IP Addressing Fundamentals

IPv4 Multicasting Mechanisms

Figure 9-3 should have raised a question in your mind. Although it demonstrated how a single flow of communications from one device conserves bandwidth by being forwarded to multiple destinations simultaneously, you should be asking how that can happen. After all, each IP packet has room for only one source address and one destination address. So how can you forward a packet with just one destination address to a limitless number of destinations, each with its own IP address? The answer is remarkably simple: Use a fictitious address that correlates to a list of real IP addresses. Such fictitious addresses are known as multicast addresses. The fictitious nature of such addresses sometimes results in their being called ...