ICMP

ICMP (eng. Internet Control Message Protocol - internet protocol control messages) - network protocol, which is included in the protocol stack TCP / IP. Mainly used for the transmission of ICMP error messages and other exceptional situations arising in the transmission of data. Also at the ICMP placed some service functions. 

Protocol ICMP is documented in RFC 792 (with additions in RFC 950) and a standard Internet (included in the standard STD 5, together with IP). Although ICMP uses IP (ICMP packets encapsulate the IP packets), it is an integral part of IP and is required in the implementation of the stack TCP / IP. The current version of ICMP for IPv4 is called ICMPv4. In IPv6 there is a similar protocol ICMPv6. 

Protocol ICMP IP protocol does not make a reliable means of message delivery. For these purposes, there is TCP. 

ICMP message (type 12) are generated when the error in the header of an IP packet (with the exception of ICMP packets, so as not to lead to an infinitely growing stream of ICMP messages ICMP messages). 

ICMP message (type 3) generated by the router with no route to the destination. 

Utility ping, used to verify the possibility of delivery of IP packets using ICMP message of type 8 (echo request) and 0 (echo reply). 

The utility traceroute, showing the path of the IP packets using ICMP message of type 11. 

ICMP message of type 5 is used by routers to update routing table entries in the sender. 

ICMP message type 4 is used with the recipient (or an intermediate router) to control the speed of sending emails to the sender.

Types of ICMP packets (full list) 
0 - Echo reply 
1 - Reserved 
2 - Reserved 
3 - The destination is not 

Code 0 - Network unattainable 
Code 1 - Host unreachable 
code 2 - Protocol unreachable 
Code 3 - Port unreachable 
Code 4 - Fragmentation needed, but a flag of the ban (DF) 
Code 5 - Invalid route from the source 
Code 6 - Destination network unknown 
Code 7 - Host destination unknown 
code 8 - source host isolated 
Code 9 - Network Administration banned 
Code 10 - Host administratively prohibited 
Code 11 - Network unreachable for TOS 
Code 12 - Host unreachable for TOS 
Code 13 - Communication administratively prohibited 
4 - The containment of the source (the source of deactivation in the overflow queue) 
5 - Redirect 

code 0 - redirect packets to the network 
Code 1 - Redirect packet to host 
Code 2 - Redirect for each type of service (TOS) 
Code 3 - Redirecting packet to the host for each type of service 
6 - Alternate host address 
7 - Reserved 
8 - Echo Request 
9 - Router Advertisement (RFC-1256) 
10 - Request for a router (RFC-1256) 
11 - Excess time interval (for datagram lifetime has expired) 

Code 0 - Lifetime packet (TTL) expired during transportation 
Code 1 - The lifetime of the package (the assembly of fragments) has expired when defragmenting 
12 - Invalid parameter (the problem with parameters datagram: error in the IP-header, or is absent, the option) 

Code 0 - Pointer indicates the error 
code 1 - required option missing 
code 2 - Incorrect length 
13 - Request timestamp 
14 - Answer to the timestamp 
15 - Information Request 
16 - Information reply 
17 - Address Mask Request (RFC-950) 
18 - The response to a request from the address mask (RFC-950) 
19 - Reserved (for security) 
20-29 - Reserved (for experiments on resistance to bugs) 
30 - Tracing route (RFC-1393) 
31 - Error converting datagram (RFC-1475) 
32 - Redirect to a mobile host 
33 - IPv6 Where-Are-You (where you are) 
34 - IPv6 I-Am-Here (I'm here) 
35 - Request for diversion to a mobile host 
36 - The response to the request for redirection of the mobile host 
37 - Request for a domain name (Domain Name Request) 
38 - The answer to the query domain name (Domain Name Reply) 
39 - SKIP 
39 - Photuris 

Code 0 - Reserved 
code 1 - unknown security parameters index (Unkown Security Parameters Index) 
code 2 - security settings are correct, but error occurred authentication (Valid Security Parameters, but Authentication Failed) 
Code 3 - Security settings are correct, but failed in the data decryption (Valid Security Parameters, but Decryption Failed) 
41-255 - Reserved

ICMP