ICMP (Internet Control Message Protocol) - Computer Science Engineering (CSE) MCQ

The sender side adds the bits of the fragmented packet to find a sum. Checksum is the compliment of the sum (exchange 0’s and 1’s). The receiver then has to verify the checksum by adding the bits of the received packet to ensure that the packet is error-free.

Ping program is used to find if a host is alive and responding. It is to be entered into a command line with the syntax “ping (IP address)” to be executed. Traceroute is a program used to find the shortest route to the destination IP.

This field will be decremented by 1 at every router, and will be zero by the time it reaches source. This error reporting message is type 11 and is used to prevent the router from travelling forever in case some unknown path anomaly occurs.

Firstly, it informs the source that the datagram has been discarded. Secondly, it warns the source that there is congestion in the network. It’s type 4 error reporting message after which the source is expected to reduce the flow of packets.

127.0.0.0 is a special address known as the loopback address which is used for testing purpose of a machine without actually communicating with a network. Thus no error reporting message will be generated for such special addresses.

ICMP notifies the source about the error when an error is detected because the datagram knows information about source and destination IP address. The source can then retransmit the data again or try to correct those errors.

IP by itself does not provide the features of error reporting or error correction. So, to address these issues a network layer protocol called Internet Control Message Protocol is used. ICMP operates over the IP packet to provide error reporting functionality.

Tracert is used in case of windows, whereas Traceroute in UNIX. Tracert is a program used to find the shortest route to the destination IP. The Router sends destination unreachable message if a path to the destination IP is not found.

The round-trip time refers to the total time taken combining the time taken for a packet sent from a source to reach a destination and the time taken the acknowledgement sent by the destination to reach the source. The Router sends destination unreachable message if the destination is not found.

Router sends destination unreachable message if the destination is not found. Destination unreachable is type 3 error reporting message. It is invoked when the router can’t find a path to the intended destination to forward the packet through.