The NIC has its own unique address, which it uses to identify itself on the network. These cards are installed into expansion slots, and are sometimes built right into the motherboard of the computer. Different types of NICs are designed to accept certain types of transmission medium or network cable, which in turn determines the amount of information and the speed at which the information can be sent. They are also designed for different purposes. One type of card can be used by a client workstation solely to connect that computer to a network, while network servers that are specifically designed to transfer large amounts of information use other cards. NICs are usually connected to hubs or switches allowing them to communicate with each other.
A hub is a device used to concentrate and organize network wiring. There are two basic types of hubs, active and passive. A passive hub is simply a device that allows wiring connections in an orderly way. It requires no power and does not do any processing. The active hub contains circuitry that can filter, amplify and control data going through it. Active hubs are based on extending the network beyond the physical limits put on it via the transmission medium. In most networks today a device called a switch is replacing hubs. .
A switch is similar to an active hub in that it can filter, control and amplify data going through it. The main difference is the ability to segment networks and control the data on those segments. This ability allows only intended data to pass from one segment to the other, thus keeping network traffic to a minimum and allowing needed data to flow at maximum speeds across the network. It regenerates and amplifies the data when the switch determines it must pass the data from on segment to another, which allows networks to expand beyond the range of the transmission medium. Switches can only extend the network within a building.
