Is the following description correct? ICMPIs a link layer protocol, ICMP The message is triggered by the physical layer, and then by IP Layer or higher layer protocol to respond.

Question

Options

• ATrue
• BFalse

• A
  18% (4)
• B
  82% (18)

Explanation

B is correct because the description contains two factual errors about ICMP's position in the network stack.

Error 1 - Wrong layer: ICMP (Internet Control Message Protocol) is a network layer (Layer 3) protocol, not a link layer (Layer 2) protocol. It is encapsulated directly inside IP datagrams and operates alongside IP.

Error 2 - Wrong trigger: ICMP messages are generated by the IP layer or higher-layer protocols when they detect network problems (unreachable hosts, TTL expiration, etc.) - not by the physical layer. The physical layer has no awareness of ICMP.

Why A is wrong: Both sub-claims in the statement are false, so "True" cannot be the answer.

Memory tip: Think of ICMP as IP's "error messenger" - it lives at the same layer as IP (Layer 3) and is invoked by IP or above, never from below. A useful mnemonic: ICMP = IP's Complaints, Managed by Peers (network-layer peers, not physical signals).

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