Which of the following is not a congestion policy at network layer?

Answer: Flow Control Policy is not a congestion policy at the network layer.

Why: Flow control operates at the transport layer (for example TCP) to match the sender's transmission rate to the receiver's ability to process data. It prevents receiver buffer overflow and is distinct from network-layer congestion control mechanisms.

Network-layer congestion policies (the other choices) are described briefly below:

• Packet Discard Policy: Routers drop packets when buffers are congested (examples: drop-tail, RED) to reduce load and avoid buffer overflow.

• Packet Lifetime Management Policy: Using TTL or expiration limits prevents packets from circulating indefinitely and reduces congestion caused by loops or stale traffic.

• Routing Algorithm: Adaptive or load-sensitive routing can divert traffic away from congested links, helping balance load across the network.

Conclusion: Flow control belongs to the transport layer, so it is not a network-layer congestion policy; packet discard, packet lifetime management, and routing algorithms are network-layer approaches to dealing with congestion.