A communications network can provide many types of service.
Simplex: The most basic type of service is known as simplex. This service provides one-way communication. Examples of this type of service are TV distribution, and the transmission of burglar alarm messages remote nodes may simultaneously transmit, or whether one must wait for the other to finish before starting transmission.
Duplex: Most networks transfer data in two directions and are known as duplex communications links. Duplex links are classified as either full duplex or half duplex (also known as two way alternate), depending upon whether both local and
Half-duplex: A half-duplex network, is one with a full duplex physical layer, but that on allows the network to be used on one direction at any one time. Many shared media are used in half duplex.
Some networks are able to transmit a message to all nodes which are connected to the network (this is common in LANs). This is known as broadcast transmission. In addition to broadcast, some networks also allow simultaneous transmission to a specific group of users, this is known as multicast transmission. An example of multicast transmission is the use of the IP network protocol to support packet video allowing remote participation in conferences across the Internet.
Gorry Fairhurst - Date: 01/10/2020