ICMP Message Dropped by Router

B.

Traceroute is a network diagnostic tool used to track the path of an IP packet from its source to its destination. It works by sending a sequence of packets with incrementally increasing time-to-live (TTL) values, and then waiting for the ICMP error message returned by each router along the path to the destination.

Among the ICMP messages that can be returned by a router during traceroute, the one that indicates the packet is dropped by a router in the path is the "Time Exceeded" message, which has a Type value of 11 and a Code value of 0 or 1, depending on the implementation.

Type 11 is used for "Time Exceeded" messages, while Code 0 is used for packets that have reached their TTL limit and Code 1 is used for packets that are dropped due to a fragmentation issue. Therefore, the correct answer to this question is option B, "Type 11, Code 0".

Option A, "Type 3, Code 3", is incorrect because it corresponds to the "Destination Unreachable" message, which is returned by a router when it cannot forward a packet to its final destination.

Option C, "Type 5, Code 1", is incorrect because it corresponds to the "Redirect" message, which is returned by a router when it has a better next-hop address for the destination than the one in the original packet.

Option D, "Type 3, Code 1", is incorrect because it corresponds to the "Destination Unreachable" message with the specific code of "Port Unreachable", which is returned by a router when it cannot deliver a packet to a specific destination port on the destination host.

Option E, "Type 11, Code 1", is incorrect because it corresponds to the "Time Exceeded" message with the specific code of "Fragment Reassembly Time Exceeded", which is returned by a router when it cannot reassemble a fragmented packet before its maximum TTL is reached.