In a layered communications model, peers can send messages to which peers?

• A. Peers in any layer
• B. Peers in the same layer only
• C. Peers in the layers above and below only
• D. Peers in the layers below only

Answer: (B)

In layered networks, each layer on a device communicates with the matching layer on other devices. That is, the peers that exchange messages across a network are the same layer on each device, not different layers or multiple layers at once. This preserves the defined interfaces and behaviors of each layer, so data handed down by a higher layer on one device is received by the corresponding layer on the other device and can be properly processed or forwarded from there.

Because of this, messages are exchanged between peers in the same layer, ensuring the protocol and services remain consistent across devices. Crossing to a different layer on the other device would break the layer-specific responsibilities and the established communication contract.

So, the correct idea is that peers communicate with peers in the same layer.