ICMP Message Type Code for Fragment Reassembly Time Exceeded

C.

The ICMP message type code that indicates a fragment reassembly time exceeded is Type 11, Code 1.

ICMP (Internet Control Message Protocol) is a protocol used by network devices to send error messages indicating issues that prevent proper communication between devices. Fragmentation is a process where large packets are divided into smaller fragments for efficient transmission across a network.

When a device receives a fragmented packet, it reassembles the fragments into the original packet. However, if the device is unable to reassemble the fragments within a certain time frame, it discards the packet and sends an ICMP message to the source device indicating the issue.

Type 11 ICMP message is known as the Time Exceeded message. It is sent by a router to a source device when a packet exceeds the time allowed to traverse the network. This message can have two different codes:

• Code 0: indicates that the TTL (Time-to-Live) value of the packet has reached 0, which means the packet has expired and discarded.
• Code 1: indicates that the fragment reassembly time has been exceeded, and the packet was discarded.

Therefore, option C, Type 11, Code 1 is the correct answer to the question. Option A, Type 4, Code 0, is incorrect because it indicates an ICMP message used for Redirect messages. Option B, Type 11, Code 0, is incorrect because it indicates a Time Exceeded message due to TTL expiration, not fragment reassembly time. Option D, Type 12, Code 2, is incorrect because Type 12 is not a valid ICMP message type.