For which one of the following reasons does Internet Protocol (IP) use the…

Answer: Prevent packets from looping indefinitely

Explanation: The TTL field limits how many hops an IP datagram can traverse. Each router that forwards the packet decrements the TTL by one; if the TTL reaches zero, the router discards the packet. This prevents packets from circulating forever due to routing loops.

• How it works: The sender sets an initial TTL value. Each router decrements the TTL by 1 before forwarding. When TTL == 0 the packet is dropped, and an ICMP Time Exceeded message is typically sent to the sender.

• Why it is called time-to-live: Historically named that way, but in practice IP implementations treat TTL as a hop-count limit rather than a clock-based time limit.

Why the other choices are incorrect:

• Stating that TTL ensures packets reach the destination within that time is wrong because TTL does not guarantee delivery or measure elapsed time; it only limits hops.

• Saying TTL discards packets that arrive later than a certain time is incorrect because TTL is not a timer measuring arrival latency; it is decremented per-hop.

• Limiting queueing time at routers is unrelated to TTL; queueing is determined by router buffering and scheduling, not by the TTL field.