ITPEC FE Subject A April 2025 Question 24
In the OSI model, which of the following is the layer that is responsible for routing datagrams between hosts utilizing IP addresses across one or more networks?
Explanation
Network layer — routing datagrams between networks by IP address is the job of OSI layer 3.
The network layer provides logical addressing (IP addresses) and chooses a path for each datagram across one or more interconnected networks. Routers are the devices that work at this layer, and IP is its main protocol.
Answer (b)
Why not others:
- •(a) Data link — layer 2 delivers frames between neighbouring nodes on one link using MAC addresses; it does not route across networks
- •(c) Physical — layer 1 only transmits bits as signals over the medium and has no notion of addresses
- •(d) Transport — layer 4 gives end-to-end delivery between processes using port numbers (TCP, UDP) and relies on the network layer to do the routing
Key rule: Match the address to the layer: MAC addresses at the data link layer, IP addresses at the network layer, port numbers at the transport layer.
Networks · AI-written, may contain errors
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