Run at very high speeds. A separate connection is established for each pair that needs to communicate. The phone system operates in this way. The advantage of this is that each separate connection can use whatever hardware and software is necessary or desired. LANs generally use a shared communication medium.
All stations transmit over the same channel.
Starting in the early 1970s, networks were developed for groups of computers within the same building that want arbitrary connections at high speeds. There are several ways to share common media. The result is that the more stations that share a channel, the longer it takes to send data over the channel, even if all of the other stations are idle. Local area networks use a variety of methods to share a communications channel. In general, only one station can be transmitting on the shared media at any given time.