Section 6.3: Internet Control Message Protocol (ICMP)
Internet Control Message Protocol (ICMP) is a TCP/IP protocol designed to help manage and control the operation of a TCP/IP network. The ICMP protocol provides a wide variety of information about a network's status and is considered part of TCP/IP's network layer. ICMP can provide useful information for troubleshooting TCP/IP.
ICMP uses messages to accomplish its tasks. Many of these messages are used in even the smallest IP network. Table 6.1 lists some of the ICMP messages.
Table 6.1: ICMP Messages
|Destination Unreachable||Informs the source host that there is a problem delivering a packet.|
|Time Exceeded||Indicates that the time that it takes a packet to be delivered has expired and that the packet has been discarded.|
|Redirect||Indicates that the packet has been redirected to another router that has a better route to the destination address. The message informs the sender to use the better route.|
|Echo||Used by the