Broadcast in the sense of television? See Streamcasting.
A broadcast reaches every node on a network, but, to keep it closer to radio/TV meaning of the word, it should be a single transmission that happens to be heard by every recipient, not a swarm of single transmissions to each recipient, something we call broad unicasting.
A broadcast is a very effective operation, too bad it is technically feasible only under certain circumstances:
- In unswitched LANs, where every node hears every other node without needing directed copies of a message. This type of usage is mostly obsolete.
- In radio networks where the broadcast message can be sent over an antenna and many receiving stations can listen to it.
- Mobile telephony protocols like GPRS/UMTS etc. can provide acceptable broadcasting options.
- Same goes for satellite transmissions, but satellites aren't popular because they raise network latencies to often unacceptable levels.
So, in most cases broadcast as a concept is dead, and when it is not dead, multicast is usually a smarter strategy even under that circumstance.
Technology and the word broadcast
PSYC doesn't use the word broadcast, as there are zero operations in the protocol that require all nodes in PSYCspace to be informed of something. But you can make a multicast which contains all of your nodes, if you wish to.
On IRC the word broadcast is used for a message that needs to reach all servers. Technically however the message is distributed using IRC's single tree network, so every broadcast still qualifies as a multicast. IRC does plenty of this kind of broadcasts. Too many in fact, making it its scalability problem.
The Jabber community chose to use the word broadcast in a completely confusing way. What sounds like an efficient operation is actually the biggest scalability killer of all, because a broadcast in XMPP sense is what we call a broad unicast, sending a copy of a message to each recipient one by one. Too bad every presence announcement, every multi user chat, every publish-subscribe operation is such a kind of broadcast. No surprise XMPP has a much bigger scalability problem than IRC.