Definition
Multicast is a network communication method where a single data stream is sent from a source to multiple specific destinations simultaneously. Instead of sending individual copies to each recipient, a multicast router replicates the stream only when necessary, efficiently delivering it to all interested parties. This technique is crucial for reducing network congestion and conserving bandwidth, especially in scenarios involving many recipients. A common application is live video streaming or online gaming, where numerous users receive the same content in real time. It differs from broadcast, which sends data to all devices on a network segment, and unicast, which sends data to a single device. Understanding multicast is essential for network engineers and security professionals and appears on exams like Network+ and CCNA.