A non-broadcast multiple access network (NBMA) is a computer network to which multiple hosts are attached, but data is transmitted only directly from one computer to another single host over a virtual circuit or across a switched fabric.
Some NBMA network devices support multicast and broadcast traffic replication (pseudo-broadcasts).
The ITU-T G.hn standard provides a specification for creating a high-speed (up to 1 Gigabit/s) local area network using existing home power lines, phone lines and coaxial cables.
The reason being is that split horizon dictates that a router cannot send a routing table update out of the same interface from which it received it.
This family of protocols relies on link layer broadcasting for route advertisement propagation, so when this feature is absent, it has to be emulated with a series of unicast transmissions, which may result in a receiver node sending a route advertisement back to the node it has just received it from.