The b-node mode uses broadcasts for name registration and resolution. For example, if CLIENT_PC1 wants to communicate with CLIENT_PC2, it will broadcast to all machines that it is looking for CLIENT_PC2 and then will wait a specified time for CLIENT_PC2 to respond.
The b-node mode has two major problems:
In a large environment, it loads the network with broadcasts.
Typically, routers do not forward broadcasts, so computers that are on opposite sides of a router will never hear the requests.