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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Control Message Protocol (ICMP/ICMPv4 and ICMPv6)                 9  ICMP Message Types and Formats                      9  ICMP Version 4 (ICMPv4) Informational Message Types and Formats

ICMP Version 4 (ICMPv4) Informational Message Types and Formats 1 2 3 ICMPv4 Timestamp (Request) and Timestamp Reply Messages

Application of Echo and Echo Reply Messages

The most common way that you may use the Echo and Echo Reply messages is through the popular utility ping, which is used to test host reachability. While the basic test simply consists of sending an Echo and waiting for an Echo Reply, modern versions of ping are quite sophisticated. They allow the user to specify many parameters, including the number of Echo messages sent, how often they are sent, the size of message transmitted and more. They also provide a great deal of information about the connection, including the number of Echo Reply messages received, the time elapsed for the pair of messages to be exchanged and a lot more. See the topic describing ping for a full explanation of the utility.

ICMP Version 4 (ICMPv4) Informational Message Types and Formats 1 2 3 ICMPv4 Timestamp (Request) and Timestamp Reply Messages