Final answer:
Explicit Congestion Notification (ECN) is a feature of TCP used in IP networks to indicate congestion without dropping packets, by marking packets. It requires support from both senders, receivers, and the network devices between them.
Step-by-step explanation:
Explicit Congestion Notification (ECN) is utilized within network protocols such as TCP/IP to indicate network congestion without dropping packets. ECN is a feature of TCP that works by marking packets instead of dropping them when there is congestion, allowing end-hosts to react to impending congestion. When both the sending and receiving sides support ECN, they can effectively manage network congestion, improving overall network performance and reducing packet loss. ECN must be supported by both the sender's and the receiver's operating system and by the routers and switches in the network path. However, if any segment of the network does not support ECN, the protocol can fall back to normal behavior (dropping packets) to signal congestion.