 – Time Exceeded | 1 |  | Fragment reassembly time exceeded |
| 12 – Parameter Problem: Bad IP header | 0 |  | Pointer indicates the error |
| 12 – Parameter Problem: Bad IP header | 1 |  | Missing a required option |
| 12 – Parameter Problem: Bad IP header | 2 |  | Bad length |
| 13 – Timestamp | 0 |  | Timestamp |
| 14 – Timestamp Reply | 0 |  | Timestamp reply |
| 15 – Information Request | 0 | deprecated | Information Request |
| 16 – Information Reply | 0 | deprecated | Information Reply |
| 17 – Address Mask Request | 0 | deprecated | Address Mask Request |
| 18 – Address Mask Reply | 0 | deprecated | Address Mask Reply |
| 19 |  | reserved | Reserved for security |
| 20 through 29 |  | reserved | Reserved for robustness experiment |
| 30 – Traceroute | 0 | deprecated | Information Request |
| 31 |  | deprecated | Datagram Conversion Error |
| 32 |  | deprecated | Mobile Host Redirect |
| 33 |  | deprecated | Where-Are-You (originally meant for IPv6) |
| 34 |  | deprecated | Here-I-Am (originally meant for IPv6) |
| 35 |  | deprecated | Mobile Registration Request |
| 36 |  | deprecated | Mobile Registration Reply |
| 37 |  | deprecated | Domain Name Request |
| 38 |  | deprecated | Domain Name Reply |
| 39 |  | deprecated | SKIP Algorithm Discovery Protocol, Simple Key-Management for Internet Protocol |
| 40 |  |  | Photuris, Security failures |
| 41 |  | experimental | ICMP for experimental mobility protocols such as Seamoby [RFC4065] |
| 42 through 252 |  | unassigned | Reserved |
| 253 |  | experimental | RFC3692-style Experiment 1 (RFC 4727) |
| 254 |  | experimental | RFC3692-style Experiment 2 (RFC 4727) |
| 255 |  | reserved | Reserved |