| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Type (13/14) | 0 | ICMP header checksum | |||||||||||||||||||||||||||||
| Identifier | Sequence Number | ||||||||||||||||||||||||||||||
| originating timestamp | |||||||||||||||||||||||||||||||
| received timestamp | |||||||||||||||||||||||||||||||
| transmitted timestamp | |||||||||||||||||||||||||||||||
notes:
originating timestamp is value provided by originating device on transmission
received timestamp is value provided by receiving device on receipt
transmitted timestamp is time value provided by receiving device on return transmission
ICMP header immediately follows IP header
Type Name/Codes (Code=0 unless otherwise specified)
0 Echo Reply 3 Destination Unreachable 0 Net Unreachable 1 Host Unreachable 2 Protocol Unreachable 3 Port Unreachable 4 Fragmentation Needed & DF Set 5 Source Route Failed 6 Destination Network Unknown 7 Destination Host Unknown 8 Source Host Isolated 9 Network Administratively Prohibited 10 Host Administratively Prohibited 11 Network Unreachable for TOS 12 Host Unreachable for TOS 13 Communication Administratively Prohibited 4 Source Quench 5 Redirect Message 0 Redirect Datagram for the Network 1 Redirect Datagram for the Host 2 Redirect Datagram for the TOS & Network 3 Redirect Datagram for the TOS & Host 6 Alternative Host Address 7 Reserved 8 Echo 9 Router Advertisement 10 Router Selection 11 Time Exceeded 0 Time to Live exceeded in Transit 1 Fragment Reassembly Time Exceeded 12 Parameter Problem 0 Pointer indicates the error 1 Missing a Required Option 2 Bad Length 13 Timestamp 14 Timestamp Reply 15 Information Request 16 Information Reply 17 Address Mask Request 18 Address Mask Reply 19 reserved for security 20-29 reserved 30 Traceroute 31-41 various services 42-255 reserved