ICMP



The Internet Control Message Protocol (ICMP), defined in the RFC792, prepares information of general type over problems with IP-data or serves actions as simple form of the time stamps or echo.



8

16

32 bits

Type

Code

Checksum

Type and Code dependently



TypeMessage type:

Type

Meaning

Reference

3

Destination Unreachable[RFC792]

4

Source Quench[RFC792]

5

Redirect[RFC792]

6

Alternate Host Address[JBP]

8 / 0

Echo Request / Echo Reply[RFC792]

9 / 10

Router Advertisement / Router Solicitation[RFC1256]

11

Time Exceeded[RFC792]

12

Parameter Problem[RFC792]

13 / 14

Timestamp Request / Timestamp Reply[RFC792]

15 / 16

Information Request / Information Reply[RFC792]

17 / 18

Adress Mask Request / Adress Mask Reply[RFC950]

19

"Reserved" (for Security)[Solo]

20..29

"Reserved" (for Robustness Experiment)[ZSu]

30

Traceroute[RFC1393]

31

Datagram Conversion Error[RFC1475]

32

Mobile Host Redirect[Johnson]

33 / 34

IPv6 Where-Are-You / IPv6 I-Am-Here[Simpson]

35 / 36

Mobile Registration Request / Mobile Registration Reply[Simpson]

37 / 38

Domain Name Request / Domain Name Reply[RFC1788]

39

SKIP[Markson]

40

Photuris[RFC2521]

41..255

"Reserved" for future use

...
CodeType specific information
ChecksumChecksum over ICMP-packet plus a so-called pseudo-header as protection against lacking segments (Source IP-Adresse, Destination IP-Adresse, Transport protocol, ICMP-length)
Type and Code dependentlyaccording to Type and Code (see RFC792 / RFC 1700)