In a Bus Topology, all of the devices, or nodes, are connected to a central cable, which is called a bus. Each node is connected one right after another along the same backbone. Information is sent across the bus until it arrives at its destination. All of the nodes receive the information. At both ends of the bus network is a terminator which absorbs the signal to prevent it from being bounced back. Each workstation has its own individual signal that identifies it and allows for the requested data to be returned to the correct originator. Only one computer on the network could talk at one time, so in order to prevent collisions, a method called CSMA/CD is used. Each node only listens; it is not responsible for moving the signal along.
The advantages of a Bus topology are that it is easy to connect a peripheral to the bus. It also requires fewer cables than the star topology. The Bus topology is the cheapest topology because of the main cable. It is easy to set up as well. Some disadvantages of the bus topology are if the main cable is severed, then the entire network goes down. It is also hard to quickly identify the location of the problem because there is no central server. During heavy traffic, the network could slow down. .
In the IBM Token Ring topology, each node is connected in a circular cable. Empty tokens are continuously traveling around the cable. To prevent collisions, a workstation can only send a message when it there is an open token. Whenever a workstation wants to send a message, it puts it into an open token and closes it. The token travels along the cable, and each workstation checks to see if the token destination belongs to that workstation. If it doesn't, then the message is sent again along the cable. If it is, then it copies the data and then opens the token and it circulates again until it is to be used.
An advantage of the Token Ring topology is that it uses a star-wired topology, which makes moving, changing, and adding equipment quick and easy.
