Connectionless communication is also known as datagram communication. That is, the ISO adopted some of the IEEE's physical network standards as part of its OSI model, including IEEE 802.3 or Ethernet, IEEE 802.4 or token-passing bus, and IEEE 802.5 or Token Ring. Each physical layer standard defines the network's physical characteristics and how to get raw data from one place to another. They also define how multiple computers can simultaneously use the network without interfering with each other.
Data is simultaneously visible to all machines on the network and is nondirectional on the cable.
All machines receive every frame, but only those meant to receive the data will process the frame and pass it to the next layer of the stack. If the data collides with another data packet, both computers back off, or wait a random time, then try again to send the data until access is permitted. Thus, once there is a high level of traffic, the more users there are, the more crowded and slower the network will become. Ethernet has found wide acceptance in office automation networks. IEEE 802.4 defines a physical network that has a bus layout.