Operation Manual

Appendix B: Types of ICMP Messages
Appendix B: Types of ICMP Messages
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Field Value Description
0 Echo Reply
3 Destination Unreachable
4 Source Quench
5 Redirect
8 Echo Request
10 Router Solicitation
11 Time Exceeded For Datagram
12 Parameter Problem On Datagram
13 Timestamp Request
14 Timestamp Reply
16 Information Reply
17 Address Mask Request
18 Address Mask Reply
Echo Request is one of the simplest methods of checking operating conditions of a
network node. Once an echo signal is received, any network node generates an Echo Reply
and returns it to the source. If the source receives a reply to the echo request, this indicates
that the main components of the traffic system are in good condition.
Destination Unreachable is generated by a gateway when it cannot deliver an IP
datagram. This is the unit of data, or packet, transmitted in a TCP/IP network. Each
datagram contains source and destination addresses and data.
A Source Quench ICMP message is transmitted from the node to the datagram source in
the event that the input queue is overcrowded. In this case, the datagram is removed from
the queue.
A Redirect ICMP message is transmitted when a gateway detects that a non-optimal route
is used, then the gateway sends a request for a change of route in the routing table.
An IP Announcement ICMP message transmits a broadcast to announce its IP address.
The Time Exceeded For Datagram ICMP message is sent when a datagram is transferred
from one gateway to another more times than it is allowed (normally this indicates route
cycling).
A Parameter Problem on Datagram ICMP message is sent by a gateway if a problem
occurs during the transmission of a specific datagram that is not in the range of the above
messages. The datagram must be abandoned due to this error.
The Timestamp Request and Timestamp Reply ICMP messages are used to synchronize
the clocks in a network’s nodes.