2. Internet Control Message Protocol (ICMP)
ICMP a network monitoring protocol that’s designed specifically for error
reporting. Network devices rely on ICMP to transmit error messages. For example,
a router might use ICMP in a situation where a host or
client cannot be reached, or
queried information is unavailable. Contrary to SNMP, ICMP is not used in
scenarios where an exchange of data takes place between systems. However, it’s
often used by network admins and analysts to troubleshoot internet connections
within diagnostic utilities such as traceroute or ping.
ICMP is a connectionless protocol which is not associated with transport layer
protocols like TCP or UDP. There is no need for a device to open a connection
with the target device before
transmitting a message, unlike TCP, for instance.
Rather, ICMP messages are sent as datagrams, consisting of
an IP header which
encapsulates ICMP data. This ensures that the specific failed packet is identified to
the request source that receives the error message.
Common error messages ICMP reports include:
•
Destination unreachable
•
Redirect
•
Time exceeded
•
Parameter problem
•
Source quench (deprecated)
•
Destination unreachable
•
Packet too big