Error Handling
An IP datagram travels from one router to another until it reaches the target host. Consider the example of a scenario where a datagram is sent to a target host that does not exist on the destination network. In this case, when the final router finds that the datagram cannot be delivered, it has to notify the sending computer. In a connectionless transmission system, Internet Control Message Protocol (ICMP) is used for communicating the control and error messages of TCP/IP. These messages are encapsulated within an IP datagram before being sent. ICMP messages are used to instruct the sending computer of any problems in the transmission. Two instances where ICMP messages are generated are as follows:
Flow control— Used to ...
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