Unicast is a one-to-one transmission between a specific source and a specific destination IP (e.g., 10.1.3.7 to 10.13.4.2). Multicast enables efficient one-to-many or many-to-many communication where traffic is sent to a specific group of interested receivers (class D addresses), allowing multiple senders and recipients. IP Directed Broadcast targets all hosts on a specific remote subnet; the packet is routed as unicast until it reaches the destination router, which then broadcasts it locally. Broadcast (specifically limited broadcast, 255.255.255.255) is sent to all network interface cards (NICs) on the same local Layer 2 segment as the sender and is not forwarded by routers.

RFC 919, "Broadcasting Internet Datagrams," Section 6 (Gateways and Broadcasts), defining the distinction between local and directed broadcasts.

RFC 1112, "Host Extensions for IP Multicasting," Section 1, defining multicast as the delivery of datagrams to a "host group" (zero or more hosts).

Cisco Systems, "IP Addressing: IPv4 Addressing Configuration Guide," Configuring IP Directed Broadcasts, which defines directed broadcasts as packets sent to the broadcast address of a subnet to which the sender is not directly attached.

RFC 1812, "Requirements for IP Version 4 Routers," Section 4.2.2.11, discussing the requirements for forwarding directed broadcasts versus limited broadcasts.