Nodes in a tree are linked to a central hub that controls the traffic to the network. However, not every device plugs directly into the central hub. A majority of the devices connect to a secondary hub that in turn is connected to the central hub. Often a network combines several topologies as subnetworks together in a larger topology. Since multiple computers share a single transmission medium, all other computers must wait when one transmits to another.
All computers wait till the bus is free and then transmit.
After a collision recovers, the net requires that each computer to have a max delay of d. The network picks the one with the smallest delay to transmit again. A Bus Network Bus network developed for Apple Macintosh computers. Localtalk only sends 230.4 Kbps, has distance limitations, and is not available on all computers. A Ring Network Most ring networks use access mechanism called token passing .