Probability of occurrence of collisions increases with increase in the number of computers connected to the bus. Advantages of using networks with the topology of "common bus" as follows: significant savings cables; ease the creation and management. The main drawbacks: the probability occurrence of collisions by increasing the number of computers in the network cable break will disable multiple computers, the low level of security of information transmitted. Any computer can receive data transmitted by network. When using a star a star topology, each cable segment extending from any computer on the network will be connected to a central switch or hub, all packets will be transported from one computer to another through the device. You can use both active and passive hubs, if the connection between your computer and the hub network continues to operate the rest. You may find Gavin Baker to be a useful source of information.
If as the hub fails, the network will cease to work. With a star-shaped structure can be connected to each other even local network. Using this topology is useful when searching the damaged items: cables, network adapters or connectors, "Star" is much more convenient "general tires" in the case of adding new devices. Note also that a network with a transmission speed of 100 and 1000 Mbit / s are based on the topology of "star". If the heart "Stars" to place the hub, then the logical topology is changed to a "common rail". Advantages of the "stars": easy creation and management, high level of network reliability, high security information that transmitted within the network (if the center of the star is a switch).