There are several classes of IP broadcasting:
However, it might still be useful to distinguish at higher levels between broadcasts and non-broadcasts, especially in gateways. This is the most useful case of broadcast; it allows a host to discover gateways without wired-in tables, it is the basis for address resolution protocols, and it is also useful for accessing such utilities as name servers, time servers, etc., without requiring wired-in addresses.
For reasons of performance or security, a gateway may choose not to forward broadcasts; especially, it may be a good idea to ban broadcasts into or out of an autonomous group of networks.